JP2015117664A - Centrifugal compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a centrifugal compressor which preferably inhibits reverse flow of a fluid through a gap between an impeller outer surface and a housing inner wall surface.SOLUTION: A compressor impeller 20 is disposed in a housing of a compressor. The compressor impeller 20 is a closed type impeller in which multiple blades 22 and a shroud 23 having a shape covering the rotation direction outer periphery side of the blades 22 are joined to each other. Protruding parts 24, each of which extends along a joint portion between the shroud 23 and the blade 22, are provided on an outer peripheral surface of the shroud 23.

Description

  The present invention relates to a centrifugal compressor provided with a closed type impeller.

  Conventionally, a centrifugal compressor in which an impeller for pumping a fluid such as air is provided inside a housing is known. In the centrifugal compressor described in Patent Document 1, a closed type in which a side plate (a shroud) having a shape covering the periphery of a plurality of blades is joined to the outer peripheral ends of the blades is employed as the impeller. Further, in the centrifugal compressor described in Patent Document 1, it has been proposed to provide a seal portion extending over the entire circumference of the outer surface of the impeller in the rotational direction of the shroud. In such a centrifugal compressor, the seal portion suppresses the back flow of the fluid from the impeller downstream side to the upstream side through the gap between the outer peripheral surface of the impeller shroud and the inner peripheral wall of the housing, thereby improving the operation efficiency of the centrifugal compressor. Enhanced.

JP-A-5-321890

  Here, since the centrifugal compressor described in Patent Document 1 is of a non-contact type, a gap is formed between the outer peripheral surface of the impeller shroud and the inner wall surface of the housing. Therefore, although the backflow of the fluid from the impeller downstream side to the upstream side via the gap is suppressed by the seal portion, the suppression effect has a limit, and this prevents the improvement of the operation efficiency of the centrifugal compressor. Cause.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a centrifugal compressor that can suitably suppress the backflow of fluid through the gap between the outer surface of the impeller and the inner wall surface of the housing. .

  In the centrifugal compressor for achieving the above object, a closed type impeller formed by joining a plurality of blades and a side plate having a shape covering the outer peripheral side in the rotation direction of the blades is disposed inside the housing. And this centrifugal compressor has the protrusion part of the shape extended along the junction part of the same side plate and the said several blade | wing on the outer peripheral surface of the said side plate.

  In the above configuration, on the inner side in the rotational direction than the side plate (shroud) of the impeller inside the housing, a force for pumping fluid from the upstream side of the impeller toward the downstream side is generated by the rotation of the blades together with the impeller. In addition, on the outer side in the rotational direction than the shroud inside the housing, the protruding portion having a shape extending along the joint portion with the plurality of blades rotates together with the impeller, and accordingly, from the upstream side of the impeller toward the downstream side along with the rotation. A force for pumping the fluid is generated. Therefore, according to the above configuration, although the fluid tries to flow backward from the impeller downstream side to the upstream side through the gap between the outer surface of the shroud and the inner wall surface of the housing during the rotation of the impeller, the flow is caused by the rotation of the protrusion. Since the generated impeller can be canceled by the force of pumping the fluid from the upstream side to the downstream side, the back flow of the fluid can be suitably suppressed.

The fragmentary sectional view of the turbocharger to which the centrifugal compressor of the first embodiment is applied. The top view of the compressor impeller seen from the arrow 2 direction of FIG. The perspective view of the compressor impeller of the state which abbreviate | omitted the shroud. The perspective view of the compressor impeller of the state in which the shroud was joined. (A)-(e) Sectional drawing which shows notionally the state of the compressor impeller in each process. The perspective view of the compressor impeller of the centrifugal compressor of 2nd Embodiment. The top view of the compressor impeller. The side view of the compressor impeller. The side view of the compressor impeller of the centrifugal compressor of 3rd Embodiment.

