JP2710729B2 - Axial turbine blades - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an axial flow turbine blade.

[0002]

2. Description of the Related Art The blades of an axial flow turbine are of a wide variety.
This is because the blades of the axial flow turbine are determined based on the design concept of the turbine manufacturer so that the blades of the axial flow turbine are harmonized with the design of the thermal fluid and the entire structure. It is extremely flexible.

[0003] Among the known examples of the prior art, a recent specific example is described in VGB Kraftwerkstech (1988), which includes design guidelines for the blade of an axial flow turbine, including thermo-hydrodynamics and strength.・ It is stated that it is determined from each condition of vibration dynamics.

Next, a moving blade of a conventional axial turbine is shown in FIGS.
This will be described with reference to FIG.

FIG. 6 is an explanatory view of a blade shape of a conventional axial flow turbine, FIG. 7 is an explanatory view of a blade shape at each position in a blade length direction of a conventional example, and FIG. 9 and FIG. 9 are explanatory diagrams of the blade inlet angle and the blade outlet angle of the conventional example, FIG. 10 is a diagram of each blade row at the root portion and the tip portion of the conventional example, and FIG. 11 is a description of the airfoil loss coefficient of the conventional example. In the figure, 1 is an airfoil, 2 is a leading edge, 3
Is a trailing edge, 5 is a dorsal side, 6 is a flow passage inlet, 7 is a flow passage outlet, 8 is a trailing edge of a ventral blade, 9 is a streamline, 11 is a separation area, 12 is an airfoil, and B is a wing. Axial dimension of the leading and trailing edges of the
S is the throat size, t is the blade pitch, W is the blade width, βm is the blade inlet angle, H is the blade length, L is the length of the coupling structure, γm is the blade outlet angle, C is the chord length, and θ is the blade turning angle. Is shown.

FIG. 6 shows only two adjacent blades taken out of rotor blades installed on the entire circumference around the turbine axis. The moving blade is formed by integrally forming an airfoil portion 12 as a fluid flow path and a coupling structure portion 13 with a turbine shaft, and an interval between adjacent moving blades is a blade pitch t.
Is represented by

FIG. 7 shows an airfoil 1 at each position in the blade length direction of the rotor blade. 7 (a) shows the tip, FIG. 7 (b) shows the center, and FIG. 7 (c) shows each airfoil 1 at the root including the coupling structure 13 with the turbine shaft. , Respectively.

Since the moving blades are installed in a fan shape from the center of the turbine shaft, the blade pitch t increases from the root to the tip of the moving blade.

FIG. 8 shows basic specifications required for the cascade configuration. That is, the airfoil 1 has a blade width W, a chord length C, and a blade entrance angle β.
m and the blade exit angle γm. The flow path between the adjacent airfoils 1, that is, the flow path between the cascades in which the airfoils 1 are arranged in parallel, has a flow path inlet 6 and a flow path outlet 7. The narrow portion is determined by the throat size S from the geometric relationship between the ventral wing trailing edge 8 and the backside 5 of the adjacent airfoil 1 facing it.

As described above, the configuration of the airfoil and the cascade are determined from the thermal fluid design and the strength design. From the viewpoint of the thermal fluid design, the blade inlet angle βm and the blade outlet The angle γm is determined. These angles differ depending on the blade height, that is, the radial position of the moving blade, as shown in FIG. 9. In general, the angles in the flow direction of the fluid determined from the thermal fluid design are different from those in the flow direction. It is a match.

On the other hand, in the strength design, the blade cross-sectional area that can withstand the acting force from the fluid and the centrifugal force is determined. In this case, the generated stress is larger at the root of the airfoil and becomes smaller at the tip, so that the blade cross-sectional area is the largest at the root, and is gradually reduced toward the tip. The wing width W and the chord length C are determined by this design policy.

