Patent Application
20060228209
The present invention relates generally to seals between a turbine rotor and a stationary component of the turbine and particularly to a seal having an abradable coating on the stationary component between caulked-in teeth in opposition to radial teeth on the rotor.
In turbines, particularly steam turbines, seals between rotary and stationary components are a critical part of steam turbine performance. It will be appreciated that the greater the number and magnitude of steam leakage paths, the greater the losses of efficiency of the steam turbine. Many and various types of sealing arrangements have been proposed and utilized for sealing between rotating and stationary turbine components. For example, high-low labyrinth seal teeth are often used in steam turbine interstage and shaft end packing. The clearances between the teeth and the opposed turbine component are typically sufficiently large to avoid any contact between the rotating and static parts. Tight clearances, however, lead to contact and rubs e.g., during transient operation of the turbine. Rubs, of course, lead to severe damage to the teeth, such as mushrooming resulting in much reduced sealing capability. On the other hand, large clearances lead to unwanted leakage paths of substantial magnitude which, in turn, affect the efficiency of the turbine. Therefore, cold clearances are typically set such that there is no contact between the rotating and stationary parts and particularly between the seal teeth and the opposed component. Accordingly, there has developed a need for a seal between rotatable and stationary components of a turbine which minimizes or eliminates the aforenoted problems and achieves an effective seal with reduced clearances and increased seal efficiency.
In a preferred embodiment of the present invention, there is provided a turbine comprising: a rotor; a stationary component; an end shaft seal between the rotor and the stationary component; the seal including (i) a plurality of teeth carried by the rotor at axially spaced locations therealong and projecting generally radially outwardly therefrom and (ii) a plurality of teeth carried by the stationary component at axially spaced locations therealong and projecting generally radially inwardly therefrom; the teeth carried by the rotor and the teeth carried by the stationary component being interdigitated and axially spaced from one another; and an abradable coating on the stationary component between the teeth thereof at locations in radial opposition to the teeth on the rotor.
In a further preferred embodiment of the present invention, there is provided a turbine comprising: a rotor; a stationary component; a seal between the rotor and the stationary component; the seal including (i) a plurality of teeth carried by the rotor at axially spaced locations therealong and projecting generally radially outwardly therefrom and (ii) a plurality of teeth formed by strips of metal mechanically secured to the stationary component at axially spaced locations therealong and projecting generally radially inwardly therefrom toward the rotor; the teeth carried by the rotor and the teeth strips carried by the stationary component being axially spaced from one another; and an abradable coating on the stationary component between the teeth strips at locations in radial opposition to the teeth on the rotor.
Referring now to the drawings, particularly to
As illustrated in
It will also be appreciated that with the arrangement of caulked-in teeth on at least the stationary component 12 or both the stationary and rotary components 12, 14 these strip seals provide more equivalent teeth within the same axial extent as in a conventional labyrinth seal teeth design. This is made possible because of the reduction in width i.e. in the axial direction of the strip seals at least on the stationary component or on both the stationary and rotary components in comparison with the width of conventional labyrinth seal teeth.
The abradable coating constitutes a sacrificial coating which is cut by the seal teeth on the rotary component without causing any damage to the teeth 16 of the rotary component 14. The abradable material may be of the type disclosed in U.S. Pat. No. 6,547,522 of common assignee herewith, the disclosure of which is incorporated herein by reference. Thus the abradable material may comprise a composition having a first component including aluminum, cobalt, nickel, chromium, yttrium and a second component selected from the group consisting of hexagonal boron nitride and a polymer. Any one of the additional abradable materials disclosed in U.S. Pat. No. 6,547,522 can be similarly utilized in the present invention. The abradable coating 22 is thermally sprayed on the stationary component. Other types of abradable seal systems may also be utilized such as fiber metals and honeycomb structures. Both fiber metals and honeycombs are applied by a brazing process.
Also as illustrated in
In
Referring now to
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.
