Improving the economic performance of the KamAZ-740 diesel engine using pulsed gas turbine pressurization

Contents

Paper

Explanatory note 89 sheets, 19 figures, 2 tables, 20 formulas, 17 sources

Keywords: pulsed gas turbine pressurisation, turbocompressor, exhaust manifold, turbine, power and economic parameters, pulsation

The object of the study is the standard KamAZ-740 engine

The purpose of the work: Based on the analysis of methods of boosting engines and pressurization schemes, develop structural measures for the use of pulsed gas turbine pressurization on the KamAZ-740 diesel engine in order to increase its economic performance

Pulsed gas turbine pressurization was used on the KamAZ-740 engine in order to increase economic and environmental indicators by installing the TKR-7N turbocharger and improving the design of devices. Due to application of this method start-up properties are improved, power indices are increased, as well as reduction of toxicity of exhaust gases

Introduction

The effectiveness of the armed struggle in modern conditions depends to a large extent on the rapid manoeuvre of forces and means, carried out both with the aim of delivering an irresistible strike and to ensure its own survivability. Therefore, the ability of combat units and rear bodies to quickly relocate, that is, their mobility, has become a necessary quality of the Ground Forces. This quality is ensured by the complete motorization of the armed forces, and in particular is achieved by the extensive use of automotive equipment, which is used not only for the transportation of personnel and materiel, but also as a chassis for various types of weapons. Modern models of automotive equipment are complex objects, the effectiveness of which depends on the perfection of many structural elements included in their composition. However, among the most important units and devices that play a decisive role in the formation of the necessary tactical and operational properties of wheeled and tracked vehicles, first of all is the power plant that provides them with energy

Modern engines of wheeled and tracked vehicles are coherent technical devices that embodied many recent achievements in science and engineering. As a result of a long period of development, they have achieved a fairly high degree of perfection and currently have acceptable power, economic and environmental indicators, as well as quite high reliability

The degree of perfection and technical condition of the engine directly depends on the mobility of the machines, their fuel range, reliability for survivability and readiness for operation. The power plant is an integral part of the power supply system of the facility, and has direct connections with all external factors

As a result, the development of military technical requirements for the engine and its systems should be based on a software chain for use in automotive equipment in the Armed Forces. Which in the most general form consists in the perfect transportation of personnel, weapons and materiel to a given area in any road meteorological conditions

In order to achieve this goal, army automotive equipment must have certain tactical and technical data

A significant role in ensuring the combat readiness of troops is also played by the time necessary to bring power plants into service. The listed properties of power plants determine their compliance with the direct purpose of the mechanical energy source and are associated with a group of basic requirements that can be called functional. However, it should be borne in mind that the enforcement of these requirements and the achievement of the goal is limited by a number of restrictive conditions.

However, the importance of the power plant plays a large role in the automotive industry

Most often, diesel engines are used on military automotive equipment, which have proven to be a good power plant that meets the technical requirements for engines of military automotive equipment

On the basis of this, work is underway to improve the power, economic and environmental characteristics of engines. Various methods for improving engines are used, various types of pressurization are used, inflatable air coolers, various types of mixing, configurations of pistons, combustion chambers and many other methods for improving engine performance

One of the most effective methods of forcing the working process of diesel engines is supercharging using exhaust gas energy - gas turbine supercharging. With the help of gas turbine pressurization, it is possible to increase power by 35-40% with almost unchanged weight and dimensions of the base engine and without any significant changes in its design

Unlike many other forcing methods, the increase in power during turbocharging occurs with a simultaneous increase in the economy of the diesel engine

Analysis of the development of the world engine industry showed that among thermal engines, diesel engines in a wide range of changes in the power and speed of the crankshaft of the engine convert the chemical energy of fuel into mechanical work with the highest efficiency, they are about 50% more economical carburetor engines, which will replace carburetor engines in the truck industry and will become more widespread in passenger than currently

The purpose of this project is to improve the exhaust gas system of the KamAZ-740 diesel engine using pressurization

