SNAME PAPER Night

Project Description:

While working on the design of the siphon turbine, we settled upon the idea of using variable pitch blades in the turbine.  Since a large consideration of the project is making a cost-effective setup to compete with already existing designs, we began our work with a controllable pitch boat propeller. 

The Initial Controllable Pitch Mechanism

Our first goal was to understand the mechanism of controlling the blades. This was the basic model for the new controllable pitch mechanism design.

The existing controllable pitch propeller relies on a concentric shafting system consisting of one solid shaft and one tubular shaft. The new design utilizes a motor in the hub which eliminates the need for a concentric shaft system.

As part of this design, a paper was submitted to the Student Paper Night put on by the Society of Naval Architect and Marine Engineers, outlining our proposed design. In early 2009, the team did research, design, and testing of this design, and a written report was submitted.

The report covers many aspects of this design, such as the hub layout, a method for transmitting a signal to the hub from the boat, and the feasibility of such a design. Using SolidWorks as a modeling tool, we were able to lay out a hub that contains all the necessary components for the system. Signal transmission required the team to build a test bed, develop an experiment, and collect data on a method to tranmit information to the hub. To see the submitted report for more details, click the "SNAME Report" link to the left.

Flow Modeling:

To accurately size and design a micro hydro turbine, some consideration of the water flow available must be made.  In many streams and rivers controlled by the small dams that will ultimately be the focus of this project, the flow of the water fluctuates significantly throughout the year.  The benefit of the variable pitch blade system is a wider range of high performance for this application.

For the river being considered, a ‘flow duration curve’ of the water was acquired.  This type of data shows the percent of time that water at least meets or exceeds a given flow rate.  This information, along with the average flow rate is critical in having a good turbine design; the range of performance of the turbine depends on the amount of water that will be flowing through it!  To aid in this, a calculator based off of a bin of data from the flow duration curve is being developed.  With the availability to specify the number of simulation values and randomly selected flow values, this program models the flow of the river over time. 

Furthermore, the MATLAB code being developed has adjustable high and low limits – flow that exceeds the physical capabilities of the turbine and siphon is not a realistic consideration, nor are periods of low flow that do not fall into the performance range.  The code being developed is already proving to be a useful design tool and is still being improved.