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基于飞轮转速的平均指示压力及气缸压力识别
Recognition of Indicated Mean Effective Pressure and Cylinder Pressure Using Flywheel Speed
【作者】 韦小刚；
【导师】 甄龙信；
【作者基本信息】 燕山大学 ， 车辆工程， 2012， 硕士
【摘要】 平均指示压力是指发动机单位气缸容积所做的指示功，是发动机扭矩管理系统中的重要信号，基于压力传感器的平均指示压力计算方法成本过高，且只限于在实验室中使用。通过其它低成本方法间接估计气缸压力以及平均指示压力对于实现发动机故障在线监测、诊断和扭矩控制有着重要的意义。在四缸发动机中每缸做功区间大致与飞轮从由最小转速上升到最大转速的区间相对应，且各缸做功区间基本上独立。本文首先利用编程得到每缸平均指示压力以及每缸做功过程中对应的飞轮转速波峰谷值以及平均转速，在对单缸机平均指示压力与转速波动模型改进的基础上得到了四缸机平均指示压力单工况模型，并提出了无需判断发动机运行工况的的平均指示压力计算方法及通用模型，基于平均指示压力模型计算的平均指示扭矩的绝对误差在4N·m以内。对现有的汽油机单区燃烧模型进行简化，得到一个关于散热比、定热容比、效率系数、形状系数和燃烧持续角度5个特征参数的简化模型，用最小二乘法对176组气缸力压数据从燃烧起点到排气门开启区间进行拟合，得到这5个参数经验模型公式，最终根据回归的气缸压力模型计算了IMEP、50%和90%已燃烧质量分数角度。在前一章工作的基础上建立了从进气门关闭到排气门开启阶段的压力模型，并对其关键参数进行回归，计算了初始压力估计误差和模型参数误差对气缸压力和平均指示压力回归效果的影响。
【Abstract】 Indicated mean effective pressure is the indicated work done by engine per cylindervolume which can be used for engine torque control. IMEP based on cylinder pressuresensor is costly to obtain, only limited. in a lab environment. So other indirectly low-costestimation methods of cylinder pressure and IMEP will be of of great significance forengine online monitoring, diagnosis and control.Firstly in the four cylinder engine each cylinder acting range is basically independentand the power region of fired cylinder is approximately in accordance with the regionthat flywheel speed rises from minimum to maximum. The individual cylinder IIMEP,speed, and mean speed is obtained by programming, and new model about individualIMEP and speed fluctuation is developed under the theoretical model of single cylinder forsix different operating cases. Then put forward the IMEP common model withoutdetermining the engine running cases. The absolute error of the mean indicated torquebased on IMEP common model is between 4N·m.Secondly, the existing single-zone combustion model of gasoline engine is simplifiedas a five parameters model of heat dissipation scale coefficient, specific heat ratio, wiebeefficiency coefficient, wiebe form coefficient and combustion duration. Least squaresmethod is used to fit the region of the cylinder pressure curve. Under the method of theexisting literature the empirical model formula of the five parameters was obtained. finallyIMEP, Mass fraction burned 50% and 90 was calculated based on the regressed model ofcylinder pressure.Finally the last chapter gives the model of cylinder pressure from intake valve closingto the exhaust valve opening on the basis of previous chapter and the key parameters ofthe mode is regressed. The effect of initial pressure estimation error and modeling error oncylinder maximum pressure and IMEP was calculated.