RELATED REGULATION OF BIOGAS SUPPLIES AND METHANE IN A GAS ENGINE

The results of experimental researches were received on a gas-electric installation with a rated power of 30 kW at 1500 rpm. The spark-ignited petrol drive engine (8-cylinder, 100 mm cylinder diameter, 88 mm stroke) was converted to a pure gas one. The compression ratio of 8.5 did not change. The gas fuel supply system consists of a supply line and an emergency shut-off circuit. The natural gas supply line was connected to the domestic main line through a special gas distributor. On the basis of HEINZMANN components, a system for dosing mixed gas fuel was developed, which, through a microprocessor control unit and an actuator, acted on the throttle valve of the gas mixer. In experimental researches, the composite fuel was a model gas – a mixture of natural and carbon dioxide gases, which was prepared in a zero pressure reducer before the gas mixer. With an increase in the volume fraction of carbon dioxide in the model gas by more than 34 %, a deterioration of the combustion process was observed in the steady state. In the article, based on the analysis of the experimental results of the operation of a piston gas engine on a model gas, an algorithm for the use of associated automatic control of biogas and methane feeds is substantiated. The transition from quantitative to qualitative regulation of the gas-air mixture has been substantiated. To do this, it is necessary to create two automatic control loops for the supply of air and a mixture of natural gas, which are interconnected through an external load. With the developed algorithm, as the load increases, the supply of natural gas increases, and the supply of biogas decreases. With an increase in the load of 75 % or more, a more intensive enrichment of the fuel mixture with natural gas occurs than at low and medium loads. The proposed algorithm for regulating the fuel mixture can be implemented using electromagnetic gas injectors for dosing the components of the composite fuel. Signals from sensors for oxygen and methane content in exhaust gases were selected as corrective links for the coupled control algorithm. Recommendations on the choice of tuning modes for oxygen and methane sensors have been developed.

MATHEMATICAL MODELING OF THE ENGINE PARAMETERS INFLUENCE ON VEHICLE ACCELERATION DYNAMICS

The throttle response of a vehicle determines its dynamic properties and is characterized by an acceleration time from 0 to 100 km/h. An experimental study of the influence of vehicle parameters on its throttle response is associated with significant material and labor costs. At the stage of sketching the design of the vehicle, preliminary determination of design parameters and settings, it is rational to use mathematical models. In the existing models of the vehicles movement dynamics, the engine power, as a rule, is set by empirical dependencies and does not take into account the possibility of changing its parameters and characteristics. The paper proposes a mathematical model that combines models of the engine workflow and the dynamics of vehicle acceleration. The mathematical model of the engine workflow is a quasi-stationary thermodynamic model, in which combustion is described by the Vibe equation, and heat transfer with the walls is described by the Woschni equation. To check its adequacy, an experimental study of the VAZ-2108 engine was carried out to obtain external speed, load and control characteristics. Good agreement between the calculated and experimental data is shown. Vehicle acceleration simulation was carried out according to the method of E.A. Chudakov. The parameters of the VAZ-2108 car and the resistance forces during acceleration from 0 to 100 km / h have been determined. It is shown that the car accelerates from 0 to 100 km / h in 18.3 s, which corresponds to the experimental data and indicates the adequacy of the chosen techniques. The influence of changing the parameters and settings of the engine on the dynamics of vehicle acceleration has been investigated. It is shown that in order to achieve better dynamics of motion, the cylinder diameter and compression ratio must be maximized. The ignition timing, intake valve closing angle and excess air ratio have extremes. The efficiency of using a 16-valve cylinder head instead of an 8-valve one is shown. Based on the results of the studies, it was proposed to apply a set of engine parameters, which made it possible to reduce the acceleration time of the VAZ-2108 from 18.3 s to 13.2 s. Thus, the developed mathematical model makes it possible to quantitatively evaluate the influence of engine parameters on the dynamics of vehicle acceleration, to optimize the parameters and settings of the power plant and the vehicle as a whole.

