Working Process Of Engine Research Articles

The improvement in the methods for estimating the nature of the working process of an internal combusting

The urgency of mathematical simulation and electronic processing of obtained experimental data for estimating the working process increases by the day. The solution of real-world problems requires high-speed computer programs that enable us to reliably simulate complex processes occurring in engines and to simplify a considerable part of research effort. In connection with these considerations, the aim of our investigation is the improvement in the methods for estimating the nature of the working process of an internal combustion engine by applying CNIDI techniques for processing indicator diagrams by designing a hardware and software package. The package is able to present the obtained design data of heat-generation law values in a readable form of a digital model that enables us to produce their subsequent export into other software products for further research. The novelty of our work lies in developing a program for personal computers which is able to process experimental indicator diagram obtained in any form and by any technique for acquisition of heat-generation values. The main purposes of our investigation are the analysis of existing CNIDI techniques of processing indicator diagrams, the algorithm design of computer software operation and the verification of data obtained by programmed methods with design data. We found that applying the technique of processing experimental indicator diagrams is one of the methods most reliably describing the processes occurring in diesel cylinders. We analyzed the theoretical basics of a fuel combustion process by using experimental indicator diagrams, examined taking into account imprecision of source data, and validated ways of updating the data. We upgraded the computer program aimed at the methods of heat-generation data calculation under combustion according to specified diagrams. The use of introduced CNIDI techniques and the appropriate program of indicator diagram analysis provide the required quality of results in investigating the influence of various factors on fuel combustion process in an engine.

Evaluation and sensitivity analysis of a piston’s thermal load in a high-power diesel engine

Optimising the parameters of valve timing and fuel system can promote the applications of high-power diesel engines that have high efficiency and low emissions. Nevertheless, the problem of the piston’s thermal load needs to be considered. In this paper, a calculation model for the working process of a high-power diesel engine and a finite element model of the piston’s thermal load were established. The piston’s thermal boundary conditions were determined and applied to the calculation of the piston’s thermal load, and the key temperature points of the piston were measured using the temperature plug method to verify the correctness of the model. Subsequently, analysis of the patterns of the piston’s thermal load’s evaluation parameters was carried out with the influencing factors based on the valve timing and the fuel system. The sensitivity and the weighting between the evaluation parameters and influencing factors were analysed using the Grey Correlation method. A new method for the comprehensive evaluation index of the piston’s thermal load with the influencing factors was proposed and applied. The research results show that the margin of error of the piston’s thermal load’s model was small, and sensitivity analysis revealed correlation between the influencing factors and the evaluation parameters of the piston’s thermal load, the comprehensive evaluation method could quantitatively analyse the piston’s thermal load.

Petrol engine workflow model for researching unconventional engines

The work lies with the study of petrol engines of an unconventional design with improved fuel and economic characteristics developed at the Automobile and Road Institute of Donetsk National Technical University for several decades. It describes the obtained mathematical model of the working process of a petrol piston engine to study the operation of engines. The authors used analytical methods of differential calculus to obtain a mathematical model. They solved the obtained equations using numerical methods and Simulink algorithms. Implementation required the development of a model that has sufficient speed to complete the tasks. The paper presents some modelling results, which makes it possible to judge the correctness of the obtained model. The implemented approach makes it possible to use this model in multi-domain modelling of the engine as a whole. The use of such a model opens up broad prospects for optimizing engine parameters, both its mechanical elements and the parameters of the working process. In addition, it becomes possible to develop and debug a control system for a petrol internal combustion engine using simulation in a Simulink environment.