The designed engine shall have improved characteristics of effective power, specific effective fuel consumption and torque without design changes. The application of the pressurization system is the most effective method for solving the problem

1 Analysis of military-technical requirements for power plants of army vehicles

The mass introduction of automotive equipment extremely increased the dependence of troops on technical and operational properties and technical perfection of machines. Hence, in order to ensure the most effective combat operations, wheeled and tracked vehicles in service must meet a set of military technical requirements arising from the tasks of their operational-tactical use on the battlefield and taking into account the specific conditions of army operation

The power plant of a wheeled or tracked vehicle shall:

- have sufficient power, torque margin and acceleration to ensure high dynamic qualities of the machine;

- have high economy in nominal and partial modes to provide, possibly, a larger fuel range and fuel resource consumption;

- have high reliability, characterized by sufficient resource and safety at minimum maintenance and repair costs;

- require a minimum time for actuation, have high start-up properties;

- work on non-deficient grades of fuel and lubricants;

- allow to operate on different fuel grades;

- allow the possibility to be multi-fuel;

- have minimum weight and dimensions;

- have a technological design: do not require for the manufacture of unique equipment, scarce material, have minimal labor input of manufacture and assembly;

- be adapted for transportation in all modes of transport

In addition to these, power plants, like any object of transport, are subject to certain aesthetic, as well as patent and legal requirements

For military-economic evaluation, it is advisable to distinguish a group of properties that characterize the effectiveness of the object. Power plant efficiency refers to the ability to generate a given mechanical energy at the minimum material and economic costs associated with production and operation, as well as with the least negative impact on the functional indicators of the object provided by energy and readiness for use in specific army conditions. The specified level or efficiency assessment should be based on the energy properties of the engine, but at the same time take into account fuel and oil consumption, material capacity and dimensions, start-up properties, the level of standardization and unification, labor intensity of manufacture, maintenance and repair

The reliability of the power plant has a significant impact on the technical and economic efficiency. This is due to the fact that failures of vehicles performing responsible functions in the troops can make it difficult to solve combat or transport tasks and, in addition, require time and funds to restore efficiency. The power plant still plays a decisive role in the overall reliability of automotive equipment. Failure of the engine or its systems completely deprives the machine of the main property - mobility, while failure of other units may not have such consequences

A significant role in ensuring the combat readiness of troops is played by the time required to bring power plants into service and spent on refueling with fuel and lubricants, inspection, preparatory operations, starting and heating of the engine. The main component of this time is the engine start-up time, which at low ambient temperatures determines the readiness of automotive equipment. Therefore, launch properties occupy one of the main places in the structure of military technical requirements for army vehicles

The mass operation of automotive equipment also has to be considered with the consumption of operational materials and labor costs for maintenance and repair, which are becoming increasingly large on a state scale. Therefore, among the most important properties that determine the suitability of the power plant, it is necessary to take into account its operational processability and especially fuel efficiency. The main types of fuels used for modern engines are liquid fuels of petroleum origin: gasoline, kerosene, diesel fuel. These grades are well mastered in terms of technology and, in general, meet the requirements for carrying out working processes with high heat of combustion, provide sufficient autonomy of automotive equipment and allow to obtain the necessary reserves of the vehicles for fuel with a relatively small capacity of fuel tanks, the refueling of which is 4-5% of the payload

In addition, improving the environmental friendliness of engines is of significant military and technical importance, as it provides an increase in the fuel range of vehicles and reduces the volume of fuel and lubricants. It is also extremely important to adapt the engines of army vehicles to work on various types of fuel - multi-fuel. This property makes the fleet of cars not sensitive to inevitable changes in the balance of production and consumption of motor fuels of various types, and in army conditions reduces the dependence of equipment on interruptions in the supply of fuel and lubricants of certain grades

The use of power plants is constantly carried out with the participation of the person who manages them, performs maintenance and repairs. In addition, toxic substances (CO, NO2) contained in the exhaust gases, as well as evaporating from the engine supply system, can act on a person. The increasing saturation of the atmosphere with these harmful emissions is a danger to human health and life. It is necessary to regulate ergonomic properties of power plants due to ease of control and maintenance, as well as related to environmental factors

