JPS6133967B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a group wing structure. In particular, the present invention relates to a blade group structure configured by arranging two or more rotor blades operated by fluid.

This type of structure is used as a structure for moving blades of axial flow machines, such as steam turbines, gas turbines, and axial flow compressors.

Conventional rotor blades of this type, that is, conventional rotor blades of turbines and axial flow compressors, mainly those with long blades, have a through hole 2 in the middle part of the rotor blade 1 in the span direction, as shown in FIG. Furthermore, as shown in FIG. 2, a connecting rod 3 is inserted through the through hole 2, thereby connecting a plurality of adjacent rotor blades 1.

The group blade structure formed in this manner has the advantage that the rigidity near the connecting portion is greater than that of a single blade, and the vibration intensity can be increased due to the effect of connecting the rotor blades to each other. However, in such a conventional example, there is a problem that the blades may be damaged due to self-excited vibration called blade cascade flutter.

That is, in the above configuration, the blade thickness (that is, the thickness of the rotor blade) near the connecting portion, especially from the connecting portion to the tip of the rotor blade, is significantly thinner than near the root of the rotor blade, and the connection effect by the connecting rod 3 is also reduced. Regardless, the blade rigidity near the tip of the rotor blade remains low. Low blade rigidity means low strain energy, and therefore the structure is such that the vicinity of the tip of the rotor blade vibrates more easily than the vicinity of the root of the rotor blade. As described above, although the blade rigidity is low near the tip of the rotor blade, the circumferential velocity here is higher than that near the root of the rotor blade, and therefore the inflow velocity of the working fluid into the rotor blade is increased. When the inflow velocity of the working fluid is high, the energy of the flow increases, and the fact that such a flow acts near the tips of the rotor blades where the blade rigidity is low means that the areas near the tips of the rotor blades are not active. This means that it is greatly influenced by the fluid. This is important when considering the problem of rotor blade vibration. In other words, under these conditions, even if the flow is uniform and no periodic external force acts, a self-excited phenomenon called blade cascade flutter occurs in a blade cascade consisting of rotor blades arranged circumferentially. Vibrations may occur and cause damage to the blades.

In order to increase safety against this blade cascade flutter, it is effective to make various factors that affect the vibration characteristics of the individual blades that make up the blade cascade non-uniform, such as blade stiffness and blade mass. This is generally known from the characteristics of blade row flutter. However, in the prior art, due to its structure, such a non-uniform structure for preventing blade row flutter could not be adopted. In other words, in the conventional blade group structure as shown in Fig. 2, a plurality of rotor blades 1 having the same structure are connected with a uniform connection structure, so mutual movement between adjacent rotor blades is independent of any blade. Maintaining a constant relationship, the energy of the flow flows into the rotor blades due to the mutual movement of the rotor blades, and the energy does not create a state where self-excited vibration is likely to occur, that is, a structure with low safety against blade cascade flutter. You don't get it. As described above, the conventional technology has the risk of blade damage due to blade cascade flutter.

In view of the above circumstances, an object of the present invention is to provide a safe and advantageous blade group structure that is highly safe against self-excited vibrations called blade cascade flutter, and does not cause damage to the blades due to this.

In order to achieve this objective, in the present invention,
A connecting member is provided through the longitudinally intermediate portion of the rotor blades to thereby connect adjacent blades across a plurality of blades to form a group blade structure, and at least one connecting member of the rotor blades is provided through the connecting member. The position has a through hole for passing through the connecting member, extends in a direction perpendicular to the longitudinal direction of the rotor blade or in a direction slightly inclined to the perpendicular direction, and protrudes from the side surface (both sides or one side) of the rotor blade. At least one rotor blade without such a protrusion is provided, and thereby two or more rotor blades are provided with non-uniformity in the bonding condition between the rotor blade and the connecting member and in the rotor blade structure. are arranged to form a wing structure.

In addition, in embodying the present invention, taking safety against forced vibration into consideration, a configuration is adopted in which rotor blades having protrusions are arranged at symmetrical positions with respect to the center of the group of blades, so as to avoid problems with forced vibration. Therefore, it is possible to reduce the number of resonance points and improve the safety against the resonance points.

Furthermore, by adopting a mode in which the protrusions are formed from the leading edge to the trailing edge of the blade, it is possible to increase the non-uniformity inside the group of blades and further improve the safety against blade cascade flutter.

It is also possible to provide the protrusions in a streamlined manner to significantly reduce fluid resistance due to the protrusions.

In addition, by enlarging the through hole in the protrusion toward the tip of the protrusion, it is possible to significantly reduce the bending moment generated at the base of the protrusion due to the centrifugal force of the connecting rod.

Hereinafter, an example of implementation of the present invention will be described with reference to the drawings.

