US2243959A

US2243959A - High-pressure turbine

Info

Publication number: US2243959A
Application number: US314133A
Authority: US
Inventors: Hertl Robert
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1940-01-16
Filing date: 1940-01-16
Publication date: 1941-06-03
Anticipated expiration: 1958-06-03

Description

Jime 3, 1941. R. HERTL 2,243,959

HIGH-PRESSURE TURBINE Filed'Jan. 16, 1940, 5 Sheets-Sheet 1 Flq. 1.

WITNESSES: grw

HERTL. BY

ATTORNEY June 3, 1941 I RHERTL 2,243,959

HIGH-PRESSURE TURBINE Filed Jan. 16, 1940 Sheets-Sheet 2 r] Ill INVENTOR ca ,M

ATTORNEY Fioaa'm' HER'TL.

June 3, 1941 R H T 2,243,959

HIGH-PRESSURE TURBINE Filed Jan. 16, 1940 5 Sheets-Sheet 3 WITNESSES: INVENTOR b Z Rosam- HERTL,

W 'fi BY ATTORNEY June 3, 1941. R. HERTL 2,243,959

HIGH-PRESSURE TURBINE Filed Jan. 16, 1940 s Sheets-Sheet 4 J ROBERT HERTL.

BY I

uam

3, ATTORNEY Patentecl June 3, 1941 HIGH-PRESSURE TURBINE Vania Application January 16, 1940, Serial No. 314,133

3 Claims.

My invention relates to steam turbines, more particularly of the high-pressure and high-temperature type, and it has for an object to provide apparatus of this character wherein the casing or cylinder is constructed so as to have greater uniformity of expansion and contraction in order to avoid distortion and the consequences thereof.

A further object of my invention is to provide a turbine casing having its high-pressure end approximately spherical in shape in order to secure uniform expansion and contraction, to provide more flexible bolting conditions, and to avoid distortion with possible destruction of steam tightness of the casing joint.

It has heretofore been common practice to design a turbine casing more or less in conformity with the outline of interior parts. Consequently, the casing has had corners or portions having abrupt changes in direction. For example, at the high-pressure end, a portion of the casing extending generally in an axial direction has been integrally joined with an inwardly-extending end wall portion, thereby producing a circumferential corner. As long as moderate temperature conditions prevailed, structures of this kind were satisfactory; however, with the current tendency toward substantially higher steam temperature and pressure conditions, trouble has been experienced on account of distortion due to the nonuniform temperature gradient and expansion with the result that join-ts have opened up and unfavorable bolting conditions have occurred. In accordance with the present invention, the casing is made spherical at the high-pressure end to avoid these objections.

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

Fig. l is a longitudinal, sectional view showing a turbine embodying the present invention;

Fig. 2 is a plan view of the apparatus shown in Fig. 1, with the casing cover removed;

Fig, 3 is a sectional view similar to Fig. 1 but showing a modified form of turbine having the invention applied thereto;

Figs. 4 and 5 are sectional views taken along Fig. 7 is a fragmentary sectional view showing the invention applied in connection with an impulse stage.

Referring now to the drawings more in detail, in Figs. 1 and 2, there is shown, at It, an axialflow elastic-fluid turbine of the reaction or full peripheral admission type and including a stator II and a rotor l2. Motive fluid is supplied to the turbine by the conduits it and i4 and it is exhausted therefrom through a conduit l5. The casing has a plurality of blade rings ll carrying rows of stationary blades l8 cooperating with rows of moving blades is carried by the rotor 52. The turbine is provided with the usual dummy structure or structures 2! and

glands

22 and 23 are arranged between the casing and the rotor at the high and low-pressure ends thereof, respec tively.

The casing H comprises high and low-pressure end portions or

zones

25 and 2?, respectively, and an intervening blade-bounding portion or zone 28. The high-pressure end portion 26 is spherically shaped, and the low'pre'ssure end portion 2? may or may not be spherical, depending upon temperature and pressure conditions.

