Accession Number : ADA300073

Title :   Large Eddy Simulation of Backward-Facing Stop Flow with Application to Coaxial Jet Combustors.

Descriptive Note : Final technical rept. 1 Oct 91-30 Nov 94,

Corporate Author : STANFORD UNIV CA DEPT OF MECHANICAL ENGINEERING

Personal Author(s) : Moin, Parviz

PDF Url : ADA300073

Report Date : FEB 1995

Pagination or Media Count : 369

Abstract : Large eddy simulations (LES) have been performed for two massively separated flows: a planar backward-facing step and a coaxial jet combustor. The backward-facing step case was used to develop and validate both the numerical method and the subgrid-scale model. Backward-facing step simulations were performed at Reynolds numbers 5100 and 28000. Both cases agree well with experimental data; the low Reynolds number case is also in excellent agreement with DNS data. Two versions of the dynamic subgrid-scale model as well as the classical Smagorinsky model were tested and little difference was found among them. The coaxial jet combustor simulations were used as a first step to study the flame stability problem known as lean blow-out. The study focused on the entrainment and mixing of fuel and air within the combustion chamber, using a passive scalar tracking technique. Chemical reactions and the effects of heat release were ignored in this initial study. Mean statistics at Reynolds number 38000 are in good agreement with experimental data. A motion picture of the unsteady motion revealed intermittent pockets of fuel-rich fluid crossing the annular air jet and becoming entrained in the recirculation zone. A larger source of entrainment, however, was found to be the upstream redirection of the fuel jet near the instantaneous impingement point on the combustor wall.

Descriptors :   *EDDIES(FLUID MECHANICS), *COMBUSTORS, *COAXIAL CONFIGURATIONS, *REYNOLDS NUMBER, SIMULATION, SOURCES, STABILITY, EXPERIMENTAL DATA, AIR, STATISTICS, TRACKING, PASSIVE SYSTEMS, TURBULENCE, FUELS, CHEMICAL REACTIONS, TUNING, SELF OPERATION, COMBUSTION CHAMBERS, WALLS, MIXING, SCALAR FUNCTIONS, MEAN, FLAMES, NUMERICAL METHODS AND PROCEDURES, HEAT, LOW RATE, JET FLOW, ENTRAINMENT, EDDY CURRENTS, FORMULAS(MATHEMATICS), RECIRCULATION, IMPINGEMENT, ANNULAR NOZZLES.

Subject Categories : Fluid Mechanics
      Combustion and Ignition

Distribution Statement : APPROVED FOR PUBLIC RELEASE