JP2018141405A - Centrifugal compressor and exhaust turbine super charger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrict increase in adverse pressure gradient in the vicinity of a tongue part of a scroll passage.SOLUTION: A centrifugal compressor comprises: an annular bleed groove 36a that is a space formed in an annular shape outside of an air supply passage in a hosing and that is opened to the air supply passage on the impeller side; a recirculation passage 15Bf having an annular recirculation groove 36b opened to the air supply passage on the air intake side; and a plurality of struts 36c extending along an axial direction so as to partition the space inside the recirculation passage 15Bf in a circular direction. At an angular position (30deg) about the rotation axis of the tongue part from which an exhaust passage branches from the scroll passage, the cross sectional area of the space partitioned by the struts 36c decreases from the bleed groove 36a toward the recirculation groove 36b.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a centrifugal compressor and an exhaust turbine supercharger.

  For example, centrifugal compressors for turbochargers for power generation and marine engines are required to have a wide operating range in a high pressure ratio region as engine output increases in recent years. As one of devices for expanding the working range, a casing treatment that provides a circulation channel is known (see, for example, Patent Document 1). The circulation channel can suppress the stall of the impeller by recirculating air in an operation state with a small flow rate, and can expand the operation range. Such an improvement in the shape improves the effect of expanding the operating range. Patent Document 1 discloses a configuration in which the width of the extraction groove (suction ring groove) of the recirculation path is changed in the circumferential direction as a non-axisymmetric casing treatment.

Japanese Patent No. 5430684

  A general casing treatment often has a configuration in which a circulation channel is provided in an axisymmetric shape in the circumferential direction. However, since the scroll passage of the casing is configured to be non-axisymmetric with respect to the rotating shaft of the impeller, the flow is distorted due to the non-axisymmetric nature of the scroll passage at a small flow rate outside the design range, and the scroll tongue portion Although the reverse pressure gradient in the vicinity increases, in the casing treatment provided with the axisymmetric circulation channel in the circumferential direction, the pressure gradient distortion as described above is not considered. When the conventional casing treatment is applied, the impeller pressure ratio increases and stalling is suppressed, but the radial dynamic pressure at the impeller outlet decreases, so the vicinity of the tongue where the reverse pressure gradient becomes steep as described above However, local stall and backflow are likely to occur, and as a result, there is a risk that the effect of expanding the operating range cannot be obtained.

  The present invention solves the above-described problems, and an object of the present invention is to provide a centrifugal compressor and an exhaust turbine supercharger that can suppress local stall and backflow in the vicinity of the tongue portion of the scroll passage. .

  A centrifugal compressor according to an aspect of the present invention includes a rotary shaft, an impeller attached to the rotary shaft and having a plurality of blades radially, and an air intake provided along an axial direction in which the rotary shaft extends. An air supply passage extending from the inlet to the impeller, a compression passage formed in an annular shape along the outer periphery of the impeller, a spiral scroll passage communicating with the outer periphery of the compression passage, and a part of the scroll passage A housing having an exhaust passage branching in a tangential direction from the housing and housing the rotating shaft and the impeller, and a space formed in an annular shape outside the air supply passage in the housing, and the supply air on the impeller side. A recirculation passage having an annular bleed groove that opens to the air passage and an annular recirculation groove that opens to the air supply passage on the air intake side, and a space inside the recirculation passage is circular A plurality of struts extending along the axial direction so as to partition in the direction, and at an angular position around the rotation axis of the tongue portion where the exhaust passage branches from the scroll passage, The cross-sectional area of the space partitioned by the struts is formed to decrease from the bleed groove toward the recirculation groove.

  In the centrifugal compressor according to one aspect of the present invention, the radial width in the space formed by reducing the cross-sectional area from the bleed groove toward the recirculation groove has a radial width from the bleed groove to the recirculation groove. It is preferable that it is formed by shrinking toward it.

  In the centrifugal compressor according to one aspect of the present invention, a part of the groove width of the bleed groove is narrowly formed in a space formed by reducing the cross-sectional area from the bleed groove toward the recirculation groove. Preferably it is.

