JP5518236B2 - Turbine blade - Google Patents

Description

  The present invention relates to a moving blade in a radial turbine such as a turbocharger or a mixed flow turbine, and particularly relates to a back surface shape of the moving blade.

  In a turbine blade of a turbocharger for vehicles, ships, etc., if the moment of inertia of the turbine blade is large, as shown in FIG. 7, the responsiveness of the rise of the engine speed and the rise of the supply air pressure is deteriorated. In addition, there is a problem of generating a time lag of the entire engine system including the turbocharger.

For this reason, as a method for lowering the moment of inertia of the turbine rotor blade, a method for adjusting the blade shape itself by cutting or the like is known.
For example, in order to reduce the height of the trailing edge 03 of the blade 01 as shown in FIG. 8, a method of lowering the shroud line 05 on the outer periphery of the blade 01, or the thickness of the blade 01 as shown in FIG. A method of reducing the thickness to 01 'or a method of reducing the overall height of the blade 01 to the leading edge 07 to make a turbine with a small diameter is known.

  However, if the height of the trailing edge 03 of the blade 01 is reduced or the thickness of the blade 01 is reduced, there is a possibility that the efficiency of the turbine blades may not be satisfied or the strength requirements may not be satisfied. In the case of applying the turbocharger, in particular, in the turbocharger, it is necessary to escape the flow rate difference between the maximum torque point and the maximum output point, which causes a problem that the efficiency of the entire system is lowered.

  Therefore, as a method for reducing the moment of inertia without changing the blade shape, a proposal has been made to form a hollow concave shape on the back surface of the moving blade.

For example, in Patent Document 1 (Japanese Patent Laid-Open No. 10-54201), as shown in FIG. 10, an axial annular recess 017 is formed on an end surface 016 of a hub 015 on which a blade 013 of a turbine rotor blade 011 is provided. Has been.
Further, in Patent Document 2 (Japanese Utility Model Laid-Open No. 63-83430), as shown in FIG. 11, an axial annular recess 026 is provided on an end face 025 of a hub 024 on which a blade 022 of a turbine rotor blade 020 is provided. Is formed. The recesses 026 are provided at four locations in the circumferential direction along the axial direction, and the cross-sectional shape is formed in a substantially triangular shape.

JP-A-10-54201 Japanese Utility Model Publication No. 63-83430

However, in Patent Document 1 and Patent Document 2, it is possible to improve the responsiveness by reducing the moment of inertia by the hollow concave shape. However, in Patent Document 1, the tip of the concave shape in FIG. No. 019 has a small curvature radius and is likely to cause stress concentration due to a sudden change in curvature. Also in Patent Document 2, stress concentration tends to occur at the concave tip portion 028 of FIG. 11 due to a sudden change in curvature.
For this reason, stress concentration tends to occur at the root portion of the rear surface of the rotor blade of the hub member, and there is a problem in terms of strength and durability.

  Therefore, the present invention has been made in view of these problems, reducing the moment of inertia of the moving blade without changing the blade shape, and suppressing the occurrence of stress concentration at the root portion of the rear surface of the moving blade. It is an object of the present invention to provide a turbine rotor blade having a rotor blade rear surface shape capable of improving durability.

In order to solve the above-described problem, the first invention (reference) of the present application integrally forms a shaft-shaped hub portion to which a rotating shaft is coupled and a plurality of blade portions formed around the hub portion. In turbine blades,
The hub portion has a shape that gradually increases in diameter toward the back surface, which is one end side in the rotation axis direction, and an annular concave shape portion is formed on the back surface around the rotation shaft center. The cross-sectional shape in the rotational axis direction is formed by a curved shape obtained by dividing an elliptical or oval long-axis symmetrical curve shape by the long axis, and the position of the long axis coincides with the back surface. It is characterized by that.

