Modernization of the KAMAZ-740 diesel engine in order to transfer it to the gas diesel

Summary

1. The theme of the project: Modernization of the KAMAZ740 diesel engine in order to transfer it to the gas diesel.

2. The project was completed at the Department of Tractors and Cars.

3. Performer: Varzar Valery Vasilievich.

4. Head: Chernobrisov Associate Professor Sergey Feodosevich.

5. Annotation Text:

The total production of natural gas in 2010 in the world amounted to 3.275 trillion cubic meters. m, which corresponds to the thermal equivalent of all produced oil, including gas condensate. About 35% of oil is currently spent on the production of motor fuels, but even a deepening of its processing with an increase in the share of light products to 5060%, as well as a fuel economy regime in operation with the development and introduction of new energy-saving technologies, cannot in the near future exclude an increase in gas consumption in agriculture. Modern automobile diesel engines can be converted into spark-ignition gas engines or converted into gas diesel engines.

The relevance of the problem is that existing modern cars are converted from diesel fuel consumption to gas fuel, as cheaper and more promising fuel.

To this end, the diploma project involves one of the methods of converting a modern automobile engine from diesel fuel to gas diesel. Design changes and environmental effects make it possible to retrofit existing ones without unnecessary costs for the creation of special engines.

Introduction

The limited and non-renewable resources of oil, the increase in its export, the increase in the production of synthetic materials from petroleum products, as well as the expanded organization of road transport does not allow to orient energy support for the growth of agricultural products to increased consumption of motor fuels obtained from oil. An alternative solution to the problem is the creation of capacities for the production of synthetic fuel from gas, the reserves of which in the territory of the former USSR exceed the reserves of oil, and in the period before the introduction of the necessary capacities for the production of synthetic fuel, the direct use of natural and petroleum gas, as well as biogas, as fuels for tractors and self-propelled agricultural machines will be relevant.

Since imports of various goods, including fuel and lubricants, come to us from the nearest Union republics, it should be noted that the former USSR ranks first in the world in terms of natural gas reserves, the production of which, unlike oil and coal, is constantly growing.

So in 1987. gas production in conversion to conventional fuel reached 822.7 million tons, which practically corresponds to the thermal equivalent of all produced oil, including gas condensate. About 35% of oil is currently spent on the production of motor fuels, but even deepening its processing with an increase in the yield of light products to 5060%, as well as fuel savings in operation with the development and introduction of new energy-saving technologies cannot in the near future exclude an increase in gas profits in agriculture. It will be used primarily for heating production premises and greenhouses, in stationary installations, as well as for household needs of agriculture, however, it is possible that the shortage of motor fuels will be compensated by gas if a sufficient number of stations is built to compress or reduce it and a fleet of gas stations is created.

Modern automobile engines can be qualified as spark-ignition gas engines or converted into gas diesel engines.

The principle of engine operation according to the gas-diesel cycle was patented by R. Diuemmi in 1898. and became the basis for the creation of various structural forces for the operation of gas diesel engines. A number of changes are made to the design of the engine. A gas mixer, a gas supply control system, an interconnected control system for the high pressure fuel pump dispenser and gas supply, as well as a protection system will be added. In this method, the air duct is supplied not with air, but with a gas-air mixture, which is ignited with a dose of liquid fuel sprayed through the nozzles of the main fuel gas supply system. The maximum amount of ignited liquid fuel is determined by the energy required to ignite and fully create the gas-air mixture. Typically, the ignition dose does not exceed 1015% of the maximum supply when operating on pure diesel fuel.

The main advantages of gas diesel engines are:

keeping the power parameters at the level of the base engine;

possibility of some increase of maximum torque and its displacement into zone of low rotation speeds;

reduction of fluidity of exhaust gases by 2-4 times;

reduction of the engine noise level by 2-4 dB, especially in the process with volumetric mixing;

saving up to 80% of diesel fuel by replacing it with gas;

relative design simplicity of conversion of diesel to gas diesel;

conversion of engines already in service;

using natural and liquefied petroleum gas and biogas while maintaining energy values at a predetermined level as a result of varying the initial dose of liquid fuel;

Sufficiently large reserves of vehicle gas travel;

increased service life of engine oil, reduced demolition of cylinder-piston group;

efficient temporary use of gas diesel machines in regions where there are no gas filling stations;

fast transition from one fuel to another and back.

The main disadvantages of gas diesel engines:

some complication of the engine power supply system due to the appearance of additional elements (gas dispenser, mixer, gas reduction system, gas storage system, etc.);

increasing the resources of hydrocarbons and nitrogen oxide with exhaust gases in the gas-diesel process compared to the diesel cycle;

increase of labour intensity of maintenance of machines with gas diesel by 5% compared to diesel engine ;

increased cost of machines with gas diesel compared to diesel mainly due to the cost of a gas storage tank.

In terms of the heat of combustion assigned to a unit mass, natural gas practically does not differ from diesel fuel. If the heat of combustion is attributed to a unit volume, then there will be difficulties in placing gas cylinders on the car, since its volume, even when removed to 20.0 MPa, exceeds the volume of the energy-equivalent diesel fuel by 5-6 times. If the gas is transported in a liquefied state in a cryogenic tank, the design of the car is simplified, and

the period between fuelling is increased to an acceptable level. However, the production and storage of reduced natural gas under conditions of agricultural production is a technical task that will require a large amount of money.

