Comparing Compressible and non compressable flow
Comparing Compressible and non compressable flow
(OP)
We are testing flow through an Air Cycle Machine (airplane Environmental system). We need to know if air and fuel could be compared to measure the flow through the sytem. Can both be compared? can the results be acceptable? If that is possible, is there an specific formula or maybe a web site where the information could be obtained?





RE: Comparing Compressible and non compressable flow
David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
The Plural of "anecdote" is not "data"
RE: Comparing Compressible and non compressable flow
Thanks!
Pete
RE: Comparing Compressible and non compressable flow
The question does need clarification. What is it exactly that you are looking for? If you are looking at things like pressure drop, etc... I would think you would need to consider similitude, equivilent reynolds numbers and such.
More specifics, please.
RE: Comparing Compressible and non compressable flow
BTW, you may have better success with this question in the Aircraft forum.
RE: Comparing Compressible and non compressable flow
RE: Comparing Compressible and non compressable flow
Let's assume it's a fuel pump. You test the pump at a specified airflow through the engine, and verify its output in gallons per minute (you could also bench test the pump by spinning its shaft at the same rpm that it would see if connected to an engine flowing the specified amount). Convert the output to lbs per minute to compare to the specified flow rate of lb/minute. To do this, you need to know the fluid density in lb/gallon, then multiply the volume flow by the density to get lb/min units.
RE: Comparing Compressible and non compressable flow
If you're simply verifying flow capacity, then what has been mentioned about comparing mass flows is applicable. The density of cal fluid is readily available.