JP2018080620A - Turbine unit and turbo charger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a turbine unit and a turbo charger capable of suppressing the reduction of a turbine efficiency, which is caused by the dispersion of the pressure distribution of a fluid that flows into a turbine rotor and flows in a passage formed around the turbine rotor.SOLUTION: There are made equivalent the flow passage area of a first passage section at the upstream end of a scroll flow passage and the flow passage area of a second passage section at the downstream end of the scroll flow passage. This results in the small dispersion of the pressure distribution of a fluid to flow in a flow passage formed around a turbine rotor.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a turbine unit and a turbocharger.

  In Patent Document 1, after working gas is caused to flow in a radial direction from a spiral scroll formed in a turbine casing to a turbine rotor blade of a turbine rotor located inside the scroll, A radial turbine scroll structure configured to rotationally drive a turbine rotor by flowing in an axial direction is described.

Japanese Patent No. 5047364

  A turbine unit for a turbocharger includes a rotating turbine rotor and a housing in which a scroll flow path through which a fluid flowing into the turbine rotor flows is formed. The scroll flow path is formed around the turbine rotor as viewed from the direction of the rotation axis of the turbine rotor. And if the pressure distribution of the fluid which flows through this scroll flow path varies, turbine efficiency will fall.

  An object of the present invention is to suppress a decrease in turbine efficiency due to variations in pressure distribution of a fluid flowing into a turbine rotor and flowing through a flow path formed around the turbine rotor. It is.

  A turbine unit according to a first aspect of the present invention is a turbine rotor that is pushed by a fluid flowing in from a radially outer side and rotates around an axis, and a housing that accommodates the turbine rotor therein, the turbine rotor being disposed in the turbine rotor. The inflowing fluid flows, and a scroll flow path formed in an arc shape around the turbine rotor as viewed from the axial direction of the turbine rotor, and an introduction flow path for guiding the fluid to the scroll flow path are formed. And in the scroll flow path, an upstream end in a fluid flow direction and a downstream end in the flow direction are separated in a circumferential direction of the turbine rotor, and the introduction flow path includes: The downstream end of the scroll channel is connected, the channel area of the first channel cross section at the upstream end of the scroll channel, and the scroll channel in the introduction channel Upstream end is characterized in that a flow passage area of the second flow path cross-section at the site to which it is connected is equal.

  According to the above configuration, the introduction channel guides the fluid to the upstream end of the scroll channel. Further, the scroll flow channel causes the fluid that has flowed into the scroll flow channel from the upstream end to flow to the downstream end side. Then, the fluid that has flowed from the downstream end of the scroll flow path to the introduction flow path and the fluid that is guided to the upstream end of the scroll flow path by the introduction flow path merge. Further, the introduction channel guides the merged fluid to the upstream end of the scroll channel.

  The fluid flowing through the scroll flow path and the fluid flowing through the introduction flow path flow into the turbine rotor from outside in the radial direction and push the turbine rotor. The turbine rotor is rotated around the axis by being pushed by the fluid.

  Here, the flow path area of the first flow path cross section at the upstream end of the scroll flow path and the flow path area of the second flow path cross section at the site where the downstream end of the scroll flow path is connected in the introduction flow path It is equivalent.

  Thereby, in the site | part to which the downstream end of the scroll flow path is connected in the introduction flow path, it is suppressed that the total pressure of the fluid becomes low. In this way, the variation in the pressure distribution of the fluid is suppressed, so that the turbine efficiency can be prevented from decreasing.

  In other words, it is possible to suppress a decrease in turbine efficiency due to variations in pressure distribution of the fluid flowing into the turbine rotor and flowing through the flow path formed around the turbine rotor. .

  A turbine unit according to a second aspect of the present invention is the turbine unit according to the first aspect, wherein the turbine unit has a straight line passing through the centroid of the first flow path cross section and the rotation center of the turbine rotor as viewed from the axial direction. The distance from the reference line to the centroid of the second flow path section is the distance from the reference line to the centroid of the first flow path section. It is characterized by being equal to or shorter than that.

  According to the above configuration, when viewed from the axial direction, the distance from the reference straight line to the centroid of the second flow path cross section is equal to or shorter than the distance from the reference straight line to the centroid of the first flow path cross section. For this reason, the fluid guided to the upstream end of the scroll flow path by the introduction flow path flows into the scroll flow path from the upstream end, hits the radially outer portion of the turbine rotor on the wall surface constituting the scroll flow path, and scrolls Flow through the flow path.

  Thereby, the dispersion | variation in the pressure distribution of the fluid which flows through a scroll flow path is suppressed. And the dispersion | variation in the pressure distribution of the fluid which flows through a scroll flow path is suppressed in this way, and it can suppress effectively that turbine efficiency falls.

