US3861823A

US3861823A - Compressor with retractable guide vanes

Info

Publication number: US3861823A
Application number: US323936A
Authority: US
Inventors: George K Serovy
Original assignee: Caterpillar Tractor Co
Current assignee: Caterpillar Inc
Priority date: 1973-01-15
Filing date: 1973-01-15
Publication date: 1975-01-21
Anticipated expiration: 1992-01-21

Abstract

In a compressor having a bladed rotor, a system is included for introducing guide vanes into the fluid path leading to such blades, such guide vanes being completely removable from said path when desired.

Description

Umted States Patent 1191 1111 3,861,823 Serovy Jan. 21,1975

1 1 COMPRESSOR WITH RETRACTABLE 3,465,950 9/1969 Freid et a1. 415/121 0 GUIDE VANES 3,733,814 5/1973 Hull, Jr. et a 415/121 0 [75] Inventor: George K. Serovy, Ames, Iowa FOREIGN P N R APPLICATIONS 951,944 I 4/1949 France 415/147 [73] Ass'gnee' Cate'pma' Tract" 9 1,142,112 3/1957 France 415/147 [22] Filed; Jan, 15, 1973 588,895 12/1959 Canada 415/147 702,266 1/1954 Great Britain 415/147 [21] Appl. No.: 323,936

Primary Examiner-Henry F. Raduazo [52] US. Cl. 415/147, 415/151 t y, g or FirmPhillips, M [51] Int. Cl. F04d 27/00 i ge pi & St aba [58] Field of Search 415/121 G, 147, 151, 150

[57] ABSTRACT [56] References Cited In a compressor having a bladed rotor a system is in- UNITED STATES PATENTS cluded for introducing guide vanes into the fluid path 2,838,227 6/1958 Thomas et al. 415/147 l di t uch blades, such guide vanes being com- 2,858,974 11/1958 Bullock et a1 415/147 pletely removable from Said path when dash-L 2,870,956 l/1959 Dhonau et a1. 415/147 3,237,563 3/1966 Hartland 415/151 5 Claims, 8 Drawing Figures COMPRESSOR WITH RETRACTABLE GUIDE VANES BACKGROUND OF THE INVENTION This invention relates to compressors, and more particularly, to a fluid compressor which incorporates movable inlet guide vanes which direct a fluid to the compressing means.

Rotating fluid compressors used with gas turbine engines are normally designed to achieve peak efficiency under pre-determined operating conditions which can be referred to as optimum design conditions. For instance, the density of the fluid is dependent upon its temperature and pressure, and changes in either of these parameters will affect the fluid density and consequently the ability of a compressor to efficiently compress the fluid. In addition, changes in output power by the engine may require a corresponding change in compressor speed. A reduction in compressor speed will decrease the velocity of the inlet fluid, thereby producing a higher relative inlet flow angle with respect to the compressor blades. Such a condition contributes to aerodynamic losses which could produce a phenomenon commonly referred to as blade stall since it corresponds to the well-known performance of an airplane wing disposed at too high an angle of attack.

The use of inlet guide vanes in a turbine compressor to reduce the inlet flow angle for operating at a level other than its optimum design condition is well known to the art. U.S. Pat. No. 2,733,853 to W. E. Trumpler illustrates the use of movable inlet guide vanes. Flexible vanes capable of varying the blade camber angle are described in US. Pat. No. 3,397,836 to W. C. Badger et al. These approaches, while improving the inlet flow angle at part load or at some other condition less than optimum design condition, are generally not required for normal operation under conditions at which the compressor is designed to operate at maximum efficiency. Consequently, even though the vanes are usually paired or otherwise adjusted for zero turning of the inlet fluid at optimum design conditions, the presence of the vanes in the flow stream produces undesirable blockage of the fluid inlet when they are not required.

SUMMARY OF THE INVENTION It is an object of this invention to provide, in a fluid compressor, a guide vane system which can be called on to function only when required.

It is a further object of this invention to provide a guide vane system which properly improves the inlet flow angle of the fluid under conditions other than the optimum design condition.

