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2. SINGLE POINT AND TWO POINT CONTACT
ANALYTIC SINGLE CONTACT MODEL
ANALYTIC TWO-CONTACT MODEL
Flexible rotor
Elastically supported stator
One point of contact between rotor-stator.
Rigid rotor
Elastically supported rigid stator
Two points of contact between rotor-stator.
Figure cited from-Childs, D. W., and Bhattacharya, A., 2007,
Prediction of Dry-Friction whirl and
whip between a Rotor and a Stator, ASME J. Vib. Acoust., 129, pp.
355362.
3. EVENTS LEADING TO 2 POINT DRY FRICTION INVESTIGATION
4. Faulty sensors had a dominant vibration frequency separate
from the rotating speed. 5. Effected sensors exhibited spiral sort
of motion, NRG systems perceived it as self excited vibratory
phenomena. 6. Dr Childs confirmed NRGs suspicion that the observed
phenomenon was dry-friction whip. 7. Low RCl and friction was the
reason of occurrence of dry friction whip. 8. Anemometer has a
rigid shaft with a mass disk at roughly its center, this rotor is
supported on 2 Teflon bearings, the rubbing contact. Radius to
clearance ratio is of the order of 30Solidworks model NRG#40
anemometerby `NRG systems
Solidworks model NRG#40 anemometerby `NRG systems
9.
10. Assuming:(i) Contact always occurs at both locations,and
(ii) The same radius-to-clearance (RCl) ratio holds at both contact
locations Mode1 and Mode 2 solutions were developed.Figure cited
from-Krkkinen, A., Helfert, M., Aeschlimann, B., Mikkola A.,
Dynamic Analysis of Rotor System With Misaligned Retainer Bearings,
ASMEJ. Tribol. 130, 021102 (2008)
Method of Research
11.
12. The equations were derived using Lagranges Equation 13. The
above equation is in complex form where ROTOR DIAGRAM
Analytical model
14.
15. The equation is in complex form, whereSTATOR
DIAGRAM
CLEARANCE DIAGRAM
Analytical model
16.
17. Mode 2 solution developed- Assumed planar precessing mode
with the normal reaction contact forces out of phase at the two
contact points. 18. These solutions were evaluated for three
different configurations Disk at center
Disk at location
Disk at overhang location
Analytical solution
19. Model Definition
connected to any piece of Turbomachinery.