  In other words, it is possible to effectively suppress a decrease in turbine efficiency due to variations in pressure distribution of the fluid flowing into the turbine rotor and flowing through the scroll flow path.

  A turbocharger according to a third aspect of the present invention has a turbine rotor that rotates by being pushed by exhaust gas as a fluid discharged from an engine and rotates from the turbine rotor. And a centrifugal compressor for compressing air supplied to the engine and transmitting force to the impeller.

  According to the said structure, in a turbocharger, by providing the turbine unit of Claim 1 or 2, a turbine rotor rotates efficiently and compressed air can be efficiently supplied to an engine.

  According to the present invention, it is possible to suppress a decrease in turbine efficiency due to a variation in pressure distribution of a fluid flowing into the turbine rotor and flowing through a flow path formed around the turbine rotor. Can do.

It is the expanded front view which showed the turbine unit which concerns on embodiment of this invention. It is the front view which showed the turbine unit which concerns on embodiment of this invention. It is sectional drawing which showed the turbine unit which concerns on embodiment of this invention. (A) (B) It is drawing which showed the analysis result of the turbine unit which concerns on embodiment of this invention, and the analysis result of the turbine unit which concerns on a comparison form. (A) (B) It is drawing which showed the analysis result of the turbine unit which concerns on embodiment of this invention, and the analysis result of the turbine unit which concerns on a comparison form. It is drawing which showed the experimental result of the turbine unit which concerns on embodiment of this invention, and the experimental result of the turbine unit which concerns on a comparison form with the graph. It is the block diagram which showed the turbocharger which concerns on embodiment of this invention. It is the enlarged front view which showed the turbine unit which concerns on the comparison form with respect to embodiment of this invention. It is the front view which showed the turbine unit which concerns on the comparison form with respect to embodiment of this invention. (A) (B) It is sectional drawing which showed the scroll flow path of the turbine unit which concerns on the modification with respect to embodiment of this invention.

  An example of a turbine unit and a turbocharger according to the first embodiment of the present invention will be described with reference to FIGS.

(overall structure)
As shown in FIG. 7, the turbocharger 10 according to the present embodiment includes a turbine unit 20, a centrifugal compressor 30, and a connecting unit 40 that connects the turbine unit 20 and the centrifugal compressor 30. The turbine unit 20 is disposed in the middle of the exhaust passage 12 of an automobile engine (not shown), and the centrifugal compressor 30 is disposed in the middle of the intake passage 14 of the engine.

  The turbine unit 20 includes a housing 24, the centrifugal compressor 30 includes a housing 50, and the connection unit 40 includes a housing 44 that connects the housing 24 and the housing 50.

  Further, the turbocharger 10 includes a rotating shaft 42 that passes through the housing 24, the housing 44, and the housing 50, and the axial direction of the rotating shaft 42 (the direction of arrow E in the figure: hereinafter simply “axial direction”). ) From one end side (right side in the figure) to the other end side (left side in the figure), the housing 24, the housing 44, and the housing 50 are fixed to each other using a fixture (not shown) and are arranged in this order.

(Centrifuge compressor)
As shown in FIG. 7, the centrifugal compressor 30 includes a housing 50 and an impeller 32. The housing 50 has a hollow inside, and the impeller 32 is disposed inside the housing 50. The impeller 32 includes a rotation shaft portion 34 fixed to a portion on the other end side in the axial direction of the rotation shaft 42, and a plurality of impeller blades 36 extending from the rotation shaft portion 34.

  In addition, an inflow channel 52 that guides the air flowing through the intake passage 14 to the impeller 32 is formed on the outer side of the impeller 32 in the axial direction of the impeller 32 (opposite to the housing 44 side) in the housing 50. ing. Further, in the housing 50, air flows out of the housing 50 to the outside of the impeller 32 in the radial direction of the rotary shaft 42 (in the direction of arrow D in the drawing: hereinafter simply “radial direction”). A spiral spiral flow path 54 (so-called scroll flow path) is formed.

[Connecting unit]
As shown in FIG. 7, the connection unit 40 includes a housing 44. And this housing 44 has the support part 44A which supports the rotating shaft 42 rotatably.

  Further, the housing 44 is circulated so that the engine oil supplied to the support portion 44 </ b> A flows into the housing 44 (not shown), and the exhaust port (not shown) discharges the engine oil from the housing 44. ).

  In this configuration, the engine oil that has flowed into the housing 44 is supplied to the support portion 44A so that the rotating shaft 42 rotates smoothly.

