边界条件对柴油机瞬态过程能量流及?流的影响规律研究

在一台高压共轨增压中冷柴油机上,分析了负荷加载时间、冷却系统温度等边界条件对典型恒转速增转矩瞬变过程能量流及?流的影响规律。结果表明,柴油机负荷加载过程热效率和?效率总体呈现先上升后下降的趋势,且加载时间越短,进气迟滞引起的能量劣变会导致更低的能量利用率;改变中冷器冷却特性,提高加载过程进气温度将导致缸内扩散燃烧份额增加、传热时间更长,而冷却液温度降低则不利于改善瞬态工况缸内等效绝热特征,导致传热和排气过程能量损失及其中的可用能份额增大;调制负荷加载时间和冷却系统温度有助于改善柴油机加载过程进气响应特性、缸内热氛围状态和绝热特征,提升柴油机瞬态工况能量利用水平。

Influence of Boundary Conditions on Energy and Exergy Flow in Transient Process for Diesel Engines

The influence of boundary conditions such as load time and cooling system temperature on energy and exergy flow in the typical constant speed torque increasing (CSTI) transient process was analyzed for a common-rail turbocharged and intercooled diesel engine. The results show that the thermal efficiency and exergetic efficiency in the loading process decrease after reaching the peak value. The shorter the loading time,the lower the energy utilization rate due to the increased intake lag. When increasing the intake air temperaturein the intercooler during the loading process, the ratio of in-cylinder diffusion to combustion increases and the rate of heat transfer is decreasing. Therefore, the decrease in coolant temperature is not conducive to improving the in-cylinder equivalent adiabatic characteristics under transient conditions. The intake air response, thermal and adiabatic characteristics can be improved by optimizing the loading time and the cooling systemtemperature, which is also favorable for improving the energy efficiency under transient conditions.