Project Leviathan: Modular Hydroelectric Generator

This project began as a part of a fascination with turbines spawned by the XM116 project, and thus can initially be considered an extension from it to further expand my understanding of fluid dynamics. The simplicity of this project was short lived, and it quickly evolved into a more functional concept that would retain an emphasis on rugged, simple design. After 2 early generations that were driven by theoretical concepts and free from functional limitations, the eventual mission statement for the project would be established as the following; ‘A compact, rugged, modular and self contained hydroelectric turbine generator’.

A significant piece of this project that would keep me invested over the many years that it persisted beyond a simple exercise in part and assembly design was the idea of Turbulence Induction Pattered Surfaces (TIPS). The concept of TIPS and it’s application was derived from a lesson I recieved from a fluid dynamics class that I’d taken at the turn of the decade wherein a demonstration compared the boundary layer behaviors of turbulent and laminar water flows over an object, as well as over a flat plane. At the same time, I was becoming aware of the relationships between certain fluid variables and how said variables affected the Reynolds Number (the Newtonian variable that determines whether a fluid is laminar or turbulent). I inferred that it should be possible to induce turbulence over the back face, also referred to as the drag face, of a turbine by increasing the surface area of said face. This would contribute to a higher Reynolds Number, thus inducing turbulence to tighten the boundary layer of the working fluid, in this case water, to decrease the stall zone of the turbine at a given fluid velocity. This would functionally allow the turbine to operate at a lower fluid velocity, therefore increasing the range of ideal operating conditions of the turbine.

To build further on this theory of TIPS, the entire inside of the outer wall was covered in this texture for a similar effect of reducting the boundary layer and increasing the operating range of the turbine. However, the functional consequence of this aspect was two-fold. Firstly, this served to increase the flow velocity at the radially outward-most portion of the blade, which would increase the torque applied to the blade at any given fluid velocity, and therefore increase output voltage. Secondly, it would increase the efficiency of a coaxially mounted second turbine by preserving the shortened boundary layer.

To further speak on this second turbine, it was created as a perfect mirror of the first turbine for a contra-rotating configuration and take advantage of the lateral deflection of fluid off of the first turbine.

Structural Design Philosophy

This project truly embodied a design philosophy at the time that I called ‘Right to Exist’. In short, Right to Exist dictates that all elements of a design must be defensible to scrutiny, as well as serve multiple functions wherever possible. For example, the Inlet and Outlet both serve the following functions:

• A structural element to keep the center screw aligned axially
• A structural element to defend a rigid form in the case of blunt force impacts
• A fluid guide to correct the incoming flow of water and optimally allow it to flow over the turbines
• A orientation correction mechanism for the entire generator to naturally orient to upstream of any flowing body of water
• A hydrofoil which will guide the generator immediately below the surface of the water, thus positioning the device at the point of hypothetically highest fluid velocity.

This design philosophy prompted dozens of iterations on all components. Other examples include the stator, which serves to both stiffen the axial core of the device to maintain alignment perfectly with the centerline of the generator, retain the generator stators positions around the turbines, and a fluid corrector between the first and second turbine to further improve the performance of the second turbine. The generator stator, also referred to as a squirrel-cage, both serves to derive electrical power from the rotation of the turbines, but also to provide a hard inner reinforcement for the outershell, and a spacer to stiffen the entire axial length of the device. Even the center screw chosen to run axially through the core of the entire device both serves its’ obvious function as a fastener, but also as an alignment tool by which an assembler or user can easily use as a guide to quickly assemble and service the generator.

As a result of this rigorous design verification process, the total part count of the device was reduced to 7 individual injection molded components, 6 of which are unique, and of these unique parts, 3 of which are compatible with the Leviathans’ sister project; the Leviathan Mini. The Leviathan mini, in short, is meant to use the same parts as the Leviathan, namely the same outlet, either turbine, and outer shell, with the only unique component being an inlet.