EP2715146A1

EP2715146A1 - Centrifugal compressor impeller

Info

Publication number: EP2715146A1
Application number: EP12728683.9A
Authority: EP
Inventors: Mathieu HERRAN; Laurent Pierre Tarnowski
Original assignee: Turbomeca SA
Current assignee: Safran Helicopter Engines SAS
Priority date: 2011-05-23
Filing date: 2012-05-14
Publication date: 2014-04-09
Anticipated expiration: 2032-05-14
Also published as: CN103562557B; WO2012160290A1; JP2014515451A; PL2715146T3; ES2573335T3; FR2975733A1; CN103562557A; US20140127023A1; CA2836040C; RU2583322C2; EP2715146B1; KR20140061319A; FR2975733B1; JP6009546B2; US9683576B2; CA2836040A1; KR101891853B1; RU2013156810A

Abstract

The invention relates to the field of centrifugal compressors and, in particular, to an impeller 201 of a centrifugal compressor 3 comprising a disc 202 and blades 205 secured to the disc 202 on a front surface 203 of the disc 202. An intersection point of the trailing edge 207 and the blade root 215 is further forward by at least one half thickness of the disc 202 than the blade root 215 with an intermediate diameter D of the impeller 201, and an intersection point of the trailing edge 207 and the blade head 216 is also further forward than the blade head 216 with an intermediate diameter Di of the impeller 201.

Description

CENTRIFUGAL COMPRESSOR WHEEL

BACKGROUND OF THE INVENTION The present invention relates to the field of centrifugal compressors.

The invention more particularly relates to a centrifugal compressor wheel comprising a web and vanes integral with the web on a front face of the web, each having a leading edge and a trailing edge, and a centrifugal compressor comprising such a wheel , and a turbomachine comprising such a centrifugal compressor. In this context, turbomachinery is understood to mean machines such as, for example, single or double flow turbojets, turboprops, turboshaft engines and / or turbochargers.

In the following description the terms "upstream" and "downstream" are defined with respect to the normal flow direction of fluid through the compressor. The terms "front", "rear", "axial" and "radial" are defined relative to the axis of rotation of the impeller.

A centrifugal compressor normally comprises a fixed part and a rotating part called wheel and comprising the rotating blades of the compressor. In operation, the impeller typically rotates at a high speed. It is therefore subject to centrifugal constraints.

The shape of the impeller of a centrifugal compressor is dictated by the flow of fluid through the compressor. Typically, in such a centrifugal compressor, the fluid enters the compressor in a substantially axial direction, that is to say, parallel to the axis of rotation of the impeller. The vein and the rotating blades direct the fluid radially outward, so that the fluid leaves the wheel in a direction substantially orthogonal to the axis of rotation of the wheel. The blades thus have substantially radial leading edges and trailing edges substantially axial, further from the axis of rotation of the wheel in radial direction and located axially behind the leading edges.

The veil secures the vanes rotating between them and with the compressor shaft. For this, each blade is secured to the web and located on a front face of the web. The veil also serves to delimit the foot of the flow vein of the fluid through the impeller. It is therefore normally axisymmetric and curved progressively outwards in the axial direction. By this shape of the web and the blades, the centrifugal acceleration generates a bending moment on the wheel tending to bend the periphery of the wheel forward. This bending moment increases continuously from the periphery of the wheel to the connection of the sail to the compressor shaft, and forces to maintain significant games at partial speed penalizing the performance of the machine. In order to resist this torque, it has been typically proposed to reinforce the web and the fixing means of the wheel to the rotary shaft. However, to strengthen in such a way the rotating parts of a compressor wheel imposes a very large mass penalty, because the mass that will be added near the air stream will also require a magnification of the wheel bore .

In order to avoid this disadvantage, it has been proposed in US Pat. No. 4,060,337 to largely remove the web of the impeller and connect the blades only at the base and at the periphery. However, this compressor suffers from a significant drop in the aerodynamic performance of the wheel by circulation of the intrados to the upper surface of each blade.