Modern piston engines do not meet all the requirements for them, as for power plants. Therefore, designers and researchers are engaged in further improving the design of internal combustion engines. One of the most effective methods of forcing the working process of diesel engines is pressurization using exhaust gas energy. With the help of pressurization, it is possible to increase power by 35-50% with almost unchanged weight and dimensions of the base engine and without any significant changes in its design. Due to turbocharging, the acceleration of diesel engines deteriorates when operating in such transient modes as touching from the spot and acceleration. To eliminate these disadvantages, turbines are used, and compressors with adjustable sizes of the flow part, instead of one turbocharger, several turbochargers of smaller sizes are installed, wave pressure systems are used. The layout and design of the diesel truck depends on its carrying capacity. So, for cars with a total weight of 8 to 20 tons, in-line four and six-cylinder, as well as V-shaped six and eight-cylinder diesel engines are used, as a rule, with undivided combustion chambers. Many six and eight-cylinder diesel engines have turbocharges. Some engines use supercharging air cooling, for example, Volvo engines. An example of the layout of diesel engines of this group is the KamAZ-740 car engine, which is currently being installed on army vehicles such as KamAZ

The KamAZ-740 engine operates reliably at any time of the year and day, at air temperature from -400С to + 500С, at relative humidity up to 38%, at dust content of air up to 1.0 g/m3. Has high operational reliability with minimal effort and maintenance time

In addition, the design of the engine provides sufficient survivability under conditions of use of nuclear weapons. In some cases, it is also possible to partially use the engine power to drive various units and special devices, both in the parking lot and during its movement. The simultaneous fulfillment of all the requirements that are imposed on the engines of modern machines is a very difficult task and technically impossible, since these requirements are often contradictory. Therefore, each of the requirements under specific conditions has a different meaning and a different specific gravity. And when designing the engine, they are treated differently

1.2 Increase of engine operating volume

The working volume causes a practically proportional change in the weight of the charge entering the cylinders, which accordingly affects the engine power

The displacement of the engine can be changed both due to the dimension of the cylinders and by changing their number

Increasing the dimension of the cylinder, in addition to directly increasing the weight of the cycle charge, positively affects the working process of the engine. As already noted, the increase in diameter of the cylinder is accompanied by a decrease in its relative surface

In this regard, heat losses associated with heat transfer to the walls of the working cavity are reduced, and thermal use is slightly improved

In addition, in a large cylinder, the relative leakage through the piston rings is reduced.

It should also be noted that in a large cylinder it is easier to organize the directional movement of the air charge, and when injecting fuel, there is no difficulty in matching the range of the flare with the size of the combustion chamber

However, as the size of the engine increases, the mass of the connecting rod-piston group increases proportionally, and the path that the piston passes for each stroke is also extended. These negative features cause a significant increase in inertia forces and average piston speed and force to reduce the number of crankshaft revolutions with an increase in engine dimension. Therefore, it is usually not possible to provide an increase in engine power proportional to the working volume, and the liter power of engines with large working volumes is usually lower than small ones.

To create the required power range of diesel engines, unified families of 6, 8 and 12-cylinder engines are created on the basis of an optimal size cylinder.

1.3 Increase of crankshaft speed

Theoretically, an increase in the number of revolutions would have caused a direct proportional increase in liter power. However, in practice, the speed movement causes an increase in gas dynamic losses at the inlet of fresh charge, and therefore the filling coefficient at a high number of revolutions decreases significantly. Increasing the speed of mutual movement of the parts of the crank mechanism also provides an increase in mechanical losses. The indicator efficiency at high speed can be reduced by transferring a portion of the combustion to the expansion line. In addition, the increase in engine speed is limited by the increase in thermal and mechanical tension of engine parts.

