JP2019015229A - Centrifugal compressor impeller and centrifugal compressor - Google Patents

Abstract

To reduce a reverse flow region of a centrifugal compressor, to improve efficiency in operation at a small flow rate.SOLUTION: An impeller 7 of a compressor 3 is configured such that out of a front edge 25 of a long blade 23 in a projection image projected on a meridian plane, a portion on a radial inward side with respect to a predetermined reference position P is defined as a front edge first part 31, and a portion on a radial outward side with respect to the reference position P is defined as a front edge second part 32, wherein the front edge second part 32 extends along a straight line orthogonal to a rotational axis line A, and all portions of the front edge first part 31 are positioned on an upstream side with respect to the front edge second part 32.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a centrifugal compressor impeller and a centrifugal compressor.

  Conventionally, as a technique in such a field, a centrifugal compressor impeller described in Patent Document 1 below is known. In the shape in which the main blades of the impeller are projected onto the meridian plane, the leading edge of the main blade extends in a direction (rotational radial direction) substantially orthogonal to the rotation axis.

JP 2008-196381

  According to the shape of the main blade as described above, the backflow region in which the gas flows back in the direction from the tip of the main blade toward the hub tends to widen, particularly when operating at a small flow rate. Such a backflow region can cause a reduction in the efficiency of the centrifugal compressor. In view of this problem, an object of the present invention is to reduce the backflow region of a centrifugal compressor and improve the efficiency at the time of small flow rate operation.

  A centrifugal compressor impeller according to the present invention is a centrifugal compressor impeller including a hub and blades provided on the hub, and is a predetermined reference among the leading edges of the blades in a projection image projected on the meridian plane. When the portion on the inner side in the rotation radial direction from the position is the front edge first portion and the portion on the outer side in the rotation radial direction from the reference position is the second front edge portion, the second front edge portion is a straight line orthogonal to the rotation axis. All the parts of the first part of the leading edge are located upstream of the second part of the leading edge.

  The first part of the leading edge may be positioned more upstream as it goes inward in the rotational radial direction. The distance in the radial direction from the end of the front edge on the hub side to the reference position is 0.2 mm, the distance in the radial direction from the end on the hub side of the front edge to the end on the tip side of the front edge. It may be made to be 0.8 times. The centrifugal compressor of the present invention includes any one of the above centrifugal compressor impellers.

  ADVANTAGE OF THE INVENTION According to this invention, the backflow area | region of a centrifugal compressor can be reduced and the efficiency at the time of a small flow rate operation can be improved.

FIG. 1 is a cross-sectional view including a rotation axis of the supercharger. FIG. 2 is a side view showing an impeller of the compressor of the supercharger shown in FIG. FIG. 3 is a diagram showing a projection image obtained by projecting the impeller onto the meridian plane. FIG. 4 is a conceptual diagram showing a static pressure distribution in the span direction (radial direction) in the vicinity of the leading edge of the impeller. FIG. 5 is a conceptual diagram showing the impeller and the backflow region of the suction port upstream of the impeller. FIGS. 6A and 6B are diagrams showing modified examples of the impeller, respectively.

  Hereinafter, embodiments of a centrifugal compressor impeller and a centrifugal compressor according to the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a cross-sectional view of a section including a rotation axis A of the supercharger 1. The supercharger 1 includes a compressor 3 as a centrifugal compressor according to the present embodiment. The compressor 3 includes a compressor impeller 7 as a centrifugal compressor impeller according to the present embodiment.

  The supercharger 1 is applied to an internal combustion engine of a ship or a vehicle, for example. As shown in FIG. 1, the supercharger 1 includes a turbine 2 and a compressor 3. The turbine 2 includes a turbine housing 4 and a turbine impeller 6 housed in the turbine housing 4. The turbine housing 4 has a scroll channel 16 extending in the circumferential direction around the turbine impeller 6. The compressor 3 includes a compressor housing 5 and a compressor impeller 7 housed in the compressor housing 5. The compressor housing 5 has a scroll passage 17 extending in the circumferential direction around the compressor impeller 7.

  The turbine impeller 6 is provided at one end of the rotating shaft 14, and the compressor impeller 7 is provided at the other end of the rotating shaft 14. A bearing housing 13 is provided between the turbine housing 4 and the compressor housing 5. The rotating shaft 14 is rotatably supported by the bearing housing 13 via a bearing 15, and the rotating shaft 14, the turbine impeller 6 and the compressor impeller 7 rotate around the rotation axis A as an integral rotating body 12.

  The turbine housing 4 is provided with an exhaust gas inlet 8 and an exhaust gas outlet 10. Exhaust gas discharged from an internal combustion engine (not shown) flows into the turbine housing 4 through the exhaust gas inlet 8 and flows into the turbine impeller 6 through the scroll flow path 16 to rotate the turbine impeller 6. Thereafter, the exhaust gas flows out of the turbine housing 4 through the exhaust gas outlet 10.