(First embodiment)
Hereinafter, a first embodiment of the centrifugal compressor will be described.
As shown in FIG. 1, a compressor 10 as a centrifugal compressor includes a housing 11. A duct portion 12 extending in a circular cross section is formed inside the housing 11. The duct portion 12 is a passage through which air as a fluid flows, and a compressor impeller 20 is disposed inside the duct portion 12. The compressor impeller 20 is a closed type in which a plurality of blades 22 projecting from a base portion 21 extending in a circular cross section and a side plate (a shroud 23) having a shape covering the outer peripheral side in the rotation direction of the blades 22 are joined. The thing is adopted.

  Further, a scroll passage 13 extending in a spiral shape is formed in the housing 11 of the compressor 10 around the entire circumference in the rotation direction of the compressor impeller 20. The scroll passage 13 and the duct portion 12 communicate with each other over the entire circumference of the compressor impeller 20 via the diffuser 14.

  The compressor 10 constitutes a part of an exhaust-driven turbocharger that performs supercharging using the energy of the exhaust gas of the internal combustion engine. Specifically, a turbine wheel is disposed inside the turbine of the turbocharger, and the turbine wheel is coupled to the compressor impeller 20 via the shaft 15 so as to be integrally rotatable.

In such a turbocharger, the internal combustion engine is supercharged as follows.
When the turbine wheel is rotated by the energy of the exhaust gas discharged from the internal combustion engine, the compressor impeller 20 is also rotated. At this time, inside the compressor 10, as shown by a black arrow in the drawing, the air flowing into the duct portion 12 is sent to the diffuser 14 by the action of centrifugal force due to the rotation of the compressor impeller 20. The air is converted into a high-pressure / low-speed flow in the diffuser 14 and then sent to the internal combustion engine through the scroll passage 13. In an internal combustion engine with a turbocharger, the output performance can be improved by supercharging using the energy of such exhaust.

  Here, the compressor 10 has a gap between the outer peripheral surface of the shroud 23 of the compressor impeller 20 and the inner wall surface of the duct portion 12 of the housing 11. Therefore, when the pressure in the portion downstream of the compressor impeller 20 inside the housing 11 becomes higher than the pressure in the upstream portion due to supercharging by the compressor 10, the pressure difference causes the whiteness in the drawing. As indicated by the arrows, there is a possibility that a backflow of air from the downstream side to the upstream side of the compressor impeller 20 through the gap occurs.

In the present embodiment, a protrusion is provided on the outer peripheral surface of the shroud 23 of the compressor impeller 20 in order to suppress such a backflow of air.
FIG. 2 shows a planar structure of the compressor impeller 20 viewed from the direction of arrow 2 in FIG. 3 shows a perspective structure of the compressor impeller 20 with the shroud 23 omitted, and FIG. 4 shows a perspective structure of the compressor impeller 20 in which the shroud 23 is integrally provided.

  As shown in any of FIGS. 2 to 4, the outer surface of the shroud 23 is provided with a protruding portion 24 having a shape protruding toward the outer peripheral side in the rotational direction. The protruding portion 24 is extended in a shape in which a ridge line (indicated by a one-dot chain line in the drawing) of the protruding portion 24 extends along a joint portion between the plurality of blades 22 and the shroud 23. Specifically, the projecting portion 24 extends on the outer peripheral surface of the shroud 23 at a portion where the inner peripheral side in the rotational direction of the shroud 23 becomes the joint portion.

Such a compressor impeller 20 is formed through “first step” to “fifth step” described below.
FIGS. 5A to 5E show the state of the compressor impeller 20 in each step.

  As shown in FIG. 5A, in the first step, the compressor in a state in which the shroud 23 (see FIG. 1) is not provided, that is, a state in which the base portion 21 and the plurality of blades 22 are integrally formed through the cutting process. Impeller 20A is formed.

  As shown in FIG. 5 (b), in the subsequent second step, the core resin material R is filled in the portion sandwiched between the plurality of blades 22 in the compressor impeller 20A, and the same portion is filled.

  As shown in FIG.5 (c), in the subsequent 3rd process, the part (part shown by arrow B in a figure) which is going to form the shroud 23 in the surface of the core resin material R is removed by cutting.

  As shown in FIG.5 (d), in the 4th process after that, the shroud 23 is formed in the surface of the core resin material R by injection molding process. At this time, the shroud 23 is bonded and fixed to the end of each blade 22 on the outer peripheral side in the rotational direction.

