The thesis presented here comprises the work undertaken for research into novel NDE techniques in the power generation industry. This has been undertaken as part of the Engineering Doctorate Scheme run by the Research Centre for Non-Destructive Evaluation (RCNDE), which aims to bridge the technological gap between university research and industrial application. In this case, the scheme consisted of two projects completed in conjunction with RWE npower looking at current NDE problems in steam turbine and steam-raising plant. The first project was concerned with detecting microstructural transformation in steam turbine blades, which can act as a precursor to failure by environmentally assisted cracking. This project, and indeed, this entire thesis is principally based on electromagnetic testing methods. An eddy current technique for mapping the microstructural phases was produced and validated as far as was achievable; this offered a significant time-saving advantage over the previous method, by reducing inspection time from 5 man days to just 1.5. The technique has novelty in producing a 2-dimensional map of the blade surface which highlights areas where microstructural phases differ. The second project focuses on the detection of microstructural damage associated with material creep life expiry. This forms a review of the current state of technology and highlights potentially useful paths for future research in both established and emerging NDE technologies, including Magnetic Barkhausen Noise testing and laser-generated ultrasound. Both projects have provided tangible benefit to the sponsoring company and have pushed forward research in a number of technological applications.

A novel study on biomass-air gasification using a horizontal entrained-flow gasifier and catalytic processing of the product gas has been conducted. The study was designed to investigate the effect of catalyst loading on the product gas. The use of a horizontal entrained-flow gasifier reactor was used to assess the effect of the gasifier reactor orientation on the gasification process. Both experimental and computational fluid dynamics (CFD) approaches were employed. The gasification tests were conducted at 800 oC and equivalence ratio of 0.23 while the product gas was catalysed at 350-400 oC and a gas hourly space velocity (GHSV) of 8000 h-1. Preparation and characterisation of wood powder and catalysts were performed using classical methods. Moreover, the syngas and tar composition were analysed using a gas chromatograph (GC) and GC-mass spectrometer (GC-MS) respectively. The research findings showed that maximum fuel conversion and cold gas efficiency using a horizontal entrained-flow gasifier were 99 % and 70 % respectively. The gasifier length can also be reduced from the common 1000-2000 mm to 500 mm. The catalysis study showed that pumice and kaolin have limited catalytic effect on the product gas. However, doping with CeO2, ZrO2, CuO and NiO improved the syngas heating value, coking resistance and tar conversion. A notable increase in syngas LHV was achieved using ceria doped pumice (8.97 MJ/Nm3) and copper doped pumice (8.66 MJ/Nm3) compared to 6.67 MJ/Nm3 of non-catalytic test. For the tested catalysts, CeO2 doped pumice exhibited highest coking resistance. Furthermore, catalytic tar conversion was mainly through cracking and partial oxidation reactions. The lowest tar yield was found to be 3.55 g/Nm3 using kaolin-ceria-zirconia catalyst compared to 14.92 g/Nm3 of non-catalytic gasification. Tar reduction using untreated pumice was through adsorption and ranged 4-6 g/Nm3. In general, the results of this study suggest that there exist a sensitivity to the gasifier orientation on the overall gasification process. It has also shown that metal oxides have both beneficial and detrimental effects of syngas composition. Although syngas heating value increased with increasing catalyst loading, H2 showed a decreasing trend highlighting that further catalyst modification is required. Furthermore, pumice and kaolin can be utilised as catalyst support in the gasification technology. However, further experimental investigation on doping various catalytic metals and testing at different operating conditions are hereby proposed.

