JP2008133766A - Turbine impeller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance turbine efficiency by suppressing reduction of a flow speed of a fluid near a leading edge of a turbine blade in a turbine impeller mounted on a radial turbine. <P>SOLUTION: The turbine impeller mounted on the radial turbine for delivering a fluid flowing in from a radial direction perpendicular to a main shaft to a main shaft direction and is provided with a plurality of turbine blades 2 around the main shaft. The turbine blade 2 is designed in shape such that, when it is cut by a plane perpendicular to the main shaft, a linear line tying a blade thickness center passes through the main shaft and the leading edge 26 is curved in a rotation direction of the turbine impeller as it is advanced from a tip part 22 to a hub part 21. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a turbine impeller mounted on a radial turbine that discharges fluid flowing in from a radial direction perpendicular to a main shaft in the main shaft direction.

Conventionally, a camber surface of a plurality of turbine blades provided in a turbine impeller may be three-dimensionalized for the purpose of improving the performance of the turbine.
For example, Patent Document 1 describes a technique for improving the performance of a turbine by, for example, making a camber surface of a turbine blade of an axial flow turbine three-dimensional.
JP 2002-349202 A

By the way, in a radial turbine that discharges fluid flowing in from the radial direction perpendicular to the main shaft in the main shaft direction, when the turbine blades are cut along a plane orthogonal to the main shaft, a straight line connecting the blade thickness centers intersects the main shaft. May be designed to pass.
By designing the turbine blade in this way, the resistance against the centrifugal stress of the turbine blade is improved, so that, for example, a turbine impeller suitable for a turbine on the exhaust gas side of a turbocharger can be designed.

  In such a turbine impeller, as shown in FIG. 8, the trading edge side of the turbine blade is set to a predetermined blade angle (an angle of the camber surface with respect to the main shaft) in order to direct the fluid discharge direction to the main shaft direction. The camber surface is curved. The leading edge of the turbine blade is displaced in the direction opposite to the rotation direction of the turbine impeller as it goes from the tip portion to the hub portion, following the camber surface curvature.

  However, when the leading edge of the turbine blade is displaced in the direction opposite to the rotation direction of the turbine impeller as it goes from the tip portion toward the hub portion, the back side surface of the turbine blade (which faces the rotation direction of the turbine impeller) is particularly important. It was found that when the fluid flows so as to hit the surface, the flow velocity of the fluid near the leading edge decreases due to the incidence loss, and the turbine efficiency decreases.

  The present invention has been made in view of the above-described problems, and in a turbine impeller including a turbine blade in which a straight line connecting the blade thickness centers passes through the main shaft when cut by a plane orthogonal to the main shaft, An object is to suppress a decrease in fluid flow velocity in the vicinity of the leasing edge and improve turbine efficiency.

  In order to achieve the above object, the present invention is a turbine impeller that is mounted on a radial turbine that discharges fluid flowing in from a radial direction perpendicular to the main shaft in the main shaft direction, and includes a plurality of turbine blades installed around the main shaft. When the turbine blade is cut along a plane perpendicular to the main shaft, a straight line connecting the blade thickness centers passes through the main shaft, and the leading edge moves from the tip portion toward the hub portion. It is characterized by being designed to bend in the direction of rotation.

  According to the present invention having such characteristics, the leading edge is curved in the rotational direction of the turbine impeller as it goes from the tip portion toward the hub portion. According to the present invention, a decrease in the flow velocity of the fluid in the vicinity of the leading edge is suppressed as compared with the conventional turbine impeller.

  In the present invention, a configuration is adopted in which the rotation direction angle of the hub portion of the leading edge is within 15 ° with respect to the tip portion of the leading edge.

According to the present invention, the leading edge is curved in the rotational direction of the turbine impeller as it goes from the tip portion toward the hub portion. According to the present invention, a decrease in the flow velocity of the fluid in the vicinity of the leading edge is suppressed as compared with the conventional turbine impeller.
Therefore, according to the present invention, in a turbine impeller having turbine blades in which a straight line connecting the blade thickness centers passes through the main shaft when cut at a plane orthogonal to the main shaft, the flow velocity of the fluid in the vicinity of the leading edge of the turbine blade Reduction can be suppressed and turbine efficiency can be improved.

  Hereinafter, an embodiment of a turbine impeller according to the present invention will be described with reference to the drawings. In the following drawings, the scale of each member is appropriately changed in order to make each member a recognizable size.

FIG. 1 is a side view of a turbine impeller 1 according to the present embodiment. FIG. 2 is a perspective view of a main part of the turbine impeller of the present embodiment.
The turbine impeller 1 is installed in a radial turbine and discharges fluid flowing in from the radial direction in the main shaft L direction. As shown in FIGS. 1 and 2, the turbine impeller 1 is provided with a plurality of turbine blades 2 around a main shaft L.

