Category: Papers

Survey Of Experimental Data For Fixed Geometry Hydrodynamic Journal Bearings

Swanson, E.E., Kirk, R.G., 1997
ASME Journal of Tribology, 119, pp.704-710.

Abstract

An extensive survey of the experimental research on the static and/or dynamic characteristics of fixed geometry, hydrodynamic journal bearings available in English, in the open literature is presented.  The type(s) of bearing, size of bearing(s) and range of parameters measured in each work are reported for slightly over 100 published experimental works.  In addition, some general observations about the available experimental data sets are made.  This annotated survey is intended to help the analytical community by providing an extensive list of sources of experimental data for use in analysis verification.  It is intended to help the experimental community by  highlighting the shortcomings of the available literature, as well as by providing a list of sources for appropriate data to help with current and future test rig debugging.

Test Results And Numerical Simulation Of AMB Rotor Drop

Swanson, E.E., Raju, K.V.S., Kirk, R.G., 1996
Proc. 6th Int’l Conf. on Vibrations in Rotating Mach., IMechE, pp. 119-131

Abstract

Active magnetic bearings (AMB) for use in land based turbomachinery has enjoyed substantial growth during the past decade. Their advantages to many applications make them an attractive solution for potentially low loss and efficient support of both radial and thrust loads. New machinery must be shop tested prior to shipment to the field for installation on-line. One necessary test is the satisfactory performance of the emergency overload backup bearings. A major concern treated by this paper is the verification of the calculation of the transient response during rotor drop and estimation of the contact forces on the radial backup bearings. The calculation technique is reviewed and results of transient response evaluation of a fill-size test rotor are compared to the reported test experimental drops. Recommendations will be given to improve the probability of stable operation during rotor drop on the test stand and in the field operating condition.

Evaluation Of AMB Turbomachinery Auxiliary Bearings

Kirk, R.G., Raju, K.V.S., Swanson, E.E., 1996
Proc Fifth Colloquium on Turbomachinery, Turbo and Power Machinery Research Center, Seoul National University, Seoul, Korea, May 6-11.

Abstract

The use of active magnetic bearings (AMB) for turbomachinery has experienced substantial growth during the past two decades. The advantages for many applications make AMBs a very attractive solution for potentially low loss and efficient support for both radial and thrust loads. New machinery must be shop tested prior to shipment to the field for installation on-line. For AMB turbomachinery, one additional test is the operation of the auxiliary drop or overload bearings. A major concern is the ability of the selected auxiliary bearing to withstand the contact forces following an at-speed rotor drop. The proper design of AMB machinery requires the calculation of the anticipated loading for the auxiliary bearings. Analytical techniques to predict the rotor transient response are reviewed. Results of transient response evaluation of a full-size compressor rotor are presented to illustrate some of the important parameters in the design for rotor drop. In addition, selected results for two test rotors used for research and development at the Virginia Tech Rotor Dynamics Laboratory are discussed.

Simulation Of AMB Turbomachinery For Transient Loading Conditions

Raju, K.V.S., Ramesh, K., Swanson, E.E., Kirk, R.G., 1995
Proc. MAG ’95, pp. 227-235.

Abstract

The increasing number of critical path machinery applications using active magnetic bearing (AMB) technology has focused awareness on the necessity for proper design of the auxiliary (backup) bearings.  These emergency bearings are required to support the rotor in the event of control system failure or to provide for operation during momentary overload conditions with the AMB control system still active.  Full-scale testing of production machinery has demonstrated both successful rotor drops as well as limited cases of auxiliary bearing failure.  The reliability required for critical path machinery makes it essential to completely understand what parameters control the nature of the rotor drop transients.  The current research project is intended to help understand the dynamic behavior of the rotor/bearing/support systems in the case of total loss of AMB support. This work presents test results for the initial rotor drop transient for several backup bearing configurations.  The cases reported are: rigidly mounted antifriction bearing, rigidly mounted solid bushings (lubricated and unlubricated), and two soft mounted solid bushing configurations.

Experimental Temperature And Pressure Profiles For Two Steadily Loaded Journal Bearings

Swanson, E.E., Kirk, R.G., 1995
Tribology Transactions, 38, pp. 601-606.

Abstract

Experimental temperature and pressure profiles for a steel and a bronze bearing are examined.  The comparisons show systematic differences between these otherwise identical bearings.  These comparisons suggest that there would be merit in including thermal deformation in the analysis if high accuracy is required.  The additional accuracy obtained could be especially important in accurately predicting the characteristics of sensitive high performance turbomachinery.

AMB Rotor Drop Initial Transient On Ball And Solid Bearings

Swanson, E.E., Kirk, R.G., 1995
Proc. MAG ’95, pp. 227-235.

Abstract

The increasing number of critical path machinery applications using active magnetic bearing (AMB) technology has focused awareness on the necessity for proper design of the auxiliary (backup) bearings.  These emergency bearings are required to support the rotor in the event of control system failure or to provide for operation during momentary overload conditions with the AMB control system still active.  Full-scale testing of production machinery has demonstrated both successful rotor drops as well as limited cases of auxiliary bearing failure.  The reliability required for critical path machinery makes it essential to completely understand what parameters control the nature of the rotor drop transients.  The current research project is intended to help understand the dynamic behavior of the rotor/bearing/support systems in the case of total loss of AMB support. This work presents test results for the initial rotor drop transient for several backup bearing configurations.  The cases reported are: rigidly mounted antifriction bearing, rigidly mounted solid bushings (lubricated and unlubricated), and two soft mounted solid bushing configurations.

