Study on the non-premixed combustion characteristics and exergy analysis of H2/Air in vase-shaped micro combustor

Abstract

The micro thermophotovoltaic system (MTPV) based on H2/Air combustion has the advantages of high energy density, long-lasting and small-scaled. However, there are still some challenges in combustion stability and safety due to short residence time, large heat dissipation, and flashback. For this reason, a non-premixed micro-combustor with tangential inlet and vase shape is proposed in this paper. The tangential inlet can replace the swirler to form a swirling flow and the vase-shaped channel is designed as a gradual expansion and shrinking tube. The effects of the tangential inlet, equivalence inlet velocity, and key parameters of structure on non-premixed combustion characteristics were numerically studied. The energy transfer path and exergy efficiency were analyzed. The results showed that the vase-shaped micro combustor has a higher blow out limit, and much greater exergy and exergy efficiency than the conventional combustor. With the increase of equivalence inlet velocity, the exergy increases while the exergy efficiency greatly decreases. With the decrease in tangential inlet size, the flame temperature and exergy decreased while the exergy efficiency increased significantly. The tangential inlet can promote the mixing effect in the back-flow region, but the exergy and exergy efficiency decrease. The blow out limit increases with the increase of R3/R1 (maximum channel radius/inlet-1 radius) while the efficiency greatly decreases.