Experimental and Computational Investigation upon Combustion Characteristics of Liquid Fuel in a Novel Combustor with Hybrid Swirl and Recirculation Bowl.

In the present study, a novel hybrid swirl combustor is designed to reduce the size and complexity of a conventional gas turbine combustor. In this combustor, a dual-swirl pattern is adopted by providing the central vane swirler (45° vane angle) and circumferential tangential injection scheme to achieve higher recirculation of heat and combustion products inside the combustor. Numerical and experimental studies are carried out to understand the flow patterns and combustion characteristics in this high mass-heat interacting environment. Initially, computational studies were carried out to find the optimum geometry for greater recirculation and interaction among the reacting species inside the combustor. Liquid fuel (kerosene) is sprayed into the combustor for two thermal inputs of 25 and 50 kW. Three cases were studied to analyze the effect of bowl recirculation and tangential air inputs in addition to the swirlers. The hybrid swirl, formed by the counter-flow pattern, helps in achieving low and uniform temperature throughout and assists in flame anchoring. The tangential air flow provides a push to the combustion products from the downstream to the central recirculation zone of the combustor. The combined effect of central and tangential swirlers helps in attaining a more distributed combustion. The CO and NO emissions reduced with the use of hybrid swirl.