US2000721A

US2000721A - Centrifugal compressor

Info

Publication number: US2000721A
Application number: US639571A
Authority: US
Inventors: Reginald G Standerwick
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1932-10-26
Filing date: 1932-10-26
Publication date: 1935-05-07
Anticipated expiration: 1952-05-07

Description

, May 7, 1935;v

R. s. STANDERWICK OENTRIFUGAL cowa ssson Filed Oct. 26, 1932 Inventof Reginald G. StandeT-wick,

m l"| ls Attorn e y.

' Patented May 7, 1935 UNITED STATES PATENT OFFICE 2,000,721 cnn'ramccar. comrnnssoa poration of New York Application October 26, 1932 Serial No. 639,571

6 Claims.

In connection with centrifugal compressors, it is known toprovide a blow oil valve or waste valve on the discharge side of the compressor which is opened at light load to waste air or other gas, being'pumped to atmosphere or back to the intake side .of the compressor in order to prevent the occurrence of pulsations or pumping. The load at which pulsation or pumping occurs depends on the volume and the pressure, which in turn bear a, certain relation tothe speed of the machine. For every volume, there is a critical pressure above which pulsations are likely to occur, and vice versa, for every pressure, there is a critical volume below which pulsations are likely to occur. The air or other gas which is discharged through the blow off valve represents a waste in power so that it is desirable to open the blow off valve only when necessary and only to the amount required under particular operating conditions to waste an amount of gas suflicient to prevent pulsation or pumping.

The object of my invention is to provide an improved regulating means for a blow off valve, and for a consideration of what I believe to be novel and my invention, attention is directed to the following specification and the claims appended thereto.

My invention may be utilized in connection with a centrifugal compressor provided with a constant volume governing mechanism and it flnds special utility in connection with a machine so equipped. Howeve'r," it is not limited to such use necessarily.

Inthe drawing, the .flgure is a more or less diagrammatic view of a centrifugal compressor having a blow oif valve provided with regulating means embodying my invention.

Referring to the drawing, l indicates a centrifugal compressor driven by elastic fluid turbine 2. The inlet to the compressor is indicated at 3; the discharge conduit is indicated at l, and the blow oil valve is indicated at 5. In the present instance, the blow oil valve is shown as being locatedin a conduit 6, which leads from the discharge conduit 4 to inlet conduit 3'so that the fluid, which may be air or gas, discharged past the blow oflf valve is returned to the inlet conduit. This arrangement is preferable in the case where the compressor is provided with a constant volume governing mechanism. In the present instance, a constant volume governing mechanism is not shown in the drawing as it forms no part of the present invention. It is to be under-. stood, however, that a constant volumegoverning mechanism may be utilized in connection with the turbine driven compressor if found desirable. For example, a regulating mechanism such as that shown in my Patent 1,729,692, dated October 1, 1929 may be utilized.

Valve 5 is of the butterfly type. It comprises 5 movable valve member I having an operating arm 8 connected to its spindle;- Arm 8 is connected by a rod 9 to the piston of a fluid actuated motor [0, the pilot valve of which is indicated at H. Stem l2 of pilot valve II is pivotally'connected to 10 a lever l3 pivoted at H. Pivotally connected to one end of lever I3 is a rod 15 which at its lower end is connected to an inverted bell l6 located in.a casing [1, the bell being sealed in a liquid chamber l8 in casing I1. I 9 is aweight connected 15 to bell l6. On rod I 5 is an adjustable nut 20 between which and the top of easing I1 is located a spring 2| 'which acts in a direction to move bell I6 upward. Theunder side of hell Hi is connected by a conduit 22 to the trailingside of a 20 pressure difference creating device 23 located in conduit 3. The outer side of bell I6 is connected to atmosphere, for example, by clearance between rod l5 and the cam in casing I! through which it passes. 24 indicates a stop which limits down- 25 ward movement of bell l6, upward movement of the bell being limited by the top of easing l1.- Pressure difierence creating device 23, which is shown in the present instance as a-flow nozzle, creates a pressure diiference which bears a 30 definite relation to the rate of flow of air through conduit 3 and hell it is subjected to this pressure difference so that it assumes a position in accordance with the rate of flow through conduit 3. In this connection, it will'be noted that the leading 35 pressure, that is the pressure in conduit 3 in ad Vance of the device 23 is atmospheric pressure and remains substantially constant so that a leading pressure pipe connection from the leading side of device 23 to casing I1 is not required. 0

