Measuring Back Pressure Without an Engine 1

[ChrisPoyaa]

There are many techniques on how to measure backpressure in an exhaust system that is already connected to an engine. How can you measure the backpressure in an exhaust system if it is not going to be connected to one though? What could you use to represent the airflow and backpressure to match what the engine would create (or something proportional) to see if the backpressure is within the specifications? The engine is a 3.0L V6 VM Turbo Diesel. Thanks for the help!

 

[ChrisPoyaa]

Yes, this would be sampling not 100% testing. Although buying an engine might be the easiest and most accurate testing, it wouldn't be very time efficient for a quality lab or the cleanest method for testing parts that are still going to be sold. The manager of this project wants compressed air as the source of the "exhaust" through the system.

dgallup, everything you just described seems very plausible. This article describes the operating principles of sonic nozzles very well for someone interested.

I don't have any experience/knowledge with sonic nozzles. Is the pressure ratio mentioned achieved soley by pressurizing the inlet of the nozzle?

 

[ChrisPoyaa]

here we go:
"The mass flow rate is primarily dependent on the cross-sectional area A of the hole and the upstream pressure P"

 

[IRstuff]

3L * 3000rpm = 318 cfm, so you need something like these:

http://us.kaeser.com/Products_and_S.../with-1-to-1-drive-up-to-315-kW/default.asp#0

TTFN
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[1gibson]

What do you do once you build this setup, then are asked to simulate a larger engine that the setup can't accommodate? Did the manager of the project consider that?

 

[Lou Scannon]

The microturbines with which I am slightly familiar _really_ don't like backpressure.

...hence my use of the word "tailored". The microturbine will not need to deliver any shaft power. I don't know if this will work easily, it's just an idea.

"Schiefgehen will, was schiefgehen kann" - das Murphygesetz

 

[IRstuff]

Those diesel compressors go up to 2000 cfm

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[hydrae]

Blower packages that are used in waste water treatment plants can produce the flows and pressures you are looking for.
They can come complete with sound insulation and controls.

As for a way to produce a specific backpressure out of the PD blower, have a tee between the blower and test bench that will feed a pipe submerged in a water tank at the level of water corresponding to the pressure desired (want to test at lower pressure, remove water), the pressure to the test bench will build up to the static water head and excess flow will bubble through the bypass providing a reliable pressure source.

Hydrae

 

[MikeHalloran]

Hydrae's got a great idea there.
Big ol' Roots blower and a submerged branch pressure vent.
You _will_ want the sound insulation.



Mike Halloran
Pembroke Pines, FL, USA

 

[Lou Scannon]

Or something maybe a little quieter & more compact: Procharger
You still would need to figure out & engineer an electric motor drive, as well as the conversion from exhaust conditions to equivalent air flow @ temperature.


"Schiefgehen will, was schiefgehen kann" - das Murphygesetz