Effect of pins and exit-step on thermal performance and energy efficiency of hydrogen-fueled combustion for micro-thermophotovoltaic

Abstract Micro thermophotovoltaic system, a chemical energy to electrical output device, has been challenged for application because of burning instability, high heat loss ratio and low energy conversion efficiency. A combustor coupling with pins and exit-step configurations is developed to improve system performance. Effects of pins arrangement and exit-step length on the combustion characteristics and thermal performance are investigated with the eddy-dissipation concept (EDC) model and detailed H2/air combustion mechanism. The results indicate that the premixed flame anchors at combustor upstream near the smaller pins where favorable ignition conditions are established. Besides, the appropriate exit-step length improves the heat transfer of gas-solid and energy efficiency, where the length ratio of exit-step to combustor δ = 0.66 is the best for reducing exhaust loss. Furthermore, the combustor coupling with pins and exit-step achieves a stable flame, high energy efficiency and thermal performance. For the micro thermophotovoltaic system with the combustor and InGaAsSb PV cells, radiation efficiency 35.6 % and electric output 2.26 W can be obtained, that is, the system efficiency is 18.7 % higher than that of the straight-channel combustor at hydrogen flow rate 3.75 g/h and equivalence ratio Φ = 1.0.