Investigation of the liquid fuel film from GDI spray impingement on a heated surface with the laser induced fluorescence technique

Abstract Quantitative two-dimensional characteristics of the liquid fuel film on a superheated smooth surface after the impingement of a GDI spray were investigated with laser induced fluorescence technique. Morphologies of fuel film changes from continuous wavy ‘film’ at 25 °C to liquid strings and ‘holes’ at 100 °C and to isolated distributing drops above 140 °C. A sensible calibration method was established by constructing an intensity profile function for the excitation laser based on the two-variate Gaussian distribution function. A series of injection durations were tested to simulate the evolution of the liquid wall film. The volume of the fuel film was found to increase almost linearly with injection duration under low surface temperature. The ratio of the wall film volume to the total injected volume is independent of the injection duration between 1 and 3 ms, but decreases gradually with increasing temperature. About 60% of the injected volume deposits on the surface of 25 °C, this value reduces to about 30% at 140 °C and 15% at 180 °C, and almost no fuel film could be found when the surface is heated to 220 °C. The Leidenfrost phenomenon hardly affects the volume of the fuel film in a short time after impingement.