Patent Grant
7240673
1. Field of the Invention
The present invention relates to a flange for optical flame observation in a gas turbine. The flange comprises at least one bore for optical observation, in which bore there is arranged at least one pane for separating the flame-side space, which is in substantially direct communication with a combustion chamber in which the at least one flame that is to be monitored is arranged, from the outside space, from which the observation of the at least one flame can take place.
2. Brief Description of the Related Art
For safety reasons, the flames in the combustion chamber of a gas turbine have to be observed and monitored. Inter alia in the case of annular combustion chambers, in which to a certain extent there is a single, encircling flame supplied by a plurality of burners arranged over the circumference of the circle, this monitoring and observation is carried out, for example, by at least one observation tube being passed through the housing of the gas turbine to the outer side of the gas turbine. The tube leads through cavities which are arranged in the housing and are used, for example, to supply cooling air, additional combustion air or to accommodate fuel supply lines, etc. The tube is usually open toward the combustion chamber, i.e. the pressure prevailing in the tube usually substantially corresponds to the pressure in the combustion chamber, and the temperature in the tube is likewise usually in the region of the temperature in the combustion chamber, although on account of weak convection in the tube a decreasing gradient is established toward the outer side of the gas turbine with respect to the temperature.
Observation means in the form of flame monitors with optical detectors, which allow automated and continuous observation and monitoring of the flame activity, are usually arranged on the outer side of the gas turbine. These observation means are arranged outside the gas turbine, i.e. substantially at room temperature and standard pressure, on the one hand in order not to apply excessive thermal and mechanical loads to these observation means, and on the other hand to make them easier to exchange and easier to carry out maintenance work on. In order accordingly to seal the tube with respect to the outer side, where substantially room temperature and standard pressure prevail, without at the same time impairing the optical path for observation, it is customary to provide at least one suitable pane, i.e. a pane which does not interfere with the optical path of flame observation, which pane is fitted either at the end of the observation tube or in a flange placed onto the observation tube. On account of the high temperature differences and pressure differences between the interior of the observation tube and the surroundings of the gas turbine, this pane has to satisfy high mechanical demands and has to be well sealed. For this purpose, it is customary for the at least one pane to be fitted into the flange, i.e. for example welded into the flange.
Accordingly, one aspect of the present invention includes providing a flange having at least one inserted pane which, for example, allows the observation of flames in the combustion chamber of a gas turbine. This is a flange for optical flame observation, comprising at least one bore for optical observation, in which bore there is arranged at least one pane for separating the flame-side space, which is in substantially direct communication with a combustion chamber in which the at least one flame that is to be monitored is arranged, from the outside space, from which the observation of the at least one flame can take place.
An exemplary flange in accordance with principles of the present invention is distinguished by the fact that two panes, which delimit a sealed intermediate space in the bore, are arranged one behind the other with respect to the optical axis, exemplarily parallel to one another and perpendicular to the optical axis, and that means for dehumidifying the sealed intermediate space are provided. Arranging two panes one behind the other has the advantage of creating a redundant system. In other words, the presence of two panes one behind the other results in increased safety, since each pane alone is advantageously able to withstand the entire temperature difference and pressure difference between the outside environment and the interior of the observation tube. Therefore, a defect at one of the two panes does not immediately lead to failure of the gas turbine (which is inevitable if there is open connection between the combustion chamber and the outside environment), since the second pane can immediately take over the entire function of the first pane all on its own. Arranging two panes one behind the other presents problems insofar as humid air which may be enclosed in the intermediate space between the two panes has the tendency to condense on the cold pane, i.e. on the pane facing the observation means, above a certain humidity level. Fogging of this pane makes it difficult if not impossible to observe the flame using the observation means, since the optical path is significantly impeded and therefore the measurement is distorted. According to the invention, this problem is solved by the provision of means for dehumidifying the intermediate space between the two panes. This can be achieved, for example, by the application of a vacuum. However, applying a vacuum has the drawback that the intermediate space between the two panes has to be extremely well sealed, since otherwise the vacuum cannot be ensured in the long term. In addition, under the standard pressure and temperature loads when using a flange of this type at a gas turbine, complete leaktightness of the intermediate space can only be ensured with very great difficulty, and accordingly a flange with an evacuated intermediate space has to be exchanged at frequent intervals, since evacuation in situ is scarcely possible. The continuous dehumidification of this intermediate space by dehumidification means of another type therefore prove to be simpler and more expedient, since maintenance of dehumidification means of this type is significantly simpler compared to when this region is evacuated. In particular, it is not generally necessary in this case for the entire flange to be exchanged, but rather only the dehumidification means have to be exchanged.
