Emission Measurements and CH* Chemiluminescence of a Staged Combustion Rig for Stationary Gas Turbine Applications

Abstract

An optically accessible combustion rig was constructed to study the combustion characteristics of a reactive jet in a vitiated crossflow. The rig features two staged combustion zones. The main combustion zone is a swirl stabilized dump combustor. The second combustion zone, which is axially downstream from the main combustion zone, is formed by a transverse jet injecting either fuel or a premixed fuel/air mixture into the vitiated stream. The rig was designed to investigate the transverse jet conditions, equivalence ratio, and momentum ratios that produce low NOx and give an adequate temperature rise before the simulated high pressure turbine. A water-cooled sampling probe extracts exhaust gas downstream for emission measurements. As a baseline, the main combustion zone was fired without the transverse jet and the results compare closely to the work of previous researchers. The emission survey with the transverse jet found several conditions that show a benefit of staging compared to the baseline of firing only the main combustion zone. The flame structure from the transverse jet was captured using high speed CH* chemiluminescence, which shows the extent of the flame front and its penetration depth into the vitiated stream. The chemiluminescence images were averaged and compared to the Holdeman correlation, which showed good agreement for injection with fuel only but poorer agreement when premixed.