According to this invention, the hub portion has a shape that gradually increases in diameter toward the back surface that is one end side in the rotation axis direction, the annular concave portion is formed on the back surface, and the cross-sectional shape thereof is elliptical. Is formed by a curved shape obtained by dividing a long axis symmetrical curve shape of the shape or egg shape by the long axis, and the position of the long axis coincides with the back surface, so that the curvature of the concave portion is smooth , The radius of curvature can be increased, and the stress concentration generated in the concave portion is greater than the stress concentration caused by the sudden curvature change at the concave tip portion as shown in FIGS. Can be reduced.
As a result, it is possible to avoid stress concentration at the root portion of the rear surface of the moving blade and to improve strength and durability. Moreover, the moment of inertia of the turbine rotor blade can be reduced by the thinning by the annular concave portion.

  In general, the stress concentration factor α has a relationship as shown in FIG. 6, and the stress concentration factor α decreases as ρ (notch arc radius) / t (notch depth) indicated on the horizontal axis increases. Therefore, the stress concentration coefficient α can be reduced by increasing ρ (the arc radius of the notch) or decreasing t (the notch depth).

  Therefore, as in the present invention, the cross-sectional shape of the concave portion is formed by a curved shape obtained by dividing the long axis symmetrical curve shape such as an ellipse or an oval by the long axis, and the position of the long axis matches the back surface By forming as described above, the stress concentration coefficient in the concave shape portion can be made smaller than the sudden curvature change in the concave shape tip portion as in the prior art, and ρ (arc radius of the notch) is increased, t (notch depth) can be reduced, and stress concentration at the root portion of the moving blade at the back of the hub portion can be reduced.

  According to a second aspect of the present invention, there is provided a turbine rotor blade in which a shaft-shaped hub portion to which a rotating shaft is coupled and a plurality of blade portions formed around the hub portion are integrally formed. It has a shape that gradually increases in diameter toward the back surface, which is one end side in the axial direction, and an annular concave portion is formed on the back surface around the center of the rotation axis. The cross-sectional shape is a part of an arc or an elliptical or oval long axis symmetrical curve shape, and the center of the arc or the position of the long axis is located outside the hub portion from the back surface, and the long axis Is formed so as to be parallel to the back surface.

  According to the second invention, the stress concentration coefficient can be reduced and the stress concentration can be reduced as in the first invention (reference). Moreover, in the second invention, the long axis forming the center of the arc or the long axis symmetric curved shape is positioned outside the hub portion from the back surface, so the long axis symmetric curved shape in the first invention (reference) The radius of curvature can be set to be larger than the radius of curvature, and the stress concentration coefficient can be further reduced as compared with the first invention (reference), and the stress concentration at the root portion on the back surface of the hub portion can be further reduced.

  In the first invention (reference) and the second invention, it is preferable that the position on the outer peripheral side of the intersection of the back surface and the circular arc or the long axis symmetrical curve shape is positioned at approximately half the wing part diameter. The inner peripheral position may be positioned in the vicinity of the intersection between the back surface and the rotation shaft.

According to such a configuration, since the position on the outer peripheral side of the intersection of the back surface of the hub portion and the circular arc or the long axis symmetrical curve shape is located at a position approximately half the wing portion diameter, the hub that holds the wing portion A sufficient thickness can be secured in the portion on the outer periphery side.
In addition, the hub and wings are manufactured integrally by casting, etc., and rotate at a high speed, so a space for removing the thickness for balancing is required. A plane part can be left on the outer peripheral side of the part.

In the first invention (reference) and the second invention, it is preferable that the cross-sectional shape of the concave portion does not include a straight portion.
In other words, since it is formed only by a long axis symmetrical curve shape such as an arc shape or an elliptical shape, the possibility of stress concentration due to shape change at the intersection of the straight line portion and these curved shapes is avoided as much as possible when a straight line portion is interposed It is possible to effectively suppress the occurrence of stress concentration at the root portion of the back surface.

