JP3397599B2 - Axial turbine blade group - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of an axial flow turbine blade group, and in particular, a plurality of turbine blades arranged in an annular blade cascade flow path are curved so as to project a blade pressure surface in the circumferential direction. The present invention relates to a turbine blade group of formed three-dimensional design blades.

[0002]

2. Description of the Related Art As a conventional example of a blade structure based on a three-dimensional design of an axial flow turbine, taking a stationary blade as an example, in addition to a structure in which the same blade cross-sectional shape is simply stacked linearly in a radial direction, For example, An Investivation of Leaned Nozzle Effe
cts on Low Pressure Steam Turbine Efficiencies, Pr
oc. of the Advances in Steam Turbine Technology fo
rPower Generation PWR-Vol.10 ASME Power division
There is a structure in which the stationary blade is simply tilted in the rotating direction of the moving blade as described in. This is intended to suppress delamination of the root portion in a stationary blade having a long blade length such as a steam turbine low pressure stage.

In addition, The Influence of Blade Lean on T
There is also a structure with an arched shape that is symmetrical in the height direction of the blade as seen from the axial direction of the trailing edge line of the stationary blade, as described in urbine Losses, ASME Paper No.90-GT-55. This is intended to suppress the development of secondary flow vortices generated near the inter-blade side wall of the stationary blade.

On the other hand, for example, JP-A-3-18930
As described in No. 4, there is a structure in which the trailing edge line of the stationary blade is viewed in the axial direction and has an asymmetrical arcuate shape in the height direction of the blade.
Furthermore, as seen from the axial direction and the meridian plane, the trailing edge line of the stationary blade as described in JP-A-6-81603,
There is an arched structure that is asymmetric in the height direction of the wing.

Among the above-mentioned conventional techniques, a blade excluding a blade shape in which the same blade cross-sectional shape is simply piled linearly in the radial direction is called a three-dimensional design blade, and is called a three-dimensional design blade. It is a means to effectively suppress the boundary layer and secondary flow vortices that develop near the sidewall of the blade. However, among these three-dimensional design blades, three-dimensional design blades called bow blades, which are curved so as to project the blade pressure surface in the circumferential direction, are selected depending on the amount of protrusion to the recoil degree of the turbine stage or the blade located downstream. Since the incident angle of the blade changes, it is necessary to find and control the similarity parameter of the three-dimensional design blade called the bow blade based on the protrusion amount.

[0006]

In the inter-blade flow passage of an axial turbine, a pair of secondary flow vortices are generated by centrifugal force due to three-dimensional flow separation at the blade leading edge and bending of the flow passage.
A boundary layer also develops on the side wall. Secondary flow vortices and boundary layers cause fluid loss in inter-blade flow.

The above-mentioned three-dimensional design blade is devised for the purpose of suppressing these. However, although this three-dimensional design blade is effective in reducing the loss in the vicinity of the side wall, it does not extend in the circumferential direction. In a three-dimensional design blade called a bow blade, which is curved so as to project the blade pressure surface, it is difficult to obtain the designed flow pattern because the blade load changes in the span direction. That is, the recoil degree of the turbine and the angle of incidence on the blade located downstream are variously changed depending on the amount of protrusion, and there is a tendency that the turbine efficiency cannot be improved depending on the model.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to reduce the side wall loss even if the blade length and the number of blades are changed in each paragraph of an axial flow turbine composed of multiple paragraphs. The present invention is to provide an axial flow turbine blade group capable of improving the efficiency of the turbine by controlling the incident angle of the fluid on the blade located downstream and providing an optimum fluid flow pattern.

[0009]

That is, the present invention is provided with a plurality of turbine blades arranged in parallel in the circumferential direction and the axial direction in an annular blade row passage through which a working fluid flows, and each of the turbine blades is provided. In the axial flow type turbine blade group in which the blades are curved so as to project in the circumferential direction of the blade pressure surface, when the circumferential pitch of the turbine blades is t and the circumferential projection amount is δc, the number of blades and the number of blades It is formed so as to maintain the relationship of δc / t = C (constant) regardless of the length of the object to achieve the intended purpose.

In this case, the C (constant) is set to 0.0
It is formed so as to maintain the relationship in the range from 1 to 0.5.

