A general splash model for direct injection engine multi-dimensional simulation

The interaction between impacting and splashed droplets on the combustion chamber walls and inlet air motion plays a fundamental role in the mixture formation process. It covers a crucial aspect for the correct operation of both DI diesel and gasoline engines as it greatly influences the combustion process and the exhaust emissions. A complete understanding of spray impingement is quite complex. In this paper, a numerical-experimental approach is proposed.

On the experimental side, the behaviour of a Diesel impinging spray emerging from a common rail injection system (injection pressures of 80 MPa and 120 MPa) and of a gasoline hollow cone spray generated by a swirled injector (injection pressures up to 10.0 MPa) have been analysed. The impinging spray has been lightened by a pulsed laser sheet generated from the second harmonic of a Nd - YAG laser. The images have been acquired by a CCD camera at different times from the Start of Injection. Digital image processing software has enabled to extract the characteristic parameters of the impinging spray with respect to different operating conditions.

The numerical analysis is carried out by means of a multi-dimensional numerical tool, based on the KIVA-3V code. The spray-wall interaction is simulated through a properly modified phenomenological splash model available in literature. Based on the experimental evidences, the proposed modified version of the model is proven to be an adequate representation for different injection pressures and back-pressures