The effect of inlet conditions on the performance of conical diffusers is considered. The conditions at inlet which were independently varied are the cross-sectional time-meaned velocity distribution and the associated stream turbulence variation. The investigation formed part of a research programme on interaction effects between pipe and duct components. Sources of data on the effect of such variants include Kline, Winternitz, Livesey, Miller and Cockrell amongst others. Whereas these persons considered the symmetrical profile developments accompanying varying inlet pipe lengths and Reynolds numbers, Tyler and Williamson examined the effects of distorted time-mean velocity profiles at inlet. A very limited amount of experimental work has been published by Kline et al on the effect of varying the free stream turbulence intensity at the diffuser inlet when the associated boundary layer thickness is small. The thesis considers this previous work, then describes the development of a turbulence generator with which a mean velocity distribution, barely distinguishable from fully-developed flow is obtained in a few pipe diamters. This mean velocity is accompanied by a turbulence intensity which is capable of being increased up to three times that normally associated with fully-developed flow. Conical diffusers were mounted downstream of the turbulence generator and pressure recovery characteristics over a wide range of expansion angle and area ratio were obtained. In general the results show a significant increase in pressure recovery over values associated with normal fully-developed inlet flow. An integral computational method is developed for ducts, pipes and conical diffusers which leads to successful predictions of boundary layer growth and diffuser pressure recovery for a wide variety of inlet boundary layer thicknesses. Possible extensions of this method to admit inlet turbulence level as a parameter which influences diffuser pressure recovery are considered. The thesis discusses how variations in mean velocity profiles and turbulence levels at the diffuser inlet are significant parameters in the current industrial context.

The work presented is concerned with investigations into the use of a refreshable graphical display for the solution of design and analysis problems in engineering. Effort has been devoted to the study and implementation of a variety of applications in an attempt to identify the most suitable techniques, form of program organization and hardware configuration for this type of equipment. General topics pertinent to these investigations, including data structuring, graphical communication and some general principles of software design, are discussed. The applications which are presented are: (a) LUISA, a system for finite element analysis of two-dimensional engineering structures, (b) TDD, a set of programs for three-dimensional drawing, written to investigate a number of methods of communicating with a three-dimensional model, (c) BAID, a program for aiding the architect with the design of high density housing layouts, (d) An outline of a system for generating the data input for three-dimensional finite element analysis of solid and shell structures. A detailed description is included of a paging scheme used to segment the data structure. The data structure employed and scope of facilities provided are described for each of the applications. Discrete representation of engineering components is shown to be ideally suited to the organization of data in structured form both in the computer core store and on secondary storage. A description is given of some devices, provided by software and making use of the lightpen, which allow development of dynamic techniques for graphical communication with a digital model. A modular approach to software design is advocated, with advantage being taken of general packages, wherever possible, for administration of interaction handling and data organization. Proposals are made about the re-arrangement of the applications dealt with in order to implement them on a remote satellite computer configuration. Suggestions are made about the size of such a configuration and the organization of software in the two machines.

This work describes a method of controlling a slip-ring induction motor so as to provide characteristics suitable for hoist drive applications. The primary of the machine was supplied from a three-phase voltage regulator which in addition to producing a motoring torque can also provide plug braking by phase reversal and dynamic braking by d.c. injection. The hoist drive characteristics are of a constant torque nature and these were obtained by the control of a variable duty cycle forced commutated thyristor chopper in the secondary circuit of the motor. The operation of the voltage regulator has been examined for a load consisting of a delta wound induction motor. A simple model of the regulator has been developed from which speed-torque characteristics have been determined. Analysis of the operation of the motor and thyristor chopper was used to determine the appropriate relationship between duty cycle and speed necessary to produce a constant torque characteristic. This relationship was realized by a function generator which was used to control the thyristor chopper. Closed loop control of motor speed by the voltage regulator combined with open loop operation of the thyristor chopper as a function of speed gave the required constant torque characteristic. Logic circuits were incorporated in the design to allow automatic selection of the motoring and braking modes. The four-quadrant controller has been designed and successfully operated throughout the required speed range. The operation of the controller has been considered from both steady state and dynamic aspects.

