Experimental and Simulation Analysis of Spray and Combustion Characteristics in a Swirl-Chamber Diesel Engine

A swirl-chamber diesel engine has an indirect injection system in which fuel is injected into a pre-chamber called the swirl-chamber that is separated from the main chamber. Indirect fuel injection systems can be directly mechanically controlled by the camshaft, which is cheaper than electronic control. For these reasons, they are used in diverse industrial applications and automobiles. However, optimization of the swirl-chamber shape and performance tests have been mainly experimental, and there has been insufficient verification of the accuracy of simulations. Thus, we have attempted to verify simulations using a rapid compression and expansion machine that can reproduce the combustion in one engine cycle, with a chamber like a swirl chamber in the cylinder head to visualize the behavior of evaporative sprays and the combustion process. In this study, the authors focused on the wall impingement of the fuel spray and took photos of its liquid phase and ignition. Furthermore, the authors constructed simulation models using commercial 3D-CFD software based on the experimental results and established an analytical method. As a result, flow, spray, and ignition behavior in the swirl chamber were clarified through visualization experiments. In addition, numerical simulation models were constructed to reproduce the in-cylinder pressure and rate of heat release during combustion obtained in experiments using a rapid compression and expansion machine.