JP2013204422A - Turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve turbine efficiency in a low rotation region, with simplified and cost-reduced configuration.SOLUTION: A turbine includes: a turbine shaft 7; a bearing housing in which the turbine shaft is supported in a freely rotatable manner; a turbine housing 4 extended in the bearing housing; and a turbine impeller which includes a turbine wheel 8a accommodated in the turbine housing and fixed to the turbine shaft, and a plurality of turbine blades 8b which extend from the turbine wheel to the outside in a radial direction and whose curved parts 8c positioned outside in the radial direction are opposed to an inner wall of the turbine housing, and converts energy of a fluid flowing inwards in the radial direction into energy of rotary motion around the turbine shaft. Downstream side end portions of the curved parts 8e are positioned in a region where a flow passage area of a cross section vertical to the turbine shaft is decreased gradually toward the downstream.

Description

  The present invention relates to a turbine that converts fluid energy into rotational motion energy.

  A turbine rotates an impeller (impeller) with fluid energy to obtain rotational kinetic energy. Such a turbine is used, for example, in a supercharger connected to an engine. In the supercharger, the turbine impeller is rotated by exhaust gas discharged from the engine, and the rotation of the turbine impeller is transmitted to the compressor impeller of the centrifugal compressor via the turbine shaft. The gas sucked from the suction port is boosted by the action of the compressor impeller. At this time, the exhaust gas that gives rotational kinetic energy to the turbine impeller passes through the center side of the turbine impeller and is discharged from the discharge port.

  In the turbine described above, the blades of the turbine impeller are formed in a shape along the inner wall (shroud) of the turbine housing. In this way, fluid is prevented from passing through the gap between the turbine housing inner wall and the turbine impeller without energy conversion, and the turbine efficiency (energy conversion efficiency in the turbine) is improved.

  Further, in a region where the number of revolutions per unit time in the turbine is low (hereinafter, simply referred to as a low-speed region), a back flow of fluid occurs near the fluid outlet of the turbine impeller on the inner wall of the turbine housing, and the turbine efficiency is lowered. Therefore, a technique has been disclosed in which guide vanes protruding in the flow passage on the inner periphery of the diffuser are separately provided to suppress loss due to backflow and improve turbine efficiency (for example, Patent Document 1).

Japanese Patent Laid-Open No. 9-264106

  In recent years, improvements in turbine efficiency in low-speed regions such as city riding in vehicles and idling stop functions have been eagerly desired. However, the technique of Patent Document 1 described above has a problem that high-precision processing for the turbine housing and separate members such as a guide blade and a guide blade rotation shaft are required, which increases costs.

  Further, in the technique of Patent Document 1 described above, in a region where the number of revolutions per unit time in the turbine is high (hereinafter simply referred to as a high revolution region), the guide blade causes a friction loss of the fluid, leading to a decrease in turbine efficiency. End up.

  Accordingly, an object of the present invention is to provide a turbine capable of improving turbine efficiency, particularly in a low rotation region, with a simple and low-cost configuration.

  In order to solve the above-described problems, a turbine according to the present invention includes a turbine shaft, a bearing housing that rotatably supports the turbine shaft, a turbine housing that extends from the bearing housing, and a turbine housing that is accommodated in the turbine shaft. A turbine wheel fixed to the turbine wheel, and a plurality of turbine blades extending radially outward from the turbine wheel, and rotational movement of fluid energy flowing radially inward about the turbine axis A turbine impeller that converts the energy of the flow path to the downstream side in the fluid flow direction of the curved portion, the flow passage area of the cross section perpendicular to the turbine axis is directed downstream in the fluid flow direction It is located in the area | region which decreases gradually as it is characterized.

  In order to solve the above-described problems, another turbine of the present invention includes a turbine shaft, a bearing housing that rotatably supports the turbine shaft, a turbine housing that extends from the bearing housing, and is accommodated in the turbine housing. A turbine wheel fixed to the turbine shaft, and a plurality of turbine blades extending radially outward from the turbine wheel and facing the inner wall of the turbine housing. A turbine impeller for converting energy of a fluid flowing inward in a direction into energy of rotational motion about the turbine shaft, and the turbine at an end portion located downstream of the fluid flow direction in the curved portion A tangent projected on the plane including the axis of the shaft and the end is directed downstream in the fluid flow direction. The distance between the turbine shaft is equal to or shorter as the power sale.

  According to the present invention, it is possible to improve the turbine efficiency particularly in a low rotation region with a simple and low-cost configuration.

