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

Mohd Fareez Edzuan Bin Abdullah*, Shinobu Akiyama, Tomoki Kinoshita, Taizo Shimada, Tetsuya Aizawa

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)


Reduction of the late combustion is of interest for further diesel engine thermal efficiency improvement. In this work, “inversed-delta” (i.e., progressive reduction of injection rate during injection period) and conventional “rectangle”-injected diesel spray flames are investigated from simultaneous high-speed imaging and in-cylinder pressure trace in a constant volume combustion chamber CVCC at modern diesel engine conditions utilizing a novel injection rate shaping TAIZAC – TAndem Injectors Zapping ACtivation injector. Optically thinner spray tip rich mixture, shorter spray tip penetration and more relatively even UV emissions distributions are noticed in 175 MPa inversed-delta injections compared to than that of 175 MPa rectangle injection profiles, probably due to much even fuel-gas mixture distribution owing to following spray velocity reduction. However, in near-zero end-of-injection EOI pressure reduction condition as in 135 MPa inversed-delta injection profile, optically thicker and broader spray mixture accompanied with intense UV emissions and long soot residence are observed, suggesting poor atomization, mixing and soot oxidation processes. Based on pressure derived apparent heat release rate AHRR, inversed-delta injection exhibits slightly faster combustion than that of rectangle injection in fixed injection duration cases. However, for constant initial injection pressure comparison cases, combustion duration is faster in rectangle injection profiles. In similar initial injection pressure cases, inversed-delta injection combustion exhibits a distinct “shoulder”-like shape, where its AHRR departs from that of rectangle injection, results in lower peak pressure but longer combustion duration. Initial similarity and departing timing of AHRR shoulder are highly identical to that of the spray tip penetration, suggesting that the inversed-delta AHRR progress is restrained from the shoulder formation timing, possibly due to smaller volumetric reactive zone at the spray periphery.

Original languageEnglish
Article number113986
JournalApplied Thermal Engineering
Early online date19 Jun 2019
Publication statusPublished - Sept 2019


  • Diesel spray flame
  • Injection rate shaping
  • Late combustion
  • Simultaneous imaging
  • Thermal efficiency

ASJC Scopus subject areas

  • Energy Engineering and Power Technology
  • Industrial and Manufacturing Engineering


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