JP2015137556A - centrifugal compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a centrifugal compressor which achieves high responsiveness.SOLUTION: A centrifugal compressor 22 includes: an impeller which compresses a low speed fluid introduced from a passage by rotation and outputs the low speed fluid; and a high speed fluid generation device 26 which supplies a high speed fluid having a speed higher than the low speed fluid from the upstream side relative to the impeller to the impeller along flow of the low speed fluid.

Description

  The present invention relates to a centrifugal compressor.

  In a turbo overbenefit engine, a turbine is driven by engine exhaust gas, and a compressor connected coaxially with the turbine is rotated to compress intake air and supply the compressed air into the cylinder. As a result, the intake air density in the cylinder is increased, more fuel can be combusted, and the engine output per unit displacement can be increased.

  When the turbo overbenefit engine is accelerated at low speed, the exhaust energy is small, and therefore there is a possibility that a turbo lag, which is a delay until the compressor functions, occurs when the engine is reaccelerated after deceleration. That is, when the accelerator pedal is returned during deceleration, the exhaust energy is reduced and the turbine rotational speed is gradually lowered. At the same time, the air upstream from the throttle valve flows backward with no place to go, preventing the compressor from rotating. After that, when the accelerator pedal is depressed for re-acceleration, the turbine speed increases again and a delay time occurs until the compressor functions. During this time, sufficient supercharging cannot be performed and the expected engine output cannot be obtained. .

  Therefore, a technique for applying external power to the turbocharger in order to improve the turbo lag is disclosed. For example, a technique is disclosed in which a pressure accumulating tank is provided as external power, and high-pressure air is directly introduced from a pressure accumulating tank to a turbine of a turbocharger via a pressure reducing valve to increase the energy of exhaust gas (Patent Document 1). . Further, a technique for assisting rotation by directly injecting high-pressure air from an accumulator tank into a casing of a compressor is disclosed (Patent Document 2).

Japanese Patent No. 4735434 Japanese Patent No. 19922991

  However, when the compressed air in the pressure accumulating tank is supplied via the pressure reducing valve, the energy is not effectively used for the reduced pressure energy. Further, since the back pressure of the compressor increases, a large amount of air for assisting cannot be supplied.

  Further, when assisting by supplying compressed air to the turbine, the supplied air is mixed with exhaust gas and discharged, so it does not pass through the engine cylinder and is not effectively used for fuel combustion.

  Further, the method of directly injecting compressed air from the compressor casing to the middle of the impeller cannot fully use the work of the impeller. In addition, depending on the operating conditions, the flow of mainstream air from the impeller entrance will be blocked, reducing the work at the impeller. Moreover, in order to prevent it, it is necessary to adjust the inflow angle of compressed air, and the mechanism and control system for that need to be adjusted.

  Furthermore, a surging phenomenon may occur due to the backflow of air from the exhaust side toward the intake side through a gap (clearance) between the impeller and the casing of the compressor. In particular, since the amount of air that passes through the impeller of the compressor is reduced at low speed, the surging phenomenon is often significant.

  In view of the above problems, an object of the present invention is to provide a centrifugal compressor that effectively performs fluid compression in a simple system.

  One aspect of the present invention is an impeller that compresses and outputs a low-speed fluid introduced from a flow path by rotation, and a high-speed fluid that is faster than the low-speed fluid along the flow of the low-speed fluid from the upstream side of the impeller. And a high-speed fluid introducing means for supplying the impeller.

  Here, it is preferable that the turbine further includes a turbine that is driven by a high-pressure fluid and that powers the impeller, and the high-speed fluid introduction unit supplies the fluid that has driven the turbine to the impeller as the high-speed fluid. .

  In addition, it is preferable that the high-speed fluid introduction unit includes a nozzle that increases the speed of the fluid that has driven the turbine and supplies the fluid to the impeller as the high-speed fluid.

  Moreover, it is preferable that the high-speed fluid introducing means includes a variable blade that changes an inflow angle of the high-speed fluid into the impeller.

  ADVANTAGE OF THE INVENTION According to this invention, a highly responsive centrifugal compressor can be provided.