The increase of the vehicle weight when using compressed gas as the main fuel is determined by the requirements for the periodicity of filling with the cylinder material.

The propellant gas propensity to burn at increased speeds is determined by a methane number, the value of which corresponds to the percentage of methane in the mixture with hydrogen and has the same combustion rate as this gas.

Propane, butane and the reduced oil gas consisting of them have low methane numbers, which limits their use in gas diesel. The very high methane number in the sewer gas is due to an admixture of carbon dioxide. Admixture of other nitral gases, such as nitrogen, can significantly increase the methane number of any gas. Even the methane number of hydrogen can be increased to 100 by mixing 60% nitrogen. Combining gas-air mixtures also leads to a significant increase in their methane number.

The low methane numbers of propane and butane do not allow to increase the degree of substitution or diesel fuel in the gas diesel while operating at full load of more than 20%. When operating on partial loads, this fraction can be increased to 4050%, but in real conditions it remains significantly lower than when using gases with a high methane number, in particular natural gas.

Design Object Analysis

1.1.Performance of the enterprise and organization of its production process.

The road construction department was founded on April 1, 1968. In 1972, an asphalt concrete plant was built in Bender. The plant became part of DRSU. The department was engaged in the repair and construction of roads in the city of Bender and adjacent villages, as well as in NovoAnensky, Suvorov and Kaushansky districts.

In 1980, a new administrative building, a club, a dining room, and new repair and mechanical workshops were built. A rack for washing machines, a lathe was put into operation.

The company has expanded. The staff increased to 140 people. There were three road repair sections:

Uch. No. 1 - Overhaul

Uch. No. 2 - Medium repair

Uch. No. 3 - Maintenance

In s. Mirineshty built a recreation center "Kommunalnik," where DRSU workers rested and were treated. All workers were provided (with harmful conditions) with milk, special. shoes and special. clothing.

Since 1990, due to the political situation and lack of financial resources, the enterprise has reduced the volume of work and the number of employees.

At the moment, the number of employees is 48 of them:

Head - 1

Wizard - 2

Ch. engineer - 1

PTO Engineer - 2

Accountant - 2

Mechanic - 1

Manager - 1

Occupational Safety Engineer - 1

Storekeeper - 1

Workers - 22

Drivers and machine operators - 12

Security - 2

1.1.1 Ownership of the enterprise, types of products produced, production links with other enterprises.

Bendery Road Construction Operation Department is a municipal enterprise. This company is directly subordinate to the Office of Housing and Communal Services of Bender and is the object of the construction industry. MP DSEU is owned by the Bender City Council of People's Deputies. The company is in the operational management of the State Administration of Bender.

The main activity of the enterprise is the overhaul and ongoing repair of roads and sidewalks, as well as the maintenance and repair of storm sewers and bridges. The work performed by the MT DSEU can be classified as follows:

Earthworks:

vertical layout;

soil development;

soil compaction;

drainage device;

Work on construction, repair and maintenance of outdoor networks of urban storm sewage:

arrangement of bases for pipelines;

laying of pipelines from asbestos-cement and reinforced concrete pipes;

arrangement of storm sewage inspection and reception wells;

replacement and installation of hatches, screens;

repair of inspection and rainwater wells;

maintenance and cleaning of storm sewage network;

3. Road repair and construction works:

arrangement of underlying and leveling layers of the base;

arrangement of bases from sand-gravel mixtures;

arrangement of bases and coatings from crushed stone materials;

installation of side stones;

construction of road and paving surfaces from concrete slabs;

arrangement of coatings from cold and hot asphalt concrete mixtures;

arrangement of cement concrete bases and coatings;

arrangement of paths and sidewalks;

carrying out work on the current, medium and overhaul of city roads and sidewalks;

restoration of pavements of roads and sidewalks after repair of underground engineering networks;

preparation of asphalt concrete mixtures and side stones.

DSEU MP maintains permanent production ties with the enterprises of Vodokanalkhoz, Electric Networks and Bender GAZ LLC. The rest of the necessary raw materials, components, spare parts, semi-finished products of the DSEU MP is purchased from various organizations, including outside the republic.

1.1.2. The general characteristics of the enterprise and by the characteristics of the classification of the enterprise, the organizational structure of management and the functions of structural divisions.

The municipal enterprise "Bender Road Construction and Production Administration," is the property of the state. The powers of the owner of state property assigned to the enterprise in terms of control over the movement and efficiency of use are exercised by the Bender City Council of People's Deputies. The company is in the operational management of the State Administration of Bender. The DSEU MP operates on the basis of the Law of the Pridnestrovian Moldavian Republic "On entrepreneurial activities and enterprises in the PMR," the Law "On Property of the PMR," the Charter, and current legislation.

The enterprise is a legal entity, has an independent balance sheet, separate property, settlement, currency and other accounts in banking institutions, has a seal with its name and image of the state emblem of the PMR, stamps, forms, may have service marks, trademark and other details. DSEU MP operates on the principles of self-calculation, self-reliance and self-financing, based on the use of municipal property assigned to the enterprise.

