The motivation for this investigation into microturbine and desalination processes is the desire to combat problems caused by frequent high temperature conditions related to the spread of global warming. The small-scale power microturbine C200, designed by the Capstone Co., was chosen. Also, a single effect absorption chiller was employed in this study. The method of thermal vapor compression multi-effect distillation desalination was chosen as a potable water producer. Also, the organic Rankine cycle was powered by low-grade heat energy. Each model was simulated and investigated on a stand-alone basis under ISO conditions using off-design simulations. The ORC, absorption chiller and TVC-MED desalination process were separately driven with the same amount of fuel consumption into microturbine. All the base and proposed models were simulated by using a software package called IPSEpro. The economic accessibility and profitability of all the proposed models was examined. Integrating the microturbine with the ORC unit led to the generation of an extra 4.10% of electric power compared to that produced by the absorption chiller, and 7.80% for TVC-MED desalination. However, the lowest carbon emission rate for all models was achieved by using a microturbine with TVC-MED desalination with a reduction of 46.80%. Accordingly, the EUF of the TVC-MED desalination was 9.20% higher than when an absorption chiller was used, and 42.40% higher than when ORC was used. ORC gained the lowest EUF. The higher rate of exergetic efficiency was found when utilising the microturbine with the single effect absorption chiller with a value of 31.00%, as compared to ORC and TVC-MED, which registered rates of 23.11%, and 22.42% respectively. The results of economic study showed that, if the selling price was £0.023/kWh, then the profitability evaluation results would not be attractive for investment. However, if investment was made into a microturbine, then the electricity price could be set at £0.040/kWh or £0.060/kWh, resulting in a desirable economic feasibility for all combined models.

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Access to energy is fundamental to civilisation, both as economic and social yTL development. This is fuelling a growing demand for reliable, affordable and clean energies. The current problems related to climate change have made imperative the search of technologies that can produce higher amounts of energy at lower emission rates. Therefore, technologies such as swirling flows with premixed lean injection have been characterized as one of the most reliable to achieve this objective. However, the use of this technology implicates the appearance of phenomena that have been barely studied such as the manifestation of coherent structures that are crucial for the stability and high efficiency of the combustion process, and which have been assumed from indirect measurements. Moreover, these structures have been recognised as major players in the generation of instabilities such as pressure and heat transfer variations, internal vibrations and flashback into the mixing chambers. Therefore, a better understanding of these structures will allow the design of better burners and a greater control over the former, permitting a more efficient process. This project is intended to reveal some of the characteristics of these structures, showing their high 3 dimensionality and high dependence on geometrical parameters, equivalence ratio, Swirl and Reynolds numbers, amongst other factors. It is recognised how under isothermal conditions the system produces strong Precessing Vortices that are fundamental in the final shape of the flow field, while the Central Recirculation Zones are dependent on the pressure decay ratio inside of the combustion chamber. Combustion conditions showed the high dependence on the method of fuel injection used, with the appearance of stronger structures at lower equivalence ratios when high amounts of premixed gas were pumped into the system and the change in shape of the recirculation zones by using different injectors. Flashback demonstrated to be a factor highly related to the strength of the Central Recirculation Zone for those cases where a Combustion Induced Vortex Breakdown was allowed to enter the swirl chamber, whilst cases where a bluff body impeded its passage showed a considerable improvement to the resistance of the phenomenon. The use of nozzle constrictions also reduced flashback at high Re. All these results were aimed to contribute to better designs of future combustors.

The shock tube test programme has shown that detonation initiation is achievable for gaseous fuel-air mixtures with a reflected shock. The presence of a shaped reflecting face enhances combustion initiation significantly. Combustion initiation has been demonstrated for a liquid kerosene-air mixture with a flat reflecting face, suggesting that the presence of a shaped reflecting face will lead to detonation. In addition, the numerical simulation programme has evaluated the fuel-air mixing characteristics of the prototype Pulse Detonation Engine and made recommendations for improvements. The droplet breakup study has demonstrated that a liquid fuel-air mixture suitable for detonation propagation is achievable in the shock tube.

This thesis investigates over tip leakage where the tip clearance is large. In the high pressure stages of axial compressors the tip clearance can be typically 6% of span and the total blockage due to tip clearance can consume in excess of forty percent of the annulus height. Experimental and computational investigations of large tip clearance in a linear cascade have been used to investigate this phenomenon. Two cascade builds have been used the first (Build A) consisted of a controlled diffusion aerofoil of low stagger and thirty degrees flow turning. The second cascade (Build B) consisted of an engine representative design with high stagger and around ten degrees of flow turning. The diffusion factor of both cascades was around 0.3. The major findings are that: Large tip clearances have a smaller detrimental influence on single row performance than the previous research would have suggested, for Build B the loss at 10% tip clearance was the same as the 0% tip clearance loss, though the overall flow turning was much reduced. An increase in blade loading towards the tip was observed with both builds. Both these phenomenon were attributed to the small amount of movement of the over tip leakage vortex. An engine representative level of inlet skew was implemented using upstream injection so to assess its influence. This was found to have a remarkably small influence on the performance of a single row with the tip clearance and geometry of the blading having a much greater influence. Finally a circumferential grooved casing treatment was applied in the linear cascade but this was found not to be an appropriate tool for such an investigation.