As shown in Figs. 4 and'5, the casing H is comprised by upper and

lower halves

29 and 3% having mating flanges 3! and 5..., respectively, connected by bolts 33 to provide the casing'joint arranged in an axial plane of the rotor. The flanges and the bolt rows conform to the shape of the casing including the high-pressure spherical end portionZS.

The blade-bounding portion or zone 28 of the casing shown in, Figs. 1 and 2 is substantially cylindrical and it merges into or is continuous with the spherical highpressure portion '28.

As shown, the casing or cylinder wall diminishes in radial thickness from the high-pressure toward the lowpressure end, this being possible, with the preservation of the: same relative strength, because of the reduction in pressure of the steam due to expansion. 7

The turbine cylinder or casing is supported by means of feet 35 (Fig. 2) extending from the high-pressure and the low-pressure ends of the lower casing or cylinder portion Elli, the feet 35 being carried by pedestal or supporting structures 3%; through the intermediary of suitable keying and sliding constructions permitting relative movement of the casing with respect to the sup porting structure to provide for expansion and contraction. As is well known in the art, the correct relative position of the cylinder and of the rotor is maintained by a thrust bearing of the bearing arrangement, diagrammatically indicated at 38, and the casing cylinder is held with the vertical plane of its axis in the rotor axis by means of the vertical guides 37, Figs, 1 and between the casing or cylinder and the pedestal or supporting structures 36.

In Figs. 3, 4, and 5 there is shown a turbine similar to that already described except that the casing gradually flares or diverges in the direction of the exhaust or low-pressure end and steam connections are made thereto in such a manner as to provide for preservation of structural strength and greater uniformity of expansion and contraction due to temperature effects. As shown, the turbine has three zones of steam admission, namely, at 38, 39, and 48, respectively,

the zone at 38 being at the high-pressure end ahead of all the blading, and the zones at 39 and 453 being in communication with the blading at suitable expansion points along the latter.

Both the upper and the lower halves of the cylinder are provided with steam admission passages to produce a more symmetrical structural arrangement and more uniform expansion and contraction. Accordingly, the steam admission zones have steam admission passages which are symmetrically disposed both with respect to the axial plane of the casing joint and the axial plane at right angles thereto. The high-pressure zone, at 38, is supplied by two steam passages, there being one passage 45 for the upper half 29 of the casing and one passage 35 for the lower half thereof. The zone, at 39, is supplied by four steam connections, there being two connections 4! and t8 for the upper half of the casing and the two

connections

39 and 53 for the lower half thereof. As with the zone at 38, the zone, at 49, also has two connections, there being one connection 5| for the upper half of the casing and one connection 52 for the lower half thereof. It will thus be seen that, for the zone, at 39, each half of the casing is provided with two steam connections which are spaced apart circumferentially approximately the same arcuate distance as each thereof is spaced from the casing joint. By having two connections instead of one, the size of each is reduced, thereby, for the same Weight, preserving a better relation of structural strength, and a better steam flow and distribution of temperature effects on the structure is secured. By locating the

passages

45 and 36 for the zone, at 38, and the passages 5! and 52 for the zone, at 40, in the vertical plane of the axis, with the passages spaced approximately equal distances therefrom and to either side thereof, the strength of the casing is better preserved and the application of heating effects thereto is made in a distributed and symmetrical manner.

In Fig. 7, there is shown a turbine having a partial or full peripheral admission impulse stage 53 arranged ahead of the full peripheral admission bladin 5d, and, as is customary, the radius of the impulse stage is larger than that of the first stage of the succeeding stages of blading. While the casing Ila might have the bladebounding portion or zone made cylindrical, as in Figs. 1 and 2, I prefer to have the casing conform generally to the outline defined by the blading. To this end, the blade-bounding zone or portion 2811 includes a part 55 conforming to the blading 5 joined by a gradually curved portion 56 to a portion 57, which extends radially outward and then axially forward to encompass the impulse stage 53. In this embodiment, the high-pressure end portion 26a of the casing is similar in structure and principle to that already aaeaese described. In other words, the generally cylindrical portion of the casing at the inlet side of the impulse stage 53 merges into or is continuous with the spherical portion 26a.

