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Simulation of Premixed Hydrocarbon Flames at High Turbulence Intensities

Citation

Lapointe, Simon (2016) Simulation of Premixed Hydrocarbon Flames at High Turbulence Intensities. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z90V89SW. http://resolver.caltech.edu/CaltechTHESIS:05272016-105842881

Abstract

Turbulent premixed hydrocarbon flames in the thin and distributed reaction zones regimes are simulated using both Direct Numerical Simulations (DNS) and Large Eddy Simulations (LES). A series of DNS is performed to study the transition from the thin reaction zones regime to the distributed reaction zones regime. Differential diffusion effects, distributed burning, and local extinctions are quantified. Different fuels, chemical mechanisms, and equivalence ratios are considered. The fuel Lewis number significantly influences the chemical source terms and turbulent flame speeds. More precisely, simulations with differential diffusion effects exhibit lower mean fuel consumption and heat release rates than their unity Lewis number counterparts. However, the differences are reduced as the reaction zone Karlovitz number is increased. The turbulent reaction zone surface areas increase with the turbulence intensity but aren't strongly affected by fuel, equivalence ratio, chemical mechanism, or differential diffusion. Unsurprisingly, changes in the integral length at a fixed Karlovitz number do not affect the chemical source terms but lead to an increase in flame surface area. Assumptions behind closure models for the filtered source term are then studied a priori using the DNS results. Using the concept of optimal estimators, it is shown that a tabulation approach using a progress variable and its variance can predict accurately the filtered progress variable source term. The filtered source terms are compared to predictions from two common presumed sub-filter Probability Density Functions (PDF) models. Both models show deviations from the filtered DNS source terms but predict accurately the mean turbulent flame speed. Finally, LES of experimentally-studied piloted premixed jet flames are performed using tabulated chemistry. Velocity and flame height measurements from simulations and experiments are compared. The LES are in good agreement with the experimental results for the four different hydrocarbon fuels and three different Reynolds numbers simulated. This corroborates that fuel and chemistry effects in turbulent flames are limited to effects present in laminar flames.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Turbulent premixed flames; Direct Numerical Simulations; Large Eddy Simulations; Differential diffusion effects; Distributed burning; High Karlovitz
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Aeronautics
Awards:Richard Bruce Chapman Memorial Award, 2016
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Blanquart, Guillaume
Thesis Committee:
  • Austin, Joanna M. (chair)
  • Blanquart, Guillaume
  • Colonius, Timothy E.
  • Shepherd, Joseph E.
Defense Date:11 May 2016
Funders:
Funding AgencyGrant Number
Air Force Office of Scientific Research (AFOSR)FA9550-12-1-0472
Air Force Office of Scientific Research (AFOSR)FA9550- 12-1-0144
Fonds de Recherche du Quebec - Nature et TechonologiesUNSPECIFIED
National Energy Research Scientic Computing Center (Office of Science of the U.S. Department of Energy)DE-AC02-05CH11231
NSFACI-1053575
Record Number:CaltechTHESIS:05272016-105842881
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:05272016-105842881
DOI:10.7907/Z90V89SW
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/j.combustflame.2015.06.001DOIArticle adapted for ch. 3
http://dx.doi.org/10.1016/j.combustflame.2016.01.035DOIArticle adapted for ch. 4
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9784
Collection:CaltechTHESIS
Deposited By: Simon Lapointe
Deposited On:07 Jun 2016 00:14
Last Modified:14 Jun 2016 18:36

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