Scroll housing and centrifugal compressor

Abstract

A scroll housing includes a scroll portion that forms a scroll flow path of a centrifugal compressor. The scroll portion includes a first arc portion, a second arc portion, and a third arc portion. When the radius of curvature of the second arc portion is defined as R2 and the radius of curvature of the third arc portion is defined as R3, the scroll portion has a nearly circular scroll cross-section satisfying the relationship of R2 > R3. The first arc portion extends from the connection position (the first position) of the centrifugal compressor with the hub-side flow surface of the diffuser flow path to one direction side (the side facing the fourth position). The second arc portion is formed at a position closer to one direction side than the first arc portion and includes at least a part of the region between the outermost end in the radial direction (the second position) and the innermost end in the radial direction (the fourth position). The third arc portion is formed at a position closer to one direction side than the second arc portion and includes the end position (the fifth position) on one direction side of the scroll portion.

Description

Technical Field

[0001] The present disclosure relates to a scroll housing and a centrifugal compressor including the scroll housing. Background Art

[0002] A centrifugal compressor used in a compressor section of a turbocharger for a vehicle or a ship, etc. applies kinetic energy to a fluid by rotation of an impeller to eject the fluid radially outward, and uses centrifugal force to obtain a pressure rise of the fluid. For the centrifugal compressor, high pressure ratio and high efficiency are required in a wide operating range, and various efforts have been made.

[0003] Generally, a centrifugal compressor includes a scroll housing having a scroll portion forming a spiral scroll flow path, and a cross-sectional shape (scroll cross-section) of the scroll flow path is formed in a near-circular shape that extends over the entire circumference of the scroll flow path. As an existing centrifugal compressor, one having a scroll cross-section including a first arc portion having a first radius of curvature and a second arc portion having a second radius of curvature different from the first radius of curvature is known.

[0004] When the scroll cross-section is deformed, it may cause a pressure loss in the scroll flow path, so the scroll cross-section is made close to a true circle. As one method of making the scroll cross-section close to a true circle, it is conceivable to form most of the scroll cross-section by the first arc portion and form the remaining portion of the scroll cross-section by the second arc portion. The second arc portion connects one end of the first arc portion to the blade end side flow surface of the diffuser flow path. In this case, an extreme curvature change occurs between the first arc portion and the second arc portion, so it may cause a pressure loss in the scroll flow path.

[0005] Patent Document 1: Japanese Patent No. 6053993 Summary of the Invention

[0006] Technical Problem to be Solved by the Invention

[0007] Moreover, as one method of making the scroll cross-section close to a true circle, it is conceivable to make the difference between the first radius of curvature and the second radius of curvature a smaller value so that the entire scroll cross-section is in a nearly circular shape. In this case, the change in curvature between the first arc portion and the second arc portion can be made gentle, so compared with the above method, the generation of pressure loss in the scroll flow path can be suppressed, and the efficiency of the centrifugal compressor can be improved. In order to further improve the efficiency of the centrifugal compressor, it is required to more effectively suppress the generation of pressure loss in the scroll flow path than this method.

[0008] Note that Patent Document 1 discloses a scroll portion of a centrifugal compressor having a scroll cross-section, which includes a first arc portion having a first radius of curvature, a second arc portion having a second radius of curvature, and a third arc portion having a third radius of curvature. By making the second arc portion flatter than the first and third arc portions, the scroll portion of Patent Document 1 can more easily guide the fluid introduced into the scroll flow path to the inner peripheral side in the scroll flow path compared to the case where the cross-sectional shape of the scroll flow path is nearly circular. Thus, the scroll portion of Patent Document 1 intentionally makes the cross-sectional shape of the scroll flow path deviate from a circular shape. Therefore, the relevance between Patent Document 1 and the present disclosure is low.

[0009] In view of the above situation, an object of at least one embodiment of the present disclosure is to provide a scroll housing capable of suppressing the generation of pressure loss in a scroll flow path and a centrifugal compressor including the scroll housing.

[0010] Technical solutions for solving technical problems

[0011] The scroll housing of the present disclosure is a scroll housing of a centrifugal compressor, wherein

[0012] the scroll housing includes a scroll portion that forms the scroll flow path of the centrifugal compressor,

[0013] In the inner peripheral surface of the scroll portion, when the connection position with the hub side flow surface of the diffusion flow path of the centrifugal compressor is defined as the first position, the outermost end in the radial direction of the centrifugal compressor is defined as the second position, the foremost end in the axial direction of the centrifugal compressor is defined as the third position, the innermost end in the radial direction is defined as the fourth position, and the end position on one direction side along the inner peripheral surface of the scroll portion from the first position toward the fourth position is defined as the fifth position, the scroll portion at least includes a first arc portion, a second arc portion, and a third arc portion.

[0014] And, when the radius of curvature of the second arc portion is defined as R2 and the radius of curvature of the third arc portion is defined as R3, the scroll portion has a nearly circular scroll cross-section satisfying the relationship of R2 > R3.

[0015] The first arc portion extends from the first position toward the one direction side.

[0016] The second arc portion is formed at a position closer to the one direction side than the first arc portion and is formed to include at least a part of the region between the second position and the fourth position.

[0017] The third arc portion is formed at a position closer to the one direction side than the second arc portion and is formed to include at least the fifth position.

[0018] The centrifugal compressor of the present disclosure includes the scroll housing.

[0019] Effects of the Invention

[0020] According to at least one embodiment of the present disclosure, there is provided a scroll housing capable of suppressing the generation of pressure loss in a scroll flow path and a centrifugal compressor including the scroll housing. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is an explanatory view for explaining the structure of a turbocharger including a centrifugal compressor according to one embodiment.

[0022] Figure 2 It is a schematic cross-sectional view schematically showing the compressor side of a turbocharger including a centrifugal compressor according to one embodiment, and is a schematic cross-sectional view including the axis of the centrifugal compressor.

[0023] Figure 3 It is an explanatory view for explaining the shape of a scroll portion of a scroll housing according to one embodiment.

[0024] Figure 4 It is an explanatory view for explaining the shape of a scroll portion of a scroll housing according to one embodiment.

[0025] Figure 5 It is an explanatory view for explaining the shape of a scroll portion of a scroll housing of a comparative example.

[0026] Figure 6 It is for Figure 3 , Figure 4 comparing the shape of the scroll portion of one embodiment shown with Figure 5 the shape of the scroll portion of the comparative example shown in

[0027] Figure 7 It is an explanatory view for explaining the shape of a scroll portion of a scroll housing according to one embodiment.

