JP5444836B2 - Centrifugal compressor - Google Patents

Description

  The present invention relates to a centrifugal compressor that compresses a gas such as air using centrifugal force.

  In recent years, various developments have been made on centrifugal compressors used in vehicle superchargers, marine superchargers, gas turbines, etc. The following is a brief description of the general configuration of a centrifugal compressor. (See Patent Document 1 and Patent Document 2).

  That is, a general centrifugal compressor has a housing, and an impeller is rotatably provided in the housing. Further, the impeller includes a wheel that can rotate around the axis of the impeller, and a plurality of blades that are provided at intervals on the outer peripheral surface of the wheel. Here, the outer edge of each blade extends along the inner wall of the housing.

  A suction port for sucking air (an example of gas) to the impeller side is formed in the upstream peripheral edge of the inner wall of the housing. Further, an exhaust passage for exhausting compressed air is formed on the downstream peripheral edge of the inner wall of the housing.

  Accordingly, when operating the centrifugal compressor, for example, by rotating the rotor shaft (not shown) using the energy of the exhaust gas from the internal combustion engine (not shown), a plurality of blades are integrated with the wheel. Rotate, in other words, rotate the impeller. Thereby, the air suck | inhaled to the impeller side from the inlet can be compressed using a centrifugal force, and the compressed air can be exhausted from an exhaust flow path.

Japanese Patent Laid-Open No. 2005-240680 JP 2006-152972 A

  By the way, when the air flow rate at the inlet side of the impeller decreases during the operation of the centrifugal compressor and the incidence on the inlet side of the impeller (the difference between the relative flow angle and the wing angle) increases, the air flows near the leading edge of the blade. Flow separation (peeling zone) occurs, and the centrifugal compressor reaches surging. On the other hand, in recent years, there is an increasing demand for sufficiently suppressing the surging of the centrifugal compressor and expanding the operating range of the centrifugal compressor.

  Then, an object of this invention is to provide the centrifugal compressor of a novel structure which can solve the above-mentioned subject.

  In order to solve the above-mentioned problems, the inventor of the present invention repeated various trials and errors, and as a result, the gas flow around the shroud on the inlet side of the impeller was swirled in the direction opposite to the impeller rotation direction. As compared with the case where the rotation in the direction opposite to the rotation direction of the impeller is not given, the relative Mach number on the inlet side of the impeller is increased as shown in FIGS. 5 and 6, and in the vicinity of the shroud on the inlet side of the impeller. The gas flow shifts from a transonic flow to a supersonic flow, and a separation shock wave that is substantially perpendicular to the blade surface is generated near the front edge of the blade, suppressing the occurrence of gas flow separation (separation zone). 1st novel knowledge that it was possible to be able to be obtained, and it came to complete the 1st invention. Furthermore, in addition to the above conditions, when the circumferential groove is formed on the inner wall of the housing so as to surround the downstream side of the leading edge of the plurality of blades, the pressure surface from the blade pressure surface through the circumferential groove. As shown in FIG. 7, the generation location of the separation shock wave is displaced (transferred) to the downstream side to suppress the development of a low energy region (low energy region in the impeller) between the blades. The second novel finding was obtained, and the second invention was completed. In addition to the above conditions, the relative Mach number at the inlet side of the impeller is extremely high to the extent that the relative flow of gas around the shroud at the inlet side of the impeller becomes supersonic flow even if the reverse rotation is not given. In the case where the circumferential groove is formed on the inner wall of the housing so as to surround the vicinity of the downstream side of the leading edge of the plurality of blades, the same relative Mach number distribution (not shown) can be obtained. Another novel finding was also obtained that the location where the shock wave was generated could be displaced downstream to suppress the development of a low energy region between the blades.

  Here, FIG. 5 is a diagram showing the relative Mach number distribution of the gas in the impeller viewed from the outside in the radial direction when no rotation in the direction opposite to the rotation direction of the impeller is given, and FIG. 6 shows the rotation direction of the impeller. FIG. 7 is a diagram showing the relative Mach number distribution of gas in the impeller viewed from the outside in the radial direction when swirling in the reverse direction is given. FIG. 7 gives swirling in the direction opposite to the rotation direction of the impeller and forms a circumferential groove. It is a figure which shows the relative Mach number distribution of the gas in the impeller seen from the radial direction outer side in the case of doing. Further, the relative Mach number distribution of the gas in the impeller is obtained by CFD (Computational Fluid Dynamics) analysis.

