Numerical Analysis on Multi-Component Fuel Behaviors in a Port-Injection Gasoline Engine

A multi-component fuel vaporization model is developed for numerical analysis of specific fuel component behaviors in port-fuel-injection(PFI) gasoline engines. In order to specify the differences of in-cylinder fuel distribution among its components, three-dimensional calculations of intake flow, spray and vapor motion of each component are performed with respect to engine wall temperature and the distillation characteristics of the fuel. Simultaneous measurements of in-cylinder behaviors of different volatility components in the fuel are also carried out using a laser-induced fluorescence (LIF) technique to validate the calculation results. In both measurements and calculations, the same fuels are used, which are composed of seven or eight components to simulate the distillation characteristics of two kinds of gasoline. The in-cylinder vapor amount of high and low volatility components is compared between the calculations and the experiments. Good agreement is obtained for each component. Both numerical and experimental results show that under high wall temperature conditions, the vapor amount of high volatility components in the cylinder is equivalent to almost all the injected mass in one cycle, at the other extreme under low wall temperature conditions, there is little vapor of low volatility component. Calculation results also show that the greater part of the high volatility component vaporizes from ‘flying’ droplets during intake stroke and its vapor is transported by intake flow. On the other hand, more than 40% of the low volatility component sticks on the intake port wall. Most of the rest of low volatility component also gets into a ‘wall-wetting’ film in the cylinder. The fuel component behavior is therefore completely different depending on the volatility.