Patent Application
20140090457
This invention relates generally to gas turbine monitoring and testing practices and, more specifically, to a metalized ceramic Kiel-type pressure sensor used to gather total pressure and/or total temperature data from the surrounding flow in the hot gas path of a turbine engine.
Kiel-type pressure sensor probes are often used to measure total pressure in a fluid environment where the direction of flow is not known or changes with operating conditions. Associated pressure tubing connects the probe to a transducer where the pressure measurement is translated to a signal for routing to a data acquisition system. The Kiel-style probe has a shroud to protect the pressure tubing. The shroud makes the probe insensitive to a range of yaw and pitch angles because the flow is straightened as it enters the probe. Kiel-style probes can be installed in a variety of turbine components/locations, for example, in a low-pressure steam-turbine exhaust duct, enabling measurement of the total pressure distribution exiting the last-stage row of buckets during performance testing. U.S. Pat. No. 4,433,584 exemplifies the use of a plurality of Kiel-style probes (referred to hereinafter as “Kiel probes”) on a rake downstream of a turbine section. In addition, Kiel probes are sometimes mounted in the hot gas path of the turbine. i.e., on components of the gas turbine that are contacted by the hot combustion gases, especially in the first and second stages of the gas turbine.
Traditional Kiel probe shrouds or housings used in gas turbine applications, and especially those mounted on nozzles in the hot gas path, have been made from high-temperature alloys. Even these high-temperature alloys, however, cannot withstand the temperature in the first stage and sometimes even in the second stage of modern gas turbines where temperatures can reach 2300° F. Unless active cooling schemes are employed to cool the metal alloy shrouds, the shrouds may well disintegrate under the extremely high temperatures. While platinum is an option for the shroud composition, it is very expensive and thus rarely if ever used in Kiel probe applications.
Ceramic materials, while able to withstand the high temperatures in the hot gas path of the gas turbine, are difficult to bond to the host metal alloy nozzle or other metal alloy turbine component.
There remains a need therefore, for a relatively low-cost Kiel probe shroud construction that will survive the high-temperature environment of a gas turbine hot gas path.
In accordance with an exemplary but nonlimiting embodiment, there is provided a pressure probe comprising an elongated cable provided with a sensing tip, a portion of the elongated cable and the sensing tip enclosed within a ceramic shroud, the ceramic shroud having at least a portion thereof metalized to facilitate bonding to a metal component.
In another aspect, the present invention provides pressure probe assembly capable of withstanding temperatures up to about 2300° comprising at least one pressure probe secured to a component, the pressure probe comprising an elongated cable provided with a sensing tip, a portion of the elongated cable and the sensing tip enclosed within a silicon carbide ceramic shroud, the silicon carbide ceramic shroud having at least a portion thereof metalized; the metalized portion of the silicon carbide ceramic shroud brazed to the metal component.
In still another exemplary but nonlimiting aspect, the present invention provides a pressure probe assembly capable of withstanding temperatures up to about 2300° comprising at least one pressure probe secured to a metal alloy gas turbine hot gas path component, the pressure probe comprising an elongated cable provided with a sensing tip, a portion of the elongated cable and the sensing tip enclosed within a silicon carbide ceramic shroud, the silicon carbide ceramic shroud having at least a portion thereof metalized; the metalized portion of the silicon carbide ceramic shroud brazed to the metal alloy gas turbine hot gas path component.
The invention will now be described in greater detail in conjunction with the drawings identified below.
With initial reference to
It will be understood that the pressure sensing cable or tubing 14 and the pressure-sensing tip 16 form no part of the invention in that they are well-known in the art. This invention has to do with the composition of the shroud or housing 12 of the Kiel probe 10 and the manner in which the Kiel probe shroud or housing is attached to a metal turbine component or a metal instrumentation rake as described further below.
In accordance with an exemplary but nonlimiting embodiment of the invention, the Kiel probe shroud or housing 12 is formed of a high-temperature ceramic material. In order to bond the ceramic Kiel probe shroud or housing to a metal component, at least a portion of the ceramic shroud indicated at 20 in
In the exemplary embodiment, the Kiel probe shroud or housing 12 is comprised of silicon carbide (Sic). More specifically, it has been found that silicon carbide not only withstands the high-pressure/temperature environment of a turbine engine hot gas path, but also is easily machined. In addition, a portion of the SiC shroud can be laced with a metal alloy so that the shroud can be bonded with a metal alloy turbine component or pressure-sensing rake. The entire length of the Kiel probe shroud need not be metalized. It is only required that the metalized portion be of sufficient extent to enable the desired bonding with the metal alloy component or device to which the Kiel probe is to be attached. Thus, an axially-extending portion 20 of the substantially cylindrical silicon carbide Kiel probe shroud or housing 12 shown in
While the probe 10 has been shown to have a right-cylinder shape, it may have other shapes such as tapered or conical, etc. along all or part of its length dimension.
In an exemplary but non-limiting embodiment, and as best seen in
In one exemplary but nonlimiting example, the host metal alloy may comprise Inconel 718, and the host component may be a turbine nozzle or other stator component, a turbine exhaust duct, or an instrumentation rake (or other instrumentation support or holder) secured to an exhaust duct or other turbine structure, e.g. a combustor transition piece as shown in
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
