Piloted jet flames of CH4/H-2/air: Experiments on localized extinction in the near field at high Reynolds numbers
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abstract
Measurements of temperature and major species concentrations, based on the simultaneous line-imaged Raman/Rayleigh/CO-LIF technique, are reported for piloted jet flames of CH4/H2 fuel with varying amounts of partial premixing with air (jet equivalence ratios of {symbol}j = 3.2, 2.5, 2.1 corresponding to stoichiometric mixture fraction values of st = 0.35, 0.43, 0.50, respectively) and varying degrees of localized extinction. Each jet flame is operated at a fixed and relatively high exit Reynolds number (60,000 or 67,000), and the probability of localized extinction is increased in several steps by progressively decreasing the flow rate of the pilot flame. Dimensions of the piloted burner, originally developed at Sydney University, are the same as for previous studies. The present measurements complement previous results from piloted CH4/air jet flames as targets for combustion model calculations by extending to higher Reynolds number, including more steps in the progression of each flame from a fully burning state to a flame with high probability of local extinction, and adding the degree of partial premixing as an experimental parameter. Local extinction in these flames occurs close to the nozzle near a downstream location of four times the jet exit diameter. Consequently, these data provide the additional modeling challenge of accurately representing the initial development of the reacting jet and the near-field mixing processes. 2009 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