The experimental investigation in this work concerns the compression-ignition (CI) engine combustion process both in normal operation and dual-fuel operation. There is a bulk of literature reporting thermal efficiencies, brake specific fuel consumption (BSFC) and emissions under single and dual fueling conditions in CI engines. Most of the studies lack the full implications of changing load (power output) and speed on these performance indicators. The studies are either restricted to various loads/powers at one engine speed (neglecting the effect of engine speed) or one or two load/power conditions at various speeds (neglecting load variations). There is a scarcity of full engine maps in the open literature (these are the full contours of thermal efficiency or BSFC plotted throughout the power versus speed range of the engine, or the torque versus speed range of the engine). This thesis provides performance and emissions maps for a CI engine using two different fuels (diesel and rapeseed methyl ester used as single fuels) and two gaseous fuels (natural gas and hydrogen) used with two different pilot fuels (diesel and rapeseed methyl ester ) under what is termed dual fueling mode. A novel approach is used to present the performance and emissions over the entire engines operational range. The results are presented as iso- contours of thermal efficiency, volumetric efficiency and brake specific NOX, specific HC and specific CO2 on a power-speed graph throughout the operating range of the engine. Many studies conclude that the emissions, particularly NOX during dual fueling are expected to form in the spatial region around the pilot spray. This region is expected to be subjected to high localised temperatures as the equivalence ratio is close to stoichiometric, thus maximising heat release from combustion. The effect of changing the pilot fuel quantity on performance and emissions is rarely reported. This study addresses this scarcity in the literature and investigates the effect of changing the pilot fuel quantity and type on various combustion and emission parameters. Diesel and rapeseed methyl ester (RME) have been used as pilot fuels for both the natural gas as well as hydrogen and three different pilot fuel settings have been employed for each of the gaseous fuels. The effect of using a different pilot fuel quantity to achieve the same brake mean effective pressure (BMEP) for the two gaseous fuels has been analysed and compared. This thesis also includes a chapter on the computational modeling of the engine esmissions. This study uses combinations of different spray and combustion models to predict in-cylinder pressure, rate of heat release and emissions. The approach employs two combustion models: Unsteady Flamelet Model (UFM) with PDF method and Finite Rate Chemistry (FRC) with stiff chemistry solver implemented through In-Situ Adaptive Tabulation (ISAT) algorithm. Two spray models used includeWAVE and Kelvin Helmohltz Rayleigh Taylor (KHRT) spray models. The UFM coupled with KHRT spray model has been used to predict NOX, CO and CO2 emissions. The model captures the emissions trends well. In-cylinder contours of O2, NO and mass average temperature have also been presented. A chemical mechanism of n-heptane with 29 species and 52 reactions has been used.

The thesis presents investigations of advanced combustion strategies in a modern V6 diesel engine fuelled with mineral diesel and Tallow Methyl Ester (TME)-diesel blends, in order to meet future emissions legislation. One of the main objectives of this research is to improve fuel consumption whilst minimising engine emissions through the combined effects of injection strategy (fuel injection pressure, dwell period, pilot fuel quantity) and cooled Exhaust Gas Recirculation (EGR) on a modern V6 common rail direct injection diesel engine. In the case of using EGR (49–52%) at 1500 rpm and 10% of engine peak torque, by increasing the fuel injection pressure from 300 to 800 bar, engine thermal efficiency increased from 16.5 to 19.1% and 17.1 to 19.7%, BSFC decreased by 13.5% and 13.2%, smoke level decreased by 74.3% and 70.1% and NOx emissions increased by 69.6% and 68.0%, respectively for a short (5 CAD) and a long (40 CAD) dwell period. In addition, the study of a variation of pilot fuel quantities (0.8–3.0 mg/stroke) with a fixed dwell period (5 CAD) at two different fuel injection pressures (250 bar and 800 bar) shows that the smaller pilot quantity with the higher fuel injection pressure can be considered as an enhanced strategy to control engine performance and emissions simultaneously. Therefore, the combination of higher injection pressure, longer dwell, smaller pilot quantity and the use of EGR could potentially improve fuel consumption and minimise engine emissions. The use of TME-diesel blends results in lower engine thermal efficiency and higher fuel consumption and NOx emissions. In the case of 1500 rpm and 25% of engine peak torque, the combustion of TME10 and TME30 reduced the engine thermal efficiency from iii 35.3 to 33.7% and 35.3 to 33.2% and increased the BSFC by 4.9% and 6.5%, respectively. At the same engine condition, the combustion of TME-diesel blends increased NOx emissions by 1.8% and 10.0% and reduced CO by 0.9% and 1.8%, THCs by 18.0% and 23.9 %, smoke by 30% and 51.7% for TME10 and TME30 respectively. However, the engine thermal efficiency, BSFC and NOx emissions could be improved with the application of the combined effect of injection strategy (fuel injection pressure, dwell period, pilot fuel quantity) and EGR as shown in the first phase of this study.

Because of the long service expected from steam power plant it is not practicable to obtain creep data from prototype installations to assist design against excessive creep. Model techniques, however, allow accelerated creep testing in a laboratory environment, which will produce the required creep information in a period of weeks rather than years. Models are made of a lead alloy and subjected to the scaled mechanical service loads at room temperature. Similarity conditions, based on the usual stress-strain-time relationships, have been developed which allow the measured strain distribution to be used to predict the strains in the engineering component at any time during its useful service life. This prediction requires only the uniaxial creep characteristics of the model and component materials. At present the technique is limited to constant temperature conditions. A lead-antimony-arsenic alloy has been selected which can be cast in the laboratory, giving good homogeneity, isotropy and fine grain structure; this material shows sufficient creep strain due to conveniently small stresses at room temperature. The steady load stress-strain-time characteristics have been determined from uniaxial tests. The model technique has been used to study simplified steam turbine casings subjected to internal pressure. The shapes tested consisted of axially split, flanged cylinders with domed end closures containing large bossed central bores to simulate the turbine bearings and glands. The loading of the models was due to the bolting forces and due to internal pressure. Strains on the inner and outer surfaces were measured with electric resistance strain gauges.

