Reaction zone weakening effects under hot and diluted oxidant stream conditions

Paul R. Medwell, Peter A.M. Kalt, Bassam B. Dally

Research output: Contribution to journalArticlepeer-review

57 Scopus citations


This paper reports computational results, to complement experimental observations, on the turbulence-chemistry interaction of nonpremixed jet flames issuing into a heated and highly diluted oxidant stream. It is found experimentally that large-scale vortices and flame stretch can lead to spatial thinning and a decrease in OH concentration. This reduction in OH is described as a weakening of the reaction zone. Accompanying reaction zone weakening is also an increase in H2CO levels. The reduction in reaction rates is most noticeable at low oxidant stream O2 levels. The heated and low oxygen oxidant conditions typify those of moderate or intense low oxygen dilution (MILD) combustion. The computational results indicate that the effects of the low oxygen levels of MILD combustion leads to both a reduction in reaction rates and an increase in transport of O2 across the reaction zone. The relationship between the reaction rate and level of O2 permeation suggests that a form of partial premixing can occur under MILD combustion conditions. This partial premixing leads to the formation of flame intermediates, which contribute to the stabilization of the flames. The permeation effects are most pronounced at high strain rates, which are commonly encountered in practical MILD combustors.
Original languageEnglish (US)
Pages (from-to)937-953
Number of pages17
JournalCombustion Science and Technology
Issue number7
StatePublished - Jul 1 2009
Externally publishedYes

Bibliographical note

Generated from Scopus record by KAUST IRTS on 2022-09-12

ASJC Scopus subject areas

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


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