The location of the MP DSEU in Bender, st. Kiev, d.20. The main objectives of the Enterprise are:

- Profit generation;

- satisfaction of public needs for saturation of the market in its products, works and services;

- realization of social and economic interests of the members of the labor collective and interests of the state on the basis of the obtained profit, including creation of conditions for increase of production efficiency, reliability of material and technical support, improvement of stability of economic and financial situation; Participation in solving employment problems.

The subject of the economic activity of MP DSEU is:

- road repair and construction works;

- civil works;

- preparation of design and estimate documentation for road works ;

- works on operation and maintenance of road-bridge facilities;

- production of construction products and small architectural forms ;

- mediation activities;

- trade and procurement activities with the right to open a store in the manner prescribed by law;

- external economic activity;

- production of consumer goods;

- auto services, freight (if licensed).

DSEU MP carries out any economic activities that are not prohibited by the current legislation.

The property of MP DSEU, as well as property acquired by him as a result of entrepreneurial activity, is municipal property and belongs to MP DSEU on the rights of full economic management.

The results of economic and other use of property, including production products and revenues, shall be owned by the state, unless otherwise provided by the agreement between the Enterprise and the Owner.

The production structure of the enterprise is composed of its production divisions: workshops, sections serving farms and services, and connections between them taken together.

At the head of the DSEU MP is the head of the department, whose reporting directly includes the deputy head for production, the chief accountant, the personnel department, the dispatcher, the safety and health engineer, and the supply agent. Deputy. three road sections, repair and mechanical workshops, an asphalt concrete plant, and a planning and technical department report to the head of production. The chief accountant is subordinate to accounting, economist, warehouse.

1.3. Analysis of existing mechanization tools and technology for facility design.

At the enterprise of MP DSEU in Bender there is a wide choice of cars, various brands. These cars are designed to perform a wide variety of road construction work. Long-term and reliable operation of the car is provided with proper operation and modern maintenance.

In the main directions of economic and social development of the USSR for 19861990 years and for the period up to 2000, the accelerated development of the machine-building complex, in particular the automotive industry with an increase in the reliability of cars, improvement and operational qualities and working conditions of the driver, was envisaged. Emphasizing also that the machines created in terms of techno-economic indicators per unit of productivity and other beneficial effect should exceed the best of the world

Process Section

2.1. Properties of compressed natural gas as an alternative fuel for diesel engines.

As we mentioned above, compressed natural gas is the best substitutes for diesel fuel, so we will describe the properties of this gas in the future.

Compressed natural gas is a full fuel for automotive engines that do not require significant processing. The expansion of the network of main gas pipelines covering large areas of the country opens up a favorable prospect of using compressed natural gas as fuel for gas turbine engines.

2.1.1. Operational and technical requirements for gas fuel.

The gas must mix well with air to form a homogeneous combustible mixture, provide high heat of combustion of the combustible mixture, and do not detonate during combustion of the combustible mixture. The content of substances in the gas that contribute to the formation and contaminants of the food system, as well as corrosive parts, should be minimal. Compressed natural gas meets these requirements most fully.

Currently, compressed natural gas is an octane number by which the detonation resistance of hydrocarbon gases is evaluated. The higher the octane number of the gas, the more resistant it is to condensation. For most major components of gases, the octane number is 90... 120.

2.1.4. Filling of car cylinders with compressed gas

The car cylinders are filled with compressed gas at gas-filling compressor stations and special mobile gas stations.

The driver must be well aware of the technology of filling the cylinders with gas and accurately comply with the rules established at the gas filling station and when refueling with a gas tanker. The cylinders of the vehicle shall be filled in the following order:

stop the engine;

switch off the battery;

unscrew and remove the plug from the filling valve on the cross, preliminary clean the valve from dirt;

close the flow valve on the spider;

make sure that the balloon valves are open;

connect the filling hose to the filling valve at the direction of the gas filling station employee or the truck truck operator and make sure that the tip is fully screwed on all threads until stop, open the filling valve (until stop) and fill the cylinders with gas up to stabilized pressure of 20 MPa.

After reaching, wait 3-4 minutes to "seal" the gas and close the filling valve;

release gas from the gas-filling hose into the atmosphere, make sure that there is no pressure in it. Disconnect the hose from the filling valve;

install the plug on the filling valve;

after filling the cylinders, turn on the battery, slowly open the service valve on the cross (until stop), start the engine and leave the gas filling station.

2.2. Peculiarities of engine working process when using different gaseous fuels.

In engines, gas is supplied to the inlet pipeline or directly to the cylinders, where it manages to form a practically halogen mixture with air and with residual gases before ignition. Most diesel engines of the autotractor type have practically no cylinder wiring due to the small overlap of the gas distribution phases. Therefore, they can supply gas to the inlet pipeline without fear of losses during the closing of the gas distribution phases. Relatively small volumes of inlet pipelines reduce the risk of damage and destruction of air filters due to the high level of ignition of the mixture, for example, in process disturbances, in cylinders and protracted combustion of the working mixture.

The direct supply of gas in cylinders during the intake or compression process is used only on large engines equipped with special gas valves in each cylinder.

