Research project: Installed turbofan and open rotor noise

Noise and emissions are critical technical issues for civil aircraft engines. Future single rotation propeller and contra-rotating advanced open rotor concepts promise a significant fuel efficiency advantage over current generation turbofan engines.

The development of rotors which produce a minimum level of noise is a critical technical issue which needs to be resolved in order for these concepts to become viable aircraft propulsors. Owing to the interaction of each rotor with the unsteady flow-field produced by the adjacent contra-rotating rotor, the radiated sound pressure will consist of a multitude of tones at frequencies equal to integer multiples of the sum and difference of the front and rear rotor blade passing frequencies.  

The objective of this project was to develop a new procedure to predict cabin noise tone levels from an installed open rotor. This work was conducted by ISVR and QinetiQ. At ISVR, the external noise problem has been investigated. In the first instance, simple theoretical models based on rotating point sound sources and a rigid, cylindrical fuselage have been used to predict the unsteady acoustic pressures on the fuselage surface. Concurrently, at QinetiQ the noise transmission problem through the aircraft fuselage has been investigated, in order to predict cabin noise levels when an open rotor is installed on an aircraft.  

This work was funded by the Technology Strategy Board project SYMPHONY.

Related publications

Far-field sound radiation due to an installed open rotor.
By A. McALPINE and M.J. KINGAN.
International Journal of Aeroacoustics, 11(2):213–245, 2012.