A boost controlled continuously variable geometry turbocharger prototype has been designed, manufactured and tested. The prototype has been first rig tested and later fitted to a Perkins T6.354 diesel engine. The engine tests have included both steady state and transient runs. Torque back up has been improved considerably increasing from 34.3% to 55.8%, the former occurring at 1400rpm while the latter at 1200rpm. In the experimental programme, compressor surge has been the limiting parameter while in the theoretical investigations a wide mass flow compressor has been assumed and the limiting parameter was maximum cylinder pressure. In the theoretical investigations lower compression ratio and retarded injection timing have been considered to further improve the scope for higher torque back up and improved transient response. In addition the performance of the variable geometry turbocharged engine using a simple boost controlled turbine restriction schedule has been simulated. It is concluded that a simple boost controlled system will present sfc penalties in the part load regime and thus more sophisticated multi-variable schemes will have to be studied if sfc optimization is to be achieved. The experimental programme has been conducted using the 'zip fastener' design. This design has been found to be strongly non-linear with respect to turn down ratio in response to turbine restriction but will offer the required effects at the expense of a slight drop in turbine efficiency. However, in future investigations initial calibration studies have to be undertaken to ensure comparable swallowing capacities with the standard turbine which the variable geometry turbine replaces.

The vibration of a turbocharger blade and dynamic characteristics of bladed packets connected by a lacing wire have been studied. The study was carried out using three analytical and experimental methods. They are: Modal Testing, Electronic Speckle Pattern Interferometry (ESPD and Finite Element Analysis (FEA)). Vibration modes of a turbocharger blade with aerodynamic profile, with and without a lacing wire, were identified using model blades with simplified geometry. The separation of coupled modes was achieved using ESPI tests. The modes of vibrations of bladed packets were identified. The effect of inter-blade coupling through a lacing wire is that a cluster of sub-modes are generated in bladed packets corresponding to each fundamental mode of the freestanding blade, the number of the sub-modes being equal to the number of blades in the packet. Apart from the fundamental sub-mode, the vibration of all other submodes are out of phase with different phase relations. The stiffness of the lacing wire and its location with respect to the blade make great contributions towards certain mode clusters in terms of mode shapes and natural frequencies. The nonlinearity of the stiffness of the deformed lacing wire caused by centrifugal force was established. The coupling of this non linearity with different vibration amplitudes, due to different phase relation, results in the dynamic mistuning in lacing wire stiffness. This mistuning is considered to be a major attribute in reducing the responses at resonance.

This thesis initially describes the experimental work which was carried out in order to examine the effects of parameters such as the blade profile, free stream turbulence intensity etc. on the onset and, extent of transition in the boundary layer on a turbine blade. A series of four different blade profiles with identical pressure surfaces but different suction surfaces, were tested. The suction surfaces differed in the severity and extent of their initial favourable pressure gradients. Tests were carried out for a range of throat Mach numbers and free stream turbulence intensities. From the results obtained it is suggested that the most significant factor is 'the severity of the initial. favourable pressure gradient. This appears to have an inhibiting effect on the influence of the free stream turbulence and on the growth of the turbulent stresses in the transition region. Using these hypotheses, modifications were made to an existing boundary layer prediction program in order to provide a better transition-model and to include the effect of free stream turbulence.

No description available.

No description available.

No description available.

This thesis investigates a novel secondary flow reduction method. The inlet boundary layer to a linear turbine cascade is skewed by injection of air through an upstream slot to oppose regular generated negative stream wise vorticity. Other methods from the pertinent literature are reviewed on a broad basis. Detailed measurements of the flowfield in the Durham Linear Cascade facility have shown that substantial reductions in secondary flows and losses are possible. If the kinetic energy required for the blowing is taken into account by means of an availability analysis, no net gain in loss is achieved. Tests are performed at two different angles, of which the higher is typical for film cooling applications, and at a wide range of injection ratios. Calculation of the mixed-out losses show the tangential rather than spanwise momentum of the injected air is more effective in countering the generation of secondary flows. Computations using a state-of-the-art Navier-Stokes solver indicated shortcomings in modelling a flow governed by complex vortex dynamics. Improvements in the turbulence model and injection geometry could remedy this. The evaluation of turbulent and laminar production rates obtained without injection helps to explain total pressure loss generation mechanisms. The comparison of calculated and experimental eddy viscosities reveals the inadequacy of the Boussinesq assumption for high turning flows. The results obtained in this work are relevant to endwall film cooling applications. The tangential injection of air in front of the leading edge provides coolant in an optimum manner whilst possibly reducing secondary losses to a large extent. Disc cooling air, present in a real engine to prevent the ingestion of hot air from the mainstream, could be used to supply the injection.

The growth of thrust and improved aeroengine efficiency has been gained by increased temperatures throughout the engine. This has been achieved by improved material technology and the continuous cooling of components complemented by the addition of thermal barrier coatings (TBC) to turbine and combustion chamber components. The aggressive nature of the application process of the TBC has previously made the measurement of metal surface temperature and strain exceedingly difficult on components to which it is applied. In the present study magnetron sputter-deposited thin film sensor techniques have been developed specifically for compressor and turbine applications of noble metal thermocouples and strain gauges. The deposition, patterning and evaluation of reactively sputtered aluminium oxide, type R platinum thermocouples as well as PdCr and PtW dynamic strain gauges is reported. A sputtered NiCoCrAlY coating has been developed to replace the vacuum plasma spray process currently used in the TBC system. The most favourable location for the thin film sensor is at the metal/ceramic interface of the TBC system. However, in order to protect the sensor from the aggressive TBC process, the sensor has been deposited in a novel installation between two layers of NiCoCrAlY bond coat. Several trials have been performed to fabricate this package on turbine blade material substrates. This work has demonstrated that the proposed sensor structure is feasible. However there are problems with delamination due to contamination and residual stress and with poor electrical insulation and these have limited the high temperature testing that could be performed. The novel techniques developed are already being utilised in measurement applications on components without TBCs. This work has been performed in an industrial context. The extensive project and risk management activities are reported.

No description available.

No description available.