Further, the cascade pitch t is adjusted so that the coupling structure of the rotor blade connected to the turbine shaft has a sufficient shape in terms of strength.
Has been determined. Further, the ratio between the throat size S and the pitch t is set so that the flow rate passing between the cascades satisfies a predetermined value.

FIG. 10 shows a configuration example of the airfoil and cascade determined by the above design guidelines. 10A shows the case of the root portion, and FIG. 10B shows the case of the tip portion. Comparing the two, βm, t, and S are larger and the turning angle θ is smaller at the tip portion than at the root portion. The blade is configured such that the airfoil 1 changes continuously from the root to the tip.

The blade entrance angle βm as shown in FIG.
Is smaller, the blade pitch t constituting the cascade
It has been described by Ainley et al. That the airfoil loss coefficient has a characteristic as shown in FIG. 11 depending on the ratio of the airfoil shape and the chord length C (= t / C). (Minimum value), it is shown that it changes depending on the blade entrance angle βm.

Note that βm in FIG. 11 is (βm) ₁ > (β
m) ₂ > (βm) ₃ > (βm) ₄ and (βm) ₁ = 50
°. Therefore, the present invention is applied to the root-shaped airfoil shown in FIG.

Further, Bammert et al. Describe test results on various cascade configurations, and show changes in airfoil loss characteristics due to differences in airfoil thickness and blade inlet angle βm and inlet angle. I have.

[0017] Further, for a cascade having a small blade entrance angle βm and a small blade pitch t and a large turning angle θ as shown in FIG.
Uenishi: disclosed in ASME, 71-GT-34.

[0018]

However, when the blade entrance angle βm is larger than 90 [degrees] as shown in FIG. Restrictions are often a major factor, and unresolved techniques remain for high-performance cascades.

The present invention provides a cascade configuration in which the blade inlet angle βm, the blade outlet angle γm and the throat dimension S, which are the thermo-hydrodynamic design conditions, are satisfied in the prior art described above. It is an object of the present invention to realize a high-performance cascade configuration of the rotor blades of an axial flow turbine by designing to satisfy the condition on the intensity vibration over a wide range, and determining the cascade configuration.

[0020]

The above object can be achieved as follows.

That is, the present invention relates to a method in which an elastic fluid flows.
Axial Flow Turbine with Blade Entrance Angles Correspondingly Formed
The blade entrance angle is [90 + 233.4].
{0.3- (Bt) / t}] degrees
Where the pitch of the blade row of the rotor blade is t, the leading and trailing edges of the blade
Where B is the axial dimension of the cascade, and (B−t) / t
Is formed so as to be in the range of 0.01 to 0.3.
The purpose of this period is to be achieved.

Also, corresponding to the direction in which the elastic fluid flows in,
Axial turbine turbine blades with formed blade inlet angles.
And the blade inlet angle is [90 + 233.4.0.3− (B
−t) / t｝] degrees to 180 degrees
The pitch of the blade row of the rotor blade is t, and the leading edge and the trailing edge of the blade are
Assuming that the dimension in the cascade axial direction of B is B, (B−t) / t becomes
Formed to be in the range from 0.01 to 0.3
It is.

Also, corresponding to the direction in which the elastic fluid flows,
Axial turbine turbine blades with formed blade inlet angles.
The blade inlet angle is βm, the pitch of the rotor blade cascade is t,
When the dimension in the cascade axial direction of the leading edge portion and the trailing edge portion is B,
The following equation between βm and (B−t) / t:

[0024]

[Number 2] The portions of the wing in relation βm [degrees] = 90 [degrees] +233.4 {0.3- (B-t) / t} [degrees] ... ... (1), (B -t ) / T is 0.01
From 0.3 to 0.3
You.

[0025]

According to the present invention, first, the presence or absence of an optimum condition for the cascade configuration will be examined with reference to FIG. FIG. 12 is an explanatory diagram relating to a comparison of examples of cascade configurations, showing an example in which the blade inlet angle βm is substantially 90 degrees, and FIGS. 12 (a) and 12 (b).
And (c) show the blade pitch t and the throat dimension S
Are the same length, and the string length C and the wing width W
Are different. 12 (a), (b) and (c), the chord length C and the blade width W are different, and the blade row axial dimension B is different between the leading edge and the trailing edge of the blade. ing.

