Low Air Compressor CFM Still Works?

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SUMMARY

The discussion centers on the feasibility of using a low CFM air compressor, specifically a 25 CFM model, to achieve the required 50-72 CFM for testing a mach 2 ramjet. It is established that the CFM rating of air compressors refers to mass flow, not volume flow. The participants highlight that typical air compressors do not allow for variable CFM settings and suggest using a large reservoir tank to store compressed air for sudden release as a potential solution. Isentropic equations indicate that a tank pressure of approximately 115 psi is necessary for the desired outlet conditions.

PREREQUISITES
  • Understanding of CFM as a measure of mass flow in air compressors
  • Familiarity with isentropic equations and their application in thermodynamics
  • Knowledge of air compressor types and their operational limits
  • Basic principles of pneumatic systems and reservoir tanks
NEXT STEPS
  • Research the specifications and performance of various air compressor models, focusing on CFM ratings
  • Study the principles of isentropic processes in thermodynamics for better understanding of pressure requirements
  • Explore designs for pneumatic systems that utilize large reservoir tanks for high-demand applications
  • Investigate alternative methods for achieving high CFM outputs in short bursts, such as using multiple compressors
USEFUL FOR

This discussion is beneficial for aerospace engineers, mechanical engineers, and anyone involved in experimental setups requiring precise air flow measurements and high-pressure systems.

yangshi
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Halfway through my thesis on a mach 2 ramjet, and I unfortunately realize that I need 50-72 CFM to test it. The only ACs I have are 2 CFM portable pancakes. Is it possible to run say a 25 CFM AC at 50 CFM for a short period of 10-60 seconds? Is there a quantitative way to find how long the AC will last above the required CFM?

I used isentropic equations to find that the required tank pressure is ~115 psi for mach 2 outlet, if that helps...
 
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Are you using "CFM" as a measure of volume flow or mass flow? According to http://www.truetex.com/aircompressors.htm the CFM rating of an air compressor is a measure of mass flow.

I don't know how you can run a typical air compressor at a variable CFM. I suppose the flow rate varies as you make it work against more and more pressure, but haven't seen any compressors where you can set the CFM to a specific value.

Can you get a large reservoir tank and slowly fill it with compressed air, then release the air suddenly?
 
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