Investigating the combustion stability of shale gas engines under HHO

Brown gas (HHO) contains H2 and O2, as well as a small amount of active oxygen radical hydroxyl (·OH), which not only promotes the flame propagation process, but also affects the stability of the shale gas engine combustion process. In this paper, we investigate the combustion stability of shale gas engines by adjusting the HHO blending ratio. In particular, the influence of HHO content on the in-cylinder pressure and heat release process of a shale gas engine is analyzed, the combustion cycle trends are discussed, and the dynamic characteristics of the combustion process are evaluated. The influence of HHO content on the stability of the flame propagation process in the cylinder is then determined. Results demonstrate that the in-cylinder pressure increases, heat release rate and the engine combustion stability increase with the HHO blending ratios, while the average indicated pressure distribution range, and pressure coefficient of variation in the combustion phase decrease. Furthermore, the increase in HHO content leads to the gradual tightening of the reconstructed phase space trajectory distribution, improves the periodicity of the engine working process, enchances the certainty of the front and back cycles in the combustion process, and improves the stability of the engine working process. Moreover, an increase in the HHO content enhances the cylinder heat release rate, the combustion temperature, the temperature distribution area, the fire core radius, the peak flame surface density, and the flame propagation.

Research on the hydrogen injection strategy of a direct injection natural gas/hydrogen rotary engine considering apex seal leakage

The purpose of the present paper is to investigate the hydrogen injection strategy on the combustion performance of a natural gas/hydrogen rotary engine. Considering that apex seal leakage (ASL) is an inevitable problem in the actual working process of a rotary engine, the action of ASL cannot be ignored for an in-depth study of its combustion performance. Therefore, in this paper, a 3D dynamic simulation model that put the effect of ASL into consideration was established. Furthermore, based on the established 3D model, the combustion process of a natural gas/hydrogen rotary engine under various hydrogen injection angle (HIA) and hydrogen injection timing (HIT) was investigated. The results indicated that the hydrogen jet flow first impacted on the rotor wall after entering the cylinder, and then diffused under the action of the vortexes in the cylinder. Therefore, the HIA and HIT could change the hydrogen distribution by changing the hydrogen impact location and the intensities of the vortexes in the cylinder. In addition, the ideal hydrogen distribution at the ignition timing which could improve the combustion efficiency was given. That is, under the premise of ensuring minimized hydrogen leakage, the hydrogen should mainly distribute in the middle and the front of the cylinder, and a high hydrogen concentration is maintained near the spark plug.

Investigation of the environmental characteristics of a diesel engine when operating on activated fuel

The internal combustion engine is the most widespread source of energy for vehicles. The main requirements for an internal combustion engine include: the efficiency of functioning as part of a vehicle, high performance indicators, as well as environmental parameters of the emission of exhaust gases into the environment. The fulfillment of these conditions is possible by improving the design of the engine, as well as improving the working process of the diesel engine while increasing the quality of diesel fuel or additional impact directly on the fuel itself. One of the most effective ways to influence diesel fuel is to transfer a certain amount of heat to it in the high-pressure fuel line in front of the injectors. At the same time, the physical and mechanical properties of diesel fuel change, which leads to a change in mixture formation and the combustion process in the engine cylinder. To intensify the combustion process, a method of preliminary high-temperature local heating of diesel fuel in the fuel supply system in front of the injectors was proposed. To achieve this goal, several main directions were identified, including the study of environmental indicators during the intensification of the combustion process. The tests were carried out in stages. At the first stage, the operation of the fuel injector when operating on activated fuel (bench, laboratory tests) was investigated. At the next stage, the indicators of the diesel engine in the main modes of its operation were investigated. Bench (laboratory) tests made it possible to draw a conclusion about the operability and compliance of the aggregate with the technical requirements of the manufacturer and the parameters of GOST. The bench tests proved the possibility of a diesel engine running on activated fuel without deteriorating environmental performance in the exhaust gases; at the same time, changes in the toxicity and smoke of the exhaust gases from different values of the average effective pressure were revealed.

Features of the working process of high-speed diesel engines

This article discusses the main history of the creation of high-speed short-stroke diesel engines and an assessment of the main factors that most significantly affect the working process of a diesel engine. When developing a new design of a high-speed diesel engine, it is necessary to pay special attention to the following factors: the intensity of the air charge, injection pressure parameters, the shape of the combustion chamber and the choice of the best option. Research carried out with a 7 x 0.15 mm nozzle in a wide range of speed changes (n = 1000 + 2800 min-1) shows that it is possible to find a position of the widened valve at which optimal results are obtained at medium and high rotational speeds, and on small - engine performance will deteriorate slightly.

