US1922017A

US1922017A - Elastic fluid turbine

Info

Publication number: US1922017A
Application number: US638416A
Authority: US
Inventors: Henry L Guy
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1931-10-27
Filing date: 1932-10-18
Publication date: 1933-08-08
Anticipated expiration: 1950-08-08

Description

Patented Aug. 8, 1933 UNITED STATES PATENT orriciz Electric Company, a Corporation of a York New Application October 18, 1932, Serial No. 638,416,

and in Great Britain October 2'7, 1931 5 Claims.

The present invention relates to elastic fluid turbines which are provided with packings for preventing elastic fluid from leaking past these packings into the atmosphere as regards the high pressure end of the turbine and for preventing air or like medium from leaking into the turbine as regards the exhaust end thereof. These packings may be labyrinth packings or a combination of labyrinth packings with a water seal, the water seal comprising usually an impeller or disc on the turbine shaft located and running in a housing to which water is supplied. In case a water-sealed packing is provided, the space surrounding the rotor shaft between the labyrinth packing and the water-sealed packing is connected usually to the condenser or to the exhaust outlet, the fluid pressure in which is lower than atmospheric pressure so that under normal conditions of operation any elastic fluid generated by the evaporation of the water in the impeller housing becomes mixed with elastic fluid leaking through the labyrinth gland and is withdrawn from the turbine. However, when the elastic fluid pressure in the turbine cylinder falls below the pressure exerted by the elastic fluid generated in the impeller housing, as for example might occur at very light loads, particularly when starting up or shutting down the turbine, the elastic fluid generated in the housing will tend to leak through the labyrinth packing and as regards the high pressure end enter the space between the flrst diaphragm and the wheel of the first turbine stage. The elastic fluid thereby comes into contact with the first turbine wheel and owing to the comparatively low temperature of this elastic fluid causes cooling of the inner parts of the wheel, efiecting an unequal temperature distribution of the different portions of the wheel. The wheel thereby is liable to warp and to assume a saucer-shape whereby the periphery of the wheel eventually touches and injures the diaphragm. In case the turbine is provided with a labyrinth packing only, such as a toothed packing, cool air may be drawn into the turbine during light load conditions and may impinge on one side of the interior portion of the bucket wheel, causing warping of the wheel.

The object of my invention is an improved turbine construction whereby the quantity of relatively cool steam or air which leaks past the labyrinth packing or packings and comes into contact with a bucket wheel is considerably minimized. According to my invention I provide means defining a channel for conducting air or like medium leaking past the labyrinth packing into the interior of the turbine towards an outer portion of the first bucket wheel as regards the inlet side of the turbines For a better understanding of what I consider to be novel and my invention, attention is directed to the following description and the claims appended thereto in connection with the accompanying drawing which forms a part of the speciprovided ahead of the bucket wheel for directing elastic fluid to the latter. The diaphragm is held in recesses 13 of an outer casing l l. A ring 15 shrunk onto the shaft serves for preventing axial movement or the bucket wheel 10. A packing or seal 16 between the inner periphery of the diaphragm and the ring prevents leakage of elastic fluid from a space 17 defined between the diaphragm and the bucket wheel and a chamber 18 defined by a labyrinth or like packing'19 and the adjacent turbine parts. The labyrinth packing 19 has been shown by way of example as a toothed packing comprising an inner member 20 fastened to the shaft and an outer member 21 concentrically arranged with the inner member and held by the outer casing 14: by means of bolts 22. The arrangement so far described is typical of any kind of turbine construction. During normal operating conditions slight leakage of elastic fluid may take place from the space 17 between the bucket wheel and the diaphragm past the seal 16 and the labyrinth packing 19. It has been the practice to further minimize this leakage by the provision .of a water seal adjacent to the packing 19. It

will be noted that under ordinary operating conditions, that is at normal load conditions, leakage takes place from the interior of the turbine to the atmosphere or, in case a water seal is provided, to the seal and from there to the condenser with which the water seal usually communicates. At light load and no load, such as occur during starting conditions and when the turbine is shut down, the elastic fluid pressure in the first stage, particularly in the space 17 between the bucket wheel and the diaphragm, may drop to a value below atmospheric pressure, to the effect that now leakage may take place from the exterior of the turbine past the packings 20 and the sealing means 16 into the space 17. The medium thus entering the space 1'! is either .air or steam in case of the provision of a water seal.

This medium comes into contact with the inner portion of the bucket wheel and having a lower temperature than said bucket wheel portion causes cooling of the inner portion, resulting in warping of the wheel.