FRENCH ENGINEER SABATHE LOUIS GASTON AND HIS ROLE IN CREATION OF DUAL COMBUSTION CYCLE

Almost immediately after Rudolph Diesel created his "rational" engine, attempts were made to improve it. Since at the end of the nineteenth and the beginning of the twentieth century, the theory of internal combustion engines had not yet been formed as a unified scientific system, there were no unified approaches to assessing the innovations proposed by individual engineers and scientists either. In this regard, disputes and litigations periodically arose related to the recognition of priority for a specific design or the proposed principle of work for a specific author. First of all, this was due to the possibility of obtaining material benefits from the introduction of a patented innovation into production. It should be noted that profit-related litigation and information campaigns were not always objective, and the development of progress at the turn of the century were so rapid that the same ideas entered the heads of several independent inventors at once, but the same discoveries were made in different parts of the world by different scientists. By the beginning of the twentieth century, the accumulated experience, as well as theoretical and experimental studies have shown that it was possible to significantly improve the nature of the flow of the working process of piston engines by replacing the isochoric or isobaric heat supply in the process of fuel combustion with a combined one with heat supply, first at a constant volume (by isochore), and then at constant pressure (isobar). Three scientists - Gustav Trinkler, Myron Zaliger and Louis Gaston Sabathe claimed priority in the development of such a cycle. Each of them came to this decision in different ways, and each made his own contribution both to the formation of the theory of working processes of piston engines, and to the formation of engine building in general. It is to this contribution made by the French engineer Louis Gaston Sabathe that this article is devoted.

INFLUENCE ON PISTON ENGINE PERFORMANCE BY THE BIOCOMPONENTS AND DIFFERENT TYPES OF NANO MATERIALS

The obviousness of the finiteness of the planet's energy resources makes us constantly concern ourselves with the search for new energy sources and their rational use. The main energy converter is the internal combustion engine and contrary to forecasts, continues to occupy a leading position. Therefore, the issues of improving its working processes, reducing the consumption of mineral fuel, the possibility of using all kinds of alternative fuels and improving the quality of motor fuel continue to be considered throughout the energy world. On the agenda is the dissemination of advances in nanotechnology to the propulsion industry. Improvement of engine performance when using fuel dispersed with nanomaterials of various types is beyond doubt and is used both for pure petroleum and biodiesel and for their mixtures. In the article, against the background of the analysis of studies on the use of alternative biofuels and the introduction of the practice of introducing nanoparticles into petroleum fuel and biofuels as a potential energy carrier to improve the characteristics of toxicity and engine performance, the results of studies of a number of biofuels have been presented. Presented are the results of a study of the performance of a 1Ch 8.5 / 11 diesel engine carried out in the laboratory of IPMash NAS of Ukraine when operating on diesel fuel dispersed with carbon spheroidal nanoadditives of various concentrations, and some comparative results of studies of the indicators of diesel engines with direct injection 2Ch 10.5 / 12 and 4ChN 7.9 / 7.5 ALH, operating on standard and mixed fuels with biocomponents synthesized from rapeseed, sunflower, mustard and corn oils. The thermophysical properties of the fuel (heat of combustion, thermal conductivity, heat capacity, density, kinematic viscosity, convective heat transfer, ignition temperature, cetane number, etc.) undergo significant changes when nanoparticles are introduced into it. The optimal amount of metal nanoparticles, metal oxides, carbon tubes, graphene in mineral, biodiesel or mixed fuel promotes more complete combustion, significantly improves engine performance, and reduces harmful emissions.