The formation of a halogen gas-air mixture in the cylinder allows full use of the air charge, that is, it is more effective to write off the gas in the absence of air loss with significantly less formation of incomplete combustion products than occurs when the heterogeneous mixture of diesel fuel injected in the engine cylinder immediately before ignition and during combustion.

Comparing the specific heat of combustion of stoichiometric mixtures of natural gas and diesel fuel (see Table 2.4.), it is possible to make an erroneous conclusion about the worst power characteristics of gas cylinder compared to the base diesel engine. However, in practice, the results of the conversion of the diesel to the gas process indicate the possibility of obtaining the same or greater power when operating on gas than on diesel fuel, since the gas-air mixture pre-prepared in the intake process burns at a high speed and without smoke, as a result of which the excess air ratio can be reduced to almost a stoichiometric level. The air contained in the above-piston gap, in the valve recesses, as well as in the gap around the head of the diesel piston, is practically not involved in the combustion process at the position of the upper dead center piston, that is, during the period when the heat generated is used with the highest efficiency.

2.3.1. Gas Power System

This system allows the Kamaz740 diesel to operate both on a mixture of natural gas (methane) and clean diesel fuel. Compressed gas is contained in steel cylinders located depending on the model of the car. When the flow valve located on the spider is opened, the gas is sent through the pipeline to the preheater and then to the high pressure reducer, after which the gas pressure decreases to 0.951.1 PMa. Gas is supplied from reducer to solenoid valve. At the inlet of the valves, a removable felt filter is built in, closed with an aluminum cap. When the electric valve is switched on, the gas enters the inlet of the double-sided low pressure reducer, where the gas pressure is additionally reduced to atmospheric pressure. Gas is supplied from gas reducer through pipeline to gas metering unit, which supplies required amount of gas to diffuser of gas system. In the system, the gas is mixed with air coming from the air cleaner. The operation of the gas system is controlled by a low pressure pressure gauge, which is installed in the driver's cab.

The pressure after the first stage of the low pressure reducer should be exactly 0.180.22 MPa. The gas pressure in the cylinders is controlled by a pressure gauge designed for a pressure of 24 MPa, which is installed on the first cylinder .

The pressure in the chamber of the high pressure reducer of 0.951.1 MPa can be adjusted in a specialized workshop for the repair of gas equipment. In order to exclude the effect of increase of the inlet duct discharge on the gas flow rate and power parameters of the engine in case of air cleaner contamination, a gas flow rate correction system is provided depending on the degree of air cleaner contamination. Principle of correction system operation consists in the fact that gas flow rate characteristic is insensitive to change of inlet path resistance by means of communication of membrane gas reducer with inlet path in section between air cleaner and systems. In this case, any additional resistance of the air cleaner equally affects the membrane of the gas reducer both from the side of the submembrane cavity and from the side of the membrane cavity, without disturbing its equilibrium state. Thereby, the gas flow rate is stable.

2.3.2. Gas preheater

When working on natural gas with a high moisture and carbon dioxide content, gas preheating is necessary, especially in winter. In the absence of a heater, moisture can freeze in the high pressure reducer, and the normal operation of the gas diesel engine is disrupted. To prevent this, the car is equipped with a gas heater, which is located in front of the high pressure reduction gear.

The preheater consists of a housing, a heat exchange element, branch pipes and connectors. Inlet and outlet branch pipes are connected with pressure cooling system. When the liquid is circulated in the heater housing, the gas is heated. Liquid from the cooling system is taken from the left water pipe and drained into the thermostat box.

If water is used as a cooling liquid, the gas heater is connected only after heating the engine, while the valves must be closed and one open. After heating, the first valves should be opened, and the last one should be closed, so that hot water will flow into the gas heater. When parking in winter, the water from the heater must be drained.

2.3.4. Electromagnetic gas valve with filter

Gas at a pressure of 0.951.1 MPa from the high pressure reducer is supplied to the solenoid valve by a high pressure signal. The valve is attached on the bracket to the engine inlet connection manifold. Filter consists of housing, solenoid valve, aluminium valve, supply and discharge nozzles. In diesel mode, the electromagnet valve under the action of the spring is in the closed position and does not pass gas to the low pressure reducer. When the engine goes to the gas-diesel mode, the valve opens, and the gas filtered from mechanical impurities enters the low-pressure reducer, then to the gas reducer and mixer. The filter cap, when installed on the housing, is sealed with a rubber ring and a copper gasket installed under the bolt head.

2.3.5. Gas reducer

Gas reducer is a two-stage automatic pneumatic valve of membrane type with lever transmission from membranes to valves. The main purpose of the reducer is to reduce the pressure of the gas supplied to the dosing mixer.

To ensure reliable closure of gas pipeline at non-operating engine there is a membrane-spring type unloading device connected to engine inlet pipeline. When the engine is not operating, the reduction gear serves as an automatic valve that tightly closes the gas outlet to the mixer.

The reducer has two stages, each of which contains a control valve, a flat membrane made of rubber tissue, a spring and a lever connected by the membrane to the valve. Both stages of reduction gear together with unloading device are combined in one unit.

