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Test Bed
2

Test Bed

Test Bed

(OP)
Hi,
I am trying to determine if it makes a difference for a test bed to have the following options? This test bed will test a turboshaft / turboprop engine.

The arrangements on the test bed are:

1) Engine -> Flywheel -> Dyno
2) Engine -> Dyno -> Flywheel

Would these setups affect the torque? Friction?

Would you have any references.

Thank you,

Gabriel

RE: Test Bed

i'm not a propulsion guy but here goes ... the engine is being tested and the dyno is showing the data (the power output of the engine)?  i'd've though that putting the flywheel between them would "smooth" out the data, the power coming out of the engine, so i'd vote for config 2.

RE: Test Bed

At some level, it shouldn't matter, should it?  They're all coupled together, and the engine is required to drive both.

At another level, the flywheel could represent the normal load on the engine, so a direct coupling between the engine and the flywheel would make sense.

Ultimately, you need to determine, possibly by asking around, what the intent of the flywheel is.  Only then could you ask where it's supposed to go.

TTFN

FAQ731-376: Eng-Tips.com Forum Policies

RE: Test Bed

(OP)
That's what I think too ... it's doesn't matter. The flywheel is used to store energy (absorb torque) during engine acceleration. The only reason I could see is that the dyno cannot handle the max torque by the engine so the flywheel must be placed between the the dyno and the engine. That's the only reason I can see, other than I don't know. If anyone has another idea, feel free to share.

Thanks guys!

RE: Test Bed

It also depends on the type turboshaft engine you are testing.  A free turbine (PT-6 as in King Air ir Huey) will need some sort of flywheel to allow inertia and rpm to build before measurement.  It is possible to start a free turbine with the output shaft tied down or overloaded and measure almost no power.  The gas generator (core jet engine) RPM is also not matched to shaft speed, but balances energy produces against load applied to control output RPM.
..
A direct drive engine won't need any flywheel at all (T-56 as in a C-130).  It can go direct into the dyno.

RE: Test Bed

You probably need to look at your torsional vibrations.

(1) is what is used on a typical IC engine, and (2) is effectively a chassis dyno.

(1) is nice because the flywheel decouples the two other shafts for TVs.
 

Cheers

Greg Locock

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