Comparing Compressible and non compressable flow

[rgmix]

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?

 

[zdas04]

Convert both to mass flow rate terms and the comparision is valid (and straight forward)

David Simpson, PE
MuleShoe Engineering

http://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"

 

[KernOily]

??? What? How can they be compared? Mass rate??? Or volumetric rate? Either way, what about the huge density difference between liquid fuel and gaseous air? Maybe I misunderstand your question? Are you trying to estimate pressure drops and heat transfer, or what?

Thanks!
Pete

 

[FredGarvin]

I'm just curious as to why you would flow a liquid through an ACM. How would you expect to sustain the cycle? Would you drive it externally?

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.

 

[gstark]

I would suggest you contact the manufacturer of the ACM, whether that be H-S, Honeywell, B-C, Liebherr or ??? Your question is pretty puzzling to me, as I can't envision why you would want to do this. I am sure you can connect with their engineers - if not, I may be able to provide some contact information with their ECS departments.

BTW, you may have better success with this question in the Aircraft forum.

 

[rgmix]

We are testing a component of the Air Cycle Machine. We are exploring alternatives to test repair parts without incurring into the expense and time of having to test it on an actual Air Cycle Machine, if we are only testing one component. The Air Cycle is tested using air. We are testing the component using Calibrated Fluid. We are recording outlet flow of the fluid in gallons per minute. The actual test results is in pounds per minute. My results are in volumetric rate (calibrated fluid) and mass rate (Air).Thus, the need to compare taht both results are good.

 

[btrueblood]

Uh, sorry rgmix, but your post is awfully confusing to me. First, what is an "Air Cycle Machine" -- I am reading this to mean an air-breathing engine. You are testing a component of this machine, fine - what component (it could help us to figure out a bit more of what you are trying to do)?

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.

 

[FredGarvin]

An air cycle machine is essentially a turbine assembly that is fed compressed/hot air from the compressor bleed of an aircraft's engine. That air is passed through the turbine in the ACM. The resultant work extraction keeps the turbine moving and also produces a temperature drop in the air stream. The air stream is sent to the cabin/fuselage for various uses such as air conditioning.

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.