The effect of heat recovery on the optimal values of helicopter turboshaft engine parameters

Recent studies related to fuel economy in air transport conducted in our country and abroad show that the use of recuperative heat exchangers in aviation gas turbine engines can significantly, by up to 20...30%, reduce fuel consumption. Until recently, the use of cycles with heat recovery in aircraft gas turbine engines was restrained by a significant increase in the mass of the power plant due to the installation of a heat exchanger. Currently, there is a technological opportunity to create compact, light, high-efficiency heat exchangers for use on aircraft without compromising their performance. An important target in the design of engines with heat recovery is to select the parameters of the working process that provide maximum efficiency of the aircraft system. The article focused on setting of the optimization problem and the choice of rational parameters of the thermodynamic cycle parameters of a gas turbine engine with a recuperative heat exchanger. On the basis of the developed method of multi-criteria optimization the optimization of thermodynamic cycle parameters of a helicopter gas turbine engine with a ANSAT recuperative heat exchanger was carried out by means of numerical simulations according to such criteria as the total weight of the engine and fuel required for the flight, the specific fuel consumption of the aircraft for a ton- kilometer of the payload. The results of the optimization are presented in the article. The calculation of engine efficiency indicators was carried out on the basis of modeling the flight cycle of the helicopter, taking into account its aerodynamic characteristics. The developed mathematical model for calculating the mass of a compact heat exchanger, designed to solve optimization problems at the stage of conceptual design of the engine and simulation of the transport helicopter flight cycle is presented. The developed methods and models are implemented in the ASTRA program. It is shown that optimal parameters of the working process of a gas turbine engine with a free turbine and a recuperative heat exchanger depend significantly on the heat exchanger effectiveness. The possibility of increasing the efficiency of the engine due to heat regeneration is also shown.

Improving the efficiency of aviation turbofan engines by using an intercooler and a recuperative heat exchanger

Continuous improvement of fuel efficiency of aircraft engines is the main global trend in modern engine construction. To date, aviation gas turbine engines have reached a high degree of thermodynamic and design-and technology perfection. One of the promising ways to further improve their fuel efficiency is the use of complex thermodynamic cycles with turbine exhaust heat regeneration and with intermediate cooling in the process of air compression. Until recently, the use of cycles with a recuperative heat exchanger and an intercooler in aircraft gas turbine engines was restrained by a significant increase in the mass of the power plant due to the installation of heat exchangers. Currently, it has become technologically possible to create compact, light, high-efficiency heat exchangers for use on aircraft without compromising their performance. An important target in the design of engines with heat recovery is to select the parameters of the working process that provide maximum efficiency of the aircraft system. The article focuses on the statement of the task of optimization and choice of rational parameters of the working process of a bypass three-shaft turbojet engine with an intercooler and a recuperative heat exchanger. On the basis of the developed method multi-criteria optimization was carried out by means of numerical simulations. The results of optimization of thermodynamic cycle parameters of a bypass three-shaft turbojet engine with an intercooler and a recuperative heat exchanger in the aircraft system according to such criteria as the total weight of the engine and fuel required for the flight, and the aircraft specific fuel consumption per ton - kilometer of the payload are presented. A passenger aircraft of the Airbus A310-300 type was selected. The developed mathematical model for calculating the mass of a compact heat exchanger, designed to solve optimization problems at the stage of conceptual design of the engine is presented. The developed methods and models are implemented in the ASTRA program. The possibility of improving the efficiency of turbofan engines due to the use of complex thermodynamic cycles is shown.