[0028] Figure 8 It is an explanatory view for explaining the shape of a scroll portion of a scroll housing according to one embodiment.

[0029] Figure 9 It is a schematic view of a scroll flow path in an axial view of a centrifugal compressor according to one embodiment. DETAILED DESCRIPTION

[0030] Hereinafter, several embodiments of the present invention will be described with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention thereto, but are merely illustrative examples.

[0031] For example, expressions indicating relative or absolute configurations such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric", or "coaxial" not only strictly represent such configurations, but also represent a state of relative displacement in terms of an angle or distance with a tolerance or to an extent that can achieve the same function.

[0032] For example, expressions indicating a state where things are equal such as "identical", "equal", and "homogeneous" not only strictly represent an equal state, but also represent a state with a tolerance or a difference to an extent that can achieve the same function.

[0033] For example, expressions indicating a shape such as a square shape or a cylindrical shape not only represent a square shape or a cylindrical shape in a strictly geometric sense, but also represent a shape that includes concave and convex portions or chamfered portions within a range where the same effect can be achieved.

[0034] On the other hand, expressions such as "comprising", "including", or "containing" a constituent element are not exclusive expressions that exclude the existence of other constituent elements.

[0035] It should be noted that for the same structure, the same reference numerals are sometimes used and the description is omitted.

[0036] (Centrifugal compressor, turbocharger)

[0037] Figure 1 It is an explanatory diagram for explaining the structure of a turbocharger of a centrifugal compressor having an embodiment. Figure 2 It is a schematic cross-sectional view schematically showing the compressor side of a turbocharger of a centrifugal compressor having an embodiment, and is a schematic cross-sectional view including the axis of the centrifugal compressor.

[0038] The centrifugal compressor 1 of several embodiments of the present disclosure is as Figure 1 , 2 shown and includes an impeller 2 and a scroll housing 3. The scroll housing 3 is as Figure 2 shown and at least has a scroll portion 32 that forms a spiral scroll flow path 31 disposed around the impeller 2.

[0039] The centrifugal compressor 1 can be applied to, for example, turbochargers 10 for automotive, marine, or power generation use, and other industrial centrifugal compressors, blowers, etc. In the illustrated embodiment, the centrifugal compressor 1 is mounted on the turbocharger 10. The turbocharger 10 is as Figure 1 shown and includes a centrifugal compressor 1, a turbine 11, and a rotating shaft 12. The turbine 11 includes a turbine rotor 13 mechanically connected to the impeller 2 via the rotating shaft 12 and a turbine housing 14 that rotatably houses the turbine rotor 13.

[0040] In the illustrated embodiment, the turbocharger 10 also includes a bearing 15 that rotatably supports the rotating shaft 12 and a bearing housing 16 configured to house the bearing 15 as shown in Figure 1 . The bearing housing 16 is disposed between the scroll housing 3 and the turbine housing 14 and is mechanically connected to the scroll housing 3 and the turbine housing 14 by fastening members such as fastening bolts.

[0041] Hereinafter, for example, as shown in Figure 1 , the direction in which the axis CA of the centrifugal compressor 1, that is, the axis of the impeller 2, extends is defined as the axial direction X, and the direction orthogonal to the axis CA is defined as the radial direction Y. The upstream side in the suction direction of the centrifugal compressor 1 in the axial direction X, that is, the side where the fluid inlet 33 is located with respect to the impeller 2 (left side in the figure), is defined as the front side XF. And, the downstream side in the suction direction of the centrifugal compressor 1 in the axial direction X, that is, the side where the impeller 2 is located with respect to the fluid inlet 33 (right side in the figure), is defined as the rear side XR.

[0042] In the illustrated embodiment, as shown in Figure 1 , the scroll housing 3 is formed with a fluid inlet 33 for introducing a fluid (e.g., air) from the outside of the scroll housing 3 and a fluid outlet 34 for discharging the fluid that has passed through the impeller 2 and the scroll flow path 31 to the outside of the scroll housing 3. The turbine housing 14 is formed with an exhaust gas inlet 141 for introducing exhaust gas into the inside of the turbine housing 14 and an exhaust gas outlet 142 for discharging the exhaust gas that has passed through the turbine rotor 13 to the outside of the turbine housing 14.

[0043] The rotating shaft 12 has a length direction along the axial direction X as shown in Figure 1 . The rotating shaft 12 is mechanically connected to the impeller 2 on one side (front side XF) in its length direction and is mechanically connected to the turbine rotor 13 on the other side (rear side XR) in its length direction. It should be noted that "along a certain direction" in the present disclosure includes not only a certain direction but also a direction inclined with respect to a certain direction.

[0044] The turbocharger 10 rotates the turbine rotor 13 by means of exhaust gas introduced from an exhaust gas generating device (e.g., an internal combustion engine such as an engine) (not shown) through the exhaust gas inlet 141 and into the inside of the turbine housing 14. The impeller 2 is mechanically connected to the turbine rotor 13 via the rotating shaft 12, and thus rotates in linkage with the rotation of the turbine rotor 13. The turbocharger 10 compresses the fluid introduced through the fluid inlet 33 and into the inside of the scroll housing 3 by rotating the impeller 2 and conveys it through the fluid outlet 34 to the fluid supply destination (e.g., an internal combustion engine such as an engine).

[0045] (Impeller)

[0046] The impeller 2 is as shown inFigure 2 includes a hub 21 and a plurality of impeller blades 23 provided on an outer surface 22 of the hub 21 as shown. The hub 21 is mechanically fixed to one side of the rotating shaft 12, so that the hub 21 and the plurality of impeller blades 23 are arranged to rotate integrally with the rotating shaft 12 about the axis CA of the impeller 2. The impeller 2 is configured to guide the fluid introduced from the front side XF in the axial direction X to the outside in the radial direction Y. In the illustrated embodiment, the plurality of impeller blades 23 are arranged at intervals from each other in the circumferential direction about the axis CA. A gap (void) is formed between the tip side edges 24 of the plurality of impeller blades 23 and a shroud surface 35 that is convexly curved so as to face the tip side edges 24.