  In the centrifugal compressor according to one aspect of the present invention, a shutter that opens and closes a part of the groove width of the bleed groove in a space formed by reducing the cross-sectional area from the bleed groove toward the recirculation groove; And an operating mechanism that closes the shutter when the pressure increases based on the pressure in the exhaust passage and opens the shutter when the pressure decreases.

  The exhaust turbine supercharger which concerns on 1 aspect of this invention has the centrifugal compressor as described in any one mentioned above.

  In a general casing treatment, a part of the compressed air pressurized by the impeller is extracted from the extraction groove to the recirculation passage and is returned from the recirculation groove to the supply passage to be recirculated. Therefore, the operating range of the compressor can be expanded by increasing the operating flow rate by recirculation at a small flow rate with a small intake air flow rate to suppress stall and increasing the pressure ratio of the impeller. In addition to the above effects, according to the centrifugal compressor of the present invention, the cross-sectional area of the space of the recirculation passage partitioned by the struts at the angular position centered on the rotation axis of the tongue portion where the exhaust passage branches from the scroll passage. It is formed to decrease from the bleed groove toward the recirculation groove. For this reason, the air recirculated in the recirculation passage is collected at the angular position of the tongue, resulting in a large flow rate, and the air compressed by the impeller and discharged into the scroll passage has an increased flow rate at the position of the tongue. Increases the dynamic pressure. As a result, local stall and backflow in the vicinity of the tongue portion of the scroll passage can be suppressed. Moreover, according to the present invention, since the circumferential distribution of the air flow that is recirculated and discharged is changed not by the extraction flow but by the area distribution of the recirculation passage, the flow extracted by the impeller is changed in the circumferential direction. The bleed flow rate is extremely increased at a specific circumferential position, and the radial dynamic pressure at the impeller outlet at the position can be suppressed from becoming excessively small. As a result, according to the exhaust turbine supercharger of the present invention, in the centrifugal compressor, it is possible to suppress local stall and backflow near the tongue of the scroll passage while expanding the stall limit of the impeller. The operating range can be expanded compared to typical casing treatments.

FIG. 1 is an overall configuration diagram of an exhaust turbine supercharger to which a centrifugal compressor according to an embodiment of the present invention is applied. FIG. 2 is a cross-sectional view of the centrifugal compressor of the exhaust turbine supercharger to which the centrifugal compressor according to the embodiment of the present invention is applied. FIG. 3 is an axial cross-sectional view of the centrifugal compressor according to the embodiment of the present invention. FIG. 4 is a developed sectional view in the circumferential direction of the centrifugal compressor according to the embodiment of the present invention. FIG. 5 is a view showing a flow rate distribution of the centrifugal compressor according to the embodiment of the present invention. FIG. 6 is an axial cross-sectional view of another example of the centrifugal compressor according to the embodiment of the present invention. FIG. 7 is a developed sectional view in the circumferential direction of another example of the centrifugal compressor according to the embodiment of the present invention. FIG. 8 is a circumferential cross-sectional development view of another example of the centrifugal compressor according to the embodiment of the present invention. FIG. 9 is an axial cross-sectional view of another example of the centrifugal compressor according to the embodiment of the present invention.

  Embodiments according to the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. In addition, constituent elements in the following embodiments include those that can be easily replaced by those skilled in the art or those that are substantially the same.

  FIG. 1 is an overall configuration diagram of an exhaust turbine supercharger to which a centrifugal compressor according to this embodiment is applied. FIG. 2 is a cross-sectional view of a centrifugal compressor of an exhaust turbine supercharger to which the centrifugal compressor according to this embodiment is applied. FIG. 3 is an axial cross-sectional view of the centrifugal compressor according to the present embodiment. FIG. 4 is a circumferential sectional development view of the centrifugal compressor according to the present embodiment. FIG. 5 is a view showing a flow rate distribution of the centrifugal compressor according to the embodiment of the present invention.

  An exhaust turbine supercharger 11 shown in FIG. 1 mainly includes a turbine 12, a compressor (centrifugal compressor) 13, and a rotary shaft 14, which are accommodated in a housing 15.

