Impeller with chord-wise blade thickness variation

Abstract

The present invention relates to an impeller with a chord-wise blade thickness variation. An impeller for a centrifugal compressor, the impeller comprising: a hub defining an axis of rotation, the impeller being rotatable about the axis of rotation; and a blade extending from the hub, the blade having a leading edge, a trailing edge, and a chord defined between the leading edge and the trailing edge, a pressure side of the blade and a suction side of the blade opposite to the pressure side, a blade thickness defined transversely between the pressure side and the suction side, the blade thickness decreasing over at least 40% downstream of the chord, the blade thickness having a trailing edge thickness value at the trailing edge between 40% and 80% of a maximum thickness value of the blade thickness.

Description

Technical Field

[0001] The present application relates generally to centrifugal compressors of gas turbine engines and, more particularly, to impellers of such centrifugal compressors. Background Art

[0002] Centrifugal compressors are usually composed of at least two main components, namely: an impeller and a diffuser. The impeller includes a hub, which is mounted to a drive shaft so as to rotate therewith. The blades (i.e., blades) of the impeller extend from the hub and are arranged to redirect the axially directed incoming airflow radially outward toward a diffuser located downstream of the impeller. However, stresses may be applied to the impeller, usually in or near the hub. Such stress concentrations may adversely affect the life of the impeller. At the same time, the large volume (vane bulk) of the blades is generally considered to be detrimental to the aerodynamic characteristics of the flow transmitted from the impeller to the diffuser, thereby making it undesirable to increase the size when solving the stress concentration problem. Therefore, there is still a need for improvement. Summary of the invention

[0003] In one aspect, an impeller for a centrifugal compressor is provided, the impeller comprising: a hub defining an axis of rotation, the impeller being rotatable about the axis of rotation; and a blade extending from the hub, the blade having a leading edge, a trailing edge, and a chord defined between the leading edge and the trailing edge, a pressure side of the blade and a suction side of the blade opposite to the pressure side, and a blade thickness defined laterally between the pressure side and the suction side, the blade thickness decreasing over at least 40% downstream of the chord, the blade thickness having a trailing edge thickness value at the trailing edge between 40% and 80% of a maximum thickness value of the blade thickness.

[0004] An impeller as described herein may also include, in whole or in part, one or more of the following additional features.

[0005] Wherein, a 0% chord position is defined at the leading edge, and a 100% chord position is defined at the trailing edge, the trailing edge thickness value is the thickness value at the 100% chord position, and the thickness value at the 100% chord position is between 45% and 75% of the maximum thickness value.

[0006] The thickness value at the 100% chord position is a thickness value between 50% and 75% of the maximum thickness value.

[0007] The thickness value at the 100% chord position is a thickness value between 45% and 55% of the maximum thickness value.

[0008] The thickness value at the 100% chord position is a thickness value between 60% and 70% of the maximum thickness value.

[0009] The thickness value at the 100% chord position is a thickness value between 60% and 75% of the maximum thickness value.

[0010] The thickness value at the 100% chord position is a thickness value between 65% and 70% of the maximum thickness value.

[0011] The thickness value at the 100% chord position is a thickness value between 70% and 75% of the maximum thickness value.

[0012] The blade thickness has a thickness value between 50% and 90% of the maximum thickness value at a 90% chord position.

[0013] The impeller of claim 9, wherein the thickness value at the 90% chord position is a thickness value between 55% and 80% of the maximum thickness value.

[0014] The thickness value at the 90% chord position is a thickness value between 55% and 65% of the maximum thickness value.

[0015] The thickness value at the 90% chord position is a thickness value between 70% and 80% of the maximum thickness value.

[0016] The thickness value at the 90% chord position is a thickness value between 85% and 90% of the maximum thickness value.

[0017] Wherein, the maximum thickness value is within the upstream 50% of the chord.