[Turbine unit]
As shown in FIG. 7, the turbine unit 20 includes a housing 24 and a turbine rotor 22. The housing 24 has a hollow inside, and the turbine rotor 22 is disposed inside the housing 24. The turbine rotor 22 includes a rotor hub 28 joined to a portion on one end side in the axial direction of the rotating shaft 42, and a plurality of turbine blades 26 extending from the rotor hub 28.

  Further, in the housing 24, exhaust gas, which is an example of fluid flowing in the exhaust passage 12, flows into the inside of the housing 24 at a portion radially outside the rotating shaft 42 side with respect to the turbine rotor 22. A scroll flow path 56 is formed. Further, in the housing 24, an exhaust flow path 58 that causes the exhaust gas to flow out of the housing 24 and be discharged to the exhaust passage 12 at a portion outside the axial direction (opposite to the housing 44 side) with respect to the turbine rotor 22. Is formed.

  Details of the configuration of the turbine unit 20 will be described later.

(Operation of the overall configuration)
Next, the operation of the turbocharger 10 will be described.

  When the turbine blades 26 are pushed by the exhaust gas flowing into the housing 24 from the scroll flow path 56, the turbine rotor 22 rotates. The rotational force of the turbine rotor 22 is transmitted to the impeller 32 via the rotation shaft 42. The exhaust gas that has rotated the turbine rotor 22 inside the housing 24 is discharged from the discharge passage 58 to the exhaust passage 12.

  The impeller 32 rotates when the rotational force of the turbine rotor 22 is transmitted via the rotating shaft 42. The rotating impeller 32 compresses the air guided from the intake passage 14 by the inflow channel 52. Further, the rotating impeller 32 causes the compressed air to flow outward in the radial direction. Further, the compressed air that has flowed outward in the radial direction flows through the spiral flow path 54 and is discharged to the intake passage 14. The compressed air discharged from the spiral flow path 54 is supplied to the engine as compressed air for combustion.

(Main part configuration)
Next, the turbine unit 20 will be described.
As shown in FIG. 3, the turbine unit 20 includes a turbine rotor 22 and a housing 24 in which the turbine rotor 22 is accommodated.

[Turbine rotor]
As described above, the turbine rotor 22 includes the rotor hub 28 joined to a portion on one end side in the axial direction of the rotating shaft 42 and the plurality of turbine blades 26 extending from the rotor hub 28.

  The rotor hub 28 is gradually thinner toward the outer side in the axial direction (the side opposite to the housing 44 side: the right side in the figure). Further, as shown in FIG. 2, each turbine blade 26 extends outward in the radial direction while being curved from the rotor hub 28 when viewed from the axial direction. Then, as shown in FIG. 3, each turbine blade 26 is curved while being curved from a tip edge 26 </ b> A that extends in the radial direction at an outer portion in the axial direction and a radially outer end portion of the tip edge 26 </ b> A. And a curved edge 26 </ b> B extending inward in the direction (housing 44 side: left side in the figure). Furthermore, each turbine blade 26 has a base end edge 26C extending in the axial direction from the end of the curved edge 26B.

  In this configuration, the turbine blades 26 are pushed by the exhaust gas flowing into the turbine rotor 22 from the radially outer side through the base edge 26C of the turbine blades 26 so that the turbine rotor 22 rotates around the rotation shaft 42. It has become. The rotating turbine rotor 22 causes the exhaust gas that has pushed the turbine blades 26 to flow outward from the tip edge 26A of the turbine blades 26 in the axial direction.

〔housing〕
As shown in FIG. 2, the housing 24 has a scroll flow path 56 formed around the turbine rotor 22 and an introduction flow path 62 that guides exhaust gas to the scroll flow path 56 when viewed from the axial direction. doing. Further, as shown in FIG. 3, the housing 24 includes a speed increasing flow path 64 (so-called nozzle flow path) for flowing exhaust gas flowing in the scroll flow path 56 to the turbine rotor 22 side, and a tip edge 26 </ b> A of the turbine blade 26. And an exhaust passage 58 through which the exhaust gas flowing out in the axial direction flows.

  As shown in FIG. 2, the scroll flow path 56 is formed in an arc shape around the turbine rotor 22 when viewed from the axial direction, and flows exhaust gas flowing into the turbine rotor 22. The cross section of the scroll flow path 56 has a circular shape (see FIG. 3). Further, the flow passage area of the scroll flow passage 56 gradually decreases from the upstream side to the downstream side in the flow direction in which the exhaust gas flows (hereinafter referred to as an arrow in the “gas flow direction” diagram). The upstream end 56 </ b> A in the gas flow direction of the scroll flow path 56 and the downstream end 56 </ b> B in the gas flow direction are separated from each other in the circumferential direction of the turbine rotor 22.

