GB2063477A - Measuring Clearance Gap Between Turbine Blades and Surrounding Duct - Google Patents
Measuring Clearance Gap Between Turbine Blades and Surrounding Duct Download PDFInfo
- Publication number
- GB2063477A GB2063477A GB7939501A GB7939501A GB2063477A GB 2063477 A GB2063477 A GB 2063477A GB 7939501 A GB7939501 A GB 7939501A GB 7939501 A GB7939501 A GB 7939501A GB 2063477 A GB2063477 A GB 2063477A
- Authority
- GB
- United Kingdom
- Prior art keywords
- turbine
- clearance gap
- electrical
- gap
- duct
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D11/00—Preventing or minimising internal leakage of working-fluid, e.g. between stages
- F01D11/08—Preventing or minimising internal leakage of working-fluid, e.g. between stages for sealing space between rotor blade tips and stator
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D21/00—Shutting-down of machines or engines, e.g. in emergency; Regulating, controlling, or safety means not otherwise provided for
- F01D21/04—Shutting-down of machines or engines, e.g. in emergency; Regulating, controlling, or safety means not otherwise provided for responsive to undesired position of rotor relative to stator or to breaking-off of a part of the rotor, e.g. indicating such position
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/14—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring distance or clearance between spaced objects or spaced apertures
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Turbine Rotor Nozzle Sealing (AREA)
- Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
Abstract
A turbine comprising a housing (6), a duct (4) in the housing (6), a plurality of rotor blades (2) which are mounted on a rotor body and which are positioned inside the duct (4), and a compressor, is provided with electrical measuring means (10, 14, 16, 18) for electrically measuring the clearance gap (G) between the duct wall (8) and the tips of the rotor blades adjacent the duct wall (8) the electrical measuring means including at least one electrical discharge device (10) which is adapted to discharge across the clearance gap (G). A ramp voltage is applied to electrode 10 and the voltage at which a discharge occurs is noted. One or more reference gaps 14, 16, 18 may be provided. Three equally spaced electrodes 10 may be provided. <IMAGE>
Description
SPECIFICATION
A Turbine
This invention relates to a turbine and it relates more especially to a turbine having means for measuring the clearance gap between rotor blades and the wall of a duct in a housing of the turbine. Usually, the turbine will be a gas turbine.
The efficiency of gas turbines, and especially those used to power civil transport aircraft, is now the subject of intense study by engine manufacturers. With fuel increasing in price rapidly, and an increasing world shortage in fuel supplies, even small improvements in engine efficiency, and hence fuel consumption, are greatly sought after. For example, a typical wide bodied airliner flying between Europe and the
United States of America may carry 400 passengers and use 250,000 Ibs of fuel. An increase in engine efficiency of 1% would result in 1% less fuel being used, that is 2500 Ibs of fuel saved. Not only would the cost of this amount of fuel be saved, but since the aircraft would carry that much less fuel, a further 10 fare paying passengers could be carried instead.In other words, for a 1% increase in engine efficiency, the potential benefit to the airline is the cost of 2500
Ibs of fuel plus the fares of the extra passengers.
Considering the gas turbine in detail, it is an established fact that for every 100 horse power of usable power produced by a gas turbine engine, approximately 300 horse power is additionally absorbed by the turbine in order to drive the compressor. This additional power is not lost since most of it is put back into the turbine by the compressor. An increase in turbine efficiency of only 1/3% would release an additional 1 horsepower of 1% of the usable power. Taken with the figures in the previous paragraph, it can be seen that for only 1/3% improvement in turbine efficiency, an airline could save 2500 Ibs of fuel and gain 10 trans-Atlantic fares in revenue on each flight.
One of the major factors affecting the turbine efficiency is the clearance gap between its rotor blades and the wall of the surrounding duct of the turbine housing. For maximum efficiency, the gap should be as small as possible to minimise the escape of high energy exhaust gases past the turbine blade tips. However, a realistic gap must be maintained to allow for differential thermal expansion of the turbine and the surrounding duct, and for distortion of the engine structure at full power, so that the turbine does not rub against the duct wall at any time. The most critical condition may often occur during acceleration of the engine to full power after start-up, when the turbine heats up rapidly, and therefore expands to its maximum extent, whereas the more massive housing containing the duct heats up more slowly and therefore does not expand at the same rate.When the housing eventually reaches a stable temperature, as in the cruise condition, the duct has expanded and therefore increased the clearance gap by a significant amount, thus reducing turbine efficiency.
