DIY axial flow pump, fractional hp motor, highest level of water through 6 inch diameter 30 ft pipe

Discussion in 'Hydrodynamics and Aerodynamics' started by Luke Frisbee, May 5, 2021.

  1. Luke Frisbee
    Joined: May 2021
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    Luke Frisbee Junior Member

    Please, I understand, I am in the wrong place...
    but there does not exist a "right place" for a mad man.
    First real quick, I am reinventing the wheel. But this "wheel" is a very high DIY sort of axial flow pump using a small outboard or trolling motor prop and a fractional horsepower motor to produce the highest level of water through a 6 inch diameter, 30 ft long pipe with two 90 degree bends.
    So if that isn't something you want to cogitate along with me then forgive me for having you read this far, and I am sorry I wasted your time.
    Now, however, I have read about 30 minutes of some of the more "scientific" threads and answers here, and you guys got the book sense and me...well I got some purely ungrounded or proven thoughts.
    My main issue is centrifugal pumps were easy to engineer, simple to work on or build, somewhat reliable..but most of all they make money for the manufacturer. But damn they waste energy sloshing water around and building unused pressures considering what they could be doing....
    I've read on here about slippage and efficiencies and water cylinders not being all the water that is "moved" or displaced" or disturbed or whatever other words you guys use to explain all the various hydro-gyrations that happen when a prop spins in water. But it makes my head spin about as bad as the water must be. But I believe each of you. And I think I can get a lot further down the road...
    Wait this is going on forever.
    {Regathers self}
    I want to put a prop at the end of a pipe and pull water through that pipe at the highest VOLUME possible, head/pressure be damned. You see I play with koi. and big water is best for koi. yet turning the water over ( volume/hour) is most important.
    Now the hobbyist have found some centrifugal pumps that do a better job than swimming pool pumps but still a huge amount of energy is wasted in using the various designs.
    The most efficient system to me would be to have a prop right in front of the end/opening and have as few encumbrances in the way as possible to keep pressure as low as possible, and also eliminate/reduce water from recirculating through the prop by getting it very close to the pipe opening..whether slightly in it or not?
    What I am going to tinker with are some thruster props, trolling motor and small outboard props. And marrying them to some fractional horsepower submersible water pumps.
    right now I have created an airlift system that is capable of creating about .6-.9 inches of head from one end of the pipe from the other...but the restriction that is causing the head is not the 6 inch pipe, and I can eliminate that restriction as I get more volume from ..,
    Well the propeller pump...If I keep the pressure so extremely low what will the flow become (Rhetorical question)?
    With my uneducated eye I see water coming off the ends of the propeller blades..it just seems like with little pressure vast amounts of water should start moving through the whole pond (system) as it gains moment.
    I wonder if anyone is still reading...this has bothered me for years.
     
  2. Luke Frisbee
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    Luke Frisbee Junior Member

    oh, and if We can develop such a water mover it will improve the planet just a little bit by getting the understanding out into the hobby so people will quit wasting energy.
     
  3. Luke Frisbee
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    Luke Frisbee Junior Member

    and the only reason I got here is because I was trying to find how much water trolling motors actually moved...the search sent me to the thread about how much water does a propeller move. the example/problem involved a 600ft ship. But the discussion started sounding like aspects I was thinking about.
     
  4. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    I'm not sure I'm fully understanding everything you said.
    But I'll make two suggestions.
    One, reduce the friction in the pipe by making the turns as large as possible.
    Two, use a prop from a jet ski rather than from an outboard.
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    What is the efficiency difference between a centrifugal pump, and an axial one, in such an application ? It might make sense to worry about it with high power requirements, but with small scale equipment, is it worth bothering ? I recall the story of the MiG-15 aircraft, which used a centrifugal air compressor, theoretically inferior to axial compressors, but still worked well enough. It would only be worth bothering if the electricity consumption difference added up to something significant.
     