DETERMINATION OF COMPLEX FUEL-ECOLOGICAL CRITERION FOR DIESEL WORKING ON WATER-FUEL EMULSION

Today, internal combustion engines are very common as energy sources in many countries around the world. This makes the tasks related to improving the environmental performance of internal combustion engines relevant. The introduction of alternative fuels in internal combustion engines is an effective way to reduce their negative impact on the environment. One of the most available and widespread alternative fuels for diesels is a water-fuel emulsion. The use of water-fuel emulsion makes it possible to reduce the specific fuel consumption of petroleum origin, as well as to achieve a significant reduction in emissions of harmful substances from diesel exhaust. However, due to differences in the physical properties of traditional diesel fuel and water-fuel emulsion, the course of the processes of mixture formation and combustion in the diesel cylinder changes significantly. This may be due to the emergence of a reserve for further improvement of the diesel engine by selecting the parameters of the diesel engine running on water-fuel emulsion. The study selected the following parameters for variation: compression ratio, boost pressure, duration of the injection process, injection timing. The article considers the influence of these parameters on the Brake-specific fuel consumption of diesel, the specific emission of particulate matter and nitrogen oxides, the maximum pressure in the cylinder. The nature and degree of influence of changes in the parameters of the diesel engine on its performance was determined using mathematical modeling. It should be noted that the influence of each of the parameters selected for variation is quite complex and often ambiguous. That is, when some indicators improve, others may deteriorate somewhat. Therefore, in order to select the most rational parameters of a diesel engine running on a water-fuel emulsion, it is necessary to simultaneously assess the economic and environmental performance of the diesel engine. For this assessment, a method was used to determine a comprehensive fuel and environmental criterion for a diesel engine running on a water-fuel emulsion. Thus, the article shows the potential for comprehensive improvement of environmental and economic performance of the diesel engine by choosing rational parameters.

CONTACT INTERACTION OF DISCRETE-CONTINUALLY STRENGTHENED PARTS OF INTERNAL COMBUSTION ENGINES

Studies of the stress-strain state of discrete-continuously strengthening parts of internal combustion engines are described in the paper. A parametric model of a microcell containing a two-part cell has been developed. The first part simulates a fragment of an aluminum part with a surface corundum layer. The second part is a fragment of a cast iron part with a zone of discrete strengthening of steel. Vary: modulus of elasticity of the corundum layer material and the shape of the discrete hardening zone. The dependences of the strength and stiffness characteristics of the studied system on the varied parameters are established. They are the basis for substantiation of rational modes of technology of discrete-continuous strengthening of parts of internal combustion engines. In the course of research, it was found that previously determined for discrete strengthening, the effects of a favourable redistribution of contact interaction between parts are preserved for discrete-continuous strengthening. The characteristic dependences of the features of the stress-strain state of the elements of discrete-continuously strengthening parts on the varied properties of the surface layers of the continuously strengthened part, on the one hand, and the shape of the discrete strengthening zone, on the other, are determined. This makes it possible to determine the sensitivity of the characteristics to purposeful or random variation of these factors. It is also expedient to set and solve optimization problems to determine such modes of technological operation of discrete-continuous strengthening, which increase the characteristics of strength, durability, efficiency of internal combustion engines and other machines, units and assemblies containing such strengthened parts. The developed approach, models and research methods will be further applied to studies of the stress-strain state of contacting discrete-continuously strengthened parts of structures to improve the technical and tactical and technical characteristics of products of machine-building enterprises.

SIMULATION OF OPERATION OF THE AUTOMATED SYSTEM OF LOCAL MULTI-CIRCUIT COOLING OF PARTS OF AUTOTRACTOR DIESEL ENGINE

The results present the intermediate stage of the study of the thermal state of individual heat-stressed parts and units of a forced tractor diesel engine in the conditions of their local air cooling (LAC), which is regulated in automatic mode. Possibilities of practical implementation on the basis of microprocessor control systems of multi-circuit local cooling of parts of valve exhaust unit, bearing unit of turbocharger, if necessary, additional air cooling of the upper part of cylinder blocks in the area of cylinder liners are considered and evaluated. The listed parts, as evidenced by the results of many engine tests, differing in the values of the maximum critical temperatures, which in turn depend on the course of heat exchange processes in the corresponding interfaces, nodes. At the same time, in the conditions of operation with the use of the LAC system on the diesel engine there are additional problems associated with the complication of the cooling control algorithm, the need to move to multi-circuit options with their critical temperature values and required cooling air costs. At this stage of the study, a test was performed in the test mode of the algorithm for supply control and shutdown of the coolant supply, the corresponding circuit solutions for its implementation. In the engineless experiment, previously specially designed and thermocoupled units were used, which were heated separately with the set test temperatures, as well as a series-produced unit, which is part of the 4th generation gas cylinder equipment (GCE) of modern engines. The unit consists of four sections with solenoid valves, which dose the gas supply to the injectors according to a given algorithm (Valtek type 30). At the input of the engineless experiment, this unit was used to turn on and off the supply of compressed cooling air in separate circuits (from 2 to 4). The moments of operation of the valves (opening-closing) corresponded to the set test temperatures. In addition to the dynamics of temperature changes at the control points of the research units during the cooling process, the pressure, temperature, and coolant flow rates on individual circuits were also monitored. The conducted engineless experiment confirmed the correctness of the adopted circuit solutions, and also proves the possibility of further application of serial GCE units in LAC systems.

