US2854211A

US2854211A - Adjustable vane arrangement for fluid flow machinery

Info

Publication number: US2854211A
Application number: US548911A
Authority: US
Inventors: Bendersky Joseph
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1955-11-25
Filing date: 1955-11-25
Publication date: 1958-09-30
Anticipated expiration: 1975-09-30

Description

p 1958 J. BENDERSKY 2,854,211

ADJUSTABLE VANE ARRANGEMENT FOR FLUID FLOW MACHINERY Filed NOV. 25, 1955 r E I? r "1 IN VEN TOR.

ADJUSTABLE VANE ARRANGEMENT FGR FLUID FLGW MACHINERY Joseph Bendersky, Lynn, Mass, assignor to General Eiectric Company, a corporation of New York Appiication November 25, 1955, Serial No. 548311 2 Ciaims. (Cl. 253-78) This invention relates to fluid flow machines and more particularly to adjustable vanes for varying the flow of fluid through the machine.

The power output of a turbomachine is a function of two principal variables. These are the flow of motive fluid through the machine in weight per unit time and the actual temperature change in the fluid in traveling from the turbomachine inlet to the turbomachine exit. In order to vary the power, one has to control either the fluid flow or the temperature change. Usually the type of power control in actual use affects both the fluid flow and the temperature change. In turbines, it is most economical for the control to maximize the temperature drop and minimize the amount of fluid flow for any power output. Accordingly, a control which approaches this is most desirable.

The simplest and probably the most common way of controlling the power output of a turbine is to have a turbine diaphragm with a fixed nozzle area and incorporate a throttling valve in the motive fluid supply line at a point upstream from the turbine nozzle diaphragm. However,-since the throttling process decreases the temperature drop across the turbine when reducing from full power by affecting the inlet pressure to the nozzle diaphragm, the fluid flow does not decrease linearly with output power.

Accordingly, to provide an arrangement in which the amount of fluid flow varies directly with the power it has been the practice to eliminate the throttling valve and provide a variable area type of nozzle diaphragm in which the nozzle area is varied to regulate the flow of motive fluid therethrough. Thus with a variable area type nozzle diaphragm, the amount of fluid flow will almost vary directly with the power output.

One of the most common and satisfactory methods of varying the area of the nozzle diaphragm is to provide blades or partitions which are pivotally mounted so that the blades may be rotated to vary their angle and consequently the flow area of the diaphragm. With this type of arrangement, it has heretofore been the practice to rotate each nozzle partition in the diaphragm simultaneously through equal arcs.

In some applications the power output of a turbomachine may be required to vary by a factor of to one. In addition, the density of the fluid flow may also vary by a factor of 10 to one. Thus the range of blade or partition angular position may vary from a half degree open to 35 open. It is known that small angular positions of the blades or partitions are detrimental to the efi'iciency of the turbomachine, and thus should be avoided. Thus it is desirable to use an area controlling device which does not change the angular position of the blades or at least minimize the angular change needed.

A device which controls the area without changing the blade angle is a partial arc control which blocks off, by means such as a moving plate, certain nozzle partitions in a fixed partition diaphragm to change the total flow area of the diaphragm. Several of the disadvannited States Patent tages of this type of arrangement are that the mechanical schemes for accomplishing this are extremely awkward and heavy and increased windage losses attend blocking off a large percentage of the nozzle to obtain low flow and power. Accordingly, it is an object of the present invention to provide an improved adjustable vane arrangement which combines the advantages of partial arc and variable angle control.

Another object of the invention is to provide an improved controllable diaphragm for a turbomachine which is mechanically light in weight and simple and which provides improved unit efliciency.

Briefly these and other objects are accomplished by providing adjustable vanes including a plurality of rotatable vanes which are divided into separate groups, the vanes in each group being rotatable independently of those in the others.

The invention will be better understood from the following description taken in connection with the accompanying drawing in which Figure 1 is a perspective view of a nozzle diaphragm for a turbomachine constructed in accordance with the present invention, Figure 2 is an enlarged view of a detail of construction of the apparatus shown in Figure 1.

