Surface micro-grooves for near-wall exergy and flow control: application to aircraft intake de-icing

Abstract

This paper develops a new surface micro-profiling technique for reducing exergy losses and controlling near-wall flow processes, particularly for anti-icing of a helicopter surface. Fabrication of embedded surface microchannels entails surface etching with KOH and XeF2 gas, so that the interspersed microchannels can be assembled into a surface layer of silicon. Testing of the micro-profiled surfaces is performed with particle image velocimetry in a water tunnel. Experimental data indicate that converging open microchannels lead to certain differences of flow patterns on the downstream side of an engine cooling bay. Furthermore, exergy losses for external flow past the parallel embedded microchannels are shown to be lower than previous benchmark results without microchannels. Analytical results are presented for these losses of available energy and exergy destruction. Reduced drag of slip-flow conditions within each microchannel offsets the added friction irreversibility of larger surface area. By altering the near-wall flow patterns, it is anticipated that embedded surface microchannels can provide a useful new approach for dealing with flow-related problems of aircraft icing.