Electrical methods of measuring the turbine blade clearance gap present difficulties due to many factors such for example as the following 1. Ambient temperature is high.
2. The electrical properties of the gas within the clearance gap are not closely defined.
3. Shape factors are difficult to control.
4. The electrical characteristics of the turbine rotor assembly (for example resistance, parasitic inductance and generated emf) are indeterminate.
5. The short duration of the signal with unshrouded rotor blades due to the blade passage frequency and low circumferential solidity of the turbine rotor.
Inspite of the above problems, it is an aim of the present invention to provide a turbine having electrical means for measuring the clearance gap between the rotor blades and the wall of a duct in the housing of the turbine.
Accordingly, this invention provides a turbine comprising a housing, a duct in the housing, a plurality of rotor blades which are mounted on a rotor body and which are positioned inside the duct, a compressor, and electrical measuring means for electrically measuring the clearance gap between the duct wall and the tips of the rotor blades adjacent the duct wall, the electrical measuring means including at least one electrical discharge device which is adapted to discharge across the clearance gap.
Preferably, the turbine is a gas turbine.
Preferably, the rotor blades will be unshrouded.
These unshrouded blades are used in turbines which are constructed to have a high pressure ratio per stage, which in turn leads to supersonic flow through the turbine. The unshrouded blades have no end plates as in the case of shrouded blades. If desired, shrouded blades can also be employed.
The turbine may be one in which the or each electrical discharge device is mounted in the duct wall and is electrically insulated from the duct wall.
The electrical discharge device may be a spark generating electrode in the form of a spark plug.
The measuring means may comprise an electrical discharge device which is adapted to discharge across the clearance gap, and a similar electrical discharge reference device having a known electrical discharge gap. If desired, there may be at least two electrical discharge reference devices for each electrical discharge device which is adapted to discharge across the clearance gap.
The or each electrical discharge reference device may have a variable gap for giving a known signal proportional to the unknown clearance gap.
The turbine may have three equally spaced electrical discharge devices for discharging across the clearance gap positioned around the rotor.
The turbine may include means for varying the clearance gap in dependence upon the measured gap. The means for varying the clearance gap is preferably an electrical means. Pneumatic means may also be employed if desired.
Embodiments of the invention will now be described solely by way of example and with reference to the accompanying drawings in which:
Figure 1 is a side view of part of a turbine in accordance with the invention;
Figure 2 is a plan view of part of the turbine shown in Figure 1.
Figure 3 is an end view of part of the turbine shown in Figure 1;
Figure 4 shows a graph of voltage against time;
Figure 5 shows a graph of volts discharge against clearance gap; and
Figure 6 also shows a graph of volts discharge against clearance gap but illustrates how the clearance gap can be continuously calibrated.
Referring to Figures 1 to 3, there is shown part of a turbine having rotor blade 2, a rotor 3 and a duct 4. The rotor blades 2 rotate in the duct 4.
The duct 4 is defined by a shroud or housing 6 having wall 8. The housing part 6 illustrated in
Figure 1 is recessed as shown to receive an electrode 10 which is insulated from the housing 6 by insulating material 12. There exists a clearance gap G between the inner surface of the electrode 10 and the tip of the blades 2 adjacent the electrode 10. As will be explained hereinbelow, the electrode 10 is adapted to discharge across the gap G and an electrical return path is provided through the rotor blade 2 and the rotor 3 shown in Figure 2.
The turbine may have another electrode 14 as illustrated in part (a) of Figure 1, the electrode 14 giving a single reference gap. The turbine may alternatively have two electrodes 14, 1 6 as illustrated in part (b) of Figure 1, the electrodes 14, 16 giving multiple reference gaps for interpolation. The turbine may further alternatively have a variable gap electrode device 18 for providing a nulling stroke proportional to the unknown clearance gap G.
The discharge across the clearance gap G is relatively tolerant to changes in turbine rotor electrical impedance characteristics. In essence the electrode 10 is fitted to the housing 6 and is electrically insulated from the housing 10 by the insulating material 12 as mentioned above. If a high voltage ramp is injected into the electrode 10 then at some point, the voltage across the gap
G will rise to a sufficiently high level to enable discharge across the gap G in the form of a spark.
If the rate of increase of the high voltage ramp and at the time interval between the start of the ramp and the time at which the discharge occurs is known (see Figure 4), then it is possible to determine the voltage at time of discharge. If a calibration of discharge voltage against gap exists (see Figures 5 and 6), then it is possible to infer the gap dimension. Obviously changes of electrical characteristics and geometrical shape can influence the accuracy of the result.
