Date of Award

5-2014

Level of Access

Campus-Only Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical Engineering

Advisor

Michael L. Peterson

Second Committee Member

Richard W. Kimball

Third Committee Member

Krish P. Thiagarajan

Abstract

In this work, a dynamic stall model is used with lifting-line vortex method models in order to predict the hydrodynamic performance of high solidity cross- flow turbines. The dynamic stall model presented in this work is based on the Beddoes Leishman (B-L) dynamic stall model and blade force solutions which are derived using conformal mapping for one blade. The dynamic stall formulae used in the model to calculate blade forces has been modified to consider the asymptotic values. The model can therefore represent the principal phenomena to which cross-flow turbines are subject at a large range of operating conditions. The dynamic stall model has also been modified to provide predictions for a large range of angles of attack and Reynolds numbers, conditions under which crossflow turbines operate. The model uses Sheng’s consideration of the influence of reduced-pitch rate on the angle at which the blade stalls. The dynamic stall model includes considerations for flow curvature effects. Parameters, such as blade thickness and camber, are considered in the derived formulae, which allow predictions of numerous turbine configurations and therefore make the model suitable for implementation on turbine optimization codes. This characteristic allows the method to better predict the performance of cross-flow turbines with high solidity ratios. The cross-flow turbine model was assessed with experimental data that was acquired using different blade profiles, range of toe angles and multiple solidity ratios.

This work also presents experimental data that was obtained for the hydrodynamic performance of a cross flow turbine using NACA 0018 and NACA 63018 blade families. This experimental data-set consist of measurements of the torque and power coefficient, taken at different toe angles and tip-speed ratios. The data set demonstrates the influence that the variation of the blade camber, the number of blades, and the chord-to-radius ratio has on the turbine performance. This experimental data-set is intended to complement previous data-sets for use in validation of design models and to support turbine design. Cases of negative power output and unoptimized design were also included in the experimental data set to increase the number of cases available for validating design models.

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