It is a still further object of this invention to provide a guide vane system which, while fulfilling the above objects, includes automatic sensing and control means to properly vary the inlet flow angle of such fluid.

It is a still further object of this invention to provide a guide vane system which, while fulfilling the above objects, is simple and efficient in design.

Broadly stated, the invention is in a compressor having a housing, a bladed rotor rotatably associated with the housing, and means defining an annular fluid inlet passage leading into the blades of said rotor and through which said fluid passes to said rotor blades. Such invention comprises means selectively positionable in said annular fluid inlet passage to redirect a portion of the fluid passing to said rotor blades through said annular fluid inlet passage and completely removable from said annular fluid inlet passage.

BRIEF DESCRIPTION OF THE DRAWINGS These and other objects of the invention will become apparent from a study of the following specifications and drawings, in which:

FIG. I is a sectional elevation of a fluid compressor incorporating the invention;

FIG. 2 is a sectional view taken along the line ll-ll of FIG. 1, and further showing control means of the system;

FIG. 3 is an enlarged view of an area of the fluid compressor; and,

FIGS. 48 are vector diagrams representing the fluid flow at the tip and hub portions of the rotor blades of the compressor, under various operating conditions.

DESCRIPTION OF THE PREFERRED EMBODIMENT With particular reference to FIGS. 1 and 2, a compressor for a gas turbine engine incorporating the principles of the present invention is generally indicated by the reference numeral 10. Such compressor 10 includes a housing 12 made up of a stationary central housing 14 and a stationary outer housing assembly 16. A bladed rotor 18 is rotatably mounted to the central housing 14 and is rotatable about its axis. The blades 20 of the rotor 18 each define a tip portion 22 and a hub portion 24. The housing assembly 16 comprises a circular shroud portion 26 and a partially contoured annular ring 28 joined to the shroud portion 26 by a plurality of bolts 30. The central housing 14 and housing assembly I6 define an annular fluid inlet passage 32 leading into the blades 20 of the rotor 18 and through which fluid passes to said rotor blades 20.

A plurality of guide vanes 34 are associated with the housing 12 as shown. Each guide vane 34 includes a rack member 36, with the guide vane 34 fixed thereto. Each rack member 36 is reciprocally mounted in a slot 38 in the outer housing assembly 16, so that each guide vane 34 is movable into the annular fluid inlet passage.

32 toward the axis of rotation of the rotor 18, and outwardly therefrom to be completely removed from the annular fluid inlet passage 32. Further included are a plurality of pinion gears 40, each pinion gear 40 being rotatably mounted to the other housing assembly 16, between shroud portion 26 and annular ring 28, with the teeth thereof in an engagement with teeth of a rack member 36.

A ring gear 42 is rotatably mounted to housing assembly 16 on a bushing 44. Bushing 44 is supported on the annular ring 28 to provide a piloting and bearing surface for the ring gear 42. Each pinion gear 40 has the teeth thereof in engagement with the teeth of the ring gear 42. It will be seen that rotation of the ring gear 42 in one direction relative to the housing 12 rotates the pinion gears 40 to move the rack members 36 and guide vanes 34 attached thereto inwardly of the annular fluid passage 32, and rotation of the ring gear 42 relative to the housing 12 in the other direction rotates the pinion gears 40 to move the rack members 36 and guide vanes 34 attached thereto outwardly of the annular fluid inlet passage 32.

For the purpose of illustrating the operation of the present invention, an imaginary vertical plane A-A positioned immediately upstream of the compressor rotor 18, as indicated in FIG. 3 by broken lines, is used as a reference plane with regard to the ensuing discussion of inlet flow velocity distribution. Although the vectors in FIGS. 4-8 are not drawn to a particular scale, conventional vector notations familiar to those skilled in the art are used.

