Experimental and Numerical Considerations of Air Entrainment Process of Diesel Spray

Although several efforts have been done to capture the air entrainment flux into a diesel spray, determinative results are still yet to come because of difficulty in simultaneous measurement of the spray profile and the velocity fields around the spray. Moreover, it has been obscure whether droplet dispersion effect is dominating or not on the spray air entrainment. In the study, properties such as penetration length, cone angle, and ambient velocity field around a diesel spray were investigated in detail using a constant volume chamber (CVC, bore 150 mm, height 350 mm)) and a dynamic 2D PIV system. The measurement results of the velocity field around the spray showed that the passive entrainment air flux induced by spray motion was much less than the active entrainment along with spray development or droplet dispersion. These results were compared with provisional simulation results of a commercial CFD code to confirm the share ratio of the two entrainments, and also to investigate the behaviors of a liquid spray in entraining the ambient gas at different locations in the spray body by visualizing the entrainment process of virtual marker gas injected on the spray trajectory.