An experiment was conducted to investigate the aerodynamic losses of two high-pressure steam turbine nozzles (526A, 525B) subjected to a large range of incident angle and exit Mach number. The blades were tested in a 2D transonic windtunnel. The exit Mach number ranged from 0.60 to 1.15 and the incidence was varied from -34o to 35o. Measurements included downstream Pitot probe traverses, upstream total pressure, and endwall static pressures. Flow visualization techniques such as shadowgraph photography and color oil flow visualization were performed to complement the measured data. When the exit Mach number for both nozzles increased from 0.9 to 1.1, the total pressure loss coefficient increased by a factor of 7 as compared to the total pressure losses observed at subsonic condition (M2<0.9). For the range of incidence tested, the effect of flow incidence on the total pressure losses is less pronounced. Based on shadowgraphs taken during the experiment, it's believed that the large increase in losses at transonic conditions is due to strong shock/boundary layer interaction that may lead to flow separation on the blade suction surface. From the measured total pressure coefficients, a modified loss model that accounts for higher losses at transonic conditions was developed. The new model matches the data much better than the existing Kacker-Okapuu model for transonic exit conditions. / Master of Science

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Predicting the performance of wind turbines is a key part of the turbine design process and operation, as predictive models play a large role in determining potential power output and efficiency at different operating conditions to help maximize production. On small-scale wind turbines performance models become more complex, as the rotor aerodynamic performance depends not only on the tip speed ratio, but also on the flow Reynolds number. An accurate predictive model that includes this behavior on small-scale wind turbines can be used to find the optimal operating conditions for power output, and is also a critical component of the design of a control system. This project aims to develop such a model for the small-scale wind turbine operated by the Cal Poly Wind Power Research Center, and to use the developed model to redesign the current control system. The full turbine system model developed in this project for the Cal Poly Wind Turbine includes detailed models of the aerodynamic, mechanical, and electrical subsystems on the turbine based on first- principles physics. Model parameters were determined through a combination of experimental testing and theoretical analysis. The full turbine model was compared against experimental data, showing that estimations from the predictive model matched closely with the true performance of the turbine. Through the model, the turbine was estimated to have a maximum efficiency of 83.63% and to produce a maximum total ���� of 35.93% at a tip speed ratio around 5. Using the performance information from the model, a new non-linear controller was designed for constant speed, constant tip speed ratio, and maximum power output. The new maximum power controller is predicted to increase the overall power production of the turbine by 17.1% over the course of a year.

Cal Poly, San Luis Obispo’s first wind turbine explores the methods and processes that are employed to manufacture utility scale wind turbines, and applies them to small scale wind turbines. The primary objective is to promote the development of small scale wind turbine blades in ways that resemble, as closely as possible, the construction and methods of utility scale turbine blade manufacturing. Vacuum infusion is employed to create a hollow, multi piece, lightweight design using carbon fiber and fiberglass with an epoxy based resin. A “rapid prototyping” method is developed using high density foam molds that allows short cycle time between design iterations of aerodynamic planforms. A production run of eight blades is manufactured and key components of the blade are tested to determine the appropriateness of the design.

This project accomplished two correlated goals of designing a new rotor blade to be used with the Cal Poly Wind Power Research Center, as well as defining the methodology required for the aerodynamic analysis of an optimized blade, the procedure required for generation of an accurate CAD model for the new blade geometry, and structural integrity verification procedure for the new blade via finite element analysis under several operating scenarios. The new rotor blades were designed to perform at peak efficiency at a much lower wind speed than the current CPWPRC rotor blades and incorporated a FEA verification process which was not performed on the earlier rotor blade design. Since the wind characteristics relative to the location of the CPWPRC are essentially unchanging the most viable option, in regards to generating power for longer periods of time, is to redesign the HAWT rotor to capture more of the wind energy available. To achieve this, the swept area of the rotor was increased, suitable airfoils were utilized, and the new rotor blades were optimized to maximize their performance under the CPWPRC location’s wind conditions. With an increased magnitude of wind energy being captured the aerodynamic loading on the rotor blades simultaneously increased which necessitated a structural analysis step to be implemented, both with classical hand calculations and with the assistance of an adequate FEA program, to ensure the new rotor blades did not fail under normal or extreme wind conditions. With the completion of this project the new rotor blade designed and analyzed in this report may be finalized and refined in order to be incorporated into the CPWPRC system in the future or the methodology defined throughout this project may be used to design an entirely different aerodynamically optimized rotor blade, including a CAD model and FEA structural integrity verification, as well.

A streamline curvature (SLC) throughflow numerical model was assessed and modified to better approximate the flow fields of highly transonic fans typical of military fighter applications. Specifically, improvements in total pressure loss modeling were implemented to ensure accurate and reliable off-design performance prediction. The assessment was made relative to the modeling of key transonic flow field phenomena, and provided the basis for improvements, central to which was the incorporation of a physics-based shock loss model. The new model accounts for shock geometry changes, with shock loss estimated as a function of inlet relative Mach number, blade section loading (flow turning), solidity, leading edge radius, and suction surface profile. Other improvements included incorporation of loading effects on the tip secondary loss model, use of radial blockage factors to model tip leakage effects, and an improved estimate of the blade section incidence at which minimum loss occurs. Data from a single-stage, isolated rotor and a two-stage, advanced-design (low aspect ratio, high solidity) fan provided the basis for experimental comparisons. The two-stage fan was the primary vehicle used to verify the present work. Results from a three-dimensional, steady, Reynolds-averaged Navier-Stokes model of the first rotor of the two-stage fan were also used to compare with predicted performance from the improved SLC representation. In general, the effects of important flow phenomena relative to off-design performance of the fan were adequately captured. These effects included shock loss, secondary flow, and spanwise mixing. Most notably, the importance of properly accounting for shock geometry and loss changes with operating conditions was clearly demonstrated. The majority of the increased total pressure loss with loading across the important first-stage tip region was shown to be the result of increased shock loss, even at part-speed. Overall and spanwise comparisons demonstrated that the improved model gives reasonable performance trends and generally accurate results, indicating that the physical understanding of the blade effects and the flow physics that underlie the loss model improvements are correct and realistic. The new model is unique in its treatment of shock losses, and is considered a significant improvement for fundamentally based, accurate throughflow numerical approximations. The specific SLC model used here is employed in a novel numerical approach — the Turbine Engine Analysis Compressor Code (TEACC). With implementation of the improved SLC model and additional recommendations presented within this report, the TEACC method offers increased potential for accurate analysis of complex, engine-inlet integration issues, such as time-variant inlet distortion. / Ph. D.

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