  The compressor housing 5 is provided with a suction port 9 and a discharge port 11. When the turbine impeller 6 rotates as described above, the compressor impeller 7 rotates via the rotating shaft 14. The rotating compressor wheel 7 sucks outside air through the suction port 9. This air passes through the compressor impeller 7 and the scroll flow path 17 and is compressed and discharged from the discharge port 11. The compressed air discharged from the discharge port 11 is supplied to the internal combustion engine described above.

  Next, the compressor impeller 7 (hereinafter referred to as “impeller 7”) will be further described. Hereinafter, the terms “upstream” and “downstream” correspond to the upstream and downstream of the gas in the impeller 7. Further, when simply referring to “radial direction”, “circumferential direction”, and “axial direction”, it means the rotational radial direction, rotational circumferential direction, and rotational axis direction of the impeller 7, respectively.

  As shown in FIG. 2, the impeller 7 includes a hub 21 and a plurality of long blades (blades) 23 provided on the hub 21. The plurality of long blades 23 are arranged at equal intervals in the circumferential direction on the surface of the hub 21. The impeller 7 may further include short blades provided between the long blades 23. FIG. 3 shows the meridian shape of the long blade 23. The meridional shape of the long blade 23 refers to the shape of a projection image obtained by projecting the long blade 23 onto the meridian surface of the impeller 7 in the rotation direction. Further, the meridian plane of the impeller 7 refers to a plane including the rotation axis A. In the following description, the fillet formed at the base of the long blade 23 is not included in the meridional shape of the long blade 23. Further, the detailed shape of the long blade 23 shown in FIGS. 2 and 3 is not shown in FIG.

  Hereinafter, the meridian shape of the long blade 23 will be described. As shown in FIG. 3, the leading edge 25 (leading edge) of the long blade 23 projected on the meridian plane is divided into two parts in the radial direction. Of the front edge 25, a portion radially inward of the predetermined reference position P is referred to as a front edge first portion 31, and a portion radially outward from the reference position P is referred to as a front edge second portion 32. The leading edge first portion 31 and the leading edge second portion 32 have different shapes. The radial distance L1 from the hub side end portion of the front edge 25 (hereinafter referred to as “hub side end portion 25h”) to the reference position P is the tip side end portion (hereinafter referred to as “tip side”) of the front edge 25 from the hub side end portion 25h. It is 0.2 to 0.8 times the radial distance L3 to “chip side end portion 25c”.

  The front edge second portion 32 extends along a straight line orthogonal to the rotation axis A. Specifically, the front edge second portion 32 extends from the reference position P to the chip side end portion 25c so as to form a straight line substantially orthogonal to the rotation axis A. The state where the front edge second portion 32 extends along a straight line orthogonal to the rotation axis A is a state where the front edge second portion 32 is slightly inclined with respect to the straight line orthogonal to the rotation axis A. Alternatively, the front edge second portion 32 may be in a state of forming a curve positioned close to a straight line orthogonal to the rotation axis A.

  All parts of the leading edge first portion 31 are located upstream of the leading edge second portion 32. That is, in the case of FIG. 3, all the parts of the front edge first part 31 are located on the left side of the front edge second part 32. With this configuration, a portion of the long blade 23 that protrudes to the upstream side compared to the tip side (hereinafter referred to as “extended portion 35”) exists. The overhanging portion 35 is a portion indicated by hatching in FIG. Further, all of the front edge first portion 31 is located on the upstream side of a straight line passing through the chip side end portion 25c and the reference position P. That is, the overhanging portion 35 protrudes upstream of the extension line of the front edge second portion 32.

  The leading edge first portion 31 is located more upstream as it goes radially inward. That is, each point on the front edge first portion 31 is located on the upstream side as the position is closer to the hub side. The front edge first portion 31 is curved so as to swell toward the radially inner side and the downstream side. The front edge first portion 31 and the front edge second portion 32 are continuously connected without being bent at the reference position P. That is, the tangent at the reference position P of the front edge first portion 31 and the tangent at the reference position P of the front edge second portion 32 coincide with each other.

  The effect by the impeller 7 which has the above long blades 23 is demonstrated. As described above, the long blade 23 has a protruding portion 35 on the hub side that protrudes to the upstream side compared to the tip side. FIG. 4 is a conceptual diagram showing a static pressure distribution in the span direction (radial direction) in the vicinity of the leading edge of the impeller. A curve G1 in FIG. 4 shows the static pressure distribution of the impeller 7 of the present embodiment, and a curve G2 shows the static pressure distribution of a comparative impeller (not shown) that does not have the overhanging portion 35. In the comparative impeller, the leading edge projected on the meridian plane is assumed to form a straight line orthogonal to the rotation axis A. FIG. 5 is a conceptual diagram showing a reverse flow region of the impeller. In FIG. 5, the region above the curve g3 indicates the reverse flow region G3 generated by the impeller 7, and the region above the curve g4 indicates the reverse flow region G4 generated by the comparative impeller. The backflow region G3 is included in the backflow region G4. 4 and 5 both show the state of the impeller in the small flow rate region of the compressor 3.

