This thesis presents the study and development of optimization methods that can perform concurrent aerodynamic-aeroelastic blade optimization in a multi-bladerow environment, and for realistic turbomachinery blade geometries. The Nonlinear Harmonic Phase Solution Method has been chosen as the flow solution method of this work because of its capability to calculate the aeroelasticity features of interest (blade flutter) and the main flow aerodynamic performance in steady flow timescales. The first optimization method that is shown is a more generic non-gradient method with an improved version of a quadratic Response Surface Model. The new Re-Scaled Response Surface Model has shown marked convergence and performance improvements against traditional surrogate models. However, the computational cost of this method for cases with a large number of design variables limits its real applications. A gradient-based adjoint method is presented next as a cost-independent alternative that can accomplish efficient multi-bladerow optimization for a large number of variables within the current levels of computational power. The continuous adjoint system has been developed based on the same methodology as the flow solution method and it shows a more consistent relation between the flow field and its corresponding adjoint field, in agreement with the "anti-physics" information path. An adjoint interface treatment has been developed as an extension of the flow harmonic interface treatment. This unique treatment allows capture of the damping sensitivities of the vibrating blade to shape changes in adjacent rows. The application of this method to the design optimization of compressor and turbine stages has shown its capability to perform efficient multicomponent and multi-disciplinary design optimization of turbomachinery blades.

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Soot production in gas turbine combustors is not desirable since it is the major source of exhaust smoke emission and its thermal radiation to the combustor liner deteriorates the liner durability. Soot formation involves comparatively slow chemistry and equilibrium can not be applied to soot modelling in the combustor flow field. . The exact sooting process in the combustor is poorly understood given both the complexity and the limited experimental data available. The work reported in this thesis seeks to first develop in-situ techniques for retrieving spatially-resolved soot properties, mainly soot particle volume fraction, from within the combustor and also to apply the measured results to comparisons with predicted soot concentrations. Two probing methods have been demonstrated which also incorporate a laser absorption technique. The sight probe proves to be more reliable in the present measurements. The evaluation of the physical probing techniques in sooty laboratory flames reveals that the flame structure will not be substantially distorted by the probe. The disturbance caused by the probe is localised, a feature which is evident in the reported water flow visualization test. The necessary inert gas purge can be minimised to reduce the local aerodynamic perturbation. The measured soot volume fraction distributions are comparable with sooting levels reported in flame studies in the literature. The peak soot volume fractions are located off-axis, characteristic of the fuel atornization. The measurementsin the primary zone are restricted by the multi-phase character of the flow, where soot absorption can not be readily discriminated from fuel droplet scattering. Measurements are reported over a range of air-fuel ratios, inlet pressures and temperatures. Time-averageds calard istributionsa t the nominald ilution sectionh ave beeno btained in addition to the soot measuremenut sing probe sampling and standard gas analysis. Correlationso f carbond ioxide with mixture fraction reveala clear relationshipa t overall lean conditionsc onsistenwt ith widely usedm odelleda ssumptions.T here are less well-correlated relationshipsb etweent emperaturea ndm ixture fraction, possiblyd ue to the influenceo f scalar fluctuationsa nda lsoo f the scalard issipationr ate. Sootl oadingi n the presentf low conditions is characteristicallylo w, basedo n the mixture fraction ands ootv olumef raction data. Thermal radiation in the visible spectrum shows a distinct narrow band spectra in addition to the soot continuum, which is believed to arise fromC2radical emission. The mean radiation intensities, predictedb y usingt he measuredte mperaturea nds ootc oncentrationre sults,a rei n generallo wer than the measured mean intensities. Temperature fluctuation levels may be particularly influential in some of these calculations. Sootm odellingi n the combustohr asb eenu ndertakenb y applyinga n extendedla minar flamelet concept. The two-equations oot formation model has beenp rimarily developedo n laminar flames. The comparisono f the computationa nd measuremenstu ggeststh at this soot model holds promise in the context of prediction in the combustor. In the absenceo f a satisfactoryt heoreticald escriptiono f the fuel-air burning in the combustor,w heret he liquid kerosinee mployedis replacedb y gaseoups ropane,t he computeds calarp rofiles are inconsistent in some importantr espectsw ith the measuredo nes. This exerts a major effect on the soot predictioni n terms of the quantitatived etail in the computationw, hich is howeverc rucial for the soot model development. The original flow field modelling needs to be improved for the purpose of further soot model refinement.

The main objective of this work is to create a robust model for two-phase liquid spray combustion flow using vegetable oils, to investigate the flow structure generated by a swirler array with different fuels, and secondly to assess and optimise the capability of the CFD to predict accurately the results obtained experimentally and eventually enhance CFD model development and simulation. Validation is achieved by comparing the numerical results obtained with CFD with the experimental measurements. The purpose of this research is to increase the scientific understanding of the fundamental mechanisms of the spray combustion process using a carbon neutral fuel such as ethanol and biodiesel. In fact, very few numerical simulations of liquid biomass fuels in gas turbine systems are available in the literature. The flames are simulated using the commercial code FLUENT. The combustion/turbulence interaction is modelled using the laminar flamelet approach with detailed chemistry modelled using the OPPDIFF model from CHEMKIN. While the experiments could be carried out only up to 3 atm, the simulations were further extended to a maximum pressure of 10 atm. The FLUENT results were assessed qualitatively and quantitatively between the experimental measurements and the simulation. The cold flow features have been captured by the present simulations with a good degree of accuracy. Effect of air preheating was investigated for the biodiesel, and sensitivity to droplet size and spray angles variation were analysed. Good agreement was obtained for ethanol except in the fuel lean region due to failure of the FLUENT laminar flamelet model to capture local flame extinction while biodiesel simulation resulted in a significant overprediction of the flame temperature especially in the downstream region and satisfactory results further upstream. The results show the importance of setting proper droplet initial conditions, since it will significantly affect the structure of the flame.