The present invention relates to a structure of a rotor blade operated by a fluid in an axial flow machine, and is a group structure in which two or more rotor blades are arranged. In the example shown in FIG. is shown.

In the present invention, as illustrated in the same figure, a connecting member is provided through the rotor blades 1 and 4 at their longitudinal intermediate portions, thereby connecting adjacent blades to each other across a plurality of blades 1 and 4. It is connected.

In the illustrated example, a round bar-shaped connecting rod is used as the connecting member 3, and through holes 7,
It passes through 6. There are two types of attachment structures for the connecting member 3 to the wings 1 and 4: fixed and loose.
In this row, the connecting member 3 has a larger through hole 7,
A loose method is adopted in which the device is arranged so that it can slide inside the 6. For this reason, the through-holes 7 and 6 are made large enough to leave a slight gap in order to prevent the two from coming into close contact with each other when the connecting member 3 is inserted through the through-hole. In such a loose structure, the rotor blades 1 and 4 are connected and integrated by the connecting member 3 due to the action of centrifugal force generated as the rotor blades 1 and 4 rotate. These connecting materials 3
and the through holes 7 and 6 provided in the rotor blades 1 and 4,
The shape takes into consideration the circumferential curvature at the position on the rotor blade where the through hole is provided (note that the present invention can be effectively applied without any problem even if a fixed structure is used instead of a loose structure). .

Furthermore, in the present invention, at least one of the rotor blades 1 and 4, that is, the rotor blade 4 in the example shown in FIG. 3, is provided with a protrusion 5 projecting from both side surfaces 10 of the rotor blade 4. This protrusion 5 is configured to have the above-mentioned through hole 6. The protrusion 5 is formed to extend in a direction perpendicular to the longitudinal direction of the rotor blade 4 (or in a direction slightly inclined with respect to the perpendicular direction). The protrusion 3 in the illustrated example is formed substantially perpendicular to the longitudinal direction of the rotor blade 4 .

The blade group structure of the present invention includes at least one rotor blade 1 without such a protrusion 5 in addition to the rotor blade 4 having such a protrusion 5 . With this configuration, the coupling conditions between the rotor blades 1 and 4 and the connecting member 3 are made non-uniform, and the rotor blades 1 and 4 are
Two or more rotor blades are arranged while providing non-uniformity in the structure of the rotor, and the non-uniformity of the lever is utilized to improve safety against the above-mentioned blade cascade flutter (self-excited vibration).

Next, we will explain the structure of an example of a group structure of five rotor blades obtained by applying the rotor blade connection structure shown in FIG. This shall also extend to the explanation of. An example of this is shown in FIG. FIG. 4 is a view of the vicinity of the rotor blade connecting member viewed from the inflow direction of the working fluid (for example, water vapor or gas). A blade wheel is constructed by combining a large number of such blades to form a circumference, and the blade wheel is rotated by the action of working fluid on the rotor blades.

In the embodiment shown in FIG. 4, the center rotor blade 4 of the five rotor blades has a rotor blade that protrudes from both side surfaces 10 of the rotor blade at the intermediate portion in the longitudinal direction of the rotor blade, and extends in the longitudinal direction of the rotor blade 4. A protrusion 5 is provided that extends in a direction perpendicular thereto. However, other rotor blades 1 are not provided with such projections. The five rotor blades 1 and 4 are connected by a connecting member 3 penetrated through through holes 7 and 6 provided in each, and the configuration has non-uniformity in connection conditions and rotor blade structure, It has a group wing structure.

The connecting member 3 has the loose structure described above,
When the blade wheel rotates, the connecting member 3 is strongly pressed against the upper part of the through holes 7 and 6 provided in each of the rotor blades 1 and 4 due to centrifugal force, increasing the connectivity of the five rotor blades and making them no longer act as a single blade. Rather, it exhibits vibration characteristics as a group of five blades integrated into one.

In the conventional example, that is, the group blade structure consisting only of the same rotor blades 1 as shown in Fig. 2, the rotor blade structure is uniform and the coupling conditions are the same, so the vibration characteristics of the group blades are constant between adjacent blades. It is. In this case, self-excited vibration called blade row flutter is likely to occur, and there is a risk of damage due to this. However, in the configuration shown in FIG.
Since the rotor blades 4 are provided, the rotor blade structure and connection conditions are non-uniform, and therefore the blade group structure is given non-uniformity locally. As a result, the mutual vibration mode between adjacent blades differs depending on the blade. This difference in vibration mode between blades due to the non-uniformity of the structure prevents the generation of self-excited vibration and can improve safety against blade cascade flutter. That is, differences in vibration patterns, such as differences in blade amplitude and mode, act in a direction that prevents the flow of energy from the working fluid into the group of blades, and therefore can improve safety against blade cascade flutter.

