Engine power supply system from a gas cylinder installation. Engine power supply system from a gas cylinder installation Disassembly and assembly of power supply devices for gas cylinder engines
Engine power supply system from a gas cylinder installation
The engines of gas-cylinder cars operate on gaseous fuel, the reserve of which is in cylinders installed on the cars.
The use of gas-cylinder vehicles makes it possible to use the significant resources of cheap combustible gases available in our country. The engine power and load capacity of gas-cylinder vehicles are the same as those of basic cars with carburetor engines. Therefore, the operation of gas-cylinder vehicles is technically and economically feasible.
Fuel for gas-cylinder vehicles. As fuel for their engines, they use mixtures of liquefied (more precisely, easily liquefied) gases obtained from associated petroleum and natural gases.
For gas-cylinder vehicles, the industry produces mixtures of technical propane and butane (SPBT) of two compositions:
SPBTZ - winter, containing at least 75% propane and no more than 20% butane;
SPBTL - summer, containing no less than 34% propane and no more than 60% butane.
In addition to propane and butane, the fuel also includes methane, ethane, ethylene, propylene, butylene, pentane and others, the total content of which in the mixture is 5...6%.
Propane fractions (propane and propylene) provide the necessary pressure in the car’s gas cylinder. The butane component (normal butane, isobutane, butylene, isobutylene) is the most high-calorie and easily liquefied component of liquefied gases.
The most important properties of liquefied gases, which determine their suitability for use as fuel for gas-cylinder vehicles, are: calorific value of propane - 45.7 (10972), butane - 45.2 (10845), gasoline - 43.8 (10500) MJ/kg (kcal/kg); the density of liquid propane is 0.509, and butane is 0.582 kg/m3; The octane number for propane is 120, for butane it is 93.
The gas must not contain mechanical impurities, water-soluble acids, alkalis, resins and other harmful impurities.
The saturated vapor pressure for a mixture of liquefied gases ranges from 0.27 MPa (2.7 kgf/cm2) at a temperature of -20 °C to 1.6 MPa (16 kgf/cm2) at a temperature of +45 °C.
Liquefied gases have a high coefficient of volumetric expansion. Therefore, cylinders should be filled with gas to no more than 90% of their volume. The remaining 10% is the volume of the vapor cushion, without which even a slight increase in gas temperature leads to a sharp increase in pressure in the cylinder (approximately 0.7 MPa, or 7 kgf/cm2 per GS of increasing the temperature of the liquefied gas).
Gas cylinder installation. The domestic automotive industry produces gas-cylinder trucks ZIL-138, GAZ-53-07 and buses LAZ-695P and LIAZ-677G. All these cars differ from the basic models ZIL-130, GAZ-53A, LAZ-695N and LIAZ-677 by the presence of a gas cylinder installation, as well as a modified gas engine that has a higher compression ratio than the base carburetor engine.
To ensure the ability to move the car in the event of a malfunction of the gas cylinder installation or lack of gas in the power system, there is a carburetor, on which the engine can develop power sufficient to move the car with a full load at a speed of 30...40 km/h, and a gasoline tank. It is not allowed to work on gasoline for a long time.
The diagram of the gas cylinder installation of the ZIL-138 car is shown in Fig. 32. It includes: a gas cylinder with fittings, a main valve, a gas evaporator, a gas filter, a reducer, a pressure gauge, a mixer, an air filter, and gas pipelines. For operation on gasoline there is a carburetor and a tank.
Rice. 32. Diagram of the gas cylinder installation of the ZIL-138 car:
1 - air filter; 2 - water supply tube to the evaporator; 3 - high pressure hose from the evaporator to the gas filter; 4 - gas evaporator; 5 - water supply hose from the evaporator to the compressor; 6 - gas pipeline of the idle system; 7 - high pressure hose from the main valve to the gas evaporator; 8 - gas supply pipe to the mixer; 9 - dosing-economizer device of the gearbox; 10 - gas reducer; 11 - gas pressure measuring transducer; 12 - gearbox filter; 13 - gas reducer pressure gauge; 14 - main valve; 15 - gasoline tank; 16 - filter; 17 - gas mixer; 18 - spacer for the mixer; 19 - vapor phase flow valve; 20 - control valve for maximum filling of the cylinder; 21 - measuring transducer for liquid level indicator in the cylinder; 22 - safety valve; 23 - filling valve; 24 - liquid phase flow valve; 25 - balloon; 26 - carburetor; 27 - hose connecting the vacuum spaces of the economizer and the gearbox unloading device with the engine inlet pipeline.
The main valve is designed to shut off the gas supply from the cylinder to the evaporator, gas reducer and mixer from the driver's seat.
The gas evaporator converts the liquid phase of the fuel into a gaseous phase. The gas passes through a channel in the aluminum mixer body, is heated by water circulating through the body cavity from the engine cooling system and evaporates.
A gas filter, equipped with a filter element consisting of a metal mesh and a package of felt plates, cleans the gas entering the gearbox from mechanical impurities - scale and rust. The filter is installed on the inlet fitting of the gearbox.
The reducer serves to reduce the pressure supplied to the gas mixer to close to atmospheric pressure. When the engine stops, the gearbox automatically stops the gas supply to the mixer.
The design and operation of the gearbox are shown in Fig. 33.
The cylindrical gearbox housing houses chamber A of the first stage, chamber B of the second stage and annular chamber B of the vacuum unloader.
One of the walls of the first stage chamber is formed by a rubber diaphragm, the edges of which are sandwiched between the gearbox housing and the cover. From the side of the cover, a compressed spring constantly presses on the diaphragm, tending to bend the diaphragm inside the gearbox housing (up). The central part of the diaphragm is connected by a crank lever to the valve, so that when the diaphragm bends inward, the lever opens the valve, and when it bends outward, it closes it.
In the second stage chamber there is a diaphragm sandwiched around the circumference between the upper part of the housing and the cover. Its central part is connected by a lever to the second stage valve. Bending the diaphragm downward causes the valve of the second stage to open, and bending it upward causes the valve to close. The spring acting on the diaphragm rod tends to bend the diaphragm upward.
The cavities under the diaphragm covers of the chambers of the first and second stages are connected to the atmosphere, and therefore, atmospheric pressure constantly acts on both diaphragms from the outside.
In chamber B of the unloader there is an annular diaphragm, which is acted upon by a spring that bends the diaphragm upward.
The housing of the dosing-economizer device is attached to the bottom of the gearbox housing, in which the main dosing device of the gearbox and an economizer with a pneumatic drive are located.
The dosing device includes dosing holes of constant and variable cross-section, a valve-regulator for economic adjustment of the gas mixture and an adjusting screw for power adjustment. The valve with spring and diaphragm with spring are parts of the economizer.
The housing of the dosing-economizer device has a gas outlet pipe; The fittings on the housing cover serve to connect chamber B of the unloader with the cavity under the economizer diaphragm and with the engine inlet pipeline.
The gearbox is mounted under the engine hood to the front wall of the cabin on a special bracket. Gas is supplied to the reducer through a gas filter mounted on a fitting. A pressure gauge tube is connected to the fitting, allowing you to control the pressure in the first stage chamber. The pipe is connected by a gas pipeline low pressure with a mixer, and the fitting using a rubber tube with the engine inlet pipe.
Rice. 33. Gas reducer:
a -- device; b - action diagram; A - first stage chamber; B - second stage chamber; B - vacuum unloader chamber; 1 - gas supply fitting; 2 - fitting for connecting a pressure gauge; 3 - first stage valve; 4 and 5 - diaphragm cover and first stage camera diaphragm; 6 - first stage diaphragm spring; 7 - adjusting nut; 8 - first stage valve drive lever; 9 - second stage valve; 10 - valve-regulator; 11 - economizer valve; 12 - valve spring; 13 and 18 - fittings; 14 - housing cover
When the main valve is opened, gas from the cylinder begins to flow through the evaporator, filter, gas filter of the reducer (Fig. 33), inlet fitting and open valve into chamber A of the first stage of the reducer. As gas enters, the pressure in the chamber increases, and when it reaches the required value (excess or gauge pressure should be 0.17...0.18 MPa or 1.7...1.8 kgf/cm2), diaphragm 5 bends down and lever the drive closes the valve, stopping gas access to the reducer. If the pressure in the first stage chamber drops, the spring bends the diaphragm upward, the valve opens and gas begins to flow into the chamber again. Thus, a constant pressure is automatically established in the first stage chamber, the value of which depends on the tension force of the spring.
The safety valve prevents damage to the diaphragm of the first stage of the gearbox, which can occur due to a failure to close the valve. If the valve of the first stage chamber does not close tightly, gas from the cylinder constantly enters this chamber and the pressure in it may exceed the permissible value. The safety valve spring is adjusted to a pressure of 0.45 MPa (4.5 kgf/cm2). At higher pressure, the safety valve opens and releases part of the gas from the first stage chamber to the outside.
While the engine is not running, the valve of the second stage chamber is closed and gas does not flow into it from the first stage chamber. When the engine starts, a vacuum is formed in the second stage chamber, connected by a gas pipeline to the mixer, and the diaphragm, bending inward, opens the valve through a lever drive. Gas from the first stage chamber will begin to flow into the second stage chamber, the pressure in which increases as gas enters it. When the pressure rises to close to atmospheric pressure, the valve will close and the flow of gas from the first stage chamber will stop.
The unloader operates as follows. When the engine is not running, the unloader spring pressure is transmitted through the stop to the diaphragm plate, increasing the closing force of the second stage valve.
When the engine is running at low idle speeds and at low loads (the mixer throttle is closed), a strong vacuum is created in chamber B of the unloader, connected by a tube to the engine inlet pipe, and the diaphragm bends down. The stop stops the pressure on the diaphragm of the second stage chamber, as a result of which only one spring acts on the second stage valve, allowing it to open even in the absence of vacuum in the second stage chamber.
Due to this, at low idle speeds and low loads, gas from the second stage chamber enters the mixer under an excess pressure of 100...200 Pa (10...20 mm water column). As the engine load increases, the gas pressure at the outlet of the gearbox and in the second stage chamber decreases, and a slight vacuum is created in it.
The dosing-economizer device regulates the amount of gas supplied to the mixer, and therefore maintains the required composition of the gas-air mixture.
