Structure and acoustic-pressure response of hydrogen-oxygen diffusion flames at high pressure

C. H. Sohn, S. H. Chung, S. R. Lee, J. S. Kim*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

39 Scopus citations

Abstract

The flame structures and extinction characteristics of undiluted hydrogen-oxygen strained diffusion flames at high pressures with detailed and reduced chemistry are numerically studied with an intention of application to acoustic instabilities of rocket engines. The numerical results of extinction strain rate for undiluted hydrogenoxygen flames are found to be qualitatively different from those for hydrogen-air flames in that extinction strain rate for undiluted hydrogen-oxygen flames increases linearly with pressure up to 100 atm whereas extinction strain rate for hydrogen-air flames saturates around 50 atm. Comparison of the characteristic flow time with the characteristic chemical time shows that extinction strain rate varies linearly with pressure for flames controlled by two-body chain-branching reactions that are found to be dominant up to 100 atm. The four-, three-, and two-step reduced mechanisms are also tested to exhibit that the linearity of the extinction strain rate with pressure is preserved. Based on these results, the asymptotic methods, previously used in low-pressure hydrogen- air flames, can be extended to predict the asymptotic structure of hydrogen- oxygen flames at high pressures. On the other hand, the fall-off effect and real-gas effect are found to be minimal on extinction characteristics. Since the characteristic flow time is estimated to be several orders of magnitude shorter than the characteristic acoustic time in rocket engines, acoustic responses are satisfactorily reproduced from the quasisteady flame structures. Finally, the sensitivity analysis identifies the reaction step, H + O2 + M → HO2 + M as a favorable reaction path to stabilize acoustic oscillations by depressing the reaction rate.

Original languageEnglish (US)
Pages (from-to)299-312
Number of pages14
JournalCombustion and Flame
Volume115
Issue number3
DOIs
StatePublished - Nov 1998
Externally publishedYes

Bibliographical note

Funding Information:
Support of this research was provided for each author as follows: CHS and SHC by the Turbo and Power Machinery Research Center at Seoul National University, SRL in part by a research grant from Seoul National Polytechnic University, and JSK by the Korean Ministry of Science and Technology through Grant No. 2N15900 and by the U.S. Air Force Office of Scientific Research through AFOSR Grant No. F49620-97-1-0098. The authors would like to express their appreciation to Prof. Forman Williams for many helpful comments on the paper as well as for the partial support to JSK.

ASJC Scopus subject areas

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

Fingerprint

Dive into the research topics of 'Structure and acoustic-pressure response of hydrogen-oxygen diffusion flames at high pressure'. Together they form a unique fingerprint.

Cite this