Spatially resolved heat release rate measurements in turbulent premixed flames.
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Heat release rate is a fundamental property of great importance for the theoretical and experimental elucidation of unsteady flame behaviors such as combustion noise, combustion instabilities, and pulsed combustion. Investigations of such thermoacoustic interactions require a reliable indicator of heat release rate capable of resolving spatial Structures ill turbulent flames. Traditionally, heat release rate has been estimated via OH or CH radical chemiluminescence; however, chemiluminescence suffers from being a line-of-sight technique with limited capability for resolving small-scale Structures. In this paper, we report spatially resolved two-dimensional measurements of a quantity closely related to heat release rate. The diagnostic technique uses simultaneous OH and CH2O planar laser-induced fluorescence (PLIF), and the pixel-by-pixel product of the OH and CH2O PLIF signals has previously been shown to correlate well with local heat release rates. Results from this diagnostic technique, which we refer to as heat release rate imaging (HR imaging), are compared with traditional OH chemiluminescence measurements in several flames. Studies were performed in lean premixed ethylene flames stabilized between opposed jets and with a bluff body. Correlations between bulk strain rates and local heat release rates were obtained and the effects of curvature on heat release rate were investigated. The results show that the heat release rate tends to increase with increasing negative curvature for the flames investigated for which Lewis numbers are greater than unity. This correlation becomes more pronounced as the flame gets closer to global extinction. (c) 2005 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
|Title:||Spatially resolved heat release rate measurements in turbulent premixed flames|
|Keywords:||heat release rate imaging, simultaneous OH and CH2OPLIF, OH chemiluminescence, turbulent premixed flames, flame front curvature, COUNTERFLOW FLAMES, OPPOSED STREAMS, LEWIS NUMBERS, STRAIN-RATE, AIR FLAMES, COMBUSTION, EXTINCTION, TEMPERATURE, METHANE, SIMULATIONS|
|UCL classification:||UCL > School of BEAMS
UCL > School of BEAMS > Faculty of Engineering Science
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