Effect of offset distance on the performance of two-region porous inert medium burners at low thermal power operation

Abstract

A modified technique to improve the performance of the conventional two-region approach used in stabilizing the combustion wave within porous inert media (PIM) burners operating at low power was proposed. This was achieved by detaching the two regions by an adjustable offset distance aiming to control the effects of the various interacted heat transfer mechanisms between the two remoted regions. The validation of this technique was experimentally examined for three offset distances of 13, 26 and 52 mm by comparing its performance with the conventional approach at 1 and 2 kW. The axial temperature distributions were measured versus time for wide ranges of stable and unstable operating conditions. Almost-constant temperature zone was created in the gap between the two regions. The stability limits range was improved by an excess air ratio of 0.2 at 1 kW and 52 mm. At 2 kW, the entire stability diagram was shifted down by an excess air ratio of 0.1 into hotter regime. A tremendous ultra-low CO-emission of ≤1 ppm, beside the ultra-low NOx-emissions of ≤2 ppm, was obtained. The CO-emission was significantly reduced with the offset distance. This may solve the high CO-emission experienced with the conventional PIM burners operating at low power.