According to a first aspect of the present invention, there is provided a centrifugal compressor that compresses gas by utilizing centrifugal force, a housing, a wheel that is rotatably provided in the housing, and is rotatable around an axis, and the wheel An impeller provided with a plurality of blades provided on the outer peripheral surface at intervals in the circumferential direction and having an outer edge extending along the inner wall of the housing. An inlet for sucking gas to the impeller side is formed on the inlet side of the impeller, and an exhaust passage for exhausting compressed gas is formed on the downstream peripheral edge (outlet side of the impeller) of the inner wall of the housing, narrowed portion gradually reduced in diameter to the inner diameter toward the downstream direction in the inlet side of the impeller in the inner wall of the housing is formed, on the upstream side of the narrowed portion in the inner wall of the housing A plurality of inlet guide vanes impart swirl in a rotational direction opposite to the direction of the impeller to the gas flow in the peripheral shroud (inner wall near the housing) are provided at intervals in the circumferential direction, the diameter reduction of the narrowed portion L, where the height of the inlet guide vane is H , the gist is that the relationship of H ≦ L is established .

  Here, in the claims and the specification, “upstream” means upstream as viewed from the flow direction of the mainstream gas, and “downstream” means downstream as viewed from the flow direction of the mainstream gas. That is.

  According to the feature of the first invention, when operating the centrifugal compressor, the blades are rotated together with the wheel, in other words, the impeller is rotated. Thereby, the gas sucked into the impeller side from the suction port can be compressed using centrifugal force, and the compressed gas can be exhausted from the exhaust passage.

Further, since the plurality of inlet guide vanes are provided at intervals in the circumferential direction on the upstream side of the throttle portion on the inner wall of the housing , in other words, on the inlet side of the impeller, the first first described above is provided. Considering new knowledge, even when the gas flow rate on the inlet side of the impeller decreases during the operation of the centrifugal compressor, the relative flow of gas around the shroud on the inlet side of the impeller is kept at supersonic flow. As shown in FIG. 8, the action of the separation shock wave generated near the leading edge of the blade can prompt the gas to follow the blade surface of the blade.

  Here, FIG. 8 is a development view seen from the outside in the radial direction showing the relative flow of the gas that has passed the separation shock wave.

  In addition, if the relative Mach number on the inlet side of the impeller is very high to the extent that the relative flow of gas around the shroud on the inlet side of the impeller becomes supersonic flow without giving the reverse turning, By applying the above-described another novel finding, as shown by a two-dot chain line in FIG. 8, the generation site of the separation shock wave is displaced downstream, and a low energy region between the blades (low energy in the impeller is reduced). (Region) development can be suppressed.

A feature of the second invention is that, in addition to the feature of the first invention , a bottomed circumferential groove (circumferential groove) for generating a gas flow from the pressure surface of the blade to the suction surface on the inner wall of the housing. ) Is formed so as to surround the vicinity of the downstream side of the leading edge of the plurality of blades.

  Here, “the plurality of blades” refers to a plurality of blades having the longest axial length when the plurality of blades are composed of a plurality of types of the blades having different axial lengths.

  According to the feature of the second invention, in addition to the effect of the feature of the first invention, the circumferential groove is formed on the inner wall of the housing so as to surround the downstream side vicinity of the front edge of the plurality of blades. Therefore, when the second novel finding described above is applied, the generation location of the separation shock wave can be displaced downstream, and the development of the low energy region between the blades can be suppressed.

  According to the first and second aspects of the present invention, during the operation of the centrifugal compressor, even if the gas flow rate on the inlet side of the impeller decreases, the relative flow of gas around the shroud on the inlet side of the impeller is supersonic. Since the gas can be urged to follow the blade surface of the blade by the action of the separation shock wave while maintaining the flow, separation of the gas flow in the vicinity of the leading edge of the blade that causes surging of the centrifugal compressor is prevented. Sufficiently suppressed, the operating range of the centrifugal compressor can be expanded to the low flow rate side.

  Further, according to the second invention, the generation location of the separation shock wave can be displaced downstream to suppress the development of a low energy region between the blades. Therefore, energy loss between the blades can be reduced, and the centrifugal force can be reduced. The efficiency of the compressor (compressor efficiency) can be increased. In the first invention, the same effect can be obtained when the relative Mach number on the inlet side of the impeller is very high.

