Spray Tip Penetration of Inversed-delta Injection Rate Shaping in Non-Vapourising Condition

Abstract

The performance and emissions of diesel engine are highly depending on the fuel delivery process thus, injection rate shaping approach is expected to be crucial in the development of a highly efficient and clean modern engine. A novel rate shaping injector called TAIZAC (TAndem Injection Zapping ACtivation) is used to realise an injection rate shaping of progressive ramp-down of high initial injection pressure as in inversed-delta shape. This study aims to investigate diesel spray tip penetration behaviour in inverseddelta injection rate shaping. The experiments are conducted under a high-density nonvapourising condition in a constant volume combustion chamber. High-speed diffused back illumination DBI imaging of the diesel spray is acquired at 30,000 fps using mercury lamp as the light source. The tip penetration of the inversed-delta injection is smaller than that of rectangle injection regardless of their injection momentum which is proportional to t0.5 and t0.43 in rectangle and inversed-delta injection case, respectively. To examine the potential of inversed-delta injection on wall heat loss reduction, diesel spray flame impinges to a MEMS sensor located at 28-mm downstream. It is interesting to note that the heat flux in 200 MPa inversed-delta injection is reduced by approximately 15% compared to 200 MPa rectangle injection even though their tip penetration starts to diverge at approximately 30 mm; indicates the TAIZAC injector potential in improving engine thermal efficiency.