FR2560639A1 - MEANS FOR CONTROLLING AIR - Google Patents

Abstract

AIR CONTROL MEANS ALLOWING THE COOLING OF A DAWN MEANS. THEY INCLUDE: A PLATFORM 26 FIXED RIGIDLY TO A RADIALLY INNER END 28 OF THE AERODYNAMIC PROFILE; THE PLATFORM 26 BEING GENERALLY PLACED ON A ROTATING ANNULAR SURFACE 16, AND THIS SURFACE DEFINING EXTERIOR 34 AND INTERIOR SPACES 36, SO THAT IN A FIRST POSITION AN EDGE 38 OF THE PLATFORM 26 INTERVIEWS SURFACE 16 AND IN A SECOND POSITION EDGE 38 IS MOVED RADIALLY TOWARDS THE EXTERIOR OF SURFACE 16 THUS ALLOWING THE FLUID TO COMMUNICATE BETWEEN EXTERIOR 34 AND INTERIOR 36. APPLICATION TO GAS TURBINE ENGINES.

Description

This invention generally relates to air control means

  for a gas turbine engine and, more particularly, a means for supplying air to the

  hub of a rotating aerodynamic profile.

  Two types of engines are commonly available and used to propel aircraft: the turbofan and the turboprop. The unit supplying energy is common to both engines. This unit conventionally comprises a compressor, a combustion chamber, and a turbine on

  all arranged in series. Compressed air from the compressor

  is mixed with the fuel and burned in the chamber.

  combustion chamber to provide a high velocity gas stream that expands in the turbine and from which energy is extracted. Part of this energy is used to implement the compressor and the rest leads to the

blower or propeller.

  Although the temperature increases are a result of the work done in the compressor, the highest temperatures encountered in the engine

  are those of the combustion chamber and the turbine.

  Compressed air for cooling these components is conventionally obtained from the compressor, the pipeline of

  blower or otherwise is drawn from the atmosphere.

  In most turbo-driven engines

  blower or turboprop, blower or propeller 2 -

  is located generally in front of the gas generator. AIN-

  if, in such applications, the hub structure of the blades of these thrusters operates in a relatively low temperature environment thus eliminating the need for cooling of the hub structure. However, it is known to locate the thruster

  typically at the back of the gas generator according to a

  figuration called "pusher". New concepts have been described

  figurations "pusher" for turbo-driven engines

  blower or turboprop. Because of the proximity

  narrow propeller blades with the turbine and the chamber.

  combustion in these configurations, the structures of

  dawn hub under certain flight conditions will be

  its at relatively high temperatures; Air temperatures in the hub area

  will vary according to flight conditions. For example,

  periods of relatively high energy demand

  such as take-off, temperatures in tur-

  and the combustion chamber are raised with

  the result of the dawn hub structure temperatures

  Vees. Lightweight and inexpensive materials and variable pitch blade hub structures frequently have limitations

  relatively low temperature. So,. the cooling

  A hub structure may be required during high power take-off conditions. Conversely,

  temperatures stabilize at a lower level

  cruising operating conditions

  permanent and cooling may not be necessary.

  Since every time a cooling system is used

  the yield is reduced, the use of cooling

  only when necessary is of particular interest

  tain. Thus, means for automatically changing the amount of cooling air required for the hub of

such blades are desired.

  The object of the present invention is to provide: - a new improved air control means;

  a new and improved way of cooling

  hub re of a propeller blade; an automatic means of varying the quantity

  S air cooling hub a propeller blade.

  According to the present invention there is described air control means used in a gas turbine engine comprising a variable pitch rotary aerodynamic profile and

  means for varying the pitch of the profile. The means of communication

  air supply shall comprise a platform rigidly

  a radially inner end of the aerodynamic profile

  than. This platform is generally placed on a rotating surface, which defines external spaces

  and inside. In a first position, an edge of the

  you form almost all the surface. In one

  position, the edge is moved radially outwards

  from the surface, thus allowing the fluid

  flow between the outer and inner spaces.

  The following description refers to the figures

  which respectively represent: FIG. 1, a view of a turboprop engine of

  type "pusher" comprising an embodiment of the pre-

  this invention; - Figure 2, a perspective view of a rotating nacelle and the blades shown in Figure 1 with the blades set at a large pitch;

  3, a view of the hub of a blade representing

  Figure 2; - Figure 4, a perspective view similar to that of Figure 2 with the blades set at a small pitch; - Figure 5, a view of the hub of the blade shown

figure 4.

  This invention can be used in any gas turbine engine that has a variable pitch rotary airfoil where it is desired to control the flow of air to the engine.

  through an annular rotating surface with respect to which

  the profile is positioned. As an illustration, the

  vention will be described for a propeller dawn on a

the rotating one.

  FIG. 1 shows a turboprop of the "pusher" type 10. The embodiment represents blades

  propeller rotating in the opposite direction 12 and 14 placed respectively

  on surfaces or nacelles 16 and 18 rotating in

  opposite direction respectively, and connected to tower turbines

  in opposite directions 22 and 24. It will be clear from

  the following discussion that the present invention is

  also applies to gas turbine engines with a single

  propeller dawn stage. The counter-rotating configuration

  described here is only as an example only.

  The engine 10 comprises a gas generator for producing combustion gases which drive the turbines 22 and 24 against each other. Each turbine 22 and 24 is

  connected to the rotating annular surfaces 16 and 18 respectively

tively.

