Mixing Enhancement in a Compact Trapped Vortex Combustor

Abstract

Previous studies on a single-cavity, compact trapped vortex combustor concept showed good flame stability for a wide range of flow conditions. However, achieving good mixing between cavity products and mainstream flow was still a major challenge. In the present study, a passive mixing enhancement strategy of using inclined struts along with a flow guide vane is presented and experimentally tested at atmospheric pressure conditions. Results show excellent mixing and consequently low values of the combustor exit pattern factor in the range of 0.1 and small flame lengths (5–7 times the main-duct depth). The pressure drop is small in the range of 0.35%, and NO_x levels of the order of 1–2 ppm are achieved. The flame stability is excellent, and combustion efficiency is reasonable in the range of 96%. The effectiveness of the proposed strategy is explained on the basis of in-situ OH chemiluminescence images and prior numerical simulations of the resulting complex flow field. The flow guide vane is observed to lead to a counterclockwise cavity vortex, which is conducive to the rise of cavity combustion products along the inclined struts and subsequent mixing with the mainstream flow.

Keywords:

• Compact combustor
• Mixing enhancement
• Struts
• Trapped vortex combustion

ACKNOWLEDGMENTS

This work is supported by Aeronautics Research and Development Board (ARDB), Government of India.