US2220616A

US2220616A - Packing for steam turbines

Info

Publication number: US2220616A
Application number: US128187A
Authority: US
Inventors: Roder Karl
Original assignee: Individual
Current assignee: Individual
Priority date: 1936-02-29
Filing date: 1937-02-27
Publication date: 1940-11-05
Anticipated expiration: 1957-11-05

Description

Nov. 5,

K. RODER f 2,220,616 PACKING FOR STEAM TURBINES I Filed Feb. 27, 1957 5 Sheets-Sheet l Nov-5,1940. A'K DgR v2,220,616

PACKING FOR STEAM TURBINES' Filed Feb. 27, 1957 5 Sheets-Sheet 2 K. RGDER l PACKING FOR STEAM :umanms Filed Feb. 27, i937" Nov. 5; 1940.-

5 Sheets-Sheet 3 Nov. 5, 1940 K. RODER PACKING FOR STEAM TURBINES' Filed Feb. 27, 1937 5 Sheds-Sheet 4 Patented Nov. 5, 1940 UNITED STATES 2,220,616 PACKING FOR. vSTEAM TURBINES Karl Riider, Hanover, Germany Application February 27, 1937, Serial No. 128,18 In Germany February 29, 1936 My invention relates to improvements in packings for steam turbines.

The efllciency and reliability of a steam turbine depends to a great extent upon the packings employed therefor. This applies particularly to machines dealing with small volumes of steam, for instance, also to high-pressure parts of highpressure turbines.

Inthe labyrinth packings with projecting edges which are employed in most cases, a circular sectional area of flow of small depth, namely the depth of the clearance space, is left between the revolving part and the stationary part enclosing the same, which parts should not come into con- 5 tact with one another.

This depth of the clearance space should be as small as possible and should remain of the same magnitude over the entire periphery independently of the variation in pressures and tempera- 20 tures of the operating fluid during the operation. It is theoretically possible to maintain the clearance space as above mentioned strictly equal onlyin the case in which both elements defining the clearance space present exactly the same 25 operating conditions, such as is the case with packings between the blade rims of turbines with nozzles and blades rotating-in opposite directions.

All other packings, that is to say, the other packings employed in turbineswithnozzles and 30 blades rotating in opposite directions as well as when employing packings of the usual type 2 40 only the revolving part retains its circular shape under all operating conditions, whereas the stationary part loses its circular shape and cannot adapt itself, without producing mechanical stresses, to thevarying. temperatures, thereby 45 causing a reduction of the clearance space which impairs the reliability of operation.

The object of my invention is: to remove the above-mentioned drawbacks, i. e., to design and to assemble the stationary parts of an expansion 50 or compression machine (by which are denoted steady flow machines working on the expansion principle, or on the compression principle, 1. e., turbines, or compressors, respectively) in such a manner I 55 (1) That the annular clearance space retains its circular shape under all operating conditions; (2) That the expansion and contraction of the parts bounding the clearance space essentially produce enlargements of the clearance space only consequently, and 5 (3) That the temperature and pressure variations do not entail any appreciable decrease of the clearance space so that the danger of contact of the movable parts is eliminated. To this end, it is above all necessary that the 10 unavoidable departures of the machine casing from the circular form or from symmetry occurnot only on one side but symmetrically on opposite sides of the central axis, and that both casing parts have the same shape and the same dimensions in planes transverse to the longitudinal axis of the casing.

The invention is illustrated in the accompanying drawings, in which- I Figs. 1 and 2 are explanatory figures, and represent respectively in side and end elevation an unsymmetrical structure, showing the distortion in dash lines, resulting from uneven expansion under the influence of heat and pressure.

Figs. 3 and 4 represent respectively in side and 'end'elevation a symmetrical structure according to the present invention, showing in. dash lines the symmetrical expansion under the influence v v of heat and pressure.

Figs. 5 to 10 show in sectional elevation diflEercut forms of resiliently supporting the stator ring to prevent the transmission of unavoidable casing distortions to the ring. 4

Fig. 7a is a transverse section through Fig. 7 on the line l in Fig. '7, and

Fig. 11 represents a steam temperature graph at dififerent'loads of a three-stage turbine. I

Referring to Figs. 1 and 2, these figures show a typical form ofan unsymmetrical machine casing A, having the connecting branches B and 40 C located all on one side of a given central axial plane. The deformations of the casing, and also of its axis when subjected to high temperatures in operation, are unsymmetrical, as indicated in dash lines. 5

Figs. 3 and 4 show in side and end elevation respectively the novel construction of a steam turbine casing in which correspondingly located points of thecasing on diametrically opposite 1 sides 0! the longitudinal central axis depart from the circular shape to the same extent (for instance, B, B; C, C), and in which the central axis D does not become dislocated or distorted. In other words, the unavoidable deformations of the casing are symmetrical with respect to the central axis within all transverse sections of the casing.