In the drawing, the nozzle diaphragm comprises a plurality of nozzle vanes 10 which are rotatably disposed between inner and outer annular casing members 11 and 12. Each of the nozzle vanes 10 has a'portion with an airfoil shaped cross-section to afford between them admission throats of varying cross-sections. Each vane 10 is mounted for rotation in a bearing 13 carried by the outer casing member 12 and a bearing 14 carried by the inner casing member 11. Connected to the inner end of each nozzle vane 10 is a control arm 15 which controls the rotational position of the vane. The vanes 10 are divided into a plurality of individually controlled groups, two such groups being shown in the drawing. The vanes in the upper half of the diaphragm form one group each having a control arm 15 which is longer than those in the group formed by the vanes in the bottom half of the diaphragm. The extremities of the control arms 15 belonging to the nozzle vanes in the upper half of the diaphragm rest in slots provided in the outer periphery of a control disk 17. Referring to Figure 2, it will be noted that the slots 28 are shaped so that the control shaft 15 is free to pivot as indicated by the dotted lines upon rotation of the control disk 17. The control arms 15 of the lower group of vanes rest in slots in a separate control disk 16. The outer portion of the upper half of the control disk 16 is cut away to prevent interference with the control arms 15 of the upper group of nozzle vanes which extend to the control disk 17.

The control disks 16 and 17 are separately actuated by concentric control shafts 18 and 19 respectively. The shaft 19 is secured to the disk 17, and the shaft 18 is secured to the disk 16. A gear 20 is rigidly secured to the other end of the inner control shaft 18 and a second gear 21 is rigidly secured to the end of the outer control shaft 19. An input control shaft 22 is mounted adjacent the gears 20 and 21 and carries two spur gears 23 and 24 adapted to mesh with the gears 20 and 21 respectively. The gear 23 is provided with teeth only on that portion of its periphery suspended by the angle 0, and the gear 24 is provided with gear teeth only on that portion of its periphery subtended by the angle It will be noted that in the drawing the nozzle vanes are shown in their closed position. Rotation of the control disks 16 and 17 in the direction indicated by the arrows causes the nozzle vanes to rotate towards the open position. Rotation of the gear 23 through the angle 9 causes the vanes in the lower half of the diaphragm to rotate from their fully closed to their fully open position.

A spring 25 is fastened at one end to the a to astationary support (not shown) are positioned to prevent rotationvof the shaft 18 beyond a position corresponding to the full open position of the nozzle vanes 10 associated therewith when the gears 20 and 23 become disengaged.

The operation of the apparatus just described is as follows. Minimum nozzle flow. area is obtained when the parts are in the position as shown in the drawing with all of the nozzle vanes 10 in the closed position. As increasing nozzle flow area is required, the input control shaft 22 is rotated in the direction indicated by the arrow in the drawing. It will be noted that as'the input shaft 22 rotates through an angle indicated as 6 in the drawing, gear 23 drives the gear 20 and, through the shaft 18, the control disk 16 thus opening the nozzle vanes in the lower half of the diaphragm. When the nozzles reach their fully open position, the gears of 23 and 20 become'unmeshed as the toothlesspart of gear 23 is brought oppositethe gear 20. The spring 26 biases the disk 16 so that :the mechanical stop 27 is held against the stop 28 and the associated nozzle vanes are held in their open position. As rotation of the control shaft 22 continues through an angle qfi, the teeth on the gear 24 engage-those on the gear 21 thus rotating the associatednozzle vanes 10 in the upper half of the nozzle diaphragm to their open position. On closing, thereverse operation takes place.

Thm it will be seen that an arrangement is provided each group of vanes.

While a particular embodiment of the invention has been illustrated and described, it will be obvious to those I skilled in the art that various changes and modifications may be made without departing from the invention and it is intended to cover in the appended claims all such 4 i changes and modifications that come within the true spirit and scope of the invention.

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

1. In a fluid flow machine comprising a casing, a nozzle diaphragm comprising a plurality of uniformly and circumferentially spaced nozzle vanes, a pivot carried by said casing for each of said nozzle vanes, an arm connected to each of said vanes, a first rotatable member operably connected to a first group of said armsfor rotation of a first group of said vanes connected thereto about said pivots, a second rotatable member operably connected to a second group of said arms for rotation of a second group of said vanes connected thereto about said pivots, and a control member operably connected to said rotatable members for sequential operation of saidmembers to sequentially rotate said first and said second groups of vanes from a minimum to a maximum flow area position.

2. In a fluid flow machine comprising a casing, a nozzle diaphragm comprisinga plurality of uniformly and circurnferentially spaced nozzle vanes, a pivot carried by said casing for each of said nozzle vanes, an arm connected to each of said vanes, a first rotatable member operably connected to a first group of said arms for rotafirst and said second rotatable members for sequential operation of said first rotatable member and said first group of vanes from a minimum to a maximum flow area position, and of said second rotatable member'and said second group of vanes from a minimum to a maximum flow area position.

References Cited in the file of this patent UNITED STATES PATENTS 1,823,311 Simpson .Sept. 15, 1931 2,219,994 Jung Oct. 29, 1940 2,613,029 Wilde Oct. 7, 1952 FOREIGN PATENTS 609,682 Great Britain Oct. 5, 1948 737,472 Great Britain Sept. 28, 1955