Method and device for monitoring a journal bearing

1. A method for monitoring at least one journal bearing for a shaft in respect to at least one acoustic event in the at least one journal bearing, comprising:

providing a gas turbine engine for an aircraft comprising:

an engine core comprising a turbine, a compressor, and a core shaft connecting the turbine to the compressor;

a fan located upstream of the engine core, the fan comprising a plurality of fan blades;

a gearbox that receives an input from the core shaft and outputs drive to the fan so as to drive the fan at a lower rotational speed than the core shaft,

the gearbox including the at least one journal bearing and a further shaft, the at least one journal bearing rotationally supported on the further shaft;

a) detecting a time dependent solid borne sound signal, emitted by the at least one journal bearing, with at least one solid borne sound signal sensor, the time dependent solid borne sound signal being representative of the at least one acoustic event, the at least one acoustic event created by relative rotation between the further shaft and the at least one journal bearing;

b) transmitting the output signal of the at least one solid borne sound signal sensor to a signal pre-processing device,

c) amplifying frequency components of the solid borne sound signal having only a frequency between 200 kHz and 1 MHz in the signal pre-processing device; and subsequently

d) wirelessly transmitting the output signal of the signal pre-processing device via an antenna device to a signal evaluation device for detecting and/or locating of the at least one acoustic event, and demodulating the output signal of the signal pre-processing device with the signal evaluation device to detect the at least one acoustic event, localize the at least one acoustic event and/or detect a wear status of the at least one journal bearing.

2. The method of claim 1 , and further comprising transmitting the output of the at least one solid borne sound signal sensor over a wire and/or wirelessly to the signal pre-processing device.

3. The method of claim 1 , and further comprising encoding the output signal of the signal pre-processing device as a homodyne signal.

4. The method of claim 1 , and further comprising providing that the at least one journal bearing is part of an epicyclic gearbox of a geared turbofan engine.

5. The method of claim 4 , and further comprising monitoring all planet gears of the epicyclic gearbox with respect to the at least one acoustic event.

6. The method of claim 4 , and further comprising providing that the antenna device is at least in part coupled to a rotating part connected to the gearbox.

7. The method of claim 6 , and further providing that the antenna device includes a rotating antenna element connected to a rotating part of the gearbox and operatively connected to a static antenna element connected to a static part of the geared turbofan engine.

8. The method of claim 1 , wherein the at least one acoustic event is generated by 1) Changes between different friction modes between the at least one journal bearing and the further shaft and/or 2) damages or wear marks in one or both of the at least one journal bearing and the further shaft.

9. A system for monitoring at least one journal bearing for a shaft in respect to at least one acoustic event in the at least one journal bearing, comprising:

a gas turbine engine for an aircraft comprising:

an engine core comprising a turbine, a compressor, and a core shaft connecting the turbine to the compressor;

a fan located upstream of the engine core, the fan comprising a plurality of fan blades;

a gearbox that receives an input from the core shaft and outputs drive to the fan so as to drive the fan at a lower rotational speed than the core shaft,

the gearbox including the at least one journal bearing and a further shaft, the at least one journal bearing rotationally supported on the further shaft;

at least one solid borne sound signal sensor configured for detecting a time dependent solid borne sound signal emitted by the at least one journal bearing, the time dependent solid borne sound signal being representative of the at least one acoustic event, the at least one acoustic event created by relative rotation between the further shaft and the at least one journal bearing;

a signal pre-processing device configured for pre-processing the at least one solid borne sound signal received from the at least one solid borne signal sensor,

an amplifier device configured for amplifying frequency components of the solid borne sound signal having only a frequency between 200 kHz and 1 MHz,

a wireless transmitter comprising an antenna device configured for outputting a signal of the signal pre-processing device, and

a signal evaluation device configured for wirelessly receiving the output signal of the signal pre-processing device, the signal evaluation device comprising a detection device and/or a location device for the at least one acoustic event, wherein the signal evaluation device is configured to demodulate the output signal of the signal pre-processing device for detecting the at least one acoustic event, localizing the at least one acoustic event and/or detecting a wear status of the at least one journal bearing.

10. The system according to claim 9 , wherein the at least one solid borne sound signal sensor is a piezoelectric element, coupled to the at least one journal bearing with a glue connection.

11. The system according to claim 9 , wherein the antenna device includes a rotating antenna element, connected to a rotating part of the gearbox and configured as a wireless sender and a static antenna element connected to a static part, a static part of the gearbox and configured as a wireless receiver.

12. The system according to claim 9 , wherein

the turbine is a first turbine, the compressor is a first compressor, and the core shaft is a first core shaft;

the engine core further comprises a second turbine, a second compressor, and a second core shaft connecting the second turbine to the second compressor; and

the second turbine, second compressor, and second core shaft are arranged to rotate at a higher rotational speed than the first core shaft.