In British patent application GB 2472621 A, it has been proposed to connect the impeller to the rotary shaft through two rims with an axial offset to limit the presence of material on the wheel only in the functional areas. The US patent application US 2010/0098546 A1 proposes to make the wheel of the impeller hollow in its periphery, so that the mass of the periphery of the impeller is limited and positioned optimally which optimizes the compressor. However, the reductions in mass that can be obtained in these two ways are penalized by the difficulty of manufacturing the final piece monobloc. German patent DE 906 975 proposes a wheel whose sail is more advanced in the axial direction at the periphery than at an intermediate diameter of the impeller. However, this wheel also requires a reinforcing disc fixed on the blade heads, in order to restrict the deformation of the periphery of the impeller in the axial direction, which can be difficult to adapt to an existing compressor or a turbomachine in the aeronautics, in which the restriction of the masses is one of the main priorities. US Patent Application US 2007/0077147 A1 and British Patent GB 553,747 illustrate other spinning wheel spinning advanced periphery, but are not proposed to solve the problem of axial deformation of the wheel at high speeds.

Object and summary of the invention

The present invention aims to remedy these disadvantages. In a first aspect, a point of intersection of the trailing edge and the blade root is more advanced than the blade root at an intermediate diameter of the wheel. In particular, it may be more advanced by at least half a thickness of sail. In addition, a point of intersection of the trailing edge and the blade head is also more advanced than the blade head at an intermediate diameter of the impeller. In this way, the bending moment at the periphery of the impeller is reversed, and its maximum absolute value is reduced, which limits the deformations of the impeller in the axial direction, while maintaining a good aerodynamic efficiency.

According to a second aspect, at the periphery of the wheel, the front face is oriented in a substantially radial direction. This provides a rectification of the fluid flow output of the wheel which allows the use of a conventional radial diffuser downstream of the wheel.

According to a third aspect, the wheel further comprises a rim connected to a rear face of the web and adapted to be fixed to the rotary shaft. In particular, the rim may comprise a radial attachment leek. An efficient and comparatively light attachment of the impeller to the rotary shaft of the compressor can thus be obtained. According to a fourth aspect, the centrifugal compressor further comprises a cover covering the blades so as to define, with the web, a vein of fluid between the leading edges and the vanishing edges of the blades. The aerodynamic losses of the centrifugal compressor can thus be substantially reduced by limiting in this way an overflow of fluid from the intrados to the extrados of each blade. In particular the cover may then comprise at least one attachment point closer to the trailing edges of the rotor blades than the leading edges of the rotor blades. As the axial displacement of the radial periphery of the wheel at high speed can be limited by the non-bijectivity in the axial direction of the curve formed by the front face of the web, the axial attachment of the cover can be positioned closer to the periphery of the wheel , which limits the clearance between the cover and the rotor blades at the periphery of the impeller in partial regimes and thus increase the efficiency: aerodynamic. Alternatively, the lid may be integral with the blades, so as to form a flanged wheel. Brief description of the drawings

The invention will be better understood and its advantages will appear better, on reading the detailed description which follows, of embodiments shown by way of non-limiting examples. The description refers to the accompanying drawings in which:

- Figure 1 is a schematic longitudinal section of a turbomachine comprising a centrifugal compressor;

- Figure 2 is a longitudinal section of a centrifugal compressor wheel of the prior art;

FIG. 3 is a longitudinal section of a centrifugal compressor according to a first embodiment of the invention;

- Figure 4 is a longitudinal section of a centrifugal compressor wheel according to a second embodiment of the invention.

Detailed description of the invention A turbomachine, more specifically in the form of a turbine engine 1, is illustrated schematically for explanatory purposes in FIG. 1. This turbine engine 1 comprises, in the direction of flow of a working fluid, an axial compressor 2, a centrifugal compressor 3, a combustion chamber 4, a first axial turbine 5, and a second axial turbine 6. In addition, the turbine engine 1 also comprises a first rotary shaft 7 and a second rotary shaft 8 coaxial with the first rotary shaft 7.

The second rotary shaft 8 connects the axial compressor 2 and the centrifugal compressor 3 to the first axial turbine 5, so that the expansion of the working fluid in this first axial turbine 5 downstream of the combustion chamber 4 serves to actuate compressors 2 and 3 upstream of the combustion chamber 4. The first rotary shaft 7 connects the second axial turbine 6 to a power output 9 positioned downstream and / or upstream of the machine, so that the subsequent detent working fluid in the second axial turbine 6 downstream of the first axial turbine 5 serves to actuate the power output 9.

Thus, the consecutive compressions of the working fluid in the axial compressors 2 and centrifugal 3, followed by a heating of the working fluid in the combustion chamber 4, and its expansion in the second axial turbine 6 allow the conversion of a part of the thermal energy introduced by combustion into the combustion chamber 4 in mechanical work extracted by the power output 9. In the turbine engine illustrated, the driving fluid is air, to which is added and in which a fuel is burned in the combustion chamber 4, fuel such as, for example, a hydrocarbon.