  Details of the position of the upstream end 56A of the scroll flow path 56, the cross section of the scroll flow path 56 at the upstream end 56A (hereinafter, “first flow path cross section 80”), and the like will be described later.

  The introduction flow path 62 is formed so that the centroid is linear between the upstream end 56A of the scroll flow path 56 and the exhaust passage 12 when viewed from the axial direction. The exhaust gas is guided to the upstream end 56A. The cross section of the introduction flow path 62 has a circular shape. Further, the downstream end 56 </ b> B of the scroll flow path 56 is connected to an intermediate portion of the introduction flow path 62 in the gas flow direction.

  As shown in FIG. 1, the downstream end 56 </ b> B of the scroll flow path 56 is formed with a tongue portion 66 that connects the wall surface constituting the introduction flow path 62 and the wall face constituting the scroll flow path 56. The tongue 66 has an arcuate shape that protrudes downstream in the gas flow direction when viewed from the axial direction.

  In the gas flow direction, a merging portion 60 constituting a part of the introduction flow path 62 is formed at the downstream end 56B of the scroll flow path 56. In this merging portion 60, the exhaust gas that has flowed from the downstream end 56 </ b> B of the scroll flow path 56 to the introduction flow path 62 and the exhaust gas that is guided by the introduction flow path 62 from the exhaust passage 12 to the upstream end 56 </ b> A of the scroll flow path 56. This is the area where we meet.

  A cross section (hereinafter referred to as “second flow path cross section 82”) at a site where the downstream end 56 </ b> B of the scroll flow channel 56 is connected in the introduction flow channel 62 (a site where the introduction flow channel 62 is in contact with the tongue 66). Details will be described later.

  As shown in FIG. 2, the speed increasing flow path 64 is formed so as to surround the turbine rotor 22 when viewed from the axial direction. The speed increasing flow path 64 allows exhaust gas flowing in a part of the introduction flow path 62 and the scroll flow path 56 to flow into the turbine rotor 22 from the base end edge 26 </ b> C of the turbine blade 26.

  The axial width of the speed increasing flow path 64 is narrower than the diameter of the scroll flow path 56, as shown in FIG.

  As shown in FIG. 3, the discharge flow path 58 is formed on the outer side in the axial direction with respect to the turbine rotor 22, so that the exhaust gas flowing out from the leading edge 26 </ b> A of the turbine blade 26 flows toward the exhaust passage 12. It has become. Further, as viewed from the axial direction, the flow passage cross section of the discharge flow passage 58 is made larger than the circle drawn by the tip edge 26 </ b> A of the turbine blade 26 by rotating the turbine rotor 22.

  Hereinafter, the position of the second flow path section 82 of the introduction flow path 62, the cross sectional shape of the second flow path cross section 82, the position of the first flow path cross section 80 of the scroll flow path 56, the cross sectional shape of the first flow path cross section 80, and the like. Will be described.

  First, the position of the second channel cross section 82 of the introduction channel 62 will be described. As shown in FIG. 1, the second channel cross section 82 is a channel cross section at a site where the downstream end 56 </ b> B of the scroll channel 56 is connected in the introduction channel 62.

  In order to obtain the second flow path section 82, the cut surface 70 that cuts the introduction flow path 62 has an R stop 66 </ b> A (arc end) on the introduction flow path 62 side of the arcuate tongue 66 as viewed from the axial direction. The plane is parallel to the rotation center line C1 of the turbine rotor 22. Further, the flow area of the introduction flow path 62 when the introduction flow path 62 is cut at the cut surface 70 is the flow of the introduction flow path 62 when the introduction flow path 62 is cut at another face that satisfies the above-described conditions. The cut surface 70 is determined so as to be the smallest as compared with the road area.

  The channel area of the second channel section 82 is S2 (hereinafter “channel area S2”), and the centroid of the channel of the second channel section 82 is G2 (hereinafter “centroid G2”). And

  Next, the position of the first flow path cross section 80 of the scroll flow path 56 will be described. As described above, the first channel cross section 80 is a channel cross section at the upstream end 56 </ b> A of the scroll channel 56.

  In order to obtain the first flow path cross section 80, the cut surface 72 that cuts the first flow path cross section 80 at the upstream end 56A is parallel to the cut surface 70 for obtaining the second flow path cross section 82 and of the turbine rotor 22. It is a plane passing through the rotation center line C1. In other words, the position where the cut surface 72 and the scroll channel 56 intersect is the upstream end 56 </ b> A of the scroll channel 56.

