JPS6250664B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a single speed reversible multi-stage pump water turbine,
In particular, the present invention relates to a single-speed reversible multi-stage pump water turbine that can perform high-performance operation during steady operation.

In recent years, there has been a trend to construct pumped storage power plants at high head locations, and the demand for multistage pump turbines is increasing. A multistage pump-turbine is equipped with a runner at each stage from the highest pressure stage to the lowest pressure stage, and each stage is connected by a return passage, and the guide vanes provided on the outer periphery of the runner at each stage Therefore, the state of water flow in each stage is controlled to control the operating state.

However, in such a multistage pump-turbine with a complicated flow path configuration in which each stage from the highest pressure stage to the lowest pressure stage is successively connected in series via a return passage, the outer periphery of the runner of each stage It is difficult to provide a guide vane at each step and connect an opening/closing operation mechanism to the guide vane at each step to perform the opening/closing operation. In particular, pump turbines with three or more stages are extremely difficult due to structural constraints, which poses a problem in practical use.

For this reason, conventional multi-stage pump turbines usually have a structure in which only fixed vanes are installed around the outer periphery of the runner of each stage, and the opening of the water inlet remains constant and cannot be changed, and the opening and closing of the inlet valve is controlled. The operating conditions are controlled by adjusting the water flow rate. Since it is not possible to appropriately adjust the water flow according to the flow rate at the outer periphery of the runner in each stage, hydraulic performance deteriorates uniformly in each stage when entering the operating range of small and large flow rates away from the design point. As a result, the hydraulic machine is operated with a reduced overall hydraulic performance.

As described above, the conventionally commonly used multi-stage pump-turbine, in which fixed vanes whose water openings cannot be adjusted are installed at each stage, and the flow rate is adjusted and controlled by an inlet valve, results in a decrease in hydraulic performance. All of them had problems such as being undesirable.

Therefore, the present inventor developed a multi-stage pump-turbine in which a movable guide vane was first provided only on the highest pressure stage so that the water mouth opening degree could be adjusted, and fixed vanes were arranged on the other low pressure side stages. have provided.
In a multi-stage pump turbine equipped with a movable guide vane that can change the water inlet opening only in the highest pressure stage, which is easy to put into practical use due to its configuration, the overall hydraulic characteristics of each stage during steady operation are: This is a huge improvement over conventional multi-stage pump turbines that use valves to adjust the flow rate. However, since it is not possible to appropriately adjust and control the water flow condition according to the flow rate in the low-pressure side stage, the hydraulic performance must be relatively lower than in the case of a multi-stage pump turbine, which has movable guide vanes at each stage, which is ideal in terms of hydraulic performance. The reality is that it is not possible.

Therefore, the problem is how to improve the overall hydraulic performance of each stage in a multistage pump turbine with a practical structure in which a movable guide vane is installed only in the highest pressure stage. There is a strong demand for technology that can solve this problem.

Therefore, an object of the present invention is to improve the overall hydraulic performance of each stage by increasing the hydraulic performance of the low-pressure side stage during steady operation of a multi-stage pump turbine equipped with a movable guide vane only in the highest pressure stage. The purpose of the present invention is to provide a single-speed reversible multi-stage pump water turbine that enables the following.

According to the present invention, the above object is achieved by connecting the stages from the highest pressure stage to the lowest pressure stage in series through return passages, and attaching the water port opening to the outer periphery of the runner of the highest pressure stage. A movable guide vane is provided that can change the rotation direction, while a fixed vane with a constant water opening is installed on the outer periphery of the runners on the other low-pressure side tiers. In a single-speed reversible multi-stage pump-turbine in which the turbine and pump are operated at the same rotational speed by changing only the By configuring the runners on the low-pressure side to be within the range of 0.86 to 0.96 times the outer diameter of the runner blades on the lower side, the hydraulic performance of the low-pressure stage runner is generally equal to the hydraulic performance of the high-pressure stage runner. Since it is possible to shift to the lower head side where the rotational speed is higher, compared to the conventional case where the runner blades have the same outer diameter at each step,
In particular, the overall hydraulic performance will be improved through high-performance operation of the water turbine power generation operation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of a single-speed reversible multi-stage pump turbine according to the present invention will be described below with reference to the drawings.

