US1915983A - Cross compound turbine - Google Patents

Description

June 27, 1933. I DORAN 1,915,983

cnoss COMPOUND TURBINE Filed June 15. 1931 Driven frm Ziarfiz'ne Z.

Inventor John H. Dorom,

b His Attorney.

' 7 turbine.

Patented June 27,

UNHTED STATES PATENT OFFICE JOHN H. DOB-AN F SCHEIEECTA'DY, NEW YORK, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK (moss comronnn TURBINE Application filed June 15,

The present invention refers to cross compound turbines in which the elastic fluid produced in a generator is supplied to the inlet of a high pressure turbine part and the ex haust of said high pressure turbine part is supplied to a low pressure turbine part.

In connection with the operation of such turbines, the condition obtains sometimes that the turbines are operated at no load, and under these circumstances it is required that cooling medium such as elastic fluid be supplied to the turbines to keep down the temperature of the rotor. Otherwise, due to friction the rotor would become over-heated. An instance wherein such turbines are operated at no load is met with when a turbogenerator is floated on the line, the generator acting as a synchronous condenser.

The object of my invention is to provide an improved construction and arrangement for supplying cooling medium to a cross compound turbine for protecting it, and par ticularly for protecting the low pressure part, against over-heating when the turbine is running idle. I

This is accomplished according to my invention by the provision of certain protective means actuated in response to conditions in the supply conduit to the low pressure part and adapted to cause live-steam to be supplied directly to said low pressure part if,

for instance, the steam pressure in said supply conduit decreases beyond a minimum value.

For a consideration of what I believe to be novel and my invention, attention is directed to the following description and the claims appended thereto.

In the drawing, the figure shows a cross compound turbine installation, partly diagrammatic and partly in cross section, embodying my invention.

Referring to the drawing, 1 and 2 represent the high and low pressure parts of'a cross compound turbine, in'the present instance shown as being arranged on separate shafts and adapted to drive electric generators 3 and 4 respectively. 5 is an elastic fluid generator which supplies fluid through a conduit 6 to the high pressure part 1 of the 7 represents a reheater which is connected to the exhaust conduit of the high pressure part and which supplies the reheated elastic fluid through a conduit 8 to the low pressure part 2 of the turbine. 9 is said high pressure part.

1931. Serial No. 544,405.

a manually operated main valve provided in conduit 6 for shutting off the steam supply to the high pressure part. 10 is another valve means provided in said conduit and actuated automatically, in the present in stance shown by a speed responsive governor 11 provided 011 the right end of a lever 12 and being adapted to control a fluid actua-ted motor 13 comprising a pilot valve 14 having its valve disks connected by a stem 15 to said lever 12, and a cylinder 16. Provided in cylinder 16 is a piston 17 having its stem 18 connected to the left end oflever 12 and being adapted to control valve means 10. 'The operation of this fluid actuated motor which is known in the art is briefly as follows: Increase of speedof the turbine causes the weigl1ts19 of the regulator to fly outwardly and thus causes an upward movement of the right end of lever 12 and a corresponding upward movement of the pilot valve to the effect that oil or like liquid is supplied to the upper part of cylinder 16 and drained off from the lower part of this cylinder. This causes downward movement of.piston 17 and accordingly a closing actuation of valve means 10. The downward movement of piston 17 also effects a corresponding movement of the pilot valve whereby the latter is restored to its original position.

Provided in conduit 8 is another valve means 20 for regulating the supply of fluid to the low pressure part. The control of this valve means is in the present instance shown as being accomplished in a. way similar to that described above, that is, by a speed re-- sponsive governor 21 which is adapted to regulate a fluid actuated motor 22 comprising a pilot valve 23 and a cylinder 24.

The arrangement so far described may be considered as typical for any cross compound turbine installation in which the two parts I are arranged on different shafts.

In order to prevent overheatingof the turbine bucket wheels if the supplied steam reaches a minimum value, that is, if valve means 10 is near its closed position I provide a by-pass 25 around the fluid admission controlling valve 10. This by-pass allows a certainamount of steam to be supplied to the high pressure part irrespective ofthe' position of valve means 10 and thus preventsoverheating of the bucket wheels, at least of steam, however, may be insuflicient to prevent This amount of 110,

overheating of the low pressure part, particularly if the exhaust of the high pressure part is passed through a reheater 7 and has a long path until it reaches the low pressure part.