As shown in FIG. 5 (e), in the subsequent fifth step, the core resin material R is heated and melted and removed from between the base portion 21 and the shroud 23.
In the present embodiment, when the shroud 23 contracts as the temperature decreases after the injection molding in the fourth step, only the portion of the shroud 23 joined to the tip of each blade 22 prevents the contraction inward in the rotational direction. As a result, the protrusion 24 having a shape protruding outward in the rotational direction is formed on the surface of the shroud 23. Specifically, the core resin material R and the material for forming the shroud 23 are set so that such a configuration is realized, and the temperatures in the fourth step and the fifth step are controlled. By forming the shroud 23 in this manner, a shape extending along the joint portion between the blade 22 and the shroud 23 without performing a complicated operation such as forming the surface of the shroud 23 into a complicated shape by cutting. The protrusion 24 can be easily formed.

Through these first to fifth steps, the compressor impeller 20 having the shroud 23 and the protrusion 24 is formed.
Hereinafter, the effect | action by providing the protrusion part 24 in the surface of the shroud 23 in this way is demonstrated.

  As shown in FIG. 1, in the duct portion 12 of the housing 11, a portion on the inner side in the rotational direction than the shroud 23, that is, a portion sandwiched between the base portion 21 and the shroud 23, together with the compressor impeller 20, a plurality of blades 22. As a result of the rotation, a force for pumping air from the upstream side to the downstream side of the compressor impeller 20 is generated.

  In addition, the outer periphery of the shroud 23 together with the compressor impeller 20 is formed in a portion outside the shroud 23 inside the duct portion 12 of the housing 11 in the rotational direction, that is, a portion sandwiched between the outer peripheral surface of the shroud 23 and the inner wall surface of the duct portion 12. The protrusion 24 formed on the surface rotates. Since the protrusion 24 extends along the joints with the plurality of blades 22, the outer periphery of the shroud 23 is similar to the force generated with the rotation of each blade 22 as the protrusion 24 rotates. Even in the gap between the surface and the inner wall surface of the duct portion 12, a force for pumping air from the upstream side to the downstream side of the compressor impeller 20 is generated.

  Therefore, in the compressor 10, although air tries to flow backward from the downstream side of the compressor impeller 20 through the gap between the outer peripheral surface of the shroud 23 and the inner wall surface of the duct portion 12, The compressor impeller 20 generated along with this can be counteracted by the force of pumping air from the upstream side toward the downstream side. Therefore, it is possible to suitably suppress the backflow of air through the gap between the outer peripheral surface of the shroud 23 and the inner wall surface of the housing 11.

As described above, according to the present embodiment, the following effects can be obtained.
(1) The protrusion 24 having a shape extending along the joint portion between the shroud 23 and the plurality of blades 22 is provided on the outer peripheral surface of the shroud 23. Therefore, it is possible to suitably suppress the backflow of air through the gap between the outer peripheral surface of the shroud 23 and the inner wall surface of the housing 11.

(Second Embodiment)
Hereinafter, the second embodiment of the centrifugal compressor will be described with a focus on differences from the first embodiment.

  The centrifugal compressor of the present embodiment is different from the centrifugal compressor of the first embodiment only in the outer surface shape of the shroud of the compressor impeller. Specifically, in the first embodiment, the protrusion 24 (see FIG. 2) is provided on the outer surface of the shroud, but in the present embodiment, such a protrusion is not formed, and a plurality of protrusions are formed on the outer surface of the shroud. Feathers are provided. In addition, below, since parts other than the plurality of blades formed on the outer surface of the shroud have the same configuration as the first embodiment, the same parts are denoted by the same reference numerals and detailed descriptions thereof are given. Omit.

  Hereinafter, the plurality of blades 34 formed on the outer peripheral surface of the shroud 23 of the compressor impeller 30 will be described in detail with reference to FIGS. 6 to 8. 6 shows a perspective structure of the compressor impeller 30, FIG. 7 shows a planar structure of the compressor impeller 30, and FIG. 8 shows a side structure of the compressor impeller 30.