An improvement in accuracy can be realised by subjecting an accurately known gap to the same
ramp voltage, see Figure 1(a). If the gas flowing through the unknown gap G and the known gap is the same, then a measurement of the unknown gap G can be derived based on the relative times at which discharge occurs. Furthermore, the shape of the electrode 14 in the known gap can be made similar to that of the electrode 10 and can therefore reduce errors due to shape effects.
Further improvements by using more than one known gap are also possible as illustrated in
Figure 1(b). The unknown gap G can then be determined by interpolation as indicated above.
Such a system can be made self-checking.
The exact meaning of a turbine tip clearance measurement is difficult to assess. The turbine is liable to be running eccentrically and the outer case from which the measurement datum is required is liable to distortion. In an ideal system with measurements at three points around the circumference of the turbine and a measurement speed sufficient to measure the clearance of each individual blade, it may be possible to access the relative values of the factors involved in tip clearance. However, since the purpose of the measurement is to provide the datum for a control system and the response of the actuator system is liable to be extremely slow when compared to the blade passage frequency, it is only necessary to know the minimum clearance at each measurement point.In all probability, only the average will be known and deviations from the average will have to be assessed from engine test.
The measurement accuracy of the clearance need not be high over the complete range of possible tip clearances. What is required is a measurement of good accuracy near to a predetermined point and an unambiguous knowledge of its direction relative to that point. With a comparative type of measurement as mentioned above, it is desirable that the known gap be set to the required controlled clearance.
The controlled high voltage ramp rate is the basis for the measurement accuracy.
If average clearances are required it is not necessary to achieve high voltage ramp rates.
However, if individual blade measurement is required, a high ramp rate and also an electrode width approaching one circumferential blade pitch maybe necessary. A wide electrode may also be required if it is desired to have an check facility without running the engine.
The turbine may include means for varying the clearance gap in dependence upon the measured gap. The means for varying the gap may be electrical means associated, for example, with the electrical measuring means. Pneumatic means for varying the gap may also be employed. With the electrical means, a ram or a linear motor may effect movement of part of the duct wall. With the pneumatic means, a ram may effect movement of part of the duct wall.
It is to be appreciated that the embodiments of the invention described above have been given by way of example only and that modifications may be effected.
Claims (12)
1. A turbine comprising a housing, a duct in the housing, a plurality of rotor blades which are mounted on a rotor body and which are positioned inside the duct, a compressor, and electrical measuring means for measuring the clearance gap between the duct wall and the tips of the rotor blades adjacent the duct wall, the electrical measuring means including at least one electrical discharge device which is adapted to discharge across the clearance gap.
2. A turbine according to claim 1 in which the turbine is a gas turbine.
3. A turbine according to claim 1 or claim 2 in which the rotor blades are unshrouded blades.
4. A turbine according to any one of the preceding claims in which the or each electrical discharge device is mounted in the duct wall and is electrically insulated from the duct wall.
5. A turbine according to any one of the preceding claims in which the electrical discharge device is a spark generating electrode in the form of a spark plug.
6. A turbine according to any one of the preceding claims in which the measuring means
comprising an electrical discharge device which is
adapted to discharge across the clearance gap,
and a similar electrical discharge reference device
having a known electrical discharge gap.
7. A turbine according to any one of claims 1 to
5 in which there are at least two electrical
discharge reference devices for each electrical -discharge device which is adapted to discharge
across the clearance gap.
8. A turbine according to claim 6 or claim 7 in
which the or each electrical discharge reference
device has a variable gap for giving a known
signal proportional to the unknown clearance gap.
9. A turbine according to any one of the
preceding claims in which there are three equally
spaced electrical discharge devices for
discharging across the clearance gap positioned
around the rotor.
10. A turbine according to any one of the
preceding claims including means for varying the
clearance gap in dependence upon the measured
gap.
11. A turbine according to claim 10 in which the means for varying the clearance gap is an
electrical means.