In order to successfully prevent overheat-- ing of the low pressure part I may provide according to my invention a conduit 26 connected to the live elastic fluid line 6 and adapted to admit under certain conditions live elastic fluid directly from the elastic fluid generator to the lowpressure part. 27 represents a valve means which in the present instance I have shown as being actuated by a pressure responsive means 28 connected to the admission conduit 8 of the low pressure part and comprising a casing 29 in which is provided a diaphragm connected to stem 30 of valve 27. The upper part of casing 29 has a pipe 31 connected to supply conduit 8. A spring 32 provided between the diaphragm and the lowerhalf of easing 2-9 biases the valve towards open position.

The operation of my arrangement is as follows: Under normal conditions, valve 27 is closed. By normal conditions I mean conditions under which suflicient elastic fluid is conducted from the high pressure part to the low pressure'part 2 to prevent excessive heating of the low pressure part. If the cross compound turbine is running at low load, particularlyif the generators are operating -as synchronous condensers, that is, when the pressure in conduit 8 decreases be yond a predetermined value, it will cause a correspondingdecreasein the upper part of the pressure responsive device 28' to the eflect that the diaphragm of this device moves upwardly under action of the spring'32 and effects opening of valve means-27. The opening of this valve permits a suificient amount of fluid to be supplied from the elastic fluid generator directly to the low pressure part part is prevented.

(if the turbine whereby over-heating of this It now the load increases again it will cause a corresponding increase in pressure in the upper part of the pressure responsive device 28 to the effect that the latter causes a closing actuation of valve 27.

In accordance with the provisions of the turbine comprising a high pressure part and a low pressurepart, of an elastic fluid generator for supplying elastic fluid to said high pressure part, a valve meansfor regulating the admission of elastic fluid to said high pressure part, a by-pass around said valve means to admit a minimum amount of elastic fluid to said high pressurepart for protect ing said part against over-heating, a conduit for passing the exhaust steam of the high pressure part to said low pressure part, the exhaust of the high pressure part being normally sufficient to prevent excessive heating of the low pressure part, a conduit connecting the inlet of said low pressure part directly to said fluid generator, a normally closed valve means in said last named conduit, and a device responsive to the fluid pressure in the conduit for opening said last named valve means to permit the supply of live elastic fluid to the low pressure'part whereby overheating thereof is prevented.

2, The combination with a cross compound turbine installation comprising a high pres sure turbine part and a low pressure turbine part, of an elastic fluid generator, a conduit connecting said elastic fluid generator with said high pressure part, a valve means in said conduit for regulating the admission of elastic fluid to said high pressure part, a by-pass connected to said conduit around said valve means for admitting a certain amount of fluid to said high pressure part for protecting the high pressure part against overheating at low load and while running idle, a reheater and a conduit provided between the exhaust of said high pressure part and the inlet of said low pressure part, another valve means provided in said conduit for regulating the admission of elastic fluid to said low pressure part, a conduit for supplying live elastic fluid directly to said low pressure part, a valve means in said last named conduit, and a pressure responsive device for actuating said last named valve means in'ternis of fluid pressure supplied through said other valve-means to said low pressure part whereby overheating of the latter is prevented.

3. The combination with across compound turbine installation comprising a high pressure and a low pressure part, of an elastic fluid generator for supplying elastic fluid to said turbine, valve means for controlling the supply of elastic fluid to said high pressure part, a reheater and a conduit for supplying the exhaust elastic fluid of said high pressurepart to said low pressure part, and means for preventing overheating of the low pressure part comprising a conduit for supplying live elastic fluid directly from said 7 elastic fluid generator to said low pressure part, and a pressure responsive device for actuating said last named valve means in' terms of pressure of elastic fluid supplied through said reheater and said conduit to said low pressure part.

In witness thereof, I have hereunto set my hand.

1 JOHN H'. DORAN.

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