Date of Thesis

7-26-2016

Thesis Type

Masters Thesis (Bucknell Access Only)

Degree Type

Master of Science in Mechanical Engineering

Department

Mechanical Engineering

First Advisor

Maria Laura Beninati

Second Advisor

Indranil Brahma

Abstract

This laboratory study was centered on the mechanical design and interaction of the two model marine hydrokinetic (MHK) turbines arranged in a stream-wise tandem configuration. The goal was to design and machine a model MHK turbine which performs in the same fashion as full scale device. In addition, experiments were performed to determine the effect of an upstream turbine on the performance of the downstream turbine. Specifically, the study focuses on the changes in nondimensional power generation that occurred as the stream-wise spacing between devices was varied. Understanding the interaction effect between laboratory scale marine hydrokinetic devices is an important step prior to field deployment. Currently only few studies have addressed the issues of non-dimensionalizing the performance of a turbine when the turbine is operating in a non-uniform flow. This study addresses the question: to what degree is there a practical basis for comparison of marine hydrokinetic turbine performance when a turbine operates in a non-uniform flow? In other words, what is the basis for relating the off-design behavior to on-design behavior due to non-uniform inflow? Testing was conducted in the hydraulic flume facility (9.8 m long, 1.2 m wide and 0.4 m deep) at Bucknell University. Two types of turbine model were used. A two-bladed turbine with a rotor diameter of 0.1 meters and a three-bladed turbine with a rotor diameter of 0.12 meters. Multiple tests were performed for a fixed range of separation distances between each set of the devices. For each separation distance, a mechanical power extracted from the flow was measured. In addition, velocity profiles incident on the downstream turbine were measured at each separation location and used in developing velocity scales to be used in non-dimensionalizing the performance of the downstream turbine. Results demonstrate that the performance of a downstream turbine is affected by the presence of the upstream turbine. The evolution of the wake was directly related to the performance of the downstream turbine and that the velocity scale used in nondimensionalizing the performance of the downstream turbine needs to be carefully developed. Results shows that an ideal separation distance could exists between devices such that the power generation and performance of the downstream turbine are maximized.

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