For these reasons, the increase in engine speed must be accompanied by structural measures to increase the filling factor, indicator efficiency and engine life. The most effective of these measures should be considered the increase in valve sizes, special adjustment of inlet and outlet systems, expansion of gas distribution phases

Most modern engines develop maximum power at 2100-3000 min-1 (for diesel engines)

Due to the significant difficulties that arise with an increase in the number of revolutions, the speed of the engines of army vehicles increases quite slowly

1.4 Transition to two-stroke cycle

When organizing a two-stroke cycle, the clock factor in the power equation decreases from Z = 2 to Z = 1. This means that a double number of work cycles occur in the same time. Therefore, the liter power of two-stroke engines should theoretically double

However, cleaning of cylinders from treated gases and its filling with fresh charge in the absence of pump passages cannot be of sufficient quality. Typically, in most two-stroke engine designs, the residual gas ratio is significantly higher and the filling ratio is lower than the four-stroke ones. In addition, part of the working volume of two-stroke engines occupied by the windows is lost during compression and expansion. To organize blowing, a significant amount of power is required to drive the inflatable pump. In this regard, the transition to a two-stroke cycle really allows you to increase liter power not by two, but only by 1.5-1.6 times

Two-stroke engines have worse economy and increased heat stress. The latter creates some difficulties in designing and refining these engines, as a result of which the two-stroke cycle is mainly used in low-power power power plants where their exclusive prostate is used, or in large slow-moving ship and diesel locomotive plants, which are difficult to force by increasing the number of revolutions

1.6 Application of new materials

Due to low density, good casting properties and workability, aluminum alloys are widely used in the production of various parts of the car. The first parts that began to be made of aluminum were pistons and cylinder heads of internal combustion engines. Good thermal conductivity of aluminum was also used. Subsequently, various bodies, tanks, containers began to be made from it, in order to achieve the necessary strength, which did not require a large wall thickness and, conversely, during injection molding, these walls were made thinner

Moulds produced by injection molding into steel molds achieve high accuracy, which significantly reduces the number of processing operations, limiting them only to the treatment of mounting surfaces. Pressure castings are increasingly used for internal combustion crankcase applications. This requires special equipment and devices for forming a coolant jacket in the casting, however, large mass savings pay off all the costs

The decrease in weight when aluminum is used instead of cast iron is almost proportional to the ratio of densities of these materials equal to 7.3: 2.7. The cast aluminum alloy part is almost three times lighter than the same cast iron part. Comparative studies of the cost of cast iron and aluminum cylinder blocks for a gasoline engine of 1800-2200 cm3 in recent years have shown the advantages of using aluminum. The comparison was carried out throughout the production cycle: from the manufacture of rods, melt, casting and to the final machining. The weight of the untreated casting is 72 kg using cast iron and 23 kg aluminum. Treated cast iron block weighs 44.5 kg, aluminum - 14.4 kg

The energy consumed for all casting and processing operations was also compared. 6,500 kW is required for the release of 3000 pieces of cast iron units per day and 1,100 kW for the same number of aluminium units

The study shows that from the point of view of energy costs in the case of manufacturing an aluminum block, energy savings are 60% compared to cast iron. Therefore, despite the higher price of aluminum, its use for the cylinder block, as well as other castings, is advantageous. The effect of weight reduction will be manifested during operation in lower fuel consumption

There are other examples of weight reduction when grey iron is replaced with aluminum. In an inline four-cylinder engine "Chevrolet-Vega" (USA) with a working volume of 2300 cm3, the cast iron block has a mass of 39.5 kg, and the same block of aluminum - 13.6 kg, that is, a mass reduction of 65%. The six-cylinder Rambler-Custom engine of AmericanMotors company has a mass of 30 kg. the weight of the same cast iron block is 76 kg. Weight reduction in this case reaches 61%

Similar figures are typical for cylinders of small air-cooled engines, where the mass decrease also reaches 60%. The cast iron cylinder with finning of a 250cm3 two-stroke engine has a mass of 8.15 kg, and the same aluminum cylinder with a hard chrome coating of the working surface - 3.15 kg, which corresponds to a mass decrease of 62%

