Mechanism of thermal efficiency improvement in twin shaped semi-premixed diesel combustion

Kazuki Inaba, Yanhe Zhang, Yoshimitsu Kobashi, Gen Shibata, Hideyuki Ogawa

Research output: Contribution to journalArticlepeer-review

Abstract

Improvements of the thermal efficiency in twin shaped semi-premixed diesel combustion mode with premixed combustion in the primary stage and spray diffusive combustion in the secondary stage with multi-stage fuel injection were investigated with experiments and 3D-CFD analysis. For a better understanding of the advantages of this combustion mode, the results were compared with conventional diesel combustion modes, mainly consisting of diffusive combustion. The semi-premixed mode has a higher thermal efficiency than the conventional mode at both the low and medium load conditions examined here. The heat release in the semi-premixed mode is more concentrated at the top dead center, resulting in a significant reduction in the exhaust loss. The increase in the cooling loss is suppressed to a level similar to the conventional mode. In the conventional mode the rate of heat release becomes more rapid and the combustion noise increases with advances in the combustion phase as the premixed combustion with pilot and pre injections and the diffusive combustion with the main combustion occurs simultaneously. In the semi-premixed mode, the premixed combustion with pilot and primary injections and the diffusive combustion with the secondary injection occurs separately in different phases, maintaining a gentler heat release with advances in the combustion phase. The mechanism of the cooling loss suppression with the semi-premixed mode at low load was investigated with 3D-CFD. In the semi-premixed mode, there is a reduction in the gas flow and quantity of the combustion gas near the piston wall due to the suppression of spray penetration and splitting of the injection, resulting in a smaller heat flux.

Original languageEnglish
Pages (from-to)1237-1247
Number of pages11
JournalInternational Journal of Engine Research
Volume23
Issue number7
DOIs
Publication statusPublished - Jul 2022
Externally publishedYes

Keywords

  • cooling loss
  • Diesel engine
  • energy balance
  • exhaust gas emissions
  • heat release rate
  • multi-stage fuel injection
  • premixed diesel combustion
  • thermal efficiency

ASJC Scopus subject areas

  • Automotive Engineering
  • Aerospace Engineering
  • Ocean Engineering
  • Mechanical Engineering

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