Experimental Characterisation of the α-Parameter in Turbulent Scalar Flux for Premixed Combustion

Abstract

The α-parameter is a variable appearing in the formulation of the Bray number, a dimensionless term that can be used to predict the behaviour of the turbulent scalar flux as counter-gradient or gradient in premixed combustion. However, the successful application of the Bray number is hampered by poor characterisation of the a-parameter. The results of previous laser-imaging studies of conditional mean velocities in turbulent premixed methane/air and propane/air Bunsen-flames are used to formulate an empirical description of a. The resulting description of a suggests that the behaviour of the scalar flux is dependent on the heal release parameter and the lengthscale ratio, I₁/δ_L, rather than the velocity ratio, U¹/S_L.

Keywords:

• Turbulent Scalar Flux
• Premixed Combustion