Analysis of fuel film formation process at low temperature by wall impingement direct injection gasoline spray

Abstract

In a direct-injection gasoline engine, strict control of pollutant emissions at cold start is a critical point to comply with new regulations, and the fuel film formed by spray impingement on the piston wall is closely related. In this context, the purpose of this study is to clarify the fuel film formation process of spray impinging on a low temperature wall. Total internal reflection laser induced fluorescence (TIR-LIF) method was applied to the fuel film formed by wall impingement gasoline spray. TIR-LIF method can measure the fluorescence from fuel film without the influence of the spray droplet. The fluorescence intensity from the fuel film depends on the film thickness and temperature. In this paper, the temperature dependence of the fluorescence from the fuel film was investigated under the condition that the laser light is totally reflected from the top surface of the film. The order of magnitude of the heat transfers due to the mixing of spray droplets and fuel film, the heat transfer from the ambient gas, and the heat transfer from the wall were compared and modeled. A method to simultaneously calculate the unsteady change in fuel film thickness and fuel film temperature was developed. Then, the model analysis method was applied to the measured experimental data and verified.

Keywords

• spark ignition engine
• fuel film
• wall impingement spray
• laser induced fluorescence
• pm/pn