US1999739A

US1999739A - Removable packing strip

Info

Publication number: US1999739A
Application number: US717142A
Authority: US
Inventors: Harold V Rasmussen
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1934-03-24
Filing date: 1934-03-24
Publication date: 1935-04-30
Anticipated expiration: 1952-04-30

Description

April 30, 1935. H. v. RASMUSSEN 1,999,739

REMOVABLE PACKING STRIP Filed March 24, 1934 E0 1a \ze r ROTOR STATIONARY BLHDE BLADE T2 5 24 f 1 2 M- u INVENTOR Hnnow V. Finsmussaw (5. 77. W fox/(OWL, V ATTORNEY WITNESSES:

Patented Apr. 30, 1935 PATENT OFFICE REMOVABLE PACKING STRIP Harold V. Rasmussen, Philadelphia; Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa, a corporation of Pennsylvania Application March 24, 1.834, Serial No. 717,142

3 Claims. (mass-7:1)

My invention relates to turbines and more particularly to improved means providing for endtightening between cooperating rows of stationary and moving blades; and by end-tightening is meant means of reducing leakage by the provision of relatively small axial clearances between successive blade rows in distinction from radial clearances over the tips of blades, the amount of the axial clearance being set by the axial adjustment of the rotor with reference to the stator.

More particularly, my invention relates to means for end-tightening stages of reaction or impulse blading, wherein leakage of steam around. the tips of the stationary and moving blades is limited by sealing or wearing strips carried at the exitedge sides of the shrouds of the stationary blades and at the inlet-edge sides of the shrouds of the moving blades, the wearing strips cooperating with radial surfaces provided adjacent to the roots of the stationary and moving blades so as to define relatively close clearances. Since the wearing strips are formed separately from the shrouds, they may be made of the most suitable material for the purpose and they may be reada ily replaced. A further feature of my invention is to have the stationary blade row shroud of each stage extending down-stream beyond its packing strip so as to deflect steam entering radially through the clearance between the packing strip and the cooperating radial surface for flow in an' axial direction through the moving blades, whereby turbulence due to radial cross flow and the consequent leakage loss are avoided. A further object of my invention is, therefore, to provide turbine blading having these advantageous features of construction and of operation.

These and other objects are effected by my invention as will be apparent from the following description and claims taken in connection with the accompanying drawing, forming a part of this application, in which:

The figure is a detail view of a turbine stage having my improvement applied thereto.

Referring now to the drawing more in detail, I show a'turbine casing or cylinder II) and a rotor II provided with a suitable number of stages of cooperating moving and stationary rows of blades. For example, I show a single stage consisting of a row of stationary blades I2 followed by a row of moving blades I3. Shrouds I4 and I5 are attached to the tips of the blades I2 and I3, respectively.

I have shown the rows of blades I2 and I3 provided with lateral packing members, I6 and I1, which may be separate members or formed integrally with the base of the blades, the members presenting radial surfaces It and I9 adjacent to the base of the blades at the down-stream side of stationary blades I2 and at the up stream side of moving blades I3.

Each moving blade row shroud i5 is rabbeted or channeled internally and at the up-stream side, as shown at Zii, to receive-a circumferentiallyextending packing strip 2 I, which is of such thickness that its internal surface is substantially flush with the internal surface of the shroud IS.

The packing strip 2I is preferably connected to the shroud I5 by rivets 22. The shroud 2i extends upstream at the inlet-side of the moving blades I3 and cooperates with the radial surface I8 to define relatively close clearance with respect. to the latter to minimize leakage of steam from between the rows of blades and out over the tips of the moving blades. The packing strip 2| is preferably sharpened so that in the event of accidental contact between the sharpened edge 23 and the surface I8, a minimum quantity of heat will be generated and so that it may readily wear down for defining a relatively close clearance.

