14th European Conference on Turbomachinery Fluid dynamics & Thermodynamics

Paper ID:

ETC2021-607

Main Topic:

Vibrations

Authors

Jonah Roy Harris - Imperial College London
Bharat Lad - Rolls-Royce plc.
Sina Stapelfeldt - Imperial College London

Abstract

The increased demands of aggressive modern aero engine architectures have highlighted the problem of outlet guide vane (OGV) buffeting. This structural response to aerodynamic excitations is characterised by increased OGV vibration, risking structural fatigue. Investigations focussed on understanding, mitigation and avoidance are therefore of high priority. This paper seeks to simplify the examination of OGV buffeting by using quasi-2D domains. A 2D simulation environment was constructed by extracting the blade section and mode shape at the mid-span of a proven 3D predecessor. Using URANS simulations this domain was then proven to replicate the desired buffeting behaviour. This validation allowed for parametric studies of factors important to OGV buffeting. These were defined broadly as either geometric or aerodynamic. The geometric study examined the influence of blade curvature and passage area. Here it was discovered that buffeting is uniformly achieved when the steady shock location is shifted beyond the point of maximum curvature. Aerodynamic testing focussed on separating the relative importance of shock movement and the following separation for exciting the 2D mode. Despite the mode shape displacement being biased towards the trailing edge, the shock movement was found to excite the mode more than the separated flow. Finally a lock-in study was completed, confirming that the aerodynamic unsteadiness adjusts its frequency to that of the vibrating structure. Future work will focus on transferring these findings back to the 3D domain, while continuing 2D investigations into multi-passage effects.







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