US2232852A - Turbine apparatus - Google Patents

Description

, Feb.25, 1941. s. H. HEMENWAY TURBINE APPARATUS Filed Sept 20, I 1939 m T N E V m SeYmun H.Hznsuwnz @MLM ATTORNEY Patented Feb. 25, 1941 UNITED STATES PATENT OFFICE TURBINE APPARATUS of Pennsylvania Application September 20, 1939, Serial No. 295,759

1 Claim.

My invention relates to mixed pressure turbines having high and low-pressure sections, wherein high-pressure steam is admitted to the high-pressure section for passage in series through the latter and the low-pressure section and wherein low-pressure steam is sup-plied to the low-pressure section, and it has for an object to provide improved means for ventilating the blading of the high-pressure section when the admission of high-pressure steam thereto is interrupted.

A mixed pressure turbine frequently should be operated so that, for any given load, the maximum possible amount of low-pressure steam is supplied to the low-pressure section in order to conserve high-pressure steam. Under certain load conditions, therefore, the steam requirements may be satisfied by the admission only of lowpressure steam to the low-pressure section, the supply of high-pressure steam to the high-pressure section of the turbine lbeing interrupted; however, under these conditions, the blading of the high-pressure section will be overheated unless steps are taken to insure ventilation. In accordance with the present invention, a conduit is arranged between the turbine exhaust connection and the interior space of the turbine at the high-pressure side of the blading of the highpressure section, a valve is arranged in the conduit, and the valve is controlled so as to be closed as long as high-pressure steam is supplied to the high-pressure section and to open upon the cessation of such supply. With the valve open, the conduit provides for backward flow of steam through the blading of the high-pressure section from the steam space between the high and lowpressure sections through the conduit to the exhaust connection, the steam so flowing absorbing heat from the blading and preventing the latter attaining an undesirably high temperature. Accordingly, a further object "of my invention is to provide, in connection with a mixed-pressure tur- 'bine, a by-pass passage extending from the highpressure side of the high-pressure blading to the exhaust connection and providing, when the supply of high-pressure steam is cut off, for the fiow of low-pressure steam baokwardly through the blading of the high-pressure section and then through the by-pass passage to ventilate such high-pressure blading.

A further object of my invention is to provide, in connection with a mixed-pressure turbine, a ventilating passage by-passing the blading of the high-pressure section and utilizing low-pressure steam flowing backwardly through the blading of the latter section when the supply of high-pressure steam is out ch. in order to ventilate the highpressure bladin'g to prevent overheating thereof, the by-pass passage having a valve constructed and arranged to provide the fiow area requisite to secure sufiicient steam for ventilating purposes.

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

The figure is a sectional view of a turbine incorporating the improved ventilating apparatus.

- Referring to the drawing more in detail, in the figure, there is shown :a mixed-pressure turbine, at H), having an exhaust connection 'I l and it includes a high-pressure section, at +2, and a lowpressure section, at 13, the high-pressure section having a high-pressure steam inlet I 4 and the low-pressure section having a low-pressure steam inlet 15. As shown, the turbine has interior spaces J6 and 1*! at the high-pressure and lowpressure sides of the high-pressure blading [8 of the high-pressure section and a diaphragm I9 is arranged between the space I! and the lowpressure section.

The admission valve '20 controlsthe flow of steam from the high-pressure steam inlet M to the high-pressure section. The low-pressure steam conduit or inlet is supplied from any suitable source and it preferably communicates with the interior turbine space I 7, and flow from the latter through the diaphragm 1 9 to the lowpressure section is controlled by a valve 2|. The high-pressure admission valve and the lowpressure :valve 2| are controlled, respectively, by servo-motors, at 22 and 23.

As shown, the turbine is provided with any suitable speed governor, at 24, having the usual speed changer apparatus including a speed changer motor 26, the governor controlling the servo-motor 22 and also, as hereinafter pointed out, exerting a controlling eifect on the servomotor, at 23. By suitable adjustment of the governor speed changer, the servo-motors are controlled so as to operate the valves '20 and 21 to utilize low-pressure steam in a preferential manner, that is, so long as the load requirements can be met by the low-pressure steam supply, the supply of high-pressure steam is cut off and the governor controls the valve 2| to admit lowpressure steam to the low-pressure section of the turbine suitably to the load requirements.

As shown, the servo-motor, at 23, in addition to being responsive to a controlling effect derived from the governor, is also influenced by the controlling effect provided by a suitable device, for example, the pressure regulator 26 associated with the exhaust connection, the arrangement being such that the exhaust steam pressure is held substantially constant with variation in the requirement for exhaust steam for any suitable purpose.

For example, the governor, at 24, is of the pressure transformer type providing a liquid pressure varying as a function of the speed of the turbine.

