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Irreversible entropy production rate in high-pressure turbulent reactive flows

Borghesi, Giulio and Bellan, Josette (2015) Irreversible entropy production rate in high-pressure turbulent reactive flows. Proceedings of the Combustion Institute, 35 (2). pp. 1537-1547. ISSN 1540-7489.

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A Direct Numerical Simulation (DNS) database is created describing high-pressure reactive flows for studying the flow characteristics and the irreversible entropy production rate that must be modeled by Subgrid-Scale (SGS) models in Large Eddy Simulation. The governing equations are the continuity, momentum, total energy and species transport equations complemented by a real-gas equation of state. The molecular transport model is based on complete mass-diffusion and thermal-diffusion matrices having elements computed according to all-pressure mixing rules. The mixture viscosity and thermal conductivity are calculated from the individual species values, valid at high pressures, by using all-pressure mixing rules. The reaction is a one-step process and the values of different coefficients in the reaction rate ensure that it gives physically-correct trends for autoignition. The DNS is performed for a temporal mixing layer. Three realizations are computed and examined to reveal the influence of the initial pressure p_0 and of exhaust gas recirculation (EGR). It is found that the main flame is of diffusion type, flanked by premixed flames. As p_0 increases, the most intensive premixed-flame regions draw closer to the diffusion flame. Additionally to the well-known advantage of EGR, we found that it promotes the development of uphill diffusion which is a molecular process inducing the formation of strong species gradients that in turn induce turbulence production, i.e. the formation of dynamic small scales. Analysis of the irreversible entropy production rate revealed that its four modes – due to viscosity, mass diffusivity, thermal conductivity and reaction – operate in different spatial regions of the flow where different phenomena occur. Increasing p_0 and lack of EGR both result in an increase in the magnitude of the irreversible entropy-production rate. For the Reynolds number values achievable in DNS, the reaction mode dominates in magnitude all other modes of the irreversible entropy-production rate.

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Additional Information:© 2014 The Combustion Institute. Published by Elsevier Inc. Available online 21 June 2014. This study was conducted at the Jet Propulsion Laboratory (JPL), California Institute of Technology (Caltech) and sponsored at Caltech by the Department of Energy, Basic Energy Sciences under the direction of Drs. W. Sisk and M. Pederson. We acknowledge Dr. N. Okong’o for deriving this form of the irreversible entropy production rate expression when reaction is present.
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Department of Energy (DOE)UNSPECIFIED
Subject Keywords:High-pressure turbulent reacting flow; Direct Numerical Simulation
Record Number:CaltechAUTHORS:20171019-102122597
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Official Citation:Giulio Borghesi, Josette Bellan, Irreversible entropy production rate in high-pressure turbulent reactive flows, In Proceedings of the Combustion Institute, Volume 35, Issue 2, 2015, Pages 1537-1547, ISSN 1540-7489, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:82487
Deposited By: Tony Diaz
Deposited On:19 Oct 2017 18:03
Last Modified:19 Oct 2017 18:03

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