  6. Barry
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    Barry Senior Member

    Pump Types Guide - Find the right pump for the job http://www.pumpscout.com/articles-scout-guide/pump-types-guide-aid100.html
    Within this table that provides an overview of the advantages of different pumps.
    You have not specified how many gallons of water per minute/hour that you are looking for
    The quality of the water is important. Ie if there is junk in the water, the displacement pumps are probably not the way to go
    Axial pumps, utilized in low head-high volume is where I would research.
    Centrifugal pumps are normally associated with high pressure and I doubt that you are requiring this and if the pump develops un needed pressure, you are not going to be power efficient

    How to figure out which is the best

    Pick the volume that you are looking for, determine if there is a height differential (head) that the inlet and the outlet, then pick any major pump manufacturer and just look at their specs
    Playing around with a thrust propeller designed with different parameters will more than likely be a waste of time.

    I would expect for under $100 -$150 you will find a high volume pump that will erode the gills of your fish at pennies per hour

    It is unlikely that your DIY proto type will "beat" the efficiency of various pumps from international companies whose sole existence relies on properly engineered pumps
     
    Last edited: May 6, 2021
  7. Dejay
    Joined: Mar 2018
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    Dejay Senior Newbie

    Another day, another Baader–Meinhof phenomenon:
     
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  8. Luke Frisbee
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    Luke Frisbee Junior Member

    I can't play with the pipe. it is 10 ft underground and concrete, but when I did bury it (and I mean literally I did, here is a thread on the construction..i wore out two shovels and a wheel barrel just digging the hole over an 18 month period Lake Luke http://winterholerct.net/lakeluke/ ).
    And I used long sweeps to reduce the friction.
    However I know little of jet ski props. But from just conceptualizing them...they seem to be engineered to send water in a particular direction at significant pressures. remember I want the physical mexhanism (propeller) to just get water past the end of the pipe, direction is irrelevant. And having the water "go everywhere" after it makes it from the pipe opening should reduce pressure so raise volume even more ?
     
  9. Luke Frisbee
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    Luke Frisbee Junior Member

    I am not dismissing your input anymore than you dismissed my query... but.
    I have had consultations with two of the very top axial flow pump creators/manufacturers in Central Florida. One designed and constructed axial flow pumps for Cape Canaveral's issues. And the other designs pumps for use all over the world for agricultural uses even though they are located in FL. Both fabricate their own pumps using the most advanced software and successful engineers.
    While the Cape Canaveral source would not attempt to make such a small pump, the owner of the company to my South had always wanted to design a small pump. And he took it on as a pet project. I am not giving his name because I consider him to be a great man and he was doing me a favor while chasing his folly at my expense.
    And when the pump failed to deliver the flow rate he believed he could produce, even after several modifications, he refunded my money and told me to just keep the pump. His shortcoming was that he never dealt with pumps with less than XX horsepower, and so when thinking of fractional horsepower motors he assumed almost all the horsepower was available for work and had no idea of the loss of power due to the motor itself.
    I've written the above so you have some idea that I have not tried to find a pump that does the function I am imagining/needing.
    What I am trying to do is just capture as much of the water that is displaced by a propeller once it interacts with a small circular cross-section of "still water."
    That one small prop moving through that "cylinder face" of water creates this huge gigantic plume/volume of water. How can I pull at least some of that through the pipe? I think by removing the prop/pump from a consigned space on the "delivered" side the pump will not suffer the huge loss created by turbulence/friction (or whatever other term).
    For several months I considered this contraption. (Acquired and modified to the point of uselessness. then rebuilt and a friend uses it for aeration.)
    Lake Circulators & Mixers | Surface Aeration | The Pond Guy https://www.thepondguy.com/category/pond-and-lake-circulators
    It was an improvement, but most of the water it moved was created on the output side of the mechanism. And while tinkering with it I could see/identify/imagine that the prop was recruiting most of the water movement outside if its prop circle. So I am where I am...trying to understand and find the sweet spot for the prop to be from/in the pipe opening to get the very highest volume at the very lowest head. And to do so I have to understand water movement off of a prop...like a trolling motor or small outboard prop. But then am I right about that? Should I use a large outboard prop at a lower rpm?
    Some of you guys has to know?
     
