Spray Characterization of Ethanol Gasoline Blends and Comparison to a CFD Model for a Gasoline Direct Injector 2010-01-0601

Operation of flex fuel vehicles requires operation with a range of fuel properties. The significant differences in the heat of vaporization and energy density of E0-E100 fuels and the effect on spray development need to be fully comprehended when developing engine control strategies. Limited enthalpy for fuel vaporization needs to be accounted for when developing injection strategies for cold start, homogeneous and stratified operation.

Spray imaging of multi-hole gasoline injectors with fuels ranging from E0 to E100 and environmental conditions that represent engine operating points from ambient cold start to hot conditions was performed in a spray chamber. Schlieren visualization technique was used to characterize the sprays and the results were compared with Laser Mie scattering and Back-lighting technique. Open chamber experiments were utilized to provide input and validation of a CFD model. In addition to the fuel variation and operating conditions three different injectors were investigated with differences in static flow rate and internal nozzle geometry. This empirical data was used in the initial development of a robust CFD model for predicting spray behaviors from a multi-hole gasoline direct injector. Comparisons of spray penetration were made between the optimized CFD model and the empirical results. Image processing techniques were presented for characterizing the spray images to quantify the penetration and the vapor cloud development.

3D-CFD numerical simulation is commonly used in order to make selections of engine injection in the early design period. In this article, the spray behavior was predicted by CONVERGE, The characteristics of the spray tip penetration and mass of the liquid and vapor phases were calculated under different temperature and pressure conditions,

Testing was also conducted at realistic chamber operating conditions for stratified operation. In these test the piston crown geometry was included in the spray chamber to evaluate fuel impingement effects. Schlieren imaging provided insight into the effect of spray impingement resulting in spray bounce and fuel puddles.