Aluminum cylinder blocks of engines provide not only a reduction in weight, but also an improvement in thermal conditions. Heat transfer and heat removal to the cooling system are improved, the temperature fields of the block head and cylinders become more uniform, which is no less important than weight reduction. First of all, local overheating near the outlet valve is reduced, and the distribution of temperature over the surface of the cylinder becomes more uniform

The cylinder retains its shape in the heated state, which is important for the fit of the piston rings along the entire circumference and, in turn, has an effect on the penetration of oil into the combustion chamber. In the conventional use of aluminum pistons, greater thermal expansion of aluminum cylinders is advantageous in that the clearance between the cylinder and the piston can be reduced, which reduces the noise level of the engine

Conclusion: the most effective methods of increasing economic indicators are; high compression ratio, use of poor combustible mixtures, improved quality of mixing, high mechanical efficiency. These methods have found great application in modern mechanical engineering

2 Design analysis of modern gas turbine pressurization systems

Currently, two types of gas turbine pressurization systems have become widespread: isobaric (i.e., pressurization at constant pressure) and pulsed (pressurization at alternating pressure). Each system is described below on the example of existing designs of automobile diesel engines

2.2 Impulse pressurizing system

In pulse systems, the outlet manifolds are divided into sections. Connected to each section is a group of cylinders where the discharge strokes do not overlap, i.e. the discharge stroke in one cylinder ends before the discharge begins in the next cylinder of that section. Respectively, the turbine supply pipes of the turbocompressor, up to the impeller, are also separated.

Such a system was used on the 8DVT- engine

This system includes two exhaust manifolds, each of which is divided into sections combining two cylinders and two turbochargers (one for each row of cylinders)

Exhaust gases are supplied to turbine of turbocompressor by outlet manifolds, which combine outlet branch pipes of separate cylinders in accordance with alternation of exhaust strokes. Manifolds are cast from cast iron and made detachable to compensate for thermal expansions, and compensators are installed in places of connection of individual parts. Air is supplied to the engine cylinders by two TKR-11 turbochargers. The use of two compressors led to the installation of a supercharging air receiver in front of the outlet nozzles to equalize the pressurizing pressure on the right and left rows of cylinders

The use of pulsed pressurization made it possible to achieve a nominal power of 272 kW and fuel economy of 238 g/kWh.

The advantage of a pulsed pressurization system is the absence of superposition of pressure waves, which contributes to better cleaning of cylinders when closing valves. At the same time, the gas turbine power is about 20% more than the constant pressure turbine power. Due to this, at the same average pressure in the header, a higher pressurization pressure can be obtained

At the same time, with a pulsed pressurization system, the pressure upstream of the turbine varies widely and for a significant part of the cycle differs significantly from the calculated one, therefore, the efficiency of the turbine in the pulsed system is lower than that of the isobaric one. In addition, with a pulse system, gas from each section of the exhaust manifold is supplied only to a part of the impeller, which also reduces the efficiency of the turbine

Disadvantages of the pulsed pressurization system include pressure surges during the transition of the blade from one section of the guide vane to another. Under the influence of pressure surges, forced fluctuations of the blades occur, which can lead to resonance and crack formation, and then to blade break. With a pulsed pressurization system, in the case of a late pulse, the average back pressure increases during the exhaust stroke and negative operation of the pump strokes occurs, i.e., the mechanical efficiency of the engine decreases

Pulsed pressurization system found application in diesel engines with nominal frequencies up to 2000 min

2.3 Two-stage gas turbine supercharging system with intermediate supercharging air cooling

The two-stage pressurization system includes:

- high pressure turbocompressor;

- low pressure turbocompressor;

- supercharging air coolers for each stage;

- auxiliary combustion chamber

The features of this system are as follows:

supercharging air cooler installed behind high-pressure stage compressor is made so that in engine warm-up mode air is supplied from compressor both to intake manifold and through combustion chamber to turbine of turbocompressor. During engine operation, air from compressor is supplied to cooler and intake manifold, and in parallel hot air is supplied through bypass to combustion chamber;