  10. Barry
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    Barry Senior Member

    Luke, if you are seriously trying to design a new pump that will save the planet a bit, but reducing the amount of power required to turn it you need then to ask questions that give some pertinent
    parameters.
    Then the contributors may participate in giving you a more complete answer. Some of the parameters are

    1) How much water do you want to move?
    2) what is the water pressure differential between both ends of the pipe
    3) Is the intake flooded
    4) Is the intake source a large volume, ie to determine water supply availability with low inlet velocity, this would affect the pitch
    5) You say a fractional horsepower motor, pick one between .0001 hp to .9999 hp as the available energy is necessary to even begin calculations
    6) you said that you used large 90 degree bends, the radius of these bends are necessary to determine pipe losses, ( an off the cuff method was something like every 90 degree standard bend was somewhat equivalent
    to 10 feet of straight pipe losses, sweep L's less etc
    7) you need the pitch and diameter of the prop, " I want to put a prop at the end of a pipe and pull water through that pipe at the highest VOLUME possible, head/pressure be damned." This statement contradicts your comment you want a
    "most efficient" pump to " save the planet a bit". Efficiency here is taken as the lease amount of power to move the design volume of water
    8) There will be more parameters of course, some hardly necessary, water density and particulate, water temperature, inlet and outlet physical dimensions, and many more.

    But firstly,
    Tell us how much water flow do you want for a given amount of fractional horsepower available, head numbers, flooded suction or not, and you will probably get some pertinent answers.
    Also decide which is important, ie highest volume, pressure be damned or least amount of energy used. Pick the volume, give us the parameters, the amount of energy used will be the result of where you focal point is.

    And if you want dollar savings, give us your local cost per unit energy of electrical charges in your area.

    It is difficult to respond with an estimate with a prop of unknown characteristics, pitch diameter etc, a targeted flow rate, etc and get a proper response
     
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  11. Luke Frisbee
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    Luke Frisbee Junior Member

    Agreed.
    I spent well over two years building a koi pond that ONLY wealthy people own.
    Lake Luke http://winterholerct.net/lakeluke/
    The finally volume was a little over 50,000 gallons. The old belief is that a koi pond should be turned over at least 1/hour for effective filtering and maintaining of the water quality. (The adage in the koi world is that "koi hobbyist don't keep koi, they keep water.")
    If I used swimming pool pumps it'd be $500/month. With centrifugal pumps designed for the hobby it will be half that... right now with an airlift system I am getting a turnover of about .5/hour for less than $40/month.
    Unfortunately when I built the pond I was designing to use low pressure high volume, axial flow, fractional horsepower pumps. I even had one designed and built. On paper it could deliver 40,000 gph at 3ft of head. In practice it got half that. And if I remember right the motor was close to 1hp...maybe it was a .75 hp.
    So while I am open to new ideas of how to build/design an extremely low head (an inch if that) with an extremely high flow 50,000 gph. The limitations is the water must pass through a 6-inch diameter pipe 30 ft long with two sweeping 90 degree turns. The device could be placed on either end, but I have chosen to investigate the discharge end of the pipe to reduce the turbulence/friction within the confines of the pipe, and allowing the water that would naturally sweep off the end of the prop to aid in pulling water through the pipe.
    So I thought some of the brains on here that understand the dynamics of waters in the presences of various props to aid me in the correct choice of prop type and size, as well of the placement of the prop in relation to the pipe's discharge end.
    Like I stated in mym opening post... my head starts spinning in similar directions that the water does when I look and thing about the water coming through and off those props.
     