As may be seen from the drawings, the highpressure end portion, 26 or 26a, has a spherical shape whose geometrical center falls on the turbine axis at the point of intersection thereof by a transverse plane close to the high-pressure side of the blading zone. In other words, the portion of the casing at the high-pressure end of the blading zone merges into the spherical portion so that such portions have the same radius with respect to a common center on the turbine axis.

The spherical high-pressure end portion of the casing affords several advantages. As the spherical portion of the casing and the immediate part of the blade-bounding portion thereof have a uniform radius with respect to a common center, the temperature gradient and expansion and contraction of the casing at the high-pressure end will be uniform in radial directions with the result that the casing may expand and contract with preservation of similarity and without distortion. As the flanges and bolt rows conform to the spherical shape, distortion of these parts forming the joint, with possible opening-up or destruction of fluid tightness, is avoided. Also, because of the spherical arrangement, the bolt stress, for the same bolt size and pitch, is reduced, with the result that more favorable bolting conditions prevail. With this arrangement, the bolt rows beginning at least at the highpressure end of the blade-bounding portion of the casing and extending near to the high-pressure gland 2! conform to the spherical shape without any sharp point of inflection, the change in direction being gradual and uniform at all points. Stated another way, the bolts at the high-pressure end of the blade-bounding zone are tangent to a surface of revolution which is continuous with a spherical surface with respect to which the bolts of the high-pressure end portion of the casing are tangent.

Furthermore, as shown in Fig. 3, the required steam admission may be made so as to preserve the symmetry of the structural arrangement so far as possible, thereby contributing further to the strength of the structure and a better distribution of temperature effects thereon.

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

What I claim is:

1. In an axial-flow, elastic-fluid turbine, a rotor, a casing for the rotor, said casing including upper and lower halves having flanges providing a joint in the horizontal plane of the rotor axis, rows of bolts for connecting the respective mating flanges, and stationary and moving blading carried by the casing and'by the rotor; said casing including a blade-bounding portion having the circumferential part thereof adjacent to the highpressure side of the blading merging into a spherical high-pressure end portion of approximately the same radius with the portions of the bolt rows for the flange portions thereof conforming thereto, said casing defining annular steam admission spaces ahead of the blading and at suitable expansion point or points along the latter, said upper and lower casing halves each having, for the first admission space, a steam admission passage approximately at the vertical plane of the rotor axis and having, for the second admission space, a pair of steam admission passages spaced from the respective adjacent joints and from each other approximately the same circumferential distance.

2. In an axial-flow, elastic-fluid turbine, a rotor, a casing for the rotor, said casing including upper and lower halves having flanges providing a joint in the horizontal plane of the rotor axis, rows of bolts for connecting the respective mating flanges, and stationary and moving blading carried by the casing and by the rotor; said casing including a blade-bounding portion having the circumferential part thereof adjacent to the high-pressure side of the blading merging into a spherical high-pressure end portion of approximately the same radius With the portions of the bolt roWs for the flange portions thereof conforming thereto, said casing defining first, second and third annular steam admission spaces arranged, respectively, ahead of the blading and at suitable expansion points along the latter, said upper and lower casing halves each having,

for the first and third admission spaces, respectively, a passage approximately at the vertical plane of the rotor axis and having, for the second admission space, a pair of passages spaced from the respective adjacent joints and from each other approximately the same circumferential distance.

3. In an axial-flow, elastic-fluid turbine, a rotor, a casing for the rotor, and stationary and moving blading carried by the casing and by the rotor, said casing including a blade-bounding portion having the circumferential part thereof adjacent to the high-pressure side of the blading merging into a spherical high-pressure end portion of approximately the same radius, said casing having upper and lower halves defining annular steam admission spaces ahead of the blading and at suitable expansion points along the latter, and said upper and lower halves having steam admission passages communicating with said steam admission spaces and symmetri-' cally disposed with respect to the axial plane of the joint and the axial plane at right angles thereto.

ROBERT HERTL.