Influence of near-leading edge curvature on the performance of aero-engine intake lips at high-incidence

Abstract

This paper describes the investigation into the flow over the lip of subsonic engine intakes at incidence, focusing on the shock wave-boundary layer interaction occurring over the inner lip. A baseline geometry is considered along with two variations, characterised by a sharper and a blunter intake highlight (i.e.: nacelle leading edge) respectively. Results to date reveal a relatively benign interaction for the baseline model, with small or no shockinduced separation reported under on-design conditions, which correspond to typical takeoff or climb circumstances. The alternative geometries reveal a considerable influence of near-highlight curvature on the flow development. In particular, a blunter nose leads to the formation of a larger supersonic region, terminated by a consequently stronger shock, which shows a greater degree of shock-induced separation and increased total pressure losses and unsteadiness. The sharp nose, on the other hand, resulted in the compression occurring via three separate shock-waves, all of which weak. Overall, none of the three intake geometries showed inherently unsteady behaviour. However, this is expected to occur as the engine flow demand increases. Further testing is in progress to assess off-design performance and to produce a complete operational envelope for intakes at incidence.

The Impact of Surface Roughness Geometry on Aero-Engine Intakes at Incidence

“…The upper wall of the working section is designed to be far enough away from the intake model to prevent choking in the upper channel. 1 The overall mass flow rate into the working section,ṁ entry , and the incoming Mach number, M entry , are set by the downstream throat aerofoil and the stagnation pressure in the settling chamber. These are both identified in Fig.…”

“…Previous measurements for this set-up have confirmed the free stream turbulence levels to be less than 1%. 1 The on-design operating condition is listed in table 1. This condition closely mimics a target flow provided by Rolls-Royce from both experimental and computational results based on a real intake at incidence.…”

“…Previous studies, such as those by Coschignano, 1 have investigated purely smooth nacelle surfaces at different operating conditions. However, surface roughness could be presented to the flow in a variety of ways.…”

Onset of unsteadiness in aero-engine intakes at incidence

“…To address this shortcoming, Cambridge University has started experimental research into this problem. The first stage of this research investigated the flow field occurring during typical take-off or climb conditions and found the shock-boundary interaction to be relatively benign, 2 with separated flow confined to small regions of space. However, aeroengine intakes are designed to operate over a wide range, defined by inflow speed, incidence and engine demand.…”

Numerical Modelling of Shock Wave Boundary Layer Interactions in Aero-Engine Intakes at Incidence

“…The rig is designed with the aim of finding a simple geometric configuration that replicates the key physics found in a real intake at incidence, allowing study of such phenomena and providing experimental validation data sought for by computational models. The intake rig was designed and built by fellow PhD student Tafara Makuni [15,21] and experimental measurements used in this work were made by fellow PhD student Andrea Coschignano [23,24], both under the supervision of Professor Holger Babinsky at the Department of Engineering, University of Cambridge. The motivation for this study and the experimental effort is driven by a lack of previous research both experimentally and computationally that investigates transonic high incidence lip flows found in intakes at incidence (as found in the literature review).…”