    Last edited: May 6, 2021
  12. Luke Frisbee
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    Luke Frisbee Junior Member

    first thanks for such a thoughtful response, and the effort it took to create your post... I will try to answer all your questions but some of them require me to have more knowledge than I do to even fully understand the question.
    I have linked my pond build at least twice already, but so you don't have to go search for it:
    Lake Luke http://winterholerct.net/lakeluke/
    The first page shows me with hand on shovel
    The last page shows the attempt at an axial flow pump with three feet of head...which did not really reach the claims to be truthful.



    Now to answer your questions...
    The head pressure would ideal be a fraction of an inch.... Romans moved water a mile with a couple of inches of head. The goal is not a quantity of water but the ability of the system/concept/prototype to deliver the highest volume for the least energy consumed.

    1) How much water do you want to move?
    it is more about getting an understanding of whether a "zero head" prop pump can deliver a dramatically higher volume of water once every effort is made to reduce turbulence, drag, friction, and head. It is the concept more than a finite fit for my pond.

    2) what is the water pressure differential between both ends of the pipe
    Typical koi ponds use 2 inch diameter pipe. I used 4 inch for eight bottom drains...which supply a reservoir which has the supply side of the 6 inch diameter pump in it. there is a 5 sq.ft. hole through an adjoining wall between the main pond and the discharge side of the 6-inch pipe.
    So let's just keep it simple... there is "zero head" difference between supply side and discharge side. The two main issues I see are the choice of props in terms of pitch, diameter, number of blades and design..like is a 10 inch, rounded edged, four blade 8 degrees of pitch outboard prop going to pull more water than a 5 inch, 2 sickle bladed trolling motor prop when attached to a .5 hp submersible motor and should a waterproof shroud be made, and should the prop be placed in the shroud or just right at the edge?

    3) Is the intake flooded
    Yes. And can be adjusted to any level within the water column..not that it matters much but with the current airlift system the intake end is perpendicular to the surface and about 6-10 inches below the surface and has a vortex where the hollow center dips about an inch and is about an inch wide. (It is one of the ways I can eyeball the pond and determine if the airlift is working.

    4) Is the intake source a large volume, ie to determine water supply availability with low inlet velocity, this would affect the pitch
    This question is something I am having difficulty with...
    the pond is 50,000 gallons. Eight 4-inch pipes feed the settlement chamber in which the input side of the 6-inch pipe stands. Right now five of the 4-inch pipes are intentionally blocked (this facilitates better water movement in the pond for filtration purposes. no need to discuss further, but If/when this pump design works I can open more 4-inch pipes to feed the 6-inch pipe. As of now the filtration chamber water level is less than an inch below the pond (which is desired and maintained because when I open more of the 4 inch pipes the flow through the pipes becomes so slow that they do not remain completely open). Basically an unlimited water supply with less than 2 inches of drop if I were pulling 75,000 gph or more. but that is just a Wild *** guess from looking at this system for many years.

    5) You say a fractional horsepower motor, pick one between .0001 hp to .9999 hp as the available energy is necessary to even begin calculations
    I purchased a Burcam Model 300910 version 2015, 115v, .5hp, 3.7amps. Part of the choice was how easily I could unbolt the motor from the centrifugal housing so I could re-rig it. I think it is a 3000 rpm motor. perhaps a slower rpm motor would be a better choice? But then I have little knowledge of prop dynamics.

    6) you said that you used large 90 degree bends, the radius of these bends are necessary to determine pipe losses, ( an off the cuff method was something like every 90 degree standard bend was somewhat equivalent
    to 10 feet of straight pipe losses, sweep L's less etc
    I am not so fixated on the frictional loss of the bends. I think they were sweeps, but that was over 10 years ago. There is little chance they were sharp 90 degree bends. and as there is no requirement in terms of a desired volume other than just trying to develop a better water mover at virtually zero head than a centrifugal pump. I think even now if I just placed the motor with the impeller an inch or two above the 6 inch pipe discharge opening I would get twice the flow I would than from attaching the pump as it came because water would not build pressure against the inside wall of the housing and be wasted.
    But I feel these impellers aren't efficient at all outside the housing compared to a prop.

