基于试验和数值模拟耦合计算的汽油机缸内RGF检测方法对比及分析

Comparison and analysis of in-cylinder RGF detection methods for gasoline engines based on coupled approach of experiment and numerical simulation

为了实现发动机的精准控制,需要对缸内状态参数进行准确而实时检测。基于一维气体动力学方程,建立相应的物理计算模型,再通过检测的进排气和缸内信号数据,实时耦合到计算模型中,最后得到缸内状态参数;在三传感器法(3PA法)基础上,提出简化的检测方法,即两传感器−动态排气法(2PA-e法)、两传感器−动态进气法(2PA-i法)和单传感器法(1PA法),并分别采用这4种方法对1台增压直喷发动机缸内残余废气系数(RGF)进行检测和分析。研究结果表明:所提出的3种方法与3PA法相比计算精算都有所下降,但变化趋势一致;2PA-e法与3PA法精度接近,其计算精度比2PA-i法和1PA法的高;当转速为2000 r/min时,2PA-e法检测精度与3PA法检测精度相比较,最大降幅为4.42%;当转速为4000 r/min时,2PA-e法检测精度与3PA法检测精度相比较,最大降幅为6.32%;在过渡工况时,3种方法的精度下降幅度都不大,2PA-e法与3PA法的精度具有较好的吻合性;2PA-e法、2PA-i法和1PA法这3种方法精度下降是因为检测方法不同,导致在气阀处叠加形成的压力波幅值差异,进而影响进排气压差,最后影响进气开始时进气阀倒流的废气量。在实际应用中,可根据检测条件、速度和精度要求,选择最恰当的实时检测方法。

In order to achieve precise control of the engine,accurate and real-time detection of in-cylinder state parameters was required.Based on the principle of one-dimensional gas dynamics equation,the corresponding physical calculation model was built,and the data of intake and exhaust and the signals in the cylinder were coupled to the calculation model in line,and finally the state parameters in the cylinder were obtained.Based on the three-sensor method(3PA method),the simplified detection methods were proposed,i.e.,two-sensor dynamic exhaust method(2PA-e method),two-sensor dynamic intake method(2PA-i method)and single-sensor method(1PA method).The results show that the accuracy of the three methods proposed decreases compared with the 3PA method,but the varied trends are consistent.The accuracy of the 2PA-e method is close to that of the 3PA method,and the calculation precision is higher than those of the 2PA-i method and 1PA method.At 2000r/min,the accuracy of the 2PA-e method decreases by 4.42%compared with the 3PA method,and at 4000 r/min,the accuracy of the 2PA-e method decreases by 6.32%.In the transition condition,the accuracy of the three methods decreases a little.The reason that the accuracy of the three methods decreases is that the detection methods are different,which results in the difference of pressure wave and the pressure difference,and then results in the difference of backflow through the inlet valve.In the practical work,according to the test conditions,the speed and accuracy,the most appropriate method for detection must be chosen.