According to my invention I provide means defining passages for conducting a medium leaking into the turbine to the outer portion of the bucket wheel, or, from another viewpoint, I provide means defining passages between the packing chamber and an outer portion of the bucket wheel which offer less resistance to the flow of leakage fluid into the turbine than the path offered by the space 17 past the sealing means 16 between the diaphragm and the rotor.

In the embodiment illustrated in the drawing I have shown a diaphragm 12 having a large annular recess in which is located an annular plate or member 23 defining with the diaphragm a space or passageway 24. The plate is held in recesses 2-5 and26 of the diaphragm and fastened thereto by rivets 27. Spacers 28 are provided near the riveted portions for securing a definite spacing between the diaphragm and the member 23. The innerpart of the space 24 communicates with the packing chamber 18 through

channels

31 and 32 in the diaphragm. The outer portion of the space 24 communicates through apertures 29 in the member 23 with space 1'7 near the outer portion of the bucket wheel.

With the arrangement above described leakage fluid entering the turbine past the packing 19 during light or no load conditions is conducted through the passages or

channels

32 and 31 the space 24 and the apertures 29 to an outer .portion of the bucket wheel where the lower temperature of this medium has little effect on the bucket wheel. The leakage is conducted through

passages

32, 31, 24, 29 owing to the fact that the hydraulic resistance of these passages is much "smaller than the hydraulic resistance past the sealing means 16 into the space 17. Thus, with my invention I have accomplished a simple and reliable arrangement for preventing a comparatively cool medium from impinging on the inner hot portion of the bucket wheel.

From another angle, my invention comprises the provision of a member 23 between the diaphragm 12 and the bucket wheel 10 for. defining two

spaces

17 and 24. The space 1'? between the bucket wheel 10 and the member 23 is sealed by the sealing means 16 to minimize the amount of leakage through this space whereas the other space 24 defined between the diaphragm 12 and the member 23 communicates through the

channels

31 and 32 with the packing chamber 18 at one end and at the other end through the apertures-29 with an outer portion of the bucket wheel. The direct communication between the outer portion of the bucket wheel and the packing chamber 18 offers little resistance to the flow of leakage fluid compared with the high hydraulic resistance between the packing chamber 18 and the space '17 past the sealing means 16 between them.

Having described the method of operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof, I desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means. What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In an elastic fluid turbine, a shaft, a bucket .wheel fastened to the shaft, a casing, a diaphragm for directing elastic fluid to the wheel and supported by the casing, a packing between the shaft the casing, a sealing means between the diaphragm and the shaft, and means including said sealing means for preventing a medium leaking past the packing into the turbine from coming into contact with the inner portion of the wheel.

2. In an elastic fluid turbine, a shaft, a bucket wheel fastened to the shaft, a casing, a diaphragm for directing elastic fluid to the wheel and supported by the casing, a packing between the shaft and the casing, a sealing means between the diaphragm and the shaft, and means providing a path of "less hydraulic resistance than the path past said sealing means for conducting a medium leaking past the packing into the turbine towards an outer portion of the bucket wheel.

3. In an elastic fluid turbine, a shaft, a bucket wheel fastened to the shaft, a casing, a labyrinth packing between the casing and the shaft defining a chamber, a diaphragm for directing elastic fluid to the bucket wheel and being supported by the casing, 21. member intermediate the diaphragm and the bucket wheel being held by the diaphragm and defining two annular spaces, a seal for preventing fluid from leaking past the labyrinth packing into the space between the member andthe wheel, there being a passageway between said chamber and an outer portion of the bucket wheel which passageway includes the space between the diaphragm and the member.

4. In an elastic fluid turbine, a shaft, a bucket wheel fastened to the shaft, a diaphragm having a recessed'portion, a sealing means between the diaphragm and the shaft, a casing supporting the diaphragm, a packing between the shaft and the casing defining a chamber, a plate in the recessed portion of the diaphragm defining a space with the latter communicating with the packing chamber and defining apath of low resistance to the flow of leakage fluid from the packing chamber to the outer periphery of the bucket wheel whereby fluid-leaking into the turbine past the labyrinth packing does not come into contact with the inner portion of the bucket wheel.

5. In an elastic fluid turbine, a shaft, a casing, a packing between the shaft and the casing, bucket wheel fastened to the shaft, a member adjacent the bucket wheel, a sealing means between the member and the shaft, there being passages defined partly by the member for conducting fluid leaking past the packing into the turbine to an outer portion of the bucket wheel, said passages offering less hydraulic resistance to the flow of fluid than the passage past the sealing means.

HENRY L. GUY.