Experimental investigation of flame stability limits of a mesoscale combustor with thermally orthotropic walls

Flame stability limits were experimentally investigated for a parallel plate mesoscale combustor with orthotropic walls. The combustor walls were made of pyrolytic graphite, which has orthotropic thermal conductivity of 350 W/m-K in ab-plane and 3.5 W/m-K in the c-plane at room temperature. Infrared images of the combustor walls showed that the pyrolytic graphite plates had uniform temperature distributions at all operating conditions tested. Compared to an isotropic material (stainless steel), pyrolytic graphite showed a greater high velocity limit (HVL) and thereby wider flame stability limit. Thermal performance of the combustor was also evaluated via an energy balance, wherein, heat losses were found to dominate the thermal fluxes. The uniform temperature profile and the lack of a distinctive “hot spot” in the thermal images of the pyrolytic graphite indicate that it is a suitable combustor material for thermoelectric and thermophotovoltaic power conversion applications. Future work should focus on the thermal management so as to avoid excessive heat losses leading to an improvement in the thermal performance of the combustor.