All turbomachines experience vibration from a variety of sources. Resonance may occur that subjects one or more blades to maximum stress conditions. Blade tip-timing (BTT) is a emergent, alternative blade stress measurement technology that is non-intrusive and noncontacting, yet delivers data on all blades in a rotor stage. By measuring blade tip passing times at a number of sensors mounted externally on the rotor's casing, processing and analysis of this data yields resonance frequencies or Engine Orders, and tip amplitudes. This study sought to advance Rolls-Royce's strategy for BTT by improving its data processing and analysis capabilities in two areas: 1. Data analysis of blades undergoing synchronous resonance, by the development of: • A multiple degrees-of-freedom blade tip displacement simulator, created to provide representative synchronous data under controlled conditions. • The formulation of a number of approaches new to BIT data analysis and their evaluation and comparison using the above simulator: three variations of an Autoregressive (AR) approach an Eigen decomposition technique and a matrix Determinant method. • An experimental Rig, designed and constructed to provide real BTT data at low cost, with which to test and begin validation of the best analysis methods. 2. The productionisation ofBTT at Rolls-Royce, which will be enhanced by: • A fast ellipse-fitting algorithm for the Two Parameter Plot (2PP) analysis method. • An ellipse-fitting Goodness-of-Fit Factor to aid analysis automation. • Cross-correlation data analysis that detects resonance behaviour automatically. This work makes the following recommendations: 1. One of the three AR techniques is robust and reliable enough for industrial use. 2. The fast ellipse-fitting algorithm be written into an industrial 2PP analysis package. 3. Trial Cross-correlation analysis on industrial data to establish its reliability further. 4. Replace optical 'spot' probes with 'line' probes to reduce measurement uncertainties. 5. Increase the industrial BTT system capacity to allow connection of up to eight probes.

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This thesis presents work carried out with the aim of improving the modelling of windmilling in gas turbine performance. The work also examines the phenomenon of relight. Methods of representing the performance of the turbomachinery components are investigated and recommendations are made for the use of a number of non- dimensional variables on which to map turbomachinery performance. A performance model was built using the turbomachinery characteristics proposed in order to test the robustness of the representations. The model was written in Fortran 90 and coupled directly to a spreadsheet package to allow easy analysis of the results. The effect of choice of representation, in terms of both the robustness and the results obtained, is presented. Techniques for the extrapolation of above-idle turbomachinery characteristics to the sub-idle region for starting and windmilling modelling are examined. A number of techniques are analysed and two new methods are proposed. These are the use of computational fluid dynamics to generate a zero speed torque and pressure loss relationship and the use of a semi-empiricalstage-by-stageextrapolation method. Some aspects of relight combustion, particularly in respect of ignition, are studied. Also investigated were the accessory systems acting on the gearbox of the engine. An assessment of the design process and the consequent benefits to the company of improved modelling were presented, in terms of the reduction in design risks and in project development costs. It was shown that research of this nature can have a substantial impact on an engine's development programme Throughout the doctoral programme, Masters and exchange students were used to broaden the scope and depth of the research. This thesis examines how best to ensure that the results of such collaboration are positive and presents the approach which this researcher used.

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