This dissertation is mainly concerned with cycloconverter -induction-motor variable-speed drives. Hitherto, the cycloconverter has been at a disadvantage compared with other types of solid-state frequency converters because of a) the number of devices required, and b) the tendency for line to line short-circuit faults. In a simple system devised in this work, the number of devices is reduced by 2-phase, 3-thyristors per group basic design and line to line short-circuit faults are prevented by the design of a special stator winding with electrically-separate, magnetically-coupled thyristor group circuits. The requirements of thyristor gate circuitry have been considered and circuits have been devised to meet the requirements of the experimental system. A study of the harmonic content of the cycloconverter output voltage has been made and its effect on the machine performance and efficiency examined. The performance and stability of cycloconverter-induction motor-drives and cycloconverter-reluctance-motor drives have been considered and it has been shown that while a closed-loop, variable- speed induction motor drive is inherently stable, a cycloconverter- reluctance motor drive can become unstable at low speeds and loads. A method of simulating cycloconverter-induction-motor-drives to enable the performance of large power drives to be predicted has been investigated, although it has not been possible to fully implement the simulation. Electrical braking in cycloconverter-induction-motor drives has been investigated and methods of achieving zero-sequence characteristic a.c. braking and optimum low-frequency a.c. braking have been devised.

The standard synthesis techniques are limited in that they cannot deal effectively with either parasitic elements or constraints and in that the range of networks they can adequately synthesise is limited. The computer makes it practical to use methods of directed trial and error which do not have these limitations, such as network evolution. Network evolution is a process by which changes occur in both the network topology and in the values of the network elements in such a way as to drive an objective function (some measure of the error between current and required response) to ever lower values and ultimately solution. In this case the error arises from the matching of the current set of coefficients of the network polynomials with their respective required values. This comparison produces a set of nonlinear equations which on solution give a suitable network topology and element values. These non-linear equations require optimisation techniques for their solution. It is shown that network evolution by coefficient matching is feasible in processes which primarily work either by network growth or by network reduction. The process of network growth works by taking a primitive starting network having the correct network polynomial structure and eliminating and growing elements at the appropriate state of development until a satisfactory solution is obtained. The method of analysis used, in addition to being both accurate and rapid, also gives the sensitivity of the coefficients with respect to virtual zero-valued elements. Use of this information enables a suitable choice of type, place in network and value of element to grow. The network reduction process takes initially a network which produces the required network polynomials, but with redundant common factors, and pares away the excess elements by making them open or short circuit, simultaneously removing excess common factors, until a suitable network is obtained. Suggestions are made on ways of improving the evolutionary process and increasing its scope.

Known methods of generating arynes, and their chemical reactions, have been classified, and some new syntheses and reactions are described. A series of substituted 1-aminobenzotriazoles were synthesised from the corresponding o-nitroanilines by considerable modification of the literature method. These compounds were also synthesised by the amination of the corresponding benzotriazoles, using hydroxylamine-o-sulphonic acid. This reaction afforded the isomeric 2-aminobenzotriazole in the unsubstituted case only. Oxidation of the substituted 1-aminobenzotriazoles with lead tetra-acetate was accompanied by elimination of nitrogen from the nitrene initially formed, to yield the free aryne. The degree of dimerisation of the arynes, to give the corresponding biphenylenes, was found to vary with the substitution of aryne. 3-Nitrobenzyne afforded no dimer, forming instead 3-nitrophenyl acetate. Benzyne and 4-methoxybenzyne were shown to react as a symmetric singlet by the stereospecificity of the reaction with trans, trans-hexa-2,4-diene. Evidence for the existence of 3-nitrobenzyne in this electronic state was also found; semi-empirical calculations predicted benzyne, 4-nitrobenzyne and 3-nitrobenzyne to exist in the singlet ground state. The reactivities of several arynes were compared by the relative degree of 2 + 2 cycloaddition to vinyl acetate. 3-Nitrobenzyne was found to be highly reactive; semi-empirical calculations showed that this species had an unusually high dipole moment, and the reactivity was explained in terms of the polarity between the non-bonded o-orbitals. Evidence for the intermediacy of 2,2'-dehydrobiphenyl in the dimerisation of benzyne was found. Certain arynes cleaved dialkyl ethers to give the phenyl alkyl ether. The "ene" reaction was extended to acetylenes, phenyl allenes being the products. Evidence for the existence of a transient ruthenium-benzyne complex was found, as was evidence of interaction between benzyne and silver or mercury.

In the Introduction to this thesis the steady flow of Newtonian fluids in duct systems is discussed, with particular consideration to rectangular section bends. The considerable economic savings, both capital and annual that can be obtained by a small reduction in the head loss of an individual system element is indicated. Reliable experimental data on the value of head loss coefficients for incompressible fluid flow through rectangular section bends is very limited and correlation of different experiments is almost impossible because of the different definitions of loss coefficient and the various experimental procedures used. At present theoretical methods of analysing the three-dimensional flow problem occuring in a bend are non-existent and only a limited contribution is made by two-dimensional approaches. Reasons for this situation are discussed together with possible areas for future development. A computer based data logging instrumentation system is used to record the necessary data required to calculate the value of the bend loss coefficient for various combinations of inner and outer radius ratio. The aspect ratio and Reynolds number of 2 and 2 x 105 respectively are representative of a number of practical situations. An indication of the accuracy of the values of bend loss coefficient quoted is given by the corresponding uncertainty interval which is based on that selected, for given confidence limits, in the collected data. For the combinations of inner and outer radii the variable area bends are modelled by a combination of a diffuser, constant area bend and a contraction in the above or reversed order. The calculated value of the model loss coefficient agrees surprisingly well with the experimental values. Based on the extension of the model calculations the optimum geometrical shapes for circular cross-section 90° bends are suggested.

