Modeling of diesel spray tip penetration during start-of-injection transients

Multiple-injection strategy that has been applied widely in diesel engines usually features a short duration for each injection pulse. As a result, the shortened injection makes the needle opening and closing transients increasingly important for spray in an injection event. Owing to the needle movement, the spray development during the transient processes is complex and quite different from the spray at the quasi-steady state. However, so far modeling of the spray development during the transient processes is far from adequate. Particularly, a theoretical zero-dimensional (0-D) spray tip penetration model considering the needle opening and sac pressurization processes as well as ambient and injection conditions during the start-of-injection (SOI) transients is still absent. In this paper, considering the sac pressurization processes, the 0-D model of spray tip penetration during the SOI transients is derived. Then, the model is validated against the experimental spray data using a long-distance microscope together with an ultrahigh speed CMOS camera. The model and experimental results show that the spray tip penetration shows at(3/2)dependence at the initial stage of injection rather than thetdependence suggested by Hiroyasu's model. Later, the spray tip penetration shows at(3/4)dependence owing to the spray breakup, and at(1/2)dependence with the completion of sac pressurization. The models and analysis are believed to provide new insights into the transient spray behaviors and valuable reference for engineers and researchers who are considering the model-based development of next-generation diesel engines.

Automated summary

In this paper, a new 0-D model describing the spray development during the transient processes at the start of injection in diesel engines is proposed. Experimental results show that the spray tip penetration behavior deviates from conventional models, providing valuable insights for engineers and researchers.