Compact design of planar stepped micro combustor for portable thermoelectric power generation

Abstract

An efficient prototype of a micro power generator with integrated micro combustor has been developed in the present study. The proposed design of the integrated micro-combustor provides high surface temperature with superior temperature uniformity and enhanced flame stability limits, a prerequisite for a thermoelectric power generation system. This novel micro combustor configuration consists of three backward facing steps with a recirculation hole fabricated in a rectangular heating medium of aluminium material. Parametric studies are carried out by varying the mixture inlet velocity, equivalence ratio and coolant flow rate to obtain the optimized operating conditions for maximum power generation. Two thermoelectric modules are mounted on the system operating with liquefied petroleum gas as fuel. A maximum conversion efficiency of 3.3% is obtained at ϕ = 0.95 with a mixture velocity of 7.5 m/s and a load resistance of 4 Ω across the thermoelectric generator. The effect of porous media is investigated to enhance the flame stability limits in the micro combustor. Porous media significantly enhances the upper flame stability limits and maximum conversion efficiencies (3.8%, 4.03%, and 3.73% at ϕ = 1, 0.9 and 0.8 at 10 m/s). A significantly higher power density (∼50% higher than existing systems) of 0.12 mW/mm3 of system volume is achieved. A compact design of the prototype system with high conversion efficiency shows the possibility of its application for various systems requiring portable power for remote, stand-alone, military and aerospace applications.