Numerical Analysis of Effect of Impacting Velocity on Diesel Droplet Impacting on Inclined Surface

Abstract:

In order to explore the process of liquid film formed by fuel droplet impact on the surface in small-size combustor of diesel engine, a numerical model was developed using coupled level set and volume of fluid method, including heat transfer and contact resistance, to explore the mechanism of a droplet impacting on inclined surface. The dynamic motion and mechanism of flow and breakup of droplet were obtained according to results analysis. The effect of impacting velocity on spreading factor, average wall heat flux, forward and backward spreading factors and spreading velocities were also explored. The results showed that the liquid jet was observed only at the front spreading edge during the oblique impact, which was different from the horizontal impact. The tangential forces for the oblique impact promoted the forward spreading and the formation of liquid jet at the front spreading edge. The breakup of liquid jet was observed at both neck and root areas. The pressure gradient inside the liquid jet was the main factor resulting in the formation, development and breakup of the liquid jet;capillary wave resulted in the breakup at the neck and root of liquid jet. The impacting characteristics were closely related to impacting velocity, the spreading factor, average wall heat flux, forward and backward spreading factors and spreading velocities obviously increased with the increase of impacting velocity;the effect of impacting velocity on impacting characteristics decreased as impacting velocity increase.