  The housing 15 is hollow and has a turbine housing 15A that forms a first space S1 that houses the configuration of the turbine 12, a compressor housing 15B that forms a second space S2 that houses the configuration of the compressor 13, and a rotation And a bearing housing 15 </ b> C that forms a third space S <b> 3 that accommodates the shaft 14. The third space S3 of the bearing housing 15C is located between the first space S1 of the turbine housing 15A and the second space S2 of the compressor housing 15B.

  The rotating shaft 14 is rotatably supported at its end on the turbine 12 side by a journal bearing 21 that is a turbine side bearing, and is rotatably supported at its end on the compressor 13 side by a journal bearing 22 that is a compressor side bearing. The thrust bearing 23 restricts movement in the axial direction in which the rotating shaft 14 extends. A center line C of rotation of the rotary shaft 14 is indicated by a one-dot chain line in the drawing. The rotating shaft 14 has a turbine wheel 24 of the turbine 12 fixed to one end in the axial direction. In the turbine wheel 24, a plurality of turbine blades 25 having an axial flow type are provided on the outer peripheral portion at intervals in the circumferential direction (a direction around the rotation shaft 14 around the center line C). The turbine wheel 24 is accommodated in the first space S <b> 1 of the turbine housing 15 </ b> A in the housing 15. Furthermore, the impeller 31 of the compressor 13 is being fixed to the rotating shaft 14 at the other end part in the axial direction. The impeller 31 is provided with a plurality of blades 32 radially spaced from the center line C of the rotating shaft 14 in the circumferential direction. The impeller 31 is accommodated in the second space S2 of the compressor housing 15B in the housing 15.

  Further, the turbine housing 15 </ b> A is provided with an exhaust gas intake port 26 that takes in the exhaust gas to the turbine wheel 24 and an exhaust gas discharge port 27 that discharges the exhaust gas. In the turbine housing 15A, a turbine nozzle 28 is provided between the exhaust gas intake 26 and the turbine wheel 24, and the axial exhaust gas flow statically expanded by the turbine nozzle 28 has a plurality of turbines. The turbine 12 can be driven and rotated by being guided to the turbine blades 25 of the wheel 24.

  Further, the compressor housing 15B is provided with an air intake port 33 for taking in the compression gas to the impeller 31 and a compressed air discharge port 34 for discharging the compressed air. In the compressor housing 15 </ b> B, a diffuser 35 is provided between the impeller 31 and the compressed air discharge port 34. The air compressed by the impeller 31 is discharged through the diffuser 35.

  In the compressor housing 15 </ b> B, the air intake port 33 is formed at an end portion of an air supply passage 15 </ b> Ba provided along the axial direction in which the rotation shaft 14 extends. The air supply passage 15Ba is provided from the air intake port 33 to the impeller 31. Further, the compressor housing 15B is provided with a compression passage 15Bb formed in an annular shape along the outer peripheral portion of the impeller 31 while communicating with the air supply passage 15Ba. Further, in the compressor housing 15B, as shown in FIGS. 1 and 2, a scroll passage formed in a spiral shape on the outlet side of the compressed air in the impeller 31 and communicating with the outer periphery of the compression passage 15Bb and outside the diffuser 35 15Bc is provided. Further, the compressor housing 15B is provided with an exhaust passage 15Bd branched in a tangential direction from a part of the scroll passage 15Bc. A compressed air discharge port 34 is formed at the opening end of the exhaust passage 15Bd. The scroll passage 15Bc is formed such that the inner diameter gradually increases in the circumferential direction from the winding start having the smallest inner diameter, and is connected to the winding end that is expanded most once in the circumferential direction. An exhaust passage 15Bd is branched and provided at the end of winding where the inner shape is expanded most. A portion where the exhaust passage 15Bd branches in the scroll passage 15Bc is a portion where the winding start and the winding end are connected as described above, and a tongue portion 15Be protruding inward of the passage is formed. In the compressor 13 having such a configuration, the air taken into the air supply passage 15Ba from the air intake port 33 is compressed by the impeller 31 and is radially transmitted from the compression passage 15Bb by the diffuser 35 (perpendicular to the central axis C). In the direction in which it is diffused and turns around the scroll passage 15Bc and is discharged from the compressed air discharge port 34 of the exhaust passage 15Bd.