[0047] (Scroll housing)

[0048] In the illustrated embodiment, the scroll housing 3 has, as Figure 2 shown, an intake passage portion 37 that forms an intake air passage 36 for guiding the fluid from the outside of the scroll housing 3 to the impeller 2, a shroud portion 38 having a shroud surface 35, and a scroll portion 32 that forms the above-described scroll passage 31 for guiding the fluid that has passed through the impeller 2 to the outside of the scroll housing 3. The scroll passage 31 and the intake air passage 36 are respectively formed inside the scroll housing 3.

[0049] The intake passage portion 37 has an inner wall surface 370 that forms the intake air passage 36. The inner wall surface 370 extends along the axial direction X, and the above-described fluid inlet 33 is formed at the front side XF end thereof. The scroll portion 32 has an inner circumferential surface 320 that forms the scroll passage 31.

[0050] And, in the illustrated embodiment, the scroll housing 3 has, as Figure 2 shown, an impeller chamber 39 that forms a space for rotatably accommodating the impeller 2 and a diffuser passage 40 for guiding the fluid from the impeller 2 to the scroll passage 31 by being combined with other components (such as the bearing housing 16, etc.).

[0051] The above-mentioned shroud portion 38 is provided between the intake air flow path portion 37 and the scroll portion 32. The shroud surface 35 of the shroud portion 38 forms the front side XF portion of the impeller chamber 39. Further, the shroud portion 38 also has a tip-side flow path surface 41, which forms the front side XF portion of the diffuser flow path 40 and connects the shroud surface 35 to one end of the inner peripheral surface 320 of the scroll portion 32. In the illustrated embodiment, the bearing housing 16 has an impeller chamber forming surface 161 and a hub-side flow path surface 162. The impeller chamber forming surface 161 is located on the rear side XR with respect to the shroud surface 35 and forms the rear side XR portion of the impeller chamber 39. The hub-side flow path surface 162 is provided opposite to the tip-side flow path surface 41 at a position on the rear side XR with respect to the tip-side flow path surface 41 and connects the impeller chamber forming surface 161 to the other end (the first position P1 described later) of the inner peripheral surface 320 of the scroll portion 32. In Figure 2 In the cross section along the axis CA as shown, the tip-side flow path surface 41 and the hub-side flow path surface 162 each extend in a direction intersecting (orthogonal in the illustrated example) with the axis CA.

[0052] The fluid introduced into the interior of the scroll housing 3 flows rearward XR in the intake air flow path 36 and then is transmitted to the impeller 2. The fluid transmitted to the impeller 2 flows in the diffuser flow path 40 and the scroll flow path 31 in this order and is then discharged to the outside of the scroll housing 3 from the fluid discharge port 34.

[0053] (Scroll cross section)

[0054] Figure 3 and Figure 4 are explanatory diagrams for explaining the shape of the scroll portion of the scroll housing according to an embodiment. In Figure 3 、 Figure 4 a cross section of the scroll housing 3 along the axis CA is schematically shown.

[0055] Hereinafter, as Figure 3 、 Figure 4As shown, in the inner circumferential surface 320 of the scroll portion 32, the connection position of the centrifugal compressor 1 to the hub side flow path surface 162 of the diffuser flow path 40 is defined as the first position P1, the outermost end in the radial direction Y of the centrifugal compressor 1 is defined as the second position P2, the foremost end in the axial direction X of the centrifugal compressor 1 is defined as the third position P3, the innermost end in the radial direction Y is defined as the fourth position P4, and the end position on the one-direction UD side, which is the side along the inner circumferential surface 320 of the scroll portion 32 from the first position P1 toward the fourth position P4, is defined as the fifth position P5. It should be noted that the first position P1 is the rear end in the axial direction X in the inner circumferential surface 320 and is a position where the radius of curvature changes from infinity (a straight line) to a finite value. Also, the one-direction UD is the counterclockwise direction centered on the center SC of the scroll flow path 31 in the cross-section of the scroll housing 3 along the axis CA, and the one-direction UD side is the downstream side thereof.

[0056] The scroll housings 3 of several embodiments are as Figure 3 、 Figure 4 shown and include a scroll portion 32 (32A, 32B) that forms the scroll flow path 31 of the centrifugal compressor 1. The scroll portion 32 (32A, 32B) has a nearly circular scroll cross-section 42 as Figure 3 、 Figure 4 shown, and this nearly circular scroll cross-section 42 includes at least a first arc portion 5 extending toward the one-direction UD side from the first position P1, a second arc portion 6 formed on the one-direction UD side of the first arc portion 5, and a third arc portion 7 formed on the one-direction UD side of the second arc portion 6. The second arc portion 6 is formed to include at least a part of the region between the second position P2 and the fourth position P4. The third arc portion 7 is formed to include at least the fifth position P5. It should be noted that in Figure 3 、 Figure 4 , the first arc portion 5 is shown by a single-dot dash line, the second arc portion 6 is shown by a dashed line, and the third arc portion 7 is shown by a double-dot dash line.

[0057] The radius of curvature of the first arc portion 5 is defined as R1, the radius of curvature of the second arc portion 6 is defined as R2, and the radius of curvature of the third arc portion 7 is defined as R3. In the embodiments shown in Figure 3 and Figure 4 , the first arc portion 5, the second arc portion 6, and the third arc portion 7 are each formed with a constant radius of curvature R1 to R3 from their upstream ends to their downstream ends.

[0058] As Figure 3 、 Figure 4 shown, the first arc portion 5 is preferably smoothly continuous with the hub side flow path surface 162 and the second arc portion 6. Also, the third arc portion 7 is preferably smoothly continuous with the second arc portion 6. And the nearly circular scroll cross-section 42 is preferably a shape close to a perfect circle.

[0059] Hereinafter, sometimes the upstream end in one direction UD is simply referred to as the "upstream end", and the downstream end in one direction UD is simply referred to as the "downstream end".

[0060] In Figure 3 In the illustrated embodiment, the first arc portion 5 of the scroll portion 32 (32A) extends from a first position P1 on the inner peripheral surface 320 to a second position P2. The second arc portion 6 extends from the second position P2 on the inner peripheral surface 320 to a third position P3. The third arc portion 7 extends from the third position P3 on the inner peripheral surface 320 to a fifth position P5.

[0061] The upstream end 51 of the first arc portion 5 of the scroll portion 32 (32A) is connected to the hub-side flow path surface 162 at the first position P1, and the downstream end 52 is connected to the upstream end 61 of the second arc portion 6 at the second position P2. The upstream end 71 of the third arc portion 7 is connected to the downstream end 62 of the second arc portion 6 at the third position P3, and the downstream end 72 is located at the fifth position P5.

