Computational Investigation of the Effects of Injection Strategy and Rail Pressure on Isobaric Combustion in an Optical Compression Ignition Engine

Hammam H. Aljabri, Xinlei Liu, Moaz Allehaibi, Abdullah S. AlRamadan, Jihad Badra, Moez Ben Houidi, Bengt Johansson, Hong G. Im

Research output: Chapter in Book/Report/Conference proceedingConference contribution


The high-pressure isobaric combustion has been proposed as the most suitable combustion mode for the double compre4ssion expansion engine (DCEE) concept. Previous experimental and simulation studies have demonstrated an improved efficiency compared to the conventional diesel combustion (CDC) engine. In the current study, isobaric combustion was achieved using a single injector with multiple injections. Since this concept involves complex phenomena such as spray to spray interactions, the computational models were extensively validated against the optical engine experiment data, to ensure high-fidelity simulations. The considered optical diagnostic techniques are Mie-scattering, fuel tracer planar laser-induced fluorescence (PLIF), and natural flame luminosity imaging. Overall, a good agreement between the numerical and experimental results was obtained. Upon validation, the optimized models have been used to conduct a comparative study between the conventional diesel combustion (CDC) and the isobaric combustion cases with different pressure levels, in terms of engine performance and emissions. Compared to the CDC case, the isobaric combustion cases led to a lower NOx emission but higher sooting tendency due to the increased diffusion combustion feature, although most of the soot was oxidized in the later engine cycle. To further reduce soot emission, the effects of various rail pressures and injector holes number were evaluated. The results indicated that the higher injection pressure was more effective in soot reduction for the isobaric combustion case but it deteriorated the thermal efficiency. It was also found that increasing the number of injector holes from the reference six to ten led to the lowest soot emission without significantly affecting the efficiency.
Original languageEnglish (US)
Title of host publicationSAE Technical Paper Series
PublisherSAE International
StatePublished - Sep 5 2021

Bibliographical note

KAUST Repository Item: Exported on 2021-10-14
Acknowledgements: The paper is based upon work supported by Saudi Aramco Research and Development Center FUELCOM3 program under Master Research Agreement Number 6600024505/01. FUELCOM (Fuel Combustion for Advanced Engines) is a collaborative research undertaking between Saudi Aramco and KAUST intended to address the fundamental aspects of hydrocarbon fuel combustion in engines, and develop fuel/engine design tools suitable for advanced combustion modes. The computational simulations utilized the clusters at KAUST Supercomputing Laboratory. The authors thank Convergent Science Inc. for providing the CONVERGE license.

ASJC Scopus subject areas

  • Safety, Risk, Reliability and Quality
  • Pollution
  • Automotive Engineering
  • Industrial and Manufacturing Engineering


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