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The cooling air in a gas turbine engine is subject to windage as it flows through the internal air system. The work in this thesis focuses on the windage generated as the cooling air passes over the rotor surface, particularly for case where bolts are encountered. Reducing windage heating of the cooling air is of great importance to turbomachinery engineers, particularly in the aerospace industry, since the use of compressor air for cooling greatly reduces the thrust potential of an engine. The ability to accurately predict windage can help reduce the quantity of cooling air required, resulting in increased efficiency. A purpose built rig was used to measure both windage and rotor surface temperature as air passes through an enclosed rotor-stator cavity. A wide range of flow conditions were tested with some being close to those found in a modern gas turbine engine. A variety of both stator and rotor mounted bolts were investigated, of varying size and shape, as well as cavities in the disc surface. In addition, PIV measurements of the core tangential velocity were obtained. Test results show that windage is increased substantially with rotor bolts present, compared with a plain disc, and that it increases with increasing bolt size. For hexagonal rotor bolts a new correlation was produced between the moment coefficient and bolt diameter to pitch ratio for a range of flow conditions, characterised by the rotational and throughflow Reynolds numbers. Stator bolts were shown to generate a large increase in disc surface temperature compared with the plain disc at engine representative conditions. PIV measurements of the core tangential velocity showed an increase of up to 80% above the plain disc with rotor bolts present and no superimposed flow. When throughflow was introduced, the increase was around 300%. These measurements also demonstrate a local increase in tangential velocity in the region close to the bolt.

Gas turbine compressor performance may encounter deterioration during service for various reasons such as damage by debris from the casing or foreign objects impacting on the blades, typically near the rotor's tip. Moreover, mal-schedule of Variable Stator Vanes (VSVs) during start-up may also result in performance deterioration and reduction in the surge margin. Ability to assess the effect of compressor deterioration using Computational Fluid Dynamics (CFD) is important at both design stage and in service. Compressor blade damage breaks the cyclic symmetry and the VSVs mal-schecule creates mis-match between stages together with geometric variations, thus computations are desirable to be performed using full annulus assemblies. Furthermore, downstream boundary conditions are also unknown during rotating stall or surge and simulations become difficult. This research presents unsteady time-accurate CFD analyses of compressor performance with tip curl blade damage in a single stage axial flow compressor and VSVs mal-schedule in a 3.5 stage axial flow compressor. Computations were per- formed near stall boundary to predict rotating stall characteristics. The primary objectives are to characterise the overall compressor performance and analyse the detailed flow behaviour. Computations for the nominal blade configurations were also performed for comparison purposes for both compressors. All unsteady simulations were performed at part speeds with a variable nozzle downstream representing an experimental throttle. For the blade damage study, two different degrees of damage for one blade and multiple damaged blades were investigated and compared with the results from the undamaged case. For the VSVs mal-schedule study, the first two stators were assumed to be variable and were used to create mal-schedule vane settings for the investigation. The effects of blade damage and VSVs mal-schedule on the aerodynamics performance and rotating stall characteristics for both compressor assemblies were investigated respectively and discussed in detail.

Gas turbine engine performance requires effective and reliable internal cooling over the duty cycle of the engine. Understanding the effectiveness of cooling flows when making life predictions for rotating components subject to the main gas path temperatures is crucial. A test facility has been developed at the University of Sussex incorporating a two stage turbine designed to support a European funded research project with the objective of enhancing the understanding of interactions between main annulus gas paths and secondary air systems. This thesis describes the specific contribution of the author to the research conducted at the test facility. Non-invasive gas seeding and concentration measurement techniques together with hot geometry displacement measurements have been developed to meet three distinct objectives: to determine inter-stage seal flows between rotor disc cavities; to provide data to quantify rim seal exchange flows between rotor stator cavities and the main annulus gas path for both bulk ingestion and egress conditions; and, to provide data to quantify the re-ingestion of cooling air egressed into the main annulus gas path. Detailed knowledge of these flows is vital to understanding the flow structures within rotor stator cavities and to optimise coolant delivery methods. Experimental results are presented for a number of cooling flow supply geometries and flow rates. The gas concentration measurement techniques developed and the results obtained are compared to traditional measurements as well as numerical simulations carried out by research project partners. This work develops the measurement techniques of rotor stator cavity flows and provides data suitable for the validation of improved thermo-mechanical and CFD codes, beneficial to the engine design process.