12. A turbine substantially as herein described with reference to the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7939501A GB2063477A (en) | 1979-11-14 | 1979-11-14 | Measuring Clearance Gap Between Turbine Blades and Surrounding Duct |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7939501A GB2063477A (en) | 1979-11-14 | 1979-11-14 | Measuring Clearance Gap Between Turbine Blades and Surrounding Duct |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2063477A true GB2063477A (en) | 1981-06-03 |
Family
ID=10509200
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB7939501A Withdrawn GB2063477A (en) | 1979-11-14 | 1979-11-14 | Measuring Clearance Gap Between Turbine Blades and Surrounding Duct |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2063477A (en) |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2164448A (en) * | 1984-09-11 | 1986-03-19 | Mtu Muenchen Gmbh | Capacitive measuring system for measuring the distance between parts in relative motion |
| EP0246576A1 (en) * | 1986-05-23 | 1987-11-25 | Mtu Motoren- Und Turbinen-Union MàNchen Gmbh | Capacitive-measuring system |
| FR2612625A1 (en) * | 1987-03-18 | 1988-09-23 | Daimler Benz Ag | DEVICE FOR DETERMINING ON CONTACT A SPACING DIFFERENCE BETWEEN A WORKPIECE AND THE CONTOUR OF A MOBILE OBJECT RELATIVE TO THE WORKPIECE |
| FR2615248A1 (en) * | 1987-05-14 | 1988-11-18 | Rolls Royce Plc | DEVICE FOR DETECTING THE ROTOR-STATOR INTERSTICE OF A TURBOMACHINE |
| EP1524411A1 (en) * | 2003-10-13 | 2005-04-20 | Siemens Aktiengesellschaft | Method of measuring and minimising the gap between an (abradable) rotor blade and a turbine housing |
| WO2006119655A1 (en) * | 2005-05-11 | 2006-11-16 | Maschinenfabrik Rieter Ag | Contactless measuring method and device on a textile machine |
| US20140167730A1 (en) * | 2012-12-14 | 2014-06-19 | Maschinenfabrik Rieter Ag | Method and Device for Monitoring Contacts of a Rotating Component of a Textile Machine |
| CN105466329A (en) * | 2015-11-23 | 2016-04-06 | 沈阳黎明航空发动机(集团)有限责任公司 | Non-contact engine turbine blade tip radial gap measurement method |
| EP3564420B1 (en) | 2018-05-02 | 2021-07-07 | Trützschler GmbH & Co. KG | Method and device for processing fibres |
-
1979
- 1979-11-14 GB GB7939501A patent/GB2063477A/en not_active Withdrawn
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2164448A (en) * | 1984-09-11 | 1986-03-19 | Mtu Muenchen Gmbh | Capacitive measuring system for measuring the distance between parts in relative motion |
| EP0246576A1 (en) * | 1986-05-23 | 1987-11-25 | Mtu Motoren- Und Turbinen-Union MàNchen Gmbh | Capacitive-measuring system |
| FR2612625A1 (en) * | 1987-03-18 | 1988-09-23 | Daimler Benz Ag | DEVICE FOR DETERMINING ON CONTACT A SPACING DIFFERENCE BETWEEN A WORKPIECE AND THE CONTOUR OF A MOBILE OBJECT RELATIVE TO THE WORKPIECE |
| FR2615248A1 (en) * | 1987-05-14 | 1988-11-18 | Rolls Royce Plc | DEVICE FOR DETECTING THE ROTOR-STATOR INTERSTICE OF A TURBOMACHINE |
| EP1524411A1 (en) * | 2003-10-13 | 2005-04-20 | Siemens Aktiengesellschaft | Method of measuring and minimising the gap between an (abradable) rotor blade and a turbine housing |
| US7018165B2 (en) | 2003-10-13 | 2006-03-28 | Siemens Aktiengesellschaft | Method of minimizing the gap between a rotating turbine blade and a casing of a turbine, a turbine, and a method of determining the wear behavior of a wheel of a rotor |
| WO2006119655A1 (en) * | 2005-05-11 | 2006-11-16 | Maschinenfabrik Rieter Ag | Contactless measuring method and device on a textile machine |
| US20140167730A1 (en) * | 2012-12-14 | 2014-06-19 | Maschinenfabrik Rieter Ag | Method and Device for Monitoring Contacts of a Rotating Component of a Textile Machine |
| US9481947B2 (en) * | 2012-12-14 | 2016-11-01 | Maschinenfabrik Rieter Ag | Method and device for monitoring contacts of a rotating component of a textile machine |
| CN105466329A (en) * | 2015-11-23 | 2016-04-06 | 沈阳黎明航空发动机(集团)有限责任公司 | Non-contact engine turbine blade tip radial gap measurement method |
| EP3564420B1 (en) | 2018-05-02 | 2021-07-07 | Trützschler GmbH & Co. KG | Method and device for processing fibres |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |