An investigation of premixed H-2/air combustion in a nozzle inlet micro tube has been carried out. The effects of inlet shape on combustion characteristics, flow field, specie distribution and thermal performance are presented and discussed. Also, effects of inlet mass flow rate and equivalence ratio on the entropy generations of combustion in the micro tubes are analyzed. The results show that the mean outer wall temperature and the emitter theoretical radiant efficiency of the nozzle inlet micro tube is higher than that of the straight micro tube. The total entropy generation rate of the nozzle inlet micro tube is lower than the straight micro tube. Moreover, the Inlet 2 and Inlet 3 nozzle inlet micro tube obtain a higher mean outer wall temperature and a lower exergy destruction, which are more appropriate for the application of the micro thermophotovoltaic (TPV) system. (C) 2018 Elsevier Ltd. All rights reserved.