- additional combustion chamber is installed in bypass between compressor outlet and turbine inlet. At that, at low frequency modes of crankshaft rotation, combustion chamber provides heating of bypass air to maintain air pressure specified by cycle feed

With respect to single-stage supercharging, the two-stage supercharging has the following advantages:

- a significantly higher level of pressurization pressure and therefore the possibility of obtaining large average pressure values;

- higher efficiency of the system at even pressurization pressure;

a wider field of performance and therefore better adaptability to the desired range of engine operation;

- application of supercharging air cooling made it possible to increase the number of charges supplied to the cylinders, slightly reduce the heat stress of the parts and the content of harmful components in the exhaust gases

The disadvantages of this system are the worst acceleration, since two successive compressor rotors must accelerate, between which the existing pressure drop is distributed. In addition, the complexity of the design reduces the possibility of using this system on military automotive engines

2.6 Turbocompressor with electric drive

The Booster system includes an electrically driven turbocharger that can be located before or after the main turbocharger, the overall compression ratio being defined as the product of the compression ratios of both devices. This system eliminates the impact of turbocharging inertia on the working process and is expected to significantly increase the specific power of the engine

The latter means that an engine with a smaller displacement must develop the same power as its larger predecessor; this will reduce specific fuel consumption and emissions

The main advantage of the Booster system is the ability to maintain the shape of speed characteristics when moving from a larger engine to a smaller one, as well as significantly reduce thermal and mechanical loads on electrical and electronic components compared to an electrically driven turbocharger

Currently, electric turbocompressors are widely used in mass production

3.2 Peculiarities of TKR-7N turbocharger arrangement

Based on the previous analysis, it is planned to use a combined gas turbine pressurization system. This system includes two interchangeable turbocompressors of TKR-7N model, inlet and outlet manifolds, pulse converters and connecting pipes

Use of two small turbocompressors with small moments of rotors inertia as pressurizing units increases engine acceleration and fuel efficiency

3.2.1 Compressor

Compressor housing assembly (made of aluminium alloy) with open spiral chamber and aluminium disk pressed into it, forming front wall, which has cone slope, which enters annular flat surface

Roughness of inner surfaces of compressor housing at injection molding R = 40. Confuser air supply channel to wheel. The outer surface of the inlet pipe is smooth, after machining. Outlet branch pipe has collar for attachment of transient flexible connections. Compressor housing together with compressor steel screen forming diffuser rear wall is secured to bearing aluminium housing by six bolts. Based on the features of JI installation on the engine, it is advisable to have the housing position not fixed (the compressor housing must rotate freely about the rotor axis)

The compressor wheel should be made of aluminium by precise casting into a chill under a controlled pressure drop. The use of a light alloy compressor wheel will reduce engine acceleration. Wheel has twelve radial blades of parabolic profile. Swirling of blades by height is profiled according to the law of constant circulation. Based on the peculiarities of operation and operation of the turbocharger, it is proposed to make the wheel separately from the rotor shaft. The wheel is freely fitted on the shaft and pressed to the oil-reflecting bushing by a nut, which has a left thread, which prevents self-rotation of the nut during rotor rotation. To create tension in the threaded connection, it is supposed to use the heat fixation of the nut

3.2.2 Turbine

Due to the effect on the turbine of high temperatures (650-450° С), it is proposed to manufacture the turbine casing from wrought iron KP 32-

Inner part of housing is made in form of spiral single-chamber shaped cavity serving as channel for supply of exhaust gases to turbine. Slot diffuser is formed by central annular surface of housing and turbine screen

The outlet channel of the housing is diffuser. Outlet flange has four holes and is intended for attachment of the whole turbocharger. The rear wall of the diffuser is formed by a turbine screen, which is pressed when the turbine is attached to the bearing housing. The attachment is carried out by six bolts screwed into the turbine housing by three plates, as well as the compressor housing, the turbine housing is proposed to be made non-fixed

The turbine wheel is manufactured by precision vacuum casting from NAB-300 nickel alloy. Wheel has thirteen radial blades of parabolic profile with straight section near disk. Swirling of blades is profiled according to the law of constant circulation by height