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Current gas turbine technology for power generation is generally optimised for natural gas. On the basis of current instabilities in natural gas price and supply, the use of alternative fuels, such as syngas, has recently gained high interest. Due to the different thermodynamic properties of syngas compared to natural gas the behaviour of existing gas turbine components may significantly change. From practical and economic points of view, it is generally considered that in order to meet the new fuel properties, the main effort should be put on the adaptation of conventional gas turbines in integrated gasification combined cycle (IGCC) plants rather than producing a new generation of gas turbine designs from scratch. In addition to the requirement of new combustion technologies, main critical issues are represented by the reduction of compressor surge margin and turbine blade overheating. Solutions might include thermodynamic cycle as well as turbine geometry modifications. The latter would be preferred in terms of power plant performance. The main aim of this thesis is to explore suitable solutions to be applied to gas turbine compressors in order to accommodate syngas combustion. Among others, the use of variable stator vanes (VSVs) and blade radial stacking line modifications are considered. These are investigated on reference geometries available in the public domain. A baseline compressor geometry representative of a conventional heavy-duty gas turbine fueled with natural gas is generated and modified according to the understating gained during this study. The re-designed machine is a result of the application of stator vanes re-staggering in the front stages and blade sweep in the rear stages in order to cope with compressor air supply control and critical flow separation regions respectively. The obtained results show that efficient and stable operation during power modulation can be achieved, while reducing the need of other modifications to the combined cycle plant. It was therefore concluded that the proposed option can be considered a viable option to satisfy some important technical and economic constraints imposed by the integration of an existing gas turbine within an IGCC plant.

Today, fostering gas-fired power plants is recognised as a significant step towards a low-carbon economy. Gas fired-power plants are favoured over other types of fossil-fuelled power plants due to their various advantages, including lower emissions, flexibility of technology, higher efficiency, short construction times and lower capital investment. The gas turbine is the main machine and the most technologically advanced part of a gas-fired power plant. There have been a limited number of companies in industrialised countries that have developed these sophisticated technologies over the last 50 years. The global market for land-based gas turbines has an oligopolistic structure. The evolution of these technologies has been greatly influenced by countries' government policies, and in particular energy policies. In this light, one question is: to what extent have industrialising countries built their technological capabilities in gas turbines? Consequently, one focus of interest here is the way in which, and the extent to which, industrialising countries have synthesised their indigenous technology development efforts with overseas technology inflows. Countries such as Iran, India and China, which have large and growing domestic electricity markets, are appropriate candidates for research in order to understand the possible technological gaps and associated dynamics between the industrialised and industrialising worlds. To answer these questions, this thesis research deals with Iran's gas turbine industry and, for the first time, systematically examines this industry in the context of a developing country. The study delves deeply into the dynamics of interactions between indigenous technology development and overseas technology inflows. It casts light upon the influences, challenges, and difficulties associated with technological catching-up processes. The framework of the analysis is based on an extensive literature review on technological catch-up, the substitution/complementarity debate, and the gas turbine industry. The framework was operationalized through qualitative interviews as well as supplementary documents. The thesis uses a ‘dynamic approach', and argues that understanding the interaction processes cannot be reduced to examining only the type of relationship between the two technology sources. Instead, far more attention needs to be devoted to analysing the complexity and associated influences on this relationship. The thesis also provides empirical insights into the development of gas turbine capabilities in India and China, the two largest emerging economies. It reveals that a high level of state involvement in developing countries is a prominent feature of the industry. It also demonstrates that the evolution of the industry also in both developed and developing countries is closely interrelated with each country's national energy policies.