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本文论述了应用特征线法计算柴油机排气压力波时对气缸端边界条件的处理。由于气缸盖排气道中气体流型极其复杂,不可能用一维不稳定流动模型处理,因此,当用特征线法计算排气压力波时,往往被略去不计。本文所述方法是用能量微分方程和质量微分方程处理此段流程,从而使边界条件得到简化,且其物理模型更接近实际。计算结果同实测数据对比表明,本法比以往方法的计算精度有所提高,计算时间缩短约8%。
This paper deals with the treatment of the boundary conditions at the cylinder end when using the characteristic line method to calculate the diesel exhaust pressure wave. Due to the extremely complicated gas flow pattern in the exhaust passage of the cylinder head, it is impossible to deal with the one-dimensional unstable flow model. Therefore, when calculating the exhaust pressure wave by the characteristic line method, it is often omitted. The method described in this paper deals with the flow of this section using the energy differential equation and the mass differential equation so that the boundary conditions are simplified and the physical model is more realistic. Comparing the calculated results with the measured data shows that this method has higher computational accuracy than the previous methods and the calculation time is shortened by about 8%.