Experimental Estimation of Journal Bearing Stiffness for Damage Detection in Large Hydrogenerators

Table 1

Main data of the generator upper (UJB), generator lower (LJB), and turbine (TJB) journal bearings.

Description	Unit	UJB	LJB	TJB
Number of pads	—	16	16	12
Journal radius	mm	1100	2600	1600
Bearing pad radius	mm	1103	2604	1633
Journal speed	m/s	10.6	25.1	15.5
Assembled pad clearance at standstill	µm	500	950	200
Assembled pad clearance in operation	µm	200	300	200
Bearing preload	—	0.933	0.925	0.994
Pad pivoting system	—	Similar to rocker-pivot type
Distance trailing edge-pivot	mm	140	248	250
Pad length	mm	350	620	500
Pad width	mm	400	310	500
Pad mass	kg	172	290	390
Bearing direct stiffness (average)	GN/m	6.70	2.85	6.70
Bearing global stiffness	GN/m	0.80	1.25	1.45
Lubricant type		Lubrax Turbina Plus 50
Lubricant viscosity at 40°C	Pas	0.047	0.047	0.047
Lubricant viscosity at 100°C	Pas	0.0068	0.0068	0.0068
Lubricant density at 20°C	kg/m^3	873	873	873
Lubricant temperature range	°C	40–55	40–55	40–50