Computational investigation of micron-sized diesel droplet trains impinging on thin liquid films*

We present 3D simulations of micron-sized diesel droplet trains impinging on pre-existing fuel films. The droplet size and impact velocity are representative of the impingement conditions during fuel injection in internal combustion engines. To study fuel injection under such conditions, Lagrangian-Eulerian solvers are generally used. However, they rely on spray-wall interaction sub-models to predict the surface impingement outcome of fuel droplets. Using droplet trains as an idealized spray, we will assess the accuracy of such sub-models. Using highly-resolved simulations the effects of pre-existing film thickness on the splashed mass ratio are quantified. The splashed mass ratio from our simulations is compared with predictions of commonly used spray-wall interaction sub-models. Furthermore, using passive scalars we quantify the contribution of each droplet to the liquid film and splashed liquid mass, providing unique insights into the post-impingement dynamics.