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.
Investigation of inversed-delta injection rate shaping diesel spray flame structure and combustion characteristics towards thermal efficiency improvement