That is, in the case of the axial-flow turbine blade thus formed, the circumferential pitch (t) and the circumferential protrusion amount (δc) of the turbine blade are irrespective of the number and size of the blades.
The relationship of δc / t, that is, the relationship of δc / t, is formed so as to maintain a certain constant, so that the outflow angle distribution in the blade length direction is almost the same. The incident angle to the row is controlled under the same condition, the loss reduction effect of the three-dimensional design blade can be fully utilized, and as a result, the turbine stage efficiency can be improved.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the illustrated embodiments. First, the similarity parameters of a three-dimensional design blade in which the blade is curved so as to project the blade pressure surface in the circumferential direction. In order to provide the above, the conditions under which the blade outflow angles are the same will be described. The outflow angle is a typical amount that exhibits the effect of a three-dimensional design blade in which the blade is curved so as to project the blade pressure surface in the circumferential direction. That is, in the above three-dimensional design wing,
Since the blade load is changed in the span direction, the outflow angle changes accordingly.

Therefore, the degree of effect of the three-dimensional design blade can be known by examining the change rate of the outflow angle.
FIG. 1 is a view of a blade of an axial flow turbine as viewed from the downstream side, and a plurality of blades are provided between an upper diaphragm 1 and a lower diaphragm 2. The trailing edge 3 of the three-dimensional design blade curved so as to project the blade pressure surface has a curved shape as shown in FIG. The broken line 4 is a straight line extending radially from the blade root portion in a radial direction, and the blade length is defined by H, the maximum protrusion amount is δc, and the blade root pitch is defined by t.

In order to simulate the flow of such a three-dimensional design blade that is curved so as to protrude from the blade pressure surface, a three-dimensional turbulent flow test is performed in a blade row test state in which a plurality of three-dimensional design blades are arranged between parallel walls. The flow was simulated by analysis. The sidewall boundary layer thickness at the inlet was calculated as 10% of the blade length. Performing various parameter surveys targeting such flow fields,
As a result of obtaining the similarity parameter regarding the outflow angle, it was found that the condition that the ratio of the maximum protrusion amount δc and the blade pitch is constant is a condition for obtaining the similar outflow angle distribution. The calculation results are shown below.

FIG. 2 shows a blade length H of 120 mm and a blade pitch t.
Is a discharge angle distribution in the span direction when the protrusion amount δc is changed while keeping the value of 36.1 mm constant. The horizontal axis represents the spanwise position in terms of blade length. The same applies to the following figures. As is apparent from FIG. 2, when the protrusion amount δc is increased, the change in the outflow angle also increases with the change in the blade load in the span direction. The larger outflow angle near the side wall means that the root recoil of the turbine stage increases. The main purpose of the present invention is to find a parameter for controlling such a change in outflow angle and control the protrusion amount δc.

FIG. 3 shows the outflow angle distribution in the span direction when the blade pitch is constant and the ratio of the blade length H to the protrusion amount δc is constant. It can be seen that the outflow angles are different even if the ratio between the blade length H and the protrusion amount δc is constant, and δc / H cannot be adopted as a similarity parameter.

The results of finding the similarity of the outflow angle distribution, which is an important parameter related to turbine stage performance, by performing various parameter surveys as described above are shown below.

FIG. 4 shows the outflow angle distribution in the span direction when the blade length is changed while keeping the ratio of the protrusion amount δc and the blade pitch t constant. As is clear from FIG. 4, even if the blade length changes, if the ratio between the protrusion amount δc and the blade pitch t is kept constant,
It can be seen that the outflow angle distribution in the blade length direction is almost the same.

The following calculation example is an example in which the blade length is kept constant and the blade pitch is also enlarged by enlarging the blade so that the ratio between the blade pitch t and the protrusion amount δc is kept constant. Therefore, the protrusion amount δc increases as the blade pitch t increases. The result is shown in FIG. As is clear from this figure, even if the blade pitch is expanded by expanding the blades in a similar manner,
If the ratio between the protrusion amount δc and the blade pitch t is kept constant, the outflow angle distribution becomes the same.

In the final confirmation of similarity, the protrusion amount δc is set to 3 m.
It is a calculation when the blade pitch is changed to 36.1 mm and the blade length is changed to m. Therefore, the protrusion amount δc is half that in FIG. 4 described above. The result is shown in FIG. Even if the protrusion amount δc is reduced, if the ratio with the blade pitch is constant, the outflow angle becomes almost the same as shown in FIG. 6 even if the blade length is changed.