The finite element method has been used to calculate the stresses and creep deformations of flanged turbine casing models subjected to internal pressure and bolting forces. The finite element results have been compared with results from photoelastic and lead model turbine casings. An axisymmetric thin shell of revolution ring finite element has been developed to analyse casings subjected to pressure, thermal and creep loads. The thin shell of revolution ring finite element is shown to be extremely powerful and has been used to investigate the shell portions of the turbine casing away from the flange. The three-dimensional isoparametric finite elements have been used for more accurate idealisations of the turbine casing. A thick shell isoparametric finite element has also been developed which can be used with the more common hexahedral isoparametric finite elements. A solution algorithm based on a frontal technique has been developed to solve the large number of linear equations given by the finite element equations. This algorithm, which is fully automatic and uses fast access backing store, has a resolution facility which is used to recalculate subsequent creep solutions assuming that the stiffness of the structure remains constant. The creep algorithms are based on time marching techniques where the creep solutions are found for small time increments, the final solution being the sum of all the incrementa1 solutions. During each time increment the stresses are assumed to remain constant and the change in stress between time increments is kept within a preset ratio. The creep algorithms have been used to predict the creep deformation of simple structures to compare with published results. The agreement between the finite element and lead model creep results is limited. The finite clement programs have been written to be compatible with the PAFEC suite of finite element programs.

The work described In this then is was initiated in response to motivation from the needs of industry, the desire to investigate the performance of a process control computer in a relatively novel application as well as to provide training in methods of research. Ever-increasing labour costs have caused the automotive and petroleum industries to seek new means of maintaining the throughput of engine testing work. Their task has been made more difficult by the stringent test regulations that have been introduced with the very commendable intention of reducing atmospheric pollution. In consequence, any means by which the efficiency of testing could be improved and the throughput of work increased were deemed worthy of investigation. Engine testing involves a diversity of simple repetitive operations. These include the collection and processing of data and the execution of logical operations. The digital computer has proved itself to be ideally suited to performing such tasks, but the problem of integrating a computer with such an activity remains only partially solved. It is hoped that the work described in this thesis will go some way towards solving this problem. A description of the instrumentation and interfacing used on the test rig is included together with a description of the program structure and functions. These are not regarded as exemplary but it is hoped that they will aid the identification of the requirements for similar systems. A linearised mathematical model is developed to represent both the static and dynamic behaviour of the engine and dynamometer. This aspect of the study has provided useful insight into the problems associated with the control of engine test rigs. As a result it has been shown that effective control can be made available without recourse to highly sophisticated techniques. Optimisation systems as applied to the control of spark timing and mixture strength are considered. The limitations imposed on their operation by the inherent nature of combustion are outlined. Finally some computer controlled tests that were implemented are described as a means of illustrating the very extensive capabilities of such a system.

