Is it possible to construct a solid state fluid system (tubing, channels, chambers, nozzles, etc.) that can convert the energy from a low-pressure high-flow-rate air current into a high-pressure low-flow-rate air current?

This is similar but not identical to this question, because in my case I am looking to use existing pressurized air as the energy source, but want to produce even higher pressure (even if the pressure is only slightly higher or there is significant energy loss). This question is also similar but seems to be asking a way to increase power, whereas in my case I don't care much about efficiency or power, only pressure. As an electrical engineer with no background in fluid dynamics, I see this problem as analogous to an electric transformer, with pressure being the analog of voltage and flow rate the analog of current. From an energy conservation perspective, it seems like it should be possible.

I realize the answer is trivial with pistons and gears but I am interested in a design that uses no moving parts, or if that's not physically possible, at a minimum uses only valves as moving parts. The hydraulic Trompe and Pulser pump are very close to what I want, but they involve water and gravity. I'm looking for something that uses only air.

The reason I am interested is because I've been reading up on pneumatic circuits and simple pneumatic devices, such as the Tesla valve, this pneumatic oscillator, and the complex no-moving-parts fluidic control circuitry described here. Particularly I am interested in constructing a "pneumatic integrated circuit", by stamping or carving channels and shapes into layers of some substrate and stacking them to produce tightly-integrated tubing circuitry in a single brick-like device. Valves that fully close may be possible in this scheme as described here. If such a pressure transformer is possible in an integrated context, I envision it could enable a variety of very simple and easy-to-build fluidic devices like audio amplifiers, mouth-operated musical instruments with artificial sounds, small-scale heat pumps and moisture collectors, and simple digital logic circuits, all powered only by moving air.

I would be grateful for any resources at all on fluidics that may be helpful, even if they don't solve my problem directly. Thank you for any answers!

  • $\begingroup$ flow to pressure- do you seek a diffuser? (opposite of a nozzle) $\endgroup$
    – Abel
    Commented Jul 7, 2021 at 12:54
  • $\begingroup$ ram jets do that by redirecting the supersonic flow of incoming air. $\endgroup$
    – kamran
    Commented Jul 7, 2021 at 15:13
  • $\begingroup$ Pipe sizes transform pressure. Moving air has energy and if you drop it into a plenum (tank or similar) the pressure will go up to reflect that energy. As to building a logic engine with pneumatic components, sure, it's just a mechanical computer. $\endgroup$
    – Tiger Guy
    Commented Jul 7, 2021 at 20:49
  • $\begingroup$ Yup, you build an electrodynamic generator and use it to drive an electrodynamic pump in the other stream. Here's a slightly larger version than what you had in mind ;) nrel.gov/docs/legosti/old/2277.pdf $\endgroup$
    – Phil Sweet
    Commented Jul 7, 2021 at 22:34
  • $\begingroup$ Um, can revisit the "solid state fluid system" description, because I'm a bit literal minded and it makes my head hurt. $\endgroup$
    – Phil Sweet
    Commented Jul 7, 2021 at 22:40

1 Answer 1


If you are really going to just change the pressure, with essentially no moving parts, the simplest way to do this is just by using diffusers.

In a fluid flow there is 3 types of pressure: 1) dynamic head, 2) static head, and 3) elevation head. Static head refers to the pressure of a fluid when it is at rest a.k.a. not moving. The value depends on the temperature and the pressure of the fluid that is at rest (to understand this in depth the easiest way is to learn the ideal gas equation). Dynamic pressure corresponds to the value of = 0.5density of the fluid(velocity of the fluid)^2. The elevation head is the pressure of the fluid relative to the reference height, as the height increase the pressure will go down, and vice versa.

The relationship of this 3 can be simply explained using the Bernoulli equation, which states that the sum of all three is always constant, given there's no energy into or out of the system (like heat, electricity, etc.). So, if we reduce the velocity of the flow with the same elevation, the static pressure should be increased.

In the case of diffuser (image attached), say from the inlet you have a high flow rate-low pressure air flow. When going into the diffuser, the flow area of the inlet is smaller than the outlet, and thus reduce the speed of the air flow, and thus increasing the static pressure.

The static pressure is the one that you should be focusing on. It is the one that interacts with all the objects around the flow, whilst the dynamic pressure and elevation is used more to correct the value of static pressure depending on the flow condition.

enter image description here

Hope that helps.


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