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

Abstract

Stratification is seen as a prominent technique for improving the performance ofspark ignition engines especially at part loads. Though rotary engines have highspecific power, they suffer high fuel consumption and HC emission. For thisreason, direct injection methods in rotary engines have been investigated sincethey were introduced to the market. In this study, early direct injection in a sideported rotary engine was investigated by using CFD techniques. The aim of thestudy is to obtain the potential of low pressure direct injection method on mixtureformation process. Geometrical model of Mazda Renesis engine that weremodified as a single rotor engine for research activities was used in the modelingstudies. Fuel was injected directly to the chamber from present oil hole locationthat 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 pointof the engine. In numerical calculations, RNG k-ε model was used as theturbulence model; spray breakup was modeled by the Taylor Analogy Breakup(TAB) model. Flow pattern of intake air and fuel droplet distributions wereinvestigated for a possibility of having rich mixture around spark plugs. Theresults showed that swirl-like motion of the side ported engine inhibits fuel sprayto accumulate in the middle of the combustion chamber. Fuel droplets were drivento the counter side of the inlet wall by centrifugal force of the inlet air. This effectreduced as the swirl flow diminishes due to sweeping motion of the rotor. It isobserved that the main flow in the chamber is converted to the tumble-like flowat middle and last part of the compression stroke.