  The channel area of the first channel section 80 is S1 (hereinafter “channel area S1”), and the centroid of the channel of the first channel section 80 is G1 (hereinafter “centroid G1”). .

  In the present embodiment, the flow passage area S1 of the first flow passage cross section 80 at the upstream end 56A of the scroll flow passage 56 and the second portion at the portion of the introduction flow passage 62 where the downstream end 56B of the scroll flow passage 56 is connected. The channel area S2 of the channel cross section 82 is made equal. Here, “equivalent” means that the channel cross section S2 is in the range of 1 to 1.1 when the channel cross section S1 is 1.

  Furthermore, as viewed from the axial direction, a straight line that is orthogonal to a straight line L1 passing through the centroid G1 of the first flow path cross section 80 and the rotation center line C1 of the turbine rotor 22 and that passes through the rotation center line C1 is a reference straight line L2. And The distance D2 from the reference straight line L2 to the centroid G2 of the second flow path section 82 is the same or shorter than the distance D1 from the reference straight line L2 to the centroid G1 of the first flow path section 80.

  Further, when viewed from the axial direction, an angle K1 formed by a straight line L3 passing through the centroid G2 of the second flow path section 82 and the rotation center line C1 of the turbine rotor 22 and the straight line L1 is 10 ° or more and 45 ° or less. Has been.

(Function)
Next, the effect | action of the turbine unit 20 is demonstrated, comparing with the turbine unit 120 which concerns on a comparison form. First, the difference between the turbine unit 120 and the turbine unit 20 will be mainly described.

[Turbine unit according to comparative form]
As shown in FIG. 9, the scroll flow path 156 of the turbine unit 120 is formed in an arc shape around the turbine rotor 22 when viewed from the axial direction, and flows exhaust gas flowing into the turbine rotor 22. Yes. The cross section of the scroll channel 156 has a circular shape. Furthermore, the flow passage area of the scroll flow passage 156 gradually decreases from the upstream side to the downstream side in the gas flow direction (see the arrow in the figure). The upstream end 156A of the scroll flow path 156 in the gas flow direction and the tip of the tongue 166 described later are not separated in the circumferential direction of the turbine rotor 22 and coincide with each other.

  The position of the upstream end 156A of the scroll flow path 156, the cross section of the scroll flow path 156 at the upstream end 156A (hereinafter, “third flow path cross section 180”) and the like will be described in detail later.

  The introduction passage 162 of the turbine unit 120 is formed so that the centroid is linear between the upstream end 156A of the scroll passage 156 and the exhaust passage 12 when viewed from the axial direction. The introduction flow path 162 guides the exhaust gas from the exhaust passage 12 to the upstream end 156A of the scroll flow path 156. The cross section of the introduction flow path 162 has a circular shape. Further, the introduction channel 162 is not connected to the downstream end 156 </ b> B of the scroll channel 156.

  Further, at the downstream end 156B of the scroll flow path 156, as shown in FIG. 8, a tongue 166 that connects the wall surface forming the introduction flow path 162 and the wall surface forming the scroll flow path 156 is formed. . The tongue 166 has an arcuate shape that protrudes downstream in the exhaust gas flow direction when viewed from the axial direction.

  In the gas flow direction, a merging portion 160 constituting a part of the introduction flow path 162 is formed at the downstream end 156B of the scroll flow path 156. This merging portion 160 includes exhaust gas that has flowed from the downstream end 156B of the scroll flow path 156 to the scroll flow path 156, and exhaust gas that has flowed from the upstream end 156A of the scroll flow path 156 to the scroll flow path 156 by the introduction flow path 162. Is a region where

  Hereinafter, the position of the channel cross section (hereinafter, “fourth channel cross section 182”) at the portion where the tongue portion 166 is formed in the introduction channel 162, the cross sectional shape of the fourth channel cross section 182 and the like, and the scroll channel The position of the third channel cross section 180 at 156, the cross-sectional shape of the third channel cross section 180, and the like will be described.

  First, the position of the fourth flow path section 182 of the introduction flow path 162 will be described. In order to obtain the fourth channel cross section 182, the cutting surface 170 for cutting the introduction channel 162 is formed on the introduction channel 162 side of the arcuate tongue 166 when viewed from the axial direction as shown in FIG. 8. The surface passes through the R stop 166A (arc end) and is parallel to the rotation center line C1 of the turbine rotor 22. Furthermore, the flow area of the introduction flow path 162 when the introduction flow path 162 is cut at the cut surface 170 is equal to the flow of the introduction flow path 162 when the introduction flow path 162 is cut at another surface that satisfies the above-described conditions. The cut surface 170 is determined so as to be the smallest as compared with the road area.

