WO2012175855A1

WO2012175855A1 - Method for diffusing a gas turbine compression stage, and diffusion stage for implementing same

Info

Publication number: WO2012175855A1
Application number: PCT/FR2012/051367
Authority: WO
Inventors: Laurent Tarnowski; Nicolas BULOT; Jérôme PORODO
Original assignee: Turbomeca
Priority date: 2011-06-20
Filing date: 2012-06-19
Publication date: 2012-12-27
Also published as: US20140133957A1; RU2013156047A; CN103635698A; PL2721305T3; FR2976633B1; JP6261498B2; JP2014517217A; EP2721305A1; CN103635698B; EP2721305B1; FR2976633A1; KR101946084B1; CA2838686A1; CA2838686C; KR20140047653A; RU2596691C2; IN2014DN00118A

Abstract

The aim of the invention is to produce an airflow by positioning flanges, the shapes of which are optimized. Non-axisymmetrical shapes in the direction of flow and in the tangential direction are thus provided. According to one embodiment, a radial or mixed gas turbine compressor diffusion stage comprises a wheel consisting of two flanges (9) between which the fluid centrifugally or inclinedly flows from the center towards the periphery. Vanes (60) of a grating are distributed among the flanges (9) in order to channel the flow of the fluid between the leading edges (6a) of said vanes (60) on the central side, and the trailing edges on the peripheral side. At least one of the flanges (9) has an inner surface (9i) comprising at least one area (Z1, Z2) having alternating concave (91) and convex (92) curvatures between two adjacent vanes (60), in at least one of two substantially perpendicular directions, namely in the direction of flow (F) along the vanes (60) and in an inter-vane tangential direction.

Description

METHOD FOR DIFFUSING A COMPRESSION STAGE OF A GAS TURBINE AND DIFFUSION STAGE USING THE SAME

DESCRIPTION

TECHNICAL AREA

The invention relates to a method of diffusing the air flow in a compression stage of a gas turbine, and a diffusion stage capable of implementing this method.

The field of the invention relates to the improvement of the performance and margin pumping of centrifugal and mixed compressors on the diffusion assembly of the stage concerned. This diffusion assembly has the function of transforming the kinetic energy of the fluid, obtained at the outlet of the centrifugal wheel constituting the stage, into static pressure. The operation must take place with a minimum of total pressure loss while maintaining a satisfactory compressor stability level in order to maintain an acceptable pumping margin for the operation of the turbomachine.

A centrifugal compressor has at least one radial compression stage, that is to say able to achieve a flow of air perpendicular to the central axis of the compressor. A mixed compressor has at least one compression stage inclined with respect to said central axis.

A diffusion assembly of a compression stage is composed of a wheel formed of two flanges between which flows the fluid centrifugally or inclined from the center to the periphery. Blades are distributed between the flanges all along the wheel. These vanes form a flow grid between the leading edges of these centrally-side blades and the trailing edges of the outer side.

STATE OF THE ART

The flanges of the radial and mixed diffusion sets are traditionally planar and the fluid passage sections between the vanes are advantageously evolutive. The evolutions of the passage sections are defined by the passage section at the neck of the diffuser and the level of slowing between the leading and trailing edges of the blade grid. .

Other architectures provide axisymmetric flanges in connection with evolutive veins for additional control of the passage section and thus optimize the diffusion in the grid.

These solutions allow a control in one dimension, that of the variation of the passage section. No control of the tangential heterogeneity of the fluid flow between two blades is achieved. This control makes it possible to regulate and optimize the flow.

STATEMENT OF THE INVENTION

The invention aims to achieve such a flow by the establishment of shaped flasks optimized because these flanges represent the largest area "wet" by the flow. Non-axisymmetric shapes in the direction of flow and tangentially are thus proposed.

More specifically, the present invention relates to a method of diffusing the air flow in a compression stage of a gas turbine comprising a diffusion assembly composed of a wheel formed of two flanges between which flows the fluid centrifugally or inclined from the center to the periphery. Blades of a grid are distributed between the flanges along the wheel to channel the flow of fluid between the leading edges of these blades on the center side and the trailing edges on the periphery side. In this method, at least one of the flanges has at least one alternation of concave and convex curvatures in at least one of two substantially perpendicular directions, namely in the flow direction along the blades and in a tangential internal direction. blades.

In these conditions, the three-dimensional shape of the vein of the fluid makes it possible to redistribute and homogenize its flow in this vein: the secondary flows, generating losses, are substantially reduced. The position of shocks in transonic blading is modified and their weakened intensity. In addition, the aerodynamic blocking input of the combustion chamber following the compression stage is also substantially reduced.

