dx upper tree-house & fan 12 june, 2010 esguerra
TRANSCRIPT
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DX Upper Tree-House & Fan
12 June, 2010Esguerra
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Definition
• “Blue sky” recommendations assume– Sufficient budget– Sufficient schedule– Sufficient manpower
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Access from this side.
M3 swing-arm
•Upper DX tree-house structure• Rigidly attached to C-ring extension• Upper fan enclosure also rigidly attached to C-ring extension
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•Upper DX tree-house structure• Attached to C-ring extension• Upper fan enclosure also attached to C-ring extension• All rigid attachments
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Comments• It makes sense to isolate the C-ring extensions from any source of
vibration• The tree-house and tree-house ventilation are vibration sources
– As demonstrated through AO testing– As demonstrated through vibration testing
• “Blue-sky” recommendation– Replace all rigid attachments to the C-ring extension with isolation
• Wire-rope isolator?• Elastomeric?• Flexure?
– Isolation performance should be *tested*• Quantitative test of isolation under representative loading• Testing before and after installation
– To verify improvement– To quantify performance
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DX Upper Tree-House Fan
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DX Upper Tree-House Fan Motor
• Operating at current low speed (16-Hz), there is obvious undesirable motion of the motor
• Motor is mounted through elastomeric pads to sheet-metal– The sheet-metal base is probably as compliant as the isolators for small displacements
• Whole motor assembly wobbles– Compliance of the sheet-metal structure– Varying belt tension during operation– Motor imbalance / cogging?
• Belt might also have dynamics– At higher speeds
• Balancing the fan will not fix any of this
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Tensile Load
Motor rocking motion(coning)
Rubber mounting pads
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DX Upper Tree-House Fan
• Fan is a “squirrel cage” type• Connected to motor by belt/pulley (1:1)• Bearing and pulley attached to sheet-metal
through flimsy looking assembly
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Tensile Load
I would guess that this is not very stiff.
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“Blue-Sky” Recommendations
• Eliminate pulley system– Direct drive, or through viscous damper, or bellows– Use a different fan/motor
• Attach fan and motor to common “frame”– Frame should be stiff– First mode (of assembly) should be higher than motor disturbance
• Should be able to measure motor disturbance frequencies directly• <1-second decay; (8% damping@10-Hz, decreasing OK with higher frequencies)
• Isolate common fan/motor frame– Isolate fan/motor connection to tree-house
• Isolation first mode should be less than lowest motor/fan disturbance frequency• Damping is good (don’t use normal springs)• Wire rope isolation?• Flexible ductwork from tree-house to fan assembly/heat exchanger compartment
– Isolate connection to C-ring extension if connection is necessary
• Balance fan/motor before reinstallation– Recommend testing in-lab before installation
• If there is still appreciable vibration– Additional passive or active vibration attenuation at the fan/motor frame– TMD or active vibration control
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“Blue-Sky” Recommendations
• Isolation performance should be *tested*– Quantitative test of isolation under representative loading– Testing before and after installation
• To verify improvement• To quantify performance