This thesis presents a multi-grid scheme applied to the solution of transport equations in turbulent flow associated with heat transfer. The multi-grid scheme is then applied to flow which occurs in the film cooling of turbine blades. The governing equations are discretized on a staggered grid with the hybrid differencing scheme. The momentum and continuity equations are solved by a nonlinear full multi-grid scheme with the SIMPLE algorithm as a relaxation smoother. The turbulence k — Є equations and the thermal energy equation are solved on each grid without multi-grid correction. Observation shows that the multi-grid scheme has a faster convergence rate in solving the Navier-Stokes equations and that the rate is not sensitive to the number of mesh points or the Reynolds number. A significant acceleration of convergence is also produced for the k — Є and the thermal energy equations, even though the multi-grid correction is not applied to these equations. The multi-grid method provides a stable and efficient means for local mesh refinement with only little additional computational and.memory costs. Driven cavity flows at high Reynolds numbers are computed on a number of fine meshes for both the multi-grid scheme and the local mesh-refinement scheme. Two-dimensional film cooling flow is studied using multi-grid processing and significant improvements in the results are obtained. The non-uniformity of the flow at the slot exit and its influence on the film cooling are investigated with the fine grid resolution. A near-wall turbulence model is used. Film cooling results are presented for slot injection with different mass flow ratios. / Science, Faculty of / Mathematics, Department of / Graduate

Externally applied loads from high winds or impacts may cause structural damage to the wind-turbine blade, and this may further affect the aerodynamic performance of the blade. Wind-turbine blades experience high vibration levels or amplitudes under high winds. Vibrations negatively affect the wind flow on the blade. This project considers the structural dynamic analysis of a small-scale wind turbine with a particular focus on the blade; it involves the finite element model development, model validation and structural analysis of the validated model. The analysis involves a small-scale wind-turbine structural response when subjected to different loading inputs. The analysis is specifically focused on on-shore systems. The use of small-scale wind-turbine systems is common however, apart from initial structural analysis during design stages, these systems have not been studied sufficiently to establish their behaviour under a variation of real-life loading conditions. On-shore wind turbines are often designed for low-wind speeds and their structural strength may be compromised. In addition, these systems experience widely-varying wind speeds from one location to another to an extent that it is extremely difficult to achieve a uniform structural performance. The main reason for solving this problem is to evaluate the structural response of the blade, with special emphasis on an 800 W Kestrel e230i. This involves the calculation of the distribution of blade deflections and stresses over the wind-turbine blade under different loading conditions. To solve the problem, a three-dimensional model of a Kestrel e230i blade was firstly developed in Autodesk Inventor Professional using geometrical measurements that were taken in the mechanical engineering laboratory. A 3D finite element model was developed in ANSYS using approximate material properties for fiberglass obtained from the literature. The model was then validated by comparing its responses with those from a number of static tests, plus a simple impact test for comparison of the first natural frequency. Finally, a number of numerical tests were conducted on the validated finite element model to determine its structural responses. The purpose of the numerical analysis was to obtain the equivalent von Mises stress and deformation produced in the blade. It was determined that under the examined different loading conditions, a higher stress contour was found to occur around the mid-span of the blade. The calculated maximum flexural stress on the blade was observed to be less than the allowable flexural stress for fiberglass which is 1,770 MPa. As expected, the highest deformation occurred at blade tip. The first critical speed of the assembled three-bladed wind turbine was found to be at 4.3 rpm. The first mode shape was observed to be in the flap-wise bending direction and for a range of rotor speeds between zero and 608 rpm, three out of a total of five mode shapes were in the flap-wise bending direction. Future studies should address issues relating blade vibrations with generated power, validation of dynamic tests, fluid-structural interaction and introduction of bio-inspired blade system. Although the performance of the bioinspired blade has not been studied in great detail, preliminary studies indicate that this system has a superior performance. / Mechanical and Industrial Engineering / M. Tech. (Electrical and Mining Engineering)