At low and medium engine loads, when the mixer throttle is not fully open, a significant vacuum is maintained in the mixer throttle space. Since the cavity under the economizer diaphragm communicates with the throttle space, a vacuum is also formed in it, under the influence of which the diaphragm bends down and the economizer valve closes. In this mode, gas from the chamber of the second stage of the reducer passes to the outlet pipe through an opening of a constant cross-section and an opening, the cross-section of which can be changed by rotating the control valve; the position of the latter is selected with the expectation of achieving economical engine operation.
At high loads, when the mixer throttle opening approaches full, the vacuum in the throttle space and in the cavity under the economizer diaphragm decreases. Under the action of the spring, the diaphragm bends upward and opens the valve, after which an additional amount of gas begins to flow to the outlet pipe of the gearbox through a hole of constant cross-section and a hole of variable cross-section. The amount of additional incoming gas is regulated by rotating the screw, achieving maximum power from the engine.
Mixer and carburetor. The mixer is used to prepare a mixture of gas and air. The mixer is two-chamber, both chambers operate simultaneously and in parallel in all modes.
Rice. 34. Mixer:
1 - gas supply pipe; 2 - check valve; 3 - air damper; 4 - gas nozzle; 5 - diffuser; 6 and 10 - spray holes of the idle system; 7 - fitting for gas supply from the chamber of the second stage of the gearbox; 8 and 9 - adjusting screws for the idle speed system; 11 - throttle.
The gas enters the nozzle from the reducer through a pipe and a check valve. At the bottom of the mixing chamber there are spray holes for the idle system, the cross-section of which can be changed using adjusting screws.
The mixer is equipped with a centrifugal-vacuum engine crankshaft speed limiter, the same type as that installed on the ZIL-130 carburetor engine.
The mixer is connected to the engine intake manifold through a spacer to which the carburetor is attached. The mixer works as follows.
When starting, close the air damper briefly (Fig. 34) to increase the vacuum in the diffuser and cause an increased flow of gas through the nozzle.
At low idle speeds, gas flows from the gearbox through the fitting to the spray holes under the influence of strong vacuum formed in the area behind the closed throttle.
When the engine is running under load, gas enters the mixing chamber through the nozzle. The composition of the mixture is regulated by the dosing-economizer device of the gas reducer.
When the engine is running on gas, the choke, carburetor throttle and fuel (gasoline) valve must be closed.
If it is necessary to switch the engine to gasoline, it is necessary to close the main valve of the gas cylinder unit and exhaust all the gas from the devices located after this valve before stopping the engine. Then close both mixer flaps and start the engine on gasoline, like a regular carburetor engine.
To subsequently switch to gas, close the fuel (gasoline) valve and produce gasoline from the carburetor. After this, close the air damper and carburetor throttle and start the engine on gas, having previously opened the main valve. Running the engine on gasoline and gas at the same time is not allowed.
Start a cold engine on gas with the steam valves of the cylinder open and the liquid valves closed. When the engine warms up, open the liquid flow valves and close the steam flow valves.
At low temperatures ambient air, when starting a cold engine on gas is difficult, it is recommended to first start and warm up the engine on gasoline, and then switch it to gas, as stated above.
Gas pipelines and their connections. High-pressure gas pipelines (from the cylinder to the reducer) are made of steel or copper tubes with a wall thickness of about 1 mm and an outer diameter of 10... 12 mm. Gas pipelines are connected to the devices of the gas cylinder installation using nipple connections.
Low-pressure gas pipelines (from the reducer to the mixer) are made of thin-walled steel pipes and gas-resistant rubber hoses of large cross-section. They are connected with clamps.
The main malfunctions of a gas cylinder installation: gas leakage through loose connections; loose closure of valves and valves; gas filter clogged; violation of gearbox adjustment, causing excessive enrichment or depletion of the gas-air mixture; violation of the adjustment of the mixer idle system.
Rules for safe work on gas-cylinder vehicles. When leaking, gas forms explosive mixtures with air. If liquefied gas comes into contact with skin, it evaporates rapidly and may cause thermal burns(freezing).
Inhalation of vaporized gas causes poisoning. Therefore, it is necessary to carefully monitor the tightness of all connections of the gas cylinder installation. A significant leak is detected by ear (by the hissing of gas); to detect a minor leak, the joints are moistened with soapy water. If there is a leak, do not park the car in a closed room.
No open fire should be used near the car.
If it is necessary to tighten the connections of the installation pipelines, first close the cylinder supply valves and exhaust the gas before stopping the engine.
TO Category: - Car maintenance
Engine power supply system from a gas cylinder installation
The engines of gas-cylinder cars operate on gaseous fuel, the reserve of which is in cylinders installed on the cars.
The use of gas-cylinder vehicles makes it possible to use the significant resources of cheap combustible gases available in our country. The engine power and load capacity of gas-cylinder vehicles are the same as those of basic cars with carburetor engines. Therefore, the operation of gas-cylinder vehicles is technically and economically feasible.
Fuel for gas-cylinder vehicles. As fuel for their engines, they use mixtures of liquefied (more precisely, easily liquefied) gases obtained from associated petroleum and natural gases.
For gas-cylinder vehicles, the industry produces mixtures of technical propane and butane (SPBT) of two compositions:
SPBTZ - winter, containing at least 75% propane and no more than 20% butane;
SPBTL - summer, containing no less than 34% propane and no more than 60% butane.
In addition to propane and butane, the fuel also includes methane, ethane, ethylene, propylene, butylene, pentane and others, the total content of which in the mixture is 5...6%.
Propane fractions (propane and propylene) provide the necessary pressure in the car’s gas cylinder. The butane component (normal butane, isobutane, butylene, isobutylene) is the most high-calorie and easily liquefied component of liquefied gases.
The most important properties of liquefied gases, which determine their suitability for use as fuel for gas-cylinder vehicles, are: calorific value of propane - 45.7 (10972), butane - 45.2 (10845), gasoline - 43.8 (10500) MJ/kg (kcal/kg); the density of liquid propane is 0.509, and butane is 0.582 kg/m3; The octane number for propane is 120, for butane it is 93.
The gas must not contain mechanical impurities, water-soluble acids, alkalis, resins and other harmful impurities.
The saturated vapor pressure for a mixture of liquefied gases ranges from 0.27 MPa (2.7 kgf/cm2) at a temperature of -20 °C to 1.6 MPa (16 kgf/cm2) at a temperature of +45 °C.
Liquefied gases have a high coefficient of volumetric expansion. Therefore, cylinders should be filled with gas to no more than 90% of their volume. The remaining 10% is the volume of the vapor cushion, without which even a slight increase in gas temperature leads to a sharp increase in pressure in the cylinder (approximately 0.7 MPa, or 7 kgf/cm2 per GS of increasing the temperature of the liquefied gas).
Gas cylinder installation. The domestic automotive industry produces gas-cylinder trucks ZIL-138, GAZ-53-07 and buses LAZ-695P and LIAZ-677G. All these cars differ from the basic models ZIL-130, GAZ-53A, LAZ-695N and LIAZ-677 by the presence of a gas cylinder installation, as well as a modified gas engine that has a higher compression ratio than the base carburetor engine.
To ensure the ability to move the car in the event of a malfunction of the gas cylinder installation or lack of gas in the power system, there is a carburetor, on which the engine can develop power sufficient to move the car with a full load at a speed of 30...40 km/h, and a gasoline tank. It is not allowed to work on gasoline for a long time.
The diagram of the gas cylinder installation of the ZIL-138 car is shown in Fig. 32. It includes: a gas cylinder with fittings, a main valve, a gas evaporator, a gas filter, a reducer, a pressure gauge, a mixer, an air filter, and gas pipelines. For operation on gasoline there is a carburetor and a tank.
Rice. 32. Diagram of the gas cylinder installation of the ZIL-138 car:
1 - air filter; 2 - water supply tube to the evaporator; 3 - high pressure hose from the evaporator to the gas filter; 4 - gas evaporator; 5 - water supply hose from the evaporator to the compressor; 6 - gas pipeline of the idle system; 7 - high pressure hose from the main valve to the gas evaporator; 8 - gas supply pipe to the mixer; 9 - dosing-economizer device of the gearbox; 10 - gas reducer; 11 - gas pressure measuring transducer; 12 - gearbox filter; 13 - gas reducer pressure gauge; 14 - main valve; 15 - gasoline tank; 16 - filter; 17 - gas mixer; 18 - spacer for the mixer; 19 - vapor phase flow valve; 20 - control valve for maximum filling of the cylinder; 21 - measuring transducer for liquid level indicator in the cylinder; 22 - safety valve; 23 - filling valve; 24 - liquid phase flow valve; 25 - balloon; 26 - carburetor; 27 - hose connecting the vacuum spaces of the economizer and the gearbox unloading device with the engine inlet pipeline.
The main valve is designed to shut off the gas supply from the cylinder to the evaporator, gas reducer and mixer from the driver's seat.
The gas evaporator converts the liquid phase of the fuel into a gaseous phase. The gas passes through a channel in the aluminum mixer body, is heated by water circulating through the body cavity from the engine cooling system and evaporates.
A gas filter, equipped with a filter element consisting of a metal mesh and a package of felt plates, cleans the gas entering the gearbox from mechanical impurities - scale and rust. The filter is installed on the inlet fitting of the gearbox.
The reducer serves to reduce the pressure supplied to the gas mixer to close to atmospheric pressure. When the engine stops, the gearbox automatically stops the gas supply to the mixer.
The cylindrical gearbox housing houses chamber A of the first stage, chamber B of the second stage and annular chamber B of the vacuum unloader.
One of the walls of the first stage chamber is formed by a rubber diaphragm, the edges of which are sandwiched between the gearbox housing and the cover. From the side of the cover, a compressed spring constantly presses on the diaphragm, tending to bend the diaphragm inside the gearbox housing (up). The central part of the diaphragm is connected by a crank lever to the valve, so that when the diaphragm bends inward, the lever opens the valve, and when it bends outward, it closes it.
In the second stage chamber there is a diaphragm sandwiched around the circumference between the upper part of the housing and the cover. Its central part is connected by a lever to the second stage valve. Bending the diaphragm downward causes the valve of the second stage to open, and bending it upward causes the valve to close. The spring acting on the diaphragm rod tends to bend the diaphragm upward.
The cavities under the diaphragm covers of the chambers of the first and second stages are connected to the atmosphere, and therefore, atmospheric pressure constantly acts on both diaphragms from the outside.
In chamber B of the unloader there is an annular diaphragm, which is acted upon by a spring that bends the diaphragm upward.
The housing of the dosing-economizer device is attached to the bottom of the gearbox housing, in which the main dosing device of the gearbox and an economizer with a pneumatic drive are located.