[0018] In another aspect, a centrifugal compressor for a turbine engine is provided, the centrifugal compressor comprising: a diffuser configured to be disposed downstream of an inlet casing of the turbine engine; and an impeller located upstream of the diffuser, the impeller comprising a hub and blades extending from the hub, the blades having a leading edge, a trailing edge, and a chord defined between the leading edge and the trailing edge, a pressure side of the blade and a suction side of the blade opposite to the pressure side, and a blade thickness defined laterally between the pressure side and the suction side, the blade thickness decreasing over at least 40% downstream of the chord, the blade thickness having a trailing edge thickness value at the trailing edge between 40% and 80% of a maximum thickness value of the blade thickness.

[0019] On the other hand, a turbine engine for an aircraft is provided, the turbine engine comprising: an inlet; and a centrifugal compressor arranged downstream of the inlet, the centrifugal compressor comprising an impeller and a diffuser located downstream of the impeller, the impeller comprising a hub and blades extending from the hub, the blades having a leading edge, a trailing edge and a chord defined between the leading edge and the trailing edge, a pressure side of the blade and a suction side of the blade opposite to the pressure side, and a blade thickness defined laterally between the pressure side and the suction side, the blade thickness decreasing over at least 40% downstream of the chord, the blade thickness having a trailing edge thickness value at the trailing edge between 40% and 80% of the maximum thickness value of the blade thickness. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Reference is now made to the accompanying drawings, in which:

[0021] Figure 1 is a schematic cross-sectional view of a gas turbine engine;

[0022] Figure 2 is a pipe with an impeller and a downstream diffuser. Figure 1 The area II in Figure 1 An enlarged cross-sectional view of a portion of a centrifugal compressor of a gas turbine engine;

[0023] Figure 3 It is observed along the direction Z of the longitudinal center axis of the gas turbine engine. Figure 2 A partial transverse cross-sectional view of a portion of a centrifugal compressor;

[0024] Figure 4 yes Figure 3 a perspective schematic diagram of a portion of an impeller of; and

[0025] Figure 5 It is a graph illustrating the variation of blade thickness in the chord direction of the impeller. DETAILED DESCRIPTION

[0026] Figure 1A gas turbine engine 10 of a type preferably configured for use in transonic flight is illustrated and generally includes the following components in series flow communication, namely: a fan 12 through which ambient air is propelled; a compressor section 14 for pressurizing the air; a combustor 16 in which the compressed air is mixed with fuel and ignited to produce an annular flow of hot combustion gases; and a turbine section 18 for extracting energy from the combustion gases. Although the engine 10 is a turbofan gas turbine engine 10, it should be understood that the present technology is also applicable to other types of gas turbine engines. Of particular interest for the present application, the compressor section 14 includes at least one centrifugal compressor assembly 20, which generally includes an impeller 22 and a diffuser 40 downstream of the impeller 22.

[0027] refer to Figure 2 , a centrifugal compressor assembly 20 includes an impeller 22 fixed to a central shaft 24 and rotatable with the shaft 24 about a central axis 26 within a stationary impeller shroud 28 of the compressor assembly 20. The impeller 22 includes a central hub 30 defining a bore 31 therethrough, the bore 31 being co-linear with the axis 26. The impeller 22 also includes a plurality of blades 32 disposed about the hub 30 and the bore 31 and extending radially outwardly thereof to define a radial periphery of the impeller 22. The blades 32 and the surrounding shroud 28 are shaped to redirect an incoming axially flowing fluid stream 34 radially outwardly by approximately ninety degrees, thereby urging the fluid stream 34 radially outwardly relative to the hub 30 and increasing the velocity of the fluid stream 34. Although not required, in some embodiments, the hub 30 and the plurality of blades 32 are formed as a single piece. Thus, an annular fluid path is defined through the compressor assembly 20 between the inner surface 36 of the wheel shroud 28 and the outer surface 38 of the hub 30 , along and through the blades 32 .