  In the compressor housing 15B, as shown in FIGS. 1 to 3, a recirculation passage 15Bf is formed in the air supply passage 15Ba. The recirculation passage 15Bf is a space formed in an annular shape outside the air supply passage 15Ba. The recirculation passage 15Bf is a space provided between an inner wall surface of the air supply passage 15Ba and an annular passage wall 36 provided along the inner wall surface of the air supply passage 15Ba. The impeller 31 has an annular bleed groove 36a that opens to the supply passage 15Ba on the inlet side of the supply air, and an annular recirculation groove 36b that opens to the supply passage 15Ba on the air intake port 33 side. It is formed outside the passage 15Ba so as to communicate with the impeller 31 side and the air intake port 33 side. Then, in order to secure a space between the inner wall surface of the air supply passage 15Ba and the passage wall 36 to form the recirculation passage 15Bf, the air passage extends in the axial direction between the inner wall surface of the air supply passage 15Ba and the passage wall 36. A plurality of struts 36c for partitioning the space of the existing recirculation passage 15Bf are provided in the circumferential direction.

  In the exhaust turbine supercharger 11 configured as described above, the turbine 12 is driven by exhaust gas discharged from an engine (not shown), and the rotation of the turbine 12 is transmitted to the rotary shaft 14 to drive the compressor 13. The compressor 13 compresses the combustion gas and supplies it to the engine. Specifically, the exhaust gas from the engine passes through the exhaust gas inlet passage 26 and is statically expanded by the turbine nozzle 28, and the exhaust gas flow in the axial direction is guided to the plurality of turbine blades 25. The turbine 12 is driven and rotated by the turbine wheel 24 to which the blades 25 are fixed. The exhaust gas that has driven the plurality of turbine blades 25 is discharged to the outside from the outlet passage 27. On the other hand, when the rotating shaft 14 is rotated by the turbine 12, the impeller 31 of the integrated compressor 13 is rotated by the rotating shaft 14, and air is sucked from the air intake port 33 through the air supply passage 15 </ b> Ba. The sucked air is compressed by the impeller 31 to become compressed air, and this compressed air passes through the diffuser 35 and the scroll passage 15Bc and is supplied to the engine from the compressed air discharge port 34. Further, in the compressor 13, a part of the compressed air pressurized by the impeller 31 is extracted from the extraction groove 36a to the recirculation passage 15Bf and returned from the recirculation groove 36b to the supply passage 15Ba to be recirculated. By recirculating air in the recirculation passage 15Bf in this way, for example, the pressure ratio of the impeller 31 is increased at a small flow rate when the air flow rate sucked at a low rotation of the engine is small, and the operating range of the compressor 13 is increased. Expanding.

  In the compressor (centrifugal compressor) 13 described above, the recirculation passage 15Bf is provided with three struts 36c every 120 degrees in the circumferential direction as shown in FIG. Then, as shown in FIG. 4, the strut 36c has an angular position (position of 30 deg in FIG. 4) around the rotation axis 14 (center line C) of the tongue portion 15Be formed in the scroll passage 15Bc, and the tongue It is provided every 120 degrees from the angular position of the part 15Be. At least one strut 36c is formed by reducing the cross-sectional area of the space of the recirculation passage 15Bf partitioned by the strut 36c from the bleed groove 36a toward the recirculation groove 36b at the angular position of the tongue 15Be. It is arranged so that. Specifically, as shown in FIG. 4, in the strut 36c at an angular position of 150 deg adjacent to the strut 36c in the circumferential direction at the angular position of the tongue 15Be, the recirculation groove 36b side is positioned at the angular position of the tongue 15Be. It is arranged to be inclined toward (position of 30 degrees).