The protrusions 5 not only change the conditions of connection by the connecting rod 3 as described above, but also increase the rigidity of the rotor blades 4 themselves at the connection part and also increase their mass, so that the difference with other rotor blades 1 is As a result, the non-uniformity within the group of blades is further enhanced, thereby further increasing safety against blade cascade flutter.

Next, an embodiment will be shown in which rotor blades provided with protrusions are arranged symmetrically with respect to the center rotor blade in order to increase safety not only against self-excited vibrations but also against forced vibrations.

That is, a plurality of group blades are arranged on the circumference to form an annular blade row, but if the rotor blades with protrusions are used as in the present invention to make the structure for each group non-uniform, When the rotational speed range (that is, the operating range) of the impeller is wide, the individual blades have different non-uniformities, which results in an increase in the number of resonance points that can cause problems with forced vibration.

However, even in such a case, safety against forced vibrations can be improved by adopting a structure such as this embodiment shown in FIG.

The example in Fig. 5 is a group blade structure in which one group blade consists of five blades, three of which are rotor blades 4 having protrusions 5, and two such group blades are adjacent to each other. It shows the state of being. As shown in the figure, the rotor blade 4 having the protrusion 5 is arranged in a symmetrical position with respect to the central rotor blade (in this case, the rotor blade 4 indicated by reference numeral 4a), and the rotor blade 4 having the protrusion 5 4 are arranged at symmetrical positions from the center of each blade group, and the positions of the rotor blades 4 are made equal among the blade groups. By arranging the moving blades 4 in symmetrical positions with respect to the center for each group of blades in this way, the vibration characteristics between the group blades become equal, the number of resonance points is reduced, and therefore safety against forced vibration can be increased. be.

Even in this case, since non-uniformity is maintained within each blade group, safety against blade cascade flutter is maintained. Therefore, this aspect can be said to exhibit the effect of the present invention, which is safety against blade row flutter, and can also improve safety against forced vibration. In addition, by arranging the rotor blades 4 having protrusions 5 at symmetrical positions from the center of the group blades, each blade group maintains the vibration mode of the group blades symmetrically, thereby preventing large deviations in the vibration modes due to the individual blades. You can Therefore, this prevents excessive stress from acting only on a specific blade, and allows stress relaxation.

The above description has been about a blade group structure consisting of five rotor blades 1 and 4, but the blade group structure of this aspect is not limited to this, and can be applied to a group blade structure consisting of any number of blades. It is.

Next, we will discuss the structure of the rotor blade joint that can effectively improve safety against blade cascade flutter by increasing the degree of non-uniformity inside the group of blades. A structure that takes strength into consideration will be explained below.

Fig. 6 shows an example of a mode in which protrusions are formed from the leading edge to the trailing edge of the rotor blade (this figure is a view of the group blade viewed from the top, that is, from the direction of the arrow in Fig. 3). ). In this example, the protrusion 5 protruding from the rotor blade 4 in the circumferential direction is formed from the leading edge 8 to the trailing edge 9 of the rotor blade 4 at the rotor blade connecting portion, and extends along the rotor blade 4. have. Such protrusions 5 significantly increase the rigidity of the rotor blades 4 in the vicinity of where they are connected by the connecting rods 3. As a result, inside the group of blades, there is a large difference in blade rigidity and blade mass in the vicinity of the connecting portion between the rotor blade 1 without the protrusion 5 and the rotor blade 4 with the protrusion 5. Therefore, the non-uniformity inside the blade group is increased, and the safety against blade cascade flutter is further improved.

Next, in view of the influence of flow on the protrusion, a configuration that can reduce fluid resistance will be described. FIG. 7 is an example of such a structure, and is a side view of the vicinity of the protrusion seen from the side surface of the rotor blade. Originally, in the present invention, the protrusion 5 extends perpendicularly to the longitudinal direction of the rotor blade, or in a direction close to it, so that the fluid resistance is reduced. It has a streamlined structure from the leading edge 8 to the trailing edge 9. As a result,
The fluid resistance due to the projections 5 is further reduced significantly. Therefore, even in a configuration in which the blade group structure is made non-uniform by the protrusions 5 as in the present invention, if this aspect is adopted, the influence caused by the resistance of the protrusions 5 to the flow can be minimized.

In addition, in each example in which non-uniformity inside the blade group was achieved, if the airfoil shape itself and the pitch between the blades were kept constant for all moving blades,
The axisymmetric flow of the axial flow machine is not impaired, and therefore the steady state function of the axial flow machine is not impaired either.

