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Unsteady three-dimensional flow phenomena have major effects on the aerodynamic performance of, and heat transfer to, gas-turbine blading. Investigation of the mechanisms associated with these phenomena requires an experimental facility that is capable of simulating a gas turbine, but at lower levels of temperature and pressure to allow conventional measurement techniques. This thesis reports on the design, development and commissioning of a new experimental facility that models these unsteady three-dimensional flow phenomena. The new facility, which consists of a 62%-size, high-pressure gas-turbine stage mounted in a transient wind tunnel, simulates the turbine design point of a full-stage turbine. The thesis describes the aerodynamic and mechanical design of the new facility, a rigorous stress analysis of the facility’s rotating system and the three-stage commissioning of the facility. The thesis concludes with an assessment of the turbine stage performance.

There is a demand for a whole field velocimetry technique which offers the capability of rapid characterisation of complex engineering flow fields. This thesis describes a research programme aimed at the development of a reliable Doppler global velocimeter, suited to the measurement of such flows. The programme of work undertaken is discussed with reference both to research undertaken elsewhere and to previous work on the system at Oxford. While much of the underlying technology required for the construction of an accurate and reliable velocimeter has already been studied in Oxford and elsewhere, little attention has been paid by previous workers to the examination of the impact of data processing techniques on attainable flow measurement accuracy. In the present work, a number of image processing methods have been utilised for Doppler global velocimetry data processing. Those methods are described here, together with a theoretical analysis of their expected performance when applied to Doppler global velocimetry data. The expected error resulting from image processing considerations and also from the physical characteristics of the Doppler global velocimetry hardware are quantified in such a way that error estimates may be computed for real measured data frames. The results of the application of the velocimeter to the simple test case of measuring a velocity component of a rotating disc are presented. The velocimeter was subsequently applied to the measurement of a free jet flow and to a transonic flow field in a convergent-divergent nozzle. Correlations with accepted velocity field values were undertaken, and compared to the expected error previously determined. The choice of image processing algorithms was found to be of great importance in terms of Doppler global velocimetry measurement accuracy.

As the performance required of high pressure turbines continues to increase, there is a need to investigate many details of the flow which occur in a gas turbine stage that were previously overlooked. These include the effects of rotation and three-dimensional flow as well as unsteady effects due to the relative motion of the blade rows. In order to obtain a better understanding of the turbine flowfield a new transient facility has been commissioned in which aerodynamic and heat transfer measurements can be undertaken in a full stage turbine at engine representative conditions. The previously used technique of measuring the heat transfer rate by mounting thin film gauges on models manufactured from machineable glass ceramic was not suitable for use on the rotor blade because of the high stress levels involved. An alternative technique has been developed in which a metal turbine blade is coated with an insulating layer of enamel and thin film gauges painted on top. The developments in signal processing and calibrations which were necessary for the use of this type of thin film gauge are discussed in detail. Signal conditioning electronics have been developed which permit amplification of the thin film gauge output to a higher level within the rotating frame before transmission through a slipring. Extensive tests have been undertaken, in a purpose built spinning rig, to establish the effects of rotation on the performance and mechanical integrity of the instrumentation and associated electronics. The heat transfer measurements recorded in the rotor facility to date are presented and compared with data from a previous two-dimensional simulation of wake passing flow on the mid-height section of the same blade.

Background: The edge-to-edge (Alfieri) technique for mitral valve repair is a versatile method of treating mitral insufficiency. Because of its simplicity, it has been applied in minimally invasive surgery, and recently, in the design of endovascular closed-heart devices. Aim: The purpose of this study was to evaluate the acute in-vivo safety and feasibility of a novel percutaneous mitral valve repair system based on Alfieri technique in an animal model. Methods: Under general anesthesia, 11 pigs (90–100 kgs), underwent percutaneous Alfeiri procedure. The right femoral vein was punctured and the mitral valve was approached via a standard transeptal puncture. Combined intracardiac echo and fluoroscopic guidance was used. The procedure included: the positioning of a guide catheter for multiple access to the left atrium and for directing devices; the use of a therapy device to capture the free edge of the mitral valve leaflets using vacuum, and to deliver the suture to the valve and finally the fixation with a Nitinol suture clip, and trimming of the suture with a fastener catheter. Results: Leaflet capture, suture placement, and suture-clip deployment was successful in all 11 animals. There were no acute cardiac or access site complications. Procedural time (from wire in left atrium to completion of the procedure was 18 ± 9 min (range 9–30 min). Blood loss was 67 ± 44 ml (range 0–125ml). A double orifice configuration was visible by echocardiography at the end of the procedure in all animals. Conclusion: This acute animal study demonstrated the feasibility of a beating heart percutaneous Alfieri procedure in a non-diseased porcine valve using an endovascular suturing device to safely access the mitral valve, place a stitch through the mitral valve leaflets, and deploy a suture-clip that reproduces the surgical technique. Clinical application of this device in humans needs to be evaluated. © 2007 Wiley-Liss, Inc.