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Component erosion in gas turbines can be a serious problem. The erosive particles which may be sand, ingested into compressors in desert regions, or carbon shed from gas turbine combustors, contribute to significant blade life reduction. In extreme cases, both sand and carbon particles can cause surface build up on turbine blades reducing efficiency and block the small diameter cooling holes thereby reducing cooling effectiveness. A two-dimensional turbine cascade tunnel was designed and built incorporating perspex rotor blades which were eroded for a variety of parametric conditions. The aerodynamic performance of the turbine cascade tunnel is examined with respect to pressure losses and efficiency. The introduction of film cooling air in varying quantities and configurations in the leading edge region is shown to significantly reduce erosive wear. Maximum erosion was found to occur close to the stagnation point on the suction surface of the aerofoils. The test Reynolds number and particle trajectories were chosen to closely represent the entry conditions of an actual film cooled turbine which had experienced this type of erosive wear in operation.

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The use of water as a hydraulic fluid in a pump necessitates the use of conformal contacts to reduce the high rates of wear and leakage losses that result from the low viscosity and lubricity of water. Swashplate type axial piston pumps are ideal in this respect because they incorporate such conformal contacts. Furthermore, the development of such a pump for use with water, especially sea-water, critically relies on the correct selection and application of materials. The purpose of this research work is firstly to examine the contact conditions within an axial piston pump for a range of sleeved and lined components manufactured from a variety of different materials. The use of finite element analysis with gap elements is a useful way of determining the contact pressure distribution between conformally contacting components. It is shown that this method gives excellent agreement with available analytical methods for the two-dimensional cylindrical and axisymmetric spherical cases, and thus can be extended to layered components. Extension to three dimensions, when the contact cannot be accounted for by plane strain or plane stress conditions, is also possible, allowing a much more representative analysis of the contact conditions within an axial piston pump. No single combination of materials is identified as being the most suitable, rather, the method enables the consequences of choosing materials for their tribological characteristics to be examined. Once the contact conditions are known within the pump it is then possible to more accurately design the pump components. However, conventional deterministic methods are not appropriate for designing ceramic components, due to the inherent scatter of limiting defects, and statistical methods are necessary. Thus the second part of this research work is aimed at reviewing and examining the different probabilistic design methods with the long-term view of determining which, if any, are best suited to the design of ceramic components in this particular application. It is conduded that no single method adequately predicts the probability of failure of ceramic specimens with more complex stress distributions than four-point flexure bars.

The problem of pressure ripple propagation in fluid filled pipelines has been understood for a long time. To-date, however, mathematical representations of pressure ripple standing waves generated in hydraulic systems have been limited to very simple systems operating at low mean pressure levels and over limited frequency ranges. This report details the evaluation and development of the mathematical impedance representation of hydraulic systems and system components. With the result that these can be used to predict, with confidence, pressure ripple levels in hydraulic circuits under normal conditions of operation and over a wide frequency range. The confidence comes from the detailed practical examination of the pressure ripple levels created in hydraulic systems, made up from standard hydraulic components, operated under normal conditions of pressure and flow. Although the test circuits used are only representative of practical systems, they do not perform any specific function, they incorporate all the major features of circuit design, including branch lines and impedances (components) in series. Lastly, the ability to model with accuracy the pressure ripple levels within a hydraulic circuit provides the means by which they can become part of the overall design specification for a hydraulic system. This thesis illustrates the difficulties which restrict the practical implementation of this ideal.

An investigation has been made of the effectiveness of reinforced flexible hoses in decreasing pressure fluctuations in a hydraulic circuit. An understanding has been obtained of the properties and length of hose required to achieve a quieter system. The existing theory of longitudinal wave propagation in hoses has been extended by considering the effect of fluid viscosity and by making an accurate allowance for the inner lining. The theory has been checked by comparing the wave properties obtained from resonance tests with those calculated from the physical properties of hose and fluid by using the theory. A method of calculating pressure fluctuations in a complete hydraulic system consisting of one or more lengths of hose has been developed. In many cases, motion of the ends of hoses can be neglected which simplifies the calculations. The results for simple circuits have been compared with those obtained experimentally. A theoretical investigation has been made of the effects of the physical properties of a hose on the wave properties. It has been found helpful to split up wall stiffness into two components corresponding to actual or effective extension of the reinforcing cords and to changes in cord angle. There are two ways in which hoses can be used to reduce the pressure fluctuations in a system. A short tuned length of hose can be used to reduce pressure fluctuation at a particular frequency, or a longer length can be used for broadband attenuation. Both approaches have been investigated theoretically and experimentally, although only the latter is of general practical applicability. High attenuation is achieved with extensible cords and with high loss factors associated with wall deformation. For this reason nylon reinforced hoses are effective. The theory also enables the normal surface velocity of a hose, and hence the sound power radiated from it, to be calculated.