The invention also relates to a radial or mixed gas turbine compressor diffusion stage capable of implementing this method. Such a stage comprises a wheel formed of two flanges between which the fluid flows centrifugally or inclined from the center to the periphery. Blades of a grid are distributed between the flanges all along the wheel and to channel the flow of fluid between the leading edges of these blades on the center side and the trailing edges on the periphery side. At least one of the flanges has an inner face having at least one zone with alternating curvatures hollow and hump between two adjacent blades, in at least one of two substantially perpendicular directions, namely in the direction of flow along the blades and in a tangential inter-blade direction.

According to advantageous features, the diffusion stage has alternating recessed and hump zones between the vanes, in particular up to substantially 80% (preferably up to substantially 50%) of a cord. a blade, at the leading edge of the blades, with a beginning upstream of the leading edge, and / or at the trailing edge, downstream of the trailing edge. These alternating zones of hollow and hump can be applied to one and / or the other of the two centrifugal (radial) and mixed diffusion flanges, in particular symmetrically, with respect to a central plane of symmetry of the flanges, or in a parallel manner in the case where the two flanges of the stage are concerned.

PRESENTATION OF FIGURES

Other data, characteristics and advantages of the present invention will appear on reading the following nonlimited description, with reference to the appended figures which represent, respectively:

- Figure 1, a partial sectional view of a gas turbine having an air diffuser;

- Figures 2a and 2b, perspective views of a vane diffusion stage having one and two flanges; FIGS. 3a to 3c, schematic views of profiles of a flange in the direction of flow of air along a blade, with two zones with alternating curvature respectively along the blade, on the edge of flight to dawn downstream, and to the leading edge from upstream of dawn;

- Figure 4, a partial schematic view in the inter-blade tangential direction, with a flange having two zones with alternating curvature;

FIG. 5 is a diagrammatic inter-blade perspective view at the leading edge with a flange having a zone with alternating curvature; and

- Figure 6, a schematic perspective view at the trailing edge of two blades with a flat flange and a flange having a zone with alternating curvature.

DETAILED DESCRIPTION

The terms "downstream" and "upstream" qualify positioning relative to the flow of the air flow. In all the figures, identical reference signs refer to the passages of the description in which the elements corresponding to these reference signs are defined.

Referring to the schematic partial sectional view of a helicopter gas turbine 1 according to Figure 1, an air flow F is first drawn into a fresh air inlet sleeve 2, then compressed between the blades 3 of a centrifugal compressor wheel 4 and a cover 10. The turbine is of axial symmetry about an axis X'X.

The compressor 5 is here centrifugal and the compressed flow F then comes out radially from the wheel 4. When the compressor is mixed, the stream exits inclined at an angle between 0 ° and 90 ° relative to a radial direction, perpendicular to the X'X axis.

The flow F then passes through a diffuser or wheel 6, disposed at the outlet of the compressor 4, to be straightened and conveyed to inlet channels 7 of a combustion chamber 8.

To perform this rectification, the wheel 6 consists of a plurality of curved vanes 60, arranged between two flanges 9 at the periphery of the wheel 4 - here radially - and therefore of revolution around the X axis 'X. Figure 2b illustrates more precisely in perspective view the diffuser 6 with vanes 60 secured to two flanges 9. In Figure 2a, where a flange has been removed for clarity, each blade 60 has, in known manner, a face called extrados 6th and a so-called intrados face 6i. In the illustrated example, these faces are connected by a tapered leading edge 6a and a rounded trailing edge 6f, in the direction of flow of the air flow. Transversally to the extrados and intrados, each blade 60 has plane flanks 6p secured to the flanges 9.

The flanges 9 of Figures 2a and 2b are classically planar. According to the invention, at least one of these flanges 9 have, in the space E which they define between them, at least one zone with alternating curvature between two blades 60.

With reference to FIG. 3a, such a flange 9 is illustrated in profile, in the direction of flow of the air flow F along the vanes 60, of the entry at the leading edge 6a of the dawn to channel 7 outlet to the combustion chamber. Two zones with alternating curvature Z1 and Z2 are formed in the flange 9, along the blades 60. Each of these zones has on the side of the flow F, and with respect to the flat face portion 9p of the flange 9, a recessed portion. 91 and a bump portion 92. The zones Z1 and Z2 extend globally, in the example shown without limitation, about 80% of the length of the rope 6c of the vanes 60.

The flange 9 has in the figures a filamentary thickness to simplify the presentation, but it actually has a certain thickness and the alternately curved zones are formed on the inner face 9i of the flange where flows the air flow F. The outer face 9e of the flange 9 may remain flat or marry alternately curved shapes alternately bump and hollow, inverted in this example with respect to the hollow forms and bump of the inner face 9i. In the first case, the flange has a variable thickness and, in the second case, a constant thickness. The shape of the flanges may depend in particular on the method used to make the areas of alternating curvature: by milling, laser, spark erosion, forming, stamping, etc.

