US2855178A - Turbines - Google Patents

Description

TURBINES 3 Sheets-Sheet 1 Filed July 12, 1955 G. H. FORSYTH ET AL @cfi. 7, 1958 TURBINES 3 Sheets-Sheet 2 Filed July 12, 1955 N QEW United States Patent cc TURBlNES George Howard Forsyth and George Wood, London, England, assignors to Vickers-Armstrongs (Engineers) Limited, London, England Application July 12, 1955, Serial No. 521,542 Claims priority, application Great Britain July 14, 1954 4 Claims. (Cl. 253-69) This invention relates to turbines.

According to the present invention there is provided a turbine having a rotor, a first casing around the rotor, a nozzle box having nozzles for directing driving fluid at the first ring of blades on the rotor, there being a first inlet for delivering driving fluid to the nozzle box, and a second casing around the nozzle box, the second casing having a second inlet for receiving fluid to pressurise the outside of the nozzle box.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made to the accompanying drawings, in which:

Figure l is a sectional elevation of a turbine,

Figure 2 is. a sectional elevation of a modification of the turbine of Figure 1,

Figure 3 is a sectional elevation of a further turbine, and

Figures 4 and 5 are sectional views of details of the turbine of Figure 3.

Each turbine is intended to be used as the economy turbine of an installation as described in our co-pending application Serial No. 521,522, filed July 12, 1955, which corresponds to our British patent application No. 20,598/54.

The turbine 1 of Figure 1 is of the axial flow kind and has an over-hung rotor 2. The rotor 2 has two rings 3 of blades and is carried on one end of a shaft 4 that passes through a gland 5 in an inner part 6 of the turbine casing. The shaft 4 is integral with, or is connected coaxially to, the spindle 7 of the ahead turbine 8 of the installation described in said co-pending application. A bearing 9 supported by the casing of the ahead turbine 8 is provided between the two turbines 1 and 8 for supporting the shaft 4.

The inner part 6 carries a single ring 10 of blades which are located between the two blade rings 3 on the rotor 2. A nozzle box 11 of annular form and carrying nozzles 12 is located adjacent the first ring 3 of blades on the rotor 2, this first ring 3 being at the end of the rotor 2 remote from the gland 5. The nozzle box 11 is secured to the inner part 6 of the casing of the economy turbine. The opening 13 through the centre of the nozzle box 11, which opening 13 is adjacent the free end of the rotor 2, is closed by a dished plate 14 secured to the nozzle box 11. The nozzle box 11, plate 14 and that portion 6A of the inner part 6 of the turbine casing that surrounds the rotor 2 is enclosed by an outer part 15 of the turbine casing. The outer part 15 is secured to the inner part 6. The outer part 15 has an inlet 16 at the bottom thereof and an outlet 17 at the top thereof. An inlet 18 to the nozzle box 11 passes through the outlet 17. The inner part 6 of the turbine casing has an annular space 19 adjacent the second ring 3 of blades on the,

rotor and this space 19 communicates with an outlet 20. The inlet 16 is connected to receive steam from the change-over valve (not shown) of said installation, and

the outlet 17 is connected to the inlet to the independently" fired superheater (not shown). The outlet of the superheater is connected to the inlet 18 to the nozzle box 11, and the outlet 20 is connected to the inlet of the ahead turbine 8. A valve control by-pass arrangement (not shown) may be connected across the inlet 16 and outlet 17. .1

In operation steam from the change-over valve flow: through the outer part 15 around the outside of the nozzle box 11 and around the outside of the portion 6A of the inner part 6- of the casing. Steam from the superheater and at a higher temperature and slightly lower pressure than the steam passing through the outer part 15 of the casing is fed to the nozzle box 11 and after passing through the blade rings 3 into the annular space 19 flows through the outlet 20 to the ahead turbine 8. In cases where the by-pass arrangement is provided the quantity of steam flowing through the outer part 16 of the casing can be made any desired fraction (including zero) of the quantity of steam passing through the superheater to the nozzle box 11. This makes it possible to prevent the cooling of the nozzle box 11 by the steam passing through the part 15. Such cooling of course reduces the temperature of the steam within the nozzle box. Alternatively the nozzle box 11 may be screened with light gauge sheet material (not shown) to minimise the heat flow through the walls of the nozzle box 11.

