Experimental and numerical studies on heat recirculated high intensity meso-scale combustor for mini gas turbine applications

Micro or meso-scale combustors usually operate with premixed combustion due to restricted space available to allow the mixing of fuel and air. In the present study, a recuperative meso-scale non-premixed combustor is developed for mini gas turbine applications. Experimental and computational analyses are performed to design this meso-scale combustor. An annular heat exchanger is provided around the combustion chamber. The heat exchanger consists of eight longitudinal fins. Air at room temperature enters into the heat exchanger and absorbs the heat. Preheated air enters in the combustor through eight holes and fuel enters through central tube. Initially, the computational analysis is carried out to design the combustor for different thermal inputs ranging from 0.2 to 1.0 kW and range of equivalence ratios of ϕ = 0.25 to 1.4. Non-premixed combustion calculations are conducted with the Reynolds Stress turbulence model coupled with the β-PDF equilibrium along with mixture fraction transport combustion model. Based on the computational analysis, the combustor is built and tested. The design methodology of the combustor, reactants flow patterns and heat transfer characteristics of annular heat exchanger are reported in the present study. Preheat temperature of the air, combustor exit temperature and the emissions from the combustor exit are measured and analyzed. Results show that the stable combustion is achieved with high thermal intensity and ultra-low emissions.