METHOD AND SYSTEM FOR MONITORING A TURBOJET ENGINE

• US 20110178772A1
• Filed: 10/09/2009
• Published: 07/21/2011
• Est. Priority Date: 10/10/2008
• Status: Active Grant

• Current Assignee: Safran Aircraft Engine Company
• Original Assignee: Snecma (Safran SA)
• Inventors: Guillemand, Gregory, Griffaton, Julien, Gerez, Valerio
• Granted Patent: US 8,560,272 B2
• Time in Patent Office: Days
• US Class Current: 702/184
• CPC Class Codes: F01D 21/003 Arrangements for testing or measuring for measuring vibrations G01H
• CPC Class Codes: F01D 21/04 responsive to undesired position of rotor relative to stator or to breaking-off of a part of the rotor, e.g. indicating such position
• CPC Class Codes: F05D 2260/80 Diagnostics
• CPC Class Codes: F05D 2260/96 Preventing, counteracting or reducing vibration or noise
• CPC Class Codes: F05D 2270/09 to cope with emergencies
• CPC Class Codes: F05D 2270/304 Spool rotational speed
• CPC Class Codes: G01H 1/006 of the rotor of turbo machines
• CPC Class Codes: Y02T 50/60 Efficient propulsion technologies, e.g. for aircraft

Abstract

A method and a system for monitoring a turbojet engine. The method acquires a signal representative of a vibratory level of an operating rotor of the turbojet engine, acquires a rotation speed of the rotor during operation, compares the amplitude of the signal with at least one predetermined threshold based on the rotor rotation speed and, in event an amplitude peak exceeds the threshold, analyzes the signal over a time slot defined around the amplitude peak to determine if the phenomenon at the origin of the amplitude peak is a mechanical shock undergone by the rotor of the turbojet engine or an electronic interference of the signal.

Claims

1-10. -10. (canceled)

11. A method of monitoring a turbojet, the method comprising:

acquiring a signal representative of a vibratory level of a rotor during operation of the turbojet;

acquiring a speed of rotation of the rotor in operation;

comparing an amplitude of the signal with at least one vibratory threshold that is predetermined as a function of the speed of rotation of the rotor; and

in event of the threshold being crossed by an amplitude peak, analyzing the signal over a defined time window on either side of the amplitude peak to determine whether a phenomenon giving rise to the amplitude peak is a mechanical impact against the turbojet rotor or an electronic disturbance of the signal.

12. A method according to claim 11, wherein the analyzing the signal over the time window comprises analyzing symmetry of the signal.

13. A method according to claim 11, wherein the analyzing the signal over the time window comprises modeling a decrease in the signal after the amplitude peak.

14. A method according to claim 13, wherein the analyzing the signal over the time window comprises calculating a difference between a curve plotting averages of amplitudes of a spectrogram of the signal at each instant over the time window, with an exponential model of that curve.

15. A method according to claim 11, wherein the predetermined vibration threshold comprises high and low values for the signal over different ranges of rotor rotation speed.

16. A method according to claim 11, further comprising, after determining that there has been a mechanical impact against the rotor of the turbojet, determining whether an unbalance has appeared in the rotor following the mechanical impact.

17. A method according to claim 16, wherein the determining that an unbalance has appeared in the rotor comprises:

making a spectrogram of the signal over a time window;

calculating an average of amplitudes of the spectrogram at each instant;

calculating a difference in levels of the average before and after the amplitude peak; and

comparing the difference in level with a predetermined level threshold.

18. A method according to claim 11, wherein the acquiring the signal and the acquiring the speed of rotation of the rotor are performed continuously during an operating cycle of the turbojet.

19. A method according to claim 11, wherein the acquiring the signal, the acquiring the speed of rotation of the rotor, and the comparing the amplitude of the signal are performed in real time, while the analyzing the signal is performed in deferred time.

20. A method according to claim 11, further comprising issuing a maintenance message if it is determined that the phenomenon giving rise to the vibratory event is a mechanical impact against the rotor of the turbojet.