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首页> 外文期刊>Combustion and Flame >Contributions of flame thickening and extinctions to a heat release rate marker of intensely turbulent premixed hydrogen-enriched methane-air flames
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Contributions of flame thickening and extinctions to a heat release rate marker of intensely turbulent premixed hydrogen-enriched methane-air flames

机译：Contributions of flame thickening and extinctions to a heat release rate marker of intensely turbulent premixed hydrogen-enriched methane-air flames

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摘要

Influences of the reaction zone thickening and extinctions on a heat release rate marker of extremely turbulenthydrogen-enriched methane-air flames are investigated using simultaneous planar laser-inducedfluorescence of formaldehyde molecule and hydroxyl radical as well as separate stereoscopic particle imagevelocimetry techniques. The fuel-air equivalence ratio is set to 0.7, and the amount of hydrogenenrichmentvaries from 0 to 70 by volume. Mean bulk flow velocities ranging from 5 to 35 m/s withReynolds and Karlovitz numbers of 18 to 2729 and 0.1 to 76.0, respectively, are examined. It is shown that,by increasing the turbulence intensity, the preheat and reaction zone thicknesses can increase to valuesthat are, respectively, 6.3 and 4.9 of the corresponding laminar flames, which were measured experimentally.Broadening of these zones for intensely turbulent hydrogen-enriched methane-air flames is shownexperimentally for the first time. Broadening of the reaction zone suggests that the flamelet assumptionused for development of the turbulent flame speed formulations may not hold. Thus, a new formulation,which does not utilize the flamelet assumption, is developed and used to calculate a heat release ratemarker of the tested flames. It is shown that, at small turbulence intensities, the heat release rate markervalues follow those of the local consumption speed, which is developed in the literature based on theflamelet assumption. However, at large turbulence intensities, the estimated heat release rate marker featureslarge values, and the ratio of this parameter to the local consumption speed is consistent with theratio of the global and local consumption speeds reported in the literature. It is shown that the ratio ofthe normalized heat release rate marker to the normalized local consumption speed is correlated withthe broadening of reaction zone, suggesting that the disparity between the values of the heat release ratemarker and the local consumption speed is linked to the reaction zone thickening. It is shown, althoughthe flame thickening increases the heat release rate marker, extinctions decrease this parameter, whichmay contribute to the characterized bending behavior. It is argued that the amount of bending is relatedto the inverse of the Damk?hler number. Using this, a mathematical formulation that allows for estimationof the heat release rate marker is developed. The predictions of the proposed formulation agree wellwith the normalized global consumption speeds of past experimental investigations.

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