ОСОБЕННОСТИ РАСЧЕТА И РЕГУЛИРОВАНИЯ ДВУХКОНТУРНОГО ТУРБОРЕАКТИВНОГО ДВИГАТЕЛЯ С ФОРСАЖНОЙ КАМЕРОЙ СГОРАНИЯ В НАРУЖНОМ КОНТУРЕ НА ПРЯМОТОЧНЫХ РЕЖИМАХ РАБОТЫ

A promising direction in aviation is the creation of anaircraft for supersonic cruise speeds (Mach 3...4). It is known that ramjet engines are more preferable for Mach numbers larger 3. However, they do not have starting thrust and uneconomical at subsonic flight speeds. At the same time, at subsonic flight speeds, turbofan engines are the most expedient. The combination of the positive properties of turbofan engines at subsonic speeds and a ramjet engines at supersonic speeds is possible by using duct-burning turbofan engine, which can operate at the ramjet mode with the blocked gas turbine duct at supersonic flight conditions. At this mode, duct-burning turbofan engine turns into ramjet engine, which, however, has special features due to the presence of fan in front of the combustion chamber, which operates in turbine mode or in zero power mode and also because of the outlet jet, which has annular shape, flows out from the duct causes the appearance of bottom drag. The presence of bottom drag requires both the development of a mathematical model for its calculation and taking into account its influence on the choice of the control law for the nozzle outlet area. The article presents a mathematical model of the working process of duct-burning turbofan engine at ramjet mode, taking into account the presence of fan in the flow path and bottom drug. Using the developed mathematical model, the regularities of changes in the internal and effective thrust, as well as the specific fuel consumption, depending on the relative fuel consumption and the critical section of the nozzle at a given altitude and flight speed are established. The critical section of the nozzle is the main regulating factor, and the relative fuel consumption is related to the main regulating factor - the fuel consumption. These patterns are useful for choosing a control program.There is such a combination of regulating factors whichprovides two extremes in the regularities of trust and specific fuel consumption changes: the mode of minimum specific fuel consumption and the mode of maximum thrust. In addition, the influence of gas underexpansion in the nozzle on the thrust-economic parameters of the engine and the required area of the nozzle outlet section were estimated. The obtained regularities are advisable to use when engine control program is chosen.

Исследование рабочего процесса дизеля при работе на безводном топливе, грубой и микрогетерогенной водотопливной эмульсии

Оксиды азота являются наиболее опасными химическими соединениями, находящимися в составе отработавших газов судовых дизелей. Уменьшение содержания оксидов азота является весьма сложной задачей, так как это связано с ограничениями максимальной температуры цикла, термического КПД и, следовательно, с ограничениями по топливной экономичности. Одним из эффективных способов уменьшения концентрации оксидов азота является применение водотопливных эмульсий. Недостатком применения эмульсии является увеличение удельного расхода топлива. Целью работы является исследование возможности одновременного снижения уровня вредных выбросов и расхода топлива при работе дизеля на ВТЭ. В статье приведены описание экспериментальной установки и результаты экспериментальных исследований дизеля Ч10,5/12 на безводном топливе, грубой и микрогетерогенной водотопливных эмульсий с содержанием воды 15% при работе по винтовой характеристике. С использование полученных в ходе испытаний дизеля индикаторных диаграмм выполнен сравнительный анализ рабочего процесса на различных топливах. Полученные результаты выполненных исследований подтвердили эффективность использования микрогетерогенной эмульсии, в сравнении с грубой эмульсией для снижения выбросов оксидов азота с отработавшими газами в судовых дизельных энергетических установках и уменьшения удельного расхода топлива. Nitrogen oxides are the most dangerous chemical compounds which come out with the exhaust gases of marine diesel engines. Reducing nitrogen oxides is challenging due to limitations on maximum cycle temperature, thermal efficiency, and hence fuel economy limitations. One of the effective ways to reduce the concentration of nitrogen oxides is the use of water-fuel emulsions. The disadvantage of using an emulsion is the significant fuel consumption increase. This article describes the experimental setup and the results of experimental studies of a Ч10.5/12 diesel engine on anhydrous fuel, coarse and micro-heterogeneous water-fuel emulsions with a water content of 15% when operating in service. Performance diagrams obtained during the diesel engine tests let the authors get a comparative analysis of the working process using various fuels. The results confirmed the effectiveness of using a micro-heterogeneous emulsion, in comparison with a coarse emulsion, to reduce emissions of nitrogen oxides with exhaust gases in marine propulsion systems and to reduce fuel consumption.