Mounted adjacent to the left hand end of lever I3 is a pressure responsive device 25, which is subjected to the pressure in discharge conduit 4. It comprises a casing 26 in which is located a corrugated bellows 21 the edges of which are 45 held between the casing and its cover 28. Corrugated bellows 21 acts on lever I3 through the intermediary of a pivot pin 29 which engages an adjustable socket 29 at the end of the lever. The interior of casing 26 is connected to conduit 50 l by a pipe 30. The connection between pipe 30 and the interior of casing 26 is through an oriflce 3| in a partition plate in casing 26. The area of on'flce 3| is adjusted by means of a needle valve 32. By adjusting the needle valve, the 55 sensitiveness of the corrugated bellows can be varied. At 33 is an adjustable stop for limiting upward movement of corrugated bellows 21.

Mounted adjacent to lever I3 is a second pressure responsive device 34 which is subjected to a pressure difference which bears a definite relation to the rate of flow through by-pass conduit 6. In other words, it is responsive to the rate at which air is discharged past blow-off valve I. It comprises a casing 35 in which is located corrugated bellows 36 which acts on lever 13 through the intermediary of a pivot pin 31 which engages an adjustable socket 3'I on the lever. The interior of casing 35 is connected through an orifice 38, the area of which may be adjusted by means of a needle valve 39, and a pipe 40 to by-pass conduit 6 on the leading side of a pressure difference creating device 4| located in conduit 6. In thepresent instance, pressure difference creating device 4| is shown as being in the form of an orifice. The inside of corrugated bellows 36 is subject to atmospheric pressure which corresponds substantially to the pressure on the trailing side of pressure difference creating device 4|.

It will be noted that pressure responsive device 25 and flow responsive device 34 are located on opposite sides of pivot I4 so that they act in opposition to each other. I

Valve rod 9 is provided with an extension 42 which is connected to one end of a floating lever 43, the other end of which is connected to lever I3 by means of a link 44. Connected to floating lever 43 is a stem 45 of a dash pot. The dash pot comprises a cylinder 46 in which is located a piston 41, which is connected to stem 45. Piston 41 is provided with a plurality of openings closed by a plate 48 which is held against the piston by means of a spring 49 located between the plate and a head 50 on an extension of stem 45. With this arrangement, when piston 41 moves down in cylinder 46 or when it moves up slowly in cylinder 46, plate 48 remains in the position shown in the drawing, thereby keeping the ports through piston 41 closed. Liquid 5I in the dash pot then functions to place a drag on the movement, the extent of the drag being determined by the leakage between the edge of the piston and the cylinder. Upon a quick upward movement of piston 41, disk 48 will be forced away from the piston, thereby uncovering the ports of the piston and permitting the upward movement to take place without appreciable resistance due to the dash pot.

The operation is as follows. Assume that the compressor is operating and delivering gas in volume and pressure such that pulsations or pumping are not likely to occur. Under these conditions, the drop in-pressure through pressure difference creating device 23 is of a value such that bell I6 is held in its downward position as shown in the drawing against the action of spring 2| which tends to move it upward. Pressure device 25 acts on lever I3 in a direction opposite to that of bell l6. In substance, it modifies the action of bell I6 in accordance with the pressure on the delivery side of the compressor. At this time, valve I is closed so that there is no flow through blow-ofi conduit 6. Hence, corrugated bellows 36 is in neutral position against its stop and has no effect on lever l3.