From the results of the parameter survey by the above three-dimensional turbulence analysis, as the similar parameters of the three-dimensional design blade in which the blade is curved so as to project the blade pressure surface in the circumferential direction, the protrusion amount δc and the blade pitch t are set. It was newly revealed that the ratio δc / t is appropriate. This is the basis of the present invention.

The first embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a diagram in which the present invention is applied to a stator blade of an axial turbine, and is a view of the stator blade of the present invention as viewed from the downstream side. The blade length is H, the protrusion amount is δc, and the blade root pitch is selected as a representative of the blade pitch, which is designated as t. Generally, a turbine is composed of multiple paragraphs, and in each paragraph the blade length, number of blades,
That is, although the blade pitch is different, the blade length and the number of blades are different as a blade row configuration condition when applying a three-dimensional design blade in which the blade is curved so as to project the blade pressure surface in the circumferential direction in such a turbine stage. Even if the protrusion amount δc and the blade root pitch t
The ratio of δc / t is constant, that is, δc / t = C (constant)
It is the first embodiment of the present invention to have the relationship of

By implementing such a blade row configuration, it becomes possible to control the recoil degree of the turbine stage and the incident angle to the blade row located on the downstream side under the same conditions, and reduce the loss of the three-dimensional design blade. The effect can be fully utilized. As a result, turbine stage efficiency is also improved.

Next, a second embodiment of the present invention will be described with reference to FIG. In this figure, the horizontal axis represents δc / t, and the vertical axis represents the paragraph efficiency improvement Δη (%) from the turbine efficiency when the three-dimensional design blade is not used. In addition,
This FIG. 7 is based on a calculation method for simultaneously turbulently analyzing the flow between the three-dimensional blades of the stationary blade and the moving blade. As shown in this figure, as δc / t is increased, the paragraph efficiency increases, but when δc / t exceeds 0.5, the paragraph efficiency tends to decrease.

The lowering of the paragraph efficiency is because the incident angle loss of the moving blade located on the downstream side is larger than the loss reducing effect of the three-dimensional design blade. Therefore, in order to improve the turbine efficiency, the constant C of δc / t = C (constant) is set to 0.0 <even if the blade length and the number of blades are changed in each paragraph of the axial flow turbine composed of multiple paragraphs. Since it is necessary to select from the range of C ≦ 0.5, in the second embodiment of the present invention, 0.0 <δc / t ≦ 0.5 is set to improve turbine efficiency.

Finally, a third embodiment of the present invention will be described with reference to FIG. As is clear from this figure, when the value of δc / t is set to 0.1 ≦ δc / t ≦ 0.4, the three-dimensional shape of the blade is curved most effectively so as to project the blade pressure surface in the circumferential direction. Design blades can be used and values in that range can be used to improve turbine efficiency.

In the above description, the blades are arranged radially, and the blades of the root and the tip have trailing edges on the same radial direction, but the blades having such a shape are always used. It does not have to be provided, and it is needless to say that the same action and effect can be achieved even if the blade tip side is a blade inclined in the circumferential direction as shown in FIG. In this case, the protrusion amount δc becomes the distance from the radiation.

Even if the blade has a shape in which the trailing edge of the root and the trailing edge of the tip are on the same radial direction of radiation, for example, as shown in FIG. 9 or FIG. Alternatively, it is needless to say that the same effect can be obtained even in the case of a blade whose shape is shifted toward the blade tip side.

As described above, with the blade group formed in this manner, the blade in the case of applying the three-dimensional design blade in which the blade is curved so as to project the blade pressure surface in the circumferential direction in the turbine stage As a row configuration condition, the ratio δc / t between the protrusion amount δc and the blade root pitch t is constant, that is, δc / t = C, even if the blade length and the number of blades are different in each paragraph of an axial flow turbine that is composed of multiple paragraphs. By maintaining the relationship of (constant), it is possible to control the effects of the above three-dimensional design blades in the same way,
Moreover, turbine efficiency can be improved by selecting the value of the constant C from the range of 0.0 <C ≦ 0.5. In order to use the three-dimensional design blade more effectively, if the value of the constant C is selected from the range of 0.1 ≦ C ≦ 0.4, the turbine efficiency can be further improved.

In the case of the present invention, except for the low pressure last stage of the steam turbine and the two stages before it, the purpose is to reduce the side wall loss. Therefore, if the curve is made based on the found similarity parameter. Even if the number of blades or the blade length changes, the same side wall loss reduction effect can be obtained. Further, in the low-pressure final stage and the preceding two stages of the steam turbine, since the emphasis is placed on the control of the root reaction degree rather than the purpose of reducing the side wall loss, the bending method is different. Even in that case, of course, it is also possible to bend the root recoil degree based on the similarity parameter of the present invention in order to set it to a predetermined value.