It is a figure which shows the structure of the engine system in embodiment of this invention. It is a figure which shows the example of the introduction method of the high-speed fluid in embodiment of this invention. It is a figure explaining the effect | action by the high-speed fluid in embodiment of this invention. It is a figure which shows the change of the blade surface pressure by the high speed fluid in embodiment of this invention. It is a figure which shows another example of a structure of the engine system in embodiment of this invention. It is a figure which shows another example of the introduction method of the high-speed fluid in embodiment of this invention. It is a figure explaining the effect | action by the high-speed fluid in embodiment of this invention. It is a figure which shows another example of the introduction method of the high-speed fluid in embodiment of this invention.

  A first embodiment of the present invention will be described. As shown in FIG. 1, the engine system according to the first embodiment includes an engine body 10, an air cleaner 12, an intercooler 14, an intake manifold 16, an exhaust manifold 18, an exhaust turbine 20, a compressor (centrifugal compressor). 22, the rotor shaft 24 and the high-speed fluid generator 26 are comprised.

  Air is supplied to the intake manifold 16 via the air cleaner 12 and the intercooler 14. Further, air is distributed and supplied from the intake manifold 16 to each of the cylinders 10 a of the engine body 10. The cylinder 10a is supplied with fuel from a fuel supply system (not shown), mixed with the air supplied from the intake manifold 16, and burned. Exhaust gas generated by the combustion of fuel is exhausted from the cylinder 10a via the exhaust manifold 18.

  The engine system is provided with an exhaust turbine 20 and a compressor 22, and compresses the air introduced from the air cleaner 12 and supplies the compressed air to the intercooler 14. Specifically, as shown in FIG. 2, the compressor 22 is configured such that an impeller 32 connected to a rotor shaft 24 is accommodated in a casing 30. The power from the exhaust turbine 20 is transmitted to the impeller 32 through the rotor shaft 24, and the impeller 32 rotates to suck air as a low-speed fluid from the intake port 34 of the casing 30 and compress the compressed air from the exhaust port 36. Supply to intercooler 14.

  Furthermore, in the present embodiment, a high-speed fluid generator 26 is provided. The high-speed fluid generator 26 functions as high-speed fluid introduction means that can supply high-speed fluid to the compressor 22. The fluid is preferably air. The high-speed fluid generator 26 generates a high-speed fluid having a flow velocity faster than the flow velocity of air sucked from the intake port 34 by the compressor 22, and sucks from the upstream side of the impeller 32 of the compressor 22, that is, the intake port 34 side. A high-speed fluid is supplied along the main flow of air. The speed of the high-speed fluid is preferably larger than the speed of the mainstream intake air and does not exceed the speed of sound.

  For example, as shown in FIG. 2, an inner pipe 34 a is provided in the intake port 34 of the casing 30 to form a double pipe structure, and high-speed fluid is introduced so as to directly contact the impeller 32 from between the casing 30 and the inner pipe 34 a. .

  In FIG. 2, the flow of the high-speed fluid and the intake air is indicated by arrows. The faster the flow, the thicker the arrow.

  FIG. 3 is a diagram for explaining the effect of introducing a high-speed fluid to the impeller 32. When the high-speed fluid is not introduced, the air sucked with respect to the peripheral speed U of the blade (impeller blade) 32a of the impeller 32 flows in at the air speed C1, so that the relative speed W1 is obtained at the inlet of the impeller 32. On the other hand, when a high-speed fluid is introduced, the high-speed fluid flows at a fluid flow velocity C2 higher than the air velocity C1 with respect to the circumferential speed U of the blade 32a of the impeller 32, so that the relative velocity W2 is obtained at the inlet of the impeller 32. . In the relative speed W2, the angle of attack with respect to the blade 32a is larger than the relative speed W1 by an angle θ, and the fluid strongly collides with the blade 32a. Thereby, as shown in FIG. 4, a large pressure difference is generated between the pressure surface 32 b and the suction surface 32 c of the impeller 32. As a result, rotational torque is generated in the blade 32a, and the acceleration response is improved as compared with the case where no high-speed fluid is introduced.

  In particular, the turbo lag, which is a delay until the compressor 22 functions during low-speed acceleration, can be reduced. Thereby, sufficient supercharging can be performed with respect to the engine main body 10, and the expected engine output can be obtained.

