US3567331A - Variable vane cascades - Google Patents

Abstract

A TURBINE NOZZLE INCLUDES AN ANNULAR ROW OF RADIALLY DIRECTED BLADES. THE AREA OF THE NOZZLE THROAT IS VARIED BY PLUTS WHICH ARE MOVABLE WITH OR AGAINST THE DIRECTION OF FLOW THROUGH THE NOZZLE INTO THE SPACES BETWEEN THE BLADES. THE PLUGS ARE STREAMLINED MEMBERS AND MAY BE INDIVIDUAL MEMBERS IN EACH INTERBLADE PATH OR MAY BE PORTIONS OF A RING EXTENDING AROUND THE NOZZLE AXIS IMMEDIATELY DOWNSTREAM OF THE NOZZLE. PROVISIONS ARE MADE FOR COOLING THE PLUGS.

Description

3,567,331 VARIABLE VANE CASCADES Leo A. Corrigan and Earle R. Wall, Jr., Indianapolis, Ind., assignors to General Motors Corporation, Detroit,

Mich.

Filed July 25, 1969, Ser. No. 844,885 Int. Cl. F01d 25 24, 17/00 U.S. Cl. 415-126 7 Claims ABSTRACT OF THE DISCLOSURE A turbine nozzle includes an annular row of radially directed blades. The area of the nozzle throat is varied by plugs which are movable with or against the direction of flow through the nozzle into the spaces between the blades. The plugs are streamlined members and may be individual members in each interblade path or may be portions of a ring extending around the nozzle axis immediately downstream of the nozzle. Provisions are made for cooling the plugs.

The invention herein described was made in the course of work under a contract or subcontract thereunder with the Department of Defense.

Our invention is directed to variable vane cascades suitable for use as stator vane rings in turbomachines such as compressors and turbines, and for other uses. It is also directed to means for cooling the structure so that it is suited for use in very high temperature turbines. In a structure according to our invention, the turbine nozzle includes a ring of fixed vanes defining between them paths for flow of gas, each path having a throat between the trailing edge of one vane and the adjacent vane. To vary the area of the nozzle, a plug is moved within the throat varying the throat area by virtue of the variation of plug cross section area at the throat. There may be an individual plug between each two adjacent vanes or there may be a continuous ring, the portions of which between vanes each constitute a plug.

The principal objects of our invention are to provide a practical variable vane cascade structure; to provide a variable vane cascade in which the variation is accomplished by movement of a ring of plugs extending generally circumferentially of the nozzle into the spaces between the vanes; to provide a structure of the kind described in which the plug structure has provisions for cooling; and to provide a variable area vane cascade having simple reliable structure particularly adapted to the requirements of practice.

The nature of our invention and its advantages will be clear to those skilled in the art from the succeeding detailed description of preferred embodiments of the invention and the accompanying drawings thereof.

FIG. 1 is a sectional view of a variable turbine nozzle taken in a plane containing the axis of rotation of the turbine and with parts broken away and in section.

FIG. 2 is an axonometric view of a nozzle throttling plug.

FIG. 3 is an axonometric view of a nozzle throttling plug ring.

FIG. 4 is a schematic view illustrating the movement of the plugs.

Before proceeding to a description of the structure in which our invention is particularly embodied, it is well to point out that the structure, except as otherwise described, may be of a type shown in copending applications, of common ownership with this, of Earle R. Wall for Variable Turbine Nozzles, Ser. No. 836,423, filed June 25, 1969, and for Variable Vane Cascades, Ser. No. 836,422, filed June 25, 1969. To the extent that United States Patent 3,567,331 Patented Mar. 2, 1971 structures disclosed herein correspond to those of the prior applications, they may not be described in detail; however, We believe that all structure is described here to the extent requisite to a full understanding of our invention. Reference may be made, if needed, to the prior applications for details described therein.

Referring first to FIG. 1, this illustrates a variable nozzle or stator ring for an axial flow turbine, which may be of various known types. The turbine includes a case 5 to which is fixed the outer shroud ring '6. The turbine also includes a support 7 within the engine which is fixed by means not illustrated to the turbine case 5. An inner shroud ring assembly 8 is fixed to the support 7. Fluid flow directing vanes 10 disposed in an annular array extend radially from the outer shroud 6 to the inner shroud 8.

The outer shroud ring 6 includes a structural ring 11 including a flange '12 fixed to the case 5 by a ring of bolts 13. The outer shroud also includes a porous facing defined by an upstream facing ring 14 and a downstream facing ring 15, the former being fixed to the structural ring 11 by bolts 16 and the latter being secured by a snap ring 18. The inner shroud ring 8 includes an inner structural ring 19 having a flange fixed to the support 7 by suitable means (not illustrated). It also includes an upstream porous facing ring 20 and a downstream porous facing ring 22, these being held in place on the structural ring 19 by rings 23 which snap into place, this structure being part of the subject matter of the Wall applications. The division of the porous facings into upstream and downstream rings provides for mounting them around the vanes 10.

Each vane 10 includes an airfoil 24 which defines the leading edge, face, and trailing edge of the van, the trailing edge being indicated at 25. The airfoil 24 is fixed to a tubular spine 26 which extends to the structural rings 11 and 19 and supports the vane from them. Spine 26 is slidably mounted in a bore 27 in a flange of the inner structural ring 19 and is fixed to the outer structural ring 11, the outer end of the spine extending through a hole 28 in the ring and being retained by a contracting snap ring 29. The vane bears flanges 30 at its ends which extend over the outer and inner surfaces of the facing rings to minimize leakage of cooling air between the facings and the vane.