[0031]

As described above, according to the present invention, even if the blade length and the number of blades change in each paragraph of the axial flow turbine composed of multiple paragraphs, the side wall loss can be reduced and the downstream can be reduced. It is possible to obtain a blade group of an axial-flow turbine of this type capable of controlling an incident angle of a fluid on a blade located, an optimum fluid flow pattern, and improving turbine efficiency.

[Brief description of drawings]

FIG. 1 is a front view showing a main part of an embodiment of an axial flow turbine blade group of the present invention, as viewed from the downstream side of the blade group.

FIG. 2 is a diagram showing changes in the outflow angle in the span direction with respect to the protrusion amount δc of the three-dimensional design blade.

FIG. 3 is a diagram showing changes in the outflow angle in the span direction when δc / H is kept constant and the blade length is changed.

FIG. 4 is a diagram showing changes in the outflow angle in the span direction when δc / t is kept constant and the blade length is changed.

FIG. 5 is a diagram showing changes in the outflow angle in the span direction when δc / t is kept constant and the blade size and blade pitch are changed.

FIG. 6 is a diagram showing changes in the outflow angle in the span direction when δc / t is kept constant and the blade length is changed.

FIG. 7 is a diagram showing the relationship between the magnitude of δc / t and the paragraph efficiency improvement amount.

FIG. 8 is a diagram showing δc when the blade trailing edges of the root and the tip are not on the radial line in the same radial direction.

FIG. 9 is a diagram showing δc when the maximum protrusion amount is near the blade tip.

FIG. 10 δc when the maximum protrusion amount is near the blade root
FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Upper diaphragm, 2 ... Lower diaphragm, 3 ... Blade trailing edge, 4 ... Radial straight line extending from a blade root part in a radial direction.

─────────────────────────────────────────────────── --- Continuation of front page (56) References JP-A-6-81603 (JP, A) JP-A-3-189303 (JP, A) JP-A-5-312003 (JP, A) JP-A-6- 193402 (JP, A) JP 5-26004 (JP, A) JP 7-253001 (JP, A) JP 2-49902 (JP, A) JP 3-189304 (JP, A) JP-A-8-74502 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F01D 1 / 00-11 / 10

Claims (5)

(57) [Claims] 1. A plurality of turbine blades arranged side by side in a circumferential direction and an axial direction are provided in an annular blade row flow path, and each turbine blade is curvedly formed so as to project a blade pressure surface in a circumferential direction. In the axial flow type turbine blade group, when the circumferential blade root pitch of the turbine blade is t and the circumferential protrusion amount is δc, δc / t = C regardless of the number of blades and the length of the blade. An axial flow turbine blade group characterized by being formed so as to maintain a (constant) relationship. 2. A plurality of turbine blades arranged in parallel in the circumferential direction and the axial direction are provided in the annular blade cascade flow path, and each of the turbine blades is curved so as to project a blade pressure surface in the circumferential direction. In the axial flow type turbine blade group, the circumferential blade root pitch of the turbine blade is t, the straight line radially extended from the blade root trailing edge and the circumferential displacement when the blade pressure surface is projected. When the maximum difference of is δc,
Δc / t = regardless of the number of blades and the length of the blades
An axial-flow turbine blade group formed so as to maintain a C (constant) relationship. 3. A plurality of turbine blades arranged side by side in the circumferential direction and the axial direction are provided in the annular blade cascade flow path, and each turbine blade is curved so as to project a blade pressure surface in the circumferential direction. In the axial flow type turbine blade group of the three-dimensional designed blades, when the circumferential blade root pitch of the turbine blade is t, a straight line radially extended from the blade root trailing edge and a blade pressure surface are projected. The maximum difference from the circumferential displacement is set to δc, and it is formed so that the relation of δc / t = C (constant) is maintained even if the blade length and the number of blades change in each paragraph of the axial turbine composed of multiple paragraphs. Axial-flow turbine blade group characterized by. 4. The δc / t is formed so as to maintain a relationship in the range of 0.0 to 0.5.
The axial flow turbine blade group according to claim 1, 2, or 3 . 5. The δc / t is formed so as to maintain the relationship in the range of 0.1 to 0.4.
The axial flow turbine blade group according to claim 1, 2, or 3 .