The dosing device includes dosing holes of constant and variable cross-section, a valve-regulator for economic adjustment of the gas mixture and an adjusting screw for power adjustment. The valve with spring and diaphragm with spring are parts of the economizer.
The housing of the dosing-economizer device has a gas outlet pipe; The fittings on the housing cover serve to connect chamber B of the unloader with the cavity under the economizer diaphragm and with the engine inlet pipeline.
The gearbox is mounted under the engine hood to the front wall of the cabin on a special bracket. Gas is supplied to the reducer through a gas filter mounted on a fitting. A pressure gauge tube is connected to the fitting, allowing you to control the pressure in the first stage chamber. The pipe is connected by a low-pressure gas pipeline to the mixer, and the fitting is connected by a rubber tube to the engine inlet pipe.
Rice. 33. Gas reducer:
a -- device; b - action diagram; A - first stage chamber; B - second stage chamber; B - vacuum unloader chamber; 1 - gas supply fitting; 2 - fitting for connecting a pressure gauge; 3 - first stage valve; 4 and 5 - diaphragm cover and first stage camera diaphragm; 6 - first stage diaphragm spring; 7 - adjusting nut; 8 - first stage valve drive lever; 9 - second stage valve; 10 - valve-regulator; 11 - economizer valve; 12 - valve spring; 13 and 18 - fittings; 14 - housing cover
When the main valve is opened, gas from the cylinder begins to flow through the evaporator, filter, gas filter of the reducer (Fig. 33), inlet fitting and open valve into chamber A of the first stage of the reducer. As gas enters, the pressure in the chamber increases, and when it reaches the required value (excess or gauge pressure should be 0.17...0.18 MPa or 1.7...1.8 kgf/cm2), diaphragm 5 bends down and lever the drive closes the valve, stopping gas access to the reducer. If the pressure in the first stage chamber drops, the spring bends the diaphragm upward, the valve opens and gas begins to flow into the chamber again. Thus, a constant pressure is automatically established in the first stage chamber, the value of which depends on the tension force of the spring.
The safety valve prevents damage to the diaphragm of the first stage of the gearbox, which can occur due to a failure to close the valve. If the valve of the first stage chamber does not close tightly, gas from the cylinder constantly enters this chamber and the pressure in it may exceed the permissible value. The safety valve spring is adjusted to a pressure of 0.45 MPa (4.5 kgf/cm2). At higher pressure, the safety valve opens and releases part of the gas from the first stage chamber to the outside.
While the engine is not running, the valve of the second stage chamber is closed and gas does not flow into it from the first stage chamber. When starting the engine, a vacuum is formed in the second stage chamber, connected by a gas pipeline to the mixer, and the diaphragm, bending inward, opens valve 9 through the lever drive. Gas from the first stage chamber will begin to flow into the second stage chamber, the pressure in which as gas enters it rises. When the pressure rises to close to atmospheric pressure, the valve will close and the flow of gas from the first stage chamber will stop.
The unloader operates as follows. When the engine is not running, the unloader spring pressure is transmitted through the stop to the diaphragm plate, increasing the closing force of the second stage valve.
When the engine is running at low idle speeds and at low loads (the mixer throttle is closed), a strong vacuum is created in chamber B of the unloader, connected by a tube to the engine inlet pipe, and the diaphragm bends down. The stop stops the pressure on the diaphragm of the second stage chamber, as a result of which only one spring acts on the second stage valve, allowing it to open even in the absence of vacuum in the second stage chamber.
Due to this, at low idle speeds and low loads, gas from the second stage chamber enters the mixer under an excess pressure of 100...200 Pa (10...20 mm water column). As the engine load increases, the gas pressure at the outlet of the gearbox and in the second stage chamber decreases, and a slight vacuum is created in it.
The dosing-economizer device regulates the amount of gas supplied to the mixer, and therefore maintains the required composition of the gas-air mixture.
At low and medium engine loads, when the mixer throttle is not fully open, a significant vacuum is maintained in the mixer throttle space. Since the cavity under the economizer diaphragm communicates with the throttle space, a vacuum is also formed in it, under the influence of which the diaphragm bends down and the economizer valve closes. In this mode, gas from the chamber of the second stage of the reducer passes to the outlet pipe through an opening of a constant cross-section and an opening, the cross-section of which can be changed by rotating the control valve; the position of the latter is selected with the expectation of achieving economical engine operation.
At high loads, when the mixer throttle opening approaches full, the vacuum in the throttle space and in the cavity under the economizer diaphragm decreases. Under the action of the spring, the diaphragm bends upward and opens the valve, after which an additional amount of gas begins to flow to the outlet pipe of the gearbox through a hole of constant cross-section and a hole of variable cross-section. The amount of additional incoming gas is regulated by rotating the screw, achieving maximum power from the engine.
Mixer and carburetor. The mixer is used to prepare a mixture of gas and air. The mixer is two-chamber, both chambers operate simultaneously and in parallel in all modes.
Rice. 34. Mixer:
1 - gas supply pipe; 2 - check valve; 3 - air damper; 4 - gas nozzle; 5 - diffuser; 6 and 10 - spray holes of the idle system; 7 - fitting for gas supply from the chamber of the second stage of the gearbox; 8 and 9 - adjusting screws for the idle speed system; 11 - throttle.
Gas enters the nozzle from the reducer through a pipe and a check valve. At the bottom of the mixing chamber there are spray holes for the idle system, the cross-section of which can be changed using adjusting screws.
The mixer is equipped with a centrifugal-vacuum engine crankshaft speed limiter, the same type as that installed on the ZIL-130 carburetor engine.
The mixer is connected to the engine intake manifold through a spacer to which the carburetor is attached. The mixer works as follows.
When starting, close the air damper briefly (Fig. 34) to increase the vacuum in the diffuser and cause an increased flow of gas through the nozzle.
At low idle speeds, gas flows from the gearbox through the fitting to the spray holes under the influence of strong vacuum formed in the area behind the closed throttle.
When the engine is running under load, gas enters the mixing chamber through the nozzle. The composition of the mixture is regulated by the dosing-economizer device of the gas reducer.
When the engine is running on gas, the choke, carburetor throttle and fuel (gasoline) valve must be closed.
If it is necessary to switch the engine to gasoline, it is necessary to close the main valve of the gas cylinder unit and exhaust all the gas from the devices located after this valve before stopping the engine. Then close both mixer flaps and start the engine on gasoline, like a regular carburetor engine.
To subsequently switch to gas, close the fuel (gasoline) valve and produce gasoline from the carburetor. After this, close the air damper and carburetor throttle and start the engine on gas, having previously opened the main valve. Running the engine on gasoline and gas at the same time is not allowed.
Start a cold engine on gas with the steam valves of the cylinder open and the liquid valves closed. When the engine warms up, open the liquid flow valves and close the steam flow valves.
At low ambient temperatures, when starting a cold engine on gas is difficult, it is recommended to first start and warm up the engine on gasoline, and then switch it to gas, as stated above.
Gas pipelines and their connections. High-pressure gas pipelines (from the cylinder to the reducer) are made of steel or copper tubes with a wall thickness of about 1 mm and an outer diameter of 10... 12 mm. Gas pipelines are connected to the devices of the gas cylinder installation using nipple connections.
Low-pressure gas pipelines (from the reducer to the mixer) are made of thin-walled steel pipes and gas-resistant rubber hoses of large cross-section. They are connected with clamps.
The main malfunctions of a gas cylinder installation: gas leakage through loose connections; loose closure of valves and valves; gas filter clogged; violation of gearbox adjustment, causing excessive enrichment or depletion of the gas-air mixture; violation of the adjustment of the mixer idle system.
Rules for safe work on gas-cylinder vehicles. When leaking, gas forms explosive mixtures with air. In case of contact with skin, liquefied gas evaporates rapidly and can cause thermal burns (freezing).
Inhalation of vaporized gas causes poisoning. Therefore, it is necessary to carefully monitor the tightness of all connections of the gas cylinder installation. A significant leak is detected by ear (by the hissing of gas); to detect a minor leak, the joints are moistened with soapy water. If there is a leak, do not park the car in a closed room.
No open fire should be used near the car.
If it is necessary to tighten the connections of the installation pipelines, first close the cylinder supply valves and exhaust the gas before stopping the engine.
TO Category: - Cars and tractors
Subject8. Gas vehicle power supply system
Simplified diagram of the power supply system of a gas-cylinder vehicle
1 – Fuel tank. Designed to store gasoline reserves in a car.
2 – Cylinder. Designed to store a supply of liquefied gas on a car
3 – Ventilation box with fittings block. Here are the filling and supply valves, as well as the gas level indicator
5 – Switch "Gasoline-Gas". The switch key has three positions: Petrol – Off – Gas
6 – LPG fuel line
7 – Low pressure gas hose
8 – Control hose
FG – Gas filter
FB – Gasoline filter
BN - Gasoline pump. Standard engine fuel pump
KLG – Electromagnetic gas valve. When supply voltage is applied from switch 5, the valve opens
KLB – Solenoid gasoline valve. When supply voltage is applied from switch 5, the valve opens
R – Gas reducer. In the reducer, the gas evaporates and changes from liquid to gaseous state. To evaporate the gas, the gearbox housing is heated with hot antifreeze from the engine. The reducer also reduces gas pressure from 12...15 kg/cm2 to atmospheric
D – Dispenser. Allows you to regulate the amount of gas entering the engine and thereby set either an economical driving mode or a dynamic one.
The principle of operation of the gas vehicle power system
The operation of a gasoline engine is no different from the operation of a conventional carburetor engine power system. Namely, the BN fuel pump sucks gasoline from tank 1, passes it through the fuel filter FB and delivers it to the KS carburetor through the open valve KLB. In the carburetor, gasoline is mixed with air to form a fuel-air combustible mixture. To switch the engine to gas, switch 5 is first switched to the “Off” position (in this position both valves are closed) and wait until the remaining gasoline in the carburetor float chamber is used up. Then move the switch to the "Gas" position. At the same time, the KLG gas valve opens and the engine starts running on gas.
