The Design of Axisymmetric Cowls for Podded Nacelles for High By-pass

Abstract

The Report describes a research programme undertaken at ARA in 1968-73. It represents the first attempt in the UK to design forecowl profiles for a podded engine nacelle of modern proportions, with the specific aim of obtaining favourable supercritical flow development over the cowl exterior. Six cowl shapes were tested, of empirical design but exploiting the 'peaky' pressure distribution principle previously evolved for high speed aerofoils. Earlier results for NACA I-series cowls were used as a basis of comparison though all the present cowls had larger lip radii than NACA 1-series cowls in order to improve the low speed performance in conditions that might correspond to a windmilling engine in single-engine flight of a twin-engined transport. The essential measurements were of mass flow, drag (by wake traverse) and surface pressure distributions.