JPS5885367A - Francis water wheel - Google Patents

Abstract

PURPOSE:To improve the vibration strength by defining such that the specific water wheel speed ns<=170, ns>=20, 15/H<1/2> while Zg=20, 22, 24, 30 when Zr=15 assuming the number of the runner vane is Zr, the maximum head of the water wheel is H and the number of the guide vane is Zg. CONSTITUTION:In a Francis water wheel, the size of the main machine can be reduced in the range of the water wheel specific speed ns<=170 while the efficiency is improved by increasing the specific speed, but the rigidity of the runner will deteriorate to lower the inherent vibration thus to susceptible to resonate with the frequency of the hydraulic exciting force due to the relative function betwen a guide vane and a runner. The resonation can be avoided by properly selecting Zg from five pairs such as Zg=20, 22, 24, 30 for Zr=15 and Zg=22, 24, 26, 32 for Zr=16, etc. assuming Zr is the number of the runner vane while Zg is the number of the guide vane.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a 7-Rancis water turbine that improves the reliability of vibration strength and achieves a smaller main engine and faster speed.

Figure 1 shows a typical example of a 7 Rancis turbine. In FIG. 52, reference numeral 1 indicates a rotating shaft, and a runner 2 is fixed to the lower end of this rotating shaft l, and this runner 2 is formed of a crown 21m, a band 2'b, and a plurality of blades 2c. . On the other hand, a plurality of guide vanes 3 are provided in the fixed flow path on the outer peripheral side of the runner 2.
are arranged in a circumferential direction in a two-way arrangement, and are formed to efficiently guide the flow from the kite vane to the launch during operation of the water turbine (τ direction). Here, the number of blades of runner 2 Zr
Conventionally, the number of blades Zf of the guide vane has been appropriately selected from the viewpoint of performance and ease of construction. However, in recent water turbines, the main engine has become larger in capacity and faster in order to improve economy, and the influence of the mutual interference phenomenon caused by water pressure pulsations between the launch and the guide vanes (2) on the vibration strength of the launch has been increasing. How to improve the reliability of the vibration strength of the launch under such severe usage conditions has recently become a focus of attention as a problem to be solved.

Next, we will explain the hydraulic excitation force acting on C Niranchi.

When the water turbine is in operation, the water flowing from the guide vanes 3 becomes a fluctuating flow in the circumferential direction by the number of guide vanes I: cyclical 1; Therefore, if the fourth blade of the runner is layered (<204), it will be subjected to a hydraulic excitation force that fluctuates 1-22 times during one revolution, and its frequency h) will be easily C/hmN-z, /6o. (H
ll) It turns out that (1) is obtained. Also 2
The blades other than 204 f) receive the same hydraulic excitation force with a certain phase lag compared to the blade C2, and a vibration phenomenon occurs in the launch as a whole due to a plurality of excitation forces g2 with a certain phase difference.

On the other hand, it has been experimentally determined that the same vibration mode of the runner itself is characterized by the diameter mode of the disk. In other words, as shown in Fig. 2, the number of diametral nodes (
1), but in 2, there are two peaks and two valleys H in the circumferential direction.

In conventional Francis turbines, the natural frequency of the launch with equal diameter mode numbers is C2, which is higher than the hydraulic excitation force frequency in equation (1), and this is a phenomenon in which both frequencies match and resonate. However, as small cylinder speed machines have become widely adopted due to the above-mentioned economic efficiency, the danger of resonance due to the above-mentioned frequency coincidence C2 has become a problem.

In the present invention, even if this resonance condition occurs, by appropriately controlling the phenomenon of multi-point excitation of the hydraulic excitation force described above, the vibration stress generated in the runner can be significantly reduced, and the strength can be improved. The purpose is to provide a 72-inch water turbine with significantly improved reliability.

The present invention will be explained below. Taking into account the harmonic distribution of the hydraulic excitation force and transforming equation (1), we get ω±n−Zp・Ω
(2). Here n=N
/6g, n is the harmonic component of the excitation force, n=1.2.
1i value of ..., ω is the frequency of the excitation force 0 In Fig. 3, zr=6. The layout diagram for the combination of zt=~20 is shown, where the positions ψ4 and 1 of the fourth blade (204)
The displacement of vibration excited by the excitation force when the position 0↓ of the second guide vane (3L) passes each other, )A is 14=6asL (9'-94 )m(a)(t-” (
#4-ψJ)) (111Ω) Here, a is the amplitude and 1 is the diameter node mode.

ψ4 and θ↓ indicate the following.

91a =-” (A-1): (The position of the fourth blade is shown in the rotational system.) is shown in the static system.) The transmission displacement received by the blades other than the A-th blade in the runnacy arrangement b table is expressed by the formula (Similar to the button, C2 is led, and as a whole tiZ
Considering ω in equations (2) and (4), which can be expressed as the sum of r pieces as shown in equation (4), the condition for exciting the vibration displacement J is ω 10 = = mZrΩ (6) can get. Here, m is an arbitrary integer. That is, the formula (
2) Forced vibration frequency ω of excitation force and number of runner blades Z
When r satisfies equation (6), the launch vibration is excited. As for the vibrations due to other frequencies C2, the vibrations from each blade position cancel each other out, and the vibrations are not excited δ. Equation (6l: Substituting Equation (2) and dividing both sides by Ω gives nZp = m
Zr (6) That is, equation (6)
It is sufficient to consider combinations of Zr and 2fj so as not to satisfy the following.