[0062] In Figure 4 In the illustrated embodiment, the nearly circular scroll cross-section 42 of the scroll portion 32 (32B) further includes a first straight portion 8 that connects the first arc portion 5 and the second arc portion 6. The first straight portion 8 extends along the axial direction X. The first arc portion 5 of the scroll portion 32 (32B) extends from a first position P1 on the inner peripheral surface 320 to a position P6 on the upstream side in one direction UD with respect to the second position P2. The second arc portion 6 extends from the second position P2 on the inner peripheral surface 320 to a fourth position P4. The third arc portion 7 extends from the fourth position P4 on the inner peripheral surface 320 to a fifth position P5.

[0063] The upstream end 51 of the first arc portion 5 of the scroll portion 32 (32B) is connected to the hub-side flow path surface 162 at the first position P1, and the downstream end 52 is connected to the upstream end (rear side end) 81 of the first straight portion 8 at a position P6 on the upstream side in one direction UD with respect to the second position P2. The upstream end 61 of the second arc portion 6 is connected to the downstream end (front side end) of the first straight portion 8 at the second position P2, and the downstream end 62 is connected to the upstream end 71 of the third arc portion 7 at the fourth position P4. The downstream end 72 of the third arc portion 7 is located at the fifth position P5.

[0064] It should be noted that in several other embodiments, the nearly circular scroll cross-section 42 of the scroll portion 32 (32A, 32B) may also further include an unillustrated second straight portion that connects the second arc portion 6 and the third arc portion 7.

[0065] Figure 5 It is an explanatory diagram for explaining the shape of the scroll portion of the scroll housing of the comparative example. Figure 6 It is forFigure 3 , Figure 4 A comparative diagram comparing the shape of the scroll part of an embodiment shown in Figure 5 with the shape of the scroll part of a comparative example shown in Figure 6 . In

[0066] , the relationship between the position and the radius of curvature in the inner peripheral surface 320 of the scroll part 32 (32A, 32B, 32C) is shown. Figure 5 The scroll housing 30 of the comparative example includes a scroll part 32C that forms a scroll flow path 31 as shown in Figure 5 . The scroll part 32C has a nearly circular scroll cross-section 42A, and the nearly circular scroll cross-section 42A includes a first circular arc part 5A extending from a first position P1 toward one direction UD side, and a second circular arc part 6A formed on the one direction UD side of the first circular arc part 5A and formed to include at least a fifth position P5. The radius of curvature of the first circular arc part 5A is defined as R4, and the radius of curvature of the second circular arc part 6A is defined as R5. The first circular arc part 5A and the second circular arc part 6A are each formed with a constant radius of curvature R4, R5 from their respective upstream ends to their downstream ends. It should be noted that in

[0067] , the first circular arc part 5A is shown by a single-dot chain line, and the second circular arc part 6A is shown by a double-dot chain line.

[0068] As shown in Figure 6 , the nearly circular scroll cross-section 42 of the scroll part 32 (32A, 32B) includes three circular arc parts (a first circular arc part 5, a second circular arc part 6, and a third circular arc part 7). In this case, compared with the nearly circular scroll cross-section 42A (comparative example) including two circular arc parts (the first circular arc part 5A and the second circular arc part 6A), the difference in the radius of curvature between the circular arc parts can be suppressed to be smaller on the one direction UD side of the second position P2. For example, the difference in the radius of curvature between the second circular arc part 6 and the third circular arc part 7 in the scroll part 32 (32A, 32B) can be made smaller than the difference in the radius of curvature between the first circular arc part 5A and the second circular arc part 6A of the scroll part 32C of the comparative example.

[0069] For example Figure 3As shown, the fluid flowing into the scroll flow path 31 from the diffusion flow path 40 has a swirling velocity component. Therefore, a swirling flow SF that flows along the inner circumferential surface 320 toward the one-direction UD side is formed at a position on the one-direction UD side of the second position P2. At a position on the one-direction UD side of the second position P2 in the inner circumferential surface 320, the difference in the radius of curvature between the arc portions is suppressed to be small, and the amount of change in the curvature of the inner circumferential surface 320 is small. As a result, the pressure loss of the swirling flow SF in the scroll flow path 31 can be suppressed. During high-flow operation of the centrifugal compressor 1, the swirling velocity component of the swirling flow SF becomes larger, so the degree of pressure loss of the swirling flow SF in the scroll flow path 31 becomes larger. In response to this, by making the amount of change in the curvature of the inner circumferential surface 320 small, a high pressure loss reduction effect can be obtained. Thereby, the efficiency during high-flow operation of the centrifugal compressor 1 can be effectively improved.

[0070] According to the above structure, the scroll portion 32 (32A, 32B) has a nearly circular scroll cross section 42, and the nearly circular scroll cross section 42 includes a first arc portion 5, a second arc portion 6, and a third arc portion 7. The first arc portion 5 includes at least the first position P1. The second arc portion 6 is formed at a position on the one-direction UD side of the first arc portion 5 and includes at least a part of the region between the second position P2 and the fourth position P4. The third arc portion 7 is formed at a position on the one-direction UD side of the second arc portion 6 and includes at least the fifth position P5. In this case, since the nearly circular scroll cross section 42 includes three arc portions (the first arc portion 5, the second arc portion 6, and the third arc portion 7), the difference in the radius of curvature between the arc portions can be suppressed to be smaller than in the case of including two arc portions (for example, the first arc portion 5A and the second arc portion 6A). As a result, from the first arc portion 5 to the third arc portion 7 of the nearly circular scroll cross section 42, the generation of pressure loss associated with a sudden change in curvature can be effectively suppressed.

[0071] In several embodiments, as Figure 6 shown, the inner circumferential surface 320 of the above-mentioned scroll portion 32 (32A, 32B) is formed such that its radius of curvature monotonically decreases toward the one-direction UD side at least in the range from the second position P2 to the fifth position P5 (preferably in the range from the first position P1 to the fifth position P5). In this case, the change in curvature in the nearly circular scroll cross section 42 can be made gentle, so the generation of pressure loss associated with a sudden change in curvature in the scroll flow path 31 can be suppressed.

