CARS Temperature Measurements in a Driven Jet Diffusion Flame

Abstract

This paper discusses the use of a broadband coherent anti-Stokes Raman scattering (CARS) system to investigate local gas temperatures during a vortex/flame interaction. The CARS system is first used to obtain flame temperature measurements in a series of near adiabatic hydrogen/air flames produced with a Hencken burner (Hencken, 1994; Hancock, et al., 1996). These temperatures are compared to adiabatic flame temperatures found using the NASA-Lewis equilibrium code (Gordon and McBride, 1976) and a computational fluid dynamics code developed by Katta, et al. (1994). These results help to validate the CARS system. Next, the CARS system is used to obtain local gas temperature measurements in an undriven hydrogen/nitrogen jet diffusion flame and during a vortex-flame interaction in the same flame, but under driven conditions. Experimental results (Hsu, et al., 1993; Carter, et al., 1995) and direct numerical simulations (Katta and Roquemore, 1995) indicate that preferential diffusion (manifest as Lewis number), acting together with flame curvature, influence the local flame temperature along the flame surface. Under certain conditions the local temperature will rise even though the flame is positively stretched-a condition which is typically thought to cause a reduction in local flame temperature. In this paper such a condition is investigated for a hydrogen/nitrogen diffusion flame using CARS and direct numerical simulations.