The Influence of Various Exhaust Geometrical Parameters on the Effectiveness of an Aero-Engine Intake Thermal Anti-Icing System

Abstract

Anti-icing air from the internal nose cowl regions of aircraft engines exits via an exhaust slot to join the engine intake air upstream of the compressor. It is important that this still hot air be used efficiently downstream of the exhaust slot to effect heating of the downstream surface (acoustic liner) to facilitate the prevention of ice build-up at this point. To this end, various exhaust slot geometry designs have been investigated in an experimental study to provide guidelines to assist in this aim. The most significant variables were found to be assembly length, slot depth, exit plane width and exhaust angle. Surface heating effectiveness does not appear to be affected by “blowing ratio” differences between exhaust geometries. Equations are derived and suggested to predict the skin temperature decay downstream of the exhaust slot for a range of “blowing ratios” but the benefits in anti-icing performance must be considered ultimately against weight, cost, reliability, maintenance factors and in-service experience.