  The channel area of the fourth channel section 182 is S4 (hereinafter “channel area S4”), and the centroid of the channel of the fourth channel section 182 is G4 (hereinafter “centroid G4”). And

  Next, the position of the third flow path cross section 180 of the scroll flow path 156 will be described. As described above, the third flow path cross section 180 is a flow path cross section at the upstream end 156A of the scroll flow path 156.

  In order to obtain the third flow path cross section 180, the cut surface 172 that cuts the third flow path cross section 180 at the upstream end 156A is parallel to the cut surface 170 for obtaining the fourth flow path cross section 182 and the turbine rotor. 22 is a plane passing through the rotation center line C1. In other words, the position where the cut surface 172 and the scroll channel 156 intersect is the upstream end 156 </ b> A of the scroll channel 156.

  The flow path area of the third flow path section 180 is S3 (hereinafter, “flow path area S3”), and the centroid of the third flow path cross section 180 is G3 (hereinafter, “centroid G3”). To do.

  In the turbine unit 120 according to the comparative embodiment, the flow passage area S3 of the third flow passage section 180 in the scroll flow passage 156 is larger than the flow passage area S4 of the fourth flow passage section 182 in the introduction flow passage 162. Has been.

  Furthermore, when viewed from the axial direction, a straight line that is orthogonal to a straight line L4 that passes through the centroid G3 of the third flow path section 180 and the rotation center line C1 of the turbine rotor 22 and that passes through the rotation center line C1 is a reference straight line. Let L5. Then, the distance D4 from the reference straight line L5 to the centroid G4 of the fourth flow path section 182 is made longer than the distance D3 from the reference straight line L5 to the centroid G3 of the third flow path section 180.

  Further, when viewed from the axial direction, an angle K2 formed by a straight line L6 passing through the centroid G4 of the fourth flow path section 182 and the rotation center line C1 of the turbine rotor 22 and the straight line L4 is less than 10 °. .

[Operation of turbine unit]
As shown in FIG. 2, the introduction flow path 62 of the turbine unit 20 guides the exhaust gas flowing in the exhaust passage 12 to the upstream end 56 </ b> A of the scroll flow path 56. Furthermore, the scroll flow path 56 allows the exhaust gas flowing into the scroll flow path 56 from the upstream end 56A to flow toward the downstream end 56B.

  Here, in the turbine unit 20, the exhaust gas that has flowed from the downstream end 56 </ b> B of the scroll flow path 56 to the introduction flow path 62 is merged 60, and is introduced from the exhaust passage 12 to the upstream end 56 </ b> A of the scroll flow path 56 by the introduction flow path 62. It merges with the exhaust gas that is led to.

  Further, the speed increasing flow path 64 formed so as to surround the turbine rotor 22 increases the speed of the exhaust gas flowing through a part of the introduction flow path 62 and the scroll flow path 56, and the base end edge 26 </ b> C of the turbine blade 26. Then, it flows into the turbine rotor 22 (see FIG. 3).

  On the other hand, in the turbine unit 120, as shown in FIG. 9, the exhaust gas that has flowed from the downstream end 156B of the scroll flow path 156 to the scroll flow path 156 is scrolled from the upstream end 156A by the introduction flow path 162 at the junction 160. The exhaust gas flows into the flow path 156 and merges.

  Further, the speed increasing flow path 64 formed so as to surround the turbine rotor 22 increases the speed of the exhaust gas flowing through the scroll flow path 156 and causes the exhaust gas to flow into the turbine rotor 22 from the base end edge 26 </ b> C of the turbine blade 26.

  The turbine rotor 22 is pushed and rotated by the exhaust gas flowing in from the base end edge 26C. Then, as shown in FIG. 3, the exhaust gas that has pushed the turbine rotor 22 flows out from the tip edge 26 </ b> A of the turbine blade 26, flows through the discharge passage 58, and is discharged into the exhaust passage 12.

  Next, an analysis result and an experiment result using the turbine unit 20 of the present embodiment, and an analysis result and an experiment result using the turbine unit 120 of the comparative form will be described.

  First, the analysis will be described. CFD (Computational Fluid Dynamics) analysis was performed when the turbine unit 20 was used and when the turbine unit 120 was used. Specifically, CFD analysis was performed on the total pressure of the exhaust gas flowing in the vicinity of the downstream ends 56B and 156B of the scroll flow paths 56 and 156. The reason for paying attention to this portion is that the pressure distribution may vary at the merging portions 60 and 160 where the exhaust gas merges.

