Scalar Dissipation Rate in a Planar Liquid Jet with a Chemical Reaction (Experimental Study on the Evaluation of the Conditional Moment Closure Equation)

Abstract

Conditional scalar dissipation rate <N | ξ = η> conditioned on a mixture fraction ξ and mean scalar dissipation rate <N> in a planar liquid jet are experimentally investigated. Streamwise velocity and reactive concentrations are simultaneously measured in the planar liquid jet with a second-order chemical reaction A+B→R. <N | η> on the jet centerline is obtained from a conditional moment closure (CMC) equation and measured conditional mean values. To calculate <N | η>, we derive the equations which represent conditional mean concentrations by assuming that the ratio of the conditional mean concentration of product R and the conditional mean reaction rate does not depend on the mixture fraction. The conditional dissipation rate is obtained from the budget of CMC equation. The results show that <N | η> becomes small in the downstream direction. It is also shown that the profiles of <N | η> change in the downstream direction; in the downstream region, <N | η> has a local minimum value at η ≈ ξS, where ξS is the stoichiometric ratio in mixture. <N> can be obtained from <N | η> and the probability density functions of mixture fraction. It is observed that <N> on the jet centerline decays in the downstream (x) direction as x-2.9, which is close to the -3 power expected from scaling arguments.