It is a sectional side view concerning the centrifugal compressor concerning a 1st embodiment. 2A is an enlarged view of the arrow portion IIA in FIG. 1, and FIG. 2B is a development view of the arrow portion IIB in FIG. 2A. It is a sectional side view of the centrifugal compressor concerning a 2nd embodiment. It is a sectional side view of the centrifugal compressor which concerns on 3rd Embodiment. It is a figure which shows the relative Mach number distribution of the gas in the impeller seen from the radial direction outer side, when not turning in the direction opposite to the rotation direction of the impeller. It is a figure which shows the relative Mach number distribution of the gas in the impeller seen from the radial direction outer side at the time of giving the rotation in the direction opposite to the rotation direction of the impeller. It is a figure which shows the relative Mach number distribution of the gas in the impeller seen from the radial direction outer side in the case where the turning in the direction opposite to the rotation direction of the impeller is given and the circumferential groove is formed. It is the expanded view seen from the radial direction outer side which shows the relative flow of the gas which passed the separation | shock shock wave.

(First embodiment)
A first embodiment will be described with reference to FIGS. 1 and 2A and 2B. In the drawings, “F” indicates the forward direction, and “R” indicates the backward direction.

  As shown in FIG. 1, the centrifugal compressor 1 according to the first embodiment is used for a supercharger, and compresses air (an example of gas) using centrifugal force. And the specific structure of the centrifugal compressor 1 which concerns on 1st Embodiment is as follows.

  The centrifugal compressor 1 includes a housing 3, and the housing 3 has an inner wall 5 on the inner side. The housing 3 is integrally attached to another housing (not shown).

  An impeller 7 is rotatably provided in the inner wall 5 of the housing 3. Specifically, a wheel 9 is provided in the inner wall 5 of the housing 3, and the outer peripheral surface of the wheel 9 gradually extends from the axial direction of the impeller 7 toward the radially outer side. The wheel 9 is integrally connected to one end portion (front end portion) of a rotor shaft (turbine shaft) 11 that is rotatably provided in another housing, and is rotatable about the axis of the impeller 7. is there. Further, on the outer peripheral surface of the wheel 9, a plurality of (only one illustrated) long blades (full blades) 13 and a plurality of (only one illustrated) short blades (splitter blades) 15 are spaced apart in the circumferential direction. Are provided alternately. Here, the front edge of the long blade 13 is located on the upstream side (front side) of the front edge of the short blade 15, and the outer edge of each long blade 13 and the outer edge of each short blade 15 are the inner walls of the housing 3. 5 is extended along. Instead of using two types of blades 13 and 15 having different axial lengths, blades having the same axial length may be used.

  An intake port (air supply port) 17 for sucking (supplying) air to the impeller 7 side is formed on the upstream peripheral edge (inlet side of the impeller 7) of the inner wall 5 of the housing 3. It can be connected to an air cleaner (not shown). An annular diffuser flow path 19 (one of the exhaust flow paths) for decelerating and exhausting the compressed air is formed on the downstream peripheral edge (the outlet side of the impeller 7) of the inner wall 5 of the housing 3, A spiral scroll channel 21 (one of the exhaust channels) for exhausting compressed air is formed on the peripheral side of the diffuser channel 19 inside the housing 3. A discharge port (not shown) for discharging compressed air is formed at an appropriate position of the housing 3, and this discharge port communicates with the scroll flow path 21 and the diffuser flow path 19, and is used as an internal combustion engine. It can be connected to an intake manifold (not shown) of the engine.

  As shown in FIGS. 1 and 2A and 2B, a throttle portion 23 is formed on the inlet side of the impeller 7 in the inner wall 5 of the housing 3, and this throttle portion 23 is directed toward the downstream direction. The inner diameter is gradually reduced. A plurality of arc-shaped vane plates 25 (only one is shown) are embedded along the circumferential direction on the upstream side (inlet side of the impeller 7) of the throttle portion 23 in the inner wall 5 of the housing 3. The vane plate 25 is provided with a plurality of inlet guide vanes 27 that give the air flow around the shroud on the inlet side of the impeller 7 (around the inner wall 5 of the housing 3) in a direction opposite to the rotation direction of the impeller 7. Yes. In other words, a plurality of inlet guide vanes 27 are provided at intervals in the circumferential direction via the plurality of vane plates on the inner wall 5 of the housing 3 upstream of the throttle portion 23.