When the flow valve is opened, gas from the cylinder passes through gas filters and fills the cavity in the first stage of the reduction gear box. With a non-operating engine, the force arising from the pressure of the gases on the membrane sets the spring force and the force from the gas pressure on the valve, as a result of which the latter presses against the seat and tightly closes the inlet hole.

The valve of the second step is in the closed state and is densely pressed to a saddle by springs from which effort is transmitted through a core, a rod, the lever and the pusher.

At the moment of engine transition to gas diesel mode, unloading membrane, cavity under which is connected through union and rubber tube to diffuser of gas mixer, bends under action of discharge, removes conical spring and expands valve. The spring force becomes insufficient to keep the valve in the closed position, it is opened under the action of gas pressure from the cavity to the valve. The gas pressure in the cavity of the first stage is set within O, 180.22 MPa.

At low gas flow rate, overpressure is created in the second stage cavity. As gas flow rate increases, pressure in the cavity gradually decreases, at that the valve under action of gas from the cavity of the first stage leaves the seat by a certain value, increasing the cross-sectional area of the flow channel. From the cavity of the second stage gas is supplied to the gas dispenser, from where it is sent to the mixer.

The gas filter of the reducer is designed to clean gas from the smallest particles of dust, rust and other mechanical impurities, which can violate the tightness of the reducer valves.

The filter is installed at the inlet to the first stage of the gas reducer. The filtering elements are a mesh screwed onto the frame, which is inserted into the housing. The filter element is screwed together with the plug.

The filter mesh should be cleaned during the second maintenance and if necessary. Filter clogging can be detected using a gas reducer pressure gauge: a sharp drop in gas pressure in the cavity of the first stage of the reducer with an increase in the opening of the doser flap indicates filter clogging. To clean the filter mesh, remove the filter element, remove the spring holder, and unfold the mesh. Rinse the mesh in gasoline, acetone or some other solvent and blow it with compressed air. This operation should be performed on a reduction gear removed from the tractor. In case of severe contamination of the copper mesh and in cases where it is difficult to wash it, it is necessary to put a new mesh. When assembling the filter after cleaning, pay attention to the quality of the sealing gasket between the housing and the element. After each filter assembly check tightness of threaded content. The gearbox can be adjusted only in a specialized workshop with compressed air. The pressure in the first stage of the reducer is adjusted by changing the spring force using an adjusted nut: when the nut is turned, the pressure increases, when the nut is turned away, it decreases. At low engine speed at idling the gas pressure in the cavity of the first stage of reduction gear box must be 0.18 - 0.22 MPa.

The gas pressure in the cavity of the second stage of the reducer is controlled by changing the spring force when the adjusting pressure screw is screwed in, and when the screw is screwed in, it decreases. At the manufacturer, the pressure at the outlet of the second stage is adjusted by 100150 Pa.

When adjusting the reducer, check the stroke of the second stage valve. To do this, check the rod travel. Sufficient valve stroke is provided at rod stroke of not less than 5 mm. Adjust the valve stroke when the flow valve is open in the following order: remove the hatch cover, loosen the lock nut and turn out the adjustment screw until the valve starts to pass the gas. Then screw the adjustment screw by 1/81/4 turn and determine by hearing the moment of gas leak cessation. After that tighten the lock nut, close the flow valve and check the valve stroke along the rod. If the travel of the membrane rod is not less than 5 mm, then stop the adjustment and install the hatch cover in place. If the rod stroke is 5 mm. And yet, this indicates a malfunction of the gas reducer, it should be disassembled and eliminated.

During operation, the gearbox must be cleaned periodically and individual units repaired. The first stage of the reduction gear consists of two main units: a valve with an inlet connector and a membrane with a lever gear, a spring and an adjustment nut. Disassembly of the units of the first stage of the reduction gear box is performed in the following sequence: loosen the lock nut, remove the adjusting nut, remove the spring, remove the place of the cover attachment nuts, remove the cover and then remove the membrane assembly. To remove the valve assembly, remove the lever axis. The filter body is previously removed to unscrew the valve seat.

After cleaning of repair or replacement of parts of the first stage, assembly is performed in reverse sequence. When assembling, install the membrane so that the center of its upper plane is below the parting plane by 1.5 mm. Adjustment of membrane position is performed by means of adjusting screw and lock nut. The second stage of the reduction gear consists of two units: the first unit includes a valve with a seat, an adjustment screw with a lock nut and a lever with an axis, the second - a membrane with an amplifying disk, a rod screwed into a rod, a spring with an adjustment nipple, a lock nut, a reduction gear cover and an unloading device.

To disassemble the second stage of the reducer, remove the adapter connector, remove the pin from the rod and spring, remove the bolt and remove the reducer cover. Remove rod with rod together with membrane assembly.

Before removing the unloading device from the reducer housing, loosen the sealing bushing by removing the connector on two three screws. To disassemble the unloading device, remove eight screws, after which all parts are freely removed.

After removing the unloading device, proceed to remove the valve of the second stage of the reduction gear box. To do this, open the hatch cover, then loosen the lock nut, remove the screw with the pusher, remove the valve. After cleaning, washing or repair of parts, assembly is performed in reverse sequence.