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No description available.

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Presently, there is a global push to improve the productivity of heavy duty machinery. With increasing demands to apply to stricter fuel and emission standards alongside increasing energy costs, it has become vital to maximise the energy efficiency of systems. Swash plate axial piston motors have inefficiencies up to 15% caused by fluid leakage and internal friction. Mechanical systems are being modified to reduce friction amongst components whilst allowing them to run at higher operating conditions and temperatures. This is where surface improvement technology plays a crucial role. By achieving compatibility between the modified surfaces and lubricant additives optimum efficient systems can be achieved. MoS2 coatings and nitriding heat treatments are applied to sample surfaces to improve their tribological properties. There are however only a few studies that focus on the tribochemical interactions of nitrided samples with lubricant additives. This study aims to investigate the impact of the properties of the modified surfaces on tribological and tribochemical interactions. The primary focus will be validating the application of the nitriding treatment to improve the durability of components and investigating the interactions with various lubricant additives in comparison to alternative treatments. To achieve this, tribological performance of the various samples and oils has been evaluated using the Cameron Plint TE77 tribometer in the boundary lubrication regime. This was followed by using the MTM-SLIM testing rig to validate the trends observed with the TE77 and add another level of complexity to the testing conditions. The MTM SLIM would allow visualisation of the formation and development of a tribofilm on the sample variants whilst using testing conditions similar to that used within a hydraulic motor. A number of surface analysis techniques were employed in this study such as Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX), X-ray Photoelectron Spectroscopy (XPS) and Raman spectroscopy. They helped to characterise the tribofilms formed and understand the effect of the properties of treated surfaces. The results of this study indicate that the mechanical properties of the compound layer formed during the nitriding process had a significant impact on the sample tribological properties, allowing it to perform better than the untreated and MoS2 coated samples. However the inertness of this layer prevents the formation of a thick tribofilm which could further impact friction and wear. However the presence of additional layers upon the nitrided surface are shown to impact not only tribological behaviour but also tribochemical formation, due to the chemical compounds present. Critically the results showed that not only did the type of treatment applied to the samples impact the tribological behaviour but also the chemical interactions with the compounds within the lubricant played a significant role. This was shown with the MoS2 coated samples and sulphurised olefin additive, where the synergy between coating and FeS formed lead to the lowest friction system observed within this study. This study has shown that the oxy-nitriding process is an effective treatment to improve the tribological performance of the samples, with lower friction and wear being achieved compared to alternative samples. The presence of an oxide layer led to the formation of FeS2 within the tribofilm. However, due to the relative thinness of the tribofilm the impact on friction was minimal. The thickness of the tribofilm with the nitrided was influenced by the presence of nascent iron on the sample surface. The tribological influence of the oxide layer was minimal however with alternative layers such as FeS the friction and wear response the influence was significant. The project demonstrated that the various additive types could positively and negatively impact the friction and wear of the modified surfaces depending on its tribochemical interaction.

A major challenge faced by the Gas Turbine industry, both the users and the manufacturers is the reduction of life cycle costs and safe running of a gas turbine. A reduction in the costs can be achieved by reducing the development time while the engine is in the development stage and reducing operating costs for in service engines. One of the ways of achieving these would be the use of sophisticated performance analysis and diagnostic techniques. Techniques for such purposes of diagnosis have developed a great deal over the last three decades. The initial work was on gas path analysis, followed by use of conventional techniques such as Kalman filters and Least squares algorithm for gas path analysis. The last decade has seen a lot of work on the use of intelligent systems such as neural networks, fuzzy logic and expert systems for such purposes. Though improvements have been made over the years, but all these techniques have major drawbacks, which make their use in the current stage of development very unlikely. The use of genetic algorithm based optimization technique for diagnostics of well instrumented engines (development engines) was successfully made at Cranfield University. The present work presents a technique for fault diagnostics of engines that are relatively poorly instrumented. The work presents how the task is achieved by the use of multiple operating point analysis and the use of a genetic algorithm based optimization technique for optimization of an objective function that depends on the measurements and the corresponding value for changed performance and power setting parameters obtained from the thermodynamic performance model of the engine. The main issues that have been addressed are the choice and number of operating points and also the development of the multi objective optimization technique. The technique is able to accurately identify the faulty components and quantify the fault. The fault is expressed in terms of a change in efficiency and capacity of the various components. The optimization also carries out Sensor fault detection, isolation and accommodation .The technique has been tested on a number of engine types using simulated data. These engines have been chosen to cover a wide range of instrumentation suites. The advantages, drawbacks and the suggested method of application have also been presented.