Simulation And Experimental Study On Spark Advance Of Piston Kerosene Engine

Kerosene has more extensive application prospects in some special vehicles of military back-ground compared with gasoline, owing to its characteristics such as low flash point, high viscosity,not easily volatile and high safty performance.Great changes have take place in combustion charac-teristics of kerosene as its poor atomization compared with gasoline; especially in the slow combus-tion of kerosene, the corresponding difference of ignition characteristics vary widely. Spark advancehas important influence on the engine performance. The research and application of piston enginecombustion kerosene characteristics are still less in the world, especially on the spark advance, so theresearch on combustion kerosene characteristics of piston engine has a highly theoretical significanceand value in engineering. In this thesis, the study work about the ignition of a mini two-stroke gaso-line engine burning aviation fuel is accomplished, and the content is to open out around the develop-ment, calibration and control of ignition ECU, combining to a defense pre-research project, and themajor study work and innovation are as follows:(1) An engine test system is established in order to acquire the parameters of experimental engine,and then the spark advance of the experimental engine is obtained by collecting and extracting theignition parameters, providing reference information for analysis of work performance of keroseneengine.(2) In order to know more about kerosene combustion status and the performance of NOx emis-sion, the method of numerical calculation is used.3D model of combustion chamber is established,and moving-mesh method is used to simulate cylinder body movement. The combustion status underdifferent spark advance and inlet pressure of normal heat engine is analyzed; its exhaust temperatureand NOx emissions are compared; the effect of kinetic energy field around the spark plug is analyzed.Finally, the combustion statuses of gasoline and kerosene combustion under the same parameters arecompared, and the results show that the combustion velocity of kerosene is slower than gasolion andignition delay of kerosene is longer than gasolion. Experiments show that the best spark advance ofkerosene is larger than that of gasoline10°CA when the engine runs in the speed of5500r/min,50%of throttle opening.(3) The numerical simulation of engine kerosene performance is carried out using GT-POWER,the influence of spark advance on engine power and emission performance are analyzed and discussed.And the influence on spark advance of the compression ratio, inlet air pressure, air temperature and air-fuel ratio are analyzed. Finally, through numerical calculation, initial spark advance MAP of dif-ferent working conditions is obtained based on power performance without regard to emissions andeconomic performance, providing reference for the control of spark advance of kerosene engine.(4) In order to make the engine work in optimal status, referencing to the initial spark advanceMAP obtained from GT-POWER simulation, the initial spark advance MAP is corrected by experi-ment platform and the best spark advance MAP is established under various working conditions. Incalibration method, based on the initial spark advance MAP, self-optimization fuzzy control of thespark advance is used under the engine working in steady-state conditions. Finially, the feasibility isvalided by Simulink and GT-POWER alliance simulation in algorithm.(5) Aiming at the knock problems of kerosene engine, the cylinder pressures of different sparkadvance are analyzed using the wavelet analysis method, and then extracted the knock characteristics,which gives reference to the control of kerosene engine spark advance.(6) With embedded16-bit micro-controller as the core, hardware circuit of data acquisition andcontrol is designed; the design of control software is completed; the engine spark ignition control isaccomplished and electromagnetic interference problem is solved. Based on the Visual Studio/C++platform, the ignition parameters calibration and experimental monitor systems are designed, enablingit to modify engine spark advance MAP in real-time, and realizing the experiment data real-time ob-servation, preservation and historical data playback.(7) Experimental platform of engine is established. After comparing with the engine performancebetween the original ignition system and the developed ignition system in this paper, the experimentalresults show that the last one can improve the engine power effectively and the re-calibration of sparkadvance is verified. The numerical simulation data and experimental data are compared and analyzed,and the numerical simulation results are validated. The engine performance and combustion cyclicvariation of different spark advance are analyzed using the cylinder pressure data acquired by experi-ment, the results show that the engine run well because the coefficient of variation is less than10%.During the processing of experimental data, the least squares support vector machine is proposed forthe regression analysis of the engine cylinder pressure data, which can acquire precision results, im-prove the analysis precision in the condition of few numbers of samples.