According to a first exemplary embodiment of the present invention, the means are accordingly designed in the form of at least one drying cartridge. In this case, the drying cartridge may accordingly be arranged in the flange in a region which is in communication with the intermediate space between the two panes, so as to ensure dehumidification of this intermediate space. It is also possible for the drying cartridge to be arranged directly in the intermediate space, provided that it does not interfere with the optical path for observation. Products which can be reused for dehumidification after the uptake of moisture by simply being heated are particularly suitable for use as drying cartridges. These are usually, for example, hygroscopic substances stored in a porous aluminum container which have the property of releasing the water which they have taken up again when an elevated temperature is applied. For example, drying cartridges of this type, after the uptake of moisture, can simply be dried again by heating in a furnace and then reused for dehumidification of the intermediate space.
According to a further exemplary embodiment of the invention, the dehumidification means are arranged in such a manner in the flange that they can be inserted, exchanged and/or removed from the outer side of the flange, remote from the intermediate space. This arrangement of, for example, a drying cartridge in the flange allows these dehumidification means to be exchanged without one of the two panes positioned one behind the other having to be removed from the flange. This makes maintenance of the flange particularly simple and efficient. In this case, the procedure is preferably such that there is at least one cavity, which is arranged to the side of the intermediate space with respect to the optical axis, for the dehumidification means, which cavity is in communication with the intermediate space, this communication being ensured in particular by means of at least one opening between the cavity and the intermediate space. This arrangement allows simple accessibility from the side of the flange (substantially from the radial side with respect to the optical axis) without the optical path being disrupted by the presence of the dehumidification means. Also preferably, the accessibility to the dehumidification means is ensured by the fact that the flange has at least one hole which is arranged substantially perpendicular to the optical axis, is in communication with the intermediate space via at least one opening, provides a cavity for receiving the means and can be sealed off with respect to the outer side of the flange by means of closure means, in particular in the form of a sealing screw. The hole may have any desired cross section, but is advantageously of cylindrical configuration (in which case the diameter is particularly preferably reduced just in front of the intermediate space, so that the cartridge is held in the region with a large diameter without dropping into the intermediate space), and is provided with an internal screw thread in its region remote from the intermediate space, so that, for example, a sealing screw (if appropriate provided with sealing rings) allows simple sealing of this hole after the drying means have been inserted.
A further exemplary embodiment of the present invention is distinguished by the fact that the observation-side pane can be inserted, exchanged and/or removed from the observation-side end of the flange, and/or that the flame-side pane can be inserted, exchanged and/or removed from the flame-side end of the flange. This simple way of exchanging the panes from the respective side likewise ensures simple, low-cost maintenance of the observation flange. For example, the panes can simply be removed and replaced or cleaned in the event of fracture or in the event of them becoming dirty, respectively. In this context, it can be particularly advantageous for the mechanical configuration of the exchangeability to be identical in form from both sides, so that both the two panes and their securing means in the flange are identical, meaning that the number of different parts is minimized. The securing means used for the panes are advantageously grub screws with a central bore, i.e. at least one of the panes is held in an internal screw thread arranged in the flange from the side remote from the intermediate space by means of at least one grub screw with an external screw thread and with an axial hole. Moreover, in this context it has proven advantageous to provide second means, allowing the grub screw to be fixed with respect to its rotation in the internal screw thread. This is in order to prevent the grub screws from coming loose during operation under the vibrations which occur in gas turbines, which can cause the leaktightness of the intermediate space to decrease on account of the loosening of the pressure on the plates. It is usual for the leaktightness on the side of the panes facing the intermediate space to be ensured by sealing rings (O rings). Sealing rings may also be arranged on the side facing the grub screw, if appropriate in combination with a washer.