In order to facilitate understanding of the present invention, FIG. 1 shows a Francis-type two-stage pump-turbine as an example of a multi-stage pump-turbine, in which a single main shaft 1 has a high-pressure stage runner 2 and a low-pressure stage runner 2. A stage runner 3 is fixedly spaced apart from the stage runner 3 in the axial direction. The high pressure stage runner 2 is surrounded by an upper cover 4 and a lower cover 5, while the low pressure stage runner 3 is surrounded by an upper cover 6 and a lower cover 7, forming a high pressure stage runner chamber 8 and a low pressure stage runner chamber 9. . The above high pressure stage runner chamber 8
and the low pressure stage runner chamber 9 are connected by a return passage 10.

Further, a spiral casing 11 is disposed outside the high pressure stage runner chamber 8, and the spiral casing 11 communicates with the high pressure stage runner chamber 8. 14.

Furthermore, a movable guide vane 15 is provided on the outer periphery of the high-pressure stage runner 2, which can change the water port opening, while a fixed guide vane 16 is provided on the outer periphery of the low-pressure stage runner 3, which does not allow the water port opening to be changed. It is provided. In this example, a two-stage pump-turbine is used, but in a multi-stage pump-turbine with three or more stages,
A movable guide vane is provided only on the outer periphery of the runner at the highest pressure stage that communicates with the whirlpool chamber 12, and fixed vanes are provided at all of the lower pressure stages below.

The movable guide vane 15 of the highest pressure stage section includes:
An operating mechanism is connected, and the opening degree is adjusted by a control device for steady operation.

When operating the two-stage pump turbine configured as described above, water flows from the penstock 14 into the spiral casing 11 connected to the penstock with the inlet valve 13 open, and this water flow flows into the high pressure stage section. The movable guide vane 15 of
6. The water flows through the low-pressure stage runner 3 and then into the suction pipe 17 connected to a discharge channel (not shown).

On the other hand, in the case of pump operation in which the runner rotates in the opposite direction at the same rotational speed as the water turbine, the water flow pumped by the low-pressure stage runner 3 is sucked out through the reverse route as in the case of the water turbine operation described above. It flows from the pipe 17 to the penstock 14.

In this way, the overall hydraulic performance of a single-speed reversible multistage pump-turbine in which each stage is connected in series through a return passage is given by combining the hydraulic performance of each stage as a single-speed reversible single-stage pump-turbine. It will be done. Therefore, when considering the hydraulic performance problems of single-speed reversible multi-stage pump-turbines, it is first necessary to accurately understand the hydraulic performance problems of single-speed reversible single-stage pump-turbines. Therefore, we will consider it next.

Generally, in a single-speed reversible single-stage pump-turbine, the rotational speed of the pump-turbine is N (rpm), the effective head of the turbine is Ht (m), the efficiency is ηt, the total head of the pump is Hp (m), and the efficiency is As ηp, the envelope of the efficiency curve of each guide vane opening degree with respect to the unit rotational speed N/√, N/√ is illustrated as shown in FIG. 2 for the water turbine and the pump.

In other words, as shown in Figure 2, the unit rotational speed N/√ ₀ that gives the highest efficiency point of the water turbine and pump does not match with N/√ ₀ , and N/√ ₀ is always larger. This is one of the unavoidable hydraulic performance problems in reversible pump turbines. Efforts have been made to make this difference as close as possible, but in practice it usually falls within the following range.

In other words, as shown in Figure 2 and Equation (1) above, in a single-speed reversible pump-turbine, the maximum efficiency point of the pump is far away from the maximum efficiency point of the turbine in terms of unit rotational speed ratio. , the efficiency during pump operation at a unit rotational speed corresponding to the maximum efficiency point of the water wheel is extremely low, and similarly, the efficiency of the waterwheel at a unit rotational speed corresponding to the maximum efficiency point of the pump is also extremely low. For this reason,
If the operating conditions of the pump-turbine are determined so that the pump can operate at or near its maximum efficiency at the standard operating water level of a pumped storage power plant, as is normally done, the conditions shown in Figure 2 and Equation (1) are Due to constraints related to hydraulic characteristics, the water turbine is operated under a high unit rotational speed state far from the maximum efficiency, in other words, the standard operation is performed in a region with low hydraulic performance on the lower head side than the operating head Ht ₀ , which corresponds to the maximum efficiency state. You will have no choice but to choose the state. In this way, when considering the hydraulic characteristics of a pump-turbine, the unit rotational speed (N/√
, N/√) has an important meaning,
Next, we will discuss the correlation between this unit rotational speed and the outer diameter D of the runner blade, which basically controls the hydraulic characteristics of the pump-turbine.

