Patent Application
20070212212
The invention relates to a method and a device for monitoring the cooling system of a turbine, cooling air being fed to at least one series of blades of the turbine.
In gas turbines, a very hot drive gas which is generated in a combustion chamber is applied to the turbine blades.
In order to avoid damage to the turbine blades, a cooling air system is usually provided by means of which cooling air for cooling the turbine blades is introduced into the interior of the turbine blades.
The turbine blades are therefore usually fashioned as a hollow body which has a number of cooling air ducts in order to convey the cooling air in the interior of the turbine blade in a targeted manner.
In this process a cooling air flow is, for example, diverted several times inside the turbine blade and exits the turbine blade at cooling air outlet openings.
The cooling air ducts and/or the cooling air inlet and/or outlet openings of the turbine blades usually have small diameters so that they tend to become blocked as a result of impurities in the cooling air.
Blocked cooling air openings and/or cooling air ducts of the turbine blades are in many cases the cause of overheating of the turbine blades, particularly in the area around the cooling air outlet openings.
The turbine blades, more particularly their heat-resistant ceramic coating, can be destroyed by such overheating.
In order to avoid such damage it is known to make provision in a turbine for maintenance cycles in which as a rule at least partial dismantling is required in order to be able to ascertain through visual inspection any looming damage or damage which has already occurred to turbine blades.
Such known methods are very costly since the turbine has to be taken out of service for this purpose, which results in production outages. In addition to this, the maintenance measures themselves are very time-consuming and costly, in particular because of the at least partial dismantling of the turbine that is usually required.
Furthermore, maintenance measures of this kind may reveal that no damage is present at all and the measure was not therefore necessary or that far advanced damage is already present, the scale of which could have been prevented if the damage had been detected earlier.
An object of the invention is therefore to indicate an improved method and a device for monitoring the cooling air system of a turbine, wherein cooling air is fed to at least one series of blades of the turbine.
The object is achieved according to the invention by means of a generic method, an air pressure being determined in at least one cooling air reservoir from which the cooling air is extracted and fed to the series of blades.
It is possible by this means to detect blockages of cooling air inlet openings and/or cooling air outlet openings and/or cooling air ducts at an early stage, which helps to avoid damage to the turbine blades.
The air pressure in the cooling air reservoir is a measure of the extent to which the flow of cooling air through the turbine blades may already be impaired.
In one embodiment, the cooling air reservoir is arranged in a turbine housing of the turbine. It is particularly preferable if this cooling air reservoir is arranged in the form of a ring about a turbine axis.
Such a rotationally symmetrical design of the cooling air reservoir enables uniform cooling of the turbine blades which are likewise arranged in a rotationally symmetrical manner.
In a particularly preferred embodiment, the cooling air reservoir is supplied with compressed air from a compressor and it communicates directly with the series of turbine blades via a cooling air duct.
In this embodiment, the cooling air reservoir is arranged in very close proximity to the series of blades to be cooled, which leads to efficient cooling with little loss of pressure in the cooling air flow.
The air pressure is preferably determined by means of at least one pressure sensor which is arranged in the cooling air reservoir.
It is particularly preferred if a current value of the air pressure is transmitted wirelessly to an evaluation unit.
In a further preferred embodiment, it is concluded, due to an increasing air pressure in the cooling air reservoir, that there is a blockage of at least one cooling air inlet or/and outlet opening enveloped by at least one turbine blade or/and of a turbine blade cooling air duct or/and of the cooling air duct thereof.
A blockage of one of the specified means leads, through back-pressure from the cooling air which has been fed, to a rise in the air pressure; this is a clear indication of the presence of a blockage.
With regard to the device, the object is achieved according to the invention by means of a device for monitoring the cooling air system of a turbine, wherein cooling air can be fed to at least one series of blades of the turbine, said device comprising at least one pressure sensor arranged in a cooling air reservoir, it being possible for the cooling air to be extracted from the cooling air reservoir and fed to the series of blades.
