ISBN 9783843917971

978-3-8439-1797-1, Reihe Ingenieurwissenschaften

Eirene Rebecca Busch
Investigation of Aerodynamics and Aeroacoustics of Contra-rotating Open Rotors

267 Seiten, Dissertation Universität Stuttgart (2014), Softcover, A5

Zusammenfassung / Abstract

In this thesis, the aerodynamics and aeroacoustics of Contra-Rotating Open Rotors (CRORs) under the variation of operating conditions and geometry modifications are examined by means of numerical simulation. The purpose is to show the potential of noise reduction for highly efficient CRORs, in order to make them applicable for civil aviation.

The process chain for numerical simulation consists of a second-order finite volume solver for aerodynamics and a Ffowcs Williams and Hawkings acoustic solver. It is validated with two propeller models without incoming flow, an advanced turboprop in flight tests and a small-scale CROR model also without incoming flow.

The investigation of the CROR focuses on different operational conditions and parameters such as inflow Mach number, rotational velocity, blade pitch angles, and rotor-rotor distance. Furthermore, the potential of geometry variations including the blade numbers, the blade tip geometry, and the rotor diameter of the rear rotor is examined. The same blade geometry is used for the variation of operational conditions and blade numbers allowing an assessment of the influencing factors on noise emission.

The potential of noise reduction by the right choice of operating conditions and geometry modification is shown. However, for a good performance, further modifications are necessary. For the single rotor noise, a steep decrease of thrust at the blade tip in combination with a small rotational frequency and a high pitch angle is beneficial. To reduce the interaction noise, the blade-vortex-interaction must be avoided.