The experimental techniques for the measurement of thermal conductivity of gases at very high temperatures were examined. Using a wall stabilised are the thermal conductivity of argon and nitrogen was measured in the temperature range 8000-16,000°K and compared with published experimental and theoretical data. Reasons for the very significant discrepancies between theory and experiment at the higher temperature end of the range examined were sought and the importance of thermal radiation demonstrated. The problems involved in including the thermal energy contribution to the arc energy balance were examined together with the measurement and calculation of the radiation density. A method for the direct measurement of viscosity using the wall stabilised arc was examined and a new method for the measurement of velocity in high temperature gases was developed. Following the experimental measurement of gas properties, the problems involved in their theoretical prediction were examined. A new method of calculation of thermal conductivity and viscosity of gases with non-frozen composition was developed which, whilst maintaining a high level of accuracy in the temperature range up to about 18,000°K in argon and nitrogen at atmospheric pressure offered a very considerable simplification and reduction in labour over other published methods. The final section of this study was concerned with the evaluation of electron-proton and electron-ion collision data in the arc. The absorption of electromagnetic radiation produced by low power He-Ne and GaAs lasers was used to make the measurements; the importance of the electron-ion collisions being clearly demonstrated in this work.

The thesis describes a wind-energy transducer system based on a doubly-fed, slip-ring machine and a cycloconverter operating with continuous circulating current. A theoretical analysis and experimental verification of the system have been carried out with a simulated wind turbine. Points 1 to 8 list the points covered and work carried out: The author has: 1) Surveyed existing wind energy transducers connected to the grid. 2) Developed an original theory of the doubly-fed machine operating as a generator. 3) Modified the doubly-fed generator theory to allow the generator to generate power proportional to the cube of its speed. 4) Computed a field voltage control function necessary to maintain cube-law generation at optimum power coefficient. 5) Further developed the generator theory to show that constant current excitation greatly reduces the induction power and permits the economic selection of electronic devices. 6) Designed and implemented digital and analogue electronic systems to satisfy the requirements of points (3) and (4) and to operate the system at optimum efficiency. 7) Successfully applied the cycloconverter, divided winding principle to the doubly-fed generator to provide a system able to withstand shock wind gusts over a wide-speed range. 8) Discussed the extrapolation of the system to large powers.

This thesis is concerned with the behaviour of structures subjected to cyclic or repeated thermal loading in the presence of steady mechanical loads. The present work consists of four main parts; in the first part, the thermal loading problems and the possible solution methods are discussed. The development of shakedown theory and its applications are reviewed with particular attention on the case of thermal actions. By utilising the upper bound shakedown theorem and assuming a broader range of shakedown conditions, a new extended upper bound technique for estimating the extent of plastic shakedown (reversed plasticity) region is developed. The occurrence of the structural and material shakedown and a related structural theory which indicates whether a reversed plasticity region exists, are discussed. In the second part, the influence of cyclic hardening and temperature dependents of material properties on the modes of behaviour of two representative kinematically determinate structures; namely a parallel two-bar assembly and a Bree plate are investigated by means of an empirical cyclic hardening material model and the theory, developed in the first part. Comparing the available experimental data on a two-bar structure with the predictions of perfect plasticity, complete cyclic and cyclic hardening models it is argued that the use of perfect plasticity model may not -always guarantee the safe performance above the shakedown limits. In this region the use of complete cyclic hardening model gives conservative boundary whereas the cyclic hardening model gives the most appropriate boundary. The analytical solutions for the Bree plate with temperature independent material properties show that the boundary between the reversed plasticity and ratchetting is insensitive to the hardening assumption. The influence of the transient thermal loading and the effects of multi-axial state of stress on the Bree solution are also studied. The applications of the upper bound technique to the problems involving transverse and in plane loading in plates are presented and the importance of the shear stresses in this type of loading conditions are emphasized. In the third part, a finite element technique for the computing of shakedown limits and estimation of the corresponding mechanisms of deformation for kinematically highly indeterminate structures is developed. Presenting the main features of the technique which is based upon the upper bound shakedown theorem and linear programming, a number of solutions are given to specific problems to illustrate the types of problems which may be solved by the technique. Some recently reported experimental data on a tube under axisymmetrical loading is compared with the present analytical predictions. Finally, the conclusions and the proposals for future work are presented in the fourth part.