No description available.

Film cooling by means of holes is an essential cooling technique in modern gas turbine engines. This cooling technique is employed over endwalls, as well as on the surface of blades. Thus, there is a need for film cooling predictions in a three-dimensional setting. Currently only boundary layer codes are available for design purposes and they are difficult to apply to the three-dimensional case with secondary flows. Present advanced computation prediction methods are capable of solving the complete flow field in three dimensions with coolant flow. However, the spatial resolution that these methods require eliminate them as suitable options for design tools This study introduces a simpler description of the film cooling process which may be implemented in a code for design purposes. The parameters of turbulence enhancement, turbulence decay, and the coolant distribution at injection were optimized using existing experimental data. Finally, the code was employed in a three-dimensional setting with film cooling present. An experimental study of the flow through cooling holes was also undertaken. Two unique geometries were later developed where a row of cooling holes exited into a vortex region where the flow was mixed before being injected from a slot. The cooling benefits of these geometries is apparent.

Clearances between gas turbine casings and rotating blades is of quite importance on turbo machines since a significant loss of efficiency can occur if the clearances are not predicted accordingly. The radial thermal growths of the blade may be over or under predicted if poor assumptions are made on calculating the metal temperatures of the surfaces exposed to the fluid. The external surface of the blade is exposed to hot gas temperatures and it is internally cooled with air coming from the compressor. This cold air enters the radial channels at the root of the blade and then exists at the tip. To obtain close to realistic metal temperatures on the blade, the Conjugate Heat Transfer (CHT) approach would be utilized in this research. The radial thermal growth of the blade would be then compared to the initial guess. This work focuses on the interaction between the external boundary conditions obtained from the commercial Computational Fluid Dynamics software package CFX, the internal boundary conditions along the channels from a 1D flow solver proprietary to Siemens Energy, and the 3D metal temperatures and deformation of the blade predicted using the commercial Solid Mechanics software package ANSYS. An iterative technique to solve CHT problems is demonstrated and discussed. The results of this work help to highlight the importance of CHT in predicting metal temperatures and the implications it has in other aspect of the gas turbine design such as the tip clearances.

An accurate knowledge of turbine blade surface temperature is desired in order to obtain maximum performance from turbine engines. A limited spectrum radiation pyrometer can be used for blade temperature measurement. A model is presented which predicts the output signal from the detector unit of a pyrometer in a turbine engine application. Six inputs are required for the model. The inputs are the turbine blade geometry, location of the pyrometer with respect to the blades being viewed, focusing parameters of the pyrometer, type of detector, transmission curve of the optical system, and an estimate of the blade surface temperature. The model uses Fortran 77 and IBM CADAM to create a three dimensional representation of the pyrometer path across the blades along with the intercepted target spots. Once the target spot areas are determined, the photocurrent output signal of the detector is predicted as a function of percent blade chord and time. Results are shown for different detectors and temperature distributions. Experimental data is also included, and a comparison is made between the data and the model. Any of the model input parameters can be varied so that different pyrometer schemes can be evaluated at either the initial design phase or after installation. / Master of Science

A cross-flow turbine was tested to determine the magnitude of the fluid forces on the blades. The tangential and radial forces and the torque were measured on a test blade. Because the runner was made of plexiglas, the flow and the effects of the incidence angle at various speeds were observed. The pattern of blade loading over a revolution was measured over a range of heads from 1.0 to 2.6 m. The maximum forces were found to occur just before the blade leaves the nozzle exit. The experimental forces agree reasonably well with the results of a control volume analysis. Two figures are provided, by which the designer may determine the tangential and radial forces for any geometrically similar machine. / Master of Science

Past research at Virginia Tech (VPI) explored the aerodynamic loss of the transonic VPI turbine blade, which 1s based on the pitchline profile of a high pressure turbine blade for a large commercial aircraft gas turbine. The current experiment explores the loss of the VPI blade for different axial solidity ratios near the design point. Ten percent changes in the solidity ratio were accomplished by varying the blade pitch and changing the blade stagger to maintain a constant throat to spacing ratio. Reaction, exit angle and exit Mach number were kept constant with this method. Cascades with three different solidities were tested in VPI’s transonic blowdown wind tunnel. Downstream total pressure loss and static pressure measurements were obtained. In addition, inviscid calculations were made for each case. Static pressure contours and Mach number profiles from the calculations were compared with the experimental results. A ten percent decrease in solidity caused no cascade loss penalty as compared to the Baseline solidity for a wide range of Mach numbers. Calculated blade Mach number profiles agreed well with experimental profiles except on the suction side near the throat and downstream of the shock/boundary layer interaction. Predicted downstream static pressure values agreed well with experimental values, except that the inviscid code tended to over-predict the pressure rise across the suction side shocks. / Master of Science

The effect of blade profile variations on the erosion of turbine blades subjected to flow containing particulates was analytically determined. To accomplish this end, the two-dimensional inviscid main flow field was determined for each blade passage. A semi-empirical model of erosion was combined with available experimental data to predict erosion on the blade surfaces. Maximum erosion was found to be at the trailing edge of the stator and rotor and at the leading edge of the rotor. The trailing edge erosion of the stator and rotor was decreased as the blade exit angle was decreased. The trailing edge erosion of the stator and rotor was also decreased when the blade leading edge radius was reduced. Reducing the degree of reaction of the turbine stage caused a change in distribution of erosion levels along the blade surface. / Master of Science