Cylinder for liquefied gas, steel, welded. The pressure of liquefied gas in the cylinder depends on the ratio of propane and butane in the mixture, does not depend on the degree of filling of the cylinder and is in the range of 12...15 kg/cm 2 . A ventilation box with a fitting block is attached to the cylinder. The valve block contains filling and flow valves. The filling valve is opened while the cylinder is being filled with liquefied gas; at the end of filling, this valve is closed. The flow valve is closed when the car is parked for a long time; in other cases, this valve is open. Associated with the valve block is a float mechanism located inside the cylinder and connected to a dial indicator on the outside of the valve block. In addition, the float mechanism is connected to a limit valve, which closes the filling line when the cylinder is 90% full. A gas cushion of 10% is necessary to compensate for the thermal expansion of liquefied gas. Liquefied gas has a high coefficient of thermal expansion. In the absence of a gas phase in the cylinder, an increase in temperature by 1 degree leads to an increase in pressure by 7 kg/cm 2. This may cause the cylinder to collapse, so filling the cylinder 100% with liquefied gas is not permitted.
The filling device 4 is usually located outside the vehicle so that possible gas leaks from the device do not enter the vehicle interior or cabin. The filling device has a ball valve that allows gas to flow from the filling hose into the cylinder and does not allow it to flow in the opposite direction.
The selection of liquefied gas from the cylinder is carried out from its day, from the liquid phase. The liquefied gas enters the FG filter through the fuel line and then enters the evaporator reducer through the open KLG valve. The housing of the evaporator gearbox is heated with hot antifreeze from the engine cooling system. This is necessary for the evaporation of liquefied gas and its transition to a gaseous state. A two-stage diaphragm-type gas reducer reduces gas pressure to atmospheric pressure. Fuel line 6 is a copper tube, control hose 8 is made of oil-resistant rubber, gas hose 7 is made of oil-resistant rubber, with a large flow area.
When the engine is not running, there is no vacuum in the carburetor and atmospheric pressure is transmitted through the control hose 8 to the gearbox P, which leads to its closure. Gas does not come out of the reducer. When the engine is running, a vacuum is formed in the carburetor, which is transmitted through the control hose 8 to the gearbox and removes the blockage of gas supply to the engine. The vacuum in the carburetor mixing chamber causes the suction of gas from the low-pressure gas hose 7 through the dispenser D. In the carburetor-mixer KS, gas is mixed with air and forms a gas-air combustible mixture, which enters the engine cylinders. Dispenser D is a regular tap that can be used to increase or decrease the flow area of a low-pressure gas line. As the amount of gas in the mixture decreases, it becomes leaner, the vehicle's movement becomes more economical, but the vehicle's dynamics deteriorate. When you rotate the dispenser in the other direction, everything changes in the opposite direction.
Gas reducer Lovato (Lovato) – Italy
The Lovato small-sized gas reducer-evaporator is designed for use in passenger cars - it contains the following functional elements:
LPG evaporator,
Two-stage pressure reducer,
Unloading device
Device for forced gas supply to the mixer,
Idle speed regulator.
Lovato evaporator reducer: 1 – inlet channel for liquefied gas, 2 – first stage valve seat, 3 – second stage diaphragm, 4 – unloader diaphragm, 5 – unloader spring, 6 – electromagnet, 7 – permanent magnet, 8 – lever second stage valve, 9 – idle speed adjustment screw, 10 – second stage valve, 11 – channel, 12 – first stage diaphragm, 13 – first stage valve lever, 14 – spring, 15 – first stage valve, A – first stage chamber cavity , B – chamber cavity of the second stage, C – heat exchanger cavity, D – unloader cavity, E – unloader fitting.
The gearbox consists of a housing, two covers and valve mechanism parts. In cavity C, hot antifreeze from the engine cooling system continuously circulates (the inlet and outlet of antifreeze is not shown in the figure). As a result of this, the entire gearbox body warms up to the operating temperature of the engine and, therefore, the liquefied gas, entering through channel 1 into cavity A, evaporates and turns into a gaseous state. In this case, the gas acts on the diaphragm of the first stage 12 and, overcoming the resistance of the spring 14, moves it down and through the lever 13 closes the valve of the first stage 15. The equilibrium of the gas pressure force and the elastic force of the spring is achieved at a pressure of 0.05...0.07 MPa (0 .5...0.7 kg/cm 2).
From cavity A through channel 11, gas enters the valve of the first stage 10 and, passing through it, fills cavity B of the second stage. In this case, the gas acts on diaphragm 3 of the second stage, lifts it, and through lever 8 closes valve 10. Equilibrium occurs at a pressure in cavity B of 50...100 Pa (0.0005...0.001 kg/cm 2), that is, slightly above atmospheric .
When the engine is running, the vacuum from the mixer is transmitted through a hose to cavity B of the first stage and gas from it enters the mixer. In this case, the pressure in cavity B decreases, diaphragm 3 lowers, opens valve 10 of the second stage, and gas from cavity A enters cavity B, and from there into the mixer. As gas flows from cavity A, the pressure in it decreases, diaphragm 12 rises, opens the first stage valve 15 and gas from channel 1 enters cavity A.
Unloading device D is designed to forcefully close the second stage valve 10 when the engine is not running. This is necessary to ensure the fire safety of the car. Cavity D is connected to fitting E and then, through a hose, to the throttle chamber of the engine. When the engine is not running, there is atmospheric pressure in cavity D and spring 5, through lever 8, forcibly closes valve 10 of the second stage, as a result of which gas does not exit the gearbox. When the engine is running, the vacuum from the throttle space is transmitted through the hose through fitting E to cavity D. In this case, the diaphragm of the unloading device, overcoming the resistance of spring 5, lowers and does not interfere with the movement of lever 8, which is controlled by diaphragm 3 of the second stage.
The short arm of lever 8 is acted upon by a spring and an idle speed adjusting screw 9. Using this screw, the engine is adjusted to idle.
Electromagnet 6 is used to force the opening of valve 10 of the second stage. This may be required to enrich the mixture when starting the engine, or to bleed gas from the gearbox before servicing or repairing it. To turn on the electromagnet, the driver presses the control button in the cab. In this case, a voltage of 12V is supplied to the winding of the electromagnet 6. Its core is pulled into the winding and acts on the lever 8, opening the valve 10 of the second stage - the gas enters the mixer. The electromagnet core protrudes outward and, if necessary, the driver can press it directly from the engine compartment. Document
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Introduction
Nowadays, the car is the most common type vehicle. Quite recently, literally 10-20 years ago, the roads of large cities were wide and free, but now a motorist has to stand in traffic jams for several hours to get to his destination. However, the number of cars is growing every day, and manufacturers are constantly trying to introduce new technologies that turn the car we know into a smart gadget that can think and act independently in a given situation.
And if the first cars were not at all safe, and only wealthy people could own them, now there are various classes of cars aimed at different wallets and needs. Naturally, every person strives and wants to buy an expensive car that has a famous pedigree, high-quality body materials and rich interior equipment. Luxury cars not only have a solid appearance, but are also equipped with the most advanced technologies. But budget cars receive only the most necessary bells and whistles, but like all others, they fulfill their intended purpose - they deliver their owner from point “A” to point “B” and back.
A huge number of people have already appreciated all the benefits of traveling by car and therefore do not want to part with this convenience even for a moment. Therefore, today, car rentals are gaining great popularity. Of course, they appeared a long time ago, but mainly only wealthy people used this service. Now, renting a business class car is available to anyone.
The world does not stand still, and along with it, we ourselves do not stand still. Cars are turning into an integral part of our lives, absorbing all the necessary functions for comfortable driving over long distances, being able to carry large loads, being invisible in city traffic or flying against the wind, reaching incredible speeds. Family, sports, SUVs, trucks, city, hatchbacks, sedans, station wagons, pickups - whatever the car, it helps us and it is impossible to do without it in our time.
Car power supply system with gas equipment
Purpose of HBO
The power system of a gas-cylinder vehicle is used to store fuel reserves, purify fuel and air, prepare a combustible mixture, supply it to the engine cylinders and exhaust gases.
HBO classification
In the current technical literature, there is no unified methodology for classifying gas equipment of different generations; almost all gas equipment installers are guided by a conventional classification system for gas equipment. The conditional division of gas equipment into generations creates convenience in professional communication and helps installation specialists clearly determine the design features of a particular type of gas equipment.
First generation
Systems with vacuum control and a mechanical gas dispenser, which are installed on gasoline carburetor and simple injection cars. The first generation uses both vacuum and electronic gas reducers. Without lambda probe.
Description
These are traditional devices with a gas mixer. The fundamental difference between a vacuum reducer and an electronic one lies in the locking element of the unloading chamber: in a vacuum, this function is performed by a vacuum membrane to which vacuum is supplied from the intake manifold:
1. the engine is running - there is vacuum - the gearbox is open
2. the engine is turned off - there is no vacuum - the gearbox is closed
simple, inexpensive solution
Can also be used on simple injection engines without feedback
· does not comply with modern safety standards
· this can be said to be the “last century”, on which subsequent generations of gas equipment are based
Second generation
Mechanical systems supplemented by an electronic dosing device operating on the principle of feedback from an oxygen sensor.
Description
Installed on cars equipped with an injection engine, with a lambda probe and a converter and a catalytic converter for exhaust gases ("catalyst"). These are traditional devices with a gas mixer, additionally equipped with gas dispensers.
To maintain the correct composition of the gas-air mixture, Lambda controllers use a signal from the car’s standard Lambda probe, as well as a signal from the throttle position and engine speed sensor, to optimize the fuel-air mixture during transient engine operating conditions.
· additional equipment with gas dispensers
guarantees compliance with Euro 1 environmental requirements
· high probability of “claps”
Reduced service life of spark plugs and air filter
· the toxicity of exhaust gases from vehicles equipped with such systems is, as a rule, at the level of EURO-1 standards, which were in force in Europe until 1996, and only in some cases approaches EURO-2 standards
Third generation
80% similar to 2nd generation HBO. Design feature This installation is an electronic dosage of fuel supply.
Description
Individual gas is supplied to individual cylinders by a dosing device (gas injector), which has a single-level control of the gas portion, which is controlled by an electronic unit. Gas is supplied to the intake manifold using mechanical injectors, which open due to excess pressure in the gas supply line.
The installation of third-generation gas equipment on fuel-injected cars differs in that instead of a gas valve, an injector emulator is used to cut off the gasoline supply. When gas is supplied, this emulator simulates the operation of gasoline injectors so that the standard computer does not go into emergency mode. For the same reason, you need to install a lambda probe emulator.