Further, in the first invention (reference) and the second invention, preferably, the long axis symmetrical curve shape is an ellipse, and the minor axis of the ellipse may be 3 to 10% of the diameter of the moving blade.
Such 3 to 10% is based on the results of numerical analysis of stress and moment of inertia, and if it becomes smaller than 3%, the effect of reducing the moment of inertia due to the hollowing out as a concave shape cannot be obtained. The depth becomes deeper and affects the wall thickness of the outer peripheral side of the hub portion that holds the blade portion, and adversely affects the strength of the entire turbine blade, so it is preferable to set this range.

According to the first invention (reference), the strength and durability can be improved by reducing the moment of inertia of the moving blade without changing the blade shape and suppressing the occurrence of stress concentration at the root portion of the moving blade back surface. It is possible to provide a turbine rotor blade having a rear surface shape that can be used.
Further, according to the second invention, the stress concentration factor can be reduced and the stress concentration can be reduced as in the first invention (reference).
Moreover, in the second invention, the long axis forming the center of the arc or the long axis symmetrical curve is positioned outside the hub portion from the back surface, so the long axis symmetrical curve in the first invention (reference) A radius larger than the curvature radius of the shape can be set, and the stress concentration factor can be made smaller than that of the first invention (reference), and the stress concentration at the root portion on the back surface of the hub portion can be further reduced. .

It is sectional drawing of the turbine rotor blade in 1st Embodiment (reference) of this invention. It is sectional drawing of the turbine rotor blade in 2nd Embodiment. It is sectional drawing of the turbine rotor blade in 3rd Embodiment. It is comparison explanatory drawing of a stress peak ratio and a moment of inertia. It is explanatory drawing of the comparative examples 1 and 2 shown in FIG. It is a general characteristic figure of stress concentration factor alpha. It is explanatory drawing which shows the response characteristic of a turbine rotor blade. It is explanatory drawing of the example of a change of wing | blade shape. It is explanatory drawing of the example of a change of wing | blade shape. It is explanatory drawing of a prior art. It is explanatory drawing of a prior art.

  Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this embodiment are not intended to limit the scope of the present invention to that unless otherwise specified.

(First embodiment (reference))
A description will be given of a turbine blade of a turbocharger for vehicles, ships, etc. as an example. FIG. 1 shows an axial sectional view of the turbine rotor blade 1. A turbine rotor blade (hereinafter referred to as a rotor blade) 1 is formed in an axial shape, and has an outer peripheral side surface 3, a front end surface 5, and a rear end surface (rear surface) 7. A hub portion 9 having a wing portion and a plurality of blade portions 11 formed on the outer peripheral side surface 3 of the hub portion 9 are integrally formed by injection molding, casting, sintering, or the like.

The outer peripheral side surface 3 is formed in a curved shape so as to gradually increase in diameter from the front end surface 5 to the back surface 7 of the hub portion 9, and a plurality of wing portions 11 are formed along the axial direction on the curved surface. It is erected.
And the front edge 13 of the wing | blade part 11 is provided in the outer peripheral side toward radial direction, the rear edge 15 of the wing | blade part 11 is formed in the inner peripheral side toward axial direction, and a flowing gas is a front edge from radial direction outer side. 13 and discharged from the rear edge 15 in the axial direction, a rotational force is generated in the hub portion 9.

  Further, a welding shelf 17 that connects the rotating shaft 19 is provided on the rear surface 7 so as to protrude in a circumferential shape, and the tip of the rotating shaft 19 is coupled to the welding shelf 17 by a welding portion 22. The connecting structure of the rotating shaft 19 may be a structure in which the central portion of the hub portion 9 is formed in a hollow shape without being welded, and the rotating shaft is fitted into the hollow shape and coupled.

  Further, an annular concave portion 21 is formed around the rotation axis 19 around the center line L on the back surface 7 of the hub portion 9. As shown in FIG. 1, the cross-sectional shape of the concave portion 21 in the rotation axis direction is an ellipse (long-axis symmetrical curve shape) G. That is, it is formed by an elliptical long arc C composed of an elliptical minor axis a and a major axis b. The elliptical arc C of the ellipse has a shape divided by the major axis b so that the major axis b of the major axis coincides with the surface of the back surface 7. That is, the curved shape forming the concave portion 21 is formed by a single elliptical long arc C having no straight portion.