The algorithm for determining the effect on the dynamic characteristics of the fuel composition on the properties of the working process of the gas-diesel engine

The article deals with the method of determining the optimal composition of the components of the combined fuel taking into account the heat-dynamic tension in the operation of the diesel engine on a mixture of diesel fuel and natural gas, i.e. the gas-diesel cycle. The calculation was based on the method developed by A. V. Grinevetsky and M. N. Mezingom, taking into account the specific conditions of the diesel engine on a mixture of natural gas and diesel fuel. The peculiarity of the mathematical model is that the optimal composition of the fuel components is initially unknown and is indicated as an array. The search for the optimal ratio of fuel components will take into account the heat and Dynamo tension. The resulting model can be used in the study of the diesel engine on other alternative fuels. Thus, it is possible to significantly improve the quality of the fuel combustion process, thereby increasing the engine power and ensuring the environmental safety of exhaust gases.

Numerical and experimental investigation of exhaust manifold configurations of turbo-charged diesel engines

The exhaust energy recovery is significant for engine fuel efficiency. However, the exhaust gas interference and the loss of flow affect the utilization of exhaust energy of multi cylinder turbocharged diesel engine seriously. In this paper, through Particle Image Velocimetry experiment and computational fluid dynamics simulation of exhaust T-junction flow field, the characteristics of junction local flow field and the law of energy loss are obtained. Based on the one dimensional simulation of engine working process, the exhaust available energy analysis is carried out, and the transmission of available energy of exhaust valve and various pipe systems under typical operating conditions is obtained. On this basis, five exhaust systems are designed, and the steady-state and transient performances are compared by bench tests. The results show that the shrinkage rate and the intersection angle of T-junction are the key factors affecting exhaust energy transmission and exhaust gas interference suppression. Reducing the branch pipe shrinkage rate leads to an increase in branch pipe flow loss, but it will also reduce the main pipe flow loss and exhaust gas interference. Reducing the angle between the main pipe and branch pipe is beneficial to the exhaust flow and exhaust energy recovery. The pulse converter exhaust system has a high exhaust available energy transmission rate; the Modular Pulse Converter system has superior fuel efficiency and transient response performance from the perspective of the entire engine operation range. The 90% response time difference between the five studied exhaust systems is about 0.41 s.

Efficiency Control Improvement Of Diesel Engines Conditions By Using The Method Of Analytical Synchronization Of Monitored Data

Improving the efficiency of the ship's diesel power plant is becoming increasingly important every year. This is primarily due to the restrictions on emissions of sulfur and nitrogen oxides into the atmosphere during the operation of the ship's diesel engines. Article is devoted to the problem of synchronization of data monitoring working process in transport diesel engines operation. The accuracy of data synchronization determines the error in determining power, control of the main engine systems operation and its diagnostics. The method of solving the synchronization problem must be analytical. The method of solving the synchronization problem must be analytical. In comparison the hardware methods used in most diagnostic systems of the working process of diesel engines have several disadvantages. It is impossible to conduct rapid diagnostic control in operation, non-stationary phase and amplitude errors in calculation the main parameters of the working process, the need for preparatory operations and related need for temporary withdrawal of diesel engine operation, complexity and high cost of diagnostic control. An analytical synchronization method is developed based on the top dead center coordinate determination algorithm, which uses three stages: linear, sinusoidal and model equal to zero the first derivative of the pressure under compression. The proposed method of analytical synchronization gives the obvious advantages for monitoring working process systems of diesel engines. The error in determining the main parameters of the working process and the indicator power does not exceed 2.5%.

Evaluation of the significance of the effect of the active cross-sectional area of the inlet air channel on the specific enthalpy of the exhaust gas of a diesel engine using statistics F of the Fisher-Snedecor distribution

This paper presents the application of Fisher-Snedecor distribution F statistics to assess the significance of the influence of changes in the active cross-sectional area of the inlet air channel (Adol) flow in a diesel engine on the observed diagnostic parameter determined on the basis of measurements of the quick changing exhaust gas temperature in the outlet channel, which is the specific enthalpy of the exhaust gas stream within one engine operating cycle (hspal). A plan of experimental tests carried out on the laboratory stand of a single-cylinder Farymann Diesel type D10 laboratory engine was presented and the method of determination of F statistics values for the obtained measurement results was characterized. Representative results of calculations were presented and the strength of Adol input parameter influence on the determined diagnostic parameter hspal simplified physical model of the working process of a compression ignition engine as the object of diagnosis was evaluated. It is planned to further develop the experimental research program to determine the significance of the influence of changes in the values of selected parameters of the engine structure on other diagnostic measures determined from the exhaust gas temperature signal, i.e. the mean peak-to-peak value as well as the rate (intensity) of increase and decrease in its value for individual engine cycles.