USE OF VEGETABLE OIL AS A FUEL IN A MEDIUM SPEED DIESEL ENGINE

While being highly fuel-efficient, diesel engines are defined by relatively high emissions, which have a negative impact on people and the environment. In the future, most European countries plan to abandon the use of diesel engines after 2030. One way to use this type of engines is to convert them to alternative fuels from renewable energy sources, such as vegetable oils (rapeseed, sunflower and soya bean oils). A significant advantage of vegetable oils is that when they hit the ground, they break down in a couple of weeks. Sulfur oxides are virtually absent due to the small amount of sulfur in vegetable oils in the engine exhaust gases. Other environmental factors include reduced emissions of nitrogen oxides NOx, carbon monoxide CO, unburned hydrocarbons and carbon black C. However, it should be noted that the use of vegetable-based fuel involves problems related to fuel preparation, consideration of physical and chemical properties and proper engine operation and use of arable land for the cultivation of vegetable oils. The article presents the results of experimental studies to determine the effective performance of soybean oil, six cylinder, four-stroke supercharged diesel engine (26 – the diameter of the cylinder, cm; 34 – the piston stroke, cm) produced by "Pervomaiskdieselmash", which is a part of the stationary diesel generator (DGA-900) with the capacity of 900 kW. This diesel engine is with an undivided combustion chamber ("Geselman" type), gas turbine supercharging and intermediate charge air cooling. Soybean oil is more viscous and has better lubrication properties of conjugated vapors and engine components, as a result, the lifespan of the engine and high-pressure fuel pump increases by an average of 60%. However, more viscous soybean oil impairs fuel mixing, spraying and combustion. Starting qualities of the engine also deteriorate. On the other hand, as the temperature rises, the viscosity of soybean oil decreases sharply. The reasons which led to the emergence of the above-mentioned problems have been analysed. In addition, the features and advantages of the cogeneration power plant have been described, which makes it possible to obtain two forms of useful energy at the output such as thermal and electric. The use of cogeneration significantly increases the overall efficiency of the plant; it provides significant opportunities for efficient heat utilization and achieving maximum economic effect.

CENTRIFUGAL COMPRESSOR PERFORMANCE MAPS TREATMENT FOR INTERNAL COMBUSTION ENGINES OPERATING CYCLE SIMULATION

Simulation of the supercharged internal combustion engines operation cycle is impossible without correct estimation of the supercharger operating parameters. Standard approach is to use specially prepared performance maps of compressor and turbine of the turbocharger, which are based on the experimental (or manufacturer’s) raw data. Centrifugal compressor performance maps interpolation, extrapolation and treatment provides challenging requirements as it is important to get correct simulation under such special conditions as compressor choke, rotating stall and pumping surge. At the same time it’s important to obtain the fast and stable calculations of the engine’s operating cycle. Blitz-PRO – online internal combustion engines operating cycle simulation service – offers supercharger performance maps preprocessing and implementation. It provides three different modes of compressor surge consideration during calculations: 1) full-scale surge mode using Moore-Greitzer approach; 2) mild surge mode with flexible adjustment; 3) “stable” mode, when the surge is neglected and the compressor constant-speed lines are extended from the rotating stall point to the lower mass flow region with the hyperbolic equation. Using the MAN 8G70ME-E engine 12140 kW, 82 rpm operating point as an example, the calculation results are compared for three modes of compressor surge consideration. The “stable” mode provides the fastest and the most stable calculations, while the calculations under the full-scale surge mode could generate the numerical (nonphysical) instability of calculations, which are caused by the high sensitivity of the two-stroke engines to the gas exchange processes as it is shown. The mild surge mode provides fast and stable enough calculation with the surge consideration ability, which could be assumed as the best solution for the given example. The researcher should choose between provided three modes of the centrifugal compressor surge consideration according to the calculations tasks, preferring “stable” mode for initial model setup and mild surge mode for the surge probability check, while the accurate compressor surge simulation needs further development.

