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. ©2013 The Japan Society of Mechanical Engineers.