The value of integrating a heat storage into a geothermal district heating system has been investigated. The behaviour of the system under a novel operational strategy has been simulated focusing on the energetic, economic and environmental effects of the new strategy of incorporation of the heat storage within the system. A typical geothermal district heating system consists of several production wells, a system of pipelines for the transportation of the hot water to end-users, one or more re-injection wells and peak-up devices (usually fossil-fuel boilers). Traditionally in these systems, the production wells change their production rate throughout the day according to heat demand, and if their maximum capacity is exceeded the peak-up devices are used to meet the balance of the heat demand. In this study, it is proposed to maintain a constant geothermal production and add heat storage into the network. Subsequently, hot water will be stored when heat demand is lower than the production and the stored hot water will be released into the system to cover the peak demands (or part of these). It is not intended to totally phase-out the peak-up devices, but to decrease their use, as these will often be installed anyway for back-up purposes. Both the integration of a heat storage in such a system as well as the novel operational strategy are the main novelties of this thesis. A robust algorithm for the sizing of these systems has been developed. The main inputs are the geothermal production data, the heat demand data throughout one year or more and the topology of the installation. The outputs are the sizing of the whole system, including the necessary number of production wells, the size of the heat storage and the dimensions of the pipelines amongst others. The results provide several useful insights into the initial design considerations for these systems, emphasizing particularly the importance of heat losses. Simulations are carried out for three different cases of sizing of the installation (small, medium and large) to examine the influence of system scale. In the second phase of work, two algorithms are developed which study in detail the operation of the installation throughout a random day and a whole year, respectively. The first algorithm can be a potentially powerful tool for the operators of the installation, who can know a priori how to operate the installation on a random day given the heat demand. The second algorithm is used to obtain the amount of electricity used by the pumps as well as the amount of fuel used by the peak-up boilers over a whole year. These comprise the main operational costs of the installation and are among the main inputs of the third part of the study. In the third part of the study, an integrated energetic, economic and environmental analysis of the studied installation is carried out together with a comparison with the traditional case. The results show that by implementing heat storage under the novel operational strategy, heat is generated more cheaply as all the financial indices improve, more geothermal energy is utilised and less fuel is used in the peak-up boilers, with subsequent environmental benefits, when compared to the traditional case. Furthermore, it is shown that the most attractive case of sizing is the large one, although the addition of the heat storage most greatly impacts the medium case of sizing. In other words, the geothermal component of the installation should be sized as large as possible. This analysis indicates that the proposed solution is beneficial from energetic, economic, and environmental perspectives. Therefore, it can be stated that the aim of this study is achieved in its full potential. Furthermore, the new models for the sizing, operation and economic/energetic/environmental analyses of these kind of systems can be used with few adaptations for real cases, making the practical applicability of this study evident. Having this study as a starting point, further work could include the integration of these systems with end-user demands, further analysis of component parts of the installation (such as the heat exchangers) and the integration of a heat pump to maximise utilisation of geothermal energy.

The current study is part of a long term experimental project devoted to investigating single-phase flow pressure drop and heat transfer, flow boiling pressure drop and heat transfer, flow boiling instability and flow visualization of de-ionized water flow in microchannels. The experimental facility was first designed and constructed by S. Gedupudi (2009) and in the present study; the experimental facility was upgraded by changing the piping and pre-heaters so as to accommodate the objectives of the research. These objectives include (i) modifying the test rig, to be used for conducting experiments in microchannels in single and two-phase flow boiling heat transfer, pressure drop and visualization, (ii) redesign metallic single microchannels using copper as the material. The purpose of the redesign is to provide microchannels with strong heaters, high insulation performance and with test sections easy to dismantle and reassemble, (iii) obtaining the effect of hydraulic diameter on single-phase flow, flow pattern, heat transfer and pressure drop, (iv) studying the effects of heat flux, mass flux,and vapour quality on flow pattern, flow boiling heat transfer and pressure drop, (v)comparing experimental results with existing correlations. However, the main focus in this present study is to investigate the effects of hydraulic diameter, heat flux, mass flux and vapour quality on flow pattern, flow boiling heat transfer coefficient and pressure drop. In addressing (iii) many possible reasons exist for the discrepancies between published results and conventional theory and for the scatter of data in published flow boiling heat transfer results: 1. Accuracy in measuring the dimensions of the test section, namely the width, depth and length and in the tested variables of temperature, pressure, heat flux and mass flux. 2. Variations in hydraulic diameter and geometry between different studies. 3. Differences in working fluids. 4. Effects of hydrodynamic and thermal flow development 5. Inner surface characteristics of the channels. Three different hydraulic diameters of copper microchannels were investigated: 0.438mm, 0.561 mm and 0.635 mm. For single-phase flow the experimental conditions included mass fluxes ranging from 278 – 5163 kg/m2 s, heat fluxes from 0 - 537 kW/m², and inlet temperatures of 30, 60 and 90°C. In the flow boiling experiments the conditions comprised of an inlet pressure of 125 kPa (abs), inlet temperature of 98°C (inlet sub-cooling of 7 K), mass fluxes ranging from 200 to 1100 kg/m²s, heat fluxes ranging from 0 to 793 kW/m² and qualities up to 0.41. All measurements were recorded after the system attained steady states. The single-phase fluid flow results showed that no deviation of friction factors was found from the three different hydraulic diameters. The effect of fluid temperature on friction factor was insignificant and the friction factors themselves were in reasonable agreement with developing flow theory. The typical flow patterns observed in all three test sections were bubbly, slug/confined churn and annular, however, based on the observation performed near the outlet, the bubbly flow was not detected. The effects of mass flow and hydraulic diameter on flow pattern for the three test sections investigated in the range of experimental conditions were not clear. The single-phase heat transfer results demonstrated that smaller test sections result in higher heat transfer coefficients. However, for heat transfer trends presented in the form of Nusselt number versus Reynolds number, the effect of hydraulic diameter was insignificant.The flow boiling experiments gave similar heat transfer results; they exhibited that the smaller hydraulic diameter channels resulted in higher heat transfer coefficients. The nucleate boiling mechanism was found for all three test sections, evidenced by the significant effect of heat flux on the local heat transfer coefficient. Moreover, the heat flux had a clear effect on average heat transfer coefficient for the 0.561 mm and 0.635mm test sections, whilst for the 0.438 mm test section, there was no discernible effect. At the same heat flux, increases in mass flux caused heat transfer coefficients to decrease. This could be due to the decrease of pressure inside the test section. When a higher mass flux was tested, the inlet pressure increased, and in reducing the inlet pressure to the original value, a decrease in system pressure resulted. Consequently, the outlet pressure and local pressure became lower. Existing flow pattern maps, flow boiling heat transfer and pressure drop correlations were compared with the experimental results obtained for all three test sections. The comparison showed that the flow pattern map proposed by Sobierska et al. (2006) was the most successful in predicting the experimental data. The local heat transfer coefficient data were compared with existing published correlations. The correlations of Yu et al. (2002), Qu and Mudawar (2003) and Li and Wu (2010) are found to predict the current local heat transfer coefficient better than other correlations tested. Pressure drop results showed that as the heat flux and mass flux were increased, the two-phase pressure drop increased too. These were due to the increase in bubble generations and the inertia momentum effect. As the channel was reduced, the twophase pressure drop increased because the pressure drop related inversely with the channel hydraulic diameter. The pressure and pressure drop fluctuations were indentified in this project, however, the maximum pressure fluctuation was found in the 0.438 mm channel whilst the minimum fluctuation was attained in the 0.561 mm channel. This indicated that the effect of decreasing in hydraulic diameter on pressure and pressure drop fluctuations is not clear and needs to be investigated further. The two-phase pressure drop data were compared with selected correlations. The Mishima and Hibiki (1996)’s correlation was found to predict the current two-phase pressure drop better than the other correlations examined in this study.

