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No description available.

No description available.

No description available.

No description available.

The aim of this study was to develop a self-tuning or adaptive SI engine controller using torque feedback as the main control variable, based on direct/indirect measurement and estimation techniques. The indirect methods include in-cylinder pressure measurement, ion current measurement, and crankshaft rotational frequency variation. It is proposed that torque feedback would not only allow the operating set-points to be monitored and achieved under wider conditions (including the extremes of humidity and throttle transients), but to actively select and optimise the set-points on the basis of both performance and fuel economy. A further application could allow the use of multiple fuel types and/or combustion enhancing methods to best effect. An existing experimental facility which comprised a Jaguar AJ-V8 SI engine coupled to a Heenan-Froude Dynamatic GVAL (Mk 1) dynamometer was adopted for this work, in order to provide a flexible distributed engine test system comprising a combined user interface and cylinder pressure monitoring system, a functional dynamometer controller, and a modular engine controller which is close coupled to an embedded PC has been created. The considerable challenges involved in creating this system have meant that the core research objectives of this project have not been met. Nevertheless, an open-architecture software and hardware engine controller and independent throttle controller have been developed, to the point of testing. For the purposes of optimum ignition timing validation and combustion knock detection, an optical cylinder pressure measurement system with crank angle synchronous sampling has been developed. The departure from the project’s initial aims have also highlighted several important aspects of eddy-current dynamometer control, whose closed-loop behaviour was modelled in Simulink to study its control and dynamic response. The design of the dynamometer real-time controller was successfully implemented and evaluated in a more contemporary context using an embedded digital controller.

Automotive engine pistons are not normally expected to be made of plastics or even composites, but before now the latter have been applied to an Over Head Cam follower of an automotive engine. As such this research work sought to demonstrate that the composite Carbon fibre Phenolic composite of the grade used is suitable enough to be employed in a hybrid piston. This work covered three broad areas; Constitutive modelling, Optimization and Fatigue. Numerical/simulation and empirical methods were employed to accomplish the tasks involved. The design of the piston was presented and this design took into account the fact that a composite was involved. A contact analysis was carried out to analyse the stresses arising from the interference of the composite piston skirt and the aluminium cap just in case interference fit is adopted as the method of assembly. Empirical analyses of tubular carbon fibre composite samples as well as carbon fibre Phenolic composite prepregs were carried out to determine the tensile, compressive and flexural capabilities of the materials as the case may be. Young's and Shear modulus values as well Poisson's ratio values were deduced leading to the establishment of the constitutive model of the composite's lamina and consequently that of the laminate for the various samples that were deemed suitable based on the nature of their testing and preparation as well as a piston cap model. With the constitutive models worked out and the piston cap model developed, fatigue analysis of the structure and piston cap followed, and in other to get the best out of the structures or materials and the piston cap optimization followed after which yet more fatigue analysis was done for the optimization outcomes. To a great extent one of the Elastic Modulus values obtained empirically can be said to be sufficiently reliable as its empirical test was simulated numerically and it turned out satisfactory; the maximum stress value from the test was 158.5 MPa while that of the simulation was 158.267 MPa. All the results were almost the same apart from the strain values that were significantly divergent. The adopted Elastic Modulus value of 61049.6757 MPa stemmed from this empirical and numerical analyses and since these two differed only in the strain values and agreed in pretty much in all other the parameters it can be said that this adopted Elastic Modulus value was indeed sufficiently reliable. It also implies that the outcomes of all the other numerical analyses that were carried out with it can be trusted. In the Results and Discussion chapter numerical Crack Propagation was discussed for various crack lengths of a finite element model.

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Thermal barrier coatings (TBC's) are used to protect gas turbine blades from environmental degradation as well as to increase thermodynamic efficiency. Most TBC systems consist of a ceramic thermal barrier coating such as partially stabilized zirconia adhering to an oxidation resistant bond coat, which in turn is bonded to the turbine blade. This is required since partially stabilised zirconia will not readily bond to superalloys. However, the TBC can fail in service either by bond coat oxidation or thermal expansion mismatch between the bond coat and the TBC. A systematic literature survey has shown that the superalloy substrate material, type of bond coat selected, with the coating application techniques i.e. thermal spray or Electron Beam PVD (EBPVD) plays a fundamental role in determining the failure mechanisms involved. This program of work is concerned with the development of coatings with enhanced temperature capabilities for turbine blade applications by understanding the fundamental mechanisms responsible for adhesion between the nickel based turbine blade and zirconia based TBC. An understanding of the bonding mechanisms will allow the design of advanced coating systems with increased operating temperatures. This program of work introduces the Glow Discharge Optical Emission Spectroscopy (GDOES) technique, an atomic emission technique used for both bulk and depth profile analysis, which had not previously been applied to TBC's, and SEM and TEM in order to enhance understanding of failure modes in TBC systems and adhesion process. The results obtained from the studies indicate that the GDOES technique can be applied to depth profile bond coats and exposed TBC systems both qualitatively and semi-quantitatively. GDOES has been able to detect elements such as silicon and sodium that are in the ppm levels which are difficult/impossible to detect using EDX systems, and are very important in coating developments. In addition, as a preliminary guide GDOES has shown Ti diffusion from the superalloy substrate into the bond coat to be detrimental towards coating adhesion on most of the systems studied. The results of SEM and cross-sectional TEM on selected bond coat systems has shown the low cost Pt bond coat microstructure system to consist of TBC, Al2O3 bond coat and CMSX-4 superalloy substrate in all cases. The intermediate layer between the TBC and bond coat consists of Al2O3 which has been identified as responsible for maintaining the adhesion. Also identified is evidence of Ti segregation at the Al2O3/bond coat interface, known to lead to decohesion in coatings. Failure in the low cost Pt bond coat system has been identified as the decohesion between the interfacial layer of Al2O3 and the bond coat. The program of studies has enabled failure mechanisms and factors affecting bonding to be identified in low cost Pt bond coat systems, so that in future better coating systems with enhanced properties can be designed This should also ensure that improved reliability in engines and increased service life of turbine blades be achieved.

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