The water turbine designs pictured here are new approaches to low-head water power generation. Thanks to the instigation of Rod Johnson and preliminary funding from Rich Gover, I designed, built and tested several concept prototypes and learned much about the involute spiral geometry and its potential for harvesting energy. Hopefully, these efforts will receive further funding and development in the near future ~ the world needs new sources of non-polluting power now.
All of these designs are built upon the involute spiral, which is essentially the unwinding of a circle. Imagine a blue string wound counterclockwise on a spool of radius one. As it unwinds, the end of the string traces out an involute path.
The distance from the end of the involute curve of a full circle of radius-1 to its origin is 2pi = 6.28…, the circumference of the circle. The successive unwinding can continue indefinitely, with the distance between successive spiral lines equal to the circumference of the inner circle being unwound.
Involute segments can also be duplicated in a circular pattern, creating pathways between spirals that are non-constricting.
This and the unique curvature geometry of the involute spiral allow ducts in turbines to capture the force of moving fluids with all the resistance imparted to rotation, not turbulence.
| The first set of turbine tests models were designed around these two involute shapes. They were constructed of 6” wide vanes glued in between two plexiglass disks, with steel rod and teflon bearings. |
The first test was as an undershot water wheel. Water was pumped into the top rear of this test bed, flowing under the green gate below and through the lower involute blades. Much to my surprise, there was significant drag and not much power. On analysis, the non-compressive nature of water under the upstream vane created an effective damper to the strong rotation imparted at the mid-stream vane position. This is a very important consideration in designing water turbines vs. air turbines, and applies equally to modified airfoil blade shapes. Turbulent cavitation and drag are created with increased speed, such that the turbine dramatically looses efficiency and can be quickly destroyed by the cavitation.
Even more resistance is created, for the same reasons, when the turbine blades are fully immersed in the water, both horizontal and vertical.
Q: Will this combination of water turbine below with air turbine above work?
A: The air turbine will work great, but the water turbine will be a dud!
Contrast this to how fast the small prototype spins in compressible air. It will even spin in the wake of a shopvac 12 feet away!
This design has the unique property of providing higher torque as more power is being taken from the turbine, due to the greater amount and weight of captured water that is being pulled down by gravity and contributing to the spin of the turbine.
Here are preliminary (not scientifically rigorous) results from the above tests:
•3 vanes 240degree, 1/4″ gate = 139 rpm………circumference speed = 218ft/min = 136% of entering water speed
•6 vanes 140degree, 1/4″ gate = 149rpm……….circumference speed = 234ft/min = 145% speed of entering water
•6 vanes 140degree, 3/16″ gate = 147rpm……..circumference speed = 231ft/min = 143% speed of entering water (smoother but slower)
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Read the full article here: https://web.archive.org/web/20190131044924/https://www.fundamentalform.com/html/low_head.html