That is, in FIG. 12A, t>
B, t <B in (b), and t (B in (c). In this case, the flow in the flow path between the cascades is in a state as shown in FIG. That is, FIG. 13 is an explanatory diagram of the relationship between the cascade configuration and the flow, and FIG.
(c) is a cascade configuration corresponding to (a), (b) and (c) of FIG. 12, respectively.

In FIG. 13A, a separation region 11 is generated on the back side of the latter half of the flow path of the streamline 9, resulting in a flow condition in which the cascade performance is deteriorated. On the other hand, in FIG. In (c), no separation area is generated, and a normal flow state is obtained.

That is, comparing the superiority and the inferiority of the cascade performance in (a), (b) and (c) of FIG.
3 (a) has a drawback that a separation area occurs and a normal flow cannot be obtained, and FIG. 13 (b) shows a normal flow state.
Also, in (c), the airfoil is larger in (c) than in (b), and the contact distance between the wing surface and the fluid is longer, so that the frictional resistance is increased. I have. These facts suggest that the cascade configuration as shown in FIG. 12 has optimal conditions.

From the above examination, it is clear that the blade cascade configuration of the axial flow turbine has a high possibility of obtaining a high-performance cascade configuration even when the blade entrance angle βm is 90 ° or more.

In the present invention, the blade pitch and the axial dimension of the leading edge and the trailing edge of the blade are adjusted so that the flow in the inter-cascade flow path is optimized. The fluid force acting on the wing can be used effectively without impairing the row performance.

FIG. 14 shows the effect of the blade surface pressure distribution in the airfoil constituting the cascade. FIG. 14 is an explanatory diagram of the relationship between the cascade configuration and the blade surface pressure distribution, and FIGS. 14 (a), (b) and (c) show FIGS.
2, (a), (b) and (c).

In FIG. 14, the product of the hatched area and the blade width W surrounded by the hatched pressure distribution on the ventral side and the back side is the fluid force acting on the moving blade. It is shown to occur.

In the case of FIG. 14A, the area indicated by the hatched area is large, but as shown in FIG.
Is small. On the other hand, in the case of FIG. 14 (c), the area of the portion shown by oblique lines is small, but the blade width W is large as shown in FIG. 12 (c).

That is, the fluid force acting on the rotor blade is represented by the product of the area of the hatched portion and the blade width W. The superiority of the cascade configuration can be compared only by the magnitude of the fluid force. Is not sufficient, and it is necessary to avoid both the occurrence of the peeling region shown in FIG. 13A and the increase in the frictional resistance shown in FIG. 13C.

According to the present invention, the configuration of the blade cascade as shown in FIG. 13B can be improved, thereby improving the performance of the blade cascade.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is an explanatory view of each cascade in the embodiment of the present invention and the conventional example, FIG. 2 is an explanatory view of the flow in the embodiment of the present invention and the conventional example, and FIG. 3 is an embodiment of the present invention and the conventional example. FIG. 4 is an explanatory diagram of an airfoil loss coefficient of the embodiment of the present invention, FIG. 5 is an explanatory diagram of an optimum airfoil configuration of the embodiment of the present invention, and 4 is a ventral side. Numeral 10 denotes an expansion wave, δ denotes a deflection angle of a streamline, and others are the above-mentioned symbols. Bt = −t (B and t are both described above).

FIG. 1A shows an embodiment of the present invention, and FIG. 1B shows a conventional example. Here, the blade entrance angle βm> 90
The case of the degree will be taken as an example, and the two examples will be compared and described.

FIGS. 1 (a) and 1 (b) show the cascade configuration conditions in which the blade entrance angle βm and the blade width W are both equal and the S / t is almost the same.

