VIBRATION-MONITORING SYSTEMS

• US 3,641,550 A
• Filed: 02/25/1970
• Issued: 02/08/1972
• Est. Priority Date: 03/05/1969
• Status: Expired due to Term

• Current Assignee: Derek L. Lynas, Walter G. Cross
• Original Assignee: Derek L. Lynas, Walter G. Cross
• Inventors: Lynas, Derek L., Cross, Walter G.
• Primary Examiner(s): Caldwell, John W.
• Assistant Examiner(s): Slobasky, Michael
• Application Number:
  US05/013,940
• Time in Patent Office: 713 Days
• Field of Search: 340/261 73/67.2,116
• US Class Current: 73/583
• CPC Class Codes: G01H 1/003 of rotating machines G01H1/10 takes precedence

Abstract

A vibration-monitoring system for use with a three-shaft gas turbine engine. Vibration from the engine is picked up by two electrical transducers and transmitted to a filter network. The filters produce three electrical outputs in three separate frequency bands, each of which corresponds to the frequency band of the vibration produced by a respective one of the shafts. The vibration produced by each shaft can thus be separately indicated.

Claims

1. A multishaft gas turbine engine shaft vibration-monitoring system comprising:

two vibration-responsive devices, means mounting said two vibration-responsive devices on said gas turbine engine in spaced-apart relationship, said vibration-responsive devices each being disposed for producing an electrical signal having frequency and amplitude respectively dependent upon the frequency and amplitude of the vibrations being monitored, means for receiving both said electrical signals and producing a single first signal representing both said electrical signals, first filter means connected to receive said first signal for passing a second signal comprising those components of the first signal lying within a predetermined broad frequency band, a plurality of second filter means, the number of second filter means being equal to the number of shafts in said engine, each of said second filter means being effective for receiving said second signal and producing a third signal therefrom comprising those components of the second signal lying within a predetermined narrow frequency band, the narrow frequency bands associated with the second filter means being in nonoverlapping relationship, warning means associated with said first filter means for operation when the magnitude of said second signal exceeds a predeTermined value, indicator means and selector means for selectively connecting said second signal and each of said third signals to said indicator means whereby the magnitude of vibration in said broad frequency band and in each said narrow frequency band may be selectively indicated.

2. A multishaft gas turbine engine shaft vibration monitoring system as in claim 1 wherein the first filter means comprises a first band-pass filter which is connected to receive the first signal and which has upper and lower 3 db. frequencies which are substantially equal to the highest and lowest frequencies respectively of the range of vibrations to be monitored.

3. A multishaft gas turbine engine shaft vibration monitoring system as in claim 2, wherein the plurality of second filter means comprises:

a low-pass filter, a second band-pass filter, and a high-pass filter, the respective inputs of these filters being connected to the output of the first band-pass filter and the respective outputs of which constitute the three outputs of the second filter means, whereby the lowest of the three frequency bands is defined as being between the lower 3 db. frequency of the first band-pass filter and the 3 db. frequency of the low-pass filter, the intermediate one of the three frequency bands is defined as being between the upper and lower 3 db. frequencies of the second band-pass filter, and the highest of the three frequency bands is defined as being between the 3 db. frequency of the high-pass filter and the upper 3 db. frequency of the first band-pass filter.

4. A multishaft gas turbine engine shaft vibration monitoring system as in claim 3, wherein the indicator means comprises:

rectifying means selectively connectable to the respective outputs of the first band-pass filter, the low-pass filter, the second band-pass filter and the high-pass filter, and an indicator connected to the output of the rectifying means.

5. A multishaft gas turbine engine shaft vibration-monitoring system as in claim 2, wherein a warning device is connected to the output of the first band-pass filter via further rectifying means, whereby when the signal at the output of the further rectifying means exceeds a predetermined value the warning device is operated.

6. A multishaft gas turbine engine shaft vibration-monitoring system as claimed in claim 5, wherein the warning device includes means for producing a visible warning.

7. A multishaft gas turbine engine shaft vibration-monitoring system as in claim 1, wherein each vibration-responsive device comprises an accelerometer device.

8. A multishaft gas turbine engine shaft vibration-monitoring system as in claim 7, wherein each accelerometer device is a piezoelectric crystal device.

9. A multishaft gas turbine engine shaft vibration-monitoring system as in claim 7, wherein the outputs of the two accelerometer devices are connected to the first filter means via a two-state switching device having two inputs, a single output and means for selectively connecting either of the inputs to the output.

10. A multishaft gas turbine engine shaft vibration-monitoring system as in claim 9, wherein the switching device is provided with switch driving means for driving it between its two states at a predetermined frequency.