Investigation of Spray Evaporation and Numerical Model Applied for Fuel-injection Small Engines

The purpose of this research is to develop a prediction technique that can be used in the development of port fuel-injection (hereinafter called PFI) gasoline engines, especially for general purpose small utility engines. Utility engines have two contradictory desirable aspects: compactness and high-power at wide open throttle. Therefore, applying the port fuel injector to utility engines presents a unique intractableness that is different from application to automobiles or motorcycles. At the condition of wide open throttle, a large amount of fuel is required to output high power, and injected fuel is deposited as a wall film on the intake port wall. Despite the fuel rich condition, emissions are required to be kept under a certain level. Thus, it is significant to understand the wall film phenomenon and control film thickness in the intake ports. In this study, spray characteristics and film thickness have been measured with an experimental apparatus, which recreates the phenomena in an intake port. In parallel, in order to develop a prediction technique by use of general-purpose computational fluid dynamics software, numerical calculations have been performed and verified with experiment results. Based on the verification of the accuracy of the simulation, a performance prediction model for a port fuel injection small engine has been developed.