【作者】 李冰林；

【导师】 魏民祥；

【作者基本信息】 南京航空航天大学 ， 车辆工程， 2011， 博士

【摘要】 与汽油相比，煤油因具有闪点低、粘度大、不易挥发等特性，且使用安全性能高，在一些军事背景的特种车辆中有较广阔的应用前景。但是由于煤油的雾化效果差，与汽油相比燃烧特性发生了较大的变化，特别是煤油的燃烧速度慢，对应的点火特性与汽油相比区别较大。点火提前角对发动机的性能有着重要的影响，国内外对活塞式煤油发动机的燃烧特性，特别是点火提前角特性研究较少，所以对发动机燃烧煤油的点火特性进行研究，具有重要的理论指导意义和工程应用价值。本文结合某国防预研项目，完成了某小型二冲程汽油发动机燃烧航空煤油的点火提前角及相关问题研究，内容围绕点火控制器的开发、点火提前角的标定与控制加以展开，主要研究内容和创新如下：1.为获得原型机的相关参数，建立了发动机的测试系统，对二冲程发动机的点火参数进行了采集和提取，获得了发动机燃烧汽油时的点火提前角，为分析发动机燃烧煤油的工作性能提供了参考依据。2.采用数值计算方法研究了发动机缸内煤油燃烧状况以及NOx排放。对燃烧室进行了三维建模，并利用动网格技术模拟了缸体运动。分析了发动机正常热工况，不同点火提前角和不同进气压力参数下的燃烧状况，比较了发动机燃烧煤油的排气温度和NOx排放等；探讨了火花塞周围影响点火成功的湍动能和速度场。对相同工况下汽油和煤油的燃烧性能进行对比，结果表明，煤油比汽油燃烧速度慢，点火滞燃期长。通过试验分析，在转速为5500r/min节气门开度为50%工况点，发动机燃烧煤油的最佳点火提前角要比燃烧汽油时的最佳点火提前角大10°CA。3.利用GT-POWER对发动机燃烧煤油的整机性能进行了数值模拟，探讨了点火提前角对发动机动力性、排放性能等的影响；分析了压缩比、进气压力、进气温度和空燃比等对点火提前角的影响；针对不同的工况条件，充分考虑动力性而忽略经济性与排放性的前提下，通过计算获取了发动机初始点火数据图（MAP），为发动机燃烧煤油的点火提前角控制提供了重要的理论依据。4.为寻求发动机最佳点火提前角，以GT-POWER仿真的初始点火MAP为参考，通过台架试验进行了标定修正，获得了不同工况下的燃烧煤油最佳点火MAP。基于模糊自寻优控制算法，发展了点火提前角标定方法，以初始点火MAP为基值，在稳态工况条件下对点火提前角标定，并通过Simulink与GT-POWER联合仿真验证了该方法的可行性。5.针对发动机燃烧煤油的爆震问题，采用了小波分析方法对不同点火提前角的缸内压力信号进行爆震检测分析，提取发动机爆震特征，为发动机燃烧煤油的点火提前角控制提供了参考依据。6.以嵌入式16位微控制器为核心，设计了点火电控单元的数据采集和控制硬件电路，完成了控制软件设计，实现了发动机的点火控制，并解决了火花塞电磁抗干扰问题。基于VisualStudio/C++平台设计了点火参数调整和监控标定系统，实现了对试验数据的实时监测、保存及历史数据的回放，以及发动机点火MAP实时在线改写功能。7.建立了发动机试验台，对论文研制的点火系统的发动机性能进行试验，并与原型机进行了对比。结果表明，点火提前角的重新标定获得了较好的动力输出性能，所研制的点火系统有效地提高了发动机的输出扭矩。对比分析了数值计算与试验结果，验证了数值计算结果的正确性；分析了不同点火提前角的煤油发动机的燃烧循环变动，结果表明其燃烧变动率均小于10%，发动机工作在正常范围内。在试验数据分析过程中，利用最小二乘支持向量机对发动机的缸内压力进行回归分析，该方法在样本数较少的情况下能得到比较精确的结果，提高了分析精度。更多还原

【Abstract】 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.更多还原