Spray dynamics and evaporation in a multihole GDI injector for pulsatile and split injection at elevated ambient pressure and temperature conditions

Abstract

The evolution of pulsatile and split injection spray from a multihole, Gasoline Direct Injection (GDI) atomizer at different ambient conditions is examined experimentally and computationally. The fuel is injected at 80 bar for a duration of 1.2 ms (for single injection) and also for different split proportions (ranging from 0.3 ms to 0.9 ms for the first injection and 0.9 ms to 0.3 ms for the second injection). The influence of different split proportions on the spray characteristics such as spray penetration length, cone angle and droplet size is studied in detail, and they are compared against those of single injection case to highlight the differences. Experiments were conducted in a constant volume chamber for elevated ambient pressures. The fuel spray was visualized using high-speed shadowgraph technique. Three-dimensional spray simulations were carried out using ANSYS FLUENT 16.1. The RANS-DPM coupled simulations were performed for higher ambient pressure and temperature conditions. Good agreement between the experiments and simulations is achieved with respect to spray penetration length and cone angles for both single and split injection strategies. For larger proportion of the first injection, the interaction of the second spray with the rear of the first spray was prominent at higher chamber pressure. The spray penetration length was found to reduce for split injection strategy for all ambient pressure conditions. The spatio-temporal evolution of vapour plumes in terms of equivalence ratio highlights the possibility of attaining near homogeneous, rich mixture or a stratified mixture depending on the split proportion and dwell time.