An exemplary embodiment of the grub screw is distinguished by the fact that it, on the side remote from the pane, has at least one bore, in particular in the form of a blind hole, which is arranged substantially parallel to and laterally offset from the optical axis, and that the flange, at the corresponding end side, has a bore, in particular in the form of a blind hole, which runs substantially parallel to the bore and is arranged axially outside the internal screw thread with respect to the optical axis, it being possible for the grub screw to be fixed by means of a securing clip which projects into the two bores. This is a simple, readily realizable embodiment of the second fixing means. The securing clip, which can easily be realized, for example, by a U-shaped wire, is in this way fixed in a simple and to a certain extent automatic way by the flange being secured to the housing and/or observation tube on the combustion chamber side and/or by the fitting of an observation means to the outer side.
Another exemplary embodiment is characterized in that the observation of the flame is carried out by means of a flame monitor with optical detector, and in that in particular the flange is attached to the housing of a gas turbine by means of a flange plate, the observation of the at least one flame in the combustion chamber of the gas turbine being carried out via an observation tube which projects through the housing of the gas turbine on the optical axis toward the combustion chamber and thereby connects the combustion chamber via the interior of the observation tube.
Another exemplary embodiment of the invention has panes made from quartz glass with a thickness in the range from 0.5 to 2 cm, in particular in the region of 1 cm, the panes having a diameter in the range from 1.5 to 4 cm, in particular in the region of 3 cm. In this case, the two panes are advantageously spaced apart from one another along the optical axis by a distance in the range from 2 to 10 cm, in particular in the range from 3 to 5 cm, and seals, in particular in the form of Teflon or graphite seals, are provided in the direction of the intermediate space and/or toward the securing means remote from the intermediate space.
The invention is to be explained in more detail below on the basis of exemplary embodiments in conjunction with the drawing, in which:
In its central region, along the optical axis 8, the flange 1 has a bore which is used for observation of the flame. In this case, this bore is of cylindrical design. However, the bore may also have a rectangular or polygonal cross section. The bore is of stepped design from both sides of the flange, so that the two panes 9 and 10 can be pushed in from both sides until they come to a stop. A sealing ring 11 is arranged between the stop and panes 9 and 10, this sealing ring 11 sealing the intermediate space 22 arranged between the panes when the panes 9 and 10 are pressed onto the stop. The bore widens out toward the end of the flange on both sides following the panes 9 and 10, with an internal screw thread 15 being provided in the outermost region. A grub screw 13 or 14 with a central hole (to ensure that the optical axis is not locked) is then screwed into this outer region of the bore and serves to press the respective pane 9 or 10 onto the abovementioned stop. First of all a further seal 11 is arranged between grub screw 13 or 14 and pane 9 or 10, respectively, and in addition a washer 12 is preferably provided between this seal 11 and grub screw 13 or 14, which washer is intended, inter alia, to prevent damage to the sealing ring 11 when the grub screw is being screwed in. The grub screw 13 or 14 is cylindrical in form in its region 19 facing the pane, whereas in the outer region 20 the internal cross section of the grub screw 13 or 14 is polygonal or of similar form, so that this nut can easily be screwed into the flange 1 from the outside using a corresponding tool which is to be inserted (for example a hexagon key). Moreover, the grub screw 13 or 14 has one or more blind holes 17, and the flange 1 has corresponding blind holes 16 at its end sides. The blind holes 16 and 17 are provided for the purpose of accommodating a securing clip 18, so that the nut can no longer be rotated with respect to the flange 1 once the securing clip 18 has been inserted. One blind hole 16 is usually sufficient for this purpose, since the large number of holes 17 in the grub screws 13 and 14 means that there is always a suitable distance for introduction of the wire 18 without disruption to the optical axis. This fixing prevents the grub screw 13 or 14 from coming loose in the screw thread 15 under the vibrations which customarily occur when gas turbines are operating, which would mean that the sealing of the panes 9 and 10 would also no longer be ensured in the long term.
This particular mechanical realization of the securing of the panes 9 and 10 in the flange now makes it possible, unlike with the welding process which is customary in the prior art, to easily exchange and/or clean the panes, since the panes can be removed from the flange and cleaned or replaced by simply loosening the grub screws. This new realization is advantageous in particular in combination with the mechanism for fixing the grub screw, which makes this flange especially suitable for use in gas turbines.
The flange 1 has an additional bore which runs substantially perpendicular to the axis 8 and which narrows in stepped form just before the intermediate space 22 to form a connecting opening 23. The cavity 21 formed in the bore is in communication with the intermediate space 22 via the opening 23. A drying cartridge 24 can be inserted into this bore from the transverse outer side of the flange, and then a sealing screw 25 can be screwed and fixed into a corresponding screw thread 26 provided in the bore, with the screw 25, together with the sealing rings, sealing off the cavity 21 with respect to the outside, optionally in a stepped arrangement.
