Development of large-scale journal bearing test setup

DEVELOPMENT OF LARGE-SCALE RADIAL BEARING TEST SETUP Á. Kalácska 1, K. Van Minnebruggen1, K. Van Hoey 2, T. Depraetere 2, P. De Baets 1 1Soete Laboratory, Department of Electromechanical, Systems and Metal Engineering, Ghent University, Belgium. 2Ghent University, Belgium. Context References: [1] –https://acteon.com/blog/floating-wind-mooring-options/ [2] –https://www.balltec.com/solutions/balltec-mooring-solutions-tools/6-moorlok/ [3] –https://www.nordenmaritim.no/--materials.html#788 [4] - https://www.oilesglobal.com/eu/en/ Acknowledgement: Sam Demeester, Jonathan Vancoillie and Wouter Ost for assembly/design inputs Fig. 1 –Mooring lines, seabed anchor of offshore wind turbines and used journal bearing [1-3] Contact in/ádám-kalácska-865b7226b/ Adam.K[email protected] Roller bearings < Large-scale journal bearings + Seawater environment + No lubrication possible (environment) + Oscillating motion due to waves, currents + Maintenance-free + High loadlow velocity characteristics –Higher CoF (sliding instead of rolling) ➢Tribological characteristics to be investigated Test set-up Objective: Measure the evolution of the coefficient of friction (CoF) and wear of the bearing in time Seabed anchor Bearing Due to the complex interactions, (running-in/out, sliding layer formation, size effect, roughness changes, ...) large-scale tests are needed to accurately describe real-life behaviour as well as possible •Rising demand for green energy •Offshore wind turbines: stronger wind, lower cost •Securing floating platforms, mooring lines: self-lubricating journal bearings Fig. 2 –Different self-lubricating bearings [4] Showcase results Fig. 4 –Working principle of the test setup and cross-section of the housing Fig. 3 –Overview of the developed Large-Scale Bearing test rig and 3D model of the setup without frame highlighting its main parts Radial force piston Load cell (radial force) Transmission trolley Test bearing Bearing housing Shaft (wear sleeve on) Support bearings Displacement piston Load cell (applied load) Displacement lever arm (applied side) Torque arm top bearing house (resulting load side) Load cell (resulting load) Design parameter Unit Value Max radial force [kN] 2250 Max CoF [-] 0.4 Bearing øinner [mm] 260-400 Bearing øouter [mm] ≤500 Bearing width [mm] ≤300 Max shaft rotation [°] 20 Counterface material / Stainless steel Working temperature min-max [°C] -20, +75 Tab. 1 –Design parameters of the setup •CoF value different for clockwise and counterclockwise rotation of the shaft in the bearing (CoF asymmetry) •Rolling -> sliding transition •Dynamic CoF the average value of friction during the middle 33% of each stroke, the average of the forward and backward stroke within each cycle •Static CoF the maximum value of friction during the first 25% of each stroke, the average of the forward and backward stroke within each cycle Fig. 5 –Example of a test cycle and resulted static and dynamic CoF CoF, Wear rate influenced by: •Contact pressure (higher load -> lower CoF) •Temperature •Seawater environment (lower CoF) •Test scale (edge effect) •Velocity (higher velocity -> higher CoF) •Shaft motion •Clearance between shaft (wear sleeve) and bearing CoF, calculation methods: Based on force/torque equilibrium around the center of the shaft •’direct’ method, using the bearing housing torque to determine the COF, •’indirect’ method, using the shaft’s frictional moment, including the support bearings The basic working principle of the test rig: A shrink disc secures the lever arm (6), which transfers the displacement piston’s motion (5) to the shaft (3). During the test, the displacement of both pistons (5 and 8), the radial load (10), the load applied on the movement lever arm (7), and the resulted torque load (12) is measured. Instrumentation: •Rotation sensors on both side of the shafts •Displacement laser sensors to measure to movement of the shaft with respect to the test bearing (bearing wear) •Thermocouples in the bearing, shaft Fig. 6 –Example of CoF and temperature evolution Displacement cylinder end position Shaft end position Shaft speed 0 Shaft speed max Shaft mid position Displacement cylinder mid position Segment forward Maximum of first 25% to identify static CoF Segment backward ± 16.5% around midpoint (red square) for dynamic CoF Displacement cylinder end position Shaft end position Shaft speed 0 Cycle buildup 0.10 0.15 0.20 0.25 10 0 20 30 40 50 60 70