A comprehensive study of the flowfield through a two-dimensional cascade of the high pressure turbine blades of a jet engine is presented. The main interest is the measurement and prediction of the mass-averaged total pressure losses. Other experiments, such as flow visualization, are aimed at the validation of the code that was used to obtain the numerical results and also to further knowledge about the details of the loss generation. The experimental studies were carried out on a cascade of eleven blades in a blow-down tunnel. Total pressure measurements were taken upstream of the cascade and also by traversing on downstream planes. The static pressures needed for the mass averaging and the probe bow shock correction were obtained by pressure taps on the cascade tunnel side wall. The static pressure was also measured on the surface of some instrumented blades. Shadowgraph pictures were taken for study of the trailing edge shock structure and for the turbulent transition location. A single-plate interferometer technique was used for density field measurements. The major goal of the numerical studies was the prediction of the mass-averaged total pressure losses, but all other measured quantities were also generated from the computed flowfield. A critical issue was the generation of a proper grid. For the studied type of flow, a non-periodic C-type grid turned out to be the most advantageous. For use in the moderately compressible attached turbulent boundary layer, a Clauser-type eddy viscosity model was developed and tested. In the trailing edge and wake region, the Baldwin-Lomax model was used. Good agreement of calculations and measurements was obtained for the blade surface and cascade tunnel side wall static pressures, the trailing edge shock structure, and the density field. The agreement between the measured and calculated total pressure drop profiles was not quite as good; however, that quantity is known to be difficult to predict accurately. The mass-averaged total pressure loss coefficient, calculated from the total pressure drop profiles, was again in good agreement with the measurements. The difference between the measured and computed total pressure drop profiles suggested that the Baldwin-Lomax model underpredicted the eddy viscosity in the trailing edge region. / Ph. D.

The finite element method is applied to an isolated and twisted wind turbine blade which is rotating in a vertical plane to determine its structural dynamic characteristics. The equations of motion are formulated for a rotating beam with flap and lead-lag degrees of freedom subjected to nonsymmetric bending. Using a variational approach, a blade finite clement is developed from these equations of motion. Additionally, expressions are formulated for the elastic strain energy and kinetic energy of a rotating wind turbine blade. Lagrange's equation is applied to these energy expressions and an isoparametric finite element based on three dimensional elasticity and quadratic interpolation functions is developed. Both sets of finite element equations are implemented in a general purpose computer program to solve the structural dynamics eigenvalue problem and results compare favorably with published data for the cases of a nontwisted cantilevered beam both at rest and while rotating. A blade finite element model of a 10KW horizontal axis wind turbine blade is presented and its lowest modes of vibration are calculated for the cases of the blade at rest and in operation at rotor speeds up to 250 RPM. / M.S.

A facility for the investigation of stall flutter in aircraft engine compressors and fans was designed. Stall flutter was achieved in the test fan and verified through sonic and photographic methods. The frequency components of the sonic output during flutter were determined using a real-time analyzer. This frequency analysis indicated a dominant peak within 7 percent of the theoretical torsional natural frequency of the blades. Photographs taken during stall flutter indicated the presence of an interblade phase angle. The effect of blade stagger angle, flow incidence angle and solidity on flutter speed was determined. / Master of Science

Gas turbine blade tip heat transfer and tip gap flow phenomena has been explored experimentally in a stationary cascade for blade exit Mach numbers = 1.2 to 1.4. Experimental results were found to agree well with qualitative predictions performed at GE Aircraft Engines. The pressure distribution in the blade tip cavity of a grooved tip blade was found to vary little with either Mach number or tip gap height. The tip cavity pressure was, however, a strong function of location. The tip cavity pressure distribution coupled with the pressure side distribution near the tip was speculated to drive the leakage flow across the blade tip from mid-chord aft based on surface flow visualization studies using an oil/dye mixture. Heat flux on the tip cavity floor was successfully measured using a thin-film Heat Flux Microsensor. Results of these measurements are consistent with previous studies in the subsonic regime. The convection coefficients on the tip cavity floor were found to be three times those found on the suction side airfoil surface near the trailing edge. Convection coefficients were found not to vary with either tip gap height or Mach number. The fluctuating component of heat flux was found to be at least 25% of the total heat flux. / Master of Science