In both examples, the dimension B in the blade row axial direction between the leading edge and the trailing edge of the blade is different from the blade pitch t, and in this embodiment, FIG. t <B, and t> B in the conventional example.

Therefore, even when the inlet angle βm and the throat size / blade pitch (= S / t), which are the thermal fluid design conditions, are the same, the cascade configuration is different and the cascade performance is different. Becomes This becomes apparent by comparing the flow conditions in the cascade.

FIG. 2 shows the state of the flow in the cascade shown in FIG. 1. FIGS. 2 (a) and 2 (b) show the flow states in FIG.
(b) respectively. FIG. 2A shows a case where t <B, which is a configuration condition of the cascade of the present embodiment, and the streamline 9 is in a smooth state along the inter-blade flow path shape.
In the case of the condition t> B shown in (b), the streamline 9 is deflected downstream of the throat size S, and the separation region 11 is generated, which greatly reduces the cascade performance.

FIG. 3 shows a comparison of such a flow condition with the pressure distribution on the wing surface.
While the back side is in a relatively good acceleration state, FIG.
In the conventional example shown in (b), the pressure suddenly drops at the inlet on the back side to become an accelerating flow, after which a separation region occurs without a decrease in pressure, and the influence of the viscosity of the fluid increases, This shows that the airfoil loss increases.

Such a state of the flow between the blades in the conventional example has a remarkable effect even in the thermal fluid design condition in which the speed reaches the sonic speed in the portion of the throat size S and becomes supersonic downstream thereof. Since the pressure drop at the trailing edge 8 of the ventral wing is sharp, the region of the expansion wave 10 (shown by a broken line in FIG. 2) due to the relationship of the Prandtl-Meyer function is widened.
The deflection angle δ of the streamline shown in (b) and the separation area 11 become large, resulting in a significant decrease in the cascade performance.

That is, in the present embodiment, high performance is achieved by configuring the cascade so as to satisfy the condition of t <B shown in FIG. FIG. 4 specifically shows this relationship. In FIG. 4, the vertical axis represents the airfoil loss coefficient indicating the performance of the cascade, and the horizontal axis represents Δt / t. Here, Δt = B−t.

Also, the curves of the _three blade entrance angles βm, ie, (βm) ₁ , (βm) ₂ and (βm) _{3 in} the figure are (βm) ₁ > (βm) ₂
> (Βm) ₃ , but shows that the characteristics of the airfoil loss coefficient differ depending on the blade inlet angle βm. Has the characteristic that the larger the blade entrance angle βm, the smaller the value, and the value of Δt / t shifts to the smaller one.

Δ at which the minimum airfoil loss coefficient reaches a minimum value
optimal value of the t / t Δt / t, i.e. as (Δt / t) _0, if indicated by the relationship between the (Δt / t) ₀ and blade inlet angle .beta.m, 5
And the blade entrance angle βm in the range of the present embodiment is 9
Above 0 [degree], (Δt / t) ₀ is 0.01 to 0.30
And the value of (Δt / t) ₀ decreases as the blade entrance angle βm becomes larger than 90 °. More specifically, the optimal line in FIG.

[0048]

Βm [degree] = 90 [degree] +233.4 {0.3− (B−t) / t} [degree] (1)

In the characteristic of the airfoil loss coefficient shown in FIG. 4, the larger the blade entrance angle βm, the smaller the increase of the loss coefficient at a large value of Δt / t.
The application range of t / t is widened.

However, in the range of Δt / t <0, as described above, an abnormal flow is generated in the cascade flow path, so that the practical range is the applicable range in FIG. The applicable range is Δt / at which a substantial effect of the present invention can be obtained.
The range of t is 0.01 to 0.3, and the applicable range of the blade entrance angle for each Δt / t is a large range from the blade entrance angle βm on the optimal line shown by the equation (1) to 180 [degrees]. Specified in the range.

In this embodiment, the cascade performance is 20 to 4
0% could be improved.

