Air Motor and Compressor calculations

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rcbondsr Power-User Join Date: Mar 2008 Location: Washington State Posts: 113 Good Answers: 1	Air Motor and Compressor calculations 06/05/2008 2:37 AM
	Hi Folks, Can someone point me to calulators or formulas for calculating torque out vs air pressure in for vane type pumps or compressors and motors ? Trying to make sense of an energy problem, and the engineering class was too long ago. Thanks rcb __________________ Testing =Testing -Testing -- We create our society each time we interact with another person. What kind of society did you create today. RCB
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	Pathfinder Tags: calculation Pressure torque

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PWSlack Guru Join Date: Jan 2007 Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on. Posts: 32175 Good Answers: 839	#1 Re: Air Motor and Compressor calculations 06/05/2008 3:43 AM
	Shaft power (without losses) = pressure change x volumetric flowrate Does that help? __________________ "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
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Codemaster Guru Join Date: Jul 2005 Location: Stoke-on-Trent, UK Posts: 4496 Good Answers: 137	#2 In reply to #1 Re: Air Motor and Compressor calculations 06/05/2008 7:19 AM
	And power = torque x speed. __________________ Give masochists a fair crack of the whip
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PWSlack Guru Join Date: Jan 2007 Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on. Posts: 32175 Good Answers: 839	#3 In reply to #2 Re: Air Motor and Compressor calculations 06/05/2008 8:54 AM
	Yep! __________________ "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
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rcbondsr Power-User Join Date: Mar 2008 Location: Washington State Posts: 113 Good Answers: 1	#5 In reply to #2 Re: Air Motor and Compressor calculations 06/05/2008 11:46 PM
	Where do we get the torque - must be a calculation somewhere round here.??! :) __________________ Testing =Testing -Testing -- We create our society each time we interact with another person. What kind of society did you create today. RCB
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rcbondsr Power-User Join Date: Mar 2008 Location: Washington State Posts: 113 Good Answers: 1	#4 In reply to #1 Re: Air Motor and Compressor calculations 06/05/2008 11:45 PM
	Where do we get the conversion from Pressure to torque - Different size air motors surely have different torque curves etc. How to figure ? Or must we first find a motor and look up the manufactures specs.?? rcb __________________ Testing =Testing -Testing -- We create our society each time we interact with another person. What kind of society did you create today. RCB
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Codemaster Guru Join Date: Jul 2005 Location: Stoke-on-Trent, UK Posts: 4496 Good Answers: 137	#6 In reply to #4 Re: Air Motor and Compressor calculations 06/06/2008 4:33 AM
	Hello rcbondsr You know discharge absolute pressure P₂. If you know inlet flow q you can calculate compressor input (shaft) power W. For compressible flow it's a bit more complicated than PWSlack's post #1. P₁ is inlet absolute pressure. n is polytropic exponent, usually 0.23. If you don't know inlet flow direct, you can get it from speed, swept volume per rev, and volumetric efficiency. VE I'd guess 90 - 95% for sliding vane type, but somebody may know better. Dividing power by compressor speed gives torque. Need to do it all in consistent units, I prefer SI. Note speed needs to be in rads/sec. Cheers.......Codey __________________ Give masochists a fair crack of the whip
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Codemaster (2); PWSlack (2); rcbondsr (2)

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