Numerical investigation on thermal performance improvement of hydrogen-fueled tube with rib/fins for micro thermophotovoltaic

Combustion characteristics and thermal performance of pre-mixed hydrogen/air in micro tubes for micro-thermophotovoltaic are conducted under various operating conditions. To improve flame stability and energy efficiency, a cylindrical stepped tube with rib/fins is proposed. Effects of burner optimization on hydrogen-fueled flame regime, heat transmission and thermal performance are numerically conducted, which is verified by experimental tests. The results illustrate that the inserted rib and its location strongly modify the anchoring and propagation of premixed H2/air flame, resulting in the improvement of heat transfer and radiation temperature. Furthermore, the employment of outlet-fins modifies the flow field and enhances heat recirculation by utilization of hot exhausted gases. There exists a balance between the radiation temperature reduction and the radiation surface augment via the increment of chamber length. Meanwhile, the influence grades of chamber length, flow rate, outlet-fins number and rib position are ranked in turn based on the grey relational analysis. So, electrical power of combustor C33-7-10 is 0.77 W higher than that of stepped tube for a micro-TPV with InGaAsSb at mf = 5.10 x 10-5 kg/s, and it obtains a higher power output of 2.22 W at mf = 8.16 x 10-5 kg/s. It can also be further improved by the flow rate increment and employment of high efficiency PV cells.