It is a schematic sectional drawing of a supercharger. It is the elements on larger scale of AA in FIG. It is explanatory drawing explaining the entropy increase amount of the fluid from the upstream to the downstream in a turbine impeller. It is explanatory drawing which showed the change of the flow-path area. It is explanatory drawing which showed the relationship between a fluid flow volume and turbine efficiency.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating the understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

  In the present embodiment, a turbocharger including a radial turbine is given as a typical example of a turbine. The supercharger operates the turbine using the energy of exhaust gas discharged from the engine, and supercharges the air supplied to the engine using the rotational force. The turbine is integrally formed as part of the supercharger. Here, a turbocharger provided with a radial turbine is illustrated, but a mixed flow turbine may be used instead of the radial turbine, and not only the turbocharger but also various gas turbines, steam turbines, etc. Can be used for applications.

(Supercharger 1)
FIG. 1 is a schematic sectional view of the supercharger 1. Below, the direction of the arrow shown by F is set as the front side of the supercharger 1, and the direction of the arrow shown by R is set as the back side of the supercharger 1. As shown in FIG. 1, the supercharger 1 is connected to a bearing housing 2, a turbine housing 4 connected to the front side of the bearing housing 2 by a fastening bolt 3, and a fastening bolt 5 to the rear side of the bearing housing 2. And a compressor housing 6.

  The bearing housing 2 is formed with a bearing hole 2a penetrating in the front-rear direction of the supercharger 1, and a turbine shaft (rotating shaft) 7 is rotatably supported by the bearing hole 2a via a bearing. A turbine impeller 8 is integrally connected to a front end portion of the turbine shaft 7, and the turbine impeller 8 is rotatably accommodated in the turbine housing 4. A compressor impeller 9 is integrally connected to the rear end portion of the turbine shaft 7, and the compressor impeller 9 is rotatably accommodated in the compressor housing 6.

  The turbine housing 4 is formed with a discharge port 10 that opens to the front side of the supercharger 1 and is connected to an exhaust gas purification device (not shown). Further, in a state where the bearing housing 2 and the turbine housing 4 are connected by the fastening bolt 3, a flow path 11 is formed between the opposing surfaces of both the housings 2 and 4. The flow path 11 is formed in an annular shape from the radially inner side to the outer side of the turbine shaft 7 (turbine impeller 8).

  Further, the turbine housing 4 is provided with an annular turbine scroll flow path 12 that is located on the radially outer side of the turbine shaft 7 (turbine impeller 8) than the flow path 11. The turbine scroll channel 12 communicates with a gas inlet (not shown) through which exhaust gas discharged from the engine is guided, and also communicates with the channel 11 described above. Therefore, the exhaust gas led from the gas inlet to the turbine scroll passage 12 is led to the discharge port 10 via the passage 11 and the turbine impeller 8, and a radial velocity component is given in the flow process thereof. The turbine impeller 8 is rotated. The rotational force of the turbine impeller 8 is transmitted to the compressor impeller 9 through the turbine shaft 7.

  The compressor housing 6 is formed with a suction port 13 that opens to the rear side of the supercharger 1 and is connected to an air cleaner (not shown). Further, in a state where the bearing housing 2 and the compressor housing 6 are connected by the fastening bolt 5, a diffuser flow path 14 that compresses and pressurizes air is formed by the facing surfaces of both the housings 2 and 6. The diffuser flow path 14 is formed in an annular shape from the radially inner side to the outer side of the turbine shaft 7 (compressor impeller 9), and communicates with the suction port 13 via the compressor impeller 9 on the radially inner side. ing.

  Further, the compressor housing 6 is provided with an annular compressor scroll passage 15 positioned on the radially outer side of the turbine shaft 7 (compressor impeller 9) with respect to the diffuser passage 14. The compressor scroll passage 15 communicates with an intake port of an engine (not shown) and also communicates with the diffuser passage 14. Therefore, when the compressor impeller 9 rotates, fluid is sucked into the compressor housing 6 from the suction port 13, and the sucked fluid is pressurized by the diffuser flow path 14 and the compressor scroll flow path 15 to be sucked into the engine. Will be led to. Hereinafter, the turbine will be described in detail.

