JP5577738B2 - Radial turbine impeller - Google Patents

Description

  The present invention relates to a radial turbine impeller.

In the radial turbine, the impeller is rotationally driven by a fluid supplied from the outside, and the vibration frequency changes according to the rotational speed of the impeller. When the vibration frequency matches the natural frequency of the impeller blade, the impeller blade resonates.
In particular, in a radial turbine having a nozzle vane on the upstream side of the impeller, vibrations having a frequency close to the natural frequency of the impeller blade are generated due to the wake generated downstream of the nozzle vane, and the impeller blade is resonated. .

  Conventionally, in order to suppress such damage due to resonance of the impeller blade, the natural frequency (especially the secondary natural frequency) of the impeller blade is lowered and the impeller is rotated at a low speed (that is, at a low speed of the impeller blade). Measures are taken to vibrate the impeller blades.

JP-A-8-246801

  Although the risk of destruction is reduced by resonating the impeller blades when the impeller is low in rotation and the impeller blades are low speed, the impeller blades still resonate. For this reason, conventionally, sufficient rigidity is provided so that the impeller blades are not damaged even when they resonate.

  However, generally, increasing the rigidity of a member increases the natural frequency of the member. For this reason, the conventional impeller blades require complicated processing such as controlling the thickness of the impeller blades precisely by changing the location in order to increase the rigidity and reduce the natural frequency.

On the other hand, if the natural frequency of the impeller blades can be raised and the natural frequency of the impeller blades can be made higher than the vibration frequency in the operating region of the radial turbine, the impeller blades are prevented from resonating in the operating region of the radial turbine. It becomes possible. As a result, it is not necessary to perform the complicated processing described above, and the required rigidity level can be reduced.
For this reason, provision of the technique which raises the natural frequency of an impeller blade is calculated | required. In particular, since the impeller blade has a large amplitude when resonating at the secondary natural frequency and easily leads to breakage, provision of a technique for increasing the secondary natural frequency of the impeller blade is required.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a technique for increasing the secondary natural frequency of an impeller blade in an impeller of a radial turbine.

  The present invention adopts the following configuration as means for solving the above-described problems.

  A first invention is an impeller of a radial turbine, and is provided at a tip side of a meridian surface of an impeller blade at a tip side with respect to a hub, and has a radial distance shorter than a radial distance from an impeller rotating shaft to the hub. A configuration is adopted in which a short radius distance region located at is provided.

  According to a second invention, in the first invention, the entire area closer to the tip than the hub is the short radius distance area, and the leading edge is inclined at a constant angle with respect to the impeller rotation axis. Adopt the configuration.

  According to a third aspect, in the second aspect, the inclination angle of the leading edge with respect to the impeller rotation shaft is such that the secondary natural frequency of the impeller blade is higher than the vibration frequency in the operating region of the radial turbine. The configuration that is set to is adopted.

  According to a fourth invention, in the second or third invention, a configuration is adopted in which an inclination angle of the leading edge with respect to the impeller rotating shaft is larger than 0 ° and not larger than 9 °.

According to the present invention, by providing a short radius distance region at the leading edge of the meridian surface of the impeller blade, a partial region of the leading edge approaches the impeller rotation axis, and the rigidity of the leading edge that is most likely to vibrate by resonance is increased. .
That is, according to the present invention, the rigidity of the leading edge can be increased, and thereby the secondary natural frequency of the impeller blade can be increased.

It is a schematic diagram which shows schematic structure of the impeller of the radial turbine of one Embodiment of this invention, and has shown the meridian surface of the impeller blade. It is a schematic diagram which overlaps and shows the leading edge shape of the impeller blade which performed the simulation. It is the table | surface and graph which put together the simulation result. It is a graph which shows the relationship between the flow volume parameter obtained by aerodynamic performance analysis, and turbine efficiency.

  Hereinafter, an embodiment of a radial 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 schematic diagram showing a schematic configuration of the impeller 1 of the radial turbine of the present embodiment, and shows a meridian surface of the impeller blade 3.

  The impeller 1 is disposed inside the housing of the radial turbine, and obtains rotational power by being rotated by a fluid flowing in the housing, and includes a base portion 2 and impeller blades 3.

The base portion 2 serves as a rotation center portion of the impeller 1 and has a rotating body shape having a rotation axis L (impeller rotation axis) shown in FIG. 1 as a rotation center.
The side surface 2 a of the base portion 2 has a curved shape that is convex toward the rotation axis L. And the base part 2 has a shape which narrows toward the front-end | tip 2b.