The position of the intersection point A on the outer peripheral side of the long arc C and the back surface 7 is positioned at approximately half of the diameter D of the wing part 11, and the position of the intersection B on the inner peripheral side is between the upper surface of the welding shelf 17 and the back surface 7. Is located at the intersection where
Since the position of the intersection A is located at a position approximately half the diameter D of the wing part 11, a sufficient thickness N can be secured in the outer peripheral side portion of the hub part 9 holding the wing part 11, and the concave part By forming 21, the strength of the entire turbine rotor blade 1 can be prevented from being lowered.
In addition, the hub portion 9 and the blade portion 11 are integrally manufactured by casting or the like, and the rotor blade 1 itself rotates at a high speed. Although necessary, a plane H is secured on the outer peripheral side of the concave portion 21 of the back surface 7 as the space.

  Based on this reason, the position of the intersection A is set. In addition, for the intersection B, the inner surface of the concave-shaped portion 21 is continuously and smoothly connected to the upper surface of the welding shelf portion 17 so that the occurrence of stress concentration can be reduced as much as possible. That is, if the position of the intersection point B is positioned on the outer peripheral side in a stepped manner from the upper surface of the welding shelf 17, a corner portion is formed at the intersection point B, and stress concentration may occur there.

  Here, the stress concentration factor will be described. In general, the stress concentration coefficient α has a relationship as shown in FIG. 6 in the material mechanics literature (Mechanical Engineering Handbook). This example shows the case of notches on both sides, but the stress concentration factor α has a relationship that decreases as ρ (arc radius of the notch) / t (notch depth) indicated on the horizontal axis increases. is there. For this reason, it can be seen that the stress concentration factor α can be reduced by increasing ρ (the radius of the arc of the notch) or by decreasing t (the depth of the notch).

Therefore, in order to increase ρ (notch arc radius) or to reduce t (notch depth), the stress concentration coefficient is obtained by forming the cross-sectional shape of the concave portion 21 with an elliptical arc shape. Can be made smaller than the sudden curvature change at the concave tip portion as in the prior art, and the back surface 7 can be thinned.
As a result, it is possible to reduce the moment of inertia of the moving blade 1 without changing the shape of the blade portion 11 and to suppress the occurrence of stress concentration at the root portion of the back surface 7 and improve the strength and durability. .

Next, the numerical analysis result of the stress generated in the base portion of the back surface 7 will be described with reference to FIGS.
Comparative Example 1 on the horizontal axis of FIG. 4 is a case of a turbine rotor blade 30 in which a concave portion is not formed as shown in FIG. 5A, and Comparative Example 2 is as shown in FIG. 5B. 10 and 11 described as the prior art with the water droplet shape 32 as the cross-sectional shape of the concave portion, and the turbine rotor blade 34 having a sharp shape with a deep concave shape and a small curvature radius at the tip. This is the case. Examples 1 to 4 are cases in which the elliptical long arc shape shown in FIG. 1 of the present embodiment is used, and Example 1 has a ratio (D / a) of the diameter D of the wing part 11 to the minor axis a of the ellipse. In the case of 10%, Example 2 shows a case where D / a is 6%, Example 3 shows a case where D / a is 5%, and Example 4 shows a case where D / a is 4%.
The vertical axis indicates the ratio when the stress peak value of Comparative Example 2 is 100% and the ratio when the inertia moment of Comparative Example 1 is 100%.

  When each case is compared based on this FIG. 4, as for the stress peak value, in the case of the concave portion of the water droplet shape of Comparative Example 2, the stress peak value is the largest and the value is 100%. It was found that Comparative Example 1 is the smallest because no concave-shaped portion is formed, and becomes smaller sequentially in Examples 1 to 4. In other words, it was confirmed that the base was closer to Comparative Example 2 as the minor axis a of the ellipse became smaller and the depth of the concave portion became shallower.