Analysis of the operation of the diesel engine on rapeseed oil

A comparative study of the working process of a rapeseed oil diesel engine for split fuel equipment and Common Rail equipment was carried out. The indicators of the working process, the parameters of heat emission and toxicity of the exhaust gases are given, the analysis of the indicator efficiency is carried out and the perspective of the use of the pilot portion in the fuel equipment of the Common Rail type is shown. One of the ways to improve the performance of diesel engines is to reduce the heterogeneity of the fuel-air mixture in the combustion chamber and the use of vegetable fuels, which include vegetable oils.

FEATURES OF ANALYTICAL SYNCHRONIZATION OF DATA OF WORKING PROCESS MONITORING IN TRANSPORT DIESEL ENGINES UNDER OPERATION

The article discusses methods for determining top dead center, based on the analysis of pressure diagrams of a marine engine. The advantages and disadvantages of different methods are shown. Diagnostics of marine engines during operation and selection of optimal operating modes are based on the analysis of pressure diagrams, as well as fuel supply and gas distribution diagrams. As a result of the analysis of the pressure diagrams, the indicator engine power is calculated, which is further used in the control of engine operation modes, in the calculation of specific indicators, as well as in the calculation of energy efficiency coefficients of marine vessels according to IMO recommendations. The influence of the accuracy of determining the position of the top dead center on the calculation of the mean indicated pressure and indicated power is shown. Solving the problem of synchronization of data of working process monitoring using hardware sensors is unacceptable due to the complexity, and sometimes the impossibility of installing hardware sensors for the position of the top dead center of the piston, in addition to the standard sensors. This also leads to a more complex measurement pattern, combined with high accuracy, which is dependent on the load mode. In addition, the installation of hardware sensors is time-consuming and involves organizational problems, as it is necessary to temporarily disable the engine. The mentioned problems are absent in case of analytical data synchronization. It is shown that the existing methods of analytical synchronization are not effective enough for the operating conditions of transport engines. This is mainly due to the complexity of the formulation of the synchronization criteria or their lack of precision due to the impact of noise in the output data. In portable diagnostic systems, the top dead center determination is best done immediately by the analytical method. Principally, there are inconveniences during the diagnosis of engines, because additional pickup sensors and their cables must be used. Before installing the sensors, it is necessary to take the engine out of operation. The installed sensors must be calibrated, which is associated with a significant investment of time. All portable systems for parametric engine diagnostics measure the pressure in the working cylinder through the channel of the indicator valve. In this regard, in portable systems, in addition to the aforementioned errors, errors occur such as throttling and delay of the signal, which leads to an additional shift of the top dead center position. Thus, recently, most modern portable systems for diagnosing marine diesel engines do not use pickup sensors, but use different variants of the analytical determination of top dead center. Diagnostics of marine engines during operating and the selection of optimal operating conditions is based on the analysis of gas pressure diagrams, as well as fuel supply and gas distribution diagrams. As a result of the analysis of the pressure diagrams, the indicator engine power is calculated, which is further used in the management of engine operation modes, in the calculation of specific indicators, as well as in the calculation of energy efficiency coefficients of marine vessels according to International maritime organization recommendations. The authors claimed a method for determining the top dead center, based on solving the equation of equality to zero the first derivative of the gas pressure under compression, which provides the required accuracy in calculating the average indicated pressure and indicator power of the engine during operation. It is shown that the method can be applicable in marine engine working process monitoring systems as an alternative to hardware methods for determining the top dead center.

