U.S. patent application number 12/844240 was filed with the patent office on 2010-11-18 for measuring rotor imbalance via blade clearance sensors.
Invention is credited to Eric B. Holmquist.
Application Number | 20100288045 12/844240 |
Document ID | / |
Family ID | 40019523 |
Filed Date | 2010-11-18 |
United States Patent
Application |
20100288045 |
Kind Code |
A1 |
Holmquist; Eric B. |
November 18, 2010 |
MEASURING ROTOR IMBALANCE VIA BLADE CLEARANCE SENSORS
Abstract
A system and method can be utilized to determine an out of
balance condition of a rotor having a plurality of blades. The
system monitors a clearance between the blades and an associated
housing. By looking at a center of that clearance information, a
determination can be made of the magnitude of imbalance of the
rotor.
Inventors: |
Holmquist; Eric B.; (South
Windsor, CT) |
Correspondence
Address: |
CARLSON, GASKEY & OLDS, P.C.
400 WEST MAPLE ROAD, SUITE 350
BIRMINGHAM
MI
48009
US
|
Family ID: |
40019523 |
Appl. No.: |
12/844240 |
Filed: |
July 27, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11866652 |
Oct 3, 2007 |
7775107 |
|
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12844240 |
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Current U.S.
Class: |
73/455 |
Current CPC
Class: |
G01M 1/28 20130101; G01M
15/14 20130101 |
Class at
Publication: |
73/455 |
International
Class: |
G01M 1/00 20060101
G01M001/00 |
Claims
1. A system for identifying an out of balance rotor comprising: a
sensor for sensing a clearance between a plurality of blades and a
housing surface, clearance information from said sensor being
delivered to a control; and said control being operable to receive
said clearance information, and determine a center of the clearance
information, and compare the distance between an actual center of
the clearance information, and an expected center of the clearance
information should there be no imbalance, said distance being taken
as a magnitude of imbalance of the rotor.
2. The system as set forth in claim 1, wherein said sensor sends a
microwave signal, and receives and analyzes a reflected microwave
signal.
3. The system as set forth in claim 1, wherein a plurality of
revolutions of the rotor are taken as said clearance
information.
4. The system as set forth in claim 1, wherein said rotor imbalance
is determined in real time.
5. The system as set forth in claim 1, wherein the location of the
actual center of the clearance information is used to determine the
location of the imbalance.
6. The system as set forth in claim 1, wherein said system is
mounted on a gas turbine engine.
7. A method for identifying an out of balance rotor comprising:
gathering clearance information of the clearance between a
plurality of blades and a housing surface; and determining a center
of the clearance information, and comparing a distance between an
actual center of the clearance information, and an expected center
of the clearance information should there be no imbalance, said
distance being taken as a magnitude of imbalance of the rotor.
8. The method as set forth in claim 7, wherein said sensor sends a
microwave signal, and receives and analyzes a reflected microwave
signal.
9. The method as set forth in claim 7, wherein a plurality of
revolutions of the rotor are taken as said clearance
information.
10. The method as set forth in claim 7, wherein said rotor
imbalance is determined in real time.
11. The method as set forth in claim 7, wherein the location of the
actual center of the clearance information is used to determine the
location of the imbalance.
12. A gas turbine engine comprising: at least one rotor having a
plurality of blades, the blades rotating spaced from a housing
surface; a sensor for sensing a clearance between the plurality of
blades and the housing surface, clearance information from said
sensor being delivered to a control; and said control being
operable to receive said clearance information, and determine a
center of the clearance information, and compare the distance
between an actual center of the clearance information, and an
expected center of the clearance information should there be no
imbalance, said distance being taken as a magnitude of imbalance of
the rotor.
13. The engine as set forth in claim 12, wherein said sensor sends
a microwave signal, and receives and analyzes a reflected microwave
signal.
14. The engine as set forth in claim 12, wherein a plurality of
revolutions of the rotor are taken as said clearance
information.
15. The engine as set forth in claim 12, wherein said rotor
imbalance determination is determined in real time.
16. The engine as set forth in claim 12, wherein the location of
the actual center of the clearance information is used to determine
the location of the imbalance.
Description
RELATED APPLICATION
[0001] This application is a continuation of U.S. patent
application Ser. No. 11/866,652, which was filed Oct. 3, 2007.
BACKGROUND OF THE INVENTION
[0002] This application relates to a system which utilizes blade
clearance information to identify the magnitude and location of a
rotor imbalance.
[0003] Gas turbine engines include a plurality of sections mounted
in series. Typically, a fan may deliver air into a compressor
section. The air is compressed and delivered downstream into a
combustion chamber where it is mixed with fuel and combusted.
Products of that combustion pass downstream over turbine
rotors.
[0004] The fan, the compressor, and the turbines all include rotors
with attached blades.