In the case of a general 5-Nearansis turbine, the attenuation in water is large (
, n=1, it is sufficient to consider the basic vibration excitation force, and it has been verified by actual measurement results.

Also, as the natural vibration mode of lunch, 1ij = 2.3゜4
If the natural frequency of the diameter node is likely to match the frequency of the excitation force, it is sufficient to avoid this range.

Furthermore, considering the performance, structure, ease of manufacture, etc. for zr and zI, for a 7 Rancis water turbine, Zr = an integer of 11 to 19 Zg '' an integer of 16 to 32 (however, Zt > Zr + 1
) is limited to.

Figure 4: This shows the actual use of Francis turbines. The -7 Lances turbine is a model that can be applied to a wide range of applications, from high head to low head. At 1FR head (b), the shape around the launch is significantly different. The problem to be solved by the present invention is the mutual interference between the launch and the guide vane, and the closer the two are to the iA drop machine (α), the more the problem becomes. In addition, the hydraulic excitation force acting on the runner changes almost in proportion to the head, so high-head machines are difficult in this respect as well. On the other hand, there is a tendency to make equipment smaller and faster in terms of economy, as shown in Figure 5. As shown, the applied head g is the same year after year.
＝There is a tendency for the specific speed of the water turbine to be large, and ＜Hibiki:
In the range of n-≦170, the advantage is significant for the reasons shown below.
Do) is large, and by increasing n, Do can be reduced in width by 42, making it possible to downsize the entire main engine, making it possible to increase the capacity, and improving the reliability of the main engine.

(2) For 7 Rancis water turbines, na = 170 mini 170 ≦
Since it has the characteristic that y is the highest, s na < 17
By increasing the specific speed below 0, the efficiency of the water turbine can be increased, which is effective in terms of energy conservation.

However, when the main engine is made to operate at a high speed and specific speed, the rigidity of the two-way launch decreases, and the natural frequency of the runner decreases.

On the other hand, as can be seen from equation (1), as the speed increases, the frequency of the hydraulic excitation force increases, and there is a risk that a resonance phenomenon will occur due to coincidence with the launch natural frequency.

Figure 6 shows an example of trial calculations for a 7 Rancis water turbine with n, = 100m-KW. Figure 4 (-shows)
6≦2015/Our current lunch is 0 points and 1 in Figure 6:
Yes, the launch frequency (n) is sufficiently far away from the hydraulic excitation force frequency (ha), which is on the safe side (-).

However, if you try to increase the speed by increasing n at the same head, the 6th
As shown in the figure, there is a risk that the re-vibration frequencies will match at the zero point and a resonance phenomenon will occur.

On the other hand, the number of guide vanes is preferably an even number from the viewpoint of ease of construction and installation, and the number of runner blades is Zr≧15 in the range of n-≦170 from the viewpoint of performance.

Therefore, when applying the effects of the present invention to practical use, the formula (
The following combination of Zr and Zp is selected from the fact that the condition 6) is not satisfied and from the above-mentioned considerations. That is, Zr =
When 15 Zp ” 2L 22e 24e 30
When zr-16 Zp depth 22.24.26.32Zr
When = 17 Zy -22m 24.26.28
Zr = 18'@Zytomi 24.26.28.
When 30zrW 19 Zp -24, 26, 28,
Zr and Zp are determined by one of the 30 and 32 combinations.

As described above, the present invention solves the problems with the strong 1itTkJ of runners of Francis turbines, which will become faster and faster in the future, and increases capacity and performance with a highly reliable integrated launch.
It has the effect of making it possible to provide equipment that can exhibit a number of advantages, such as energy saving effects due to the second aspect and economic effects due to miniaturization, without impairing reliability.

[Brief explanation of drawings]

Fig. 1 is a plan view and a longitudinal view showing a 7 Rancis water turbine, Fig. 2 is an explanatory diagram showing a typical example of the eigenmode of the lunch,
Figure 3 is an explanatory diagram of the multi-point vibration phenomenon, and Figure 4 is a diagram showing the applicable range of the recent 7 Rancis turbine. Fig. 5 is a sectional view showing the relationship between the shape of the Francis turbine and specific speed, and Fig. 6 is a diagram showing the relationship between the hydraulic excitation force frequency and the Lunch natural frequency. 1...Rotating shaft 2...Runner 2a...Crown 2b...Band 2c...Blade,
3...Guide Bene-Me (7317) Agent Patent Attorney Noriyuki Chika (and 1 other person) Figure 1, Figure 2! , 2 No. 3 No "4 Fig. 3 Fig. 4 Fig. N5 (rn-KvJ) Fig. 5 (b)

Claims (1)

[Scope of Claims] A launch formed by a number of blades, a hub and a shroud ring surrounding the upper and lower surfaces of the blades, and a guide vane provided on the fixed flow path side adjacent to the launch. , where Zrs% is the number of blades in the launch, the maximum head of the water turbine is H (m), p (kw) is the maximum output of the water turbine, and N (rp, m) is the rotation speed, then the specific speed of the water turbine is ns (= Nu /H') is n-≦
170 (m-kw) and n#≧2015/@ (m-k
V) and %Zr and ZJF are set to any one of the combinations specified below. Zr = 15: Zy = 20.22124.30
Zr −16: z7 = 22.2426* 32Z
r = 17: Zy = 22.24.26.28
Zr "" 18: Zy =24+ 26* 28
e 3GZr = 19: Zg = 24.26.
28.30.32