Computational and Optical Investigation of Liquid Fuel Film on the Cylinder Wall of an SI Engine

The liquid fuel film on the cylinder liner is believed to be a major source of engine-out hydrocarbon emissions in SI engines, especially during cold start and warm-up period. Quantifying the liquid fuel film on the cylinder liner is essential to understand the engine-out hydrocarbon emissions formation in SI engines. In this work, the fuel film formation model was developed to investigate the distribution of wall fuel film on the cylinder wall of an SI engine. By integrating the continuity, momentum, and energy equations along the direction of fuel film thickness the simulation of the fuel film formation was carried out in the test rig. Spray impingement and fuel film models were incorporated into the computational fluid dynamics code, STAR-CD to calculate fuel film thickness and distribution of fuel film on the cylinder wall.

With a laser-induced fluorescence method, the two-dimensional visualization of liquid fuel films was carried out to validate the simulation results. Using a quartz liner and a special lens, only the liquid fuel on the liner was visualized. The calibration technique was developed to quantify the fluorescence signal. The fluorescent intensity increases linearly with increase in the fuel film thickness on the quartz liner. Using this technique, the distribution of the fuel film thickness on the cylinder wall was measured quantitatively with respect to injector angle.

In all the cases, the prediction compared reasonably well with the experimental results at the same condition as experiments.