[0072] In several embodiments, as Figure 3 、 Figure 4 、 Figure 6As shown, the nearly circular vortex cross-section 42 of the above-described vortex portion 32 (32A, 32B) satisfies the relationship R2 > R3. By making the radius of curvature R2 of the second arc portion 6 larger than the radius of curvature R3 of the third arc portion 7, the change in curvature between the second arc portion 6 and the third arc portion 7 in the nearly circular vortex cross-section 42 can be made gentle. By making the change in curvature between the second arc portion 6 and the third arc portion 7 gentle, the generation of pressure loss associated with the abrupt change in curvature between the second arc portion 6 and the third arc portion 7 can be suppressed. And, according to the above structure, within the range from the second position P2 to the fifth position P5 in the inner peripheral surface 320, the radius of curvature of the inner peripheral surface 320 can be made to monotonically decrease as it faces the one direction UD side.

[0073] In several embodiments, as Figure 3 , 6 shown, the nearly circular vortex cross-section 42 of the above-described vortex portion 32 (32A) satisfies the relationship R1 > R2. By making the radius of curvature R1 of the first arc portion 5 larger than the radius of curvature R2 of the second arc portion 6, the change in curvature between the first arc portion 5 and the second arc portion 6 in the nearly circular vortex cross-section 42 can be made gentle. Thereby, the generation of pressure loss associated with the abrupt change in curvature between the first arc portion 5 and the second arc portion 6 can be effectively suppressed. And, according to the above structure, within the range from the first position P1 to the fifth position P5 in the inner peripheral surface 320, the radius of curvature of the inner peripheral surface 320 can be made to monotonically decrease as it faces the one direction UD side.

[0074] In several embodiments, as Figure 4 , Figure 6 shown, the nearly circular vortex cross-section 42 of the above-described vortex portion 32 (32B) satisfies the relationship R2 > R1. By making the radius of curvature R1 of the first arc portion 5 smaller than the radius of curvature R2 of the second arc portion 6, the distance from the outermost end (second position P2) in the radial direction of the vortex flow path 31 to the axis CA of the centrifugal compressor 1 can be shortened, thus achieving miniaturization of the scroll housing 30 and further achieving miniaturization of the centrifugal compressor 1. And, the region 31A facing the first arc portion 5 in the vortex flow path 31 is the region where the fluid from the diffuser flow path 40 enters, and the swirling flow SF formed in the vortex flow path 31 is formed on the downstream side (one direction UD side) of the above region 31A. Therefore, even if the radius of curvature R1 of the first arc portion 5 is smaller than the radius of curvature R2 of the second arc portion 6, by suppressing the generation of pressure loss on the downstream side of the above region 31A, the generation of pressure loss in the vortex flow path can be sufficiently suppressed. It should be noted that the radius of curvature R1 of the first arc portion 5 may also be smaller than the radius of curvature R3 of the third arc portion 7.

[0075] In several embodiments, as Figure 4As shown, the nearly circular vortex cross-section 42 of the above-described vortex portion 32 (32B) satisfies the relationship of R2 > R1. Further, the nearly circular vortex cross-section 42 includes a first straight portion 8 that connects the first arc portion 5 and the second arc portion 6.

[0076] When the distance of the outermost end in the radial direction (second position P2) of the vortex flow path 31 from the axis CA of the centrifugal compressor 1 is shortened, it may be difficult to directly connect the first arc portion 5 and the second arc portion 6. According to the above-described structure, by the first straight portion 8 that connects the first arc portion 5 and the second arc portion 6, a shape that can easily connect the first arc portion 5 and the second arc portion 6 can be formed. It should be noted that when the first straight portion 8 is long, an increase in pressure loss in the vortex flow path 31 may occur. Therefore, it is preferable to make the first straight portion 8 as short as possible.

[0077] Figure 7 It is an explanatory diagram for explaining the shape of the vortex portion of the scroll housing according to an embodiment. In Figure 7 it, the relationship between the position and the radius of curvature in the inner peripheral surface 320 of the above-described vortex portion 32 (32A) is shown. Further, in Figure 7 a vortex portion 32D including an infinite number of arc portions configured such that the curvature of the inner peripheral surface 320 continuously decreases toward one direction UD side is shown together.

[0078] In several embodiments, as Figure 7 shown, the nearly circular vortex cross-section 42 of the above-described vortex portion 32 (32A) satisfies the relationships of R2 / R1 ≥ 0.8 and R3 / R2 ≥ 0.8. Preferably, the nearly circular vortex cross-section 42 satisfies the relationships of R2 / R1 ≥ 0.9 and R3 / R2 ≥ 0.9.

[0079] According to the above-described structure, the nearly circular vortex cross-section 42 satisfies the relationship of R2 / R1 ≥ 0.8. In other words, the reduction rate of the radius of curvature of the second arc portion 6 relative to the radius of curvature of the first arc portion 5 is 20% or less. By making the amount of change in curvature between the first arc portion 5 and the second arc portion 6 small, generation of pressure loss associated with a sudden change in curvature between the first arc portion 5 and the second arc portion 6 can be effectively suppressed. Further, the nearly circular vortex cross-section 42 satisfies the relationship of R3 / R2 ≥ 0.8. In other words, the reduction rate of the radius of curvature of the third arc portion 7 relative to the radius of curvature of the second arc portion 6 is 20% or less. By making the amount of change in curvature between the second arc portion 6 and the third arc portion 7 small, generation of pressure loss associated with a sudden change in curvature between the second arc portion 6 and the third arc portion 7 can be effectively suppressed.

[0080] In particular, when the nearly circular vortex cross-section 42 satisfies the relationships of R2 / R1≥0.9 and R3 / R2≥0.9, a reduction effect of pressure loss that is almost comparable to the case where the curvature of the inner peripheral surface 320 in the nearly circular vortex cross-section 42 continuously decreases toward one direction UD side (vortex portion 32D) can be obtained.

[0081] Figure 8 It is an explanatory diagram for explaining the shape of the vortex portion of the vortex housing according to an embodiment. In Figure 8 it shows the relationship between the position and the radius of curvature in the inner peripheral surface 320 of the above-mentioned vortex portion 32 (32B). And in Figure 8 it shows together the reduced vortex portion 32E including an infinite number of circular arc portions formed in such a way that the curvature of the inner peripheral surface 320 continuously becomes smaller toward one direction UD side.

