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Aero-acoustic optimization of a swept fan
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
2012 (English)Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

This study deals with the aerodynamics and acoustics of modern transonic fans. Today, three-dimensional design techniques make possible the creation of fan blades with enhanced performance. This project investigates two of these techniques, the sweep and dihedral controls, and their influence on supersonic shock structures and blade performance. Simultaneously, the parameters influencing fan shock noise in the intake are examined.


The first objective is to determine the consequences of a forward sweep on the fan performance. A series of analyses is thus carried out on a typical fan blade in order to assess the effect of a high negative sweep introduced in the tip section. Two blades with the same geometry, except for the tip section which is swept forward, are analyzed at high rotation regimes using CFD methods. The results show that the forward sweep blade has a significantly improved stall margin but an overall lower performance.


In parallel, a CFD analysis is carried out to study the fan’s acoustics. The shock noise, mostly created in the tip section of the blades, is responsible for a large percentage of the noise coming out of the engine during takeoff and cruise. The objective is to understand the propagation of shock noise in the intake and isolate relevant parameters involved in the phenomenon. It is found that the shock noise level emitted is not proportional to the fan speed, as expected. This observation is counterintuitive and leads to search which variables are relevant for the analysis of the phenomenon. The angle the shock makes with the meridional axis is found to be influential on the outgoing noise level as well as the position of the shock on the blade. Finally, a model using the shock angle and aerodynamic variables to predict the noise levels is presented and support the CFD results.

Place, publisher, year, edition, pages
2012. , 31 p.
Keyword [en]
National Category
Aerospace Engineering
URN: urn:nbn:se:kth:diva-126996OAI: diva2:643154
Subject / course
Aeronautical Engineering
Educational program
Master of Science - Aerospace Engineering
2012-03-09, Villaroche, 09:00 (English)
Available from: 2013-10-29 Created: 2013-08-26 Last updated: 2013-10-29Bibliographically approved

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