[0028] Still reference Figure 2 , the diffuser 40 includes a diffuser housing 42 that defines a circumferential inlet space 44 around the periphery of an outlet space 46 of the compressor assembly 20. As shown in Figure 3 As best seen in FIG. 1 , the diffuser 40 includes a series of angled passages 48 defined from an inlet space 44 through the diffuser housing 42, each passage 48 being defined between adjacent diffuser vanes or vane islands 50 ( Figure 3 ). The diffuser 40 may be a vane-type diffuser, or may include multiple diffuser tubes. Alternative diffuser geometries are also possible, including, for example, diffusers with vaneless inlet spaces. Although not required, in a particular embodiment, the diffuser housing 42 is a single machined component.

[0029] Now go to Figure 3, the blade 32 will now be described in more detail with respect to the blade 32a of the blade 32 of the impeller. It should be understood that the present description of the blade 32a is consistent with the remaining blades of the blade 32 of the impeller 22, mutatis mutandis. The blade 32a has a pressure side 52 and a suction side 54 that are opposite to each other. The pressure side 52 and the suction side 54 extend from the outer surface 38 of the hub 30 to define a root of the blade 32a, which is formed at the junction between the outer surface 38 of the hub 30 and the pressure surface 52 and the suction surface 54 of the blade 32a. The blade 32a extends from its root to an outer free end of the blade 32a, which is spaced from the outer surface 38 to define the height of the blade at a given chord position. The blade 32a also has a leading edge 56 and a trailing edge 58. The leading edge 56 and the trailing edge 58 extend from the root of the blade 32a to the free end at the junction between the pressure surface 52 and the suction surface 54. The leading edge 56 forms the upstream end of the blade 32a. Figure 3 As best seen in FIG. 5 , in some embodiments, the pressure side 52 and the suction side 54 converge to define a leading edge 56. A trailing edge 58 forms the downstream end of the blade.

[0030] The true chord 60 of the blade 32a is defined as the chord line extending along the pressure side 52 and / or suction side 54 of the blade airfoil between the leading edge 56 and the trailing edge 58 and is measured at the hub 30 (i.e., at the junction between the pressure side or suction side of the blade and the outer surface 38 of the hub 30). Figure 3 , the chord 60 is shown as extending intermediate the pressure side 52 and the suction side 54 at the root of the blade 32a. In other embodiments, the chord 60 may additionally follow the blade 32a alongside either the pressure side 52 of the blade 32a or the suction side 54 of the blade 32a at either the root and the free end. A blade thickness is defined between the pressure side 52 and the suction side 54. The blade thickness may be measured transversely to the chord 60 at the root of the blade 32a between the pressure side 52 and the suction side 54. In other embodiments, the blade thickness may alternatively be measured at the outer free end of the blade 32a. The blade thickness includes: a trailing edge thickness value measured at the trailing edge 58; and a maximum thickness value at a point on the blade upstream of the trailing edge. The maximum thickness value is greater than the trailing edge thickness value. According to Figure 3 It will be appreciated that the portion of the blade 32a having this maximum thickness value is substantially upstream of the trailing edge 58 and, in practice, this maximum thickness value may be provided in the upstream half of the blade. As will be seen, the blade 32a of the impeller 20 has a blade thickness that decreases non-negligibly over the downstream portion of the blade 32a.

[0031] As in Figure 4As best seen in FIG. 6 , at the trailing edge 58, the pressure side 52 and the suction side 54 are separated by a distance 58a that corresponds to the value of the trailing edge thickness of the blade 32a at the hub 30. At the outer free end of the blade 32a away from the hub, the pressure side 52 and the suction side 54 are separated by a distance 58b that may be less than the trailing edge thickness value 58a at the hub, such as in one embodiment shown. In this one embodiment, the second blade thickness of the blade 32a measured at the free end is substantially constant over the downstream portion of the chord 60. In other embodiments, the second blade thickness may vary over the downstream portion of the chord 60.

