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I'm tying to figure out what something is called, assuming it exists at all. If I knew what to search for, I'm reasonably sure I could figure out which part would be suitable for the application, but so far my searches haven't found anything applicable so I've got nothing to even start from.

What I'm looking for is a class of devices that can reduce hydraulic pressure from one side to the other while using the power it dissipates doing that to pump extra fluid volume from ambient pressure up to the low-pressure output side. I'd be interested in systems that reduce pressure either as a pressure regulator or as a flow controller. Either would work for the motivating uses case.


With enough cash and complexity budget (both in short supply), a variable displacement motor/pump set with the right controls should be able to do that (it might not even need much of a control system), but what I'm hoping for is something more in the cost/complexity range of a variable geometry venturi pump, even if it cost a modest reduction in overall efficiency.

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    $\begingroup$ While custom designs are not viable for the motivating case, I wonder if a wicket gate turbine could be used to drive a centrifugal pump? At low output pressure, the power stage sees a high drop and the pump sees high volume. At high output pressure, the power stage flows high volume and the pump stage basically stalls and consumes little power. $\endgroup$
    – BCS
    Jul 2, 2023 at 15:32
  • $\begingroup$ "Volume multiplying" necessitates a pump, and providing the pump with energy necessitates a turbine. Like a turbocharger, although at hydraulic pressures the mechanism would be different. $\endgroup$
    – Pete W
    Jan 14 at 23:08

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You can use a motor / pump combination.

There are motors and pumps that use the swash plate design and can vary pressure and flow from zero to max.

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    $\begingroup$ As noted in the question, that solution is precluded by cost/complexity constraints, that I have no control over. $\endgroup$
    – BCS
    Jul 2, 2023 at 15:22
  • $\begingroup$ @BCS without any idea of your budget $10 or $10000 you asked for ideas or at least a better indication of what to look for... You could try reading the Bosch/Mannesmann?Rexroth hydraulic tomes which would give you a very good idea. $\endgroup$
    – Solar Mike
    Jul 2, 2023 at 15:45
  • $\begingroup$ To get an idea of the kind of budget I'm constrained by, take a look at the last paragraph of my question. -- Tl;dr; something in the ballpark of a flow control valve is viable, something like a hydrostatic transmission is not. $\endgroup$
    – BCS
    Jul 2, 2023 at 17:05
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Something to look into is hydraulic intensifiers, combining this with a pump would theoretically give what you desire.

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    $\begingroup$ I didn't know that's what that device was called. -- But I'm actually looking for the exact opposite operation however; increased volume not pressure. Also, I'd need something that supports continuous operation (or at least more output volume than the volume of the device). $\endgroup$
    – BCS
    Jul 2, 2023 at 15:19
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Most pressure reduction is adiabatic, no work is done. Expansion cools the fluid and ambient heat is absorbed.

Certainly you can use high pressure fluid to do work to generate power, operate a shaft, etc. The output would be a lower pressure fluid. Numerous devices exist to do this.

I am unaware of a simple valve-type device which can be used to harness the energy and redirect it to another use. Certainly energy production at scale would point us to water turbines used in hydropower generation, which is just taking higher pressure water and turning it into electricity.

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