It will be understood that with the turbine construction described above, the only gland in the turbine is subjectedonly to the exhaust pressure of the economy turbine. 5

In a modified form of the turbine described above the rotor shaft 4, as shown in Fig. 2, is coupled through gearing (not shown) to the propeller shaft (not shown) of the installation instead of being integral with or connected to the spindle of the ahead turbine. The shaft 4 is supported adjacent the gland 5 of the economy turbine 1 by two journal bearings 21, 22 having a thrust bearing 23 therebetween. The shaft 4 has a collar 24 thereon which co-operates with thrust pads 25 incorporated in the same casing 26 as the two journal bearings 21, 22.

The turbine of Figure 3 is of the axial flow type and has a rotor 27 which carries five rings 28 of blades. The

rotor 27 is enclosed by an inner cylindrical casing 29 to the outlet of the independently fired superheater (not shown) of the installation. The inner casing 29 and nozzle box 31 are enclosed by an outer casing 34 which has an inlet 35 for connection to the change-over valve (not shown) of said installation and an outlet 36 for connection to the inlet of the independently fired superheater. The inlet 33 to the nozzle box 31 passes through the outlet 36. The low pressure end of the inner casing 29 has an outwardly directed flange 37 and the periphery of the flange 37 abuts against an inwardly directed flange 38 on the outer casing. The low pressure end of the easing 29 is closed by an end member 39 that abuts against the low pressure end of the outer casing 34 and the flange 37. The end member 39 has an annular space 40 to which working fluid passes from the rotor 27. The space 40 communicates with an outlet 41 connected to the inlet of the ahead turbine (not shown) of said installation.

The rotor 27 is carried on a shaft 42 which passes through a gland 43 in the end member 39 and a gland 44 located in a boss 45 formed at thehigh pressureend of the outer casing 34. The gland 44 is carried in a sleeve 46 mounted in the boss 45. The sleeve 46 has Ramsbottom rings 47 around the outer periphery thereof, the rings 47 allowing the sleeve 46 to slide along the inner surface of the boss 45. The inner end of the sleeve 46 is encircled by the nozzle box 31 and has an outwardly directed flange 48 which co-operates with an inwardly directed flange 49 on the nozzle box 31. The flange 48 lies between the rotor 27 and the flange 49. The nozzle box 31 has an outwardly directed flange 50 around the outer periphery thereof and this flange t? co-operates with the rim 51 of the high pressure end of the inner casing 29.

A joint between the flange 48 and the flange 49 is formed by a first H-sectioned ring 52. A joint is formed between the rim 51 and the flange 50 by a second H-sectioned ring 52. The two rings 52 connect surfaces that are perpendicular to the axis of the rotor 27. Each of the H-sectioned rings 52 is formed such that the uprights of the H-section are parallel to the axis of the rotor 27. The rings 52 are made of ductile material such as mild steel. A groove 53 (Figure 5) is formed in each flange and in the rim for receiving two adjacent legs 54 of the uprights of the associated H-sectioned ring 52. Each groove 53 diverges as it becomes deeper and a wedge 55 for fitting between a pair of adjacent legs 54, is placed in the bottom of each groove 53 so that when the ring 52 is placed in the grooves 54 of the parts to be joined together and these parts are forced towards each other, the wedges 55 cause adjacent legs 54 to be forced apart so that the H-section spreads out into a dovetail form. If the wedge angles are small it will be appreciated that the joints can only be broken by cutting through the rings 52 at the centre thereof. This disadvantage can be avoided by forming one of the wedges (the wedge 56 in Figure 4) co-operating with each ring integrally with the part into which the ring 52 is fitted. When assembling the rings into the grooves, jointing material 57 may be placed at the bottom of the grooves 53 on either side of the wedges 55.

A controlled by-pass arrangement (not shown) and similar to that described in connection with Figure 1, is connected across the inlet 35 and outlet 36.

In operation of the turbine described above in connection with Figs. 3, 4 and 5 steam from the changeover valve passes through the inlet 35 of the outer casing 34, around the nozzle box 31 and the inner casing 29 and thence to the superheater. Superheated steam from the superheater passes to the nozzle box 31, through the five stages of the turbine and thence to the annular space 40 from which it is conveyed to the ahead turbine of the installation.

Since the outer periphery of the inner end of the sleeve 46 is joined to the nozzle box 31 and this sleeve 46 carries the gland 44 at the high pressure end of the turbine, it will be appreciated that this gland 44 is subjected only to the pressure of the steam leaving the nozzle box 31 and not to the pressure of the steam in the outer casing 34.