[0052]

According to the present invention, in the axial flow turbine, the flow path between the moving blades can be improved by optimizing the blade pitch and the axial dimension of the leading edge and the trailing edge of the moving blade. Thus, the performance of the cascade can be improved. This is particularly effective in a cascade configuration in which the blade entrance angle is 90 degrees or more, and can improve the cascade performance by 20 to 40%.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of each cascade in an embodiment of the present invention and a conventional example.

FIG. 2 is an explanatory diagram of a flow in an embodiment of the present invention and a conventional example.

FIG. 3 is an explanatory diagram of an airfoil pressure coefficient according to an embodiment of the present invention and a conventional example.

FIG. 4 is an explanatory diagram of an airfoil loss coefficient according to the embodiment of the present invention.

FIG. 5 is an explanatory diagram relating to an optimal airfoil configuration according to the embodiment of the present invention.

FIG. 6 is an explanatory view of a rotor blade shape of a conventional axial flow turbine.

FIG. 7 is an explanatory diagram of an airfoil at each position in a blade length direction in a conventional example.

FIG. 8 is an explanatory diagram relating to a configuration of a conventional cascade.

FIG. 9 is an explanatory diagram of a blade inlet angle and a blade outlet angle of a conventional example.

FIG. 10 is an explanatory view of each cascade of a root portion and a tip portion in a conventional example.

FIG. 11 is an explanatory diagram of a conventional airfoil loss coefficient.

FIG. 12 is an explanatory diagram related to a comparison of cascade configuration examples.

FIG. 13 is an explanatory diagram of a relationship between a cascade configuration and a flow state.

FIG. 14 is an explanatory diagram of a relationship between a cascade configuration and a blade surface pressure distribution.

[Explanation of symbols]

12: airfoil, βm: blade entrance angle, t: blade pitch, B: axial dimension of the leading edge and trailing edge of the blade.

Continuation of the front page (72) Inventor Yoshiaki Yamazaki 502, Kandachicho, Tsuchiura-shi, Ibaraki Machinery Research Laboratory, Hitachi, Ltd. (56) References JP-A-57-105503 (JP, A) JP-A-51-145008 (JP) JP-A-52-133402 (JP, A) U.S. Pat. No. 3,975,462 (US, A)

Claims (3)

(57) [Claims] 1. A blade of an axial flow turbine having a blade inlet angle formed corresponding to a direction in which an elastic fluid flows, wherein the blade inlet angle is [90 + 233.4 ｛0.3- (B−
t) / t｝] degree or more,
The row pitch is t, the dimension in the cascade axial direction between the leading edge and the trailing edge of the blade.
When the method is B, (B−t) / t is 0.01 to 0.1.
Rotor blades of an axial flow turbine, wherein the forming the this to be in the range of up to 3. 2. A blade of an axial flow turbine having a blade inlet angle formed corresponding to a direction in which an elastic fluid flows, wherein the blade inlet angle is [90 + 233.4 ｛0.3- (B−
t) / t｝] degrees to 180 degrees
The pitch of the blade row of the rotor blade is t, the leading edge and the trailing edge of the blade
Assuming that the dimension in the cascade axial direction is B, (B−t) / t is
Rotor blades of an axial flow turbine, characterized that you formed to be in the range from 0.01 to 0.3. 3. A blade of an axial flow turbine having a blade inlet angle formed corresponding to a direction in which an elastic fluid flows, wherein the blade inlet angle is βm, the pitch of the blade cascade is t, and Before
When the dimension in the blade axis direction between the edge and the trailing edge is B, βm
The following equation between the (B-t) / t, ie, ## EQU1 ## βm [degrees] = 90 [degrees] +233.4 {0.3- (B-t) / t} of [degrees] The part of the wing in the relationship is defined as (Bt) / t is 0.01
Rotor blades of an axial flow turbine, characterized that you was formed to have a range of up to 0.3 from.