COMPARISON OF COMBUSTION INDICATORS OF TWO-STROKE ENGINES WITH A CARBURETOR AND DIRECT FUEL INJECTION

The subject matter of study in the article is the indicators of the combustion process of a two-stroke engine 1D 8.7 / 8.2 with spark ignition when using a carburetor power supply system (external mixture formation) and a direct fuel injection system (internal mixture formation). Internal mixture formation ensures the organization of a stratified fuel-air charge (SFAC) and a stratified lean fuel-air charge (SLFAC). Combustion indicators allow you to assess the nature of the combustion process. The goal is to determine the nature of the change in the combustion indicators of the engine with external and internal mixture formation during the organization of the working process with the SFAC and SLFAC at the load characteristic modes (n = 3,000 rpm). The tasks to be solved are as follows. The use of internal mixture formation and the organization of the combustion of SLFAC and SFAC made it possible to obtain values of ηi greater than with external mixture formation at all modes of the load characteristic. The maximum value of ηi for SLFAC is 0.5 at a load bmep = 0.2 MPa, for SFAC – 0.44 at bmep = 0.25 MPa and 0.3 at bmep = 0.36 MPa for an engine with a carburettor. Maximum combustion pressure (рz), pressure increase ratio (λ), preliminary expansion ratio (ρ), further expansion ratio (δ), combustion character indicator (m), maximum heat release rate (dx / dfi max), duration of combustion from TDC to point Z (φz), total duration of combustion (dφz); to construct the characteristics of changes in combustion indicators and to obtain empirical dependences depending on the engine load. An experimental-analytical research method is used, which provides for the determination of the nature and analysis of the course of the combustion process according to the combustion indicators established by the experimental indicator diagrams. The following results were obtained. The use of internal mixture formation and the organization of the combustion of SFAC and SLFAC made it possible to obtain ηi values greater than with external mixture formation at all modes of the load characteristic. The maximum value of ηi for SLFAC is 0.5 at a load ре = 0.2 MPa, for SFAC - 0.44 at ре = 0.25 MPa and 0.3 at ре = 0.36 MPa for an engine with a carburetor. The pressure in the cylinder with the piston position at TDC is on average 1.5 times higher for an engine with a carburetor, and the maximum combustion pressure рz is higher up to 11 % with the organization of SLFAC (the degree of pressure increase λ is reduced by 26 %) and 20-22 % higher than in the organization of SFAC (the value of λ is reduced by 31 %). An increase in the compression ratio ε by 26.4 % and a decrease in the degree of preliminary expansion ρ at SLFAC in comparison with SFAC made it possible to increase the degree of further expansion δ by an average of 30 % and by 43 % in comparison with the carburetor power system. When organizing SLFAC, the value of the indicator of the nature of combustion m is, on average, 1.4 times higher than that of an engine with a carburetor and 1.45 times higher relative to the organization of SFAC, at which the maximum rate of heat release dx / dfi max is up to 40 % higher than in the engine with carburetor. The SLFAC organization allowed reduce the combustion duration by 39 % relative to external mixture formation and by 36 % relative to the SFAC organization. Conclusions. The scientific novelty of the results obtained consists in obtaining data and empirical dependences of the indicators of the combustion process of the 1D 8.7 / 8.2 engine with external and internal mixture formation with the organization of SFAC and SLFAC at load characteristic modes (n = 3,000 rpm). It was found that the best technical, economic and environmental indicators correspond to the organization of internal mixing with SLFAC.