Reaction Zone Weakening Effects under Hot and Diluted Oxidant Stream Conditions
- 30 June 2009
- journal article
- research article
- Published by Taylor & Francis Ltd in Combustion Science and Technology
- Vol. 181 (7), 937-953
- https://doi.org/10.1080/00102200902904138
Abstract
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.Keywords
This publication has 28 references indexed in Scilit:
- Conditional moment closure modeling of turbulent nonpremixed combustion in diluted hot coflowProceedings of the Combustion Institute, 2005
- Mild CombustionProgress in Energy and Combustion Science, 2004
- Experimental and numerical analyses of magnetic effect on OH radical distribution in a hydrogen-oxygen diffusion flameCombustion and Flame, 2003
- Advanced low NOx combustion using highly preheated airEnergy Conversion and Management, 2001
- Numerical simulation of a mild combustion burnerCombustion and Flame, 2001
- Combustion of natural gas with high-temperature air and large quantities of flue gasProceedings of the Combustion Institute, 2000
- Reaction zone structure in flameless combustionProceedings of the Combustion Institute, 2000
- Zero-dimensional analysis of diluted oxidation of methane in rich conditionsProceedings of the Combustion Institute, 2000
- Laseroptical investigation of highly preheated combustion with strong exhaust gas recirculationSymposium (International) on Combustion, 1998
- The science and technology of combustion in highly preheated airSymposium (International) on Combustion, 1998