Generally, at the highest efficiency point of the pump, which represents the design point in terms of the hydraulic characteristics of a pump-turbine, the rotational speed of the runner is N (rpm), the outer diameter of the runner blade is D (m),
The outer peripheral speed of the runner blade is u (m/s), the outer peripheral speed coefficient of the runner blade is φ, and the total head of the pump is Hp.
(m) and the gravitational acceleration is g (m/s ² ), the following equations (2) and (3) are given in terms of hydraulic power.

u=πDN/60=φ√2 ₀ …(2) or φ=(π/60√2)(N/√ ₀ )D = (1/√2)(u/√ ₀ …(3) On the other hand , the flow rate at the pump's highest efficiency point is Qp (m ³ /
s), the specific speed Ns, which is a basic condition for pump-turbine design, is given as Ns=N・(Qp)〓/(Hp ₀ )〓. According to the results of a model hydraulic characteristic test conducted by systematically modifying the outer diameter D of the runner blades in a pump-turbine designed under the condition of a certain specific speed Ns, the reduction change in the outer diameter D of the blades On the other hand, the unit rotational speed N/√ ₀ increases and changes, and it has been confirmed that within the range where practical performance can be obtained, both are in a reciprocal proportional relationship as shown by the following equation (4).

(N/√ ₀ )・D=constant ...(4) This means that if the blade outer diameter D is made small in a pump turbine designed under the condition of a given specific speed Ns, it will be within the range where practical performance can be obtained. This shows that the blade outer circumferential velocity coefficient φ in the above equation (3) hardly changes, and therefore the result brings about the relationship in the above equation (4).

In addition, when the outer diameter D of the blade is reduced in this way, the unit rotational speed N/√ of the pump maximum efficiency point is
₀ , the unit rotation speed N/√ ₀ at the highest efficiency point of the water turbine also increases, and each unit rotation speed ratio is within the range defined by equation (1) above, and the hydraulic characteristics of both the pump and the water turbine are It is possible to shift the overall rotational speed to the high unit rotational speed side, that is, to the low head side.

Next, based on the above-mentioned results of the study on the basic problems of hydraulic characteristics unique to single-speed reversible single-stage pump turbines, we installed a movable guide vane that can change the opening of the water port on the highest pressure stage, and installed a movable guide vane on the low pressure side stage. The conventional case is a single-speed reversible multi-stage pump-turbine with fixed vanes whose water openings cannot be changed, in which the runner blades in each stage have the same outer diameter and are hydraulically similar (Fig. 1). Regarding the problems in hydraulic characteristics when D ₁ = D ₂ ), the first
This will be explained with reference to the two-stage pump turbine shown in the figure. In this case, the relationship between the hydraulic characteristics of each stage during steady operation of the water turbine is shown in FIG. 3. In Figure 3, H ₁ is the effective head of the high-pressure stage, H ₂ is the effective head of the low-pressure stage, Q is the flow rate, and the values with a suffix 0 are for the standard operating condition (□0 in the figure). , a ₀ is the water port opening of the guide vane in the standard operating state, a with a positive integer subscripted (for example, a ₁ ) is the high pressure stage water port opening when the opening is more than the standard opening, and a is the negative The subscript with an integer (for example, a _-1 ) is the high-pressure step water mouth opening when the opening is slightly opened according to the standard opening, and Δη is the relative efficiency difference of the water turbine expressed as the relative difference from the maximum efficiency of the water turbine.
In Figure 3, the horizontal axis shows the flow rate ratio Q/Q ₀ , and the vertical axis shows the effective head ratio H ₁ of the high pressure step and the low pressure side step.
~ H ₁₀ and H ₂ /H ₂₀ are respectively taken, and the relationship between the hydraulic characteristics of the effective head and the flow rate is displayed for each stage. Therefore, the total effective head as a two-stage pump turbine is calculated at each stage. It is given by adding up the effective heads of each section. In Fig. 3, in the standard operating state □0 in which the inlet valve 13 is fully opened and each stage is in a hydraulically equivalent operating state, the effective head of each stage is the total effective head H acting on the two-stage pump turbine. ₀
It is equal to dividing into two equal parts, and becomes as follows.

