Stator adjusting mechanism for axial flow compressors

Jan. 6, 1970

U. A. PINEDA

3,487,992

STATOR ADJUSTING MECHANISM FOR AXIAL FLOW COMPRESSORS

Filed Nov. 1, 1967

Sheets-Sheet 1

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Jan. 5.; 1970 u. a. pineda 3,487,992

STATOR ADJUSTING MECHANISM FOR AXIAL FLOW COMPRESSORS

Filed Nov. 1, 1967 2 Sheets-Sheet 2

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3,487,992

Patented Jan. 6, 1970

United States Patent Office

487 992 STATOR ADJUSTING MECHANISM FOR AXIAL FLOW COMPRESSORS

Urbano A. Pineda, Sierra Madre, Calif., assignor to General Electric Company, a corporation of New York Filed Nov. 1, 1967, Ser. No. 679,866 Inf. Cl. F04d 27/00

U.S. Cl. 230—114 3 Claims

ABSTRACT OF THE DISCLOSURE

The disclosure shows an axial flow compressor comprising a casing, a rotor therein, airfoil blades mounted in circumferential rows alternately on the rotor and the casing. The blades of a plurality of the stator rows, mounted on the casing, are pivotal about axes radial of the rotor. Each of the pivotal blades in a given row is connected to a unison ring. The unison rings are respectively connected, by links, to lever arms which project from a distributor shaft. The distributor shaft is mounted on the casing longitudinally thereof. A single, reciprocable actuator has one end mounted on the casing and its opposite end connected to a lever arm projecting from the distributor shaft. Movement of the actuator simultaneously adjusts all of the pivotal stator blades to properly control air flow through the compressor.

The invention described and claimed in the United States patent application herein resulted from work done under United States Government contract FA-SS-66-6.

The United States Government has an irrevocable, non-exclusive license under said application, to practice and have practiced the invention claimed herein, including the unlimited right to sublicense others to practice and have practiced the claimed invention for any purpose whatsoever.

The present invention relates to improvements in gas turbine engines, and, more particularly, to improvements in “variable geometry” axial flow compressors used in such engines.

Axial flow compressors comprise a rotor having a plurality of circumferential rows of airfoil blades spaced along its length. Relatively stationary rows of stator vanes are mounted on the compressor casing between the rows of rotor blades, with each adjacent pair of rotor and stator blades forming a compressor stage. One accepted method of insuring proper operation of the compressor under varying operating conditions is to pivotally adjust all or several of the stator rows about axes radial of the compressor axis.

To accomplish such adjustment it is desirable to employ a single actuator which is mechanically linked to the several stator stages for their simultaneous movement in accordance with a desired schedule. Several proposals for actuation systems of this type have been made. While many are entirely workable and meet the needs of engines operating at the present time, more advanced engines require significant improvements in such aspects as weight, reliability, and envelope, i.e,, the area required for installation of the system on the engine,

To be more specific, other engine components have greatly increased reliability, especially in terms of service life, so that at the present time there is a strong demand for a stator actuation system which is extremely rugged, with a long-wear life, consistent with the desire to eliminate or greatly protract the time between engine overhauls in which the engine is thoroughly inspected, and rebuilt in many respects. The obvious approach to increasing ruggedness by increasing the size of components is at odds with the strong motivation to reduce weight in aircraft installations. In considering the matter of weight it must be remembered that the actuator forces for stator adjustment systems must be taken by the compressor casing. The compressor casing is desirably a thinwalled shell not particualrly suited to external force loadings thereon. The compressor casing must be sufficiently thick to prevent deflection which would cause the stators mounted thereon from being displaced in a manner adversely affecting compressor operation.

Another aspect of stator actuation systems is the everincreasing demand that the angular adjustment of the stator blades be extremely accurate in order to obtain more efficient compressor operation. Not only is accuracy desired in the initial installation, but, again looking to the objective of long service life, accuracy must be maintained for prolonged periods of operation.

The object of the present invention is, therefore, to provide an improved actuation system for adjusting stators in axial flow compressors and, in doing so, to fulfill the needs outlined above to obtain improved reliability, accuracy, and ruggedness.

The above objects are attained in an axial flow compressor comprising a casing having a rotor therein. Airfoil blades are mounted in circumferential rows alternately on the rotor casing. The blades of a plurality of the rows mounted on the casing are pivotal about axes radial of the rotor. Stator adjusting mechanism is provided which comprises a reciprocable actuator, one end of which is mounted in fixed relation to the casing for movement of its opposite end in a plane generally normal to the rotor axis. An axially extending distributor shaft has a plurality of lever arms projecting radially therefrom with the movable end of the actuator being connected to one of the lever arms. Linkage means connect each of the other lever arms to a given row of pivotal stator blades and provide for simultaneously adjusting all of the stator blades in reponse to movement of the actuator.

