Relationship between local reaction rate and flame structure in turbulent premixed flames from simultaneous 10 kHz TPIV, OH PLIF, and CH2O PLIF

This work experimentally quantifies the relationship between metrics of the local reaction rate and flame thickness for turbulent premixed flames in the corrugated flamelet and thickened preheat zone/thin reaction zones regime using data from simultaneous 10 kHz tomographic particle image velocimetry (TPIV), hydroxyl planar laser induced fluorescence (OH PLIF), and formaldehyde (CH2O) PLIF. Two reaction rate metrics are presented, which are based on tracking fluid elements in a Lagrangian manner as they traverse from the flame leading edge to the reaction zone. This yields both a fluid residence time in the flame (tau(c)) and a metric of the flame speed (S). tau(c) in the thickened preheat zone regime was reduced by nearly 40% compared with the corrugated flamelet despite the flame being broader, indicating a substantial increase in the local reaction rate. The joint PDFs of S and local flame thickness showed a positive linear correlation between these quantities, which can be explained by turbulent diffusivity arguments. These data provide guidelines for reaction rate models, as well as a quantitative means of comparing local behavior between experiments and simulations. (C) 2016 by The Combustion Institute. Published by Elsevier Inc.