What should be especially noted here is that due to the above-mentioned problem with the hydraulic characteristics peculiar to single-speed reversible pump turbines, the reference operating state of each stage section is □0 (operating head
H ₁₀ , H ₂₀ ) must be selected in an area where the hydraulic performance is relatively low and on the side with a much lower head (on the side where the unit rotational speed is larger) than the highest efficiency state of the turbine (△η = 0). . Therefore, in Fig. 3, when closing the water port opening of the movable guide vane in the high pressure step while keeping the water port opening in the low pressure side section constant, the following formula is used.
Based on the head relationship given by (6), the operating state of the high-pressure stage section can follow the trajectory □0 → □B, where the hydraulic performance is relatively high, but on the other hand, when the water mouth opening is fixed, The low-pressure side step section follows a trajectory of □0 → □A above a constant opening degree a ₀ , and its hydraulic performance, on the contrary, decreases more and more.

In this way, in the operating range where the flow rate is smaller than the standard operating condition □0, the hydraulic performance of the high-pressure stage section improves, but the hydraulic performance of the low-pressure side stage section conversely continues to decline. This means that no improvement in performance can be expected.

Therefore, in the present invention, the highest pressure stage part, which can perform high-performance water turbine operation in a small flow area by controlling the highest pressure stage part movable guide vane, is moved to the low head side (unit rotation The runners are formed so as to perform standard operation of the turbine in the area (high speed side), but for the low-pressure side stage in question, which has fixed vanes that cannot change the opening of the water port, the outside of the blades of the low-pressure stage runner is By reducing the diameter, the overall hydraulic characteristics are shifted to the low head side where the unit rotational speed is large, and the maximum efficiency of the turbine can be achieved during standard operation of the turbine. By forming the runners to enable performance operation, the overall hydraulic characteristics of each stage are improved.

A specific embodiment of the present invention will be described with reference to a single-speed reversible two-stage pump water turbine shown in FIG. In FIG. 1, the pump efficiency η under the single-stage hydraulic characteristics of the high-pressure stage runner 2 equipped with the movable guide vane 15
The unit rotational speed ratio between p and the turbine efficiency ηt at each maximum efficiency point is 1.04 to 1.16 (see formula (1)), and by reducing the outer diameter D of the blades of the low-pressure stage runner 3, the low-pressure The unit rotational speed N/ _√0 of the stage runner 3 is increased to shift the single stage hydraulic characteristics of the low pressure stage runner 3 to the low head side compared to the high pressure stage runner 2 (see equation (4)).

In this case, the relative relationship between the blade outside diameter D ₁ of the high-pressure stage runner 2 and the blade outside diameter D ₂ of the low-pressure stage runner 3 is expressed by equation (4) that gives the relationship between the blade outside diameter D and the unit rotational speed N/√ ₀ . It is given as the following equation (7). however,
The number 1 represents the high-pressure stage, and the number 2 represents the low-pressure stage.

In equation (7), the right-hand side is the unit rotational speed (N/√ ₀₂ ) of the high-pressure stage where the outer diameter of the runner blade remains unchanged when the unit rotational speed (N/√ 02 ) of the low-pressure stage increases.
₀₁ ) as the denominator (N/√ ₀₂ )/
It corresponds to the reciprocal of (N/√ ₀₁ ), and the left side is the reduction ratio D ₂ / of the runner blade outer diameter D ₂ of the low-pressure stage with the runner blade outer diameter D 1 of the high-pressure stage as the denominator, which is the _same as before.
Equivalent to D ₁ .

In other words, Equation (7) shows that when increasing the unit rotational speed (N/√ ₀₂ ) of the low-pressure stage, the necessary reduction ratio D ₂ /D ₁ of the outer diameter D ₂ of the runner blade of the low-pressure stage is equal to the unit rotational speed. It shows that it is given by the reciprocal of the increase ratio. In this case, the runner blade outer diameter D ₁
However, the single-stage hydraulic characteristics of the high-pressure stage section are unchanged from conventional ones, and as mentioned above, the maximum efficiency unit rotational speed of the turbine is N/√
₀₁ is pump maximum efficiency unit rotational speed N/√ ₀₁
becomes smaller, and the relative ratio of N/√ ₀₁ and N/√ ₀₁ is 1.04 to 1.16 as given by equation (1) above.
The basic problem is that the water turbines are forced to operate at low performance. Therefore, considering the situation of the high-pressure stage, how can the reduction ratio of the outer diameter of the runner blade be reduced in the low-pressure stage?
The important point is whether to determine D ₂ /D ₁ and increase the unit rotational speed N/√ ₀₂ .

