Numerical Simulation of the Gas Flow Accompanied by Pressure Wave Propagation and Diffusion Phenomena in Internal Combustion Engines

为了提高内燃机非定常气体流动的模拟精度，减小数值误差即伪扩散误差是十分重要的。通过各种方法的调查得到的结果如下：1。利用CIP方法，由于其虚假扩散很小，具有较高的精度，从而明确了注入气体在涡旋运动下的扩散过程。在此基础上，采用CIP方法对火花点火发动机内燃料气体和空气混合物的扩散过程进行了数值分析，揭示了混合气体分层形成的过程。通过将燃油喷射模型纳入计算程序，对进气道喷射发动机混合气形成过程进行了数值分析，预测了燃油液滴的行为和燃油蒸气浓度的分布。在预测发动机性能时，有必要对排气系统中的各种气体流动进行评估。本文提出了一种基于特征的方法，适用于锥形管内的气体流动，也适用于温度急剧变化的气体流动。将该方法应用到预测程序中，讨论了发动机系统的优化问题。结果表明，该程序可用于发动机系统的研制。在含压力波气体流动的三维分析中，研究了消声器结构对消声器内压力损失和声学特性影响的预测方法。通过将计算的压力损失与实验值进行比较，证实了该方法可以预测压力损失随消声器尺寸的变化趋势。

It is important to reduce the numerical error, that is, false diffusion error in order to improve the simulation accuracy of unsteady gas flows in internal combustion engines. The results obtained through the investigation of various methods are as follows :1. By using the CIP method with high accuracy because its false diffusion is very small, the diffusion process of injected gas due to vortex motion has been made clear. Furthermore, the diffusion process of the mixture of fuel gas and air in a spark ignition engine has been numerically analyzed by the CIP method, and the process of stratified mixture formation has been shown. By incorporating fuel spray models into the calculation program to numerically analyze the process of mixture formation in a port-fuel-injection engine, the behavior of fuel droplets and the distribution of fuel vapor concentration have been predicted.2. In predicting the engine performances, it is necessary to evaluate various gas flows in exhaust systems. The method based on characteristics has been developed for the gas flow in a tapered pipe and also for the gas flow with the steep change of temperature. Applying this method to the prediction program, the optimization problem of engine systems has been discussed. The results shows that the program is useful in developing the engine systems.3. In three-dimensional analysis of gas flow including pressure wave, a method has been investigated for predicting the effects of the configurations of silencers on both the pressure losses and the acoustic characteristics in the silencer. By comparing the calculated pressure losses to the experimental ones, it has been confirmed that the method enables one to predict the trend of change of the pressure losses to the dimensions of silencer.