Patent Application
20050242526
The present invention relates to a hot gas seal and a hot gas seal assembly.
Walls of high temperature gas reactors, e.g. the walls of turbine combustion chambers, need to be shielded by a suitable thermal shield against attack of the hot gas. The thermal shielding can be achieved by providing a hot gas resistant liner, which usually comprises a number of shield elements covering the wall to be shielded. The heat shield elements can e.g. be implemented in form of ceramic heat shield elements (CHS elements) or in form of suitable metallic heat shield elements. To allow for thermal expansion when being exposed to the hot gas, the heat shield elements are arranged such that gaps are left between neighboring heat shield elements. In order to prevent hot gas from passing through these gaps from the hot gas side of a heat shield, e.g. to a carrier structure to which the heat shield elements are fixed, gaps would need purging with air to avoid over-heating. This air is costly leakage.
In EP 1 302 723 A1 it is proposed to seal gaps between heat shield elements with sealing elements to prevent hot gas from passing the gaps. This sealing elements my be cooled.
It is an object of the present invention to provide a hot gas seal and a hot gas seal assembly by which the cooling of the hot gas seal can be improved.
The first object is solved by a hot gas seal as claimed in claim 1, the second object is solved by a hot gas seal assembly as claimed in claim 11.
An inventive hot gas seal comprises a sealing body and means for allowing a cooling fluid, preferably cooling air, to flow through the interior of the sealing body.
Such a hot gas seal can be effectively cooled by guiding a cooling fluid through the interior of the sealing body.
In a first embodiment of the present invention, at least one cooling channel is formed to extend through the interior of the sealing body as said means for allowing a cooling fluid to flow through the interior of the sealing body.
In the first embodiment, the sealing body may be shaped in a tube like manner such that it comprises a circumferential portion and an interior space surrounded by said circumferential portion which defines a cooling channel for allowing a cooling fluid to flow through the interior of the tube like shaped sealing body.
In a second embodiment of the inventive hot gas seal, the sealing body is made from a porous material the pores of which are inter-connected so that the pores form said means for allowing a cooling fluid to flow through the interior of the sealing body. Such a porous material allows for an effective distribution of the cooling air in the interior of the sealing body and, therefore, for evenly cooling the hot gas seal.
In an advantageous development of the second embodiment, the porous material is an elastic porous material. Such a hot gas seal can be fixed between neighboring heat shield elements by spring forces. As the elastic porous material, a ceramic material, metal foam, or a suitable polymer material may be used. The choice of the material to be used may depend on the temperatures of the hot gas which is to be prevented from passing through the gaps between two heat shield elements.
A hot gas seal assembly according to the invention comprises a hot gas seal which comprises a sealing body in which at least one cooling channel extending through the interior of the sealing body is formed as a means for allowing a cooling fluid to flow through the interior of the sealing body. The inventive hot gas seal assembly further comprises means which are arranged outside of the hot gas seal for channeling a cooling fluid flow, preferably a cooling air flow, at least partly through the cooling channel of the hot gas seal. By providing such means a highly efficient cooling of the hot gas seal of the assembly is possible.
The means for channeling cooling fluid through the cooling channel may be designed such that a high static pressure is build up in front of them which channels the cooling fluid at least partly through the cooling channel.
The inventive hot gas seal assembly may further comprise a means arranged outside the hot gas seal for guiding the cooling fluid which has flown through the cooling channel back into the cooling fluid flow. Such a means may be designed such that a high static pressure is build up in front of them which guides the cooling fluid back into the cooling fluid flow.
As a means for building up high static pressure, a fixing bolt for fixing a heat shield element or any other flow restriction may be used.
Further features, properties, and advantages of the present invention are described hereinafter with reference to the accompanying drawings, by means of detailed embodiments.
A first embodiment of the inventive hot gas seal is shown in
The hot gas seal 22 comprises a sealing body 24 which has a tube-like shape. The interior of the sealing body 24 forms a cooling channel 26 for allowing a cooling fluid, which in the present embodiment is cooling air, to flow through the hot gas seal 22. In the present embodiment, the sealing body 24 comprises a ceramic portion 28 as a highly heat resistant portion.
The hot gas seal 22 is arranged such in the space formed by the first grove 14 and the second grove 20 that the ceramic portion 28 shows towards the hot gas side of the liner, i.e. the sides of the heat shield elements which are disposed to the hot gas.
Inside the cooling channel 26, an axial flow of cooling air 30 and a convective cooling air flow which originates from the axial flow 30 and flows clockwise and counter-clockwise along the wall of cooling channel towards the center of the ceramic portion 28 (indicated by arrows) are provided. At the center of the ceramic portion 28, the convective cooling air flow is directed back towards the axial cooling air flow 30. With the described hot gas seal, an effective cooling of the ceramic portion, which is disposed to the hot gas, is possible.
A modification of the first embodiment is shown in
In the modification shown in
A further development of the first embodiment is shown in
A second embodiment of the present invention is shown in
In the second liner 318, a recess 320 is formed in the second front face 316 at the edge to the hot gas side 317. The heat shield elements 310, 318 are arranged such that the front faces 312, 316 are disposed opposite to each other and that the recess 320 forms, together with the first front face 312, a space for a accommodating therein the hot gas seal 322 according to the second embodiment.
Through the gap 331 between the first front face 312 and the second front face 316, a cooling air flow 332 outgoing from a carrier structure flows towards the hot gas side of the liner.
The sealing body 324 of the hot gas seal 322 is made from a porous material the pores of which are interconnected such that they form channels through which the cooling air of the cooling air flow 332 can pass through the hot gas seal. Thus, the cooling air can flow through the hot gas seal 322.
In addition, the material of the sealing body 324 is an elastic material, so that the hot gas seal 322 is held in place by spring forces which act on the first front face 312 and the part of the recess 320 which lies opposite to the first front face 312. As elastic material, all materials which are suitable for being disposed to a hot gas can be used. Examples for such materials are porous ceramics, like abradable TBC, metal foams or polymeric materials.
An embodiment for an inventive hot gas seal assembly 400 is shown in
Although in the shown embodiment for the hot gas seal assembly the fixing bolts 434, 436 are used to build up high and low static pressure, other means could be used as well as long as they allow for building up a high pressure in front of and a low pressure behind the hot gas seal 422.