When assembling the gas gearbox, observe the frequency and pay attention to the following:

Gearbox housing, and all parts shall be thoroughly washed, membranes shall have no damages and folds. Complete gas impermeability of the membranes is required.

The newly installed membranes of the first and second stage must have a properly located hole for bolts and rod, the aluminum discs of the membrane of the second stage must have an even surface and tightly squeeze the membrane with their edges, the new valve of the first stage and the valve seat must be checked for tightness with compressed air at a special installation before installation in the reducer. All ball connections and valves shall be free to move without increased friction. When assembled, movable parts are lubricated with technical vaseline or solidol, valve seats must not have hairlines and scratches, if there are damage to the valve, replace.

The failure of the gas reduction gearbox is most often the following, in violation of tightness, that is, in the passage of gas through the valves when the engine is not operating, there is no or insufficient gas supply or an excessively high discharge at the outlet.

In case of tightness violation of the valve of the first stage at non-operating engine, the pressure in the cavity of the first stage of the reducer increases and gas begins to enter through the valve of the second stage. The non-tightness of the first stage valve can be detected using a low pressure pressure gauge. When gas passes through the valve of the first stage, the pressure in the cavity of the first stage will increase until the opening of the valve of the second stage. After that, the gauge arrow will remain stationary.

First stage valve tightness failure can be caused by the following reasons:

- by falling on the working surface of the valve and seat mechanical impurities (rust, metal chips, dust, etc.)

- seat and valve contamination;

- damage of the lever of the first stage of the reduction gear box.

A minor tightness violation of the first stage valve does not have a noticeable effect on the engine operation, but the violation should be eliminated. If the seal is damaged, there is no need to change the seat. Damage to the valve seat of the first stage can be repaired by clipping and grinding its end. The non-tightness of the valve of the second stage of the reduction gear box during installation of the engine causes a gas leak from the reduction gear box to the diesel intake system.

The tightness of the valve of the second stage of the reducer can be caused by the following reasons:

-high high gas pressure after the first stage due to the fact that the adjusting nut is too deeply screwed.

-a very deep position of the adjusting nipple, as a result of which the spring of the second stage membrane is completely weakened and the valve on closes, as the nipple rests against the membrane.

- difficult movement of the valve in the guide;

- closing of lock nut and turning of valve adjusting screw;

- tight rotation on the axis of the lever of the second stage of the treductor;

- accumulation under the valve of metal chips, rust, etc.

- damage to the rubber seal;

- failure of tightness of the valve of the first stage of the reducer;

Damage to the valve seat of the second stage can be eliminated by clipping or grinding its end face.

Leaks of the gearbox membranes can be caused by the following reasons:

-interest assembly,

-Rupture of membrane ,

- porosity of its material,

- separation of the membrane by various chemical substances formed in the gearbox cavities as a result of pressure reduction.

If the first stage membrane is leaking, the gas will escape under excessive pressure through an opening in the adjusting nut of the first stage spring. If the gas flow is insignificant and leaks occur during engine operation, the operation of the gearbox and the fuel supply of the engine are not completely disturbed, so this defect can be detected when the engine stops.

With very small gas passes, the membrane of the second stage of the reduction gear box also does not completely disturb the supply of gas to the engine. If the pressure of the second stage of the reduction gearbox is higher than atmospheric, then if the membrane of the second stage is leaking, the gas will escape through the cover of the second stage adjustment nipple, therefore it will not be difficult to detect a malfunction.

If the membrane of the discharge device is damaged, the gas from the reduction gear box will flow through the nozzle directly to the diffuser of the mixer, therefore, the normal operation of the reduction gear box and the engine is disrupted.

If any of the gearbox membranes fail, replace it.

The resulting causes of increase of reduction gear box output cavity discharge at full engine load are:

-lock of filters, as a result of which less gas is supplied to the reduction gear box. The clogging of the reducers can be detected by a sharp drop in gas pressure in the cavity of the first stage of the reducer when switching to load modes, determined by the pressure gauge of the gas reducer. Clean the filter as above;

- insufficient opening of the first stage valve. As a result of this, the pressure of the first stage cavity decreases sharply at high gas flow rates, determined by the pressure gauge of the gas reducer. The required valve stroke of the first step is established at assembly of a reducer;

- expansion of the rubber seal of the valves of the first and second stages of the gas reducer, reduction of the cross-sectional area of the gas flow valve and pressure drop during operation of the engine with high loads;

- incorrect adjustment of tightening moment of the second stage spring of the reduction gear box;

- insufficient opening of cylinder valves or service valve;

damage, clogging or disconnection of the tube connecting the vacuum cavity of the reduction gear discharge device with the mixer diffuser;

- low gas pressure in cylinders less than 0.9 MPa

For normal operation of the gearbox, the faults must be eliminated immediately.

2.3.6. Adjustment of gas reduction gear box

To adjust the gear box:

close the flow valve on the spider;

disconnect the hoses from the reducer branch pipes and the reducer filter connector;

insert a plug with a tube to connect the gasometer hose into the outlet pipe hole of the reducer. Connect the T-joint with the piezometer hose to the cover branch pipe. The tee tube is used to transfer the discharge from the vacuum pump to the cavity of the gearbox unloading device through the hose. Compressed air supply from the compressor unit to the cavity of the first stage of the reduction gear box at pressure of 0.220.6 MPa. It is carried out by a hose connected to the connector of the reduction gear filter (you can correct the pneumatic system of the car when the engine is off).

