JP2017203410A - Supercharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a supercharger capable of suppressing separation of air layers from impeller blades at a low speed without deteriorating the performance of a compressor at a high speed.SOLUTION: Between a pair of long blades 31 adjacent to each other in the circumferential direction of a hub part 30, one long blade 31 lying forward in the rotation direction of a compressor impeller 12 has an inlet side blade part extending from an impeller throat T, that is defined by the pair of long blades 31 and a shroud wall 39, to an air inlet part 15 side. The inlet side blade part has a recess 43 that is recessed radially inward of the compressor impeller 12 from an outer peripheral edge of the long blade 31 facing the shroud wall 39. The shroud wall 39 has an annular convex part 44 of a cross-sectional shape corresponding to the recess 43 at a position facing the recess 43 of the long blade 31.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a supercharger, and more particularly to a supercharger equipped with a compressor impeller.

  As a conventional turbocharger, for example, a compressor disclosed in Patent Document 1 and a turbocharger using the compressor are known. The compressor disclosed in Patent Document 1 includes a compressor housing having an air inlet portion and a compressed air outlet portion, and an impeller that is housed and arranged in the compressor housing so as to be rotatable about a rotation axis. In this compressor, the inner wall surface of the compressor housing is smoothly bulged. The clearance between the inner wall surface of the compressor housing and the radial edge of the impeller blades facing the inner wall surface is such that the end region on the air inlet side and the end on the air outlet side of the blade in the radial direction edge. It is the minimum at the intermediate position between the partial areas.

  According to the compressor disclosed in Patent Document 1, the amount of air passing through the clearance region, that is, the loss is reduced, and the compressor efficiency can be improved while avoiding contact between the impeller and the housing rotating at high speed.

JP 2010-275950 A

  However, although the compressor disclosed in Patent Document 1 reduces the loss by reducing the amount of air passing through the clearance region, it does not solve the problem of stalling due to separation of the air layer from the impeller at low speed. The stall due to the separation of the air layer from the impeller is one of the factors that cause a surge and reduce the performance of the compressor. As shown in FIG. 7, for example, when the absolute velocity of the air flowing into the compressor impeller 61 having the impeller blades 62 is C and the peripheral speed U of the compressor impeller 61 is, the relative velocity of the air flowing into the compressor impeller 61 is W It is. The separation of the air layer from the compressor impeller 61 at low speed occurs when the angle of attack α formed by the center line (camber line) L of the impeller blades 62 and the inflow relative velocity W of the air flowing toward the compressor impeller 61 increases. It is known to occur. The reason is that at low speed, the air flow rate is small with respect to the cross-sectional area of the flow path near the leading edge of the impeller blade 62, and the absolute speed C decreases, so that the elevation angle α increases. Therefore, if a compressor impeller provided with an impeller blade that reduces the angle of attack α at low speeds or a compressor impeller with a reduced inlet diameter of the compressor impeller, air flow separation at low speeds can be prevented. However, these measures are forced to reduce the cross-sectional area of the impeller throat in the compressor impeller (the area where the cross-sectional area is the smallest in the air flow path between the impeller blades), and the ability of the compressor at high speed is reduced. Cause problems.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to suppress separation of the air layer from the impeller blades at low speed without reducing the capacity of the compressor at high speed. The provision of turbochargers.

  In order to solve the above problems, the present invention provides a compressor housing having an air inlet portion and an air outlet portion, a compressor impeller rotatable in the compressor housing, the compressor impeller provided in the compressor housing, A plurality of first impeller blades that are provided in a circumferential direction of the hub portion and extend from the air inlet portion toward the air outlet portion. One of the pair of first impeller blades that are adjacent to each other in the circumferential direction of the hub portion in the rotation direction of the compressor impeller, and the first impeller blade and the shroud of the pair of first impeller blades An inlet side wing extending from an impeller throat section partitioned by a wall to the air inlet section side, and the inlet The blade portion has a concave portion recessed inward in the radial direction of the compressor impeller from an outer peripheral edge facing the shroud wall of the first impeller blade, and the shroud wall is located at a position facing the concave portion of the first impeller blade. And having an annular convex portion having a cross-sectional shape corresponding to the concave portion.