[0032] Now go to Figure 5 , which provides a graph to describe the blade thickness of blade 32a in more detail with the specific example of blade 32b consistent with various embodiments of the present technology. The graph depicts the blade thickness as a function of the chord-wise position of blade 32b. At a number of estimated true chord positions 62 (i.e., positions on the blade expressed as a percentage of the chord 60) of each blade 32b, estimates of normalized thickness values ​​64 (i.e., measured thickness values ​​expressed as a percentage of a maximum thickness value) are plotted. Thus, Figure 5 Each of the curves 70, 72, 74 depicted in the graph of represents a blade 32b according to a different embodiment of the present technology. However, it is to be understood that each of these curves is exemplary in nature and other blade thickness distributions may be used without departing from the scope of the present disclosure. Figure 5 In the graph of , a 0% chord position 66 of the true chord position 62 corresponds to the leading edge 56 of the blade 32 b , and a 100% chord position 68 of the true chord position 62 corresponds to the trailing edge 58 of the blade 32 b .

[0033] In this graph, the blade thickness of blade 32b is depicted by curves 70, 72, and 74, respectively. In some embodiments, at the 0% chord position 66, the blade thickness has a blade thickness value that is the minimum thickness value 76 of blade 32a. In some such embodiments, at the 0% chord position 66, the blade thickness has a blade thickness value that corresponds to less than 10% (and in one particular embodiment, approximately 5%) of the maximum thickness value (shown at 78).

[0034] From this graph, it can be appreciated that the blade thickness decreases over at least the downstream 40% of the chord, ie, from the 60% chord position 80 downstream to the 100% chord position at the trailing edge 58 .

[0035] At the 60% chord position 80, the blade thickness has a thickness value between about 90% and 100% of the maximum thickness value 78, and more particularly between about 90% and about 97% of the maximum thickness value 78. For example, in the embodiments depicted by curves 70, 72, and 74, the blade has thickness values ​​of about 92%, 96%, and 96%, respectively, at the 60% chord position.

[0036] At the 70% chord position 82, the blade thickness has a thickness value between about 80% and about 95% of the maximum thickness value 78. For example, in the embodiments depicted by curves 70, 72, and 74, thickness values ​​of about 83%, 93%, and 93% are shown, respectively.

[0037] At the 90% chord position 84, the blade thickness has a thickness value between about 50% and 95%, and more particularly between about 55% and 90%, of the maximum thickness value 78. For example, curves 70, 72 and 74 show thickness values ​​of about 60%, 77% and 90%, respectively.

[0038] At the 100% chord position 68, i.e. at the trailing edge of the blade, the blade thickness has a thickness value between 40% and 80% of the maximum thickness value 78, and more specifically between 45% and 75% of the maximum thickness value 78. For example, curves 70, 72 and 74 show trailing edge thickness values ​​of approximately 50%, 66% and 73%, respectively.

[0039] In some embodiments, the maximum thickness value 78 may be located at a position upstream of the 50% chord position 86, or in other words, within the upstream half of the blade. For example, curves 70, 72, and 74 show that their respective maximum thickness values ​​78 are generally between the 15% chord position and the 40% chord position.

[0040] Based on the foregoing, it can be appreciated that the chord-wise reduction in thickness of the blades 32, 32a, 32b as disclosed herein can result in a longer life for the impeller 22 when compared to certain conventional impellers. The reduction in thickness of the blades 32, 32a, 32b over at least the downstream 40% of the chord 60 is arranged to provide the impeller 22 with a desired resistance to stresses at the bore 31 under certain operating conditions. For example, the reduction in thickness results in a mass distribution of the blades 32, 32a, 32b as they extend away from their roots, thereby producing a desired inertial load at the root. Upstream of the reduction, the bulge 88 of the blades 32, 32a, 32b, including the portion thereof having the maximum blade thickness value 78, produces a desired resistance to stress concentrations that conventional impellers are typically subjected to. It should also be appreciated that the blades 32, 32a, 32b are also arranged to provide the impeller 22 with certain desired aerodynamic properties. For example, in some embodiments, the reduced thickness of the blades 32, 32a, 32b over at least the downstream 40% of the chord 60 is arranged so that under certain operating conditions, the flow 34 is imparted with a desired maximum amount of disturbance as it moves downstream from the trailing edge 58. In some embodiments, the geometry of the blades 32, 32a, 32b over at least the downstream 40% of the chord 60 may be configured relative to the shape of the corresponding diffuser 40.

