Numerical and experimental study of spray impingement and liquid film separation during the spray/wall interaction at expanding corners

The liquid film separation at expanding corners during the spray/wall interaction is usually encountered in internal combustion engines, which has significant influence on the fuel/air mixing and combustion processes, and consequently the engine-out emissions. However, fundamental investigations on the film separation during the spray/wall interaction at expanding corners are very limited, especially under the relevant operating conditions of engines. In the present study, a new film separation and atomization model was proposed, including the sub-models of film separation criterion, film separation mass ratio, and the film atomization model derived from the Rayleigh-Taylor instability theory. By implementing the proposed model into a computational fluid dynamics (CFD) code, the reliability of the new model was validated by the experimental measurements conducted in this study. The results indicate that the effects of the injection pressure, impingement distance, and corner angle of the expanding corner on the evolution of the impinging spray and the wall film dynamics after the corners are satisfactorily reproduced by the present model. Moreover, the predicted size distribution of the detached droplets formed by the film separation is in good agreement with the measurement. It is also found that the expanding corner angle remarkably affects the impinging spray structure and the film separation characteristics, and the predictions of the new film separation model agrees better with the measurements than the previous model.