  The impeller blades 3 rotate the base portion 2 by receiving a fluid, and a plurality of impeller blades 3 are arranged at predetermined intervals in the rotation direction of the impeller 1 and attached to the side surface 2 a of the base portion 2.

  In the impeller 1 of the present embodiment, the direction in which the rotation axis L extends is the axial direction, the direction orthogonal to the axial direction is the radial direction, and the direction in which the tip 2b of the base portion 2 faces in the axial direction. The backward direction is the forward direction.

As shown in FIG. 1, the impeller blade 3 has a front edge 3 a disposed on the front side in the axial direction and radially outward on the meridian surface, and a rear edge 3 b disposed in the axial direction. It arrange | positions toward the back of an axial direction while arrange | positioning at the back side.
That is, the impeller blade 3 has a shape curved from the radial direction to the axial direction (that is, along the side surface 2a of the base portion 2) from the front edge 3a to the rear edge 3b.

In the impeller blade 3, the end on the base part 2 side (the part connected to the base part 2) is the hub 3c, and the end far from the base part 2 is the tip 3d.
Here, since the impeller blade 3 is curved as described above, the hub 3 c and the tip 3 d are curved along the side surface 2 a of the base portion 2.

  In the impeller blade 3 of the radial turbine of the present embodiment, as shown in FIG. 1, the leading edge 3a on the meridian surface of the impeller blade 3 is inclined with respect to the rotation axis L so that the tip 3d side faces the rotation axis L. Has been.

  More specifically, in the impeller 1 of the radial turbine of the present embodiment, as shown in FIG. 1, the rotational axis L is greater than the radial distance L1 from the rotational axis L to the hub 3 c at the leading edge 3 a of the impeller blade 3. A radial distance L2 from the tip to the chip 3d is set short. The front edge 3a is inclined with respect to the rotation axis L so as to connect the hub 3c and the chip 3d with a straight line.

  That is, in the impeller 1 of the radial turbine according to the present embodiment, the entire region on the tip 3d side of the front edge 3a on the meridian surface is shorter than the radial distance L1 from the rotation axis L to the hub 3c. Located in the direction distance.

  And the area | region located in radial direction distance shorter than radial direction distance L1 from the rotating shaft L to the hub 3c in the front edge 3a in a meridian surface is equivalent to the short radial distance area | region in this invention.

In other words, the impeller 1 of the radial turbine of the present embodiment is provided on the tip 3d side of the front edge 3a on the meridional surface of the impeller blade 3 more than the hub 3c, and is more than the radial distance L1 from the rotation axis L to the hub 3c. It has a short radius distance region located at a short radial distance.
By providing such a short radius distance region, a part of the leading edge 3a that swings greatly especially when resonating at the secondary natural frequency approaches the rotation axis L, and the radial length of the impeller blade 3 is shortened. The rigidity of the leading edge 3a can be increased.

  In the radial turbine impeller 1 of the present embodiment, the short radius distance region α is the entire region on the tip 3d side of the hub 3c except for the hub 3c of the leading edge 3a, as shown in FIG. ing.

  According to the impeller 1 of the radial turbine of the present embodiment having such a configuration, a fluid flows from the front edge 3a of the impeller blade 3 toward the rear edge 3b, and the impeller blade 3 performs work by receiving this fluid. Thus, the base portion 2 is rotationally driven.

  And according to the impeller 1 of the radial turbine of this embodiment as described above, the rigidity of the leading edge 3a that is most likely to vibrate by resonance is increased by the short radius distance region α. As a result, the secondary natural frequency of the impeller blade 3 as a whole can be increased.

As described above, the leading edge 3a on the meridian surface of the impeller blade 3 is inclined with respect to the rotation axis L at a constant angle. The secondary natural frequency of the impeller blade 3 increases as the inclination angle of the leading edge 3a with respect to the rotation axis L increases. For this reason, the inclination angle of the leading edge 3a with respect to the rotation axis L is set so that the secondary natural frequency of the impeller blades 3 is higher than the vibration frequency in the operating region of the radial turbine in consideration of the efficiency of the radial turbine. It is preferably set.
As a result, when the radial turbine is operating, the vibration frequency does not match the secondary natural frequency of the impeller blade 3, and the resonance of the impeller blade 3 can be suppressed.