The above and other related objects and features of the invention will be apparent from a reading of the following description of the disclosure found in the accompanying drawings and the novelty thereof pointed out in the appended claims. In the drawings:

FIGURE 1 is a view in outline form of a gas turbine engine in which the present invention is embodied;

FIGURE 2 is a perspective view illustrating control mechanism seen in FIGURE 1;

FIGURE 3 is an elevation of this actuator mechanism;

FIGURE 4 is a section taken on line IV—TV of FIGURE 3;

FIGURE 5 is a section taken on line V—V of FIGURE 3; and

FIGURE 6 is a section taken on line VI—VI in FIGURE 3.

FIGURE 1 shows a gas turbine engine 10 of a type normally employed in the propulsion of aircraft. Air enters the engine 10 at 12 and is pressurized by a compressor 14 to support combustion of fuel in a combustor section 16 for the generation of a hot gas stream which is discharged from a nozzle 18 to provide a propulsive force.

The compressor 14 is itself of known axial flow type, the internal details of which are not shown herein or necessary for an understanding of the present invention. Such compressors, however, comprise a rotor having circumferential rows of airfoil blades axially spaced along its length. Between each row of rotor blades is a row of stator blades which are mounted on the compressor casing 20, which is conventionally formed by two semicylindrical shells, as seen in FIGURE 2. Selected rows of stators are pivotally journalled on the compressor shells

3,487.

so that they may be adjusted about axes radial of the main axis of the compressor. In the .present instance, and for illustrative purposes, the last five rows of stators are adjustable in this fashion to provide optimum compressor operation under varying operating conditions. _

A unison ring 22 encircles the compressor casing adjacent each row of adjustable stators (FIGS. 2 and 6). The several stators of each circumferential row have levers 24 secured thereto which are appropriately connected to the adjacent unison ring 22 by appropriate means which permit universal movement between the point of connection to the rings and the point of connection of the lever arms to the stators.

A bracket 26 (FIGS. 2 and 4) is secured to each of the unison rings and is connected to a distributor shaft 15 28 by a link 30 extending between the bracket 26 and a lever arm 32 projecting from the shaft 28. The connections between the link 30 and the bracket 26 and lever arm 32 are preferably made of spherical connections, such as a ball and socket, to permit universal movement between the 20 link 30 and the bracket 26 and lever arm 32. The links 30 are preferably turnbuckles to enable accurate initial setting of the stator blade angles.

The torque shaft 28 is journaled on brackets 34 secured to the casing 20. The journals for the shaft 28 are 25 of the spherical, self-aligning type to facilitate installation of the shaft on the compressor casing. The rod end 36 of an actuator 38 is connected to a lever arm 40, projecting from the distributor shaft 28. The opposite or cylinder end of the actuator 38 is connected to a bracket 30 42 which is secured to the compressor casing 20. The actuator 38 has appropriate hydraulic connections which direct pressurized fluid to one end or the other of the actuator to cause reciprocation of the piston end 36.

The connections of the actuator to the bracket 42 and 35 the lever arm 40 are preferably of the spherical type, employing balls and sockets.

When the rod end of the actuator is displayed (in a plane normal to the axis of rotor rotation) to oscillate the distributor shaft 28, the several stator rows connected 40 thereto, are simultaneously adjusted in a pivotal fashion to properly control air flow through the compressor. The timing of and the means for pressuring the actuator 38 to effect such adjustment is well known to those in the art and not a part of the present invention. 45

It will be apparent that the described arrangement provides a minimum of connection points between the power source, i.e., the actuator 38 and the stators which are to be adjusted. Further, the actuator may be disposed in essentially tangential relationship to the compressor cas- 50 ing and thus minimize the space envelope required for the stator adjusting mechanism. Additionally, the use of linkage mechanism for the transmission of all forces enables all of the connections to be made by way of spherical connections or spherical mountings as in the case of 55 the journals for the shaft 28, thereby insuring a high de,992 gree of reliability with a minimum of installation and manufacturing costs;

It will further be noted that the described tangential relationship of the actuator 38 enables the force loadings on the compressor casing 20 to also be essentially tangential where they are applied to the bracket 42 and the brackets 34. This minimizes the deflective forces on the compressor casing and reduces the mass of the casing required to withstand such actuation forces.