Rotor Drop Test Stand For AMB Rotating Machinery, Part I: Description Of Test Stand And Initial Results

Kirk, R.G., Swanson, E.E., Kavarana, F.H., Wang, X., 1994
Proc. of Fourth International Symposium on Magnetic Bearings, Zurich, pp. 207-212.

Abstract

The recent increase in the number of critical path rotating machinery applications using active magnetic bearing (AMB) technology has focused awareness and necessity for proper design of the auxiliary or backup bearings. These emergency bearings are essential for protection of the AMB stator in the event of control system failure or limited operation during momentary overload conditions wherein the AMB control system is still active. The current research project is concerned with the former design requirement, which is referred to as rotor drop. The rotor system and the auxiliary bearing support structure are equally important and influence the nature of the resulting rotor drop transient response. Limited testing of production machinery has demonstrated both successful drop tests and limited cases of auxiliary bearing failure. The reliability required for critical path machinery makes it essential to completely understand what parameters control the nature of the rotor drop transients. The design and construction of a full scale research test stand at Virginia Tech will be documented in this paper. The overall goals are summarized and initial test results of rotor drops on the rigidly supported auxiliary bearings are presented.

An Experimental Comparison Of Two Steadily Loaded Plain Journal Bearings

Swanson, E.E., Kirk, R.G., 1994
Tribology Transactions, 37, pp. 843-849.

Abstract

A potentially powerful effect on the characteristics of plain journal bearings is local thermal deformation of the bearing surface.  Although there are a few analyses that consider the effect, it is ignored by most journal bearing codes used by industry.  There is also almost no experimental data in the literature that focuses on this effect.  To generate such data, two “”identical,”” 101 mm dia., 57 mm long bearings – one fabricated from steel and one from bronze – have been tested in a precision journal bearing test rig.  Comparisons between shaft displacement data for steady loading of the two bearings show that the deformations are important to consider.

Experimental Evaluation Of Fluid-Film Bearings Using Electro-Magnetic Shaft Loading And Evidence Of Localized Thermal Distortion

Swanson, E.E., Kirk, R.G., 1992
Proc. 5th Int’l Conf. on Vibrations in Rotating Mach., IMechE, pp. 359-363.

Abstract

During the preliminary operational verification of a new test rig, a possible source of some of the discrepancy between analytical and experimental results for fluid film bearings, which has not been considered at great length in the literature, was noted. This mechanism is the localized thermal deformation of the bearing bush. To qualitatively demonstrate that such a mechanism may change the static shaft locus for a bearing, results from the VPI & SU test rig and a published work are presented.

An Examination And Comparison Of The Maximum Film Temperatures In A Journal Bearing For 13 Synthetic, Mineral And Viscosity Index Enhanced Oils

Swanson, E.E., Kirk, R.G., Mondy, R.E., 1992
Rheology and Tribology of Engine Oils, SAE SP-936, Society of Automotive Engineers, Warrendale, pp. 137-145.

Abstract

An experimental investigation of the peak film temperatures for 13 different oils has been performed with a precision journal bearing test rig. This study examined the differences between mineral, synthetic and viscosity index enhanced oils with regards to peak oil film temperatures. The oils examined include: three mineral oils (1-ISO 68 and 2-ISO 32), eight synthetic oils (1-ISO 22, 6-ISO 32, 1-ISO 68) and two viscosity index enhanced oils (1-ISO 22 synthetic, 1-ISO 32 mineral). The synthetic oils included both Diester base and Polyalphaolefin base products. Data for each oil were obtained at 6000, 8000, 10800, 12000, and 14000 RPM (100, 133, 180, 200 and 233 Hz); for loads of 670, 1330, 2000, 2670 and 3340 N. These speeds and loads correspond to surface speeds between 16 m/s to 37 m/s and unit loading between 0.5 MPa and 2.6 MPa. A 50.8 mm diameter, 25.4 mm long bearing with the upper portion relieved was used for all tests.

The data obtained tend to confirm the initial expectation that the bulk fluid characteristics are much more important than the lubricant composition with regards to static performance characteristics (i.e., load capacity and peak film temperature) in the thick film operating regime characteristic of a moderately loaded journal bearing. The results showed a 5 to 10 ?C decrease in peak film temperature can be obtained by changing from an ISO 68 to an ISO 32 oil. It was also found that viscosity index enhancers can allow a relatively inexpensive mineral base oil to show the same general level of thermal performance as a synthetic oil. The reduction in peak temperatures was seen in both an enhanced ISO 32 mineral base oil and an enhanced ISO 22 synthetic base oil. These observations suggest that the effect of shear thinning on polymer thickened oils may not be as great as the published analytical investigations would suggest. The reductions in temperature observed should also be of interest with regards to thrust bearings which often experience severe thermal crowning.