The opening 23 has a diameter of 10 mm, and the space 21 corresponds to a ¾″ thread.
The drying cartridge 24 is operatively connected to the intermediate space 22 and can therefore dehumidify this intermediate space 22. On the other hand, however, this drying cartridge 24 can also be exchanged or replaced very easily, since it is readily accessible from the outer side of the flange by simply unscrewing the sealing screw 25 (if appropriate even when the gas turbine is operating). Examples of suitable drying cartridges 24 include products of type A3 produced from Süd Chemie AG, Cologne, DE. Cartridges of this type are made from aluminum sheet, are filled with approx. 3 g of molecular sieves and can be regenerated. The uptake of moisture is effected by means of a nonwoven via a hole in the underside. Their diameter is 23 mm and their height 11 mm. The molecular sieves are synthetically produced zeolites. The uptake of water is approx. 18% by weight, irrespective of the relative humidity prevailing. The regeneration temperature is between 250 and 300 degrees Celsius (the moisture stored in drying means is released again at these temperatures). At lower temperatures, silica gel or blue gel would also be conceivable drying agents. In other words, cartridges of this type have the advantage that they can be regenerated simply by being heated, and therefore do not have to be completely replaced. If appropriate, the cartridges may additionally have a moisture indicator which can be fitted into the housing and allows inspection or monitoring of the state of the cartridge.
This design of the flange 1 has proven suitable for connection to observation tubes 5. These observation tubes 5 have a diameter which is usually at least as great as the bore in the region of the intermediate space 22, i.e. for example 3 cm. An observation tube of this type is in direct communication with the combustion chamber (the observation is usually at a distance of approximately 1 meter from the flame) and to a certain extent serves as a passage through the housing 4 of the gas turbine. The pressure conditions in the tube are substantially identical to those in the combustion chamber, i.e. pressures usually in the range of, for example, approx. 30 bar. Therefore, with an outside pressure of 1 bar, a pressure difference in the region of 29 bar prevails at the panes. Temperatures comparable to temperatures in the combustion chamber are likewise present in the observation tube. Accordingly, when the gas turbine is operating, the flange 1 is usually at an overall temperature of over 100 degrees Celsius. Consequently, the seals 11 should be made from graphite or Teflon or similar heat-resistant materials, and the panes 9 and 10 are usually formed from quartz glass with a thickness of approx. 1 cm. The panes are spaced apart from one another by approx. 3 cm and have an external diameter of approx. 3 cm. The diameter of the bore in the region of the intermediate space 22 is 2 cm. In order to ensure redundancy and completeness also with regard to observation, it is typical for three observation tubes of this type to be distributed over the circumference of the gas turbine.
While the invention has been described in detail with reference to exemplary embodiments thereof, it will be apparent to one skilled in the art that various changes can be made, and equivalents employed, without departing from the scope of the invention. Each of the aforementioned documents is incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0888/02 | May 2002 | CH | national |
This application is a Continuation of, and claims priority under 35 U.S.C. § 120 to, International Application no. PCT/EP03/50179, filed 20 May 2003, by the inventors named herein, and claims priority under 35 U.S.C. § 119 to Swiss application no. 2002 0888/02, filed 28 May 2002, the entireties of both of which are incorporated by reference herein.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3154821 | Weker | Nov 1964 | A |
| 4210120 | Ritopecki | Jul 1980 | A |
| 4332663 | Berneke | Jun 1982 | A |
| 5000580 | Leininger et al. | Mar 1991 | A |
| 5748090 | Borg et al. | May 1998 | A |
| 6024084 | Gerhardinger | Feb 2000 | A |
| 6168112 | Mueller et al. | Jan 2001 | B1 |
| Number | Date | Country |
|---|---|---|
| 37 36 442 | May 1988 | DE |
| 0 181 435 | May 1986 | EP |
| 343 580 | Feb 1931 | GB |
| 2000073667 | Mar 2000 | JP |
| 2000073668 | Mar 2000 | JP |
| 2004324268 | Nov 2004 | JP |
| 8912774 | Dec 1989 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20050115167 A1 | Jun 2005 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP03/50179 | May 2003 | US |
| Child | 10998044 | US |
