After more indepth calculation, we arrived at the following:
Impeller Diameter- 40 inches
HP requirement- ~900 (approximation on the high-end)
Est. Flow (GPM)- 142,000
Head (Ft.)- ~24
At first, these numbers seemed unrealistic. Calculations were re-evaluated multiple times and were consistant.
Using the estimations, we scaled the entire unit down to fit our small scale test boat (a 14' aluminum boat, powered by an 8 HP, 36 VDC golf cart motor turning 1600 RPM), and designed the propeller, housing, nose cone and tail cone using Autodesk Inventor 2010. From Inventor, we printed FDM (Fused Deposition Modeling) parts on our Dimension 3D printer.
Using the calculations from before, we figured the scaled unit would absorb about 3.5 HP and should pump about 1320 GPM. This would fill a 55-gal. drum in about 2.5 seconds. This seemed too good to be true.
For testing, we decided to connect a 6" PVC pipe to the pump, and try to measure the flow by filling up a drum. This unit pumped so much water, that I could not hold the barrel upright in the stream. I was very impressed.
We then connected a 55 gallon barrel to the end of the pipe. Using a stop watch, we were able to get a good idea of how long it takes to fill the drum, and allow us to figure how much flow we were actually producing. We ran several test, and all were consistent with an average time of 2.7 seconds. This matches very closely with our preliminary calculation of 2.5 seconds.
All in all, this was a very encouraging test. It seems our figures are right on so far. We were very close to our calculations on flow, HP absorption, and head. Now, we plan to scale this up for some bigger testing at 190 HP, before building the full scale version.
In all the excitement, I didn't snap a still shot of the barrel test. But I did get it on video. I will have to convert it to get it under 10MB (Host Limit), then I will post it for upload.
~R.J. Penn
