柴油机缸内近气缸盖壁面边界层预测模型的研究

摘要

The investigation of velocity and temperature boundary layer near wall in cylinder is very important for understanding the convection heat transfer and the exhaust emission of engine.The present paper analyzed the form process of the velocity and temperature boundary layer near wall in cylinder.Velocity and temperature wall function is derived.Velocity and temperature profile,boundary layer thickness are studied.The prediction results are found to be in conformance compared with the measurement results in a motored engine.The present work shows that the boundary layer may be formed near head wall in cylinder.The thickness of velocity boundary layer equals approximately the thickness of temperature one.Both are about 2 mm～4 mm．%分析了缸内壁面速度边界层和热边界层的形成过程，建立了缸内近气缸盖壁面湍流速度壁面函数和温度壁面函数，研究了边界层内的速度分布、温度分布及速度边界层厚度和热边界层厚度，并将预测结果与拖动发动机的实测值进行了比较，发现两者的趋势是一致的。研究结果表明，缸内近气缸盖壁面有边界层形成，同一位置的速度边界层与热边界层的厚度很接近，不同位置的边界层厚度不同，大约在2 mm～4 mm左右。