Flexure Plates for Turbine Test Rig 1

[jfaucher]

I'm looking for suppliers (or engineering cues to design by myself) a set of 4 flexure plates that must support a turbofan engine and its adapter structure (approx. weight 8,000 lbf). These plates act as flexure hinges in order to transfert axial thrust to a load cell, but must support rigidly any other degrees of freedom. Any idea where could I find the expertise?

 

[rb1957]

it should be easy enough to design a truss to react the maximum engine thrust. use the most convenient RSJ to hand, skin it over with what ever plate you have lying around ... lick of paint

 

[tbuelna]

jfaucher,

Turbofan (as opposed to turboshaft) engines are primarily designed for fixed-wing aircraft use, and must be mounted as prescribed in the installation document (ICD) produced by the engine OEM. Even though you state that your test stand will employ some sort of "adapter structure" for mounting the engine, the ICD requirements should still be thoroughly reviewed.

Most turbofan engines are configured for a three point mounting system, where each mounting point is designed with the correct degrees of freedom such that the engine can thermally expand independent of the mounting structure or pylon. And conversely, so that the pylon structure may deflect under load without inducing unnecessary strains in the engine's structure.

The turbofan engine's forward and rear mounting points are always located on heavy, intermediate case structures, to prevent distortion of the lightweight shrouds surrounding the fan, compressor and turbine blade tips. The blade tips run with very tight clearances to the shrouds, so any distortion of the shroud case would produce blade tip contact and have catastrophic consequences. This is why it is imperative that the requirements outlined in the engine model ICD be followed to the letter.

To do a safe and reliable design of a mount for your test cell, I would first recommend obtaining a copy of the engine model ICD from the engine's manufacturer. I'm sure they'll be happy to provide one, even if the engine is not a current production model. The ICD will give very detailed design data for engine mounting with regards to loads, thermal limits, structural stiffnesses and frequencies, dimensional tolerance limits, potential hazards due to uncontained rotor burst or combustor burn through, location of inspection points such as borescope ports and chip detectors (that you may wish to have access to on your test stand), etc. The ICD will also give guidelines on designing whatever provisions your test stand will have for intake and exhaust flows, fuel flows, bleed air flows, FADEC interface, etc.

Finally, take some time to analyse and fully understand the various vibratory modes of your test stand structure to make sure they will not couple with any modes occurring in the engine during operation. Since during testing you may wish to use accelerometers to monitor for things like rotor unbalance, and vibration response of the test stand structure may make this difficult.

Good luck.
Terry