In operation, the rotary shafts 7 and 8 rotate at speeds of the order of 5000 to 60000 revolutions per minute. The rotating parts of the compressors 2. and 3 and the turbines 5 and 6 are therefore subjected to great efforts by the centrifugal forces. Turning now to Figure 2, one can appreciate how these centrifugal forces act on the wheel 101 of a conventional centrifugal compressor known to those skilled in the art. This wheel 101 has a sail 102 substantially axisymmetric and having a front face 103 and a rear face 104. The blades 105 are fixed by the blade roots 115 on the front face 103 of the sail 102. Each blade 105 also has a blade head 116 opposite to the blade root 115, a leading edge 106 with a substantially radial orientation and a trailing edge 107 with a substantially axial orientation, located radially outside and axially behind the leading edge 106. In operation, the working fluid is thus sucked by the front

108 of the wheel 101 and directed by the blades 105 to the periphery 109 of the impeller 101, along a stream of fluid defined internally by the web 102 and outside by a non-rotating cover 110 of the centrifugal compressor close heads of dawn 116.

On its rear face, the web 102 is secured to a rim 111 with a leek for attachment to the rotary shaft. The rim 111 and the leek thus define a plane A for transmitting the radial forces of the wheel 101 to the rotary shaft. Because of the high speeds of rotation of the wheel 101, the centrifugal forces exerted on the wheel 101 represent a preponderant part of these radial forces. However, since the centrifugal force F _c is proportional to the square of the angular rotation speed ω multiplied by the distance to the axis of rotation X of the impeller 101, according to the formula ω ² Γ, the centrifugal forces exerted on the periphery

109 of the wheel 101 will prevail. Thus, in the illustrated conventional wheel 101, the centrifugal forces F _c acting on the periphery 109 of the wheel 101 will create a bending moment M _F in the wheel 101 tending to tilt the periphery 109 of the wheel 101 forward. This bending moment M _F increases continuously from the periphery 109 of the wheel 101 to the junction of the veil 102 with the rim 111. In order to limit the bending of the wheel 101, the veil 102, the rim 111 and the leek must be reinforced. which results in a considerable increase in the total mass of the wheel 101. In addition, to accommodate the forward movement of the periphery 109 of the wheel 101, it is normally necessary to grant the periphery of the wheel 101 an important set of wheels. _p partial regime between the blade heads 105b and the cover 110, which results in significant aerodynamic losses, or even arranging relatively complex cover mounting structures 110, to induce a displacement of the cover 110 forward when the compressor rises. Figure 3 shows the centrifugal compressor 3 with a wheel 201 according to a first embodiment of the invention. This wheel 201 also comprises a sail 202 substantially axisymmetric and having a front face 203 and a rear face 204. As in the wheel illustrated in Figure 2, the blades 205 are fixed by the blade roots 215 on the front face 203 of the 202 and each also have a blade head 216 opposite to the blade root 215, a leading edge 206 with a substantially radial orientation and a trailing edge 207 with a substantially axial orientation, located radially outwardly and axially behind the leading edge 206. Around the periphery of the impeller 201, the compressor 3 comprises a conventional radial diffuser 212 with straightening vanes 213. In operation, the working fluid is thus also sucked by the front 208 of the impeller 201 and directed by the blades 205 towards the periphery 209 of the impeller 201, along a fluid stream defined inside by the web 202 and outside by the non-rotating cover 210, to reach the diffuser radial 212.