The shroud M of the stationary blades I2 is externally rabbeted or channeled, as shown at 24, to'receive the circumferentially-extending packing strip 25. The strip 25 is shown connected to the shroud l5 by rivets 263. The packing strip 25 extends downstream and cooperates with the radial surface I9 to define relatively close clearance with respect to the latter to limit leakage of steam around the tips of the stationary blades I2 and into the space between the stationary and moving blades. Here again the packing strip has its outer edge sharpened, as indicated at 27, so that it may readily wear to define relatively close clearance and not generate excessive quantities of heat in the event of accidental rubbing.

The stationary blade row shroud I4 extends downstream beyond the packing strip 25 to provide an annular deflector 28, which functions to deflect steam entering between the edge 21 and the radial surface I9 from a radial to an axial direction of flow, thereby causing such leakage to join the main stream of axially-flowing steam and avoiding losses due to cross flow and turbulence.

From the foregoing, it will be apparent that the packing strips act effectively to minimize leakage losses. As the packing or sealing strips are formed separately from the shrouds, a more suitable material for each may be selected. Furthermore, the packing strips are related and connected to the shrouds so as to secure operation to the best advantage: the rotatable strip is carried internally of its shroud so that the shroud withstands the centrifugal load of the strip and the rivets serve simply as fastening means between the strip and the shroud; and, by having the strips arranged to fit in channels, it is assured that the strips may be correctly placed to define the proper clearances. Since the strips are formed separately from the shrouds and are connected to the latter by rivets, they are readily replaceable, it being merely necessary to remove a strip and its rivets and rivet on a newstrip, the rivets and channels serving, as already pointed out, to assure 'properlocation of the wearing strips. I 7

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications, without departing from the spirit thereof, and'I desire, therefore, that only such limitations, shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What Iclaim is:

1. In a turbine, a stator, a rotor, stationary and moving blades carried by the stator and by the rotor, respectively, shrouds connected to the tips of the blades, means providing radial surfaces adjacent to the roots of the blading at the down-stream and up-stream sides of the stationary and moving blades, respectively, each stationary blade row shroud being externally rabbeted or channeled at the down-stream side, a circumferential packing strip fitting said rabbet or channel and extending toward the radial surface at the up-stream side of the cooperating moving blades to define relatively close clearance, each moving blade row shroud being internally rabbeted or channeled at the up-stream side, a circumferential packing strip fitting the channel or rabbet of the moving blade row shroud and extending toward the radial surface at the down-stream side of the cooperating succeeding stationary blades to define relatively close clearance, the moving blade packing strip being of a. thickness substantially equal to the moving blade shroud channel or rabbet radial depth, whereby, with the strip in position, the internal surfaces of the shroud and strip are flush, and rivets for connecting the packing strips to the shrouds.

2. The combination as claimed in claim 1 wherein the packing strips are provided with sharpened outer edges.

3. In a turbine, a stator, a rotor, stationary and moving blades carried by the stator and by the rotor, respectively, shrouds connected to the tips of the blades, lateral packing elements providing radial sealing surfaces adjacent to the root portions of the stationary and moving blades at the down-stream sides of the stationary blades and at the up-stream sides of the moving blades, each stationary blade shroud being channeled or rabbeted externally and at the down-stream side, a circumferential packing strip fitting said channel or rabbet and extending down-stream. to cooperate with the radial sealing surface adjacent to the roots of the cooperating moving blades to define relatively close clearance, the moving blade row shroud being channeled or rabbeted internally at the up-stream side, a circumferential packing strip fitting the last-named channel or rabbet so that its internal surface is flush with the internal surface of the moving blade shroud and extending up-strBam to cooperate with the radial sealing surface adjacent to the roots of the cooperating stationary bladesvto define relatively close clearance, the stationary blade row shroud having its down-stream side extending down-stream so as to circumferentially overlap the packing element at the up-stream side of the cooperating moving blade row to deflect steam entering radially between the stationary blade row packing strip and its cooperating radial surface for flow in an axial direction through the cooperating moving blades, and rivets for connecting the packing strips to the shrouds.

.HAROLD ,V. RASMUSSEN.