Experimental Studies on Recuperative Micro-Combustion Chamber for 1 W Gas Turbine Engine

Abstract

Experimental investigations are carried out on recuperative micro-combustion chamber for 1 W gas turbine engine. The combustion chamber under consideration is of Swiss Roll type. The micro-combustion chamber is operated at ultra-lean premixed hydrogen air mixture. The central reaction zone volume is 3 mm × 4 mm × 5 mm, with reactant and product passages coiled around. The reaction cross-sectional passage has inlet of 0.6 mm × 5 mm, while the product cross-sectional passage is of 1.5 mm × 5 mm. The heat loss due to small size is virtually eliminated as reactant passages are coiled around product passage. The reactants are thus pre-heated by the heat loss to the walls by the product of combustion. Velocity reduction is achieved by dumping the reactants in the central reaction zone. The cross-sectional area is increased of reactant passage from inlet to central reaction zone, thereby reducing the velocity in the reaction passage. This increases the residence time and helps in achieving stable combustion. The micro-combustor is experimented by varying the equivalence ratios from very lean condition of 0.12 to near stoichiometry. The results suggest that the combustor performance deteriorates above equivalence ratio of 0.52, in terms of NOx emissions. The generation of hot spots becomes evident after equivalence ratio of 0.43. Above equivalence ratio of 0.43, the flame front extends to the product passage, giving very high temperatures, leading to reactants being heated to self-ignition temperature.