[0041] The above description is intended to be exemplary only, and those skilled in the art will recognize that the described embodiments may be changed without departing from the scope of the disclosed invention. For example, the impeller may be disposed in a centrifugal compressor of a turbine engine of other types than the turbine engine described herein. The fluid passing downstream of the impeller may be collected by other types of structures than the diffuser. Upon review of this disclosure, further modifications falling within the scope of the present invention will be apparent to those skilled in the art, and these modifications are intended to fall within the appended claims.

Claims

1. An impeller for a centrifugal compressor, the impeller comprising: a hub defining an axis of rotation about which the impeller is rotatable; as well as A blade extending from the hub, the blade having a leading edge, a trailing edge and a chord defined between the leading edge and the trailing edge, a pressure side of the blade and a suction side of the blade opposite the pressure side, a blade thickness defined laterally between the pressure side and the suction side, the blade thickness decreasing over at least 40% downstream of the chord, the blade thickness at the hub having a trailing edge thickness value at the trailing edge between 40% and 70% of a maximum thickness value of the blade thickness at the hub.

2. The impeller according to claim 1, wherein: A 0% chord position is defined at the leading edge and a 100% chord position is defined at the trailing edge, the trailing edge thickness value being the thickness value at the 100% chord position, the thickness value at the 100% chord position being between 45% and 75% of the maximum thickness value.

3. The impeller according to claim 2, wherein: The thickness value at the 100% chord position is a thickness value between 50% and 75% of the maximum thickness value.

4. The impeller according to claim 2, wherein: The thickness value at the 100% chord position is a thickness value between 45% and 55% of the maximum thickness value.

5. The impeller according to claim 2, wherein: The thickness value at the 100% chord position is a thickness value between 60% and 70% of the maximum thickness value.

6. The impeller according to claim 2, wherein: The thickness value at the 100% chord position is a thickness value between 60% and 75% of the maximum thickness value.

7. The impeller according to claim 2, wherein: The thickness value at the 100% chord position is a thickness value between 65% and 70% of the maximum thickness value.

8. The impeller according to claim 2, wherein: The thickness value at the 100% chord position is a thickness value between 70% and 75% of the maximum thickness value.

9. The impeller according to claim 2, wherein: The blade thickness has a thickness value at a 90% chord position between 50% and 90% of the maximum thickness value.

10. The impeller according to claim 9, wherein: The thickness value at the 90% chord position is a thickness value between 55% and 80% of the maximum thickness value.

11. The impeller according to claim 9, wherein: The thickness value at the 90% chord position is a thickness value between 55% and 65% of the maximum thickness value.

12. The impeller of claim 9, wherein: The thickness value at the 90% chord position is a thickness value between 70% and 80% of the maximum thickness value.

13. The impeller of claim 9, wherein: The thickness value at the 90% chord position is a thickness value between 85% and 90% of the maximum thickness value.

14. The impeller according to any one of claims 1 to 13, wherein: The maximum thickness value is within the upstream 50% of the chord.

15. A centrifugal compressor for a turbine engine, the centrifugal compressor comprising: a diffuser configured to be disposed downstream of an inlet casing of the turbine engine; as well as An impeller as defined in any one of claims 1 to 13.

16. A turbine engine for an aircraft, the turbine engine comprising: Entrance; as well as A centrifugal compressor as defined in claim 15, said centrifugal compressor being disposed downstream of said inlet.

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