A 2-D CFD / FEM model to simulate thermal stresses in a turbine blade has been set up using the software FLUENT and FIDAP. The model was validated against the data of Bohn et. al. (1995) and was used to simulate 5 test cases. The numerical model was set up for a single Mark II nozzle guide vane (NGV) and utilised the appropriate boundary conditions for the surrounding flow field. A commercially available software code, FLUENT, was used to resolve the flow field, and heat transfer to the blade. The resulting surface temperature profile was then plotted and used as the boundary conditions in FIDAP (a commercial FEM code) to resolve the temperature and stress profile in the blade. An additional solver within FLUENT essentially superimposes an additional flow field as a result of the NGV vibration in the flow field. The pressure, temperature and heat transfer coefficient distribution, from FLUENT, were compared to those from Bohn et. al. (1995). The model predicted the distributions trends correctly, with an average over-prediction for temperature, of 10 % on the suction side and 6 % on the pressure side. This was restricted to the region from leading edge to 40 % chord on both sides of the blade. The blade temperature and equivalent stress contour trends were also correctly predicted by FIDAP. The blade temperature was over-predicted by and average of 1.7 %, while the equivalent stress magnitude was under-predicted by a worst case of 43 %, but the locations of maximum stress were correctly predicted. The reason for the differences between the stresses predicted by FLUENT / FIDAP and the data given in Bohn et. al. (1995), is believed to be the results of the temperature dependence of the material properties for the blade (ASTM 310 stainless steel), used in the two studies, not being identical. The reasoning behind this argument is because the distribution trends and contour variation, predicted by the model, compared favourably with the data of Bohn et. aI., and only the equivalent stress magnitude differed significantly. This completed the validation of the FLUENT / FIDAP model. The model was used to simulate test cases where temperature (i.e. turbine inlet temperature or TIT), at the model inlet (Le. the pressure inlet boundary in FLUENT), was set up to be time varying. Four simplified cases, viz single shock, multiple shocks, simplified cycle and multiple cycles, and a complex cycle (a mission profile) were simulated. The mission profile represented typical gas turbine operational data. The simulation results showed that stress was proportional to TIT. Changes in TIT were seen at a later time in the stress curve, due to conduction through the blade. Steep TIT changes, such as the shock loads, affected stress later than gentler TIT changes - the simplified and multiple cycles. These trends were consistently seen in the complex cycle. The maximum equivalent stress was plotted against TIT to try and develop a loose law that gives maximum equivalent stress as a function of TIT. A 4th order polynomial was fitted through the maxima and minima of the maximum equivalent stress plot, which gave the maximum and minimum stress as a function of TIT. This function was used calculate the maximum and minimum and mean equivalent stress using the TIT data for the mission profile. Thus, the FLUENT I FIDAP model was successfully validated, used to simulated the test cases and a law relating the equivalent stress as a function of TIT was developed. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2002.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1982. / Microfiche copy available in Archives and Barker / Includes bibliographical references. / by Edward N. Marcus. / M.S.

An experimental and numerical investigation of the flow and convective heat transfer distribution around a high turning angle gas turbine rotor blade has been carried out at the University of Kwa-Zulu, Durban campus. This study in gas turbine blade aerothermodynamics was done to meet the research and development requirements of the CSIR and ARMSCOR. The experimental results were generated using an existing continuously running supersonic cascade facility which offers realistic engine conditions at low operating costs. These results were then used to develop and validate a 2-D model created using the commercially available Computational Fluid Dynamics (CFD) software package, FLUENT. An initial phase of the study entailed a restoration of what was an unoperational experimental facility to a state capable of producing test simulation conditions. In the analysis, a 4-blade cascade system with provisions for an interchangeable, test blade was subjected to the steady state conditions set up by the facility. Firstly, the flow was characterised by evaluating the static pressures around the midspan of a pressure measurement test blade. This was done using two pressure transducers, a scanivalve, an upgraded data acquisition system and LABview software. The method for measuring the heat transfer distributions made use of a transient measuring technique, whereby a pre-chilled Macor test blade, instrumented with thin film heat flux gauges was rapidly introduced into the hot cascade flow conditions by displacing an aluminum dummy blade while still maintaining the flow conditions. Measurement of the heat flux and generation of the isothermal heat transfer co-efficient distributions entailed re-instrumentation of the test blade section with gauges of increased temperature sensitivity along with modifications of the associated electrical circuitry to improve on the quality of experimental data. Both the experimental flow and heat transfer data were used to validate the CFD model developed in FLUENT. An investigation into different meshing strategies and turbulence models placed emphasis on the choice of model upon correlation. The outcome of which showed the k -co model's superiority in predicting the flow at transonic conditions. A feasibility study regarding a new means of implementing a film cooled turbine test blade at the supersonic cascade facility was also successfully investigated. The study comprised of experimental facility modifications as well as cascade and blade redesigns, all of which were to account for the requirements of film cooling. The implementation of this project, however, demanded the resources of both time and money of which neither commodity was available. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2006.