Fuel-air mixing process of low pressure direct injection in a side ported rotary engine

Stratification is seen as a prominent technique for improving the performance of spark ignition engines especially at part loads. Though rotary engines have high specific power, they suffer high fuel consumption and HC emission. For this reason, direct injection methods in rotary engines have been investigated since they were introduced to the market. In this study, early direct injection in a side ported rotary engine was investigated by using CFD techniques. The aim of the study is to obtain the potential of low pressure direct injection method on mixture formation process. Geometrical model of Mazda Renesis engine that were modified as a single rotor engine for research activities was used in the modeling studies. Fuel was injected directly to the chamber from present oil hole location that has less geometrical constraints than any other location of the Renesis engine. Simulations were done for 2000 rpm which is a typical part load operation point of the engine. In numerical calculations, RNG k-e model was used as the turbulence model; spray breakup was modeled by the Taylor Analogy Breakup (TAB) model. Flow pattern of intake air and fuel droplet distributions were investigated for a possibility of having rich mixture around spark plugs. The results showed that swirl-like motion of the side ported engine inhibits fuel spray to accumulate in the middle of the combustion chamber. Fuel droplets were driven to the counter side of the inlet wall by centrifugal force of the inlet air. This effect reduced as the swirl flow diminishes due to sweeping motion of the rotor. It is observed that the main flow in the chamber is converted to the tumble-like flow at middle and last part of the compression stroke.