Experimental and numerical study of the wall temperature of cylindrical micro combustors

The micro combustor is a key component of the micro thermophotovoltaic (TPV) system. Premixed combustion of a hydrogen-air mixture in micro combustors with an inner diameter of 2 mm is studied experimentally and numerically. A backward-facing step (s = 0.5 mm) is employed in the cylindrical tube for flame stabilization. The effects of flow velocity, fuel - air equivalence ratio and combustor length on the wall temperature are investigated. Based on the measured wall temperature, the radiation heat flux through the combustor wall is quantified. The experimental results (measurements and direct photos) indicate that the position of the peak wall temperature is nearly localized within a narrow zone (4-6 mm from the step), independent of flow velocity, fuel-air equivalence ratio and combustor length. The combustion flows are numerically modeled by solving the 2D governing equations in both the gas phase and solid phase. The numerical results indicate that at Re > 500 (u(0) = 8 m s(-1)) modeling the turbulence (k-epsilon model) is necessary to ensure good agreement with the experimental values. The numerical model is shown to be applicable over the full span of both flow velocity (8 <= u(0) <= 16 m s(-1)) and fuel-air equivalence ratio (0.6 <= Phi <= 1.0).