  As shown in FIG. 4, according to the static pressure distribution (curve G2) of the comparative impeller, the static pressure difference between the tip side (high pressure) and the hub side (low pressure) of the comparative impeller is relatively large. Due to this static pressure difference, in the comparative impeller, the tendency of the backflow region where the gas flows back from the tip side toward the hub side becomes relatively large, and the backflow region G4 is formed as shown in FIG. Such a backflow region can cause a reduction in efficiency of the centrifugal compressor and a surge.

  On the other hand, in the impeller 7 having the overhanging portion 35, due to the presence of the overhanging portion 35, work from the long blade 23 is given to the gas on the hub side before the gas on the tip side. As a result, the static pressure on the hub side is increased, and the static pressure difference between the tip side and the hub side is alleviated, as shown by the curve G1 in FIG. Therefore, the tendency of the gas backflow region to spread from the tip side to the hub side is reduced, and the backflow region G3 is reduced as shown in FIG. And work is efficiently given to gas from impeller 7, and the efficiency of compressor 3 improves. The above effect is particularly remarkable in a small flow rate region. Further, by reducing the backflow region, it is difficult for a surge in a small flow rate region to occur, and the operational stability of the compressor 3 and the supercharger 1 is improved.

  In addition, since the front edge first portion 31 has a shape positioned more upstream as it goes radially inward, the front edge 25 forms a shallow angle with respect to the hub 21 surface at the hub-side end portion 25h. It will be connected to. Therefore, in the impeller 7, the stress generated at the root of the long blade 23 is reduced as compared with the comparative impeller.

  The present invention can be implemented in various forms including various modifications and improvements based on the knowledge of those skilled in the art including the above-described embodiments. In addition, the following modifications may be configured using the technical matters described in the above-described embodiments. You may use combining the structure of each embodiment suitably.

  The meridional shape of the long blade having the overhanging portion is not limited to the long blade 23 (FIG. 3). For example, the meridian shape of the long blade may be the shape shown in FIG. 6A or 6B described below.

  A front edge 45 of the long blade 43 shown in FIG. 6A is divided into a front edge first part 41 and a front edge second part 42 with the reference position P as a boundary. The front edge second portion 42 forms a straight line that extends in the direction substantially orthogonal to the rotation axis A through the chip side end portion 45c. All parts of the leading edge first portion 41 are located upstream of the leading edge second portion 42. The leading edge first portion 41 is located more upstream as it goes radially inward. A hub side end 45 h of the front edge 45 is located upstream of the reference position P. The front edge first portion 41 extends linearly from the reference position P to the hub side end portion 45h. An extended portion 47 is formed on the hub side of the long blade 43 so as to protrude upstream from the tip side.

  A front edge 55 of the long blade 53 shown in FIG. 6B is divided into a front edge first part 51 and a front edge second part 52 with the reference position P as a boundary. The front edge second portion 52 forms a straight line that passes through the chip side end portion 55c and extends in a direction substantially orthogonal to the rotation axis A. All parts of the leading edge first portion 51 are located upstream of the leading edge second portion 52. The hub side end portion 55 h of the front edge 55 is located upstream of the reference position P. The front edge first portion 51 includes a straight portion 51a that extends in a direction orthogonal to the rotation axis A through the hub side end portion 55h. And the overhang | projection part 57 projected over the upstream compared with the chip | tip side is formed in the hub side of the long blade 53. FIG.

1 Supercharger 3 Compressor (centrifugal compressor)
23 Long blade 25 Front edge 25c, 45c, 55c Tip side end 25h, 45h, 55h Hub side end 31, 41, 51 Front edge first part 32, 42, 52 Front edge second part P Reference position

Claims (4)

A centrifugal compressor impeller comprising a hub and blades provided on the hub,
Among the leading edges of the blades in the projected image projected on the meridian plane, a portion on the inner side in the rotational radial direction from the predetermined reference position is defined as a first front edge, and a portion on the outer side in the rotational radial direction from the reference position When the second part of the leading edge
The leading edge second part extends along a straight line orthogonal to the rotation axis,
The centrifugal compressor impeller, wherein all parts of the first part of the leading edge are located upstream of the second part of the leading edge. The first part of the leading edge is
The centrifugal compressor impeller according to claim 1, wherein the centrifugal compressor impeller is located further upstream as it goes inward in the rotational radial direction. The distance in the rotational radial direction from the end of the front edge on the hub side to the reference position is
3. The centrifugal compressor according to claim 1, wherein the centrifugal compressor is 0.2 to 0.8 times the distance in the rotational radial direction from the hub-side end of the front edge to the tip-side end of the front edge. Impeller.   A centrifugal compressor provided with the centrifugal compressor impeller according to any one of claims 1 to 3.

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