For heat insulation of the compressor on the side of the turbine and on the side of the compressor, it is proposed to install special plates-screens that form air cavities with the bearing housing. In addition, on the side of the turbine between the screen and the housing, it is advisable to have a steel gasket

3.2.3 Lubrication of bearings

Lubrication of turbine compressor bearings is circulating under pressure from engine lubrication system. Oil is drained from turbocompressor to engine crankcase through branch pipes. Tightness of oil drain line connections is supposed to be provided by rubber sealing rings and paranite gaskets. Steel covers and oil shield (compressor side) are installed in the bearing housing, which together with sealing rings prevents oil leakage from the bearing cavity

3.3 Exhaust Exhaust

For normal operation of the proposed pressurizing system, it is necessary to ensure tightness of the cylinder head-turbocompressor section. Failure of outlet duct tightness leads to decrease of JI RPM. In this case, the amount of air injected into the cylinders decreases, the heat stress of the engine increases and its life is reduced

As a result, outlet manifolds are made solid-cast and are bolted to cylinder heads. To compensate for angular movements of the bolt head of the outlet manifold attachment arising during heating, it is proposed to install a special thermal insulation washer under the bolt head. Gas joints between the outlet manifold and the cylinder head, between the outlet manifold and the pulse converter, it is advisable to provide gaskets made of heat-resistant steel sheet. Tightness of joint between pulse converter and JI is provided by gasket

In the pulse converter, the pressure pulses are converted into kinetic energy, which communicates the entire mass of gases in the manifold, and then converted into pressure. Thus, the use of pulses occurs before the turbine. Pulse converters as well as outlet manifolds are cast from cast iron

5 Military-technical evaluation of the adopted constructive decisions

Work was carried out to determine the impact of pulsed gas turbine pressurization on the power and economic performance of the KamAZ engine

The supercharging of this engine allows a significant increase in economic performance, since the indicator specific fuel consumption equal to 0.1765 kg/( kWh) in the non-pressurized version decreased to 0.1187 kg/( kWh), but despite a decrease in the specific fuel consumption, an increase in the indicator cycle efficiency occurs. So from a value of 0.4797 cycle efficiency increases to 0.7133, which allows the engine to increase its power performance

Analysis of the parameters of the combustion process shows that during the installation of the pulsed gas turbine pressurization, the pressure in the combustion chamber increases due to a change in the angle of rotation of the crankshaft and the temperature decreases due to the rapid withdrawal of exhaust gases from the cylinders of the engine

The calculations and their assessment show that the pressurization of the KamAZ-740 engine leads to a significant increase in engine performance, which makes it possible to improve the engines currently in the RF Armed Forces

The use of pulsed gas turbine pressurization on the KamAZ-740 engine allows us to solve a number of features related to specific operating conditions of military automotive equipment. And also allows the engine to meet special requirements

In particular, the following indicators are being addressed:

- high power indicators that ensure the movement of the machine with the necessary speeds in difficult road conditions or off-road conditions under full loads;

- fast and trouble-free start in any climatic conditions at minimum time of output at nominal operating mode;

- high economy providing maximum range of vehicles and as low fuel consumption as possible;

- ability at least for a short time to operate on non-standard fuels (multi-fuel);

- low cost of specific fuel consumption;

Low toxicity and emissions;

- increased reliability and compactness;

- reduction of material consumption, weight, labour input of manufacturing and operation

These requirements can be met when pressurizing is used as a means of complex improvement of engine parameters

Conclusion

Improvement of internal combustion engines is carried out in the following areas: increase of economic indicators, increase of specific power, increase of reliability and increase of engine service life, reduction of smoke and toxicity of exhaust gases, provision of parametric stability in operating conditions, etc.

