Flow Field and Structure of Turbulent High-Pressure Premixed Methane/Air Flames

Abstract

The present study focuses on the flow field characterization of highly turbulent premixed flames, typical for stationary gas turbines. Mean flame front position and flame front structure at high inlet temperatures, lean mixtures, and high pressures are studied, too. Turbulence intensities and integral length scales have been measured in an isothermal flow field with the help of Particle Image Velocimetry (PIV). Mean flame front position and flame structure have been studied using Planar Laser-Induced Fluorescence (PLIF) of the OH radical. Turbulence intensities and integral length scales have been measured for different turbulence generating grid geometries and operating conditions. The results show that the combustor flow field can be divided in a region close to the combustor head, where grid-generated turbulence is dominant, and a region further downstream, strongly influenced by turbulence generated in the shear layer. In general the measured turbulence intensity scales well with the bulk velocity. For a systematic variation of the turbulent Reynolds number, Damko¨hler number, and Karlovitz number the mean flame front position and the flame front structure were investigated. Increasing the pressure and thereby mainly increasing the turbulent Reynolds number only slightly affects the mean flame front position but increasingly corrugates the flame front. Increasing the bulk velocity and thereby the turbulence intensity does not affect the mean flame front position but due to the higher turbulence the flame front is increasingly corrugated.