Investigation of atomization and evaporation characteristics of high-pressure injection diesel spray using Kelvin-Helmholz instability/droplet deformation and break-up competition model

This paper describes a numerical investigation into the atomization and evaporation characteristics of common-rail diesel injection spray using the KH-DDB (Kelvin-Helmholz instability/droplet deformation and breakup) competition model and the evaporation model. The predicted results, such as the images of spray development and SMD distribution, were obtained by using the KH-DDB competition breakup model at different injection pressures. To verify the prediction accuracy of the competition breakup model, the experiments on the atomization of common-rail diesel injector were conducted by using a PDPA (phase Doppler particle analyser) system and laser sheet method, and the experimental results on the atomization characteristics were compared with the predicted results. Also the numerical study of the evaporation characteristics of high-speed diesel spray were performed by using the proposed breakup model. It was revealed that the TAB (Taylor analogy breakup) model predicts the excessive atomization at the early stage of injection duration, whereas the KH-DDB model predicts it properly. From this point of view, the prediction accuracy of the KH-DDB competition model on the mean droplet size distribution is improved compared with the results of the TAB model, the original breakup model of KIVA-3 code. The numerical results of spatial distribution of droplet breakup indicate that both the primary and secondary breakup happen most actively at 0.7 ms after start of injection and 10 mm downstream from the injector tip.