Title: Ultrasonic Reflections from the Multi-Axis bearing in the Full-Scale Wind turbine Bearing Test Rig
Instituation: The University of Sheffield, UK
Date of Collection: 12/08/2021 - 20/08/2021
Keywords: Bearing, meniscus, oil lubrication, grease lubrication
Rig: Multilife - owned by Riccardo

Overview:

This test data was captured on the multi-axis bearing, installed in the full-scale wind turbine bearing test rig, and has test data for the bearing lubricated with Hyspin VG 32 oil , Alpha SP 320 oil and Mobil SHC 460 WT grease.

The bearing inner raceway has two rows (longitudinal and shear) of ultrasonic sensors mounted on the inner face. When excited these sensors send ultrasonic waves through the raceway which reflect from the inner raceway-roller contact face. A bearing carrier supports the instrumented inner raceway which is in turn shaft mounted. This inner raceway then remains stationary during the test and the outer raceway is belt driven at 5 different speeds of 20, 40, 60, 80, 100rpm.

For oil tests an oil pump and scavenger pump worked to constantly circulate oil. For the grease tests the pump was removed and 1/3 of the bearing volume was packed. The packing method was to give an advantageous spread of grease to the bearing for optimum lubrication.

The recordings are of these raw reflections. The data was capturered using the Film Measurement System from Tribosonics Ltd. For grease tests (460WT) chnannel 1 is linked to the left side of the bearing, and channel 7 to the right.
For both oil tests the same sensors were used butchannel 1 is linked to the right side of the bearing to channel 7 which is at the left side of the bearing. This needs to be taken into account when analysing data.

After the VG 32 test the rig sumps and hoses were opened and the oil was allowed to drain from the rig. A rinse fluid was deemed unecessary as VG32 is very low viscosity and drains easily, and VG320 is so much more viscous and pumped in such quantaties that and residual VG32 was assumed to have a negligable effect.

Notes on data:

Temperature for oil tests:
Pos 124 = thermocouple 1 - inner raceway ext to sensor location
Pos 85 = thermocouple 2 - in-situ in the oil line
Pos 34 = thermouple 3 - attached to outer bearing case

Temperature for oil grease:
Pos 124 = thermocouple 1 - inner raceway ext to sensor location
Pos 85 = thermocouple 2 - attached to outer bearing case

For oil tests, three 10s captures were taken. Then end of the file name refers to the test number. For example, 20210812_Multilifetest_0200kN_080RPM_VG32_t2 is the VG32 oil testsed under 200kN of total radial load, with the outer raceway spinning at 80rpm, and is the second capture.

For grease tests, the grease churning phase was of particular interest and so 5 brake in steps were identified for the 5 rig speeds of 20, 40, 60, 80, 100rpm. At each speed the bearing was loaded and rotated, and the inner raceway thermocouple was used to monitor the grease. When there was a period of 10 minutes witha temperature gradient <1C the grease was deemed to be broken-in at that particular rpm.

Units:
In the file, there are unit themes throughout:
-pulse rate (Hz)
-temperature (Celcius)
-range and delay (microseconds)
-reflection units (millivolt)
-Filter (mode 6, centred around 10MHz, gave largest amplitude response)