A 3D-CFD Study of Flow Dynamics on Mixture Preparation for Fuel Injected Motorcycles

With the increased demand of mobility in the form of two-wheelers and the continued dominant share of Internal Combustion Engines (ICE) in Indian market, there is considerable influence on the deterioration of air quality. The regulators in this region have legislated Bharat Stage 6 (BS6) as a measure to restrict tail pipe emissions, which necessitates the automotive industry to work towards emission optimization measures. Some of the factors influencing this includes, air-fuel mixture formation, spray targeting, fuel properties, flow dynamics, combustion chemical kinetics, exhaust after-treatment etc. The focus area of this paper is to study the influence of air-fuel mixture formation which is highly dependent on fuel droplet atomization, injection timing, fuel injector, injection pressure and mixture preparation techniques to reduce the engine out emissions. A Three Dimensional Computational Fluid Dynamics (3D-CFD) simulation was used to evaluate the influence of flow dynamics on mixture homogeneity at various engine speeds and throttle openings. Simulation results were found to be in line with theoretical calculations with deviation under 10% on more than 90% of the operating points. A shift in re-circulation zone was observed with varied speed and load points throughout the throttle opening (0-100%). A transient analysis was also performed over engine cycle to suggest best injection timing by evaluating flow characteristics.