The complex nature of turbomachinery flows and the scale of associated flow phenomena such as shock waves and vortex shedding, apply constraints to the methods by which the flow can be analysed experimentally. Computational techniques have quite successfully been applied to the flow around turbine blades, but the transient and periodic phenomena observed in experimental studies have not been fully investigated. In this work an original working computational code is presented for time-resolved flows around turbine cascades. The code has been verified using test cases relevant to transonic flow. Some of the problems associated with computational techniques have been highlighted; these include the large number of schemes that are available, each with its own advantages and disadvantages. The code has been applied to a geometry representing highly loaded turbine blading currently under study at the National Research Council of Canada; this was also used extensively in previous computational and experimental investigations. The blading chosen has a relatively thick trailing edge, necessitated by cooling considerations. A distribution of the flow properties on the surface of the blade has been determined, from which an equivalent water table model has been designed based on the principle of the hydraulic analogy. The water table model thus generated represents a further method for experimentally investigating flow phenomena without the complexity of analysing very high frequency oscillations in situ. The timeresolved flow field has been computed showing unsteady phenomena. The unsteady phenomena have been shown to compare favourably with the unsteady features observed in preliminary experimental results. In the process, energy separation has been predicted to occur not only in the coupled wake region, but also for the first time within Kelvin-Helmholtz instabilities present in the trailing edge shear layers.

Quality and reliability is one of the most important issues. in power generation and distribution. With the recent advances in computer and network technology, the Operational Information Systems (OIS) have been installed in almost all power plants and substations. The data stored in databases covers long periods of time, which presents a challenge as how to extract the useful, task-oriented knowledge from the data to improve power system reliability and power quality. The thesis presents the research work in development of mathematical models for power systems by analysing the data available from on-site measurement using evolutionary computation techniques. The project contributes to aspects in power generation and distribution: coal mill modelling and electrical load area modelling. Coal-fired power stations are now obliged to vary their outputs in response to changing electricity demand and are required to operate more flexibly with more varied coal specifications. The operations of a mill need to be controlled to respond effectively to changes in plant load and coal quality. Combustion optimization relies heavily on optimization of the mill output. Frequently start-ups and shut-downs of mills bring the impact on power plant to achieve both low NOx and CO2 emissions. Operational safety and efficient combustion require better understanding to the milling process. The work described in the thesis has three new contributions: 1) Development of an improved normal grinding coal mill process model which provide more accurate prediction of mill states than the previous version; 2) Development of a new multi-segment coal mill model which covers the whole milling process from start-ups to shut-downs; 3) Development of a prototype software programme to implement the multisegment mill model on-line. The software has been passed to RWEnPower PIc. for further test. Stable operation of a power system depends on the ability to continuously match the electrical output of generation units to the electrical load. So it is important to have a reliable mechanism to predict the power load on time. Model based approach is one of the options. With the sponsorship from the National Grid Transco PIc, a study of modelling electricity area load has been carried out through this project A methodology using evolutionary computation techniques based on system measurements to construct power system area load models and achieve distribution network reduction is proposed in the thesis. Three aggregate load area model (ALAM) approaches entitled Voltage-Two-Step, Current-Two-Step and Direct-OneStep have been studied in the thesis. Simulations studies are carried out for these three approaches, and it found that the Direct-One-Step offers the best performance among the three ALAM approaches. Verification studies are performed through the project and some rules for constructing a good ALAM are obtained.

In the design of a gas turbine engine it is important to have a good prediction ofthe temperature distribution for components ofthe engine. This research work looks at the method ofpredicting air and metal temperatures of the lIP compressor disc drum. It is a common practice to supply cooling air for the turbine disc and blades by passing the air axially between the bores of adjacent discs in the lIP compressor. Some ofthe central axial throughflow is known to enter the compressor interdisc cavities and a parasitic temperature rise occurs in the throughflow air as a result ofthe convective heat transfer. It is important that the heat transfer mechanism within a compressor interdisc cavity is understood, as the engine designer needs to know the temperature ofthe cooling air and the disc temperatures in order to predict the stress and the life of the compressor, and also to predict the seal and blade tip running clearances.In this thesis, computational fluid dynamics (CFD) is used to study the flow and heat mechanism experienced by a gas turbine lIP compressor rotor. A review ofprevious research work and knowledge in the field of rotational buoyancy-driven flow has shown that the flow within the compressor inter-disc cavities is highly three-dimensional and time dependent in nature. Two approaches in the numerical modelling ofthe flow can be considered; one is to use CFD as a tool to model a single inter-disc cavity with axial throughflow in full three dimensions with unsteady flow. Using this approach requires a huge amount ofcomputational memory and time to run the CFD models. A second approach is to break down this complex flow process into separate physical mechanisms and introduce approximate but computationally efficient models for these processes. The second approach has been taken in this thesis, with the aim ofproducing a method that can be incorporated into current design practice. Two underlying flow mechanisms may be identified for this complex flow; the first associated with the flow within the inter-disc cavities and the second associated with the axial throughflow under the compressor disc bores.

An investigation into the feasibility of the free-piston engine concept and its potential for high efficiency and low emissions power generation has been conducted using computational modelling and simulation. A thorough background study and literature review was carried out covering previously reported experience with free-piston engines, particular features of this technology, and potential advantages and challenges associated with their design. A single piston free-piston engine generator was proposed as a result of the background study and a design strategy for this engine configuration was formulated. Detailed simulation models for the free-piston engine were developed and extensive simulation studies conducted to investigate the performance and operating characteristics of such an engine. Engine performance indicators, such as fuel efficiency, power to weight ratio, and exhaust gas emissions formation, were studied along with engine operational control issues. The results were directly compared to those of equivalent conventional crankshaft engines in order to investigate potential differences in engine performance. It was found that the free-piston engine has potential advantages over conventional technology in the areas of mechanical efficiency, exhaust gas emissions formation, and operational flexibility. The main challenge lies within the area of piston motion control and further research into engine control issues are required. A more detailed study of engine emissions formation is also recommended in order to fully understand the influence of the particular operating characteristics of the free-piston configuration on engine performance.

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