  According to the present invention, by providing the concave portion of the inlet side blade portion of the compressor impeller and the convex portion of the shroud wall, the cross-sectional area of the channel at the concave portion and the convex portion becomes smaller than the cross-sectional area of the flow channel at the air inlet portion. Although the flow rate of the air passing through the compressor impeller at low speed does not change, the reduction of the flow path cross-sectional area increases the speed of the air passing through the concave portion and the convex portion, and the separation of the air layer at the inlet side wing portion is suppressed. As a result, it is possible to suppress separation of the air layer from the impeller blades at low speed without reducing the capacity of the compressor at the high speed of the supercharger.

In the supercharger, the concave portion may be an arc-shaped concave portion, and the convex portion may be a convex portion that protrudes in a circular arc shape following the arc-shaped concave portion.
In this case, the air passing through the compressor impeller can smoothly pass through the concave portion and the convex portion.

In the supercharger, a ratio of a recess amount of the concave portion to an inlet clearance between the compressor impeller and the shroud wall at the air inlet portion may be greater than 0 and smaller than 3.
In this case, separation of the air layer at the inlet side wing of the compressor impeller can be further suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, the supercharger which can suppress the peeling from the impeller blade | wing of an air layer at the time of low speed can be provided, without reducing the capability of the compressor at the time of high speed.

It is the schematic which shows schematic structure of the turbocharger which concerns on embodiment of this invention. It is a longitudinal cross-sectional view which shows the compressor in the turbocharger which concerns on this embodiment. It is a side view of the compressor impeller concerning this embodiment. It is explanatory drawing which expand | deploys and shows typically the long blade and short blade of the compressor impeller which concerns on this embodiment. It is a longitudinal cross-sectional view which expands and shows the principal part of the compressor impeller of this embodiment. (A) is the principal part enlarged view of the turbocharger which concerns on the modification 1, (b) is the principal part enlarged view of the turbocharger which concerns on the modification 2, (c) is the turbocharger which concerns on the modification 3 It is a principal part enlarged view. It is explanatory drawing which expand | deploys typically and shows the impeller blade | wing of the conventional compressor impeller.

  Hereinafter, a turbocharger as a supercharger according to an embodiment of the present invention will be described with reference to the drawings. The turbocharger of the present embodiment is an in-vehicle turbocharger. As shown in FIG. 1, the turbocharger 10 includes a compressor housing 11 and a compressor impeller 12 that can rotate within the compressor housing 11. The compressor housing 11 has an air inlet portion 15 and an air outlet portion 16. The air inlet portion 15 is an air inlet that takes in air at atmospheric pressure passing through a pipe 17 connected to the compressor housing 11. The air outlet portion 16 is an outlet for air compressed by the compressor impeller 12. The compressed air is supplied to the engine as combustion air through a pipe 18 connected to the air outlet 16. In FIG. 1, white arrows indicate the flow of air.

  The compressor impeller 12 is connected to one end of the rotary shaft 19. A turbine 20 is connected to the other end of the rotating shaft 19. The turbine 20 is rotatably accommodated in a turbine housing 21. A bearing housing 22 is provided between the compressor housing 11 and the turbine housing 21. The rotating shaft 19 is rotatably supported by a bearing portion 23 constituted by a thrust bearing or a radial bearing.

  The turbine housing 21 has an exhaust gas inlet portion 24 and an exhaust gas outlet portion 25. The exhaust gas inlet 24 is an exhaust gas inlet through which high-temperature exhaust gas discharged from the engine flows into the turbine housing 21 at high speed. Hot exhaust gas discharged from the engine passes through a pipe 26 connected to the turbine housing 21. The exhaust gas outlet 25 is an exhaust gas outlet after the turbine 20 is rotated in the turbine housing 21. The exhaust gas after rotating the turbine 20 passes through a pipe 27 connected to the turbine housing 21 and is discharged to a muffler (not shown). In FIG. 1, black arrows indicate the flow of exhaust gas.