FlGS. 4 and 5 illustrate typical vector diagrams representing the flow at the rotor blade tip and

hub portions

22,24, respectively, for operation at the optimum design conditions. The absolute velocity vector is perpendicular to the rotor 18 velocity vector U. The velocity of the inlet flow relative to the rotor 18 is represented by vector V, and the included angle between the vectors V and V, designated Beta, represents the relative inlet flow angle of the fluid. It should be noted that the absolute velocity vector V is essentially equal at the tip 22 and hub 24 portions. The rotor 18 velocity U, however, is a function of the rotor 18 radius, and is therefore greater at the tip 22 than at the hub 24. Thus, the relative inlet flow angle Beta of FIG. 4 is likewise greater at the tip 22 than the flow angle Beta of FIG. 5 at the hub 24. This condition is anticipated and the rotor blades 20 are normally designed with the appropriate incidence angle at the tip 22 and hub 24 portions to compensate for differences to the relative inlet flow angle for operation at a predetermined optimum design condition.

Since the rotor velocity U is greater at the tip 22 than at the hub 24 portion, the tip 22 is influenced more than the hub 24 by changes in rotor 18 velocity. For example, FIG. 6 represents a velocity distribution diagram for inlet flow at the tip 22 that is typical of operation at slightly less than the optimum design condition. The absolute velocity vector V has decreased proportionately more than the rotor 18 velocity vector U, and is slightly lower than at the optimum design condition, and therefore the relative inlet flow angle Beta is greater than for the predetermined optimum design condition. The increase in the relative inlet flow angle Beta contributes to losses at the tip 22, thus lowering the compressor 10 efficiency. Insertion of a guide vane 24 partially into the inlet passage 32 deflects or redirects a portion of a fluid passing through the passage 32 to the tip portions 22 of the rotor blades 20, thereby altering the relative inlet flow angle Beta and the relative velocity Vector V as indicated by a solid vector in the diagram.

At operating conditions which deviate more greatly from the optimum design condition, both tip 22 and hub 24 portions will show significant changes in the relative inlet flow angle Beta. This condition is represented by broken vectors in the velocity diagrams of FIGS. 7 and 8. Insertion of the inlet guide vanes across the inlet passage to redirect the inlet flow to both the tip portions and hub portions of the rotor blades, as represented by solid vectors, effectively reduces the relative inlet flow angle Beta to values near that of normal optimum design condition operation.

The principal control elements are shown schematically in FIG. 2. A hydraulic cylinder 50 is anchored at one end 52 to a compressor frame member 54. The hydraulic cylinder 50 includes a piston 56 which is attached to a tab 58 of the ring gear 42 by a control rod 60. A control unit 62, interposed the cylinder 50 and a fluid source 64, receives an input signal such as engine speed or compressor discharge pressure. designated by arrows N and CDP, respectively. In response to the input signal, the control unit modulates the flow of fluid from the supply source to the hydraulic cylinder 50 by way of

conduits

66 and 68, communicating respectively with

internal chambers

70 and 72 located within the cylinder 50.

Compressor performance may be easily measured by sensing one of several operating characteristics such as rotor speed or compressor discharge pressure. As best shown in H0. 2, the control unit 62 uses an electrical signal output from a speed sensor or pressure transducer, not shown, to modulate a valve supplying fluid to the hydraulic cylinder 50. During normal operation at the optimum design condition, when directional control of the inlet flow is not required, the guide vanes 34 are fully retracted into the housing 16. The control unit 62 supplies pressurized fluid to the chamber 70 of the cylinder 50 while simultaneously evacuating fluid from the chamber 72 to force the piston 56 to its extreme right position. This action produces a clock-wise rotation of the ring gear 42, thereby rotating the pinion gear 40 in a clock-wise direction. Clock-wise rotary movement of the pinion gears 40, each operatively engaging a gear rack 36, produces a concurrent radially outward retracting of the guide vanes 34. In this operating mode, the vanes 34 present no obstruction or blockage to the inlet air flow.

