Measurements to Quantify the Effect of a Reduced Flow Rate on the Performance of a Tilting Pad Journal Bearing With Flooded Ends

Author:

San Andrés Luis1,Toner Jonathan1,Alcantar Andy1

Affiliation:

1. J. Mike Walker '66 Mechanical Engineering Department, The Turbomachinery Laboratory, Texas A&M University, College Station, TX 77843

Abstract

Abstract Operation of tilting pad journal bearings (TPJBs) with a reduced flow decreases pumping costs and oil sump storage. A low supplied oil flow improves system energy efficiency by reducing drag power losses, albeit the temperature rise in both the bearing pads and the lubricating oil become a concern. This paper presents measurements of the static and dynamic load performance of a flooded ends TPJB lubricated with an ISO VG 46 oil supplied at 60 °C, and with a flow rate ranging from 150% to just ∼5% of a nominal supply condition. The flow range covers both over-flooded and starved flow conditions. The test bearing is a four-pad, 102 mm diameter, center pivot, with single orifice feeds, and configured with end seals to flood the bearing housing. The experiments include operation at two shaft speeds = 6 krpm and 12 krpm (= 64 m/s surface speed) and under three specific loads = 0.345 MPa, 1.03 MPa, and 2.07 MPa applied in between pads (LBP). The measurements show the bearing drag power loss decreases by nearly 20% when the flow rate drops to 50% of nominal. However, halving the flow produces a raise in pad subsurface temperatures, ∼7 °C for operation at 12 krpm. Flow reduction below 50% does result in even more substantial power savings; however, it also produces too hot pad temperatures that approach 130 °C, a known limit for Babbitt material safe operation. The bearing static eccentricity (e) and direct stiffnesses Kxx < Kyy (load direction) do not show a significant dependency on the supplied flow, either above or below the nominal condition. A minor stiffness hardening does occur for very low flow conditions, 5% or so of nominal. Damping coefficients (Cxx ∼ Cyy) decrease by ∼30% as the flow rate decreases from 150% to just a few % of the nominal flow. The experimental results are first to quantify the operation of a TPJB supplied with minute amounts of lubricant flow. A test with a very low flow rate at ∼2% of nominal and under a light load produced the emergence of a broadband subsynchronous vibration (SSV) frequency, albeit with a very small amplitude.

Publisher

ASME International

Subject

Mechanical Engineering,Energy Engineering and Power Technology,Aerospace Engineering,Fuel Technology,Nuclear Energy and Engineering

Reference16 articles.

1. Tilting Pad Bearings-Limits of Operation;ASLE Lubr. Eng.,1976

2. A Study of Parameters That Affect Pivoted Shoe Journal Bearing Performance in High-Speed Turbomachinery,2001

3. Effect of Oil Evacuation on the Static and Dynamic Properties of Tilting Pad Journal Bearings;Trib. Trans.,2006

4. Effect of Load Direction, Preload, Clearance Ratio, and Oil Flow on the Performance of a 200 mm Journal Pad Bearing;Trib. Trans.,1994

5. Nichols, B., 2017, “ Experimental Measurements and Modeling of Tilting-Pad Bearing Performance and System Stability Under Reduced Oil Supply Flow Rates,” Ph.D. dissertation, University of Virginia, Charlottesville, VA.https://libra2.lib.virginia.edu/downloads/5d86p056z?filename=1_Nichols_Bradley_2017_P HD.pdf

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