Preferably, the cooling air reservoir is arranged in a turbine housing of the turbine.
In one embodiment, the cooling air reservoir is arranged in the form of a ring about a turbine axis.
It is particularly preferable if the device comprises furthermore a compressor for supplying the cooling air reservoir with compressed air, the cooling air reservoir communicating directly with the series of turbine blades via a cooling air duct.
Particularly advantageously, the pressure sensor is enhanced for wirelessly transmitting a current air pressure to an evaluation unit.
An exemplary embodiment of the invention will be described in more detail below with reference to the FIGURE, in which:
FIG shows a device according to the invention for monitoring the cooling system of a turbine.
The FIGURE shows an inventive device 1 by means of which a cooling system 3 of a turbine 5 can be monitored.
The turbine 5 comprises in the present exemplary embodiment four series of turbine blades 7 which are embodied as rotor blades. The series of stator blades which is usually arranged, in the direction of flow of the heating gas, upstream of each series of rotor blades is not shown in the exemplary embodiment.
In connection with the present invention, the cooling air system 3 can also be provided in addition for cooling the series of stator blades.
The most severely temperature-stressed series of blades 7 are the series of blades lying, in the direction of the heating gas, closest to the hot drive gas.
The cooling air system 3 in the present exemplary embodiment is therefore configured for cooling the first two series of blades 7. It is, however, also conceivable for the cooling system 3 to be configured only for one of the series of blades 7, in particular for the first series, or else for several or all series of blades 7.
The turbine blades of the series of blades 7 are fashioned as hollow bodies into which cooling air 9 is introduced.
For this purpose, the turbine blades usually have internally a number of turbine blade cooling air ducts in which the cooling air 9 is conveyed. Furthermore, the turbine blades comprise cooling air inlet and cooling air outlet openings.
The details specified with regard to the conveying of cooling air in the turbine blades are not shown in detail in the FIGURE.
The cooling air 9 is provided by a compressor 19 which supplies cooling air reservoirs 11 with compressed air as cooling air 9.
The cooling air reservoirs 11 are arranged in a rotationally symmetrical manner and in the form of a ring about a turbine axis 17 and inside a turbine housing 15.
To determine the air pressure in the cooling air reservoirs 11, at least one pressure sensor 13 is provided in each case, said pressure sensor being connected, preferably wirelessly, to an evaluation unit 23.
The cooling air 9 provided in the cooling air reservoirs 11 for the series of blades 7 is conveyed via cooling air ducts 21 into the series of turbine blades 7.
A blockage of the cooling air ducts 21 or/and of cooling air inlet openings of the turbine blades or/and of cooling air outlet openings of the turbine blades or/and of turbine blade cooling air ducts is detected by means of the pressure sensor 13, since such a blockage leads to back-pressure in cooling air 9 in at least one cooling air reservoir 11, which in turn translates into rising air pressure in the respective cooling air reservoir 11.
The evaluation unit 23 is enhanced to detect such a rise in the air pressure and, for example, to generate a corresponding alarm or fault message for the personnel operating the turbine 5.
In connection with the invention, the absolute air pressure of the cooling air 9 or a change therein is preferably determined in at least one cooling air reservoir 11. With regard to the first series of rotor blades, the air pressure is measured between the central hollow shaft and the first turbine wheel disk; correspondingly, the air pressure in respect of the second series of rotor blades is measured between the first and the second turbine wheel disk.
| Number | Date | Country | Kind |
|---|---|---|---|
| 04016249.7 | Jul 2004 | EP | regional |
This application is the US National Stage of International Application No. PCT/EP2005/053240, filed Jul. 7, 2005 and claims the benefit thereof. The International Application claims the benefits of European application No. 04016249.7 EP filed Jul. 9, 2004, both of the applications are incorporated by reference herein in their entirety.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP05/53240 | 7/7/2005 | WO | 1/9/2007 |