Built-in electronic power supply provides the required gas-air supply
· work is carried out from signals from motor sensors (Lambda probe, RPM, TPS, MAP)
· special gas supply system - using parallel injection
· gas engine and ECU (electronic control unit)
· low reaction speed to changes in driving mode
low speed of reaction to mixture adjustments
· non-compliance with Euro-3 environmental requirements
Fourth generation
These are systems with distributed synchronized gas injection. This is the latest and greatest solution known today in Eastern Europe: separate gas supply control (gas injectors) for each cylinder, which are controlled by a more advanced electronic unit.
Description
The 4th generation gas installation differs from the previous ones in that it is an exact copy of a gasoline injector, namely: each cylinder has its own nozzle that supplies the calculated gas injection necessary for the operation of a given cylinder. And the operation of the injectors is controlled by the ECU. In this case, the ECU is directly involved in the operation of the engine on gas, working with many sensors necessary for the correct operation of the engine on gas.
This type of gas injection completely eliminates the possibility of “pops” and requires less attention to the spark plugs and air filter. Gas consumption is as close as possible to gasoline consumption, while maintaining the dynamics of the car.
· function of automatic switching from gasoline to gas, and vice versa (when the gas in the cylinder runs out)
· compatible with Euro 3 environmental requirements, as well as with OBDII, EOBD on-board diagnostic systems
· is an exact copy of a gasoline injector
· the possibility of “claps” is excluded
· errors during installation are practically impossible, since all connecting parts are unified.
Fifth generation
Designed for use in any fuel-injected vehicles and is compatible with environmental requirements Euro-3, Euro-4 as well as on-board diagnostic systems OBD II, OBD III and EOBD.
Description
Unlike the 4th generation system, in the 5th generation systems, gas enters the cylinders in the liquid phase. To do this, there is a “gas pump” in the cylinder, which circulates the liquid phase of gas from the cylinder through a gas injector ramp with a back pressure valve back into the cylinder. 5th generation systems use the computing power and fuel maps embedded in the vehicle’s standard controller, and make only the necessary adjustments to adapt gas-cylinder equipment to the gasoline fuel map. The 5th generation is characterized by the presence of separate electromagnetic gas injection nozzles into each cylinder, i.e. completely similar to the gasoline system. The phase and dosage of injection is determined by the standard gasoline controller of the vehicle. An important advantage of 3rd, 4th and 5th generation systems is the function of automatic switching from gas fuel to gasoline.
· gas enters the cylinders in the liquid phase
· separate electromagnetic gas injection nozzles into each cylinder
· no loss of power and no increased gas consumption
· possibility of starting the engine on gas at any negative temperatures
High sensitivity to dirty gas
low maintainability
· high complexity
Search LecturesThe power supply system for gas-cylinder engines when using liquefied gas consists of a cylinder 1 with liquefied gas (at a pressure of 1.6 MPa), an evaporator, a filter, a gas reducer, a mixer, and a valve. As a reserve, an additional system is used, consisting of a gas tank, filter, pump, carburetor, which has a main metering device and an idle device. In addition, as in any power system there is an air filter, intake manifold, exhaust manifold, exhaust pipe, muffler. Engine operation with simultaneous use both systems are prohibited.
The evaporator in a car, heated by the cooling system liquid, serves to convert liquefied gas into a gaseous state.
The gas reducer ensures a reduction in gas pressure to a value close to atmospheric. The mixer prepares a gas-air mixture, the composition of which varies depending on the operating mode of the engine, for which there are additional devices, like the carburetor of a carburetor engine.
Using instrumentation on the instrument panel, the level (quantity) of liquefied gas in the cylinder and the gas pressure in the gas reducer are monitored. The power supply system for gas-cylinder engines when using compressed natural gas has, instead of a cylinder, several high-pressure cylinders (20 MPa), high- and low-pressure gas reducers. There is no evaporator. To control the amount of gas, a pressure gauge is used, and there may be a warning lamp on the instrument panel, signaling an unacceptable drop in pressure in the car’s cylinders.
In addition to single-fuel power systems, dual-fuel systems are used with equivalent power systems on gas and liquid fuels, as well as gas-liquid systems in which part of the liquid fuel is used as a pilot dose to ignite the gas-air mixture (gas diesel engines).
Compressible and liquefied gases for car engines. The engines of gas-cylinder vehicles operate on various natural and industrial gases, which are stored in a compressed or liquefied state in cylinders.
Gases released from drilling gas and oil wells or obtained during oil processing at cracking plants are used as compressible gases. The basis of compressible gases is methane. The pressure of compressed gases in cylinders reaches 20 MPa and decreases as gas is consumed.
Liquefied gases - propane, butane, etc. - are produced at oil refining plants. In a charged cylinder, liquefied gas fills about 90% of its volume. In the rest of the cylinder, the gas is in a vapor state. The presence of a vapor cushion protects the cylinder from destruction when the temperature rises, since the pressure in it is determined by the pressure of the fuel saturated with steam for the conditions environment and for any amount of liquefied gas does not exceed 1.6 - 2.0 MPa.
Compressed and liquefied gases used for gas-cylinder vehicle engines have high detonation resistance. The combustion heat of the gas-air mixture makes it possible to obtain slightly less power when using serial carburetor engines than when operating them on a gasoline-air mixture. Increasing the compression ratio on these engines makes it possible to compensate for the loss of power. A significant advantage of gas-cylinder car engines is the reduction of exhaust gas toxicity, which largely determines the prospects of such cars.
To operate on compressed and liquefied gases, serial cars with gasoline engines are used. Some gasoline engines are specially designed to run only on gas. Changes in their design consist mainly of increasing the compression ratio. Other engines of gas-cylinder vehicles do not undergo significant design changes and can operate on both liquefied gas and gasoline. Changes to the chassis include the installation of gas cylinders. The mass of compressed gas cylinders is several times greater than the mass of a filled gas tank, which provides the same vehicle range. The weight of liquefied gas cylinders differs slightly from the weight of a gas tank.
Before being used in the engine, liquefied gases are converted in a special device - an evaporator - from the liquid phase into the gaseous phase. Compressed gases come from cylinders to the engine in a vapor state. In both cases, gases are supplied to the engine under pressure close to atmospheric pressure. To reduce gas pressure in gas engine power supply systems, reducers are used.
Fuel supply equipment for gas vehicles.
The diagram of the fuel supply equipment of the ZIL-138 engine running on liquefied gas is shown in the figure. From the cylinder 8, liquefied gas under pressure flows through the supply valve 9 and the main valve 7 into the evaporator 1. In the evaporator, heated by hot liquid from the cooling system, the liquefied gas passes into a gaseous state. Gas filtration occurs in filter 2.
To reduce the gas pressure, a two-stage gas reducer 6 is used, which is a membrane-lever pressure regulator, from which the gas flows through a low-pressure hose into the mixer 10. The gas mixer is used to prepare a gas-air mixture, the composition of which varies depending on the engine load. Starting and warming up a cold engine is carried out using the vapor phase of the fuel in the cylinder. To do this, open the valve, the intake pipe of which is led into top part balloon.
But two indicators 4 and 5 control the gas pressure in the first stage of the gearbox and the fuel level in the cylinder. The cylinder 8 is also equipped with a valve for filling with liquefied gas during refueling, a safety valve and other fittings.
As a backup system, the engines are powered with a gasoline-air mixture. For this purpose, there is a gas tank 12, a fuel pump 14 and a carburetor 11, consisting of a main metering system and an idle system. Operating the engine while using both systems at the same time is prohibited.
The gas mixer is two-chamber with a downward flow of the combustible mixture and parallel opening of two throttle valves. In housing 4 (Fig.), on the common rollers of both chambers, air 3 and throttle 12 dampers are mounted, diffuser b, into the narrow part of which nozzle 5 is installed. Gas supply pipe 13 is attached to the housing through a gasket, closed with lid 2. A check valve is installed in it. 1. In the other pipe 7, through which the mixture enters channels 10 and 11, there are screws 8 and 9 for adjusting engine idle speed. The gas reducer is connected by two pipelines through economizer device 3 (see figure), from which gas is supplied to pipes 13 and 7 (see figure).
When the engine is idling, the formation of a combustible mixture occurs in the cavities behind the throttle valves. As the throttle valves open and the load increases, gas begins to flow into injector 5 through check valve 1, which opens due to the pressure difference. Finally, at maximum loads and the throttle valves are opened close to full, through a special economizer valve of the gas reducer, an additional quantity enters pipe 13 gas, enriching the gas-air mixture to the power composition. This is how the composition of the combustible mixture prepared by the gas mixer changes depending on the engine load.
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8. Gas vehicle power supply system
Topic 8. Power system of a gas-cylinder vehicle
Simplified diagram of the power supply system of a gas-cylinder vehicle
1 – Fuel tank. Designed to store gasoline reserves in a car.
2 – Cylinder. Designed to store a supply of liquefied gas on a car
3 – Ventilation box with fittings block. Here are the filling and supply valves, as well as the gas level indicator
5 – Switch "Gasoline-Gas". The switch key has three positions: Petrol – Off – Gas
6 – LPG fuel line
7 – Low pressure gas hose
8 – Control hose
FG – Gas filter
FB – Gasoline filter
BN - Gasoline pump. Standard engine fuel pump
KLG – Electromagnetic gas valve. When supply voltage is applied from switch 5, the valve opens
KLB – Solenoid gasoline valve. When supply voltage is applied from switch 5, the valve opens
R – Gas reducer. In the reducer, the gas evaporates and changes from liquid to gaseous state. To evaporate the gas, the gearbox housing is heated with hot antifreeze from the engine. The reducer also reduces gas pressure from 12...15 kg/cm2 to atmospheric
D – Dispenser. Allows you to regulate the amount of gas entering the engine and thereby set either an economical driving mode or a dynamic one.
The principle of operation of the gas vehicle power system
The operation of a gasoline engine is no different from the operation of a conventional carburetor engine power system. Namely, the BN fuel pump sucks gasoline from tank 1, passes it through the fuel filter FB and delivers it to the KS carburetor through the open valve KLB. In the carburetor, gasoline is mixed with air to form a fuel-air combustible mixture. To switch the engine to gas, switch 5 is first switched to the “Off” position (in this position both valves are closed) and wait until the remaining gasoline in the carburetor float chamber is used up. Then move the switch to the "Gas" position. At the same time, the KLG gas valve opens and the engine starts running on gas.
