Positive displacement pump designs, efficiencies, small

[fastline12]

We are helping a friend with an air pump requirement and thought you guys might have some info from the automotive super charger area. Basically making a pump to test some proprietary components. pump MUST be compact, light weight, and positive displacement.

So far, all I am familiar with is twin screw and roots. Centrifugal is out because it is not pos disp. I think most roots type pumps are pretty heavy. We only need to move about 20-30ci/rev of air. As I understand it, a 6-71 blower is designed to provide 71ci of air to 6 cyl per rev??? Is that right?

This will have to be a custom design for fitment reasons so not really shopping for a ready made solution, but rather just the design types so we can hug a direction. I am not quite sure what efficiencies have been achieved but I seem to remember the twin screw has been able to hold decent eff over a decent range in the past. is that accurate?

 

[patprimmer]

Rots blowers are sometimes used to pump air for materials handling systems. Some for that application may suit.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[gruntguru]

Aisin AMR 300 displaces 300cc per rev and spins tho 16,000 rpm. It is quite compact after removing the pulley and plumbing seen in these shots.

http://www.austarletclub.com/forums/index.php?showtopic=10438&mode=threaded&pid=112077

Engineering is the art of creating things you need, from things you can get.

 

[fastline12]

That AMR a really cute!!! I might just have to see if I can find a few of those. I could not find any info to see if they are a straight lobe design or helical screw?

Also, on the rotary vane stuff, I wanted to ask about the elliptical housing designs with dual inlet/outlet. It would seem these might be a great design for high volume, low pressure to reduce pump speed requirements and reduce wear? Looking at some ballpark numbers, it looks like PR 2 could be easily obtained as well as nearly double the flow and reduced radial load on the rotor. Plumbing complexity would be substantially higher though.

 

[fastline12]

Update - I was doing some simple number crunching on rotary vane and not finding them to be a very compact solution unless I have done something wrong. Simply using the swept volume x rpm x eff of 90% as a ballpark. Seems these pumps may be great for higher pressure at low rpm due to the good seal but might not be a good compact solution for high volume air.

Seems the movement of the vanes would LARGELY limit the rev ability of the pump so they could probably be made huge, swallow a large gulp real slow but doing it fast might really wear it out. hmmm.

 

[gruntguru]

AMR 300 has straight rotors, 2 lobes per rotor, PTFE coated. Used units typically fetch about $300 US. I did see someone in the US (on ebay) importing new units and selling for about $1000.

Engineering is the art of creating things you need, from things you can get.