Jun 27 2018 08:00 AM
Jun 27 2018 09:00 AM
Premixed and Partial Premixed Turbulent Flames at High Reynolds Number
Stefano Luca, Ph.D. Candidate Supervised by Prof. Fabrizio Bisetti
Wednesday, June 27, 2018
08:00 AM - 09:00 AM
LocationAl Kindi Building, Bldg 5, Level 5, Room 5209
Methane/air premixed and partially premixed turbulent flames at high Reynolds number are characterized using Direct Numerical Simulations (DNS) with detailed chemistry in a spatially evolving slot Bunsen configuration. Two sets of simulations are performed. A first set of simulations with fully premixed inlet conditions is considered in order to assess the effect of turbulence on the flame. Four simulations are performed at increasing Reynolds number up to 22400, defined based on the bulk velocity, slot width, and the reactants' properties, using 22 billion grid points, making it one of the largest simulations in turbulent combustion. The simulations feature finite rate chemistry with a 16 species mechanism. The study covers different aspects of flame-turbulence interaction. It is found that the thickness of the reaction zone is similar to that of a laminar flame, while the preheat zone has a lower mean temperature gradient, indicating flame thickening. The characteristic length scales of turbulence are investigated and the effect of the Reynolds number on these quantities is assessed. The tangential rate of strain is responsible for the production of flame surface in the mean and surface destruction is due to the curvature term.
A second set of simulations with inhomogeneous inlet conditions is performed to study how partial premixing and turbulence interact with the flame and with each other. The jet Reynolds number is 5600, and a 33 species mechanism is used. The effect of the inlet fluctuations is reflected on heat release rate fluctuations, however the conditional mean is not affected. The flames show thickening of the preheat zone, and for the lowest level of mixing a slight thickening of the reaction zone is observed.
To perform these simulations, few preliminary steps were required: (i) two skeletal mechanisms were developed reducing GRI-3.0; (ii) a convergence study is performed to select the proper spatial and temporal discretization and (iii) simulations of fully developed turbulent channel flows are preformed to generate the inlet conditions of the jet.
Stefano Luca joined KAUST for Ph.D. in 2014. He has been conducting research under the guidance of Prof. Fabrizio Bisetti since. He received his Bachelor's Degree in Aerospace Engineering in 2010 and his Master's Degree in Space Engineering in 2013 from “La Sapienza”, University of Rome in Italy.