  Although not clearly shown in the drawing, the strut 36c at the angular position of 150 deg may be formed to be curved so that the recirculation groove 36b side faces the angular position of the tongue portion 15Be (position of 30 deg). Although not clearly shown in the drawing, in the strut 36c at the angular position of 150 deg, only the side surface on the angular position side of the tongue portion 15Be is inclined or curved with the recirculation groove 36b side toward the angular position of the tongue portion 15Be. May be formed. Further, although not shown in the drawing, the strut 36c may be formed to be inclined or curved from the middle in the axial direction toward the recirculation groove 36b. Although not clearly shown in the drawing, in the strut 36c at the angular position of −90 deg adjacent to the strut 36c at the angular position of the tongue 15Be in the circumferential direction, the recirculation groove is similar to the strut 36c at the angular position of 150 deg. 36b side may be arrange | positioned or formed toward the angle position of tongue part 15Be. Although not clearly shown in the drawing, the recirculation groove 36b side of each strut 36c at the angular position of 150 deg and −90 deg adjacent to the strut 36c in the circumferential direction at the angular position of the tongue 15Be It may be arranged or formed toward an angular position of 15Be. Further, the strut 36c may not be provided so as to coincide with the angular position of the tongue portion 15Be. In this case, the recirculation groove 36b side of the strut 36c located closest to the angular position of the tongue portion 15Be It may be arranged or formed toward the angular position of the part 15Be.

  In the compressor 13, as described above, the scroll passage 15Bc is connected to the winding end where the inner diameter gradually increases in the circumferential direction from the winding start having the smallest inner diameter and is expanded most once in the circumferential direction. , The rotational axis 14 is non-axisymmetric. For this reason, when the flow rate is small, distortion occurs in the flow of air at the outlet of the diffuser 35, and a pressure distribution is formed in which the static pressure near the tongue portion 15Be increases. Therefore, since the reverse pressure gradient from the outlet of the diffuser 35 to the tongue portion 15Be increases, when the outlet pressure of the impeller 31 increases due to the casing treatment, the dynamic pressure at the outlet of the impeller 31 decreases. Local stall and backflow occur near the tongue 15Be having a steep reverse pressure gradient. When the recirculation passage is configured symmetrically with respect to the rotation axis as in the conventional casing treatment, the dynamic pressure at the impeller outlet decreases uniformly in the circumferential direction. It is difficult to increase the pressure locally and suppress backflow.

  In this regard, according to the compressor 13 of the present embodiment, the space of the recirculation passage 15Bf partitioned by the struts 36c at the angular position around the rotation shaft 14 of the tongue portion 15Be where the exhaust passage 15Bd branches from the scroll passage 15Bc. The cross sectional area is reduced from the bleed groove 36a toward the recirculation groove 36b. Therefore, as in the distribution of the recirculation flow rate m shown in FIG. 5A, the air recirculated in the recirculation passage 15Bf is collected at the angular position of the tongue portion 15Be and becomes a large flow rate. 5B, the air compressed by the impeller 31 and discharged to the scroll passage 15Bc through the diffuser 35 has a flow rate at the position of the tongue portion 15Be. Increasing the dynamic pressure increases. As a result, local stall and backflow in the vicinity of the tongue portion 15Be of the scroll passage 15Bc can be suppressed. Moreover, according to the compressor 13 of the present embodiment, since the flow rate of the air recirculated and discharged in the recirculation passage 15Bf is changed, the distribution of the flow rate m of the bleed groove 36a shown in FIG. As described above, the flow rate of air extracted to the recirculation passage 15Bf on the inlet side of the air supply in the impeller 31 can be made uniform in the circumferential direction, and the increase in the pressure ratio of the impeller 31 due to the air extraction can be made uniform in the circumferential direction. It is possible to suppress the occurrence of backflow as a result of an extreme increase in the pressure ratio and a decrease in the radial dynamic pressure at a specific position.

  FIG. 6 is an axial cross-sectional view of another example of the centrifugal compressor according to the present embodiment. FIG. 7 is a developed circumferential sectional view of another example of the centrifugal compressor according to the present embodiment. FIG. 8 is a developed circumferential sectional view of another example of the centrifugal compressor according to this embodiment. FIG. 9 is an axial cross-sectional view of another example of the centrifugal compressor according to the present embodiment.

  As another example of the compressor 13 of this embodiment, as shown in FIG. 6, the cross-sectional area is re-established from the bleed groove 36a at an angular position (position of 30 deg in FIG. 4) around the rotation shaft 14 of the tongue portion 15Be. In the space formed to decrease toward the circulation groove 36b, the radial width is preferably reduced from the extraction groove 36a toward the recirculation groove 36b.