In FIGS. 3b and 3c, the two zones with alternating curvature Z1 and Z2 are respectively formed at the trailing edge 6f of the vanes 60 and downstream blades in the inlet of the channel 7, and / or at the leading edge 6a from the upstream inlet of the blades 60.

FIG. 4 illustrates a partial schematic view of the diffusion stage "in the tangential direction" 6t between vanes, that is to say between two vanes 60. The arrow F indicates the direction of flow of the air. The inner face 9i of the flange 9 has two zones with alternating curvature Z1 and Z2 which extend mainly between the intrados face 6i and extrados 6e two blades 60.

The perspective view inter-blades leading edge 6a of Figure 5 shows, more specifically, the flange 9 with a zone with alternating curvature Z1 between the two blades 60. The zone has the recessed curved portion 91, at the intrados 6i of a blade 60, and the portion with curvature in the bump 92, at the upper surface 6e of the other blade 60. This alternation of curvatures allows a balancing of the pressures between the intrados and the extrados of each blade 60. The section at the neck 6s between the leading edges 6a is retained.

At the trailing edges 6f, the homogenization of the flow of the air flow F is illustrated in perspective in Figure 6. With a flat flange 90 (shown hatched in the figure) between two vanes 60, a blocking aerodynamic is created in the zone Z0 with a very small amount of movement. In this configuration of the state of the art, the main air flow (arrow F) is high Mach number. In contrast, with a flange 9 with alternating curvature according to the invention, the aerodynamic blocking zone is eliminated and the flow of air F is homogenized occupying the entire passage section offered, with a lower Mach number.

The invention is not limited to the embodiments described and shown. Thus, in the illustrated examples, the curvatures are alternated in the flow direction of the fluid F but also in the tangential direction 6t. In other variants, the alternating curvature zones can be juxtaposed so that surface portions of the same curvature, hollow or hump, can be side by side.

Claims

1. Method for diffusing the air flow (F) in a compression stage (5) of a gas turbine (1) comprising a diffusion assembly composed of a wheel (6) formed of two flanges (9) between which flows the fluid centrifugally or inclined from the center to the periphery, vanes (60) of a grid being distributed between the flanges (9) all along the wheel (6) to channel the fluid flow between the leading edges (6a) of these centrally-facing blades (6) and the periphery-side trailing edges (6f), characterized in that at least one of the flanges (9) ) has at least one alternating concave (91) and convex (92) curvatures in the flow direction (F) along the vanes (6).

The method of diffusing the air flow (F) according to claim 1, wherein at least one of the flanges (9) also has at least one alternating concave (91) and convex (92) curvatures in a tangential direction (6t) between vanes substantially perpendicular to the direction of flow (F) along the vanes (6).

3. Stage of diffusion of radial or mixed gas turbine compressor capable of implementing the method according to claim 1, comprising a wheel (6) formed of two flanges (9) between which the fluid flows centrifugally or inclined from the center to the periphery, blades (60) of a grid being distributed between the flanges (9) all along the wheel (6) to channel the flow of fluid between the leading edges (6a ) of these blades (60) on the central side and the trailing edges (6f) on the periphery side, characterized in that at least one of the flanges (9) has an internal face (9i) comprising at least a zone (Z1, Z2) with alternating recesses (91) and bumps (92) between two adjacent blades (60).

4. Radial or mixed gas turbine compressor diffusion stage according to claim 3, wherein at least one of the flanges (9) has an inner face (9i) also comprising at least one zone (Z1, Z2) to alternating hollow (91) and bump (92) curves between two adjacent blades (60) in a tangential inter-blade direction (6t).

5. diffusion stage according to claim 3 or 4, characterized in that it has zones (Z1, Z2) alternately recessed (91) and bump (92) between the blades, in particular up to substantially 80% , preferably up to substantially 50%, of a rope (6c) of a blade (60).

6. Edge diffusion stage of the blades according to one of claims 4 to 5, characterized in that it has zones of hollow and hump (Z1, Z2) leading edge (6a) of blades (60), with a beginning upstream of the leading edge (6a).

7. diffusion stage in the leading edge of the blades according to one of claims 4 to 6, characterized in that it has areas of hollow and hump (Z1, Z2) trailing edge (6f) of the blades (60), downstream of the trailing edge (6f).

8. Edge diffusion stage blades according to one of claims 4 to 7, wherein these alternating zones of hollow and hump (Z1, Z2) apply to one and / or the other two centrifugal and mixed diffusion flasks (9).

9. diffusion stage according to the preceding claim, wherein these alternating zones (Z1, Z2) are applied to the flanges (9) symmetrically with respect to a central plane of symmetry of the flanges (9) or in parallel manner.