  As shown in any of FIGS. 6 to 8, on the outer peripheral surface of the compressor impeller 30, a plurality of blades 34 projecting in a thin plate shape toward the outer peripheral side in the rotation direction of the compressor impeller 30 are formed. These blades 34 are capable of generating a force for pumping air from the upstream side to the downstream side of the compressor impeller 30 as the compressor impeller 30 rotates in the duct portion 12 (see FIG. 1). It extends on the outer peripheral surface of the shroud 23.

  In the compressor impeller 30, the extending angle of the plurality of blades 34 on the outer surface of the shroud 23 with respect to the plane orthogonal to the rotation axis L (the angle indicated by “α” in the drawing) is the inside of the shroud 23 with respect to the plane orthogonal to the rotation axis L. This is smaller than the extending angle of the plurality of blades 22 (the angle indicated by “β” in the figure).

  In the compressor of the present embodiment, the inner diameter of the duct portion 12 in the portion where the compressor impeller 30 is disposed, the outer diameter of the base portion 21 of the compressor impeller 30, and the outer diameter of the outer peripheral surface of the shroud 23 are all closer to the downstream side. It is larger (see FIG. 1). The plurality of blades 34 are not formed in the downstream portion of the outer peripheral surface of the shroud 23, and are extended in the upstream portion of the outer peripheral surface of the shroud 23. The blades 34 are made of carbon fiber reinforced plastic (CFRP) and are bonded and fixed to the outer peripheral surface of the shroud 23.

Hereinafter, the operation and effect of providing the blades 34 on the outer peripheral surface of the shroud 23 will be described.
In the compressor of the present embodiment, blades 34 having an appropriate shape are provided on the outer surface of the shroud 23 in order to pump air. Therefore, it is a force that pumps air from the upstream side of the compressor impeller 30 toward the downstream side in the gap between the outer peripheral surface of the shroud 23 and the inner wall surface of the duct portion 12, and the outer wall surface of the shroud 23 and the inner wall surface of the duct portion 12. Thus, it is possible to appropriately generate a force for suppressing the backflow of air through the gap.

  Moreover, in the compressor of this embodiment, since the several blade | wing 34 is formed in the shroud 23 outer peripheral surface, the centrifugal force which acts on the compressor impeller 30 at the time of rotation will increase by that much. In this regard, in the compressor of the present embodiment, the plurality of blades 34 are provided only in the upstream portion of the outer peripheral surface of the shroud 23, that is, only in the portion having a small outer diameter. Therefore, the centrifugal force acting on the compressor impeller 20 can be reduced as compared with the case where the blades are formed in the downstream portion (the portion having a large outer diameter) of the outer peripheral surface of the shroud 23, and the compressor impeller 30 is balanced. It can be made a good structure.

(Third embodiment)
Hereinafter, the third embodiment of the centrifugal compressor will be described focusing on differences from the first embodiment and the second embodiment.

  The centrifugal compressors of the first and second embodiments and the centrifugal compressor of the present embodiment differ only in the outer shape of the shroud of the compressor impeller. Specifically, in the first embodiment, the protrusion 24 (see FIG. 2) is provided on the outer peripheral surface of the shroud 23, and in the second embodiment, a plurality of blades 34 (see FIG. 6) are provided on the outer peripheral surface of the shroud 23. In contrast, in the present embodiment, such protrusions and blades are not formed, and a convex portion extending in a spiral shape is provided on the outer peripheral surface of the shroud 23. In addition, below, since parts other than the convex part formed in the outer peripheral surface of the shroud 23 have the same configuration as the first embodiment and the second embodiment, the same parts are denoted by the same reference numerals and shown. The detailed explanation is omitted.

  Hereinafter, the convex portion 44 formed on the outer peripheral surface of the shroud 23 of the compressor impeller 40 will be described in detail with reference to FIG. 9. FIG. 9 shows a side structure of the compressor impeller 40.