On its rear face, the web 202 is also secured to a rim 211 with a leek attachment to the rotary shaft. However, in this wheel 201, the web 202 is curved so that a peripheral segment of the web 202 is inclined forwardly from an intermediate diameter D ,, thus having a concave front face 203. Thus, at the periphery 209 of the impeller 201, this front face 203 is advanced by a distance L with respect to the intermediate diameter D 1. This distance L is substantial, and in particular it is greater than half the thickness d of the web 202 at the periphery 209 of the impeller 201. Consequently, on a peripheral segment 202c facing forward, the centrifugal forces F _c generate a bending moment M _F tending to bend this peripheral segment 202c, not forwards, but in the opposite direction, towards the rear. The modulus of this bending momentum M _F increases from the periphery 209 to the intermediate diameter D, where it reaches a local maximum. Then, however, it decreases until eventually reversing the direction of the bending moment M _F. Thus, as the bending moment M _F does not increase continuously from the periphery 209 to the junction of the web 202 with the rim 211, it reaches substantially lower levels than in the wheel 101 of the state of the art, thus allowing the use of a lighter rim 211 and leek. In addition, since the axial displacement of the periphery 209 of the impeller 201 is reduced, the clearance d _p between the tips of the blades 205 at the periphery of the impeller 201 and the cover 210 can also be reduced, and this cover 210 can be fixed in such a way that comparatively rigid on an attachment point 214 closer to the back of the cover 210 and therefore: trailing edges 207 than the front of the cover 210 and the leading edges 206. An additional advantage lies in the axial space requirement reduced wheel 201, and in particular in the reduced axial distance between the inlet of the working fluid to the front of the wheel 201 and its output periphery 209 of the impeller 201. In particular in a turbomachine such as the turbine engine 1 illustrated in Figure 1, this makes it possible to substantially advance the elements downstream of the compressor, that is to say, in the embodiment illustrated, the hot parts such as the combustion chamber 4, and the first and second axial turbines 5 and 6, thereby reducing the overall axial size of the turbomachine. In the embodiment illustrated in FIG. 3, the outer edge of the peripheral segment 202c of the web 202 is curved so as to reorient the front face 203 of the web 202 in the radial direction, and thus to straighten the stream of fluid in the radial direction in order to be able to use the conventional radial diffuser 212 illustrated. However, in an alternative embodiment, illustrated in FIG. 4, in which each equivalent element receives the same reference numeral as in FIG. 3, the fluid stream is not rectified radially, which makes it easier to the production of the wheel, even if the diffuser downstream of the wheel must be adapted.

A centrifugal compressor with a wheel 201 such as those illustrated in FIGS. 3 and 4 may be used, inter alia, in turbomachines such as the turbine engine 1 illustrated in FIG. 1, but also single or double flow turbojets, turboprops , turboshaft engines and / or turbochargers. By its reduced mass, it will be particularly advantageous in an aeronautical use, such as that, for example, for the propulsion of fixed and / or rotary wing aircraft, with or without a pilot, lighter or heavier than air. However, other non-aeronautical applications known to those skilled in the art may also be envisaged, such as, for example, the propulsion of land and / or marine vehicles, including air cushion vehicles, electrical generation, pumping stations, and / or other industrial applications. Such a centrifugal compressor may constitute the only stage of a compression system, or one or more of the stages of a multi-stage compression system, axial, mixed or centrifugal, that is to say comprising at least one centrifugal stage and an axial stage or a mixed stage.

Although the present invention has been described with reference to specific exemplary embodiments, it is obvious that various modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various illustrated embodiments can be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

Claims

1. Wheel (201) centrifugal compressor (3) having a web (202) and blades (205) integral with the web (202) on a front face (203) of the web (202), each having a blade root (215), a blade head (216), a leading edge (206) and a trailing edge (207), the impeller (201) being characterized in that a point of intersection of the trailing edge (207) and blade root (215) is more advanced by at least half a sail thickness (202) than the blade root (215) at an intermediate diameter (D,) of the wheel (201) , and a point of intersection of the trailing edge (207) and the blade head (216) is also more advanced than the blade head (216) at an intermediate diameter (D,) of the wheel (201) .

2. Wheel (201) centrifugal compressor (3) according to claim 1, wherein, in a periphery (209) of the wheel (201), the blade root (215) is oriented in a substantially radial direction.

3. Wheel (201) centrifugal compressor (3) according to any one of claims 1 or 2, further comprising a rim

(211) connected to a rear face (204) of the web (202) and adapted to be fixed to a rotary shaft.

Centrifugal compressor wheel (201) according to claim 3, wherein the rim (211) comprises a radial attachment leek.

5. Centrifugal compressor (3) comprising a wheel (201) according to any one of claims 1 to 4.

6. Centrifugal compressor (3) according to claim 5, further comprising a cover (210) covering the blades (205) so as to delimit, with the web (202), a vein of fluid between the leading edges (206). ) and the trailing edges (207) of the vanes (205).

The centrifugal compressor (3) according to claim 6, wherein the lid (210) has at least one attachment point (214) closer to the trailing edges (207) of the blades (205) of the impeller (201) than leading edges (206) of the blades (205) of the impeller (201).

8. Centrifugal compressor (3) according to claim 6, wherein the lid is integral with the vanes (205).

9. A turbomachine comprising a centrifugal compressor (3) according to any one of claims 5 to 8.