Development of General-Purpose Computer Programs to Predict the Performance of Four-Cycle Internal Combustion Engines for Improving Their Thermal Efficiency

本文开发了一套发动机性能预测仿真程序，采用双网格序列特征法实现了较小的数值扩散。对四缸发动机进气系统的尺寸效应对EGR率进行了估计。计算结果与实验结果吻合较好，证明了程序的有效性。对管道内激波的计算方法进行了初步的研究。一种新的计算特性的方法已经被开发出来，它可以提供准确和有效的管道内气体流动的评估，包括锥形管道内的气体流动或具有数值扩散的气体流动。复合动力系统中透平和压气机的流动特性用包含若干参数的函数形式表示。这使我们能够评估不同配置的复合电力系统的性能。在进排气系统压力波和气流的三维分析中，改进了CIP方法，采用一般曲线坐标变换来计算消声器等任意形状通道内的气流和压力波。通过对计算结果的检验，明确了消声器结构对衰减特性和压力损失的影响。为了对发动机进气道和燃烧室的三维气体流动进行数值分析，提出了一种适用于复杂形状发动机模型的体贴体网格计算方法。利用GTT程序，明确了翻滚涡的形成和崩溃过程。通过将燃油喷射模型引入该程序，预测了液体燃油喷射发动机中燃油液滴的行为和燃油蒸气浓度的分布。

A simulation program has been developed to predict the engine performance, achieving little numerical diffusion by the use of teh characteristic method with two mesh series. The dimension effect of the intake system on the EGR rate has been estimated for a four-cylinder engine. The availability of the program is recognized by the good agreement between the calculated and experimental results. A scheme to calculate the shock wave in pipes has been fundamentally investigated. A new procedure to perform characteristics has been developed and found to provide accurate and efficient evaluations of gas flows in pipes including the gas flow in a tapered pipe or gas flow with numerical diffusion. The flow characteristics of the turbine and the compressor used in compound power systems have been expressed as function forms containing several parameters. These enable us to evaluate the performance of compound power systems with their various configurations.In three-dimensional analysis of the pressure wave and the gas flow in intake and exhaust systems, the CIP method has been improved by applying the general curvilinear coordinate transformation in order to calculate the gas flow and pressure wave in arbitrarily-shaped passages such as silencers. The effect of the configuration of silencers on the attenuating characteristics and the pressure losses has been made clear by examining the calculated results. For numerically analyzing three-dimensional gas flows in engine intake ports and combustion chambers, a calculation method (GTT) which can deal with engine models having complicated shapes by using body-fitted grids has been developed. The forming and collapsing processes of tumbling vortices have been made clear using the GTT program. By incorporating fuel spray models into this program, the behavior of fuel droplets and the distribution of fuel vapor concentration in liquid fuel injection engines have been predicted.