  FIG. 4A shows the analysis result when the turbine unit 20 is used, and FIG. 4B shows the analysis result when the turbine unit 120 is used. By dividing the dots (patterns), the total pressure of the exhaust gas is indicated as high or low. The higher the dot density, the higher the total pressure of the exhaust gas, and the lower the dot density, the lower the total pressure of the exhaust gas.

  The part (range H2 in the figure) where the total pressure is lowest in the turbine unit 120 shown in FIG. 4B is the lowest in the turbine unit 20 shown in FIG. 4A due to the flow separation loss. This is larger than the portion (range H1 in the figure) (see FIGS. 5A and 5B). In other words, the portion of the turbine unit 20 where the total pressure is the lowest is smaller than the portion of the turbine unit 120 where the total pressure is the lowest.

  The reason for this is that in the turbine unit 20, as shown in FIG. 1, the flow passage area S 1 of the first flow passage section 80 at the upstream end 56 A of the scroll flow passage 56 and the tongue 66 are formed in the introduction flow passage 62. The flow path area S2 of the second flow path cross section 82 at the portion where the flow is performed is equivalent. On the other hand, in the turbine unit 120, as shown in FIG. 8, the flow passage area S3 of the third flow passage cross section 180 at the upstream end 156A of the scroll flow passage 156 is such that the tongue portion 166 is in the introduction flow passage 162. This is because it is made larger than the channel area S4 of the fourth channel section 182 at the formed site. Therefore, as described above, the portion where the total pressure is the lowest in the turbine unit 120 (range H2 in the figure) is larger than the portion where the total pressure is the lowest in the turbine unit 20 (range H1 in the figure). I think.

  Next, experiments will be described. The relationship between the flow rate of the exhaust gas flowing through the turbine units 20 and 120 and the turbine efficiency was determined by experiments when the turbine unit 20 was used and when the turbine unit 120 was used.

The vertical axis of the graph shown in FIG. 6 is the turbine efficiency, and the horizontal axis of the graph is the flow rate of the exhaust gas. The solid line in the graph is the experimental result when the turbine unit 20 is used, and the broken line in the graph is the experimental result when the turbine unit 120 is used. In addition, about the flow volume of exhaust gas, when using the turbine units 20 and 120, it experimented about the flow volume from the lower limit assumed to the upper limit. Also,

  As can be seen from the graph shown in FIG. 6, the turbine efficiency of the turbine unit 20 is higher than the turbine efficiency of the turbine unit 120 at all flow rates.

(Summary)
In the turbine unit 20, the flow passage area of the first flow passage section 80 of the scroll flow passage 56 and the flow passage area of the second flow passage section 82 of the introduction flow passage 62 are equal. Therefore, as can be seen from the analysis results described above, the portion of the turbine unit 20 where the total pressure is the lowest is smaller than the portion of the turbine unit 120 where the total pressure is the lowest.

  That is, when the turbine unit 20 is used, variation in the pressure distribution of the exhaust gas flowing through the flow path formed around the turbine rotor 22 is smaller than when the turbine unit 120 is used.

  Further, as can be seen from the analysis results described above, the turbine efficiency of the turbine unit 20 is higher than the turbine efficiency of the turbine unit 120 at all flow rates.

  As described above, in the turbine unit 20, compared with the case where the turbine unit 120 is used, the turbine efficiency is reduced due to the variation in the total pressure distribution of the exhaust gas flowing through the flow path formed around the turbine rotor 22. Can be suppressed.

  In the turbine unit 20, as shown in FIG. 1, the distance D2 from the reference straight line L2 to the centroid G2 of the second flow path section 82 is from the reference straight line L2 to the centroid G1 of the first flow path section 80. Compared to or shorter than the distance D1. For this reason, the exhaust gas that has passed through the upstream end 56A of the scroll flow path 56 by the introduction flow path 62 is supported on the inner peripheral side by the gas flowing in from the downstream end 56B, so that the direction from the centroid G2 toward the centroid G1 In the figure, it flows in the direction of the arrow F1, flows into the scroll flow path 56 from the upstream end 56A, hits the radially outer portion of the wall surface constituting the scroll flow path 56, and flows toward the downstream end 56B.

  On the other hand, in the turbine unit 120, as shown in FIG. 8, the distance D4 from the reference straight line L5 to the centroid G4 of the fourth flow path section 182 is the figure of the third flow path section 180 from the reference straight line L5. Longer than the distance D3 to the heart G3. For this reason, the exhaust gas guided to the scroll channel 156 by the introduction channel 162 flows in the direction of the arrow F2 in the figure so as to go from the centroid G4 to the centroid G3. As a result, in the turbine unit 120, the amount of exhaust gas that hits the radially outer portion of the wall surface that forms the scroll flow path 156 is smaller than when the turbine unit 20 is used. Further, since the gas flow does not change suddenly in the F2 direction, the gas that has passed through the downstream end 156B is drawn out to the outer peripheral side.

