Combustion Characteristics of a Peripheral Vortex Reverse Flow Combustor With Coaxial Fuel Injection

This paper deals with an experimental investigation of a novel and simple reverse flow combustor, operated stably with a liquid fuel (ethanol) for heat release intensities ranging from 16 to 25 MW/(m³·atm) with very low NO_x and CO emissions. The liquid fuel is injected coaxially with the air jet along the centerline of the combustor. The high velocity air annulus helps in primary breakup of the liquid fuel jet. Air injection along the combustor centerline results in a strong peripheral vortex inside the combustor leading to enhanced product gas recirculation, internal preheating of the reactants, and stabilization of reaction zones. Single-digit NO_x emissions were obtained for both coaxial fuel injection (non-premixed) and a premixed–prevaporized (PP) cases for all operating conditions. CO emissions for both the modes were less than 100 ppm (ϕ < 0.75). CH* chemiluminescence images revealed two distinct flame structures for coaxial fuel injection case. A single flame structure for PP case was observed extending from the injector exit to the bottom of the combustor. The instantaneous (spatially averaged) CH* intensity fluctuations were significantly lower for the PP case as compared to the coaxial fuel injection case.