  In the present embodiment, since the high speed fluid is introduced from the inlet side of the impeller 32, the energy of the high speed fluid can be effectively used for the impeller 32. Further, the compressed air can be effectively supplied from the compressor 22 to the engine body 10 without blocking the flow of air sucked from the inlet of the impeller 32.

  Furthermore, the backflow of air through the clearance (clearance) between the impeller 32 and the casing 30 of the compressor 22 can be suppressed, and further, the occurrence of the surging phenomenon can be suppressed.

  Further, a valve 28 may be provided so that air can be supplied from the air cleaner 12 to the gap between the casing 30 and the inner pipe 34a. By providing the valve 28, when high-speed fluid is not introduced from the high-speed fluid generator 26, air can be sucked into the impeller 32 from the gap between the casing 30 and the inner pipe 34a by opening the valve 28. On the other hand, when the high-speed fluid is introduced from the high-speed fluid generator 26, the air flow from the air cleaner 12 to the gap between the casing 30 and the inner pipe 34a can be stopped by closing the valve 28.

  As shown in FIG. 5, the high-speed fluid generator 26 includes an auxiliary compressed fluid supply device 40, a check valve 42, a pressure accumulating tank 44, a flow rate adjusting electromagnetic valve 46, a driving turbine 48, a rotor shaft 50, a one-way clutch 52, and a control device. 54 can be configured.

  The auxiliary compressed fluid supply device 40 includes fluid compression means such as a compression pump and a turbo compressor, for example. The fluid compressed by the auxiliary compressed fluid supply device 40 is stored in the pressure accumulation tank 44 in a high pressure state via the check valve 42. The check valve 42 is a valve that prevents the compressed fluid stored in the pressure accumulation tank 44 from flowing back to the auxiliary compressed fluid supply device 40.

  The compressed fluid stored in the pressure accumulating tank 44 is supplied to the drive turbine 48 as a high-pressure fluid via the flow rate adjusting electromagnetic valve 46. The flow rate adjusting electromagnetic valve 46 adjusts the flow rate of the compressed fluid supplied to the drive turbine 48 under the control of the control device 54. When the flow rate adjusting electromagnetic valve 46 is in the closed state, the compressed fluid is not supplied from the pressure accumulation tank 44 to the drive turbine 48. When the flow rate adjusting electromagnetic valve 46 is in the open state, the compressed fluid is supplied from the pressure accumulation tank 44 to the drive turbine 48. The drive turbine 48 is driven by a compressed fluid having a flow rate corresponding to the opening degree (opening degree) of the flow rate adjusting electromagnetic valve 46.

  The drive turbine 48 is coupled to the exhaust turbine 20 or the centrifugal compressor 22 by the rotor shaft 50 via the one-way clutch 52, and only when the rotational speed of the drive turbine 48 is higher than the rotational speed of the exhaust turbine 20, The rotation of the exhaust turbine 20 is linked to the rotation. The one-way clutch 52 is provided so that the drive turbine 48 does not become a resistance of the exhaust turbine 20 and the compressor 22 when the responsiveness of the compressor 22 is not required.

  With such a configuration, the rotational speed of the impeller 32 of the compressor 22 can be increased even when the amount of exhaust gas discharged from the engine body 10 is small, such as during low-speed acceleration, and the compressed air is supplied to the engine body 10. Can be supplied effectively.

  Further, a flow path 56 for introducing the exhaust fluid of the drive turbine 48 into the compressor 22 is provided. As a result, high-speed fluid exhausted from the drive turbine 48 is supplied to the compressor 22. As a result, rotational torque is generated in the blade 32a of the impeller 32, and acceleration response is improved. Further, the turbo lag can be reduced, and the engine output can be sufficiently obtained.

  A nozzle 58 may be provided in the flow path 56 in order to increase the flow rate of the fluid exhausted from the drive turbine 48. By providing the nozzle 58, the flow velocity of the fluid from the drive turbine 48 can be increased, and the rotational force can be increased on the blade 32a of the impeller 32.

  In the present embodiment, it is preferable not to provide a pressure reducing valve in the flow path 56. This is because if the compressed air is supplied through the pressure reducing valve, the pressure energy that has been reduced is not effectively used.