  Here, when the amount of diameter reduction of the throttle portion 23 is L and the height of the inlet guide vane 27 is H, the relationship of H ≦ L is established. This is for restricting the downstream of the inlet guide vane 27 and rectifying the flow of air flowing into the impeller 7. The diameter reduction amount L of the throttle portion 23 is a value obtained by subtracting the inner radius of the downstream end 23d of the throttle portion 23 from the inner radius of the upstream end 23u of the throttle portion 23.

  Then, the effect | action and effect of 1st Embodiment are demonstrated.

  When the centrifugal compressor 1 is operated, the rotor shaft 11 is rotated using the energy of the exhaust gas from the exhaust manifold (not shown) of the internal combustion engine so that the plurality of blades 13 and 15 are connected to the wheel 9. The impeller 7 is rotated integrally. In other words, the impeller 7 is rotated. As a result, the air sucked into the impeller 7 from the suction port 17 can be compressed using centrifugal force, and the compressed air is exhausted from the diffuser flow path 19 and the scroll flow path 21 and passes through the discharge port. Can be sent to the intake manifold of the internal combustion engine.

  In addition, since a plurality of inlet guide vanes 27 are provided in the inner wall 5 of the housing 3 on the upstream side of the throttle portion 23 at intervals in the circumferential direction, the first new knowledge ([Solving the problem] In view of the above, the relative flow of air around the shroud on the inlet side of the impeller 7 is supersonic flow even when the air flow rate on the inlet side of the impeller 7 decreases during the operation of the centrifugal compressor 1. The air can be urged to follow the suction surface of the long blade 13 by the action of the separation shock wave generated near the front edge of the long blade 13.

  Further, when the relative Mach number on the inlet side of the impeller 7 is very high to the extent that the relative flow of air around the shroud on the inlet side of the impeller 7 becomes supersonic flow without giving the turning in the reverse direction. Applying the above-mentioned another novel finding (see [Means for Solving the Problems]), the generation site of the separation shock wave is displaced downstream, and the low energy region (inside the impeller 7) between the long blades 13 is displaced. (Low energy region) can be suppressed.

  Therefore, according to the first embodiment, separation of the air flow in the vicinity of the leading edge of the long blade 13 that causes surging of the centrifugal compressor 1 is sufficiently suppressed, and the operating range of the centrifugal compressor 1 is reduced. It can be expanded to the flow rate side.

  Further, when the relative Mach number on the inlet side of the impeller 7 is very high, the development of a low energy region between the long blades 13 (low energy region in the impeller 7) can be suppressed. Thus, the efficiency (compressor efficiency) of the centrifugal compressor 1 can be increased.

(Second Embodiment)
A second embodiment will be described with reference to FIG.

  As shown in FIG. 3, the centrifugal compressor 29 according to the second embodiment compresses air using centrifugal force, and has substantially the same configuration as the centrifugal compressor 1 according to the first embodiment. Of the specific configuration of the centrifugal compressor 29 according to the second embodiment, portions different from the specific configuration of the centrifugal compressor 1 according to the first embodiment will be described. Of the plurality of components in the centrifugal compressor 29 according to the second embodiment, those corresponding to the components in the centrifugal compressor 1 according to the first embodiment are denoted by the same reference numerals in the figure. Description is omitted.

  A circumferential groove (circumferential groove) 31 is formed on the inner wall 5 of the housing 3 so as to surround the vicinity of the downstream side of the front edge of the plurality of long blades 13. Here, the vicinity of the downstream side of the front edge of the long blade 13 refers to a portion that is intermediate between the front edge and the rear edge of the long blade 13 and is close to the front edge side of the long blade 13.

  According to the second embodiment, in addition to the same operation as the operation according to the first embodiment, the circumferential groove 31 surrounds the downstream side of the front edge of the plurality of long blades 13 on the inner wall 5 of the housing 3. Therefore, when the second novel finding described above (refer to [Means for Solving the Problems]) is applied, the generation site of the separation shock wave is displaced downstream, and the gap between the long blades 13 is changed. Development of the low energy region can be suppressed.

  Therefore, according to the second embodiment, in addition to the effects of the first embodiment, the development of a low energy region in the impeller 7 can be suppressed, so that energy loss between the long blades 13 is reduced and the centrifugal force is reduced. The efficiency of the compressor 1 can be increased.

(Third embodiment)
A third embodiment will be described with reference to FIG.