The gas pressure of the first stage cavity is controlled by a nut. When the nut is screwed in, the pressure in the cavity will decrease. Pressure is controlled by the pressure gauge in the driver's cab. When adjustment is complete, tighten the lock nut.

Before adjusting the gas pressure, adjust the second stage cavities by opening the second stage valve. To do this, remove the cover, loosen the lock nut and remove the adjusting screw until the air enters through the valve of the second stage (check for hearing). Then screw in the adjusting screw by 1/81/4 turn, determining by hearing the moment of air leak stop through the valve, and tighten the lock nut. Through the tube transfer the discharge to the cavity of the reduction gear box unloading device, set its value equal to 0.70.8 kPa by piezometer. The second stage valve must open. After the discharge is removed, the valve shall close the opening in the valve seat tightly.

The gas pressure in the second stage cavity is controlled by a nipple. When the nipple is screwed in, the pressure in the cavity will increase. Supply 1 kPa discharge through the tube to the cavity of the unloading device, monitoring its value by piezometer. Turn the nipple to set the pressure in the second stage cavity by 0.10.15 kPa more than atmospheric one.

After adjustment tighten lock nut, remove adapter connector and check rod travel. If the second valve is less than 5 mm when opening the valve, disassemble the gearbox and eliminate the malfunction.

2.3.7. The valve.

The gas-balloon installation of the tractor has 4 special valves: filling two balloons and consumable. VMH1 valve is used as filling valve, as consumable and balloon VMP1 valve. The valves have the same design, differ only in threads on the side union (the filling valve has special, left thread). To connect the gas pipeline, the adapter with sealing gasket is turned on the side connector.

2.3.8. Gas pipelines.

All gas pipelines from the cylinders from the high pressure reducer are made of steel thick-walled tubes with an outer diameter of 10 ± 0.15 mm and a wall thickness of 2 mm.

Connections of gas pipelines with adapters, valves and other elements of gas equipment are carried out using a wireless nipple connection of the type "rotating ring" and allow multiple disassembly. When tightening the overlay nut, the ring is deformed and takes the form of an internal hole in the connector. At the same time, the ring is cut by the inner edge into the tube wall, preventing its explosion from the joint under the influence of high pressure .

When replacing the nipple, it is necessary to ensure that the new nipple is installed at a distance of 2-3 mm from the end of the tube. If the nipple does not provide tightness of the connection after tightening of the nut, replace it. The faulty nipple is trimmed together with a small piece of tube. From the outside, all pipes of the high pressure gas pipeline are painted with paint to protect against corrosion.

It is not allowed to install tubes with a ring tie-in less than 2 mm from the end of the tube.

If it is necessary to assemble a tube with swivel nuts and rings, it should be pre-pressed and cut into the tube wall at a distance of 2-3 mm from the end of the tube.

Preliminary cutting of rings into walls of tube assembled with swivel nuts is performed in process connector, which has connection dimensions of connectors of balloon adapters.

Before assembling, clean the ends of a 1315 mm long tube of paint or anti-corrosion coating. The tube must be inserted into the hole until stop. The tightening torque of the swivel nut during the ring pre-cut must be 4050 Nm. After pre-cut check the nipple condition. Beams shall have no cracks or other damages.

Installation of pipelines on the car in violation of these requirements, preliminary soldering by soldering of the ring and flaring of the ends of the tubes is not allowed.

The dimensions of the connector for preliminary cutting of the ring are given in the technical documentation. Periodically monitor the conical surface of the hole. If steps appear, replace the connector.

2.3.9. Batcher-mixer

Batcher-mixer is made in one unit, which provides its installation. Gas dispenser is installed in single housing with membrane-type mechanical gas supply limiter and is made in form of throttle device controlled by pedal from driver's cab. The main purpose of the gas dispenser is to control the required amount of gas suppressed into the mixer from the two-stage reducer. Using two studs, the dispenser is attached to the mixer housing, which is a cylinder with a Venturi nozzle dispenser inserted into it. Inside, the diffuser has an annular header for supplying gas through radial holes. The mixer has three functions:

- creates the required discharge at low engine speeds, which allows to act on the "gearbox diaphragm and transfer it from the shut-off valve mode to the operating mode";

- provides uniform mixing of gas and air;

- together with the gas reducer forms the engine speed characteristic.

Control of required amount of gas (generation of load characteristic) is performed by throttle valve. When the accelerator pedal is pressed, the throttle drive pedal opens the throttle through the drive roller and due to the discharge in the mixer diffuser, the gas comes from the reduction gear box to the mixer. Throttle valve is installed on driven roller of doser, which is connected to source of membrane mechanism of gas supply limitation. The diaphragm mechanism allows you to control the position of the throttle valve regardless of the position of the valve actuator lever, for example: rotate the valves to the closing side when the engine reaches the maximum permissible speed.

Mixer metering device is installed between air cleaner and engine intake manifold.

