The paper describes the results from two series of tests of Rolls-Royce's open rotor rig 145 at the Aircraft Research Association's (ARA) high speed wind tunnel. The paper describes the results from the first test in 2008/9, the subsequent redesign and aeroacoustic optimisation of the open rotor blades, and the results from the second test of rig 145 at ARA in 2011. Comparisons are made between the high speed results of the two different blade designs and results are also shown of the variation in near field noise with key blade operating parameters such as tunnel Mach number and blade pitch. For calibration purposes, back-to-back comparisons are also made between the low speed results of rig 145 at ARA and those from the equivalent tests of rig 145 at the large low speed anechoic facility DNW in 2008 and 2010. Noise prediction tools, specifically developed for the acoustic near field of open rotors, are discussed and applied to the data to allow rig-rig comparisons at equivalent spatial locations.

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This paper presents a review of aeroelasticity research concerning fan blades in modern civil aircraft engines. It summarises the research carried out at the Rolls-Royce Vibration University Technology Centre (VUTC) at Imperial College over the past 25 years. The purpose of this paper is to gather information on all the aeroelastic issues observed for civil aero-engine fan blades into one document and provide a useful synopsis for other researchers in the field. The results presented here are based on numerical methods but wherever possible data from experiments are used to verify the numerical findings. For cases where such datasets do not exist fundamental principles, engine observations and engineering judgement are used to support the numerical results. Numerical methods offer a cheaper alternative to rig tests, especially in cases of blade failure, and can also provide more information about the nature of instabilities, which can be useful in the design of future civil aircraft engines. In fact, in cases such as crosswind testing that use smaller rig-scale blades, such results can even be more representative of real engine flows.

This paper describes an analytical model for predicting the tonal noise produced by an open rotor situated in a rectangular wind tunnel with rigid walls. The mathematical derivation of the model makes use of Graf 's theorem to transform from Cartesian coordinates, which are useful for describing the duct geometry, to cylindrical coordinates, which are useful for describing the distribution of 'sources' on the rotating blades. This transformation greatly simplifies the analysis and provides a final expression which is relatively straightforward to evaluate. An interesting validation of the model is also presented where it is shown that the final expression is equivalent to that produced by an infinite series of 'image sources'. The model is then used to compare sound pressure levels produced by an open rotor operating within a rigid walled wind tunnel to those which would be produced if the rotor was operating in a free-field environment. The motivation for this work was to assess how measurements made in a closed test section wind tunnel could be used to infer noise levels in a free-field environment.

Modern gas turbine design continues to move towards improved performance, reduced weight and reduced cost. As turbomachinery blade aerofoils are thinned to improve performance and reduce weight, aeroelastic issues such as flutter, forced response and stall driven vibrations become more predominant. Moreover, as the use of blisks (blade-integrated-disks) with very low mechanical damping becomes more common in modern compressor designs, accurate prediction of compressor aeroelastic stability in a multi-row environment becomes vital. This paper presents a review of aeroelasticity research carried out at Rolls-Royce Vibration University Technology Centre (VUTC) at Imperial College over the past 20 years. The aim is to summarise the unusual aeroelastic issues observed in multi-stage compressors into one document so that it can be used by other researchers in the field. Blade passing forced response is not addressed here as their existence can be detected by a Campbell diagram. The results presented here are based on numerical methods but where possible data from experiments are used to verify the numerical findings.