  Each blade 12 and 14 has means for varying

  step in order to improve the efficiency of the motor during all phases of operation. Figures 2 and 3 show in detail the control means

  of air with the blades 12 set at a pace suitable for the

  cruising operation of the engine. A generally disk-shaped platform 26 is rigidly attached to the blade 12 by the blade root 28 forming a portion, or area, of the surfaces 16 and 18. Thus, when when the blade 12 changes

  by rotation about a radial axis 50, the platform

  me 26 moves with her. Means for changing the pitch of a rotating airfoil are well known in the art. For example, mechanical, hydraulic means

  or electric or pneumatic are available to provoke

  to couple a couple on the structure of the hub 32 of the dawn 12

  to provide the necessary maneuvering force.

  Figures 2 and 3 show the platform being placed generally on the annular surface

  16. The surface 16 as well as the platform 26 defines

  Nite outer 34 and inner 36 spaces. The temperature in the space 36 is generally hot because of its proximity to the turbine 22. The temperature in the zone 36

  depending on the operating mode of the motor 10. For example,

  the turbine 22 operates at a higher temperature during takeoff than during steady state operation.

  permanent cruise. Unlike space 36 which compares

  door high temperatures, space 34 is usually

  at room temperature much lower.

  The air control means of the present invention

  provide variable amounts of cooling air.

  In FIG. 2 and 3, the platform 26 has a generally circular cross-sectional shape when viewed radially and is placed relative to the hub structure 32 according to the pitch setting of the blade 12.

  the rotating annular surface 16. In this first position,

  the platform 26 substantially marries the surface 16.

  Thus, in the peripheral direction, the surface at the perimeter of the platform 26 generally follows the contour of the surface

  16. In the embodiment shown in FIG.

  face 16 is generally cylindrical. However, the invention also applies to conical surfaces as well

  surfaces that do not have a linear slope.

  FIGS. 4 and 5 represent the means of

  Means as shown in FIGS. 2 and 3 with the platform 26 which has been rotated by means of a modification of the pitch of the blade 12 so as to expose the edge 38 of said platform. As will be evident from the geometry, the edge 38 is moved radially towards

  the outside from the surface 16 and defines an opening

  40 between them. The opening 40 thus allows the fluid

  to pass between the outside spaces 34 and inside 36.

  - 6 - This allows the cooling air 41 to enter

  space 36 and cool the hub structure 32.

  During steady-state operation of the

  10, as for example during the cruising speed, the pitch of the blade 12 will be such that the platform 26 and the edge 38 substantially match the surface 16. During the higher power operating mode of the engine 10, we will adjust the blade 12 with a smaller step, represented in

  FIG. 4, thus exposing the edge 38 and the opening 40.

  if, while the opening 40 is practically closed during

  cruising speed, an increased amount of cooling air

  is available during the operational periods

  motor at higher temperature.

  The nacelle 16 rotates in the direction indicated by the arrow 42. Thus, the direction of the air flow with respect to the nacelle 16 due to the rotation of the nacelle 16 is represented by the arrow 44. The direction of the air on the nacelle 16 due to the forward displacement of the engine 10 is generally axially rearward as shown

  by arrow 43. The relative displacement of air by

  port to the platform 26 is represented by the arrow 46, which is the vector-sum of the arrows 43 and 44. It will appear

  clearly from what has just been said above that the

  40 looks practical forward with respect to the 46 direction of the air. This orientation makes it possible to obtain

  an increase in the available air pressure contributes

  thus buoyant to increase the air flow rates for

cool the way.

  It will be clear to those skilled in the art that the

  present invention is not limited to the modes of

  specific conditions described and represented here. Nor is the invention limited to the air control means for propellers or turbofan blades. Rather the invention

  also applies to the air control means for all

  rotary aerodynamic threads with variable pitch.

-7-

Claims (7)

CLAIMS -   1. In a gas turbine engine having a rotary variable pitch aerodynamic profile, comprising means   to vary the pitch of said profile, control means   of air, characterized in that they comprise:   - a platform (26) fixed rigidly to an   radially inner trough (28) of the airfoil; the platform (26) being generally placed on a rotatable annular surface (16), and this surface defining external (34) and interior (36) spaces,   so that in a first position an edge (38) of the   form (26) matches the surface (16) and in a second   the edge (38) is moved radially outwardly of the surface (16) thereby allowing the fluid to communicate   between the outer (34) and inner (36) spaces.   2. Air control means according to the claim   1, characterized in that the aerodynamic profile is a   thruster and that the first position corresponds to   at a dawn step for steady state operation permanent engine.   3. Air control means according to the claim   1, characterized in that the edge (38) and the surface (16) de-   end between them an opening (40), which is practically   closed in the first position and open in the second position.   4. Air control means according to the claim   3, characterized in that the aerodynamic profile is a   be of thruster and in that the second position is practically a step of dawn for the operating regime high engine.   5. In a gas turbine engine having a rotating aerodynamic profile with variable pitch, and means for varying the pitch of this profile, air control means, characterized in that they comprise:   È, 5 - a platform (26) fixed rigidly to an ex-   Radially inner trough (28) of the aerodynamic profile; the platform being generally placed on a rotatable annular surface (16), the surface defining outer (34) and inner (36) spaces so that in a first position the platform (26) substantially conforms to the surface (16), and in a second position an edge (38) of the platform (26) is moved radially outwardly from the surface (16) thereby allowing the flow of air from space outside (34) to the interior space- (36).   An air control means according to claim 1, characterized in that the aerodynamic profile is a propeller and the edge (38) and the surface   (16) define between them an opening (40) which is practically   closed in the first position and open in the second position.   7. An air control means according to claim 6, characterized in that the opening (40) in the second position looks substantially forward with respect to the relative displacement of the air.