Improvement of thermal performance and energy efficiency of micro-thermophotovoltaic with the dual-inlet combustor at appropriate equivalence ratio

Micro-thermophotovoltaic is facing challenge caused by small size, large area-volume proportion and heat loss ratio, reducing the burning stability and output power. So, the dual-inlet combustors with exit-step and porous medium are proposed for micro-thermophotovoltaic system. Effects of equivalence ratio, exit-step and porous medium setting on combustion characteristic and thermal performance are conducted and analyzed. Results demonstrate that 1% air in the second-inlet is conducive to releasing heat of combustion and optimizing wall temperature distribution, where the total equivalence ratio of H2/air keeps 1.0. Furthermore, the exit-step with applicable length and channel height can generate heat recirculation and enhance working performance of micro-combustor, while the employment of porous medium can further enhance heat transmission of gas-wall and boost the radiation temperature Tw. Combustor CP13 with porosity ε = 0.85 obtains the highest average Tw of 1273.9 K at mf = 3.376 × 10-5 kg/s. With the increase of mf, system efficiency of the combustor with porous medium is increased, while that with exit-step reaches the maximum at mf = 4.501 × 10-5 kg/s. The highest output electrical power and efficiency are appeared in combustor CP15 with ε = 0.95 at mf = 5.626 × 10-5 kg/s, that is, 4.2 W and 2.2%.