[0005] It is known to monitor the tip clearance of at least some of
the blades of these rotors. Such monitoring may be utilized to
determine potential problems with the rotors or the blades. It is
known to utilize microwave signals, and monitor a reflected signal
to identify a tip clearance.
[0006] One other feature that is often monitored with regard to
such rotors is rotor imbalance. If the rotors are out of balance,
severe vibration can occur, which is undesirable. To date, engine
rotor balance technology has required special test instrumentation
or ground support equipment. Installing this instrumentation is
time consuming, and requires the engine to be out of service for a
period of time. The ground support equipment is limited, and there
is often a wait to obtain this equipment.
SUMMARY OF THE INVENTION
[0007] In the disclosed embodiment of this invention, the results
from a blade clearance sensor are utilized to identify the
magnitude of imbalance of a rotor. The same information can be
utilized to determine the location of the imbalance.
[0008] These and other features of the present invention can be
best understood from the following specification and drawings, the
following of which is a brief description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a schematic view of a gas turbine engine.
[0010] FIG. 2 is a system for identifying an imbalance with regard
to a rotor in the FIG. 1 system.
[0011] FIG. 3 is a sample result for performing the method of this
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0012] FIG. 1 illustrates selected portions of an example gas
turbine engine 10, such as a turbofan gas turbine engine used for
propulsion. In this example, the turbine engine 10 is
circumferentially disposed about an engine centerline 12. The
turbine engine 10 includes a fan 14, a compressor section 16, a
combustion section 18, and a turbine section 20. The combustion
section 18 and the turbine section 20 include corresponding blades
22 and vanes 24. As is known, air compressed in the compressor
section 16 is mixed with fuel and burned in the combustion section
18 to produce hot gasses that are expanded in the turbine section
20. FIG. 1 is a somewhat schematic presentation for illustrative
purposes only and is not a limitation on the disclosed examples.
Additionally, there are various types of gas turbine engines, many
of which could benefit from the examples disclosed herein and are
not limited to the designs shown.
[0013] FIG. 2 shows a system 50 for identifying an imbalance for a
rotor 52 having a plurality of blades 54 spaced from a housing 53.
While this invention may relate to any number of rotors having
blades, in particular, it is well suited for the rotors such as are
found in a gas turbine engine. A probe 56 may be utilized to
determine a clearance between the outer tip of the blades 54 and
the inner surface 53 of the housing. Such sensors are in use today,
and are known in the art.
[0014] The probe 56 may communicate with a coupler 58, and receive
microwave signals from a source 60. A detector 62 may detect a
reflected signal, and submit that detected signal to processing
electronics 64. The processing electronic 64 may also be provided
with a signal 65 indicative of the completion of a rotation cycle.
Such systems are known, and have been utilized in the past for
determining blade clearance.
[0015] The present invention is directed to utilizing the blade
clearance information to determine an imbalance of the rotor 52. As
shown in FIG. 3, a series of clearances for multiple rotation of a
rotor having 58 blades might well look like as shown at B.sub.C. As
can be appreciated, this clearance information is offset relative
to a center C.sub.1 of the rotor. The offset of the B.sub.C
information relative to the center C.sub.1, is indicative of the
rotor being out of balance.
[0016] Known processing techniques can be utilized on the B.sub.C
information. As an example, fast Fourier transforms can be
utilized, or any other way of calculating a center of the
information B.sub.C can be utilized. The center of that information
is shown at C.sub.A. This is the apparent center, due to the
imbalance. In essence, this is the actual center which can be
compared to an expected center C.sub.1. The distance d between
C.sub.1 and C.sub.A is the magnitude of the displacement of the
center of mass, and is indicative of the magnitude of the
imbalance. An angle .theta. can be defined between any point, and a
location of C.sub.A. As shown in FIG. 3, the location of the number
one blade to the location of the apparent center C.sub.A is
utilized to determine .theta.. By determining .theta., the location
of the center of the imbalance can be determined. A worker of
ordinary skill in this art with knowledge of the apparent center
and .theta., would know how to provide a counterweight to correct
the imbalance.
[0017] Since the present invention utilizes sensor technology that
is already incorporated into gas turbine engines for other
purposes, no new instrumentation is necessary to achieve the
invention. Moreover, since this existing sensor is utilized, the
present invention can provide imbalance information in real time,
and without taking the engine out of service. As an example, if on
one flight an incident occurred that could have affected the
balance of the rotor, the electronics would have been able to
identify the change in the imbalance, and could provide a warning
to a pilot. An example display 67 may be utilized to provide such a
warning to the pilot that the rotor imbalance has exceeded a
magnitude that had been preset as a limit.
[0018] Alternatively, the system can also be utilized to provide
routine maintenance information, and the location to which a
counterweight can be attached to correct the imbalance.
[0019] Although an embodiment of this invention has been disclosed,
a worker of ordinary skill in this art would recognize that certain
modifications would come within the scope of this invention. For
that reason, the following claims should be studied to determine
the true scope and content of this invention.
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