During compressor 10 operation at slightly less than the optimum condition, directional control of the inlet flow of the rotor tip 22 is desirable. As shown in the vector diagram of FIG. 6, the relative inlet flow angle Beta can be reduced to a more nearly normal value by insertion of a guide vane 34 into the inlet passage 32. Accordingly, the control unit 62, sensing an operating condition somewhat less than the optimum design condition, simultaneously relieves a measured amount of fluid from the chamber 70 and adds a like amount of fluid to chamber 72. Transposition of fluid from the chamber 70 to chamber 72 forces the piston 56 partially to the left, producing a corresponding counterclockwise rotation of the ring gear 42 and the pinion gears 40. This motion produces a concurrent radially inward movement of the guide vanes 34 partially into the inlet passage 32 as determined by the control unit 62. Consequently, the relative inlet flow angle Beta is reduced to an acceptable value, thereby reducing unwanted losses and increasing compressor performance. Also, since the guide vanes 34 are inserted to influence only the inlet flow at the tip 22 portions, undesirable blockage of the inlet flow at the hub 24 is avoided.

When the compressor 10 is required to operate at other than the optimum design condition, the abovedescribed operation for partial vane assembly extension is continued until the vanes 34 are fully projected into the inlet passage 32. The control unit 62 supplies fluid to the cavity 72 and relieves the fluid contained in cavity 70 to urge the piston 56 leftwardly. This action produces counter-clockwise rotation of the ring gear 42 and pinion gears 40, resulting in concurrent extension of the guide vanes 34 into the inlet passage 32.

What is claimed is:

1. In a compressor having a housing, a bladed rotor rotatably associated with the housing, and means defining an annular fluid inlet passage leading into the blades of said rotor and through which said fluid passes to said rotor blades. the improvement which comprises means selectively positionable in the annular fluid inlet passage to redirect a portion ofthe fluid passing to said rotor blades through said annular fluid inlet passage and removable to a substantial degree from said annular fluid inlet passage, wherein the selectively positionable means are completely removable from said annular fluid inlet passage, and wherein said selectively positionable means comprise a plurality of guide vanes reciprocally associated with .the housing and movable into the annular fluid inlet passage and outwardly therefrom, and means for selectively so moving said guide vanes, wherein said means for selectively moving the guide vanes into the annular fluid inlet passage and outwardly therefrom comprise a plurality of rack members, each rack member having a guide vane fixed thereto and extending inwardly therefrom, a plurality of pinion gears, each pinion gear being rotatably mounted to the housing and having the teeth thereof in engagement with the teeth of a rack member, and a ring gear rotatably mounted to the housing, each pinion gear having the teeth thereof in engagement with the teeth of the ring gear, so that rotation of the ring gear relative to the housing in one direction rotates the pinion gears to move the rack members and guide vanes attached thereto inwardly of the annular fluid inlet passage, and rotation of the ring gear relative to the housing in the other direction rotates the pinion gears to move the rack members and guide vanes attached thereto outwardly of the annular fluid inlet passage.

2. The apparatus of claim 1 and further comprising automatic sensing and control means for rotating said ring gear relative to said housing in response to variations in selected compressor operating characteristics. 3. A compressor comprising: a housing; a bladed rotor rotatably associated with the housing, rotatable about its axis and having blades each defining a tip portion and a hub portion; said housing defining an annular fluid inlet passage leading into the blades of the rotor and through which said fluid passes to said rotor blades; a plurality of guide vanes reciprocally associ- 6 ated with the housing and movable into the annular fluid inlet passage toward the axis of rotation of the rotor, and outwardly therefrom to be completely removed from the annular fluid inlet passage, whereby, upon initial movement of the guide vanes into the annular fluid inlet passage, such guide vanes are positioned to redirect a portion of the fluid passing to the tip portions of the rotor blades through the annular fluid inlet passage; and, means for selectively so moving said guide vanes, and wherein said means for selectively moving the guide vanes into the annular fluid inlet passage and outwardly therefrom comprise a plurality of rack members, each rack member having a guide vane fixed thereto and extending inwardly therefrom toward the axis of rotation of the rotor, a plurality of pinion gears, each pinion gear being rotatably mounted to the housing and having the teeth thereof in engagement with the teeth of a rack member, and a ring gear rotatably mounted to the housing, each pinion gear having the teeth thereof in engagement with the teeth of the ring gear so that rotation of the ring gear relative to the housing in one direction rotates the pinion gears to move the rack members and guide vanes attached thereto inwardly of the annular fluid inlet passage, and rotation of the ring gear relative to the housing in the other direction rotates the pinion gears to move the rack members and guide vanes attached thereto outwardly of the annular fluid inlet passage.

