Wind energy is recognized as a sustainable source of energy that is both reliable and capable of dramatically reducing pollution to the environment and dependency on non-renewable fuels, leading to research on wind turbines. Nowadays, the demand for electricity increases. Considering that the greater the distance from shore, the greater the wind, more electricity will be generated along the coast. It is necessary and beneficial to study large scale offshore wind turbines. The National Renewable Energy Lab (NREL) 5-MW offshore wind turbine is simulated using a three-dimensional computational fluid dynamics (CFD) model in this article. A realizable k-ε viscous model is used to simulate turbulence flow. The work is validated by comparing the torque with published simulated data, and satisfied consistency is observed. Further simulation and comprehensive analysis demonstrate the flow features and aerodynamic performances of 5-MW offshore wind turbine under various wind and rotor speeds. The velocity profiles, total pressure distribution, pressure coefficient, rotor thrust, torque and aerodynamic properties are obtained in detail.

The aim of this thesis is to introduce the reader into theory, which is needed to make an aerodynamic calculation of flue gas part of steam boiler. On the back of the knowledge, project documentation and other entry parameters calculate sectional losses for each component and design a ventilator, that is suitable for our requirements.

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Due to renewed interest in the sub orbital rocket program of the Florida Space Authority and a surplus of Super Loki Sounding Rockets, an effort to improve the usefulness of this surplus is herein undertaken. Currently, the capacity of the payload compartment in the upper stage of the Super Loki system is very limited. A redesign of the upper stage will allow larger and more versatile payloads to be carried, assuming the appropriate design parameters are met. It has therefore been undertaken to create a design procedure that is comprehensive in scope in order to affect this redesign. This procedure includes five major components. These are the separation of the upper and lower stages, the stability of the vehicle, the altitude and velocity of the rocket, the mechanical loading and finally the aerodynamic heating. Semi-empirical methods were used whenever possible to allow comparison with experimental data. This procedure revealed that larger diameter upper stages might be used up to a reasonable maximum of four inches. The four-inch modification is found to be stable as were the smaller modifications considered. The altitude and velocity of the rocket were found via a simple Eulerian time stepping scheme resulting in an estimate of approximately 148,000ft for the four-inch dart. The mechanical loading analysis allowed for the material selection for the rocket components. Reinforced steel fins and carbon fiber tubing, for the payload section, are adequate to meet expected mechanical loads, those being, 16000psi for the fin section due to launcher forces, 22800psi for compressive plus torsion forces on the composite section and 18000psi for the ejection stresses. An ablative coating is considered necessary to counteract the 760ºF temperatures along the composite tube.

The phenomena of stall and surge in axial-centrifugal compressors is investigated through high-response measurements of both the pressure field and the flowfield throughout the surge cycle. A unique high-response forward-facing and aft-facing probe provides flow information. Several axial-centrifugal compressors are examined, both in compressor rigs and engines. Extensive discussion is presented on the differences in axial and centrifugal rotors and their effect on the system response characteristics. The loading parameters of both are examined and data is presented that shows the increased tolerance of the centrifugal stage to instability. The dynamics of the compressor blade response are shown to be related to the transport time of a fluid particle moving through a blade passage. The data presented provides new insight into the dynamic interactions that occur prior to and during stall and surge. In addition, the inception of rotating stall and the inception of surge are shown to be the same phenomena . An analytical dynamic model (DYNTECC) is applied to one of the compression systems and the results are compared to data. The results show that the model can capture the global effects of rotating stall and surge. The data presented, along with the analytical results, provide useful information for the design of active and passive stall control systems. / Ph. D.

A linear model based on the wave-envelope technique is used to study the propagation of axisymmetric and spinning acoustic modes in hard-walled and lined nonuniform circular ducts carrying near sonic mean flows. This method is valid for large as well as small axial variations, as long as the mean flow does not separate. The wave-envelope technique is based on solving for the envelopes of the quasiparallel acoustic modes that exist in the duct instead o£ solving for the actual wave, thereby reducing the computational time and the round-off error encountered in purely numerical techniques. The influence of the throat Mach number, frequency, boundary-layer thickness and liner admittance on both upstream and downstream propagation of acoustic modes is considered. A numerical procedure, which is stable for cases of strong interaction, for analysis of nonlinear acoustic propagation through nearly sonic mean flows is also developed. This procedure is a combination of the Adams-PECE integration scheme and the singular value decomposition scheme. It does not develop the numerical instability associated with the Runge-Kutta and matrix inversion methods for nearly sonic duct flows. The numerical results show that an impedance condition can be satisfied at the duct exit and a corresponding solution obtained. The numerical results confirm that the nonlinearity intensifies the acoustic disturbance in the throat region, reduces the intensity of the fundamental frequency at the duct exit, and increases the reflections. This implies that the mode conversion properties of variable area ducts can reflect and focus the acoustic signal to the vicinity of the throat in high subsonic flows. Also the numerical results indicate that a shock develops if certain limits on the input parameters are exceeded. / Ph. D.

<p> Continuous development of Gas Turbines to realise higher work output has necessitated the design of turbine blades having large turning angles.</p> <p> Improvements to existing calculation methods have been carried out to better describe the potential flow near the leading and trailing edges of a blade originally designed by R. K. Malhotra at McMaster University. An incompressible turbulent boundary layer program has been extended to calculate compressible flows, taking into account the adverse and favourable pressure gradients, and it has been used to describe the flow in the region near to the blade surface. </p> <p> A test facility of the intermittent blow-down type was constructed and instrumented to test two-dimensional blade cascades. Some of the blades were instrumented to measure the surface pressure distribution. The performance of the blades has been analysed both theoretically and experimentally over a range of angles of attack and pressure ratios. The effect of stagger angle was also investigated to show its effect on performance. The experimental results were compared to those obtained theoretically, and the agreement substantiates the main thrust of the thesis, which was to develop a rational design technique.</p> / Thesis / Doctor of Philosophy (PhD)

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