Heat energy is important to all aspects of life. Various industries including food processing plants, chemical processing plants, thermal power plants, refrigeration and air conditioning equipments, petrochemical plants, etc. are faced with the problems of effective utilization, conservation and recovery of heat. The production of heat exchangers involves huge investments for capital and operation costs. In view of this, it has become important to design heat exchangers that will be efficient and also save energy, cost and materials. Different techniques known as heat transfer enhancement are employed to achieve this. Of these techniques, the tube-insert technology is applied in the present research. No prior work on heat transfer and fluid flow in a tube induced with twisted tape insert with emphasis on cuts with different geometrical shapes but equal area has been reported. Hence, in the present work, heat transfer and fluid flow of water in tubes induced with twisted tape inserts with different-shape-equal-area cuts is investigated numerically. The present studies pay attention to the thermo-hydraulic characteristics of laminar, transitional and turbulent flows of water through different tube designs fitted individually with twisted tape of different design under uniform wall heat flux. The numerical simulation in this work is carried out by using Fluent software. The RANS-based RNG κ-ε model is employed for the turbulent flow because it is found to give a more accurate result than other turbulence models. Since transitional flow is not fully turbulent, the transitional variant of the SST κ-ω model is applied for the simulation of the transitional flow. The analyses quantify the improvement in the heat transfer, friction factor and thermal performance index in each of the tube systems and these results are used to ascertain the system that gives the best performance. Correlations are also proposed for the Nusselt number and friction factor. The results indicates that the superior fluid mixing provided by the alternate-axis triangular cut twisted tape is one of the reasons why it offers heat transfer enhancement and thermal performance factor that is higher than those that are offered by other induced tubes. Interestingly, the enhancement in heat transfer increases as the size of the cuts on the tape and the width of the tape increase but decreases as the pitch of the tape increases. The enhancement of heat transfer affects the start and the end of the transition to turbulent flow. Transition to turbulent flow occurs and ends earliest in the tube system with the highest heat transfer enhancement. Investigation is also performed on the combined forced and free convection heat transfer in an inclined tube for laminar, transitional and turbulent flows. The induced tube is inclined at different angles (15o≤θ≤90o ) with respect to the horizontal. Importantly, the heat transfer enhancement of the tube systems under mixed convection is higher than those under forced convection, and the enhancement for the mixed convection increases as the inclination angle increases.