Cylinder for liquefied gas, steel, welded. The pressure of liquefied gas in the cylinder depends on the ratio of propane and butane in the mixture, does not depend on the degree of filling of the cylinder and is in the range of 12...15 kg/cm2. A ventilation box with a fitting block is attached to the cylinder. The valve block contains filling and flow valves. The filling valve is opened while the cylinder is being filled with liquefied gas; at the end of filling, this valve is closed. The flow valve is closed when the car is parked for a long time; in other cases, this valve is open. Associated with the valve block is a float mechanism located inside the cylinder and connected to a dial indicator on the outside of the valve block. In addition, the float mechanism is connected to a limit valve, which closes the filling line when the cylinder is 90% full. A gas cushion of 10% is necessary to compensate for the thermal expansion of liquefied gas. Liquefied gas has a high coefficient of thermal expansion. In the absence of a gas phase in the cylinder, an increase in temperature by 1 degree leads to an increase in pressure by 7 kg/cm2. This may cause the cylinder to collapse, so filling the cylinder 100% with liquefied gas is not permitted.
The filling device 4 is usually located outside the vehicle so that possible gas leaks from the device do not enter the vehicle interior or cabin. The filling device has a ball valve that allows gas to flow from the filling hose into the cylinder and does not allow it to flow in the opposite direction.
The selection of liquefied gas from the cylinder is carried out from its day, from the liquid phase. The liquefied gas enters the FG filter through the fuel line and then enters the evaporator reducer through the open KLG valve. The housing of the evaporator gearbox is heated with hot antifreeze from the engine cooling system. This is necessary for the evaporation of liquefied gas and its transition to a gaseous state. A two-stage diaphragm-type gas reducer reduces gas pressure to atmospheric pressure. Fuel line 6 is a copper tube, control hose 8 is made of oil-resistant rubber, gas hose 7 is made of oil-resistant rubber, with a large flow area.
When the engine is not running, there is no vacuum in the carburetor and atmospheric pressure is transmitted through the control hose 8 to the gearbox P, which leads to its closure. Gas does not come out of the reducer. When the engine is running, a vacuum is formed in the carburetor, which is transmitted through the control hose 8 to the gearbox and removes the blockage of gas supply to the engine. The vacuum in the carburetor mixing chamber causes the suction of gas from the low-pressure gas hose 7 through the dispenser D. In the carburetor-mixer KS, gas is mixed with air and forms a gas-air combustible mixture, which enters the engine cylinders. Dispenser D is a regular tap that can be used to increase or decrease the flow area of a low-pressure gas line. As the amount of gas in the mixture decreases, it becomes leaner, the vehicle's movement becomes more economical, but the vehicle's dynamics deteriorate. When you rotate the dispenser in the other direction, everything changes in the opposite direction.
Gas reducer Lovato – Italy
The Lovato small-sized gas reducer-evaporator is designed for use in passenger cars - it contains the following functional elements:
LPG evaporator,
Two-stage pressure reducer,
Unloading device
Device for forced gas supply to the mixer,
Idle speed regulator.
Lovato evaporator reducer: 1 – inlet channel for liquefied gas, 2 – first stage valve seat, 3 – second stage diaphragm, 4 – unloader diaphragm, 5 – unloader spring, 6 – electromagnet, 7 – permanent magnet, 8 – lever second stage valve, 9 – idle speed adjustment screw, 10 – second stage valve, 11 – channel, 12 – first stage diaphragm, 13 – first stage valve lever, 14 – spring, 15 – first stage valve, A – first stage chamber cavity , B – chamber cavity of the second stage, C – heat exchanger cavity, D – unloader cavity, E – unloader fitting.
The gearbox consists of a housing, two covers and valve mechanism parts. In cavity C, hot antifreeze from the engine cooling system continuously circulates (the inlet and outlet of antifreeze is not shown in the figure). As a result of this, the entire gearbox body warms up to the operating temperature of the engine and, therefore, the liquefied gas, entering through channel 1 into cavity A, evaporates and turns into a gaseous state. In this case, the gas acts on the diaphragm of the first stage 12 and, overcoming the resistance of the spring 14, moves it down and through the lever 13 closes the valve of the first stage 15. The equilibrium of the gas pressure force and the elastic force of the spring is achieved at a pressure of 0.05...0.07 MPa (0 .5...0.7 kg/cm2).
From cavity A through channel 11, gas enters the valve of the first stage 10 and, passing through it, fills cavity B of the second stage. In this case, the gas acts on diaphragm 3 of the second stage, lifts it, and through lever 8 closes valve 10. Equilibrium occurs at a pressure in cavity B of 50...100 Pa (0.0005...0.001 kg/cm2), that is, slightly above atmospheric.
When the engine is running, the vacuum from the mixer is transmitted through a hose to cavity B of the first stage and gas from it enters the mixer. In this case, the pressure in cavity B decreases, diaphragm 3 lowers, opens valve 10 of the second stage, and gas from cavity A enters cavity B, and from there into the mixer. As gas flows from cavity A, the pressure in it decreases, diaphragm 12 rises, opens the first stage valve 15 and gas from channel 1 enters cavity A.
Unloading device D is designed to forcefully close the second stage valve 10 when the engine is not running. This is necessary to ensure the fire safety of the car. Cavity D is connected to fitting E and then, through a hose, to the throttle chamber of the engine. When the engine is not running, there is atmospheric pressure in cavity D and spring 5, through lever 8, forcibly closes valve 10 of the second stage, as a result of which gas does not exit the gearbox. When the engine is running, the vacuum from the throttle space is transmitted through the hose through fitting E to cavity D. In this case, the diaphragm of the unloading device, overcoming the resistance of spring 5, lowers and does not interfere with the movement of lever 8, which is controlled by diaphragm 3 of the second stage.
The short arm of lever 8 is acted upon by a spring and an idle speed adjusting screw 9. Using this screw, the engine is adjusted to idle.
Electromagnet 6 is used to force the opening of valve 10 of the second stage. This may be required to enrich the mixture when starting the engine, or to bleed gas from the gearbox before servicing or repairing it. To turn on the electromagnet, the driver presses the control button in the cab. In this case, a voltage of 12V is supplied to the winding of the electromagnet 6. Its core is pulled into the winding and acts on the lever 8, opening the valve 10 of the second stage - the gas enters the mixer. The electromagnet core protrudes outward and, if necessary, the driver can press it directly from the engine compartment.
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Components and devices of gas cylinder installations.
Components and devices of gas cylinder installations
Gas supply equipment
The gas supply equipment of a gas cylinder installation includes the following devices and components:
- gas evaporator;
- gas heater;
- gas mixer;
- gas filters;
- gas reducers;
- dosing-economizer device.
Gas evaporator
The gas evaporator is used to convert liquefied gas into the vapor phase (gaseous state). In Fig. Figure 1 shows an evaporator used in domestic gas cylinder installations in trucks. It consists of two parts cast from aluminum alloy. The heat source in this evaporator is liquid from the engine cooling system.
The liquefied gas passes through the evaporator heat exchanger and turns into a gaseous state. The evaporator ensures normal engine operation at a coolant temperature of at least 80 °C, therefore, to start and warm up the engine, they most often resort to working on traditional types of fuel (gasoline).
Gas heater
The gas heater is used to preheat compressed gas in order to prevent moisture condensation in gas pipelines and its freezing in winter.
On domestic trucks, a heater is installed (Fig. 2), which uses the heat of the exhaust gases.
The heater consists of a housing 2, which houses a heat exchange coil 5. The heater is connected to the exhaust system upstream of the muffler. Exhaust gases, passing through the heater body, wash the coil through which the compressed gas passes and heat it up. Then the exhaust gases, having passed the heater, are released into the environment, bypassing the muffler, through the welded outlet pipe 6.
The intensity of gas heating is regulated by the size of the hole in a special dosing washer.
Gas filters
Filters are used to purify gas from mechanical impurities. Filters can be felt with rings or mesh. They are installed in the line after the evaporator. The mesh filter is usually installed on the gas reducer, and the filter with felt rings is combined with the solenoid valve.
On vehicles running on compressed gas, one filter element is installed at the inlet of the high-pressure reducer, the other - on the low-pressure line in front of the two-stage reducer.
The filter consists of a housing 2 (Fig. 3), a glass 4, a felt filter element 3 and a coupling bolt 5.
Electromagnetic valve 1 is in the normally closed position and when it is connected to the vehicle's on-board electrical network (ignition is turned on), it opens and allows gas to flow into the supply gas line.
Gas reducers are used to reduce the pressure of liquefied or compressed gas to a pressure close to ambient (atmospheric) pressure.
For gas-cylinder liquefied gas installations, two-stage low-pressure reducers are used, and for compressed gas installations, a single-stage high-pressure reducer is additionally used.
Two-stage gas reducer
The two-stage gas reducer (Fig. 4) is designed for all domestic gas-cylinder trucks. Structurally, a dosing-economizer device is combined with it.
When the engine is not running, the solenoid valve is closed and gas does not flow into the inlet fitting 8 of the gearbox. In this case, the pressure in cavity D, which is connected to the environment, bends the membrane 11 down and through the lever 10 opens the valve 7 of the first stage of the gearbox. In cavity B there is also a pressure corresponding to the ambient pressure, so membrane 2, through spring 5 and rod 4, moves lever 1 upward and opens valve 12 of the second stage of the gearbox. The pressure in the entire reducer corresponds to the ambient pressure.
When the ignition is turned on and the main valve is open, gas through inlet I, valve 7 enters cavities G and B and acts on membranes 11 and 2. If the engine is not running and there is no gas consumption, then these membranes close valves 12 and 7.
When starting the engine, through output II, the vacuum is transferred to cavity G, opening valve 7. At low loads, this system maintains a pressure of 50...100 kPa in cavity B. As the throttle valves open, valve 13 of the economizer is activated. The vacuum is transmitted to the membrane from below, and the economizer spring bends the membrane upward, opening the valve and allowing an additional amount of gas to pass to outlet II.
Single stage high pressure reducer
A single-stage high-pressure gas reducer (Fig. 5) is used to reduce the pressure of compressed gas to 1.2 MPa. Gas from the cylinder enters cavity A of the gearbox through a fitting with a union nut 15 and a ceramic filter 14 to valve 12. The gearbox spring presses on the valve from above through the pusher 3 and the membrane.
When the gas pressure in cavity B is less than the set one, the gearbox spring lowers valve 12 through the pusher, passing gas into cavity B through the resulting gap. The gas then passes through an additional filter 11. When the set pressure in cavity B is reached, membrane 2 bends upward, overcoming the force of its spring, and valve 12, under the action of spring 13, rises and closes the gas passage.