The turbine blade 2 is set so that a straight line connecting the blade thickness centers always passes through the main shaft L when cut by a plane orthogonal to the main shaft L.
Further, the camber surface 25 on the trading edge 24 side is set at a predetermined angle with respect to the main shaft L so that the fluid discharged from the rotating turbine impeller 1 faces the main shaft direction.
For this reason, the camber surface 25 on the trading edge 24 side of the turbine blade 2 has a configuration curved toward the trading edge 24 toward the direction opposite to the rotational direction of the turbine impeller 1 shown in FIG. .
The trading edge 24 is an end of the turbine blade 2 on the side from which the fluid flows.

Further, at the leading edge 26 which is the end portion of the turbine blade 2 on the fluid inflow side, the rising portion of the turbine blade 2 is the hub portion 21, and the end portion separated from the hub portion 21 is the tip portion 22. The leading edge 26 is curved in the rotational direction of the turbine impeller 1 as it goes from the tip portion 22 toward the hub portion 21.
The camber surface 25 on the leading edge 26 side is curved following the curvature of the leading edge 26, and is smoothly continuous with the camber surface 25 on the trading edge 24 side.
That is, when the turbine impeller 1 of the present embodiment is viewed from the radial direction (the height direction of the turbine blade 2), the shape is substantially S-shaped, and the camber surface 25 is a continuous surface.
In the following description, of the camber surface 25 of the turbine blade 2, a surface facing the rotation direction of the turbine impeller 1 is referred to as a back side surface 251, and a surface facing the direction opposite to the rotation direction of the turbine impeller 1 is defined as a ventral side surface 252. Called.

In the turbine impeller 1 of the present embodiment configured as described above, when a fluid flows between the turbine blades 2 and 2 through the leading edge 26 of the turbine blade 2 from the radial direction, the turbine impeller 1 is changed according to the flow rate of the fluid. The back side 251 or the ventral side 252 of the wing 2 is struck by the fluid.
The fluid struck on the back side 251 or the ventral side 252 of the turbine blade 2 flows along the camber surface 25 and is discharged from the trading edge 24 side of the turbine blade 2. At this time, rotational power is applied to the turbine impeller 1, and the turbine impeller 1 is rotated about the main shaft L.

In the turbine impeller 1 of this embodiment, the leading edge 26 of the turbine blade 2 is curved in the rotational direction of the turbine impeller 1 as it goes from the tip portion 22 toward the hub portion 21.
For this reason, when the fluid flows so as to strike the rear side surface 251 of the turbine blade 2, it is possible to suppress occurrence of incident loss and suppress a decrease in the flow velocity of the fluid in the vicinity of the leading edge 26.
Therefore, according to the turbine impeller 1 of the present embodiment, the turbine efficiency can be improved as compared with the conventional turbine impeller.

  In the present embodiment, the turbine efficiency ηt is an adiabatic efficiency and is defined by the following equation (1). In Equation (1), T1 is the turbine inlet temperature, T2 is the turbine outlet temperature, πt is the expansion ratio, and κ is the specific heat ratio.

  ηt = (1− (T2 / T1)) / (1− (1 / πt) ^ ((κ−1) / κ)) (1)

  Hereinafter, the simulation result of the turbine impeller of this embodiment will be described.

FIG. 3 is a diagram showing the flow of the fluid in the vicinity of the leading edge 100 when the fluid flows into the back side surface of the turbine blade in the conventional turbine impeller (when the fluid is struck on the back side surface).
As shown in FIG. 3, in the conventional turbine impeller, the leading edge 100 is displaced in the direction opposite to the rotation direction of the turbine impeller as it goes from the tip portion to the hub portion, following the camber surface curvature. ing.
As can be seen from this figure, when the fluid flows into the back side surface of the turbine blade in the conventional turbine impeller, the portion where the fluid flow is stagnant can be confirmed in the portion C of the leading edge 100.

On the other hand, FIG. 4 is a diagram showing the flow of fluid in the vicinity of the leading edge 26 when the fluid flows into the back side surface 251 of the turbine blade 2 in the turbine impeller 1 of the present embodiment by arrows. In FIG. 4, the arrow direction indicates the flow direction, and the length indicates the flow velocity.
In the turbine impeller 1 of the present embodiment, the leading edge 26 is curved in the rotational direction of the turbine impeller 1 as it goes from the tip portion 22 toward the hub portion 21 as described above.
As can be seen from this figure, when the fluid flows into the rear side surface 251 of the turbine blade 2 in the turbine impeller of this embodiment, the stagnation of the fluid at the D portion of the leading edge 26 is suppressed.