[0082] In several embodiments, as Figure 8 shown, the nearly circular vortex cross-section 42 of the above-mentioned vortex portion 32 (32B) satisfies the relationship of R3 / R2≥0.8. Preferably, the nearly circular vortex cross-section 42 satisfies the relationship of R3 / R2≥0.9.

[0083] According to the above structure, the nearly circular vortex cross-section 42 satisfies the relationship of R3 / R2≥0.8. In other words, the reduction rate of the radius of curvature of the third circular arc portion 7 relative to the radius of curvature of the second circular arc portion 6 is 20% or less. By making the amount of curvature change between the second circular arc portion 6 and the third circular arc portion 7 small, the generation of pressure loss associated with the sudden change in curvature between the second circular arc portion 6 and the third circular arc portion 7 can be effectively suppressed.

[0084] In particular, when the nearly circular vortex cross-section 42 satisfies the relationship of R3 / R2≥0.9, a reduction effect of pressure loss that is almost comparable to the case where the curvature of the inner peripheral surface 320 in the nearly circular vortex cross-section 42 continuously decreases toward one direction UD side (vortex portion 32E) can be obtained.

[0085] In the above several embodiments, the above-mentioned nearly circular vortex cross-section 42 includes three circular arc portions (first circular arc portion 5, second circular arc portion 6, and third circular arc portion 7) each having a constant radius of curvature. However, in other several embodiments, the nearly circular vortex cross-section 42 is formed, for example, in Figure 7 、 Figure 8In the range of at least from the second position P2 to the fifth position P5 (preferably from the first position P1 to the fifth position P5) of the inner peripheral surface 320 as shown, the curvature of the inner peripheral surface 320 continuously decreases as it faces the one-direction UD side. In this case, the pressure loss in the vortex flow path 31 can be effectively suppressed, but it is difficult to form the shape of the inner peripheral surface 320, which may lead to an increase in the manufacturing cost of the vortex housing 3. In contrast, the nearly circular vortex cross-section 42 including the three arc portions described above is easy to form the shape of the inner peripheral surface 320, and an increase in the manufacturing cost of the vortex housing 3 can be suppressed.

[0086] Figure 9 It is a schematic diagram of a vortex flow path in an axial view of a centrifugal compressor according to an embodiment.

[0087] As Figure 9 shown, regarding the angular position θ around the vortex center O in the above-mentioned vortex flow path 31, the confluence position of the vortex start 311 and the vortex end 312 of the vortex flow path 31 is set to 60 degrees, and the angular position θ is defined in such a way that the angle gradually increases toward the downstream side of the vortex flow path 31 (the clockwise direction around the vortex center O in the figure).

[0088] In several embodiments, as Figure 9 shown, the above-mentioned nearly circular vortex cross-section 42 is formed in the range S where the angular position θ is from 120 degrees to 360 degrees.

[0089] The smaller the cross-sectional area of the vortex flow path 31 is as it gets closer to the vortex start side. Therefore, it may be difficult to form the above-mentioned nearly circular vortex cross-section 42 on the vortex start side. According to the above structure, by forming the nearly circular vortex cross-section 42 in the range S where the angular position θ is from 120 degrees to 360 degrees, where it is easy to form the nearly circular vortex cross-section 42, the generation of pressure loss in the vortex flow path 31 can be sufficiently suppressed. It should be noted that the nearly circular vortex cross-section 42 may also be formed in the range T where the angular position θ is from 0 degrees to 120 degrees. The nearly circular vortex cross-section 42 is preferably formed in the above range S and range T.

[0090] In several embodiments, as Figure 3As shown, the third arc portion 7 in the above-described scroll portion 32 is formed to include at least a third position P3, a fourth position P4, and a fifth position P5. In the illustrated embodiment, the third arc portion 7 has a constant radius of curvature R3 in the range from the third position P3 to the fifth position P5. According to the above structure, since the third arc portion 7 includes the third position P3, the fourth position P4, and the fifth position P5, the near-circular scroll cross-section 42 can have a gentle change in curvature in the range from the third position P3 to the fifth position P5, which is the range required to determine the swirling state of the swirling flow SF formed in the scroll cross-section 42, and can effectively suppress the generation of pressure loss associated with a sudden change in curvature in the above range. In particular, by making the radius of curvature R3 constant in the range from the third position P3 to the fifth position P5, the generation of pressure loss associated with a sudden change in curvature in the above range can be more effectively suppressed.

[0091] The centrifugal compressor 1 of several embodiments is equipped with the above-described scroll housing 3 as Figure 2 shown. In this case, the generation of pressure loss in the scroll flow path 31 can be suppressed, and thus the efficiency of the centrifugal compressor 1 can be improved. In particular, the efficiency of the centrifugal compressor 1 can be effectively improved during high-flow operation.

[0092] The present disclosure is not limited to the above-described embodiments, and also includes modified forms of the above-described embodiments and forms in which these forms are appropriately combined.

[0093] The content described in the above several embodiments can be understood as follows, for example.

[0094] 1) The scroll housing (3) of at least one embodiment of the present disclosure is the scroll housing (3) of a centrifugal compressor (1), wherein

[0095] the scroll housing (3) is provided with a scroll portion (32) that forms the scroll flow path (31) of the centrifugal compressor,

[0096] In the inner peripheral surface (320) of the scroll portion, when the connection position of the centrifugal compressor with the hub-side flow surface (162) of the diffuser flow path (40) is defined as the first position (P1), the outermost end in the radial direction of the centrifugal compressor is defined as the second position (P2), the foremost end in the axial direction of the centrifugal compressor is defined as the third position (P3), the innermost end in the radial direction is defined as the fourth position (P4), and the end position on one direction (UD) side along the inner peripheral surface of the scroll portion from the first position (P1) toward the fourth position (P4) is defined as the fifth position (P5), the scroll portion (32) includes at least a first arc portion (5), a second arc portion (6), and a third arc portion (7).

[0097] Further, in a case where the radius of curvature of the second arc portion (6) is defined as R2 and the radius of curvature of the third arc portion (7) is defined as R3, the vortex portion (32) has a nearly circular vortex cross-section (42) that satisfies the relationship R2 > R3.

[0098] The first arc portion (5) extends from the first position (P1) toward the one-direction side.

[0099] The second arc portion (6) is formed at a position closer to the one-direction side than the first arc portion (5), and is formed to include at least a part of the region between the second position (P2) and the fourth position (P4).

[0100] The third arc portion (7) is formed at a position closer to the one-direction side than the second arc portion (6), and is formed to include at least the fifth position (P5).

