Spray-wall impingement in a multi-hole GDI injector for split injection at elevated wall temperature and ambient conditions

Post wall-impingement characteristics of pulsatile and split injection sprays in multi-hole Gasoline Direct Injection (GDI) are investigated. A combined experimental and numerical approach is adopted, to examine the influence of wall temperature as well as gas temperature and pressure on spray evolution. For fuel injection condition, split proportion and wall stand-off distance are not varied. The single injection case is also studied for comparison. The experiments were conducted under atmospheric conditions but for different wall temperatures, and the fuel spray was visualized using high-speed shadowgraph technique. The three-dimensional Eulerian-Lagrangian spray simulations were validated against the measured post-impingement plume width and height. Simulations were carried out to analyse spray-wall interaction process under elevated ambient temperature and pressure conditions also. Considerably smaller radial and vertical spread of the spray plume is obtained for split injection, highlighting its benefits over the single injection case. Both plume and wall film characteristics are strongly influenced by the ambient gas density and temperature rather than the wall temperature. However, time evolutions of the mass, thickness and temperature of the film are similar for both single and split cases at different operating conditions, exhibiting some interesting trends. For split injection, the vapour plumes from the two injection pulses interact. At high ambient temperatures, the peak equivalence ratio values are lower for split injection due to lower injected mass per pulse, in comparison to the single injection strategy.