Air for cooling the shrouds and vanes may enter the outer shroud through openings 36 and the inner shroud through openings 37 and may flow into the vane through the open ends of the vane and also into the spine 26 through open ends of the spine. The structure of the cooling means of the shrouds and vanes is immaterial to this invention.

Our invention is directed to the means for varying the flow area of the nozzle or area of the nozzle throat which involves plugs 40 (FIG. 1) movable in the direction of fluid fio'w into or away from the nozzle throat adjacent the trailing edge of one vane and the approximate mid-chord of an adjacent vane. The plug means 40 may take either of the forms shown in FIGS. 2 and 3.

The device of FIG. 2 is a short airfoil 41 normally of symmetrical section with a leading edge at 42 and a trailing edge at 43. The ends of the airfoil 41 are closed by caps 45. The structure of the plug means 40 is of porous material so that cooling air introduced to the interior of the plug means can diffuse through the entire outer surface for transpiration cooling.

The plug means 40 of FIG. 3 is defined by a ring airfoil 48 having a similar cross section to the airfoil 41. The ring may be a single 360 ring extending around the turbine nozzle or it may be in sections or segments if desired. The ring airfoil 48 has a notch 49 at the position of each vane defined by radial walls 50. The surfaces of the ring airfoil 48 likewise are of porous material for transpiration cooling.

Referring to FIG. 1, the plug means is supported by hollow struts 51, of streamlined cross section to minimize resistance to air flow, there being one strut 51 for each airfoil 41 and a suitable number of struts 51 for the ring airfoil 48. The struts 51 are integral with a mounting and actuating ring 54 of rectangular cross section which is mounted between the support ring 11 and downstream facing ring 15 and supported by these so that it may slide forward and aft in the structure and also move circumferentially to a slight extent. The strut 51 extends through a skewed slot 55 in the facing ring '15 and the actuating ring 54 covers it. An offset connecting bracket 56 includes a head 57 welded to the ring 54 and terminates in a pin 59 which connects it to an actuating arm 60.

An appropriate number of actuating arms 60 may be distributed evenly around the circumference of the nozzle, each such arm being pivoted at 61 on a flange of the structural ring 11 and having mounted in it a spherical bearing device 62 which receives the pin 59. The arms 60 may be rotated in unison by a unison ring 64 coaxial with the turbine and disposed within the case 5, which is connected to the arms 60 through spherical bearings 65. Brackets 56 extend through skewed slots 66 in the structural ring 11.

The nature of the movement of the plug means will be clearly apparent from the somewhat schematic showing in FIG. 4. As the arm 60 is swung in the are indicated by the arrow A, the plug means 40 is moved in a corresponding are indicated by the arrow B, and is thus moved to a greater or lesser extent into the throat between the adjacent vanes 10. It will be noted that the intermediate connecting means between the pin 59 and the plug means are not illustrated in FIG. 4.

The plug means 41 move together as a unit although each is a separate part. The ring 48 moves as a unit and has a suflicient number of struts 51 connecting it to the mounting and actuating ring 54 to provide suitable support and conduct sutficient cooling air to it.

The cooling air which is admitted through holes 36 to the interior of the shroud 6 flows in part through a ring of holes '68 in the leading edge of the ring 54, through the hollow struts 51, and into the chamber 70 within the plug means. Since the walls of the plug means (including walls 45 in FIG. 2) are a suitable temperature resisting alloy and have a controlled degree of porosity, the air transpires through the plug surface to cool the plug and protect 'it against the hot gases discharged through the turbine nozzle.

It will be apparent to those skilled in the art that our invention provides means for varying to a limited extent the area'of a turbine nozzle for various purposes of engine control known to those skilled in the art. The structure is of a simple and feasible nature and is particularly suited to hot environments because of the provisions for cooling.

- The detailed description of preferred embodiments of the invention for the purpose of explaining the principles thereof is not to be considered as limiting or restricting the invention, since many modifications may be made by the exercise of skill in the art. We claim:

1. A turbomachine structure comprising, in combination, an annular support, an annular cascade of fixed flow directing vanes extending spanwise of the vanes from the support, the vanes defining a fluid flow path through each space between adjacent vanes, area-varying plugs disposed between adjacent vanes, and means mounting the plugs for concurrent movement in the direction of flow through the said paths toward and from the entrance to said paths so as to vary the flow path throat area, the plugs being airfoil structures with span extending circumferentially of the vane cascade.

2. A structure as defined in claim '1 in which the mounting means includes a ring movably mounted on the support.

3. A structure as defined in claim 2 including streamlined struts extending from the ring to the plugs.

4. A structure as defined in claim 2 in which the plugs are defined by a distinct plug between each two adjacent vanes, each plug being individually connected to the ring.

5. A structure as defined in claim 2 in which the plugs are defined by a'ring airfoil having notches to References Cited UNITED STATES PATENTS 2,372,518 3/1945 Robinson 415148 3,249,333 5/1966 Corbett, Ir. 4l5161 3,433,015 3/1969 Sneeden 4l6-231 HENRY F. RADUAZO, Primary Examiner U.S. Cl. X.R. 415l15,148,

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