Study of swirling recirculating hydrogen diffusion flame using UV Raman spectroscopy

Abstract

Raman/Rayleigh scattering is used to measure temperature and major species concentrations in a swirling recirculating hydrogen diffusion flame in air and a corresponding nonreacting flow. Mean and fluctuation statistics are reported. Laser-Doppler Velocimetry (LDV) is used to determine properties of the flow field. The main difference between reacting and nonreacting flow is the decreased centerline decay of mixture fraction in the former case, a shortened and broadened recirculation zone, and higher root mean spare (rms) fluctuations of the mixture fraction. Conclusions drawn from the results confirm that the effect of combustion heat release on the turbulent mixing process is considerable. The width of the flow structure based on mixture fraction is found to be approximately linear with axial distance up to the second stagnation point. Results demonstrate the significant influence of buoyancy in the recovery region down-stream of the recirculation zone. Finite-rate chemistry effects result in a temperature well below the adiabatic equilibrium value where the calculated Damkohler number is less than unity at the upstream end of the recirculation zone. A progress variable is defined to describe the departure from chemical equilibrium. The mean progress variable at radial locations with identical mixture fraction is found to be different, depending on its relative position to the recirculation zone.