Flame structures and combustion efficiency computed for a Mach 6 scramjet engine

Tohru Mitani, Toshinori Kouchi

Research output: Contribution to journalArticlepeer-review

88 Citations (Scopus)


Our hydrogen-fueled scramjet engines with a length of 2.1 m delivered net thrusts exceeding the engine drags and exhibited fuel specific impulses of about 10 km/s under Mach 4 to 8 flight conditions. A three-dimensional, reactive CFD code using unstructured hybrid grids was developed to accelerate the engine studies. Combustion in the scramjet engine under the Mach 6 condition was simulated by using this code. In this paper, the engine testing and the CFD code were outlined first. Timewise progress of hydroxyl radicals was investigated to understand autoignition and upstream-wise developments of combustion in the engine. Autoignition occurred from the cowl section at 0.1 ms after fuel mixing was completed. The reaction zones propagated upstream at speeds of about 500 m/s and reached the backward-facing steps in the combustor at 1 ms after the autoignition. Steady-state solutions showed small flames around individual fuel jets in the combustor and a large-scale diffusion flame downstream in the engine. Sonic combustion was autonomously realized in the combustor, resulting in delivery of a maximum thrust of 2250 N in the stoichiometric condition. Variations of combustion efficiency indicated that combustion performance was determined in a narrow region with a length of 0.15 m in the combustor and that the combustion downstream of the engine was rate-controlled by a large diffusion flame. The results found by the CFD computations enable us to not only improve engine performances but also to optimize computations for scramjet engines.

Original languageEnglish
Pages (from-to)187-196
Number of pages10
JournalCombustion and Flame
Issue number3
Publication statusPublished - Aug 2005
Externally publishedYes


  • Computational fluid dynamics
  • Flame structure
  • Scramjet engines
  • Supersonic combustion

ASJC Scopus subject areas

  • General Chemistry
  • General Chemical Engineering
  • Fuel Technology
  • Energy Engineering and Power Technology
  • General Physics and Astronomy


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