Also, the regulator '26 provides a liquid pressure which is a function of the steam pressure in the 5: exhaust connection I l. Liquid pressure provided by the governor is supplied to a passage 21 communicating with the pressure chambers 28 and 29 of the pressure-responsive devices 30 and 3| of the servo-motors, at 22 and '23, respectively. The pressure-responsive device 30 includes, for example, a movable abutment 132 connected to adjacent ends of the larger and smaller bellows elements 33 and 34, the bellows elements and the annular area 35 of the abutment forming a part of the boundary or enclosure of the pressure chamber 28.- Likewise, the pressure-responsive device 3| includes a movable abutment 31 connected to adjacent ends of the larger and smaller bellows elements 38 and 39 so as to separate the pressure chamber 29 from the pressure chamber 40, thereby providing an annular pressure area 4| exposed to pressure in the chamber 29 and the pressure area 42 exposed to pressure in the chamber 40. As already pointed out, the pressure chamber 29 is shown as being supplied by liquid under governing pressure while the chamber is supplied with liquid under pressure which is a function of the exhaust connection steam pressure; and, in consequence, .the valve 2| is operated in accordance with the difierential effect of liquid pressures supplied to said chambers.

To avoid overheating of the blading l8 of the high-pressure section when the supply of highpressure steam to the latter is interrupted, there is provided a ventilating conduit 45 connecting the interior space l6 of the turbine at the highpressure side of the blading l8 to the exhaust connection II and a valve 46 is arranged in the 401 conduit. Assuming that the supply of highpressure steam to the high-pressure section is interrupted. and that low-pressure steam is being supplied to the low-pressure section and that the valve 46 is open, then steam may flow back- 45 wardly from the interior space I! of the turbine through the high-pressure blading IE to the space l6, and, from the latter, through the ventilating conduit, to the exhaust connection II,

the circulation of steam so provided affording ventilation of the blades l8 and preventing over heating thereof.

The valve 46 is preferably arranged for automatic operation, that is, as long as high-pressure steam is supplied to the high-pressure section, the valve is closed and it opens only when such supply is interrupted. As shown, the valve closes by movement in an upstream direction toward the space 16 and it opens in a downstream direction toward the exhaust connection II, the

valve having opposed pressure areas 41 and 48 facing, respectively, in upstream and downstream directions. A movable operating member 49 is connected to the valve and it has opposed pressure areas 50 and 5| forming portions, respectively, of the boundaries of the pressure chambers 52 and 53, the pressure chamber 52 being connected by the conduits 54 and 45 to the space l6 and the chamber 53 being connected by a conduit 55 to the space H. As long as high-pressure steam is supplied to the turbine, the pressure in the space 52 will be higher than that in space 53 to the extent of the pressure drop across the high-pressure blading I8 and the abutment 49 will be operated to close the valve 46. However, just as soon as the supply of high-pressure steam is interrupted, then the pressures at opposite sides of the abutment 49 come into equilibrium; and, as the pressure of low-pressure steam is substantially higher than that of the exhaust, the differential effect thereof acting on the areas 41 and 48 causes the valve 46 to open the by-pass conduit 45 to provide for backflow of steam from the section [1, through the highpressure blading I8 to the exhaust connection for ventilating such blading. When high-pressure steam is again supplied to the turbine, the pressure of steam above the abutment 49 increases and the valve 46 closes.

The valve 46 is of such size as to provide whatever throttling efiect may be required to secure the requisite flow of steam for ventilating purposes considering the diiference in pressure of the low-pressure steam supply and that of the exhaust.

While a governor and a pressure regulator are shown in operative relation to the admission valve 20 and the diaphragm valve 2|, it is to be understood that these control devices are referred to only for the purpose of indicating that under certain conditions the turbine is operated only by the admission of low-pressure steam to the low-pressure section, the admission of high-pressure steam to the high-pressure section being interrupted. Therefore, it is to be understood that the means herein described for ventilating the blading of the high-pressure section when the supply of high-pressure steam thereto is interrupted may be used with a turbine of this type irrespective of the manner in which the admission valve 20 and the diaphragm valve 2| are controlled or operated.

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 specifically set forth in the appended claim.

What I claim is:

In an elastic fluid turbine, a high-pressure section, a low-pressure section, a diaphragm separating the sections, an exhaust connection, said turbine having a first space at the high-pressure side of the blading of the high-pressure section and a second space between such blading and the diaphragm, means including an admission valve for supplying high-pressure elastic fluid to the high-pressure section, a valve for controlling the flow of steam from said second space to the low-pressure section, means for supplying low-pressure elastic fluid to said second space, means for controlling said valves, and means for ventilating the blading of the high-pressure section when the supply of high-pressure elastic fluid thereto is interrupted by closure of the admission valve; said last-named means comprising a conduit aifording communication of said first space with the exhaust connection, a valve in the conduit and arranged to close and to open by movements in directions, respectively, which are upstream toward said first space and downstream toward said exhaust connection, said valve having opposed pressure areas facing in upstream and downstream directions, a movable abutment connected to said valve, and means providing first and second pressure chambers separated by the abutment and connected, respectively, to said first and second spaces.

SEYMOUR Ht HEMENWAY.

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