  As for the moment of inertia, the comparative example 1 having no concave portion is the largest, and the value thereof is set to 100%. In other cases, the comparative example 2 having the water droplet shape is the smallest, and gradually increases from the first to fourth examples. I found out that In other words, it was confirmed that the base was closer to Comparative Example 1 as the minor axis a of the ellipse became smaller and the depth of the concave portion became shallower.

From the above comparison, those in which the concave portion is not formed as in Comparative Example 1 have a small concentrated stress but a large moment of inertia, and in the shape of a water droplet shape as in Comparative Example 2, the inertia is small. Although the moment was small, it was confirmed that large concentrated stress was generated.
In the present invention, intermediate characteristics between the comparative example 1 and the comparative example 2 can be obtained, and the occurrence of stress concentration at the root portion of the back surface 7 can be suppressed while reducing the moment of inertia. .

In addition, about the setting of the ratio of D / a, since it has the relationship between an inertia moment and peak stress as shown in Examples 1-4, it is good to set beforehand by the use conditions of a turbine rotor blade. Further, the range of the ratio of D / a is appropriately 3 to 10% including 4 to 10% shown in FIG. 4 from the numerical analysis results of stress and moment of inertia.
This is because if it becomes smaller than 3%, the effect of reducing the moment of inertia due to the hollowing out as a concave shape cannot be obtained, and if it exceeds 10%, the depth becomes too deep, and the outer peripheral side of the hub part holding the wing part becomes too deep. Since this affects the wall thickness of the portion and adversely affects the strength of the entire turbine rotor blade, it should be set within this range.

  In 1st Embodiment (reference), although elliptical G was demonstrated as a cross-sectional shape of the concave-shaped part 21, the same thing can be said also about the oval approximated to the ellipse as a long-axis symmetrical curve. In other words, the oval curve shape is a shape that connects an ellipse and a semicircular arc, and the curvature of the concave portion changes smoothly even if it is not only an ellipse but also a shape connected to an arc, and the radius of curvature is increased. Any shape that can be taken large may be used. However, the straight portion should not exist, that is, the curvature of the concave portion changes smoothly by being formed only by a long axis symmetrical curve shape such as an arc shape or an elliptical shape. This is because if a straight line portion is interposed, a shape change is likely to occur at the intersection between the straight line portion and these curved shapes, and stress concentration is likely to occur.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the same component as demonstrated in 1st Embodiment (reference), and description is abbreviate | omitted.
As shown in FIG. 2, the cross-sectional shape of the annular concave portion 44 formed on the back surface 42 of the hub portion 40 around the center line L of the rotation shaft 19 is an elliptical shape G ′. Thus, it is formed by an elliptical long circular arc E having a short diameter a ′ and a long diameter b ′. The elliptical long arc E does not match the major axis b ′ with the back surface 42. It is located at a position moved from the surface position of the back surface 42 in the outward direction of the hub portion 40 by a distance s, and is formed by a part of an elliptical long arc shape. In other words, the curved shape forming the concave portion 44 is formed by a single elliptical long arc without a straight portion.

Further, as the distance s largely moves, the major axis b ′ can be increased, so that the distance s can be made closer to the base shape of the comparative example 1 of FIG. 4 described in the first embodiment (reference). become.
As for the moving direction of the distance s, when moving in the inner direction of the hub portion 40 and the major axis b ′ of the major axis is located in the hub portion 40, the portion directly on the upper and lower sides of the cross-sectional shape of the concave portion 44. Therefore, the distance s is moved from the position of the back surface 42 to the outside of the hub portion 40 (left side in FIG. 2). There is a need.
The position of the intersection A on the outer peripheral side of the long arc E and the back surface 42 and the position of the intersection B on the inner peripheral side are the same as in the first embodiment (reference).