  In the form shown in FIG. 6, an inclined surface 36d is formed at the position of the recirculation groove 36b so that the radially outer peripheral wall of the recirculation passage 15Bf (the inner wall surface of the compressor housing 15B of the housing 15) becomes narrow in the radial direction. Yes. Although not shown in the drawing, the inclined surface 36d may be provided on the side of the passage wall 36 of the recirculation passage 15Bf. Although not shown in the drawing, the inclined surface 36d may be provided from the bleed groove 36a to the entire recirculation groove 36b.

  According to such a configuration, the radial width of the space partitioned by the struts 36c is reduced from the bleed groove 36a toward the recirculation groove 36b, so that the exhaust passage 15Bd is formed from the scroll passage 15Bc. At the angular position around the rotating shaft 14 of the branching tongue portion 15Be, the cross-sectional area of the space of the recirculation passage 15Bf partitioned by the struts 36c decreases from the bleed groove 36a toward the recirculation groove 36b. Yes. For this reason, since the flow velocity can be increased on the discharge side of the recirculation flow and the flow distribution of recirculation can be increased at the angular position of the tongue portion 15Be, the above-described effects can be remarkably obtained.

  Furthermore, as another example of the compressor 13 of the present embodiment, as shown in FIG. 7, the cross-sectional area is the bleed groove 36a at an angular position (position of 30 deg in FIG. 6) around the rotation shaft 14 of the tongue portion 15Be. It is preferable that a part of the groove width of the bleed groove 36a is narrowly formed in the space formed so as to decrease toward the recirculation groove 36b.

  In the form shown in FIG. 7, the protrusion 36e is formed on the groove edge on the impeller 31 side of the bleed groove 36a so that a part of the groove width of the bleed groove 36a is narrowed. Although not clearly shown in the figure, the protrusion 36e may be formed on the groove edge on the air intake port 33 side of the bleed groove 36a. Further, although not shown in the drawing, a plurality of protrusions 36e may be provided.

  In a situation where the pressure in the exhaust passage 15Bd rises to become a surge region, the extraction flow rate of the recirculation flow increases and the work amount of the impeller 31 increases, so the deceleration tends to become stronger. In this regard, as in the present embodiment, if a part of the groove width of the bleed groove 36a in the space partitioned by the strut 36c is formed narrow, the pressure of the exhaust passage 15Bd rises to become a surge region. In the situation, since the extraction flow rate of the recirculation flow can be suppressed, the increase in the work amount of the impeller 31 can be suppressed and the deceleration can be weakened. Therefore, it is possible to individually control the circumferential flow distribution of the recirculation flow and the recirculation flow to the impeller 31.

  Furthermore, as another example of the compressor 13 of the present embodiment, as shown in FIGS. 8 and 9, the cross-sectional area is at an angular position (position of 30 deg in FIG. 8) around the rotation shaft 14 of the tongue portion 15Be. A shutter 36f that opens and closes a part of the groove width of the bleed groove 36a in a space formed by decreasing from the bleed groove 36a toward the recirculation groove 36b, and closes the shutter 36f when the pressure rises based on the pressure of the exhaust passage 15Bd. It is preferable to include an operating mechanism 37 that operates and opens the shutter 36f when the pressure is lowered.

  The operation mechanism 37 is a pneumatic actuator that is operated by the pressure of the diffuser 35. Specifically, the operating mechanism 37 includes an operating member 37a that opens and closes the shutter 36f, a pneumatic cylinder 37b that drives the operating member 37a, and a communication pipe 37c that communicates the compression passage 15Bb and the pneumatic cylinder 37b. doing. In the operating mechanism 37, when the pressure in the exhaust passage 15Bd increases, the pneumatic cylinder 37b drives the operating member 37a by the pressure to close the shutter 36f. On the other hand, the operating mechanism 37 opens the shutter 36f without driving the operating member 37a of the pneumatic cylinder 37b when the pressure in the exhaust passage 15Bd drops.

