Autoignition of hydrogen in shear flows

Kalbhor, Abhijit and Chaudhuri, Swetaprovo and Chitilappilly, Lazar (2018) Autoignition of hydrogen in shear flows. In: PHYSICS OF FLUIDS, 30 (5).

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Abstract

In this paper, we compare the autoignition characteristics of laminar, nitrogen-diluted hydrogen jets in two different oxidizer flow configurations: (a) co-flowing heated air and (b) wake of heated air, using two-dimensional numerical simulations coupled with detailed chemical kinetics. In both cases, autoignition is observed to initiate at locations with low scalar dissipation rates and high HO2 depletion rates. It is found that the induction stage prior to autoignition is primarily dominated by chemical kinetics and diffusion while the improved scalar mixing imparted by the large-scale flow structures controls the ignition progress in later stages. We further investigate the ignition transience and its connection with mixing by varying the initial wake conditions and fuel jet to oxidizer velocity ratios. These studies reveal that the autoignition delay times are independent of initial wake flow conditions. However, with increased jet velocity ratios, the later stages of ignition are accelerated, mainly due to enhanced mixing facilitated by the higher scalar dissipation rates. Furthermore, the sensitivity studies for the jet inwake configuration showa significant reduction in ignition delay even for about 0.14% (by volume) hydrogen dilution in the oxidizer. In addition, the detailed autoignition chemistry and the relative roles of certain radical species in the initiation of the autoignition process in these non-premixed jets are investigated by tracking the evolution of important chain reactions using a Lagrangian particle tracking approach. The reaction H-2 + O-2 <-> HO2 + H is recognized to be the dominant chain initiation reaction that provides H radicals essential for the progress of subsequent elementary reactions during the pre-ignition stage. Published by AIP Publishing.

Item Type:	Journal Article
Publication:	PHYSICS OF FLUIDS
Publisher:	AMER INST PHYSICS, 1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA
Additional Information:	Copy right of this article belong to AMER INST PHYSICS, 1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA
Department/Centre:	Division of Mechanical Sciences > Aerospace Engineering(Formerly Aeronautical Engineering)
Date Deposited:	27 Jun 2018 17:45
Last Modified:	27 Jun 2018 17:45
URI:	http://eprints.iisc.ac.in/id/eprint/60099

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