Characteristics of Vaporizing Continuous Multi-Component Fuel Sprays in a Port Fuel Injection Gasoline Engine

Vaporization models for continuous multi-component liquid sprays and liquid wall films are presented using a continuous thermodynamics formulation. The models were implemented in the KIVA3V-Release 2.0 code. The models are first applied to clarify the characteristics of vaporizing continuous multi-component liquid wall films and liquid drops, and then applied to numerically analyze a practical continuous multi-component fuel - gasoline behavior in a 4-valve port fuel injection (PFI) gasoline engine under warm conditions. Corresponding computations with single-component fuels are also performed and presented for comparison purposes. As compared to the results of its single-component counterpart, the vaporizing continuous multi-component fuel drop displays a larger vaporization rate initially and a smaller vaporization rate as it becomes more and more dominated by heavy species. It is found that the continuous multi-component model reasonably predicts the vaporization characteristics of wall films, while the vaporization predicted with single-component models shows an intrinsic binary behavior as the wall temperature is increased around the boiling temperature of the fuel. It is shown that, although the flow and vapor distribution behaviors in PFI engines are generally similar to each other for both single- and multi-component fuels for the present warm engine case, the multi-component nature of the fuel has a significant influence on the time-space distributions of the air-fuel-ratio (AFR). The engine results also suggest that it is critical to use a multi-component vaporization model for correctly predicting and analyzing PFI engine cold start performance.