    7) you need the pitch and diameter of the prop, " I want to put a prop at the end of a pipe and pull water through that pipe at the highest VOLUME possible, head/pressure be damned." This statement contradicts your comment you want a
    "most efficient" pump to " save the planet a bit". Efficiency here is taken as the lease amount of power to move the design volume of water
    HMM? I've reread the question a few times...here is a roundabout answer... The only givens are I want the motor to be less than 1 horsepower, and the water must all pass through the 6 inch pipe. Other than that I want to find a prop to attach the motor, and then attach the prop and motor to the 6-inch pipe in such a way that it will draw the most water it can through that pipe. And that is a different task... one which might require I add an extension rod to the motor shaft to get it a few inches further out of the way of the water movement, and or put a plate that extends out a distance from the pipe opening to keep water not in the pipe from being pulled into the flow created by the pipe and therefore stealing the created energy from the task. As well as one above the propeller if it would help? perhaps even make the one between the motor and the prop be a cone?
    But first..finding a prop that has the right characteristics and getting it positioned correctly in relation to the discharge side of the pipe. right?
    as to volume needed? If a .5 hp draws 50,000 gallons through the 6-inch pipe then while the rule of thumb of turning the pond over once per hour is accomplished I will smile. But the main interest should be on designing a no head, highest volume pump design..ok...perhaps a 2 inch head.... or 1 inch..or 4 inch

    8) There will be more parameters of course, some hardly necessary, water density and particulate, water temperature, inlet and outlet physical dimensions, and many more.
    Ah yes. water density...no water deeper than eight ft, particulate is suspended single-cell algae maybe an occasional leaf, the temp stays between 60 and 85f. We are not using a pump to titrate heart meds.

    But firstly,
    Tell us how much water flow do you want for a given amount of fractional horsepower available, head numbers, flooded suction or not, and you will probably get some pertinent answers.
    Also decide which is important, ie highest volume, pressure be damned or least amount of energy used. Pick the volume, give us the parameters, the amount of energy used will be the result of where you focal point is.

    And if you want dollar savings, give us your local cost per unit energy of electrical charges in your area.

    It is difficult to respond with an estimate with a prop of unknown characteristics, pitch diameter etc, a targeted flow rate, etc and get a proper response
     
  13. baeckmo
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    baeckmo Hydrodynamics

    So, if I understand you correctly, basically you want to pump 190 m3/h through a 150 mm pipe, 9.2 m long and with two "soft" bends. There remains two questions to be answered: what is the pipe material (for estimation of surface roughness) and what is the height difference between the surfaces of the supply reservoir and the pond. Now, reading through your novel above, it seems there are some additional chambers or manifolds; ie we are not looking at a simple "reservoir-pipe-recipient" system. Give us a sketch of the system, with heights and distances, then we can point you in the right direction. Remember, the losses occur in the system, the pump works to compensate for them.

    You must start with defining the requirements of the system, then the pump selection and the required power comes out as a result. The pump has to: A/ accelerate the fluid from zero speed to 2.9 m/s (in your case) and B/ overcome the friction losses in the pipe, bends, area changes and whatever, at that speed. Since the hydraulic power required is the product of flow (m3/s) times pressure differential (N/m2), this is what the pump must supply with the highest possible efficiency (=least losses). Its physical configuration is a function of flow, head and shaft speed (or cycle frequency if pulsating).
     
  14. Dejay
    Joined: Mar 2018
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    Dejay Senior Newbie

    For pure efficiency, looking into research on Pumped-Storage Hydropower could be worthwhile. They can reach 80% roundtrip efficiency so 90% one way. Which already sounds pretty incredible to me.
     

  15. Luke Frisbee
    Joined: May 2021
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    Location: Indialantic FL

    Luke Frisbee Junior Member

    I did google it, and I think you are going somewhere I am not.
     
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