Experimental characterization of combustion in recirculation zone of double-stage swirl chamber

Abstract

Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.

The focus of the present work is a new Low-NOx combustor configuration to especial application in gas turbine. The combustion happens in two phases; the first one with oxidant deficiency, or fuel rich combustion, and the second one is a fuel lean combustion. This combustion structure allows the conciliation of low NOx emissions and partial oxidation combustion products, as carbon monoxide and unburned hydrocarbons. In the new concept proposed here, these unfavorable combustion conditions for NOx formation are reached through the dynamic control of reactants mixing process into the chamber. However, the success of this strategy depends on the formation of a strong recirculation zone in the secondary chamber and quick-mixing between air, reminiscent fuel and combustion products. So that the present work shows experimental results about the structure of the recirculation zone using Particle Image Velocimetry (PIV) and the combustion dynamics using Planar Laser Inducing Fluorescence (PLIF). Both techniques were applied in the secondary zone of combustion. The conclusion based on the results presented in this paper can be summarized according to the increase of the recirculation zone intensity: 1. the volume occupied by recirculation zone is greater, the transition to reverse flow is more abrupt and the magnitude of the reverse velocity is higher; 2. intensify the vortices formation; 3. the combustion reactions take place in the central region of recirculation zone.