The output pressure is regulated by a handle with a screw 4. The operation of the gearbox is controlled by a pressure gauge that receives a signal from the high pressure sensor 1 and the output pressure drop indicator 6 (emergency sensor).
Gas mixer
Gas mixers are designed to prepare a combustible mixture and regulate its supply to the engine cylinders in accordance with its operating modes. They are manufactured as a stand-alone device (in a purely gas version) or combined with a carburetor. In the latter case, the device is called a carburetor-mixer and differs from a conventional carburetor in the presence of a nozzle for introducing gas into it. At the same time, the ability of the engine to operate on gasoline is preserved without changing the dynamic and economic indicators. The gas injector is placed either in the spacer between the throttle body and the diffusers, or is inserted into the diffuser from above.
Mixers for the gas version have the simplest design; the connection diagram of the gas channels of the mixer and reducer is shown in Fig. 6. Mixers do not have accelerator pumps, since, unlike gasoline, the density of oil and natural gases differs little from the density of air. Consequently, when the throttle valves are opened sharply, the combustible mixture will not become leaner.
The main gas supply is carried out by the metering-economizer device 1 through channel 2, check valve 6 and gas injectors 7, which are located in the narrow section of the diffusers 8.
When the engine is running at minimum idle speed, check valve 6 is closed, the rectangular hole is in the low-pressure zone, and gas enters the throttle space through round hole 3. The amount of incoming gas is regulated by screw 11. In this case, air enters through the gaps between the throttle valves. dampers and walls of mixing chambers.
When the throttle valves 5 are opened, the rectangular holes 4 move into a high vacuum zone, gas begins to flow through them, the crankshaft speed and engine power increase. The total gas supply to the idle system is adjusted with screw 10.
As the engine crankshaft speed increases, the vacuum in the diffusers 8 increases and the check valve 6 opens, turning on the main gas supply.
Gas is supplied to the idle system through two channels: directly from the second stage of the gearbox through channel 12 and from the cavity behind the metering device through channel 2. This design ensures a smooth transition from idle to partial load mode and the absence of over-enrichment of the combustible mixture at low loads.
Gas equipment and fittings
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Gas engine power supply system. Trucks. Supply system
Gas engine power supply system
By switching your car to gas fuel, you can save more expensive and scarce gasoline. Gas fuel is more environmentally friendly; its combustion releases fewer toxic substances into the atmosphere. A significant disadvantage of gas fuel is its low volumetric calorific value.
For gas engines, liquefied (petroleum) gases are used, which are in cylinders under pressure up to 1.57 MPa, and compressed (natural) gases, which are under pressure up to 19.6 MPa. Gas fuel is stored in containers made of steel or aluminum alloys. Liquefied fuel has become more widely used in automobiles. In gas engines, as well as in engines running on liquid fuel, external or internal mixture formation can be carried out. Cars with carburetor engines are used to operate on compressed and liquefied gases, but some engines are specially adapted to operate only on gas fuel. The operating cycle of an engine running on gas fuel is the same as that of an engine running on gasoline, but the operation of the system components and assemblies is significantly different.
In engines with external mixture formation without supercharging, gas enters the mixing devices under pressure approximately close to atmospheric pressure, in this case gas leakage into the external environment and air penetration into the gas pipeline are prevented. If there is excess pressure, gas leaks, and if there is a vacuum in the gas pipeline, a flammable mixture of gas and air is formed, which can lead to an explosion. In engines with any supercharged mixture formation, gas is supplied to the gas valve under pressure slightly higher than the boost pressure; this also occurs in engines with internal mixture formation without supercharging. In stationary gas engines, to maintain constant pressure, a gas pressure regulator is installed in front of the mixing elements, which automatically maintains the required pressure for engine operation.
To reduce gas pressure in front of the mixing devices, a reducer is installed. This device also regulates gas pressure and differs from gas pressure regulators, only with a higher degree of gas pressure reduction. There are one, two and multi-stage reducers, depending on the number of elements in which the gas pressure is gradually reduced. The reducer also prevents gas from flowing to the mixer when the engine is not running.
Let's consider the design and principle of operation of a liquefied gas power system using the example of cars of the ZIL family.
Rice. Scheme of a gas cylinder installation using liquefied gas.
1 – carburetor, 2 – pipeline. 3 – gas supply pipeline from the reducer to the mixer, 4 – gas supply pipeline at idle, 5 – low pressure gauge, 6 – valve for draining sludge or water in the cold season, 7 and 8 – pipelines for supplying and discharging liquid from the cooling system , 9 – main valve (in the driver’s cabin), 10 – filling valve for liquid gas, 11 – gas level indicator in the cylinder, 12 and 13 – flow valves for liquid and vapor phases of gas, 14 – safety valve.
Liquefied gas from the cylinder, through flow valve 12, filter valve, evaporator and gas filter enters the reducer. The reducer regulates the pressure and supplies it to the mixer through pipelines. Air is supplied from above, through the gas mixer pipe, which, together with the gas entering the mixer, forms a gas-air mixture, which then enters the engine cylinders through the intake pipe. Low pressure reducer.
Rice. Scheme of operation of a two-stage gearbox.
A – with the main valve closed, b – during engine start-up and operation, 1 and 10 – membranes of the second and first stages, 2, 9 – springs of the second and first stages, 3 – conical spring, 4 – check valve, 5 – throttle valve , 6 and 8 – double-arm levers of the second and first stages, 7 and 11 – valves of the second and first stages, 12 – membrane of the unloading device, 13 – dispenser-economizer, 14 and 19 – gas pipelines, 15 – air filter, 16 – mixing chamber, 17 – inlet pipeline, 18 – vacuum pipeline, 20 – safety valve, I – first stage of the gearbox, II – second stage of the gearbox, A – atmospheric cavity, B – vacuum cavity, C – cavity of the economizer device.
Each stage of a two-stage membrane-lever gearbox has valves 7 and 11, a spring 3, two-arm levers 6 and 8, which pivotally connect the membrane to the valve.
The first stage valve is in the open position under the action of spring 9 and membrane 10, double-armed lever 8, the pressure in the cavity of the first stage I remains constant and equal to atmospheric pressure when the engine is not running and the flow valve is closed.
Valve II, the second stage, when the engine is not running, is in the closed position and is tightly pressed to the seat by conical and cylindrical springs through a double-armed lever 6.
If the solenoid valve is turned on and the flow valve is open, gas enters the cavity of the first stage of the reducer. Diaphragm 1 overcomes the force of spring 3, bends through lever 6, and closes valve 7. The gas pressure in the cavity of the first stage is regulated by changing the force of spring 2 within the nut 0.16….0.18 MPa. The pressure gauge, which controls the pressure level, is located in the driver's cabin.
When the throttle valves are half-open (Fig. b), when starting the engine and operating it at medium loads, a vacuum is created under the throttle valves, which is transferred to cavity B of the economizer. Under vacuum, the membranes of the vacuum unloading device bend down and compress the conical spring3, unloading valve 7 of the second stage. The valve from the first stage opens, overcomes the resistance of the cylindrical spring 2 of the membrane 1. Gas fills the cavity of the second stage and enters the mixer through pipeline 19.
When the throttle valves are fully opened, the vacuum in the mixing chamber 16 becomes sufficient to open the check valve 4 and additional gas begins to flow through the dispenser - ecomizer 13. With an increase in the gas supply through the air ducts 14 and 19, the gas-air mixture is enriched and the engine power increases.
The gas mixer is used to obtain a combustible mixture in gas-cylinder vehicles. A significant difference between such a car and a carburetor is that the fuel is supplied in the same aggregate state as air, hence the design of the gas mixer is much simpler than a carburetor. Such mixers can be either a separate design or made in conjunction with a carburetor.
The presence of a carburetor-mixer does not mean that such a car cannot run on gasoline.
The liquefied gas evaporator is designed to convert liquid fuel into a gaseous state. The evaporator is made of aluminum and consists of two parts. The internal cavities of the evaporator are heated by liquid from the engine cooling system, which heats the gas moving through the channels.
The electromagnetic valve-filter is used to purify the gas from mechanical impurities. The purified gas then flows through the evaporator into the reducer and then into the mixer.
The natural gas power system is a high pressure unit. The cylinders are connected in series by pipelines; such cylinders are filled at gas filling stations through a filling valve. The pressure of compressed gas in the cylinders and reducer is controlled using pressure gauges.
The disadvantages of vehicles running on gas cylinder fuel include the vehicle's reduced carrying capacity by the amount of cylinder weight, as well as its increased fire hazard. Share on the page
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Car fuel equipment repair
General structure of a gas cylinder installationBased on the type of gaseous fuel, gas cylinder units for internal combustion engines are divided into three types: for compressed natural gas, liquid methane and liquefied propane-butane gas. A gas-cylinder installation, regardless of the type of gas used, consists of cylinders for storing and transporting gas, an evaporating or heating device, a gas reducer, a dosing device, a mixer, a pipeline and control devices.
Instruments and apparatus used for any type of gas do not differ significantly in their operating principle. The exception is cylinders for storing and transporting gas. This is because compressed natural gas is stored at high pressure (up to 20 MPa) and requires thick-walled vessels. Liquid methane is contained at a boiling point (-161 ° C) in isothermal vessels, and liquefied propane-butane gas has a maximum operating pressure of 1.6 MPa and for its storage and transportation by car, cylinders with a wall thickness of 3.0 to 6 are used, 0 mm and capacity up to 300 l.
Of all gaseous fuels, liquefied propane-butane gas comes closest to gasoline in terms of energy concentration per unit volume, storage method and other performance properties. It is most widely used as a fuel for automobile engines.
Since 1975, serial production of gas-cylinder vehicles ZIL-138 and GAZ-53-07 began. These cars have gas engines. Their gas cylinder units are designed for an excess pressure of 1.6 MPa and provide storage of liquefied gas, its evaporation, purification, stepwise reduction and supply to the engine in strictly specified quantities mixed with air. In addition, the car has a backup system for powering the engine with gasoline (Fig. 94).
Liquefied gas in gas-cylinder vehicles is contained in a cylinder 20 in liquid and vapor state. In addition to control, safety and filling valves, the gas cylinder is equipped with two flow valves that allow the engine to be supplied with the vapor or liquid phase of gas.
The power supply system ensures normal operation of the engine provided that gas is supplied to the reducing device in a vapor state. Evaporation of liquefied gas in the power system occurs due to heat release from the engine cooling system.