The use of military automotive equipment mainly falls on poor road conditions, or on off-road at maximum loads. All these factors give rise to certain specific requirements for the engines of these machines. To increase the power economic indicators on the engine of military automotive equipment, designers are working on the improvement, modernization and installation of additional and auxiliary installations, which make it possible to significantly increase these indicators

One such method is to install a pulsed gas turbine pressurization. The development of gas turbine supercharges began in the late 30s and to date, turbocharged automobile diesel engines for trucks have been brought to a greater degree of perfection

Based on the requirements for engines of military automotive equipment and the trend in the development of engine construction, an analysis was made of modern gas turbine pressurization systems, other systems that increase the power and economic performance of engines and the reasonable use of pulsed gas turbine pressurization

The project investigated the impact of pulsed gas turbine pressurization on the power and economic parameters of the KamAZ engine

Due to the fact that this engine is common among engines of military automotive equipment, an increase in its performance is a pressing problem at present

Calculations show that the installation of the proposed pulsed gas turbine pressurization system increases engine power from 170 kW to 190 kW, with an improvement in fuel economy to 136 g/kVt∙ch

The analysis provides the following conclusions:

- during development of pressurization for KamAZ-740 engine it is necessary to monitor the increase of operating stiffness, which may lead to early engine failure;

- the change in the temperature of the residual gases should be monitored, which can lead to heavy heating of the parts and the occurrence of ignition disturbance due to the appearance of scale;

- the investigated pulsed gas turbine pressurization allows to significantly increase the economic performance of the engine and allows the KamAZ-740 engine to meet the requirements for military automotive equipment for engines

Installation of the proposed system on the engine will slightly increase the amount of maintenance and will practically not complicate its operation

Operation of the advanced KamAZ-740 engine on military automotive equipment will significantly improve the combat qualities of military automotive equipment

Supercharging is now considered the most effective way to increase the power and improve the economy of diesel engines

Contents

Introduction........................................................................

8

1

Analysis of military-technical requirements for power plants of army vehicles.................................................................................................................................................................................

11

1.1

Main directions of engine power and economic performance increase.................................

15

1.2

Increase of engine operating volume.................................

18

1.3

Crankshaft speed increase.....................

19

1.4

Transition to two-stroke cycle.................................................................................................................................................

20

1.5

Increase of cycle charge weight due to pressurization...............

21

1.6

Application of new materials.................................................................................................................................................................

24

2

Design analysis of modern gas turbine pressurization systems.............................................................................................................................................................

27

2.1

Isobaric pressurization system.....................................................................................................................

27

2.2

Pulsed pressurization system.............................................................................................................................................

29

2.3

Two-stage gas turbine pressurization system with intermediate cooling of supercharging air...............

30

2.4

"Giperbar" system.................................................................................................................................................................................................................................................................

32

2.5

Variable geometry compressor..................................

34

2.6

Electrically driven turbocompressor.................................................................................................................

37

2.7

Pressurizing of "Comprax" type.........................................................................................................................

37

2.8

Valvetronic system...........................................................

41

3

Substantiation of design solutions of KamAZ-740 engine gas turbine pressurization.............................................................................................................................................................................

43

3.1

Design diagrams of turbocompressors.....................................................................................

43

3.1.1

Turbocompressors with supports at rotor ends.....................

45

3.1.2

Turbocompressors with supports between impellers..........

47

3.1.3

Turbocompressors with arrangement of compressor wheel and turbine on one side from rotor supports...............................................................................................................................................................................................................................................................................................................................................................................................................

52

3.1.4

Turbocompressors with rotor supports on both sides of the turbine...........................................................................................................................................................................................................................................................................................................................................................................................................................................

52

3.1.5

Turbocompressors with rotor supports on both sides of compressor wheel..............................................................

53

3.2

Peculiarities of TKR7N turbocharger device................

54

3.2.1

Compressor.........................................................................

55

3.2.2

Turbine..............................................................................

56

3.2.3

Lubrication of bearings.........................................................

57

3.3

Exhaust gas exhaust.............................................................................................

57

3.4

Engine air supply system.................................................................................................................................................................

58

3.5

Thermal calculation.................................................................................................

66

4

Military-technical evaluation of the adopted design solutions.....................................................................................................................................................

84

Conclusion.....................................................................................................................................

86

Appendix A

Appendix B