  As shown in FIG. 4, the centrifugal compressor 33 according to the third embodiment compresses air using centrifugal force and has substantially the same configuration as the centrifugal compressor 1 according to the first embodiment. Of the specific configuration of the centrifugal compressor 33 according to the third embodiment, portions different from the specific configuration of the centrifugal compressor 1 according to the first embodiment will be described. In addition, about the component corresponding to the component in the centrifugal compressor 1 which concerns on 1st Embodiment among the some components in the centrifugal compressor 33 which concerns on 3rd Embodiment, the same number is attached | subjected in a figure. Description is omitted.

  At the downstream side of the front edge of the long blade 13 in the inner wall 5 of the housing 3, one or a plurality (only one is shown) of bleed holes 35 that can bleed back flow air are formed. In the upstream side of the front edge of the inlet guide vane 27, one or a plurality of (only one shown) outflow holes 37 through which air can flow out to the inlet side of the impeller 7 are formed. An annular cavity (treatment cavity) 39 that allows air to flow from the extraction hole 35 side to the outflow hole 37 side is formed inside the housing 3. An annular extraction groove (an example of an extraction hole) is formed instead of one or a plurality of extraction holes 35, or an annular outflow groove (an example of an outflow hole) instead of one or a plurality of outflow holes 37. ) May be formed.

  According to the third embodiment, in addition to the same operation as the operation according to the first embodiment, during the operation of the centrifugal compressor 33, the air flow rate on the inlet side of the impeller 7 decreases, and the impeller 7 A back flow of air (a part of the air sucked into the impeller 7 side) occurs, and the back-flowed air is extracted from the extraction hole 35 and flows into the cavity 39. Then, the air that has flowed into the cavity 39 flows from the extraction hole 35 side to the outflow hole 37 side, flows out from the outflow hole 37 to the inlet side of the impeller 7, and is again sucked into the impeller 7 side. Thereby, a part of the air sucked into the impeller 7 side is circulated between the bleed hole 35 and the outflow hole 37, and the operation of the centrifugal compressor 33 can be stabilized.

  Therefore, according to the third embodiment, the effect of the first embodiment can be further enhanced.

  In addition, this invention is not restricted to description of the above-mentioned embodiment, It can implement in a various aspect. Further, the scope of rights encompassed by the present invention is not limited to these embodiments.

DESCRIPTION OF SYMBOLS 1 Centrifugal compressor 3 Housing 5 Inner wall 7 Impeller 9 Wheel 11 Rotor shaft 13 Long blade 15 Short blade 17 Suction port 19 Diffuser flow path (exhaust flow path)
21 Scroll channel (exhaust channel)
23 throttle portion 23u upstream end 23 d downstream end 25 vane plate 27 inlet guide vanes 29 a centrifugal compressor 31 circumferential groove 33 centrifugal compressor 35 bleed hole 37 outlet hole 39 cavity

Claims (3)

In a centrifugal compressor that compresses gas using centrifugal force,
A housing;
A wheel rotatably provided in the housing and rotatable around an axis, and a plurality of wheels provided at circumferential intervals on the outer peripheral surface of the wheel and having outer edges extending along the inner wall of the housing An impeller provided with a blade,
A suction port for sucking gas to the impeller side is formed in the upstream peripheral portion of the inner wall of the housing, and an exhaust passage for exhausting compressed gas is formed in the downstream peripheral portion of the inner wall of the housing,
A throttle part having an inner diameter gradually reduced in the downstream direction is formed on the inlet side of the impeller on the inner wall of the housing, and the impeller is arranged on the upstream side of the throttle part on the inner wall of the housing to flow gas around the shroud. When a plurality of inlet guide vanes that provide a turn in the direction opposite to the rotation direction of the nozzle are provided at intervals in the circumferential direction, the diameter reduction amount of the throttle portion is L, and the height of the inlet guide vane is H , H ≦ L. The centrifugal compressor is characterized in that the relationship is established.   A bleed hole is formed in the inner wall of the housing to bleed the gas that has flowed back to the downstream side of the leading edge of the blade, and the gas is fed to the upstream side of the leading edge of the inlet guide vane on the inner wall of the housing. The outflow hole that can flow out to the outside is formed, and an annular cavity that allows gas flow from the bleed hole side to the outflow hole side is formed inside the housing. Centrifugal compressor. The inner wall of the housing, the circumferential groove having a bottom for generating a flow of gas to the suction side from the pressure surface of the blade is formed so as to surround the vicinity of the downstream side of the front edge of a plurality of said blades The centrifugal compressor according to claim 1 .

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