The aerodynamic and thermodynamic performance of an aircraft gas turbine directly affects the fuel consumption of the engine and the life of the turbine components. Hence, it is important to be able to understand and predict the fluid flow and heat transfer in turbine blades to enable the modifications and improvements in the design process. The use of numerical experiments for the above purposes is becoming increasingly common. The present thesis is involved with the development of a flow solver for turbine flow and heat transfer computations. A 3-D Navier-Stokes code, the Moore Elliptic Flow Program (MEFP) is used to calculate steady flow and heat transfer in turbine rotor cascades. Successful calculations were performed on two different rotor profiles using a one-equation q-L transitional turbulence model. A series of programs was developed for the post-processing of the output from the flow solver. The calculations revealed details of the flow including boundary layer development, trailing edge shocks, flow transition and stagnation and peak heat transfer rates. The calculated pressure distributions, losses, transition ranges, boundary layer parameters and peak heat transfer rates to the blade are compared with the available experimental data. The comparisons indicate that the q-L transitional turbulence model is successful in predicting flows in transonic turbine blade rows. The results also indicate that the calculated loss levels are independent of the gridding used while the heat transfer rate predictions improve with finer grids. / Master of Science

The behavior of 8-harness satin woven Celion 3000/PMR-15 graphite-polyimide was experimentally investigated. Unnotched and center-notched specimens from (0)₁₅, (0)₂₂, and (0,45,0, - 45,0,0, - 45,0,45,0)₂ laminates were tested. Material properties were measured and damage development documented under monotonic tension, sustained incremental tension, and tension-tension fatigue loading. Damage evaluation techniques included stiffness monitoring, penetrant-enhanced X-ray radiography, laminate deply, and residual strength measurement. Material properties of the woven graphite-polyimide were comparable to those of woven graphite-epoxy. Damage development in woven graphite-polyimide was quite different than in non-woven graphite-epoxy. Matrix cracking was denser and delamination less extensive in the graphite-polyimide material system, and as a result, increases in notched residual tensile strength were much lower. A ply level failure theory was used to successfully predict the notched tensile strength of the (0,45,0, - 45,0,0, - 45,0,45,0)₂ laminate based on experimental data from the (0)₂₂ laminate. A simple method was used to simulate fatigue damage in a (0)₂₂ notched specimen to predict residual strength as a function of fatigue life. The advantages and disadvantages of the ply level failure theory used in this study are discussed. / Master of Science

This thesis describes the design and initial testing of a transonic turbine cascade facility. It is specifically concerned with the best way to obtain flow periodicity and repeatability through the cascade by the use of tailboards at the cascade exit. The problem of how to achieve flow periodicity and repeatability has not been completely resolved. An examination of the literature available on transonic turbine cascade testing indicates some researchers use no tailboards, some use a solid tailboard, and still others use a porous tailboard. In this thesis, the flow through the turbine cascade is tested for three different cascade exit configurations; no tailboard, a solid tailboard, and a porous tailboard. The cascade is also tested with the tailboard at different angles, to see what effect the angle of the tailboard has on the flow through the cascade. The data acquisition and flow visualization systems are discussed and some preliminary results are given. / Master of Science

The success of harnessing energy from ocean current will require a reliable structural design of turbine blade that is used for energy extraction. In this study we are particularly focusing on the fatigue life of a 3m length ocean current turbine blade. The blade consists of sandwich construction having polymeric foam as core, and carbon/epoxy as face sheet. Repetitive loads (Fatigue) on the blade have been formulated from the randomness of the ocean current associated with turbulence and also from velocity shear. These varying forces will cause a cyclic variation of bending and shear stresses subjecting to the blade to fatigue. Rainflow Counting algorithm has been used to count the number of cycles within a specific mean and amplitude that will act on the blade from random loading data. Finite Element code ANSYS has been used to develop an S-N diagram with a frequency of 1 Hz and loading ratio 0.1 Number of specific load cycles from Rainflow Counting in conjunction with S-N diagram from ANSYS has been utilized to calculate fatigue damage up to 30 years by Palmgren-Miner's linear hypothesis. / by Mohammad Wasim Akram. / Thesis (M.S.C.S.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.