Effect of Physical Parameters on Thermal Behavior of Microcombustor

Abstract

A numerical study on methane/air combustion inside a microchannel was undertaken to investigate the effects of inlet velocity, equivalence ratio, and convective heat transfer coefficient on combustion characteristics. The simulation results show that the inlet velocity has a strong influence on the reaction zone, and the flame front shifts downstreamastheinletvelocityincreases.Theinfluenceofinletvelocityonconvectionheattransferbetweenmixture and walls is significant and the temperature difference between mixture and walls in the inlet section increases with the inlet velocity first to a certain value and then decreases. The equivalence ratio is a key parameter that affects the combustion characteristics. The highest flame temperature is obtained if the equivalence ratio is set at 1.0. The reaction rateof the equivalence ratio equal to 0.8 is largerthan that of the equivalence ratio equal to 1.0and 1.2.The steady flame cannot be obtained with a 0.6 equivalence ratio and 0:5 m=s inlet velocity. However, when the inlet velocity is increased to 0:7 m=s, a steady flame is observed. The convective heat transfer coefficient shows a very strong influence on combustion characteristics. With the increase of heat transfer coefficient on external walls, the wall temperature and downstream fluid temperature decrease. However, the influence is weakened at the inlet section. No oscillatory behavior is observed when the heat transfer coefficient is less than 50 W=m 2 K and the steady flame cannot be obtained if the heat transfer coefficient is set at 100 W=m 2 K.