Numerical Investigation of the Performance Characteristics in a Radial Disc Micro-Combustor for Various Geometrical and Operating Conditions

The present study is a numerical investigation on the Hydrogen-air premixed combustion in a micro disc- radial burner with an annular step of curved profile. Micro disc-radial burner with a curved-in annular step with diameters of 0.5mm., 0.625mm and 0.75mm are considered in this study. Average combustion efficiency and upper wall temperature are used as metric to quantify the combustion and heat transfer performance of the micro-burner. The average combustion efficiency in the micro-disc burner is observed to monotonously decrease with increase in inlet velocity. The results show that the effect of the inlet velocity on the average upper wall temperature is non-monotonous. The average upper wall temperature decreases with the initial increase in the inlet velocity to reach a minimum. However, further increase in the inlet velocity is observed to increase the average upper wall temperature for all the curved-in step burners. Also, the increase in the inlet velocity is noticed to result in the micro-disc burner to exhibit more uniform upper wall temperature. The curved-in step is observed to result in a significant drop in the outer-wall temperature compared to the burner with a conventional step. An increase in the diameter of the curvature is observed to cause a further drop in the average upper wall temperature. The average combustion efficiency is also noticed to decrease for the curved-in step burners. The adverse effect of the curved-in step on the combustion performance could be attributed to the downstream movement of the point of reattachment of the fluid separated at the step with the combustor wall.