  As described above, in a situation where the pressure in the exhaust passage 15Bd rises to become a surge region, the extraction flow rate of the recirculation flow increases and the work amount of the impeller 31 increases, so the deceleration tends to become stronger. In this regard, in the present embodiment, since the extraction flow rate of the recirculation flow can be suppressed by closing the shutter 36f when the pressure of the exhaust passage 15Bd is increased, the increase in the work amount of the impeller 31 is suppressed and the deceleration is performed. Can weaken. On the other hand, by opening the shutter 36f when the pressure of the exhaust passage 15Bd is low when the flow rate is small, the flow rate of the air extracted into the recirculation passage 15Bf is reduced as in the flow distribution of the extraction groove 36a shown in FIG. It can be made uniform in the direction, and the work amount of the impeller 31 by the bleed air can be made uniform in the circumferential direction. Therefore, the bleed flow rate of the recirculation flow and the circumferential distribution of the recirculation flow rate to the impeller 31 can be individually controlled, and the bleed flow rate of the recirculation flow can be controlled according to the pressure of the exhaust passage 15Bd.

  Further, according to the exhaust turbine supercharger 11 having the compressor 13 described above, in the compressor 13, it is possible to suppress local stall and backflow in the vicinity of the tongue portion 15Be of the scroll passage 15Bc while expanding the operating range. Since the efficiency of supplying air to the engine is improved, the efficiency of the supercharger can be increased.

  In addition, although this embodiment demonstrated the structure applied to the compressor 13 of the exhaust turbine supercharger 11 as a centrifugal compressor, it is not this limitation. The present invention can be suitably used for a centrifugal compressor in which an impeller is attached to a rotating shaft and the compressor is compressed in a housing.

11 Exhaust turbine supercharger 13 Compressor (centrifugal compressor)
14 Rotating shaft 15 Housing 15B Compressor housing 15Ba Air supply passage 15Bb Compression passage 15Bc Scroll passage 15Bd Exhaust passage 15Bf Recirculation passage 15Be Tongue portion 31 Impeller 32 Blade 33 Air intake port 34 Compressed air discharge port 35 Diffuser 36 Passage wall 36a Extraction groove 36a 36b Recirculation groove 36c Strut 36d Inclined surface 36e Projection 36f Shutter 37 Actuation mechanism 37a Actuation member 37b Pneumatic cylinder 37c Communication pipe

Claims (5)

A rotation axis;
An impeller attached to the rotating shaft and having a plurality of blades radially;
An air supply passage provided along an axial direction in which the rotating shaft extends and extending from an air intake port to the impeller, a compression passage formed in an annular shape along an outer peripheral portion of the impeller, and the compression passage A spiral-shaped scroll passage communicating with the outer periphery, a housing having an exhaust passage branched in a tangential direction from a part of the scroll passage, and housing the rotating shaft and the impeller;
A space formed in an annular shape outside the air supply passage in the housing, and has an annular bleed groove that opens to the air supply passage on the impeller side, and opens to the air supply passage on the air intake port side. A recirculation passage having an annular recirculation groove,
A plurality of struts provided extending along the axial direction so as to partition the space inside the recirculation passage in an annular direction;
With
A cross-sectional area of the space partitioned by the struts decreases from the bleed groove toward the recirculation groove at an angular position around the rotation axis of the tongue portion where the exhaust passage branches from the scroll passage. Centrifugal compressor being used.   The radial width in the space formed by reducing the cross-sectional area from the bleed groove toward the recirculation groove is formed to be reduced from the bleed groove toward the recirculation groove. Centrifugal compressor.   The centrifugal compressor according to claim 1 or 2, wherein a part of the groove width of the extraction groove in a space formed by reducing a cross-sectional area from the extraction groove toward the recirculation groove is narrow. A shutter that opens and closes a part of the groove width of the bleed groove in a space formed by reducing the cross-sectional area from the bleed groove toward the recirculation groove;
An operating mechanism for closing the shutter when the pressure increases based on the pressure of the exhaust passage while opening the shutter when the pressure decreases;
The centrifugal compressor according to claim 1 or 2.   An exhaust turbine supercharger comprising the centrifugal compressor according to any one of claims 1 to 4.

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