  As shown in FIG. 2, the compressor impeller 12 includes a substantially truncated cone-shaped hub portion 30. The outer diameter of the hub portion 30 is constant from the air inlet 15 side toward the bearing housing 22 in the axial center P direction, and increases as the bearing housing 22 is approached from the predetermined position. As shown in FIG. 3, the hub portion 30 includes a plurality of impeller blades provided in the circumferential direction. The impeller blade of the present embodiment includes a plurality of long blades 31 extending from the air inlet portion 15 to the air outlet portion 16 and a plurality of short blades 32 having a shorter extension length than the long blade 31. The long blades 31 and the short blades 32 are alternately arranged in the circumferential direction. The long blades 31 and the short blades 32 are formed in a three-dimensionally curved plate shape. The long blade 31 corresponds to a first impeller blade, and the short blade 32 corresponds to a second impeller blade.

  The long blade 31 has a leading edge (leading edge) 33 facing the air inlet portion 15 and a trailing edge (trading edge) 34 facing the air outlet portion 16. The long blade 31 has an outer peripheral edge (impeller shroud line) 35 that connects the leading edge 33 and the trailing edge 34 and is drawn as a curved line. The front edge 33 side of the outer peripheral edge 35 is substantially straight and reaches the rear edge 34 so as to draw an arc toward the rear edge 34. The rear edge 34 of the long blade 31 is located on the outer peripheral edge of the hub portion 30 in the radial direction.

  The short blade 32 has a leading edge (leading edge) 36 facing the air inlet portion 15 and a trailing edge (trading edge) 37 facing the air outlet portion 16. The short blade 32 has an outer peripheral edge (impeller shroud line) 38 that connects the leading edge 36 and the trailing edge 37 and is drawn as a curved line. The leading edge 36 of the short blade 32 is located farther from the air inlet portion 15 than the leading edge 33 of the long blade 31 in the direction of the axis P of the rotating shaft 19. The trailing edge 37 of the short blade 32 is located on the outer peripheral edge of the hub portion 30 in the radial direction. Accordingly, the length of the outer peripheral edge 38 of the short blade 32 is shorter than the length of the outer peripheral edge 35 of the long blade 31. The outer peripheral edge 38 reaches the rear edge 37 so as to draw an arc from the front edge 36.

In FIG. 3, the minimum outer peripheral diameter D1h on the air inlet portion 15 side in the hub portion 30 is set, and the inner peripheral diameter D1s of the compressor housing 11 in the air inlet portion 15 is set. Further, the maximum outer peripheral diameter D2 of the hub portion 30 on the air outlet portion 16 side is set. The channel cross-sectional area A in the vicinity of the leading edge 36 of the long blade 31 is obtained from Equation 1 based on the inner peripheral diameter D1s and the minimum outer peripheral diameter D1h. π is the circumference ratio.

A = π · (D1s / 2−D1h / 2) ² (Formula 1)

  On the air inlet 15 side of the compressor impeller 12, the long blades 31 are adjacent to each other in the circumferential direction of the hub 30. As shown in FIG. 3, the impeller throat portion T is defined by the compressor housing 11 and a pair of adjacent long blades 31. The impeller throat portion T indicates a region where the cross-sectional area of the air flow path between the long blades 31 is rapidly reduced. The impeller throat portion T exists in the circumferential direction of the compressor impeller 12 according to the number of long blades 31. In the present embodiment, the outer diameter of the hub portion 30 in the impeller throat portion T is equal to the outer diameter (D1h) of the hub portion 30 on the air inlet portion 15 side. The outer peripheral diameter of the hub portion 30 increases from the impeller throat portion T toward the bearing housing 22 in the axial center P direction (see FIG. 2).

  As shown in FIG. 2, the compressor housing 11 includes a shroud wall 39 that faces the outer peripheral edge 35 of the long blade 31 and the outer peripheral edge 38 of the short blade 32. The shroud wall 39 is formed so as to follow the outer peripheral edges 35 and 38. Therefore, the impeller throat portion T is partitioned by the pair of long blades 31 and the shroud wall 39. An inlet clearance CL is set between the compressor impeller 12 and the shroud wall 39 in the air inlet portion 15.