  In other words, in the turbine unit 20, the amount of exhaust gas that hits the radially outer portion of the wall surface that forms the scroll flow path 56 is larger than when the turbine unit 120 is used, and the downstream end 56 </ b> B. The flow of gas that passes through becomes smooth. Thereby, in the turbine unit 20, it is suppressed that the total pressure distribution of the exhaust gas which flows through the scroll flow path 56 varies compared with the case where the turbine unit 120 is used.

  As described above, in the turbine unit 20, compared with the case where the turbine unit 120 is used, the turbine efficiency is reduced due to the variation in the total pressure distribution of the exhaust gas flowing through the scroll flow path 56 formed around the turbine rotor 22. It can suppress effectively that it falls.

  Further, the introduction flow path 62 of the turbine unit 20 is formed so that the centroid is linear when viewed from the axial direction. For this reason, the pressure loss of the exhaust gas flowing through the introduction flow path 62 can be reduced as compared with the case where the introduction flow path is formed in a curved shape when viewed from the axial direction.

  Moreover, in the turbocharger 10, by providing the turbine unit 20, the turbine rotor can be efficiently rotated and compressed air can be efficiently supplied to the engine as compared with the case where the turbine unit 120 is provided.

  Although the present invention has been described in detail with respect to specific embodiments, the present invention is not limited to such embodiments, and various other embodiments can be taken within the scope of the present invention. This will be apparent to those skilled in the art. For example, in the above embodiment, the fluid that pushes the turbine rotor 22 is exhaust gas, but may be, for example, steam or water.

  In the above embodiment, the flow path area S1 of the first flow path cross section 80 of the scroll flow path 56 and the flow path area S2 of the second flow path cross section 82 of the introduction flow path 62 are equal. There may be. By making it the same, the pressure loss of the exhaust gas flowing through the introduction flow path 62 can be reduced compared to the case where they are not the same.

  Moreover, in the said embodiment, although the cross section of the scroll flow path 56 was made into circular shape, as FIG. 10 (A) (B) shows, the shape different from circular shape may be sufficient.

  When the speed increasing flow path is short (for example, the radial length of the speed increasing flow path is shorter than the width of the speed increasing flow path), the bias of the total pressure distribution is not alleviated and the turbine blade 26 In this case, when the speed increasing flow path is short, the efficiency reduction becomes remarkable. In such a case, calculation is made using the area obtained by adding the speed increasing flow path 64 on the outer peripheral side of the base end edge 26C of the turbine blade 26 in addition to the scroll as the flow path cross section S1 ′. It is desirable to set the cross-sectional area of S2 in the range of 1 to 1.1 times. The cross section for calculating the area in this case may be the same as the cross section for calculating the area of S1 described above.

DESCRIPTION OF SYMBOLS 10 Turbocharger 20 Turbine unit 22 Turbine rotor 24 Housing 30 Centrifugal compressor 32 Impeller 56 Scroll flow path 56A Upstream end 56B Downstream end 62 Introduction flow path 80 First flow path cross section 82 Second flow path cross section

Claims (3)

A turbine rotor that rotates around an axis by being pushed by fluid flowing in from a radially outer side;
A housing that accommodates the turbine rotor, wherein a fluid that flows into the turbine rotor flows, and a scroll flow path that is formed in an arc shape around the turbine rotor as viewed from an axial direction of the turbine rotor; The housing formed with an introduction flow path for introducing a fluid to the scroll flow path,
In the scroll flow path, the upstream end in the fluid flow direction and the downstream end in the flow direction are separated in the circumferential direction of the turbine rotor,
The introduction channel is connected to the downstream end of the scroll channel,
The flow passage area of the first flow passage cross section at the upstream end of the scroll flow passage and the flow passage area of the second flow passage cross section at the site where the downstream end of the scroll flow passage is connected in the introduction flow passage. Turbine unit that is equivalent.   When viewed from the axial direction, a straight line passing through the centroid of the first flow path cross section and the rotation center of the turbine rotor and passing through the rotation center is defined as a reference straight line, and The turbine unit according to claim 1, wherein a distance to the centroid of the second flow path section is equal to or shorter than a distance from the reference straight line to the centroid of the first flow path section. The turbine unit according to claim 1, wherein the turbine unit has a turbine rotor that rotates by being pushed by an exhaust gas as a fluid discharged from an engine.
A centrifugal compressor that compresses air supplied to the engine by a rotational force transmitted from the turbine rotor to an impeller;
Turbocharger with