Difference between revisions of "Progressing cavity pump"

Latest revision as of 18:22, 25 March 2025

Progressing cavity pumps (PCPs) also Moineau pumps.

Due to a quite astonishing and surprising geometric miracle despite …
– the smooth non translatory motion and
– the continuous non pulsing transport flow
this is a positive displacement pump with closed chambers.
As such it acts as a pump in the mechanical electrical analogy
more like a constant current source rather than a constant voltage source
(given a non compressible liquid as medium).

Nanoscale peculiarities – biaxial curvature issue

While uniaxial bent structures are nicely possible by bending strain and systematic substitutions and such
biaxial curvature (as in spheres and the complex curvatures of PCPs) is not so easily possibly.
Advanced methods to design and mechanosynthesize quasi amorphous structures could help in getting
inner walls of nanoscale atomically precise PCPs smooth to subatomic precision
thereby reducing friction and likely hood of backflow of smallest atoms and molecules like helium and hydrogen

Vacuum applications

Due to nanoscale atomically precise diamondois or more gemerally gemstone based
structures being possibly such tight that even high pressure helium can't leak through gaps,
these pumps will be usable to create very good (or even PPV) vacuum.

Due to molecular flow having a hard time to find one small outled from a big chamber.
One will want to cover walls with many nano PCPs
walls similar to the size of the chambers pumped down.

Advantage over trubomolecular pumps

Turbomolecular pumps need to operate near or above the speed of sound.
Atomically precise sliding bearings would cause extreme friction heat at these very high speeds
(see Nanoscale friction) so much so that they could not be operate steady-state in macroscopic quantities,
some sort of active nanoscale electrostatic levitation bearing could still make them practically
at a bit bigger scale.
There's the possible issue of backflow through bearing gaps.
Though ballistic molecular gas flow counteracts and
clever geometries with interdigitating blades on the inside too likely can completely solve that

Viscosity losses at near perfect vacuum are likely negligible.
For pumping at higher pressures larrger scale PCPs may be

Note that (while not totally obvious) there are two exactly equal 90° phase shifted reciprocative motions involved.
Four PCPs need to be paired up to compensate by counter-motions and hugely reduce radiated vibrations.
Higher multipole moment(?)

Possible disadvantages of piston based positive displacement pumps

• More parts and more complex assembly
• Possibly squeezed gas or liquid atoms (though the high thermals speeds compared to pump speeds might make that unlikely)
• Possibly more (complex) vibrations though PCP pumps feature two orthogonal 90° phase shifted reciprocative motions too. The wobbling.

Ideas

Usage as motor with inherent-direct-geardown and self-cooling

The concept could be reversed and used as a motor.
Wobbling the outer stator without rotating is around a fixed axis rotating inner rotor
Using pulling actuators in three or more phases for the wobbling.
The lobe number determines a decent gear-down ration.
If a gas or liquid is present it can act acts as a coolant that is automatically pumped.
Though this works better at larger scales due to falling viscosity issues.
Low pressure hydrogen or helium might work for nanoscale - to analyze.

(wiki-TODO: Add gif and OpenSCAD code.)

Related

• Quasi amorphous structure
• Reciprocation – reciprocation does not need to be translatory
• Reciprocative friction in gem-gum technology

External links

• https://en.wikipedia.org/wiki/Progressing_cavity_pump
• http://www2.mat.dtu.dk/people/J.Gravesen/MoineauPump/ ( nice page explaining the math - on internet archive too )
• http://www2.mat.dtu.dk/people/J.Gravesen/MoineauPump/HypoEpi4_3.html