While deformations of the casing are in this case not avoided, the axis of the casing is not deformed or shifted by these changes.

Furthermore those parts which support the guide blades and the stationary packing elements-even if these parts are subdivided in a plane through the longitudinal axis-should be made in the form of bodies of revolution with respect to the casing axis, whatever their contour may be in the direction of the axis, and be mounted in the casing in such a manner that they may follow the changes in temperature as free bodies of revolution without loosing their circular shape.

To this end, such bodies of revolution may be supported by other bodies of revolution which are concentrically mounted in the casing or assembled therewith so as to permit a symmetrical expansion or contraction thereof in response to the temperature changes.

Referring first to Fig. 5, b represents in cross section one-half of the revolving part or rotor of the turbine which, of course, in itself is a body of revolution. The rotor carries the rotor blades 1'. In the turbine casing c, which may be of the general symmetrical character as shown in and described with reference to Figs. 3 and 4, is mounted the stator support d" which is annular and thus also constitutes a body of revolution. Support d" is shaped at one and d into a clamping ring and carriesat the other end a separate clamping ring d. Between these two clamping bodies of revolution is positioned the turbine stator a which carries the stator blades 3 and is in itself also a body of revolution. By this arrangement complete symmetry is maintained so that no distortion, due to uneven heat expansion located in the upper half of the casing c and the other half of the elements is located in the lower half of casing c. When these halves are assembled they act as complete bodies of revolution and expand and contract symmetrically. This two parts, for instance, four parts, provided the division lines are on planes through the longitudinal turbine axis.

The form of the different bodies of revolution of which the entirestator is composed as aforethe design requirements. For instance, as shown in Fig. 6 at d1, (12, the clamping elements for the stator ring a may be composed of two parts, each a body of revolution, and may hold the stator ring between them at its ends and at an annular rib a disposed intermediate its ends. Further, as shown in'Fig. 7, the stator ring a may be held by clamping rings d1, dz, as shown in Fig. 6, between one of its ends and its middle, and its freely extending end may be held by a clamping ring 0' provided at an annular extension c" of casing c.

holds one end of the stator ring a by means of a ring 0' at the end of an annular portion c" of casing C in a manner similar to that shown in Fig. 7. The other end of stator ringa is supported by an annular support t carried by the outer casing portion is through arms t'. The portion of stator ring a intermediate its ends is held by an annular rib k on casing portions k, whereby it is also prevented from longitudinal shifting.

Fig. 9 shows a construction similar to Fig. 8, except that one end of the stator ring a is carried by a separate supporting ring m mounted in the casing portion C.

Fig. 10 shows the support of stator ring a at one end by means of a clamping ring dz attached by means of arms (is and a base ring d4 to casing c. The other end of stator ring a is held by clamping ring c' supported similar to the manner shown in Fig. 7, and the stator ring a is supported intermediate its ends by a rib a held between base ringd4 and a shoulder on casing c.

All of the holding or clamping rings for stator ring a, such as d, d in Fig. 5, d1, dz in Figs. 6 and.

'7, c in Figs. 7, 8 and 10, and t in Figs. 8 and 9,

arms extending substantially in parallel to the turbine axis so that this stator support is made sufficiently resilient in radial direction to prevent unavoidable defprmations of the outer casing from being transmitted to the stator ring a.

The changes in temperature in the several stages of a turbine to be expected may be seen from the graph, Fig. 11. It is assumed that the turbine under consideration be a three-stage turbine having a high pressure stage HD, a medium pressure stage MD, and a low pressure stage ND. The turbine is divided into three stages.

The temperatures at the beginning and the end of these three stages are plotted in Fig. 11 against the load conditions varying within wide limits. The high-pressure HD and the medium pressure stage MD are subjected as will be seen from Fig. 11 to great changes in the temperature of the operating medium only when starting, the temperature in this case increasing to a considerable extent from standstill to no-load running.

The changes in temperature during operation between no-load to full load and back to standstill are relatively slight so that these variations in temperature during starting are only fractions of the great increase in temperature.

The temperatures of steam are not identical with the temperatures of the machine parts of the different stages; nevertheless it may be concluded 'with certainty from Fig. 11 that the temdescribed may, of course, vary in accordance with peratures of the individual machine parts increase considerably during and after starting and vary only to a slight extent during operation.

in temperature occurring during operation should cause corresponding decrease of the clearance space, the latter being only a small percentage of the former.