Next, I will add some explanations regarding important matters. FIG. 8 is a longitudinal sectional view of the vicinity of the rotor blade connection section showing the connected state, that is, it corresponds to the - line sectional view of FIG. 3, and the broken line shows the state when the blade wheel is stationary. The solid line indicates the state when the impeller rotates. As shown in this figure, connecting rod 3
is pressed against the upper surface of the through hole 6 by centrifugal force when the blade wheel rotates, and as a result, the maximum bending moment is generated at the root of the protrusion 5 to the rotor blade 4. However, when embodying the present invention, it is possible to appropriately set the length (width) l of the protrusion 5 in the rotational direction so that the length l does not pose a problem in terms of strength. It is possible.

Further, as shown in FIG. 9, the vicinity of the tip of the through hole 6 in the protrusion 5 is enlarged in the vicinity of both openings, taking into account the shape of the connecting rod 3 deformed by centrifugal force (see FIG. 8). It is also possible to have a shape with 6'. With such a configuration, the bending moment generated at the root portion (root portion) of the protrusion 5 due to the centrifugal force of the connecting rod 3 can be significantly alleviated.

As mentioned above, as an example, a group blade structure having protrusions protruding from both sides of the rotor blade and extending substantially perpendicular to the longitudinal direction of the blade has been described. Many variations are possible. For example, since the protrusions make the blade structure non-uniform within the group of blades, the protrusions can be provided only on one side of the rotor blade. As other modifications, it is of course possible to arbitrarily change the length of the protrusion from the leading edge to the trailing edge of the rotor blade, or to create a structure in which two or more through holes are provided and a group of blades is constructed from a plurality of connecting rods. It is possible.

As detailed above, in the blade group structure of the present invention, at least one of the rotor blades has a through hole for penetrating the connecting member at a position where the rotor blade passes through the connecting member, and in a direction perpendicular to the longitudinal direction of the rotor blade ( A protrusion protruding from the side surface of the rotor blade extending in a direction slightly inclined to the vertical direction is provided, and at least one rotor blade without such a protrusion is provided, thereby creating a connection between the rotor blade and the connecting member. Since the coupling conditions and rotor blade structure are made non-uniform, it has the effect of exhibiting high safety against blade cascade flutter, and has the advantage that safety is significantly improved compared to the conventional method.

Although the illustrated embodiment has many other advantages, the present invention is not limited to this embodiment.

[Brief explanation of the drawing]

FIG. 1 shows a typical rotor blade, and is a front view of the rotor blade before the blade wheel is assembled. FIG. 2 is a schematic diagram for explaining a conventional blade group structure. FIG. 3 is a schematic perspective view showing one structural example of the present invention, FIG. 4 is a front view of an embodiment to which the structural example is applied, FIG. 5 is a front view of another embodiment, and FIG. 6 is a front view of another embodiment. An example of a group of blades is viewed from above, and is a plan view corresponding to the direction arrow view in Figure 3. Figure 7 is a side view of the vicinity of the protrusion seen from the side of the rotor blade. Figure 8 is also a connected state. FIG. 9 is a longitudinal sectional view of the rotor blade connecting portion and its vicinity, corresponding to the cross section taken along the line in FIG. 3, and FIG. 9 is a longitudinal sectional view of the rotor blade before the connecting rod is inserted. 1... Moving blade (without protrusion), 3... Connecting rod, 4
... Moving blade (having a protrusion), 5... Protrusion, 6... Through hole (in a moving blade having a protrusion), 7... Through hole (in a moving blade not having a protrusion), 8... (Blade) leading edge,
9... (wing) trailing edge, 10... side surface of rotor blade.

Claims (1)

[Claims] 1. A group of blades in which a connecting member is provided through the longitudinally intermediate portion of the rotor blades of a fluid-operated axial flow rotary machine, thereby connecting adjacent blades to each other across a plurality of blades. In the blade structure, at least one of the rotor blades has a through hole for penetrating the connecting member at a position where the connecting member is inserted, and a hole is provided in a direction perpendicular to the longitudinal direction of the rotor blade or in the perpendicular direction. A protrusion extending in a slightly inclined direction and in the blade span direction and protruding from the blade surface of the rotor blade is provided, and at least one rotor blade without such a protrusion is provided, thereby improving the connection between the rotor blade and the connecting member. 2 while maintaining heterogeneity in conditions and rotor blade structure.
A blade group structure characterized by being configured by arranging three or more rotor blades. 2. The blade group structure according to claim 1, wherein the rotor blades having the protrusions are arranged at symmetrical positions with respect to the center of the blade group. 3. The blade group structure according to claim 1 or 2, wherein the protruding portion is formed from the leading edge to the trailing edge of the blade. 4. The wing structure according to any one of claims 1 to 3, wherein the protrusion has a streamlined shape. 5. The group according to any one of claims 1 to 4, characterized in that the diameter of the through hole in the protrusion through which the connecting member is inserted is enlarged toward the tip of the protrusion. wing structure.