If new the value of either the flow of the compressor or the pressure on the discharge side of the compressor or both, vary so that pulsations are likely to occur, then lever I3 will be moved in a counterclockwise direction on its pivot I4,

thus raising pilot valve II to admit actuating fluid beneath the piston in cylinder I0 and permit it to escape from above the piston whereupon the piston is raised and valve I is opened to a greater or less extent. Flow of gas will occur now from conduit 4 past valve I and through conduit 6 to conduit 3 and there will be created by device M a pressure difference which bears a definite relation to the rate of flow through conduit 6. This pressure difference is applied through pipe 40 to bellows 36, creating a pressure downward on lever I3, thereby moving the right hand end of lever I3 downward and restoring the pilot valve II to normal position where it covers its ports, as is well understood in connection with the operation of a fluid actuated motor of this type. Thus it will be seen that the position of valve I is dependent not only on the fiow through conduit 3 and the pressure in conduit 4 but also on the flow past the blow-01f valve, this being in the present instance the flow through conduit 6. The several forces acting on lever I3 are so related and balanced against each other that valve I is opened enough to by-pass or waste just sufficient gas to prevent the occurrence of pusation.

When conditions of fiow through conduit 3 and pressure in conduit 4 become such that pulsations are no longer likely to occur, lever I3 will be moved to effect closing of valve'I.

The dash pot serves to dampen or regulate the movement of both lever I3 and bell I6 and the valve I, the dash pot permitting of a quick upward movement of bell I6 and a quick opening movement of valve I due to the arrangement of spring pressure plate 48, as already explained.

By adjusting sockets 29 and 31 along lever I3, the forces acting on the lever may be adjusted relatively to each other to give the characteristics desired for the control and to meet the conditions imposed by any particular compressor installation. In making adjustments it will be understood that the pressure responsive devices 25 and 34 will be moved to correct positions relatively to the sockets.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. The combination with a centrifugal compressor having a pulsation preventing valve and means for'opening and closing it in accordance with the resultant of the rate of flow through the compressor and the discharge pressure from the compressor, of means for further controlling the 1 opening and closing of the valve in accordancewith the rate of flow past it.

2. The combination with a centrifugal compressor having a pulsation preventing valve and means for opening and closing it in accordance with the rate of flow through the compressor, of means for further controlling the opening and closing of the valve in accordance with the rate of fiow past it.

3. The combination with a centrifugal compressor having a pulsation preventing valve, of a fluid actuated motor connected to the valve, a pilot valve for the motor, a pivoted lever to which the pilot valve is connected, and means responsive to the flow to the compressor, the pressure on the discharge side of the compressor and the flow past the pulsation preventing valve for pcsitioning said lever in accordance with a resultant value of said flows and pressure.

4. The combination with a centrifugal compressor having a pulsation preventing valve, of a fluid actuated motor connected to the valve, a pilot valve for the motor, a pivoted lever to which the pilot valve is connected, meansresponsive to the flow to the compressor, the pressure on the discharge side of the compressor and vthe flow past the pulsation preventing valve for positioning. said lever in accordance with a resultant value or said flows and pressure, and a dash pot for dampening movement of the lever and the pulsation preventing valve,

5. A centrifugal compressor having a blow-oi! valve, means responsive to-a flow through the compressor, to control the opening and closing or said valve, and means to adjust the opening and closing of said valve comprising means responsive to the flow past the blow-oi! valve, means responsive to the discharge pressure, and means connecting said two last named means to the valve whereby said valve is controlled in accordance with the resultant oi. the flow through the compressor, the flow past the blow-oil. valve, and the discharge pressure.

6. A centrifugal compressor having a blow-ofl valve; means responsive to the flow through the inlet of the compressor to control the opening and closing of said valve and meansresponslve to the. now past the blow-oi! valve to adjust the opening and closing oi! said valve, whereby said valve is controlled in accordance with the resultantot the flow through the inlet of the compressor and the flow past the blow-o1! valve.

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