  According to the second embodiment, the stress concentration coefficient can be reduced and the stress concentration can be reduced as in the first embodiment (reference). In addition, in the second embodiment, the position of the major axis b ′ of the ellipse is positioned outside the hub portion 40 from the back surface 42, so that it is set larger than the radius of curvature of the ellipse major arc C in the first embodiment (reference). Therefore, compared to the first embodiment (reference), the stress concentration coefficient can be further reduced, and the stress concentration at the root portion of the back surface 42 can be further reduced.

(Third embodiment)
Next, a third embodiment will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the same thing as the structural member demonstrated in 1st Embodiment (reference) and 2nd Embodiment, and description is abbreviate | omitted.
In the third embodiment, the shape of the concave portion 50 is formed by a circular arc with respect to the ellipse of the second embodiment.

  As shown in FIG. 3, the cross-sectional shape of the annular concave portion 50 formed around the center line L of the rotating shaft 19 on the back surface 54 of the hub portion 52 of the rotor blade 1 has a radius R as shown in FIG. It has an arc shape and is formed by a partial arc F of the circumference. The center P of the arc F is located at a position moved from the surface position of the back surface 54 to the outside of the hub portion 52 by a distance s, as in the second embodiment. That is, the curved shape forming the concave portion 50 is formed by a single arc without a straight line portion, and is formed by an arc shape smaller than the semicircular arc.

  The position of the intersection point A on the outer peripheral side of the arc F and the back surface 54 and the position of the intersection point B on the inner peripheral side are the same as in the first embodiment (reference).

  According to this 3rd Embodiment, since the same effect as 2nd Embodiment can be obtained, and since the concave shape part 50 is formed using the curve of a part of circular arc, an ellipse or egg Manufacture and processing are easier than the cross-sectional shape of a long axis symmetrical curved shape such as a shape. Further, when the distance between the points A and B is constant and the projection amount of the welding shelf 17 is limited, the long axis symmetry such as an oval shape or an oval shape is provided so as not to be applied to the welding portion 22. The degree of freedom in setting the shape of the concave-shaped portion 50 is improved, for example, it is possible to set a smaller radius of curvature than the curvature radius of the curved shape.

  The present invention provides a blade rear surface shape that can reduce the moment of inertia of the blade without changing the blade shape and suppress the occurrence of stress concentration at the root portion of the blade rear surface, thereby improving the strength and durability. Therefore, it is suitable for use in turbine blades.

DESCRIPTION OF SYMBOLS 1 Turbine blade 9 Hub part 5 Front end surface 7, 42, 54 Back surface 11 Wing part 17 Welding shelf part 19 Rotating shaft 21, 44, 50 Concave-shaped part 22 Welding part A Intersection of concave-shaped part and back surface B Back surface and rotation Intersection with axis C, E Ellipse long circular arc D Wing diameter F Arc G, G 'Ellipse L Center line N Thickness H Plane S Distance P Center of arc

Claims (4)

In a turbine rotor blade integrally formed with a shaft-shaped hub portion to which a rotating shaft is coupled and a plurality of blade portions formed around the hub portion,
The hub portion has a shape that gradually increases in diameter toward the back surface, which is one end side in the rotation axis direction, and an annular concave shape portion is formed on the back surface around the rotation shaft center. The cross-sectional shape in the direction of the rotation axis is a part of an arc or an elliptical or oval long-axis symmetrical curve, and the center of the arc or the position of the long axis is located outside the hub portion from the back surface. In addition, the turbine rotor blade is characterized in that the long axis is formed in parallel with the back surface.   The position on the outer peripheral side of the intersection of the back surface and the circular arc or the long axis symmetric curved shape is positioned at approximately half of the wing diameter, and the position on the inner peripheral side is in the vicinity of the intersection of the back surface and the rotating shaft. The turbine rotor blade according to claim 1, wherein   The turbine rotor blade according to claim 1, wherein a straight portion does not exist in a cross-sectional shape of the concave portion. The turbine rotor blade according to claim 1, wherein the major axis symmetrical curve shape is an ellipse, and a minor axis of the ellipse is 3 to 10% of a diameter of the rotor blade.

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