During operation, faults of the dosing mixer may occur, at which the engine will not develop RPM during transfer to operation in gas-diesel mode or there will be an increased gas flow rate and unstable engine operation, and after the engine reaches the maximum speed of "firing" in the exhaust system.

In these cases (in case of known serviceable electrical circuit) possible reasons are:

failure of dosing throttle control drive;

failure of the diaphragm mechanism, at which the dosing valve does not open or close.

If a fault is detected, the mixer must be repaired or adjusted, after which the driving and driven types of the gas dispenser must rotate freely.

All operating processes of the gas diesel must be cleaned periodically from dust and dirt, lubricated and check the tightness of the membrane and the density of the throttle valve.

To check the tightness and control of the gas dispenser, the following devices are necessary: sources of pressure and discharge: bubble chamber, tube supplying air with a diameter of 5 mm, crane, U-shaped vacuum meter, device for installing the dispenser.

2.3.10. Telescopic thrust

When the engine is operating in the gas diesel mode, the telescopic thrust provides movement of the fuel supply pedal due to compression of the thrust spring (after the stroke of the lever of the high pressure fuel pump regulator), thereby changing the position of the throttle valve of the gas dispenser. In diesel mode, the thrust does not provide shock-absorbing action and acts as a liquid element, since its spring is more liquid than the spring of the regulator lever.

Design Section

The main tasks of thermal calculation are: determining the efficiency, specific effective fuel consumption, drawing up the thermal balance of the engine. Thermal calculation allows you to determine the main dimensions of the engine, identify and determine the forces acting on its main parts.

Initial parameters:

Diesel Kamaz-740

Diagram, dimension D * S, 120 * 120

Crankshaft speed p = 2600 min-1

Compression ratio E = 17

Working volume of all cylinders Vh = 10.85 l.

3.1.1. Fuel for the engine.

For gas engines, gas fuel is used in accordance with the requirements of specification 5116683 "Natural compressed gas, fuel for gas balloons"

Grade A - containing 95 ± 5% methane

Brand B - containing 90 ± 5% methane

According to GOST, the fuel for a gas engine has the following elementary composition of one kg. fuel:

C = 0.87

H2 = 0.125

02=0,005

Lower combustion heat Qn = 48000 kJ/kg.

Excess Air Ratio

For engines with an undivided combustion chamber, in which the mixing process is not so perfect, the excess air coefficient can be taken in the range α = 1.4... 2.2. We accept

α =2.

3.6 Working process of gas diesel engine.

The engine can be started only on diesel fuel. All electrical circuits are protected by a fuse. The gas supply system installed on the car consists of a battery of cylinders, a reduction gearbox, a control throttle and a mixer, as well as a filling valve, a service solenoid valve, a control pressure gauge, a control system, connecting rods and pipelines.

Placing the cylinders in the container behind the cabin provides optimal access to it.

To prevent icing of the reducers and the formation of ice plugs in the lines, the gas is heated in the heat exchanger using the heat of the engine coolant. Due to the optimal temperatures of the diesel exhaust gases, it is advisable to use a liquid heater, however, the liquid temperature when switching to gas should not be lower than 5060 ° C. Remote control of the process of switching the power system from diesel fuel to gas fuel, as well as emergency switching of the gas line is carried out using an electromagnetic valve. When using compressed gas up to 20 MPa, the reduction system consists of one multi-stage or two reduction gears. one of which is high pressure up to the level of 1MPa, the other low - up to 1 atm.

Gas is supplied from the reduction gearbox, through a dosing device made with a throttle valve, to the mixer, which is a branch pipe of the Venturi nozzle type. A limiter can be installed on the dosing device to reduce the gas supply when the engine reaches the maximum speed.

The main advantages of gas diesel engines based on diesel engines.

-A significant reduction in toxic substances in exhaust gases compared to gasoline and diesel engines.

- Relative simplicity and low cost of fuel equipment compared to the full transition to gas.

-Low fuel cost.

-Operability in places where there are no gas filling stations.

Disadvantages of gas engines created on the basis of diesel:

-The worst fuel efficiency compared to diesel.

- Decrease of engine power parameters compared to diesel engine, and hence decrease of vehicle capacity with such engine.

-Less gas diesel range than diesel.

-It is not possible to perform conversion of the engine under farm conditions. Conversion takes place as a rule at the factory of the manufacturer of the base engine. - Increase in car cost due to more expensive gas storage system (compared to diesel storage system).

Conclusion

In order to save diesel fuel, taking into account the growing network of gas filling stations, it is possible to use compressed natural gas on cars. The economic characteristics of the gas diesel engine are almost the same as that of the diesel engine. The use of high-pressure cylinders of high alloyed steels and metal plastics provides acceptable pressure on the soil, convenient placement of cylinders, in particular behind the car cabin.

When developing a system for complex use in the production of compressed natural gas, it is advisable to use it on all types of cars. The accumulated foreign experience, the automotive industry, the existing production of gas equipment makes it possible to develop designs of cars adapted for working on gas. At the same time, it is necessary to solve the issues of managing the energy modes of gas cars, manning gas tanks behind the car cabin, taking into account various operating requirements, as well as the requirements for filling and servicing gas equipment in conditions of relatively high dispersion of cars.