Heat transfer and entropy production evaluation on premixed hydrogen/air-fuelled micro-combustors with internal threads

Abstract

A micro-combustor with a tailored internal thread is proposed to uniform the wall temperature and improve the second law efficiency of a micro thermophotovoltaic (MTPV) system. The influences of 1) the thread form, 2) the inlet velocity and 3) the nominal diameter on the system’s thermal performances are investigated by performing computational fluid dynamics simulations. Results indicate that the application of the proposed corrugated thread structures can reduce the flame temperature and enhance heat transfer remarkably. The recirculation zone formed in the spiral grooves is conducive to obtaining uniform temperature on the outer combustor surface. Especially when the inlet velocity increases to 5 m/s, the standard deviation of the wall temperature can be maintained below 20 K. In addition, the mean wall temperature and the standard deviation of the wall temperature both increase distinctively with the increase of the nominal diameter. Entropy production is the analysed for the tested combustors with different thread forms. Moreover, the second law efficiency of a triangular thread is above 65%, while the entropy production from the chemical reaction and heat conduction proceses contribute more than 90%. The present work provides a new design of the internal structure for optimizing micro-combustors performances.