LaminarTriple Flames in Partially Premixed Opposed Flows

Abstract

Presented is an asymptotic analysis of premixed laminar flames in opposed streams under circumstances of fast chemistry and/or low rates of strain and of high Reynolds numbers. In this case there exist three distinct reaction layers, two premixed and one nonpremixed, the latter centered on the stagnation plane. These layers separate inviscid, chemically inert regions with constant gas properties. The state variables in each region are determined by the reactants exiting from each jet. If the location of the two premixed reaction layers is known, the velocity distributions in the four regions can be readily calculated. An activation energy analysis of the structure of the two premixed reaction layers determines the Damköhler parameter associated with their locations. Comparison of the asymptotic analysis is made with a recently reported large scale computation of triple flames. Agreement with the distributions of the velocity components is satisfactory; however, as a consequence of the idealized chemistry treated here the temperature distributions in the two high temperature regions are only roughly correct. The analysis shows the influence of changes in jet velocities and equivalence ratio of the fuel rich reactant stream on the location of the premixed reaction layers and on the velocity distributions. The former changes establish the limiting behavior of triple flames corresponding on the one hand to the premixed reaction layers being in the neighborhood of the exit planes and on the other lo all three layers being embedded in a viscous layer centered on the stagnation plane.

Keywords:

• Triple flames
• reaction layers
• planes

Additional information

Notes on contributors

P. A. LIBBY

e-mail: [email protected]