When starting and warming up the engine, a slight temperature difference between the coolant (cooling system fluid) and the gas does not ensure its evaporation. In this case, the engine is powered by the vapor phase of gas through a valve.
Rice. 94. Diagram of the power supply system of a gas-cylinder car: 1 - spacer, 2 - sediment filter, 3 - fuel pump, 4 - carburetor, 5 - gas mixer, 6 - tube connecting the gearbox to the suction pipeline, 7,9 - hoses for supply and cooling system fluid discharge to the evaporator, 8 - evaporator, 10 tube for gas removal to the idle system, 11 - main gas supply hose, 12 - dosing-economizer device, 13 - gas reducer, 14 - gas filter, 15 - mesh filter, 16-pressure gauge of the first stage of the gearbox, 17 - level indicator of liquefied gas in the cylinder, 18 - main valve, 19 - fuel tank, 20 - liquefied gas cylinder, 21 - vapor phase flow valve, 22 - liquid phase flow valve
After the engine has warmed up, it is supplied with liquid gas through a valve. Feeding the engine with a liquid phase allows you to eliminate boiling of the liquid and a drop in pressure in the gas cylinder, as well as maintain the stability of gas parameters, since in the liquid phase all components are well mixed and the chemical composition of the fuel practically does not change as the cylinder is emptied.
From the cylinder, gas is supplied to the main valve, which serves to quickly stop the gas supply to the engine. The valve is controlled from the driver's cab. After the main valve, the liquefied gas enters the evaporator, in which hot liquid from the engine cooling system circulates through hoses. After passing through the evaporator coil, the liquefied gas completely changes from a liquid state to a vapor state and undergoes purification. For this purpose, the system is equipped with a filter with felt rings and a mesh filter.
The purified gas is supplied to the reducer, where a two-stage pressure reduction occurs to a value close to atmospheric pressure. The operation of the gearbox is controlled by vacuum from the suction pipeline, which is transmitted into it through tube 6. From the gearbox, through a dosing-economizer device and the main supply hose, gas is directed to the gas mixer.
In addition, gas is supplied through the tube, bypassing the dosing-economizer device, from the reducer to the mixer’s idle system. In the mixer, gas is mixed with air, forming a combustible mixture, which is sucked into the engine cylinders.
The gas cylinder installation of the car is equipped with two control devices: a remote electric pressure gauge indicating the gas pressure in the first stage of the reducer, and an indicator of the level of liquefied gas in the cylinder.
The backup system for powering the engine with gasoline consists of a fuel tank, filter filter, fuel pump and a single-chamber carburetor mounted on a spacer located under the gas mixer.
The presence of a backup power system on a car creates the possibility of running the engine on gasoline in the event of complete consumption of gas or a malfunction of the gas equipment. When switching from gaseous fuel to gasoline, or vice versa, the engine should not be allowed to operate on a mixture of the two fuels, as this leads to backfires, which are dangerous in terms of fire.
When switching engine power from one type of fuel to another, be sure to stop the engine. At the same time, the supply is shut off and one type of fuel is produced from the system, then the throttle control lever is attached to the carburetor (or, conversely, to the mixer), the supply of another type of fuel is opened and the engine is started in the usual way.
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Cars and tractors
General structure of the engine power supply system from gas cylinder unitsThe operation patterns of gas cylinder installations of different cars are fundamentally the same. A gas cylinder installation for compressed gas consists of cylinders, cylinder valves, a filling valve, a gas heater, a main valve, high-pressure gas pipelines, a gas reducer with a filter, pressure gauges, a carburetor-mixer and low-pressure gas pipelines. The power supply system devices for running on gasoline in gas-cylinder vehicles have been retained (fuel tank, sediment filter, fuel pump and fuel lines).
When the engine is running, the valves are open and gas flows under high pressure to the gearbox, having been pre-cleaned in a strainer. In the reducer, the gas pressure is reduced to approximately 0.1 MPa. The gas then goes through a rubber hose to the carburetor-mixer, which is used when operating on gas as a gas mixer, from which the gas-air mixture enters the engine cylinders. The high pressure gauge shows the gas pressure in the cylinders. Using a low pressure pressure gauge, the operation of the first stage of the gearbox is monitored. A preheater, in which the gas is heated by exhaust gases from the exhaust pipe, is necessary because when sharp decline pressure in the reducer, the gas is greatly cooled, which can lead to interruptions in operation and the formation of ice jams, especially in the cold season. The heating intensity can be adjusted using washers with holes of different diameters. The hose of the filling dispenser of the gas filling station is connected to the valve when filling cylinders with gas. Cylinder valves are used to shut off the main pipeline at the end of the working day. The main valve is located in the driver's cabin and is used to shut off the gas main in parking lots.
The gas-cylinder installation for liquefied gases (Fig. 67, b) differs from the described design of the cylinders, evaporator and the presence of minor changes in the design of the gearbox and carburetor a-mixture.
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Gas injection power system.
Engine power supply system from a gas cylinder installation
Gas injection system
The design of the gaseous fuel engine power supply system discussed in previous articles is a mechanical system with vacuum control and belongs to the first generation of gas-cylinder installations. IN Lately Gas cylinder installations are widely used. The first generation has been replaced by the second - mechanical systems with electronic control, which retain the same gas equipment installation diagram and chain: filling device - cylinder fittings - gas cylinder - main shut-off valve (instead of a valve) - reducer - gas mixing device - heating system.
However, the gas supply in second-generation systems is regulated by an electronic control unit (ECU), which ensures the stoichiometric composition of the mixture in all engine operating modes and, in addition, automatically closes the shut-off valves in the event of emergency damage to the gas line or when the engine stops.
The executive element for regulating the gas supply is an electric gas dispenser - a device operating on the principle of a stepper motor. Changing the position of its piston according to a signal from the ECU ensures the optimal composition of the gas-air mixture supplied to the engine cylinders.
Second-generation engine power systems can also be installed on vehicles equipped with gasoline injection systems. In this case, when switching to gas, the electric fuel pump is turned off (in systems with mechanical injectors). At the same time, they are replaced by emulators - devices that emulate the operation of injectors. The need to use emulators is due to the fact that the electronic engine control unit, not receiving information about the operation of the injectors, turns off the entire system, including the ignition system, assuming that damage has occurred in the electrical circuit.
The air flow sensor is protected with a “cracker” - a device that prevents damage to the sensor and air filter in the event of a possible backlash of gas from the intake pipe. Additionally, sensors are installed for the amount of gas entering the engine and a gas mixing device, which is installed on the throttle assembly.
In Fig. 1 shows a diagram of the installation of Landi Renzo gas equipment produced in Italy on a car.
The electronic control unit performs the same functions as the computer in a gasoline injection system, and, in addition, simulates the normal signal of an oxygen sensor designed to operate on gas. It also ensures that the engine starts only on gasoline, automatically turning off the gas supply, and also makes it possible, using switch 2, to switch to the desired type of fuel at any time without stopping the engine.
The third generation of gas-cylinder installations includes the gas injection system. One variant of this system is the IGS system, shown in Fig. 2. It features reduced gas consumption compared to systems of previous generations.
The dynamic characteristics of a car equipped with such a system, when running on gas, are as close as possible to the parameters of a car running on gasoline.
Electronic control unit 2 adjusts the gas supply to the engine cylinders based on the analysis of signals from oxygen sensors, throttle position, crankshaft speed and the absolute value of pressure in the intake manifold. Having received the necessary information, the ECU determines the opening position of the dosing unit and the position of the blocking valve located in it.
Dosing unit 3, according to ECU signals, opens by a certain amount, increasing or decreasing the amount of incoming gas. The blocking valve stops the gas supply when the car is braking by the engine.
Distributor 4 supplies gas to each engine cylinder through special nozzles installed in the intake manifold near the intake valves.
Reducer-evaporator 5 is equipped with a coolant temperature sensor, which determines the moment of switching the engine power supply from gasoline to gas. After starting the engine on gasoline, as soon as the programmed temperature is reached, the ECU switches the engine to gas power.
Gas flows from the cylinder into the evaporator reducer 5, which sets the gas pressure value depending on the vacuum value in the inlet pipeline. Next, the gas enters the metering unit 3, which, based on a signal from the electronic control unit 2, instantly determines and produces the amount of gas required for the engine, which then flows to the distributor 4. The distributor not only divides the gas flow among the cylinders, but also maintains the optimal pressure in the area at a constant level systems after the dosing unit.
As the load on the engine increases, the gearbox increases the gas pressure at the inlet to the dosing unit in order to guarantee the supply of the gas required in this mode, while the pressure at the outlet of the doser remains unchanged.
There is a constant search for new solutions to improve gas cylinder installations for compressed natural gas. A new gas-fuel system “SAGA-7” has been developed for ZIL vehicles, the peculiarity of which is lightweight, high-strength cylinders with a metal body covered with a layer of fiberglass.
Gas-fuel equipment has also been developed for storing and supplying liquefied natural gas to a heat exchanger, where the gas evaporates and is then supplied through a gearbox to the engine cylinders in the usual way.
A feature of the gas-fuel equipment of the Gazelle car is the presence of a vessel with high vacuum-solid-insulating properties (Fig. 3), which allows methane to be stored at a temperature of -150 ˚C in a liquid state, which significantly reduces its volume. The vessel is a kind of thermos - a double cylindrical tank made of stainless steel. The internal vessel is designed for excess pressure (0.5 MPa).
To maintain the required vacuum in the insulating space between the inner vessel and the outer casing and provide thermal insulation, the outer surface of the inner vessel is covered with a highly effective absorbent material (vacuum jacket), forming a layered thermal insulation. The vessel is secured in the casing by two cylindrical fiberglass support bushings.
A trap is installed in the upper cavity of the internal vessel to prevent the release of the liquid phase of gas into the drainage pipeline when the car is moving on an uneven road. At the bottom of the casing there is a vacuum valve, with which you can create and maintain a vacuum for a long time. The capacity of the gas vessel is 100 l. The vessel is filled with gas no more than 90%. The gas reserve in the container provides approximately the same vehicle mileage without refueling as with gasoline.
As mentioned in previous articles, diesel engines are now less widely used to run on gas fuel. The main reason - heat self-ignition of oil and natural gas compared to diesel fuel, therefore, to convert a diesel engine to run on gas, it is necessary to solve the problem of ignition of the combustible mixture. This problem can be solved in two ways - to inject gas together with a small “ignition” portion of diesel fuel, or to equip the diesel engine with an ignition system.
Features of operation of gas-cylinder vehicles
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