Fundamental Form-s

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LOW HEAD INVOLUTE WATER TURBINE DESIGNS & PLANS

Canal Turbine full scene2
Canal Turbine with reinforcing-1

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.

This page is introductory.  To view the final detailed drawings, CLICK HERE.
 

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.

Involute 360 math

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 840 degree dimensions_not-to-scale_600W

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.

involute_270 degree 5-fold_600pixW
water turbine scale model-1

Click here to view mpg movie of testing this model in the wind.

Water Turbine-3vane in wind2

A 3-bladed linear extrusion of an involute segment spins very fast in the wind, and also has high speed and torque as an overshot water wheel.

Canal Turbine Test compare-1

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.

water turbine scale model-1 in test bed1
twin turbines with tanks H
Water Turbine test-3vane in channel showing gate

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.

Water turbine_5vane involute in straight flume

Neither of these configurations are efficient designs.

Water turbine_5vane involute in flume

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!

Water turbine_5vane involute immersed in straight flume

The test rig was then modified to be an overshot turbine, with various turbine mounting options, variable flow directing spill-plates, and a variable water gate (green plate top center - set here to 1/4”) to level-out flow of water entering from two hoses at around 12 gpm flow rate.

Water Turbine test-3vane in channel

Click here for a video of testing both turbine configurations in overshot testbed.

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)

 

The above configuration is diagramed below as a 6-vaned 200degree involute 3ft diameter turbine with narrow inlet channel.

Gover overshot4
Gover overshot-3.5ft02

After numerous tests, the above was determined to be the most efficient design for a low-head overshot water turbine.  For our test site of 30cu.ft./sec water flow, optimized turbine deployment would be three 42” diameter x 8ft long turbines in parallel, separated by 2ft in stream.  This would allow a maximum of 29cu.ft. of water to collect in the vanes as it travels down and through the turbine, or 1,800 pounds of water per revolution assisting in the power generation.

Unfortunately, the chosen site for demonstrating this turbine did not have enough water drop (head) to accommodate this design.

Water Turbine test-3vane through center1

I also performed several tests with the water flowing through a center hole the size of the involute circle.  This would be an excellent design for a turbine mounted on the end of a pipe, allowing maximum power capture from the enclosed water pressure.  See diagram below:

A vertically oriented turbine produced considerably less torque than a horizontally oriented one, because of the gravity-propelled water loading the vanes.

 

Flow results for three 240 degree vanes
both hoses filling horizontal 1/7 of turbine volume at 1.57 cu.ft./min = 150rpm

Click here for a video showing testing of this turbine configuration.

Water pipe horizontal canal turbine1

Because practical water drop at the chosen site is less than 5 feet elevation, with top of incoming water to bottom of exiting water maximum 7 feet, a vertical axis design was chosen, with six 200 degree involute vanes in an 8ft diameter x 4ft tall configuration as pictured below.  Water flows from above, upper right duct (which is covered to compress water into the narrow channel)  Outlet below is wider to accommodate slower flow (due to energy extracted from water) in shallower stream.

Water turbine_6vane vertical in cement ductwork-man

To download a detailed dimension PDF drawing of this design, click here.

Canal Turbine 3ft-dia 5-vane horizontal overshot 200degree

The 3ft diameter horizontal axis turbine drawing above is designed to fit within the elevation drop parameters of the site.

STUDY THE OVERALL DIMENSIONS TO DETERMINE IF THIS IS INDEED POSSIBLE!  The canal will flow through a constriction, SLOPING FROM BELOW, to accelerate the water to around 100ft/sec at minimum depth of 14”.

5/20/09 ~ a high-volume flow test was conducted pouring from a 5gal bucket to augment the faucet flow.

Total flow through a 1” deep gate valve was 52.7gal/min

ratio of 4' wide x 3'dia turbine to 6" wide x 6"dia turbine = 8 times as wide and 48 times the volume
1" deep equivalent to 8" deep on 4' wide turbine
48 x 52.7 equivalent to 2530 gal/min = 338 cu.ft./min = 5.6cu.ft./sec = 2/5th the flow
using only 48" x 6" ratio, = 451 cu.ft./min = 7.5cu.ft./sec = 1/2 the flow
speed at max flow = 200rpm, which figures to 400rpm when flow speed is doubled.
 

This test indicates that the 3’ x 4’ turbine will handle the required flow of 15cu.ft./sec if speed is doubled in the constrictor.

 

CLICK HERE TO SEE VIDEO OF HIGH-VOLUME FLOW TEST

 

CLICK HERE TO SEE COMPARISON WITH COMMON FRANCIS TURBINE

Canal Turbine 19inch cowling duct

3’ diameter x 4ft long 5-vanes; 200 degree involute spirals.  Water enters tangentially to vanes.

Canal Turbine-front with person2

One of two 3’ x 4’ turbines, showing support framework and size comparison with 5’9” person

to download a PDF file of a dimensioned drawing, CLICK HERE

Water Skeeter1 with man
Water Skeeter mechanism-CLOSE

The above concept drawing shows a test prototype of a drag-propulsion sail boat propelled by an involute spiral wind turbine, which should revolutionize sailboat design by creating very smooth and high efficiency transfer of wind energy to pushing the water between the split hull of the boat.  When the boat is anchored in a current, it can be generating electricity.  The same mechanism can be used to extract power from any shallow moving water when anchored in-stream.  The multiple paddles are pulled through the water along tracks by cables which direct them around pulleys and up out of the water as they return to the front.

Water Skeeter mechanism-perspective above

For more details on this boat design, CLICK HERE