Therefore, in this embodiment, as mentioned above, in the high pressure stage section, the maximum efficiency unit rotational speed of the water turbine is N/√
₀₁ is pump maximum efficiency unit rotational speed N/√ ₀₁
The relative ratio of N/√ ₀₁ and N/√ ₀₁ is 1.04 to 1.16 times smaller. Therefore, as a target for increasing the unit rotational speed N/√ ₀₂ in the low-pressure stage, the increase ratio is higher than that of the high-pressure stage. The purpose is to specify the relative ratio to be equal to the above relative ratio, 1.04 to 1.16 times. On the other hand, the reduction ratio of the outer diameter _D2 of the low-pressure stage runner blade required to achieve this increase ratio of 1.04 to 1.16 times is calculated by adding the reciprocal of the increase ratio of 1.04 to 1.16 to the right side of equation (7), as described above. Since it can be obtained by substitution, the relative relationship between the outer diameters of the runner blades is finally given as in equation (8).

Equation (8) is the outer diameter of the runner blade of the runner in the low pressure stage.
D ₂ is 0.86 to 0.96 of the outer diameter of the runner blade of the high pressure stage D ₁
This means setting it to twice the range.

In this case, the hydraulic characteristics of each stage are shown in Figure 4 when the turbine is operating, and Figure 5 when the pump is operating.
Each is shown in the figure. In other words, the outer diameter of the blades of the low-pressure stage runner 3 with fixed vanes is the outer diameter of the blades D ₁ of the high-pressure stage runner 2 with movable guide vanes.
If the runner of each step is configured by reducing D ₂ within a specific range defined by equation (8), and the opening degree of the water port of the movable guide vane 15 provided only in the high-pressure step is adjusted and controlled, In water turbine power generation operation where high efficiency operation is strongly required, as is clear from the trajectory of the turbine operation status at each stage shown in Figure 4, the low pressure side stage where the overall performance characteristics have been shifted to the low head side. Since the operation is more efficient than in the conventional case (see FIG. 3) from the standard operating state □0 to the small flow rate region, the overall hydraulic characteristics of each stage can be significantly improved. In addition, in the case of pump operation, as shown in Figure 5, compared to the conventional case (when the outer diameter of the runner blades is the same in each stage), the pump performance on the high head side is particularly poor, and the overall performance characteristics are on the low head side. There is a tendency for the low-pressure stage runner 3, which has been moved to the In terms of overall performance, the pump can be operated at the same level of pump performance as the conventional case.

As described above, the present invention arranges a movable guide vane only in the highest pressure stage part, and provides fixed vanes in the remaining low pressure stage part to adjust the outer diameter of the blades of the highest pressure stage runner and the low pressure stage runner. The extremely simple structure and control, in which the runners of each stage are configured with relative relationships within a specific range, and controlled only by the movable guide vanes of the highest pressure stage, allows Hydraulic performance can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing the structure of a two-stage pump-turbine according to an embodiment of the present invention, FIG. An explanatory diagram showing the relationship between the water turbine characteristics of each stage in a multi-stage pump-turbine, FIG. 4 is an explanatory diagram showing the relationship between the turbine characteristics of each stage in a multi-stage pump-turbine according to an embodiment of the present invention, and FIG. FIG. 2 is an explanatory diagram showing the relationship between pump characteristics of each stage in an example multistage pump turbine. 1... Water turbine main shaft, 2... High pressure stage runner, 3...
Low pressure stage runner, 10... return passage, 11... spiral casing, 13... inlet valve, 14... penstock, 15... movable guide vane, 16... fixed guide vane.

Claims (1)

[Claims] 1 Each stage from the highest pressure stage to the lowest pressure stage is connected in series by a return passage, and a movable guide vane that can change the opening of the water port is installed around the outer periphery of the runner of the highest pressure stage, while the low pressure side A fixed vane with a fixed water mouth opening is installed on the outer circumference of each runner in each step, and the runners in each step are directly connected to a single main shaft of the water turbine, and the runners in each step are connected directly to a single main shaft of the water turbine, so that the runners in each step are connected to each other at the same rotational speed by changing only the direction of rotation. Or, in a single-speed reversible multi-stage pump-turbine designed for pump operation, the outer diameter of the runner blade in the low-pressure side stage equipped with fixed vanes is 0.86 to 0.96 times the outer diameter of the runner blade in the highest-pressure stage. A single-speed reversible multi-stage pump-turbine characterized in that the runner of the low-pressure side stage is configured to fall within the range.