4. The compressor according to claim 3 wherein the guide vanes are movable toward the axis of rotation of the rotor to an extent sufficient to redirect a portion of the fluid passing to the hub portions of the rotor blades through the annular fluid inlet passage.

5. The compressor of claim 4 and further comprising automatic sensing and control means for rotating said ring gear relative to said housing in response to variations in selected compressor operating characteristics.

Claims

1. In a compressor having a housing, a bladed rotor rotatably associated with the housing, and means defining an annular fluid inlet passage leading into the blades of said rotor and through which said fluid passes to said rotor blades, the improvement which comprises means selectively positionable in the annular fluid inlet passage to redirect a portion of the fluid passing to said rotor blades through said annular fluid inlet passage and removable to a substantial degree from said annular fluid inlet passage, wherein the selectively positionable means are completely removable from said annular fluid inlet passage, and wherein said selectively positionable means comprise a plurality of guide vanes reciprocally associated with the housing and movable into the annular fluid inlet passage and outwardly therefrom, and means for selectively so moving said guide vanes, wherein said means for selectively moving the guide vanes into the annular fluid inlet passage and outwardly therefrom comprise a plurality of rack members, each rack member having a guide vane fixed thereto and extending inwardly therefrom, a plurality of pinion gears, each pinion gear being rotatably mounted to the housing and having the teeth thereof in engagement with the teeth of a rack member, and a ring gear rotatably mounted to the housing, each pinion gear having the teeth thereof in engagement with the teeth of the ring gear, so that rotation of the ring gear relative to the housing in one direction rotates the pinion gears to move the rack members and guide vanes attached thereto inwardly of the annular fluid inlet passage, and rotation of the ring gear relative to the housing in the other direction rotates the pinion gears to move the rack members and guide vanes attached thereto outwardly of the annular fluid inlet passage.

2. The apparatus of claim 1 and further comprising automatic sensing and control means for rotating said ring gear relative to said housing in response to variations in selected compressor operating characteristics.

3. A compressor comprising: a housing; a bladed rotor rotatably associated with the housing, rotatable about its axis and having blades each defining a tip portion and a hub portion; said housing defining an annular fluid inlet passage leading into the blades of the rotor and through which said fluid passes to said rotor blades; a plurality of guide vanes reciprocally associated with the housing and movable into the annular fluid inlet passage toward the axis of rotation of the rotor, and outwardly therefrom to be completely removed from the annular fluid inlet passage, whereby, upon initial movement of the guide vanes into the annular fluid inlet passage, such guide vanes are positioned to redirect a portion of the fluid passing to the tip portions of the rotor blades through the annular fluid inlet passage; and, means for selectively so moving said guide vanes, and wherein said means for selectively moving the guide vanes into the annular fluid inlet passage and outwardly therefrom comprise a plurality of rack members, each rack member having a guide vane fixed thereto and extending inwardly therefrom toward the axis of rotation of the rotor, a plurality of pinion gears, each pinion gear being rotatably mounted to the housing and having the teeth thereof in engagement with the teeth of a rack member, and a ring gear rotatably mounted to the housing, each pinion gear having the teeth thereof in engagement with the teeth of the ring gear so that rotation of the ring gear relative to the housing in one direction rotates the pinion gears to move the rack members and guide vanes attached thereto inwardly of the annular fluid inlet passage, and rotation of the ring gear relative to the housing in the other direction rotates the pinion gears to move the rack members and guide vanes attached thereto outwardly of the annular fluid inlet passage.