As shown in FIG. 9, a convex portion 44 is formed on the outer peripheral surface of the shroud 23 of the compressor impeller 40 so as to protrude toward the outer peripheral side in the rotational direction of the compressor impeller 40.
Specifically, the convex portion 44 is formed in a spiral shape (specifically, a screw shape) extending around the entire circumference of the outer peripheral surface of the shroud 23. The winding direction of the convex portion 44 formed in a spiral shape is a force that pumps air from the upstream side to the downstream side of the compressor impeller 20 as the compressor impeller 40 rotates in the duct portion 12 (see FIG. 1). It is set in the direction to generate. Specifically, the inclination of the ridge line of the convex portion 44 with respect to the rotation axis L of the compressor impeller 40 is the same as the inclination of the extending direction of the plurality of blades 22 with respect to the rotation axis L (the upward direction in FIG. 9). )It has become.

  In the present embodiment, the shroud 23 and the convex portion 44 are formed by injection molding using a mold in a step according to the above-described fourth step (see FIG. 5D). When the compressor impeller 40 is formed through such a process, the compressor impeller 40 can be removed from the mold by rotating the compressor impeller 40 after the shroud 23 is formed by injection molding.

Hereinafter, the effect by providing the convex part 44 in the outer peripheral surface of the shroud 23 in this way is demonstrated.
In the compressor of this embodiment, when the compressor impeller 40 is rotated, the screw-shaped convex portion 44 is rotated between the outer peripheral surface of the shroud 23 and the inner wall surface of the duct portion 12, so that the convex portion 44 is formed. The part functions like a screw-type pump. Therefore, a force that pumps air from the upstream side to the downstream side of the compressor impeller 40 is generated in the gap between the outer peripheral surface of the shroud 23 and the inner wall surface of the duct portion 12. Therefore, in the compressor of the present embodiment, although the air tends to flow backward from the downstream side of the compressor impeller 20 through the gap between the outer peripheral surface of the shroud 23 and the inner wall surface of the duct portion 12, It can be canceled out by the force of pressure-feeding air from the upstream side to the downstream side of the compressor impeller 40 generated with the rotation of 44. Therefore, it is possible to suitably suppress the backflow of air through the gap between the outer peripheral surface of the shroud 23 and the inner wall surface of the housing 11.

Each of the above embodiments may be modified as follows.
In the first embodiment, the protrusion 24 may be formed by cutting the outer peripheral surface of the shroud 23 or may be disposed by fixing a separately formed member to the outer peripheral surface of the shroud 23.

  -In 1st Embodiment, if the protrusion part 24 is extended in the shape extended along the said junction part, it will be extended in the shape extended substantially parallel to the said junction part in the position slightly away from the junction part. Etc. Even with such a configuration, the same effects as those of the first embodiment can be obtained.

-In 2nd Embodiment, the material which forms the blade | wing 34 is not restricted to a carbon fiber reinforced plastic (CFRP), It can change arbitrarily.
-In 2nd Embodiment, it is not restricted to arrange | positioning the blade | wing 34 by fixing the blade | wing 34 formed separately on the outer surface of the shroud 23, but the outer surface of the shroud 23 by cutting the outer surface of the shroud 23 Alternatively, the blades 34 may be formed.

-In 3rd Embodiment, the convex part 44 can also be formed through machining processes, such as a rolling process and a cutting process, besides forming by molding processes, such as injection molding.
The centrifugal compressor of each of the above embodiments is not limited to an exhaust drive type turbocharger compressor, and can be applied to any centrifugal compressor having a structure in which a closed type impeller is disposed inside a housing.

  -The centrifugal compressor of each said embodiment is applicable also to the centrifugal compressor which pumps other fluids other than air.

  DESCRIPTION OF SYMBOLS 10 ... Compressor, 11 ... Housing, 12 ... Duct part, 13 ... Scroll passage, 14 ... Diffuser, 15 ... Shaft, 20, 30, 40 ... Compressor impeller, 21 ... Base part, 22 ... Blade, 23 ... Shroud, 24 ... Projection, 34 ... blade, 44 ... convex.

Claims (1)

In a centrifugal compressor in which a closed type impeller formed by joining a plurality of blades and a side plate covering the outer peripheral side in the rotation direction of the blades is disposed inside the housing,
A centrifugal compressor characterized by having a protruding portion extending along a joint portion between the side plate and the plurality of blades on the outer peripheral surface of the side plate.