These conditions are actually obtained by the arrangement of the stationary elements of the machine, such as the stator ring and its supporting elements in the manner shown in Figs. 5 to 10, in which they are exposed to the steam temperature so that they can respond more quickly to variations in temperature than the adjacent .and having a casing enclosing said stator and Consequently, an

increase in the clearance space is brought about when putting the turbine into operation and when taking up a load, i. e., under operating conditions which, in the designs followed hitherto, lead rather to decreases of the clearance by which the operation of the machine is endangered. In the present designs according to the invention, on the other hand, the decreases of the clearance space below that allowed during the mounting of the machine, which occur duringthe operation of the machine at different loads, are so slight as to be practically negligible. Thus, in-assembling the machine, the allowable clearance space between the moving elements may be made extremely small, and only the expansion oi! the rotor due to centrifugal forces need be taken into considerationior the amounts of these clearances. I

The material for the revolving and stationary parts which limit the clearance space should have about the same coeflicicnt of heat expansion. The dimensions, the wall thickness and the arrangement of the packing parts in the path of the flowing medium depend upon the above-mentioned method of designing steam turbines as will be seen from Figs. 5 to 10.

I claim as my invention:

1. A fluid expansion or compression machine having a casing and stator and rotor elements subject to expansion and contraction, said casing having all portions deviating from circularshape with respect to the'rotor axis arranged in pairs disposed symmetrically on diametrically opposite sides of said axis, and having its stator elements mounted within said casing and formed as bodies of revolution with respect to said rotor axis, said stator elements comprising an elongated stator blade carrier and a plurality of rowsof stator blades mounted directly on said carrier and being freely exposed to the varying temperatures of the operating'fluid and being disposed to tion disposed to hold said divided carrier together and to support it in said casing as a single body of revolution which retains its shape at Varying temperatures.

3. A steam turbine having a stator and a rotor rotor and being longitudinally divided in atleast one plane through the turbine rotor axis, said and having a casing enclosing said stator and .rotor and being longitudinally divided in at least one plane through the turbine rotor axis, said stator comprising a similarly divided stator blade carrier and a plurality of rows of stator blades disposed therein, said blade carrier being constructed as a body of revolution with respect to said rotor axis, and at least one body of revolution diametrically divided in a plane through said rotor axis but at right angles to the dividing plane of said carrier and disposed to hold said divided carrier together and to support it in said casing as a single body of revolution which retains its shape at varying temperatures.

5. A steam turbine having. a stator and a rotor and having a casing enclosing said stator and rotorand being longitudinally divided in at least one plane through the turbine rotor axis, said stator comprising a similarly divided stator blade carrier and a plurality of rows of stator-blades disposed therein, said blade carrier being con- .structed as a body of revolution with respect-to said rotor axis, said casing containing at least one elastically centered body of revolution disposed to hold said divided carrier together and to support it in said casing as a single bodyof revolution which, retains its shape at varying temperatures.

6. A steam turbine having a stator and a rotor and having a casing enclosing said stator and rotor and being longitudinally divided in at least one plane through the turbine rotor axis, said stator comprising a similarly divided stator blade carrier and a plurality of rows of stator blades disposed therein, said blade carrier being constructed as a body of revolution with respect to said rotor axis, and at least one body of revolution disposed to hold said divided carrier together and to support it in said casing as a single 'body of revolution which retains its shape at varying temperatures, said carrier and said supporting body being arranged in the path of the entering operating medium so as to follow its temperature variations faster than the rotor elements of the turbine.

7. A steam turbine having a stator and a rotor and -having a casing enclosing said stator and rotor and being longitudinally divided in at least one plane through the turbine rotor axis, said stator comprising a similarly divided stator bla'de carrier and a plurality of rows of stator blades disposed therein, said blade carrier being constructed as a body of revolution with respect to said rotor axis, and at least one body of revolution disposed to hold said divided carrier together and to support it in said casing. as a single body of revolution which retains its shape at varying temperatures, said carrier and said support- 8. A steam turbine having astator and a rotor and having a casing enclosing said stator and rotor and being longitudinally divided in at lea-st one plane through the turbine rotor axis, said stator. comprising a similarly divided stator blade carrier anda plurality of rows of stator blades disposed therein, said blade carrier being constructedas a body of revolution with respect to said rotor axis, and at least one body oirevoluplane into two half shells and constructed as a body of revolution, a plurality of rows of stator blades disposed in said carrier, ring members clamping the two halves of the carrier together and maintaining the circular form of the carrier when variations of the length of the carrier occur, said ring members comprising means engaging the casing in a plane perpendicular to the rotor axis and intermediate the ends of the carrier to support the carrier in the casing.

-KARL RGDER.