(Turbine)
FIG. 2 is a partially enlarged view of AA in FIG. 1, and FIG. 3 shows the exhaust gas flow from the upstream side to the downstream side (hereinafter simply referred to as the upstream side and the downstream side) in the flow direction of the exhaust gas in the turbine impeller 8. It is explanatory drawing explaining an entropy increase amount. The exhaust gas flowing in from the turbine scroll passage 12 collides with the turbine impeller 8 from the radially outer side to the inner side of the turbine impeller 8 as shown by the solid line arrows in FIG. It is deflected to be exhaled. In this way, the energy (including kinetic energy and pressure energy) of the exhaust gas flowing radially inward is converted into rotational kinetic energy of the turbine impeller 8 around the turbine shaft 7.

  Further, the inner diameter of the turbine housing 4 is once narrowed in the region occupied by the turbine impeller 8 toward the downstream side, and gradually expands from the predetermined turning point 4 a to the discharge port 10. This is because the pressure loss due to the inner wall of the turbine housing 4 is suppressed and the exhaust gas energy is received by the turbine impeller 8 to the maximum by gradually increasing the flow path area from the turning point 4a toward the downstream.

  The turbine impeller 8 is fixed to the turbine shaft 7 and has a turbine wheel 8a formed so as to gradually decrease in diameter toward the downstream side of the turbine shaft 7, and extends radially outward from the turbine wheel 8a. And a plurality of turbine blades 8b arranged at equal intervals.

  Further, the turbine impeller 8 shortens the separation distance from the inner wall of the turbine housing 4 and prevents the exhaust gas from passing through the gap without energy conversion. Therefore, a curved portion (shroud line) 8c facing the inner wall of the turbine housing 4 and a straight portion 8d opened to the discharge port 10 are formed on the radially outer side of the turbine blade 8b.

  Here, as shown by a broken line in FIG. 2, the downstream end portion 8e of the curved portion 8c of the turbine blade 8b is positioned downstream of the turning point 4a, and the linear portion 8d is moved downstream of the turbine shaft 7. It is assumed that the diameter is inclined so as to gradually decrease. As described above, the end portion located on the radially outer side of the turbine blade 8b along the inner wall of the turbine housing 4 is formed so as to increase the flow path area, thereby improving the turbine efficiency particularly in the high rotation region. can do.

  However, in recent years, there are cases in which the turbine efficiency in the low rotation region is prioritized over the high rotation region, such as city riding in vehicles and an idling stop function. Here, when the downstream end portion 8e is located at the position shown by the broken line in FIG. 2, no backflow occurs in the high rotation region, but in the low rotation region, as shown in FIG. 3A, the radial direction of the turbine impeller 8 In the exhaust gas traveling from the outside to the inside, a reverse flow is generated (stagnation) on the inner wall side of the turbine housing 4 in the region 20 where the flow direction is deflected toward the discharge port 10 side, and entropy increases. Here, entropy is an index representing the irreversibility of the adiabatic change, and indicates that the loss increases as entropy increases. It is considered that the reverse flow region is generated because the centrifugal force caused by the rotation of the turbine impeller 8 is smaller than the centrifugal force caused by the curvature of the inner wall of the turbine housing 4 (meridional curvature).

  Therefore, in the present embodiment, the flow path area is configured to be most restricted downstream from the turbine blade 8b. With such a configuration, it is possible to reduce the region where the exhaust gas flows backward and to suppress an increase in entropy due to the backward flow, so that it is possible to improve the turbine efficiency particularly in the low rotation region.

  As a configuration for narrowing the flow path area downstream of the turbine blade 8b, for example, a protrusion is provided on the inner wall of the turbine housing 4 downstream of the turbine blade 8b so as to gradually reduce the inner diameter of the turbine housing 4 toward the downstream side. Can be considered. However, in this case, as the turbine housing 4 is processed, a larger amount of material is required for the turbine housing 4 by the amount of the protruding portion, and the mass also increases.

  Therefore, in the present embodiment, as shown by a one-dot chain line in FIG. 2, the downstream end portion 8 e, which is an end portion located on the downstream side of the curved portion 8 c, has a channel area in a cross section perpendicular to the turbine shaft 7. It is located in a region that gradually decreases as it goes to. In other words, the tangent line 21 projected on the surface (corresponding to the cross section shown in FIG. 2) including the axis of the turbine shaft 7 and the downstream end 8e at the downstream end 8e of the curved portion 8c is downstream. The turbine blade 8b is formed so that the distance from the turbine shaft 7 becomes shorter as it goes.