  FIG. 4 is a diagram schematically showing the long blade 31, the short blade 32, and the impeller throat portion T. In FIG. 4, the absolute speed of the air flowing into the compressor impeller 12 is C, and the peripheral speed of the compressor impeller 12 is U. The relative velocity of the air flowing into the long blade 31 is the inflow relative velocity W. The angle formed by the center line (camber line) L and the inflow relative velocity W at the leading edge 33 of the long blade 31 is the angle of attack α. The angle formed by the axis P and the center line L is the blade angle β. In FIG. 4, the impeller throat portion T is indicated by a one-dot chain line.

  In FIG. 4, of the pair of long blades 31 that define the impeller throat portion T, one long blade 31 is a long blade 31A, and the other long blade 31 is a long blade 31B. In this case, the impeller throat portion T is defined based on the leading edge 33 of the other long blade 31B. The long blade 31A is located in front of the long blade 31B in the rotation direction of the compressor impeller 12. That is, the long blade 31A is positioned in front of the impeller throat portion T in the rotation direction of the compressor impeller 12. The long blade 31A has an inlet side wing portion 41 extending from the impeller throat portion T toward the air inlet portion 15 and an outlet side wing portion 42 extending from the impeller throat portion T toward the air outlet portion 16 side. The other long blade 31 </ b> B is located behind the impeller throat portion T in the rotational direction of the compressor impeller 12.

  When the long blade 31B shown in FIG. 4 is viewed as the long blade 31 forward in the rotation direction, the impeller throat portion T exists between the long blade 31B and the long blade 31C behind the rotation direction. Therefore, when viewed from the impeller throat portion T between the long blade 31B and the long blade 31C, the long blade 31B corresponds to one long blade, and the long blade 31C corresponds to the other long blade. That is, the long blade 31 in the rotation direction forward with respect to the impeller throat portion T corresponds to one long blade, and the long blade 31 in the rotation direction rearward of the impeller throat portion T corresponds to the other long blade. In this case, the impeller throat portion T is defined based on the leading edge 33 of the other long blade 31C.

In the present embodiment, an arcuate recess 43 is formed in the inlet wing 41 of one long blade 31B so that a part of the outer peripheral edge 35 is recessed radially inward. The recess 43 is provided to suppress separation of the air layer at a low speed in the inlet side wing 41. Incidentally, the inlet-side wing portion 41 of the long blade 31A is the portion where the air layer is most likely to peel off at the low speed in the long blade 31A. Concave portions 43 are formed in all the long blades 31 of the compressor impeller 12. As shown in FIG. 5, the distance from the outer peripheral edge 35 that defines the inlet clearance CL of the front edge 33 to the deepest point in the radial direction of the recess 43 is defined as the recess amount Q. In the present embodiment, the relationship between the dent amount Q and the inlet clearance CL is set to satisfy Equation 2.

0 <Q / CL <3 (Formula 2)

  On the other hand, the shroud wall 39 is formed with an annular convex portion 44 having a cross-sectional shape corresponding to the concave portion 43 at a position facing the concave portion 43 of the long blade 31. The convex portion 44 is formed in the circumferential direction near the air inlet portion 15 of the shroud wall 39. The distance from the shroud wall 39 to the most protruding point in the radial direction of the convex portion 44 is defined as a protruding amount R. In this embodiment, the dent amount Q and the protrusion amount R are equal (Q = R). Therefore, the clearance between the outer peripheral edge 35 in the concave portion 43 and the convex portion 44 in the shroud wall 39 is constant. In addition, since the convex part 44 is provided in the shroud wall 39, if the compressor housing 11 is divided into two along the axis P, for example, the compressor housing 11 can be assembled.

When the channel cross-sectional area at the position corresponding to the concave portion 43 and the convex portion 44 is At, the channel cross-sectional area At is obtained by Equation 3. π is the circumference ratio.