By appropriate dimensioning of the parts described, the loads on the H-sectioned jointing rings 52 can be made almost equal and in this way the stress in the nozzle box 31 due to steam thrust is minimised.

We claim:

1. In a turbine having inlet and discharge ends for the driving fluid and including a shaft and a rotor carried by the shaft having a plurality of rings of turbine blades, a first casing surrounding the periphery of the rotor, a nozzle box attached to said casing and having nozzles for directing the driving fluid against the first ring of turbine blades on the rotor, an inlet connection for supplying a driving fluid at a high pressure and temperature to the nozzle box, a second casing extending around the nozzle box in spaced relation, an inlet connection to said second casing for supplying fluid to the space between the nozzle box and the second casing, a gland at each end of the rotor through which said shaft extends, a sleeve surrounding the shaft at the inlet high pressure end of the turbine and in which the gland at the inlet end is mounted, said sleeve being carried by the second casing, an inwardly-directed flange on the inner perpihery of the nozzle box, an outwardly-directed flange on the inner end of the sleeve located between the rotor and said inwardlydirected flange on the nozzle box, and fluid-tight sealing means securing the two flanges together so that the gland in the sleeve is not subjected to the fluid in the second casing, the fluid in the space between the nozzle box and the second casing being at a higher pressure and lower temperature than that supplied through the inlet connection to the nozzle box, whereby excessive stresses are prevented on the nozzle box due to the high pressure of the driving fluid at the high temperature at which it is supplied to the nozzle box.

2. In a turbine having inlet and discharge ends for the turbine driving fluid and including a shaft carrying a rotor having a plurality of rings of turbine blades, a first casing surrounding the periphery of the rotor, at least a portion of said shaft extending beyond the rotor at the inlet end of the turbine, a nozzle box surrounding the shaft at the inlet end of the turbine and having nozzles for directing the driving fluid against the first ring of turbine blades on the rotor, means for securing the nozzle box and casing together in a fluid tight sealing relationship, an inlet connection for supplying a driving fluid to the nozzle box, a sleeve surrounding the shaft at the inlet end of the turbine, a gland mounted in said sleeve around the shaft, means for securing the inner end portion of the sleeve in a fluid-tight sealing relationship to the inner peripheral portion of the nozzle box, at least one of said securing means comprising a generally H-section ring, the pairs of the adjacent legs of which are secured respectively in a groove provided in the nozzle box and a facing groove provided in one of the elements consisting of the said sleeve and the first casing, the legs of each pair diverging from the central portion of the H-section ring, a wedge located in the groove between each pair of the diverging legs of the H-section ring, a second casing surrounding the nozzle box in spaced relation thereto and extending around said sleeve in sealing relation therewith and an inlet connection with said second casing for supplying a pressurizing fluid to the space between the nozzle box and the second casing.

3. A turbine as claimed in claim 2, wherein the wedge in one of the grooves and extending between one pair of legs of the H-section ring is integral with one of the elements consisting of the nozzle box, the sleeve and the first casing.

4. In a turbine having inlet and discharge ends for the turbine driving fluid and including a shaft carrying a rotor having a plurality of rings of turbine blades, a first casing surrounding the periphery of the rotor, at least a portion of said shaft extending beyond the rotor at the inlet end of the turbine, a nozzle box surrounding the shaft at the inlet end of the turbine and having nozzles for directing the driving fluid against the first ring of the turbine blades on the rotor, means for securing the nozzle box and easing together in a fluid tight sealing relationship, an inlet connection for supplying a driving fluid to the nozzle box, a sleeve surrounding the shaft at the inlet end of the turbine, a gland mounted in said sleeve around the shaft, an outwardly-extending flange on the inner end of the sleeve, an inwardly-extending flange on the inner peripheral portion of the nozzle box overlapping the flange on the sleeve, a sealing ring concentric to the axis of the rotor the respective ends of which are fluid tight with respect to and secured in said flanges thereby sealing and securing the inner end portion of the sleeve to the inner peripheral portion of the nozzle box, a second casing surrounding the nozzle box in spaced relation thereto and extending around said sleeve in sealing relation therewith, and an inlet connection with 1,825,580 said second casing for supplying a pressurizing fluid to 2,425,177 the space between the nozzle box and the second casing. 2,717,118

References Cited in the file of this patent 5 UNITED STATES PATENTS 904,512

1,714,893 Smith May 28, 1929 Collingham Sept. 29, 1931 Cronstedt Aug. 5, 1947 Walter Sept. 6, 1955 FOREIGN PATENTS France Nov. 8, 1945

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