[0101] According to the structure of 1) above, the vortex portion (32) has a nearly circular vortex cross-section (42). The nearly circular vortex cross-section (42) includes the first arc portion (5), the second arc portion (6), and the third arc portion (7). The first arc portion (5) includes at least the first position (P1). The second arc portion (6) is formed at a position closer to the one direction (UD) side than the first arc portion (5) and includes at least a part of the region between the second position (P2) and the fourth position (P4). The third arc portion (7) is formed at a position closer to the one-direction side than the second arc portion (6) and includes at least the fifth position (P5). In this case, the nearly circular vortex cross-section (42) includes three arc portions (the first arc portion 5, the second arc portion 6, and the third arc portion 7). Therefore, compared with the case including two arc portions, the difference in the radius of curvature between the arc portions can be suppressed to be smaller. Thereby, from the first arc portion (5) to the third arc portion (7) of the nearly circular vortex cross-section (42), the generation of pressure loss associated with a sudden change in curvature can be effectively suppressed.

[0102] Further, according to the structure of 1) above, the radius of curvature R2 of the second arc portion (6) is greater than the radius of curvature R3 of the third arc portion (7). In this case, the change in curvature between the second arc portion (6) and the third arc portion (7) in the nearly circular vortex cross-section (42) can be made gentle. By making the change in curvature between the second arc portion (6) and the third arc portion (7) gentle, the generation of pressure loss associated with a sudden change in curvature between the second arc portion (6) and the third arc portion (7) can be suppressed.

[0103] 2) In several embodiments, according to the scroll housing (3) described in 1) above, wherein,

[0104] In the case where the radius of curvature of the first arc portion (5) is defined as R1, the near-circular vortex cross-section (42) satisfies the relationship R1 > R2.

[0105] According to the structure of 2) above, in the near-circular vortex cross-section (42), the radius of curvature R1 of the first arc portion (5) is greater than the radius of curvature R2 of the second arc portion (6). In this case, the change in curvature between the first arc portion (5) and the second arc portion (6) in the near-circular vortex cross-section (42) can be made gentle. Thereby, the generation of pressure loss associated with a sudden change in curvature between the first arc portion (5) and the second arc portion (6) can be effectively suppressed.

[0106] 3) In several embodiments, according to the scroll housing (3) described in 1) above, wherein,

[0107] In the case where the radius of curvature of the first arc portion (5) is defined as R1, the near-circular vortex cross-section (42) satisfies the relationship R2 > R1.

[0108] According to the structure of 3) above, in the near-circular vortex cross-section (42), the radius of curvature R1 of the first arc portion (5) is less than the radius of curvature R2 of the second arc portion (6). In this case, the distance from the outermost end in the radial direction (the second position P2) of the vortex flow path (31) to the axis (CA) of the centrifugal compressor can be made short, so that the miniaturization of the scroll housing (30) is achieved, and further the miniaturization of the centrifugal compressor (1) is achieved. And the region (31A) in the vortex flow path (31) facing the first arc portion (5) is the region where the fluid from the diffuser flow path (40) enters, and the swirling flow (SF) formed in the vortex flow path (31) is formed on the downstream side (one direction UD side) of the above region (31A). Therefore, even if the radius of curvature R1 of the first arc portion (5) is less than the radius of curvature R2 of the second arc portion (6), by suppressing the generation of pressure loss on the downstream side of the above region (31A), the generation of pressure loss in the vortex flow path (31) can be sufficiently suppressed.

[0109] 4) In several embodiments, according to the scroll housing (3) described in 3) above, wherein,

[0110] The near-circular vortex cross-section (42) further includes a first straight portion (8) connecting the first arc portion (5) and the second arc portion (5).

[0111] When the distance of the outermost end (second position P2) in the radial direction of the vortex flow path (31) from the axis (CA) of the centrifugal compressor (1) is shortened, it may be difficult to directly connect the first arc portion (5) and the second arc portion (6). According to the structure of the above 4), the first straight portion (8) connecting the first arc portion (5) and the second arc portion (6) enables the shape of easily connecting the first arc portion (5) and the second arc portion (6) to be established.

[0112] 5) In several embodiments, according to the scroll housing (3) described in the above 2), wherein,

[0113] The near-circular scroll cross-section (42) satisfies the relationship of R2 / R1≥0.8 and R3 / R2≥0.8.

[0114] According to the structure of the above 5), the near-circular scroll cross-section (42) satisfies the relationship of R2 / R1≥0.8. In other words, the reduction rate of the curvature radius R2 of the second arc portion (6) relative to the curvature radius R1 of the first arc portion (5) is 20% or less. By making the curvature change amount between the first arc portion (5) and the second arc portion (6) small, the generation of pressure loss associated with the sudden change in curvature between the first arc portion (5) and the second arc portion (6) can be effectively suppressed. And, the near-circular scroll cross-section (42) satisfies the relationship of R3 / R2≥0.8. In other words, the reduction rate of the curvature radius R3 of the third arc portion (7) relative to the curvature radius R2 of the second arc portion (6) is 20% or less. By making the curvature change amount between the second arc portion (6) and the third arc portion (7) small, the generation of pressure loss associated with the sudden change in curvature between the second arc portion (6) and the third arc portion (7) can be effectively suppressed.

[0115] 6) In several embodiments, according to the scroll housing (3) described in the above 3) or 4), wherein,

[0116] The near-circular scroll cross-section (42) satisfies the relationship of R3 / R2≥0.8.

[0117] According to the structure of the above 6), the near-circular scroll cross-section (42) satisfies the relationship of R3 / R2≥0.8. In other words, the reduction rate of the curvature radius R3 of the third arc portion (7) relative to the curvature radius R2 of the second arc portion (6) is 20% or less. By making the curvature change amount between the second arc portion (6) and the third arc portion (7) small, the generation of pressure loss associated with the sudden change in curvature between the second arc portion (6) and the third arc portion (7) can be effectively suppressed.

[0118] 7) In several embodiments, according to the scroll housing (3) described in any one of the above 1) to 6), wherein,

[0119] Regarding the angular position (θ) around the vortex center (O) in the vortex flow path (31), when the confluence position of the vortex start (311) and the vortex end (312) of the vortex flow path (31) is set to 60 degrees and the angular position (θ) is defined in such a way that the angle gradually increases toward the downstream side of the vortex flow path (31), the nearly circular vortex cross-section (42) is formed within the range (S) where the angular position (θ) is from 120 degrees to 360 degrees.