Next, the change in the natural frequency due to the inclination angle of the leading edge 3a of the impeller blade 3 with respect to the rotation axis L will be described based on the simulation result.
As shown in FIG. 2, in this simulation, the inclination angle of the leading edge 3a with respect to the rotation axis L was changed, and the natural frequency of the impeller blade 3 at that time was obtained.
More specifically, in this simulation, an impeller blade whose front edge 3a is parallel to the rotation axis L shown in FIG. 2 is set to base (θ = 0 °), and the front edge 3a is 3 to the rotation axis L. An impeller blade inclined at ° is case A (θ = 3 °), an impeller blade whose front edge 3a is inclined at 5 ° with respect to the rotation axis L is case B (θ = 5 °), and the front edge 3a Impeller blades inclined at 7 ° with respect to the rotation axis L are referred to as case C (θ = 7 °), and impeller blades whose leading edge 3a is inclined at 9 ° with respect to the rotation axis L are referred to as case D (θ = The natural frequency was determined as 9 °).

  In this simulation, the number of impeller blades was 10 and the node diameter was 1. The node diameter is indicated by a vibration node that appears as a line (diameter) that bisects the impeller blade disk.

FIG. 3 is a table and a graph summarizing the simulation results. As shown in this figure, the secondary natural frequency (f2) ratio in case A is 101.03% of the secondary natural frequency (f2) ratio in base, and the secondary natural frequency (f2) in case B. ) Ratio is 101.74% of the secondary natural frequency (f2) ratio in base, and the secondary natural frequency (f2) ratio in case C is 102.45 of the secondary natural frequency (f2) in base. %, The secondary natural frequency (f2) ratio in Case D was 103.23% of the secondary natural frequency (f2) ratio in base.
That is, it was confirmed that the secondary natural frequency (f2) ratio of the impeller blade 3 increases as the inclination angle of the leading edge 3a with respect to the rotation axis L increases.

  Next, aerodynamic performance analysis was performed on the base and cases A to D, and the turbine efficiency was determined and compared. In this aerodynamic performance analysis, the turbine pressure ratio is πt = 2.

FIG. 4 is a graph showing the relationship between the flow rate parameter obtained by the aerodynamic performance analysis and the turbine efficiency.
As can be seen from this figure, by using the impeller 1 of the radial turbine of the above embodiment, the efficiency is the same as that of the conventional radial turbine on the small flow rate side and the efficiency higher than that of the conventional radial turbine on the large flow rate side. It turns out that it is obtained.
Therefore, in the impeller 1 of the radial turbine of the above embodiment, the leading edge 3a is inclined at a constant angle with respect to the rotation axis L, and this inclination angle is set to 9 ° or less without reducing the efficiency of the radial turbine. The secondary natural frequency of the impeller blade 3 can be increased.

  As mentioned above, although preferred embodiment of this invention was described referring drawings, 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.

For example, in the above embodiment, the configuration has been described in which the front edge 3a is inclined at a constant angle, and the entire region on the tip 3d side excluding the hub 3c is a short radius distance region.
However, the present invention is not limited to this, and a configuration in which only the middle portion of the front edge 3a is a short radius distance region or a configuration in which only the tip side from the center of the front edge 3a is a short radius distance region is adopted. It is also possible to do.

  DESCRIPTION OF SYMBOLS 1 ... Radial turbine impeller, 2 ... Base part, 3 ... Impeller blade, 3a ... Front edge, 3b ... Rear edge, 3c ... Hub, 3d ... Tip, L ... Rotating shaft, α ... ... Short radius distance region

Claims (2)

A radial turbine impeller,
Provided at the leading edge of the meridian surface of the impeller blade on the tip side of the hub, and having a short radius distance region located at a radial distance shorter than the radial distance from the impeller rotation shaft to the hub ,
The entire region on the tip side from the hub is the short radius distance region, the front edge is inclined at a constant angle with respect to the impeller rotation axis, and the inclination angle of the front edge with respect to the impeller rotation axis is An impeller for a radial turbine, wherein a secondary natural frequency of the impeller blade is set to be higher than a vibration frequency in an operating region of the radial turbine. Angle of inclination with respect to the impeller rotation axis of the leading edge, a radial turbine impeller according to claim 1, wherein a is less than or equal to 0 ° greater than 9 °.

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