FIG. 5 is a diagram showing the velocity distribution of the fluid in the vicinity of the leading edge 100 when the fluid flows into the back side surface of the turbine blade in the conventional turbine impeller by contour lines.
FIG. 6 is a diagram showing the fluid velocity distribution in the vicinity of the leading edge 26 when the fluid flows into the rear side surface 251 of the turbine blade 2 in the turbine impeller 1 of the present embodiment by contour lines.
As can be seen by comparing these figures, in the conventional turbine impeller, the fluid velocity is greatly reduced near the leading edge 100, whereas in the turbine impeller 1 of the present embodiment, the leading edge 26 is reduced. A decrease in fluid velocity in the vicinity can be suppressed.

FIG. 7 is a graph showing the turbine efficiency with respect to the flow rate of the fluid supplied to the turbine impeller.
In FIG. 7, a graph A indicated by a solid line indicates the turbine efficiency of a radial turbine provided with the turbine impeller of the present embodiment, and a graph B indicated by a broken line indicates the turbine efficiency of a radial turbine provided with a conventional turbine impeller.
As shown in this figure, it turned out that the radial turbine provided with the turbine impeller 1 of this embodiment can exhibit high turbine efficiency especially in an environment with a small flow rate.

  From the above simulation results, according to the turbine impeller 1 of the present embodiment, when fluid flows so as to strike the back side surface 251 of the turbine blade 2, occurrence of incident loss is suppressed, and the fluid in the vicinity of the leading edge 26 is suppressed. It has been found that the flow rate can be prevented from decreasing, and the turbine efficiency can be improved as compared with the conventional turbine impeller.

Moreover, in the said simulation, it turned out that turbine efficiency improves especially when the rotation direction angle of the hub part 21 of the leading edge 26 is set to 15 degrees or less with respect to the tip part 22 of the leading edge 26.
The rotation direction angle is a rotation angle in the rotation direction of the turbine impeller 1 with the main shaft L as the rotation center.

In the turbine impeller 1 of the present embodiment, the camber surface 25 is curved in different directions with respect to the rotational direction of the turbine impeller 1 on the trading edge 24 side and the leading edge 26 side. A continuous surface extends from the trading edge 24 side to the leading edge 26 side.
For this reason, the flow of the fluid along the camber surface 25 can be made smooth, and it can suppress that a loss component arises.

Note that the turbine impeller 1 of the present embodiment improves the turbine efficiency particularly when fluid is received by the rear side surface 251 of the turbine blade 2.
Therefore, the turbine impeller 1 of the present embodiment is exposed to an environment in which the flow rate of the fluid is variable, and in this environment, receives more fluid on the back side 251 than the ventral side 252 of the turbine blade 2. It is preferable to be installed.

  As mentioned above, although preferred embodiment of the turbine impeller which concerns on this invention was described referring drawings, it cannot be overemphasized that this invention is not limited to the said embodiment. Various shapes, combinations, and the like of the constituent members shown in the above-described embodiments are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

It is a side view of the turbine impeller which is one embodiment of the present invention. It is a principal part perspective view of the turbine impeller which is one Embodiment of this invention. It is the figure which showed the flow of the fluid of the leading edge vicinity in case the fluid flows in into the back side surface of a turbine blade in the conventional turbine impeller by the arrow. It is the figure which showed the flow of the fluid of the leading edge vicinity in case the fluid flows in into the back side surface of a turbine blade in the turbine impeller which is one Embodiment of this invention by the arrow. It is the figure which showed the velocity distribution of the fluid near the leading edge in the case of the fluid flowing in into the back side surface of a turbine blade in the conventional turbine impeller by the contour line. It is the figure which showed the velocity distribution of the fluid of the leading edge vicinity in case the fluid flows in into the back side surface of a turbine blade in the turbine impeller which is one Embodiment of this invention by the contour line. It is a graph which shows the turbine efficiency with respect to the flow volume of the fluid supplied to a turbine impeller. It is a side view of the conventional turbine impeller.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Turbine impeller, 2 ... Turbine blade, 21 ... Hub part, 22 ... Tip part, 24 ... Trading edge, 25 ... Camber surface, 251 ... Back side, 252 ... Ventral side, 26, 100: Leading edge, L: Spindle

Claims (2)

A turbine impeller mounted on a radial turbine that discharges fluid flowing in from a radial direction perpendicular to the main shaft in the main shaft direction, and comprising a plurality of turbine blades installed around the main shaft,
When the turbine blade is cut along a plane perpendicular to the main shaft, a straight line connecting the blade thickness centers passes through the main shaft, and the turbine impeller rotates as the leading edge moves from the tip portion toward the hub portion. A turbine impeller characterized by being designed to bend in a direction. The turbine impeller according to claim 1, wherein a rotation direction angle of the hub portion of the leading edge is within 15 ° with respect to a tip portion of the leading edge.

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