  FIG. 4 is an explanatory diagram showing changes in the flow path area. When the downstream end portion 8e is located at the position indicated by the broken line in FIG. 2 (hereinafter simply referred to as a comparison target), the flow passage area downstream from the straight portion 8d of the turbine blade 8b gradually increases as indicated by the broken line in FIG. Tend to. On the other hand, when the downstream end portion 8e is located at the position indicated by the alternate long and short dash line in FIG. 2 (hereinafter referred to as the subject of the present application), as indicated by the alternate long and short dashed line in FIG. 4, the downstream portion from the straight portion 8d of the turbine blade 8b. The flow path area of the filter gradually decreases and gradually increases with the turning point 4a as a boundary. Note that the flow path areas of the subject of the present application and the subject of comparison differ on the upstream side of the turbine impeller 8 because the blade angle (bending angle in the circumferential direction of the blade) and the thickness of the blade at the same position are different. .

  In this configuration, for example, the turbine housing 4 other than the turbine impeller 8 can be used as it is, and the downstream end portion 8e of the turbine impeller 8 is a position indicated by a one-dot chain line from a position indicated by a broken line in FIG. It is possible to improve the turbine efficiency in the low rotation region only by retreating to the minimum.

  The entropy loss of the subject of the present application is as shown in FIG. 3B, and the entropy loss is suppressed in the region 20 on the inner wall side of the turbine housing 4 as compared to FIG. 3A, which is the entropy loss of the comparison subject. I understand that.

  Further, when the downstream end 8e is retracted from the position indicated by the broken line in FIG. 2 to the position indicated by the alternate long and short dash line, as shown in FIG. 4, the flow path area at the position of the downstream end 8e is increased. It becomes larger and the maximum flow rate can be increased.

  FIG. 5 is an explanatory diagram showing the relationship between the fluid flow rate and the turbine efficiency. Comparing the subject of the present application with the subject of comparison, it can be understood that the subject of the present subject matter has a lower turbine efficiency peak value compared to the subject of comparison, but the turbine efficiency is higher in the low rotation region where the fluid flow rate is low. It can also be understood that the flow rate (maximum flow rate) at which a predetermined turbine efficiency can be obtained increases in a high rotation region where the fluid flow rate is higher.

  As described above, according to the turbine of the present embodiment, it is possible to improve the turbine efficiency and increase the maximum flow rate particularly in a low rotation region with a simple and low-cost configuration. Further, the tangent projected on the surface including the turbine shaft 7 at the downstream end portion 8e of the curved portion 8c with respect to the convex portion having the turning point 4a of the turbine housing 4 as the apex, and the turbine shaft 7 as it goes downstream. Therefore, the turbine impeller 8 can be easily fitted from the upstream side of the turbine housing 4 and the manufacturing burden can be reduced.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this embodiment. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Is done.

  The present invention can be used in a turbine that converts fluid energy into rotational energy.

DESCRIPTION OF SYMBOLS 1 ... Supercharger 2 ... Bearing housing 4 ... Turbine housing 4a ... Turning point 7 ... Turbine shaft 8 ... Turbine impeller 8a ... Turbine wheel 8b ... Turbine blade 8c ... Curved part 8d ... Linear part 8e ... Downstream end part 10 ... Discharge Outlet 12 Turbine scroll flow path

Claims (2)

A turbine shaft;
A bearing housing that rotatably supports the turbine shaft;
A turbine housing extending from the bearing housing;
A turbine wheel housed in the turbine housing and fixed to the turbine shaft, and a plurality of turbine blades extending radially outward from the turbine wheel, and fluid energy flowing radially inward A turbine impeller for converting the energy into rotational motion energy about the turbine shaft;
With
An end portion of the curved portion located on the downstream side in the fluid flow direction is located in a region where a flow path area of a cross section perpendicular to the turbine axis gradually decreases as the fluid flows in the downstream direction. Turbine. A turbine shaft;
A bearing housing that rotatably supports the turbine shaft;
A turbine housing extending from the bearing housing;
A turbine wheel housed in the turbine housing and fixed to the turbine shaft, and a plurality of curved portions extending radially outward from the turbine wheel and positioned radially outward face the inner wall of the turbine housing. A turbine impeller for converting fluid energy flowing radially inward into energy of rotational motion about the turbine shaft;
With
A tangent line projected on a surface including the axial center of the turbine shaft and the end portion at an end portion of the curved portion located on the downstream side in the fluid flow direction, as the fluid flows toward the downstream in the fluid flow direction. A turbine characterized in that a distance from a turbine shaft is shortened.