[0120] The smaller the cross-sectional area of the vortex flow path (31) is as it gets closer to the vortex start (311) side. Therefore, it may be difficult to form the above-mentioned nearly circular vortex cross-section (42) at the vortex start side. According to the structure of the above 7), by forming the nearly circular vortex cross-section (42) within the range (S) where the angular position (θ) is from 120 degrees to 360 degrees, at which it is easy to form the nearly circular vortex cross-section (42), the generation of pressure loss in the vortex flow path (31) can be sufficiently suppressed.

[0121] 8) In several embodiments, according to the vortex housing (3) described in any one of the above 1) to 7), wherein,

[0122] The third arc portion (7) is formed to include at least the third position (P3), the fourth position (P4), and the fifth position (P5).

[0123] According to the structure of the above 8), since the third arc portion (7) includes the third position (P3), the fourth position (P4), and the fifth position (P5), the nearly circular vortex cross-section (42) can make the change in curvature gentle within the range from the third position to the fifth position, which is the range required to determine the swirling state of the swirling flow (SF) formed within the vortex cross-section (42), and the generation of pressure loss associated with the sudden change in curvature within the above range can be effectively suppressed.

[0124] 9) The centrifugal compressor (1) according to at least one embodiment of the present disclosure includes the vortex housing (3) described in any one of the above 1) to 8).

[0125] According to the structure of the above 9), the generation of pressure loss in the vortex flow path (31) can be suppressed, so the efficiency of the centrifugal compressor (1) can be improved. In particular, the efficiency of the centrifugal compressor (1) can be effectively improved during high-flow operation.

[0126] Description of Reference Numerals

[0127] 1 Centrifugal compressor;

[0128] 2 Impeller;

[0129] 21 Hub;

[0130] 22 Outer surface;

[0131] 23 Impeller blade;

[0132] 24 Tip side edge;

[0133] 3, 30 Scroll housing;

[0134] 31 Scroll flow path;

[0135] 31A Region;

[0136] 32, 32A - 32E Scroll part;

[0137] 320 Inner peripheral surface;

[0138] 33 Fluid inlet;

[0139] 34 Fluid outlet;

[0140] 35 Shield surface;

[0141] 36 Inlet air flow path;

[0142] 37 Inlet air flow path part;

[0143] 370 Inner wall surface;

[0144] 38 Shield part;

[0145] 39 Impeller chamber;

[0146] 40 Diffusion flow path;

[0147] 41 Tip side flow surface;

[0148] 42, 42A Nearly circular scroll cross - section;

[0149] 5, 5A First arc part;

[0150] 51, 51A Upstream end;

[0151] 52, 52A Downstream end;

[0152] 6, 6A Second arc part;

[0153] 61, 61A Upstream end;

[0154] 62, 62A Downstream end;

[0155] 7 Third arc part;

[0156] 71 Upstream end;

[0157] 72 Downstream end;

[0158] 8 First straight portion;

[0159] 10 Turbocharger;

[0160] 11 Turbine;

[0161] 12 Rotating shaft;

[0162] 13 Turbine rotor;

[0163] 14 Turbine housing;

[0164] 141 Exhaust gas inlet;

[0165] 142 Exhaust gas outlet;

[0166] 15 Bearing;

[0167] 16 Bearing housing;

[0168] 161 Impeller chamber forming surface;

[0169] 162 Hub side flow path surface;

[0170] CA Axis;

[0171] P1 First position;

[0172] P2 Second position;

[0173] P3 Third position;

[0174] P4 Fourth position;

[0175] P5 Fifth position;

[0176] P6 Position;

[0177] R1 to R5 Radius of curvature;

[0178] S, T Range;

[0179] SF Circulating flow;

[0180] UD One direction;

[0181] X Axial direction;

[0182] XF (Axial) front side;

[0183] XR (Axial) rear side;

[0184] Y Radial direction.

Claims

1. A scroll housing, which is a scroll housing of a centrifugal compressor, characterized in that the scroll housing has a scroll portion that forms a scroll flow path of the centrifugal compressor, in the inner peripheral surface of the scroll portion, when the connection position of the centrifugal compressor with the hub side flow surface of the diffuser flow path is defined as the first position, the outermost end in the radial direction of the centrifugal compressor is defined as the second position, the foremost end in the axial direction of the centrifugal compressor is defined as the third position, the innermost end in the radial direction is defined as the fourth position, and the end position on one side in the direction from the first position toward the fourth position along the inner peripheral surface of the scroll portion is defined as the fifth position, the scroll portion at least includes a first arc portion, a second arc portion, and a third arc portion, and, when the radius of curvature of the first arc portion is defined as R1, the radius of curvature of the second arc portion is defined as R2, and the radius of curvature of the third arc portion is defined as R3, the scroll portion has a nearly circular scroll cross-section satisfying the relationship of R1 > R2 > R3, the first arc portion extends from the first position toward the one direction side, the second arc portion is formed at a position closer to the one direction side than the first arc portion, and is formed to include at least a part of the region between the second position and the fourth position, including the second position and the third position, the third arc portion is formed at a position closer to the one direction side than the second arc portion, and is formed to include at least the fifth position.

2. The scroll housing according to claim 1, wherein the nearly circular scroll cross-section satisfies the relationship of R2 / R1 ≥ 0.8 and R3 / R2 ≥ 0.

8.

3. The scroll housing according to claim 1, wherein with respect to the angular position around the scroll center in the scroll flow path, when the confluence position of the start and end of the scroll flow path is set to 60 degrees and the angular position is defined in such a way that the angle gradually increases toward the downstream side of the scroll flow path, the nearly circular scroll cross-section is formed within the range of the angular position from 120 degrees to 360 degrees.

4. The scroll housing according to claim 2, wherein with respect to the angular position around the scroll center in the scroll flow path, when the confluence position of the start and end of the scroll flow path is set to 60 degrees and the angular position is defined in such a way that the angle gradually increases toward the downstream side of the scroll flow path, the nearly circular scroll cross-section is formed within the range of the angular position from 120 degrees to 360 degrees.

5. The scroll housing according to any one of claims 1 to 4, wherein the third arc portion is formed to include at least the third position, the fourth position, and the fifth position.

6. A centrifugal compressor, comprising the scroll housing according to any one of claims 1 to 5.

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