The effect of surface chemistry on the development ofthe [OH] in a combustion boundary layer

Abstract

The development of a combustion boundary layer formed by flowing a lean hydrogen-air mixture (=0.1) over a high temperature (1170K) flat plate has been investigated. Two different plate surface materials were studied: platinum and quartz. The OH concentration and temperature were measured respectively by laser induced fluorescence and Rayleigh scattering. The highly non-equilibrium OH concentration profiles were compared with the results of a numerical boundary layer model. The effect of surface chemistry was evaluated with three general surface chemistry boundary conditions: noncatalytic, surface oxidation, and surface oxidation with radical recombination. Near the leading edge of the flat plate the [OH] gradient obtained from the measured profiles for the platinum and quartz surfaces indicated a net OH production. Farther downstream the [OH] profiles were substantially different, with the quartz surface behaving similar to the noncatalytic boundary condition and the platinum surface behaving similar to the boundary condition for surface oxidation with radical recombination.