IMPLEMENTATION OF HIGHLY EFFICIENT THERMODYNAMIC CYCLES IN TWO-STROKE SOLID-FUEL PISTON INTERNAL COMBUSTION ENGINES OF SHIP PURPOSE

An analysis of global fuel resources indicates that the most common fossil fuels on earth are solid fuels. Experts believe that while maintaining the current pace of their use, coal reserves will be enough for at least another 400...450 years. The low price of this type of fuel makes their use an attractive prospect for use as engine fuel for internal combustion engines. Attempts to create engines capable of working on solid fuels have been made throughout the entire period of the ICE's existence, starting with the work of R. Diesel to create its rational engine. However, throughout this period, the main efforts of specialists were aimed at adapting existing types of piston engines operating on liquid or gaseous fuels for the use of coal fuel in the form of fine dust directly supplied to the working cylinder, or injected into the combustion chamber in composition of a fuel or water-coal suspension. The first attempt to develop an engine that was specially created for the use of solid fuels and which would maximize the advantages of their state of aggregation was the work of the American engineer Joseph C. Firey, who proposed a design with in-cylinder gasification of solid fuel. Subsequently, the authors have improved this method by organizing a forced purge of a layer of solid fuel in the process of supplying heat to the working medium. The authors have developed and implemented a numerical model of this engine working process, using which a number of studies were carried out aimed at finding new approaches to the organization of working processes in solid-fuel engines with layered combustion, which allow the maximum use of the features of preparing an air charge for combustion and a controlled heat supply process to increase the thermodynamic efficiency of the workflow. This article is devoted to the discussion of the results of this study.

Analysis and Optimisation of Thermo-Mechanical Coupling Load of Cylinder Head Considering Fluid-Structure Interaction for a Marine High-Power Diesel Engine

A one-dimensional model of the diesel engine working process was established, and thermal boundary conditions of gases contacting with a cylinder head were determined by comparing them with the results of a routine test. A fluid-structure interaction model between the cooling water and cylinder head passages was established in which boundary conditions of cooling water were obtained by computational fluid dynamics analysis. Simultaneously, considering the pressure mechanical load in the cylinder, temperature and the stress distribution of the cylinder head were analysed by the model with a thermo-mechanical coupling load. The model was validated using the temperature hardness plug method. Four parameters of intake valve opening, exhaust valve opening, fuel supply beginning, and compression ratio were selected as influencing factors, and the thermo-mechanical coupling load of the cylinder head was optimised by the Taguchi and analysis of variance method subsequently. The study indicates that the error of the calculation model for the cylinder head’s thermal-mechanical coupling load is within ±1.5%, and the proportion of the thermal stress in the cylinder head thermal-mechanical coupling stress is above 90%. The fuel supply beginning has the greatest influence on the thermal load of the cylinder head. Based on the optimisation methods within the required power range, the maximum temperature and maximum thermo-structural coupling stress of the cylinder head are decreased by about 10.05 K and 7.13 MPa in the nose bridge area, respectively.

Optimization of Fuel Injection Control System of Two-Stroke Aeroengine of UAV

Power efficiency of two-stroke spark-ignition engine is generally low because improper amount of fuel injection leads to a lot of unburned fuel loss during the engine working process. However, parameters of the fuel injection system are hard to confirm by aviation experiments due to expensive test costs. This paper proposes a method of calibrating injection parameters of two-stroke spark-ignition engine based on thermodynamic simulation and parameter optimum algorithm. Firstly, the one-dimensional thermodynamic model is built according to the internal structure and thermodynamic process of the engine; then, the model parameters are corrected according to the operating principle of the injector; after experimental verification of the model, considering both the engine power sufficiency and fuel economy, Analytic Hierarchy Process method is applied to look for the optimal injection amount and fuel injection advance angle at different engine working speeds; finally, an aeroengine experiment station with an electronic fuel injector system is built. Through simulation and experiment studies, it can be seen that when the engine speed changes from 3000 to 3500 RPM, the oil consumption rate of the optimal results is higher than that of the previous ones; when the aeroengine speed is higher than 4000 RPM, the oil consumption rate results of the optimal method are 10% to 27% higher than the original results. This paper can be a reference in the optimization of UAV aircraft engine.