At = π · {(D1s / 2−Q) −D1h / 2} ² (Formula 3)

Therefore, the channel cross-sectional area At is smaller than the channel cross-sectional area A in the vicinity of the leading edge 36 of the long blade 31.

Next, the operation of the turbocharger 10 of this embodiment will be described. When the turbocharger 10 is rotated at a constant rotational speed, air is taken into the compressor impeller 12. At this time, the flow rate of air passing through the compressor impeller 12 is constant. Assuming that the air flow rate is Ga, the air flow rate Ga is obtained by Equation 4. ρ is the density of air.

Ga = ρ · C · A (Formula 4)

It is known that the air flow rate Ga is proportional to the flow path cross-sectional area A and the absolute velocity C of air. Looking at the air flow passing between the pair of long blades 31, the blade surface of the inlet side wing portion 41 of one long blade 31 has a lower pressure than the blade surface of the other long blade 31 on the air inlet portion 15 side. Become. When the air flow rate Ga is constant and the absolute velocity C of air decreases, the angle of attack α increases and air layer separation is likely to occur at the inlet side wing portion 41.

  In the present embodiment, by providing the concave portion 43 and the convex portion 44, the flow passage cross-sectional area At in the middle of the air flow passage in the compressor impeller 12 is smaller than the flow passage cross-sectional area A. For this reason, when the flow rate of air passing through the compressor impeller 12 is constant, the absolute velocity C of the air passing through the inlet side blade 41 corresponding to the recess 43 in the compressor impeller 12 increases. Since the elevation angle α decreases due to the acceleration of the air passing through the inlet side wing part 41, separation of the air layer at the low speed at the inlet side wing part 41 is suppressed. The air that has passed through the inlet side wing part 41 passes through the impeller throat part T, passes through the outlet side wing part 42, and is ejected from the air outlet part 16.

  In the relationship between the dent amount Q and the inlet clearance CL, it is preferable to satisfy Expression 2. In this case, the air layer is reliably separated from the inlet side wing portion 41 at the low speed without lowering the compressor capacity at the high speed. It is suppressed and the impeller efficiency is improved.

According to the turbocharger 10 of the present embodiment, the following operational effects are achieved.
(1) By providing in the recessed part 43 of the inlet side blade | wing part 41 of the compressor impeller 12, and the convex part 44 of the shroud wall 39, the flow-path cross-sectional area At in the recessed part 43 and the convex part 44 is the flow-path cross-sectional area A in the air inlet part 15. Smaller than Although the flow rate of the air passing through the compressor impeller 12 does not change, the speed of the air passing through the concave portion 43 and the convex portion 44 is increased due to the decrease in the cross-sectional area of the flow path, and the separation of the air layer at the inlet side wing portion 41 is suppressed. The As a result, separation of the air layer from the long blades 31 at the low speed can be suppressed without reducing the performance of the turbocharger 10 at the high speed.

(2) Since the concave portion 43 is an arc-shaped concave portion and the convex portion 44 is a convex portion that protrudes in a circular arc shape following the circular arc-shaped concave portion 43, the air passing through the compressor impeller 12 is the concave portion 43 and the convex portion. 44 can pass smoothly.

(3) The ratio of the recess 43 to the recess clearance 43 with respect to the inlet clearance CL between the compressor impeller 12 and the shroud wall 39 at the air inlet 15 is greater than 0 and less than 3. Separation of the air layer at the inlet side wing 41 of the compressor impeller 12 can be further suppressed.

(Modification Examples 1 to 3)
Next, the turbocharger according to the first to third modifications will be described. In the turbocharger according to the first modification shown in FIG. 6A, the cross section is the concave portion 51 having an arc shape, but the curvature of the concave portion 51 is set so that the curvature decreases as the distance from the front edge 33 increases. Further, the convex portion 52 projects inward in the radial direction following the concave portion 51. The curvature of the convex portion 52 decreases as the distance from the air inlet portion 15 increases. Therefore, the speed of the air passing through the flow path corresponding to the side closer to the front edge 33 of the concave portion 51 and the convex portion 52 increases. In addition, you may set so that a curvature may become large as the curvature of the recessed part 51 goes away from the front edge 33. FIG.

