TRC-SFD-1-07 - Tribology Group - Texas A&M University

More documents

Recommendations

Info

Executive SummaryOpen end squeeze film dampers operating with low levels of pressurization are proneto air ingestion and entrapment that drastically reduce their damping capabilities. Endseals can significantly reduce the severity of air ingestion. A prior TRC report [3]advances an experimental work to identify the force coefficients of a combined squeezefilm damper and mechanical end seal. The test damper configuration includes outlet portsfor oil flow through the damper at the sealed end. The system parameters are identified ina two step procedure. First, the mechanical seal friction force is identified from circularorbits tests prior to pumping oil through the damper (i.e. dry system). Second, thesqueeze film force coefficients are extracted from the system force coefficients identifiedfrom circular orbit tests with oil circulating through the damper.This report extends the experimental work advanced in [3] to include theidentification of force coefficients for the same SFD damper but with closed outlet ports(i.e. no-thru flow). An identification method, suited for non-linear systems, allows tosimultaneously identify the squeeze film force coefficients and dry friction forceintroduced by the mechanical seal. The identification procedure shows similar (within10 %) damping and added mass coefficients than those reported for the thru-flowconfiguration. The oil temperature in the squeeze film land does not increase significantlydespite the no-thru flow condition. The oil temperature remains constant due to the shortlength of the experiments, the relatively small amount of energy (work) input into thesystem, and the large amount of oil stored in the SFD inlet plenum. In an actualapplication, the no-thru flow condition is expected to lead to an increase of the oiltemperature and a significant reduction of damping.In addition, tests are conducted to find the onset excitation amplitude and frequenciesleading to air ingestion. The results, for the maximum allowable shaker loads,demonstrate no evidence of oil cavitation in the damper land. On the other hand, for thelargest test amplitude (74 um at 50 Hz) and one of the highest test frequencies (32 um at100 Hz), the experiments indicate the ingestion of air into the SFD land. Visualobservations of the SFD land shows that, besides the seal interface, air is being ingestedthrough other passages including the juncture of the instrumentation facing the damperfilm land. The amount of air ingested is relatively small and the damper performance isnot greatly affected.2
Table of ContentsExecutive Summary............................................................................................................ 2Nomenclature...................................................................................................................... 6I Introduction ...................................................................................................................... 7II Literature Review............................................................................................................8III Test Rig Description .................................................................................................... 11IV Parameter identification............................................................................................... 14IV.1 Experimental procedure................................................................................ 14IV.2 Identification method.................................................................................... 16IV.3 Results: Dynamic force coefficients ............................................................. 20V Onset amplitude and frequency leading to air ingestion and lubricant cavitation in testSFD ................................................................................................................................... 26V.1 Experimental procedure................................................................................ 26V.2 Experimental Results .................................................................................... 30VI Conclusions and Recommendations............................................................................ 36VII References .................................................................................................................. 38List of TablesTable 1 Test conditions for dynamic load tests (CCO). Lubricated SFD......................... 14Table 2 SFD inertia coefficients and dry friction force identified from circular centeredorbit tests (frequency range 20-70 Hz, no thru-flow) ............................................... 22Table 3 Test conditions for dynamic load tests (CCO). Lubricated SFD. No thru-flow. 26List of FiguresFigure 1 Test rig for dynamic force measurements and flow visualization in a sealed endSFD ........................................................................................................................... 11Figure 2 Sealed-end SFD assembly cross section view.................................................... 12Figure 3 Sealed-end SFD assembly cut view. .................................................................. 13Figure 4 SFD housing reference coordinate system and location of sensors. .................. 13Figure 5 Recorded load and ensuing displacement orbits for four amplitude loadmagnitudes. Clearance circle noted. (20 Hz, lubricated SFD, CCO) ....................... 15Figure 6 Recorded load and ensuing displacement orbits for four amplitude loadmagnitudes. Clearance circle noted. (60 Hz, lubricated SFD, CCO) ....................... 163
Page 1: Texas A&M UniversityMechanical Engi
Page 5 and 6: Figure 22 Dynamic pressure measurem
Page 7 and 8: I IntroductionSqueeze film dampers
Page 9 and 10: A review of publications related to
Page 11 and 12: III Test Rig DescriptionFigure 1 de
Page 13 and 14: Oil inletEddy current sensorHousing
Page 15 and 16: 300Y Load [N](90 N,82 N)(98 N,88 N)
Page 17 and 18: M sM fK sxC SFDxxC SFDyyF djournalF
Page 19 and 20: 2( ω−ω− )F = L x + F u ; L =
Page 21: configurations including open outle
Page 24 and 25: capacity of 4.1 kJ. In actual appli
Page 26 and 27: V Onset amplitude and frequency lea
Page 28 and 29: Figure 14 Excitation load and respo
Page 30 and 31: V.2 Experimental ResultsFigure 17 s
Page 32 and 33: 1.5Pk-Pk Pressure (bar)10.532 μm50
Page 34 and 35: Absolute Pressure [bar]24001.75Pres
Page 36 and 37: VI Conclusions and RecommendationsT
Page 38 and 39: VII References[1] Delgado, A., and
Page 40 and 41: Appendix A Identification of dry fr

TRC-SFD-1-07 - Tribology Group - Texas A&M University

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?