汽油机掺醇燃烧进气油膜湿壁温度预测

Prediction of Intake Port Wall-Wetting Temperature of SI Engines Fueled with Ethanol-Gasoline Blends

对进气口喷射汽油机进气门处传热过程进行了分析,建立了进气油膜吸附壁面温度模型.通过冷机状态起动试验和温升过程数据分析,对已有模型结构进行了细化和改进,并基于试验数据及MATLAB参数辨识工具箱对模型参数进行了辨识.根据模型结构及试验数据,分析了油膜吸附壁面温度的关键影响因素和影响规律,以及不同掺混比例乙醇汽油下的差异.油膜吸附壁面温度变化规律类似一阶惯性系统特性,其温升时间常数可视为进气流量的单值函数,但稳态项与多个发动机工况参数有关,而不同乙醇汽油下油膜吸附壁面温度则差异不大.改进与辨识后油膜吸附壁面温度模型在纯汽油及掺醇汽油下均具有较高的预测精度,可直接用于油膜动态补偿器设计.

Heat transfer process near intake valve of port injection SI engines was analyzed, and an intake port wall-wetting temperature model was proposed. Through cold start bench tests and data analysis, the model structure was then refined and improved, while its parameters was also identified based on experi- mental data and MATLAB parameter identification toolbox. According to the existing model structure ex- perimental data, the critical factors and their impact on the wall-wetting temperature were analyzed, and the difference at various mixing ratios for ethanol-gasoline blends was also studied. The variation of wall- wetting temperature is similar to the first order inertial system, in which the time constant can be treated as a single-value function of intake air flow, but the stable value depends on multiple engine condition parameters. For different ethanol-gasoline blends, the wall-wetting temperature difference is not signifi- cant. The intake port wall-wetting temperature model has high prediction accuracy both for pure gasoline and ethanol-gasoline blends, and it can be directly used for fuel film dynamic compensator design.