  In the turbocharger shown in FIG. 6B, the cross section of the recess 53 is formed in an arc shape, but is not formed immediately from the front edge 33 but is formed from a position away from the front edge 33. The convex portion 54 projects inward in the radial direction following the concave portion 53. Therefore, the speed of the air passing through the flow path corresponding to the concave portion 53 and the convex portion 54 is increased.

  In the turbocharger shown in FIG. 6C, the recess 55 has a cross section formed by a combination of a plurality of straight lines instead of an arc. The convex portion 56 projects inward in the radial direction following the concave portion 55. The speed of the air passing through the flow path corresponding to the concave portion 55 and the convex portion 56 increases. Note that the concave portions 51, 53, and 55 and the convex portions 52, 54, and 56 shown in FIGS. 6A to 6C are exaggerated.

  The above embodiment shows an embodiment of the present invention, and the present invention is not limited to the above embodiment, and various modifications can be made within the scope of the invention as described below. Is possible.

In the above embodiment (including the modified example), the compressor impeller provided with two types of blades (long blade and short blade) is exemplified, but the present invention is not limited to this. For example, a compressor having only long blades without short blades may be used.
In the above embodiment (including the modified example), the impeller throat portion is present between the adjacent long blades. For example, the present invention can be applied even when a short blade slightly shorter than the long blade is provided and an impeller throat portion exists between the long blade and the short blade.
In the above embodiment (including the modified example), the concave portion is formed in a part of the inlet side wing portion that extends from the impeller throat portion to the air inlet portion side, but this is not restrictive. For example, a recess may be formed over the inlet side wing, and the axial length of the recess can be changed according to various conditions.
In the above-described embodiment (including the modified example), the ratio (Q / CL) of the recess depression Q to the inlet clearance CL between the compressor impeller and the shroud wall at the air inlet is larger than 0 as a preferable condition. It is said that it is smaller, but this is not the case. The ratio (Q / CL) of the depression amount Q to the inlet clearance CL may be 3 or more depending on various conditions of the compressor impeller.

DESCRIPTION OF SYMBOLS 10 Turbocharger 11 Compressor housing 12 Compressor impeller 15 Air inlet part 16 Air outlet part 19 Rotating shaft 30 Hub part 31 Long blade 32 Short blade 33 Front edge 35 Outer edge 39 Shroud wall 41 Inlet side blade part 42 Outlet side blade part 43, 51, 53, 55 Recess 44, 52, 54, 56 Protrusion A, At Channel cross-sectional area CL Inlet clearance Q Depression amount R Protrusion amount T Impeller throat portion W Air inflow relative speed U Impeller peripheral speed C Air absolute speed α Angle of attack β Wing angle

Claims (3)

A compressor housing with an air inlet and an air outlet;
A compressor impeller rotatable in the compressor housing;
A shroud wall provided on the compressor housing and facing the compressor impeller,
The compressor impeller is
A hub,
A plurality of first impeller blades provided in a circumferential direction of the hub portion and extending from the air inlet portion toward the air outlet portion,
One of the pair of first impeller blades adjacent to each other in the circumferential direction of the hub portion is positioned in front of the compressor impeller in the rotation direction, and is partitioned by the pair of first impeller blades and a shroud wall. An inlet wing extending from the impeller throat part to the air inlet part side,
The inlet side wing portion has a concave portion that is recessed inward in the radial direction of the compressor impeller from an outer peripheral edge facing the shroud wall of the first impeller blade.
The supercharger, wherein the shroud wall has an annular convex portion having a cross-sectional shape corresponding to the concave portion at a position facing the concave portion of the first impeller blade.   The supercharger according to claim 1, wherein the concave portion is an arc-shaped concave portion, and the convex portion is a convex portion that protrudes in a circular arc shape following the arc-shaped concave portion.   3. The supercharger according to claim 1, wherein a ratio of a recess amount of the concave portion to an inlet clearance between the compressor impeller and the shroud wall at the air inlet portion is larger than 0 and smaller than 3. 3.

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