  Further, a variable blade (variable blade) whose angle can be changed with respect to the flow path may be provided in the flow path of the high speed fluid so that the angle at which the high speed fluid collides with the blade 32a of the impeller 32 may be controlled. For example, as shown in FIG. 6, a plurality of variable blades 60 that are rotatable with respect to the flow path are arranged in the circumferential direction in the flow path of the high-speed fluid formed by the casing 30 and the inner tube 34a. . By rotating the variable blade 60 with respect to the flow path, the flow of the high-speed fluid flowing through the flow path can be changed along the circumferential direction of the flow path.

  Accordingly, as shown in FIG. 7, in the configuration in which the variable blade 60 is not provided, the high-speed fluid flowing at the fluid flow velocity C2 can be swirled, and the blade of the impeller 32 can be changed by changing the inflow angle of the high-speed fluid. It can be made to flow in at 32 at the fluid flow velocity C3. The high speed fluid is faster than the air speed C1 with respect to the peripheral speed U of the blade 32a of the impeller 32 and flows at a fluid flow velocity C3 that is a larger angle of attack with respect to the variable blade 60 than the fluid flow velocity C2. The speed becomes W3. The relative speed W3 has a larger angle of attack with respect to the blade 32a than the relative speed W2, and the fluid strongly collides with the blade 32a. Therefore, the pressure difference between the pressure surface and the suction surface side of the impeller 32 becomes larger, the torque in the rotational direction with respect to the blade 32a also becomes larger, and the acceleration response is higher than when the high-speed fluid is not swirled by the variable blade 60. Improved.

  Further, as shown in FIG. 8, the flow path for introducing the high-speed fluid into the impeller 32 may be provided with an inclined portion 30a that is narrowed from the outside to the inside of the intake port immediately before introduction into the impeller 32. Good. In order to prevent the flow of air from being disturbed by the high-speed fluid, it is preferable to make the inclination angle of the inclined portion 30a as gentle as possible.

  By providing the inclined portion 30a in this manner, the flow path width D1 of the air sucked from the air cleaner 12 to the compressor 22 is kept substantially equal to the width D2 of the inlet to the impeller 32, while the high-speed fluid generator 26 It is possible to introduce the high-speed fluid into the outer peripheral portion of the impeller 32. Further, since the width D1 of the flow path of the air to be sucked can be made comparable to that of the conventional compressor, the air is sucked by the compressor 22 even when the high-speed fluid is not introduced from the high-speed fluid generator 26. The flow rate of air is not reduced compared to the prior art.

  10 engine body, 10a cylinder, 12 air cleaner, 14 intercooler, 16 intake manifold, 18 exhaust manifold, 20 exhaust turbine, 22 (centrifugal) compressor, 24 rotor shaft, 26 high-speed fluid generator, 28 valve, 30 casing, 30a inclined portion, 32 impeller, 32a blade (impeller blade), 34 intake port, 34a inner pipe, 36 exhaust port, 40 auxiliary compressed fluid supply device, 42 check valve, 44 pressure accumulation tank, 46 flow rate adjusting solenoid valve, 48 drive Turbine, 50 rotor shaft, 52 one-way clutch, 54 controller, 56 flow path, 58 nozzle, 60 variable blade (variable blade).

Claims (4)

An impeller that compresses and outputs low-speed fluid introduced from the flow path by rotation;
High-speed fluid introduction means for supplying a high-speed fluid faster than the low-speed fluid to the impeller along the flow of the low-speed fluid from the upstream side of the impeller;
A centrifugal compressor. The centrifugal compressor according to claim 1,
A turbine driven by high pressure fluid to power the impeller;
The high-speed fluid introduction means is a centrifugal compressor that supplies the fluid that has driven the turbine to the impeller as the high-speed fluid. The centrifugal compressor according to claim 2,
The high-speed fluid introducing means is a centrifugal compressor including a nozzle that increases the speed of a fluid that drives the turbine and supplies the fluid to the impeller as the high-speed fluid. The centrifugal compressor according to any one of claims 1 to 3,
The high-speed fluid introducing means is a centrifugal compressor including variable blades that change an inflow angle of the high-speed fluid into the impeller.

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