CN116776496A - Pumped storage transformation method for axial flow turbine runner - Google Patents

Abstract

A method of transforming the axial flow turbine runner into a pumped storage energy storage system. Using the operating parameters of the original power station axial flow turbine, the working parameters of the modified water pump turbine are formulated, including the characteristic head, head H ₁ , flow rate Q, rotation speed n and ratio. Rotation speed n _s , use the preliminary working parameters to calculate the main geometric parameters of the runner blade, including blade inlet diameter D ₁ , runner hub ratio, blade density s, runner blade airfoil chord length L, and grating pitch t , the blade inlet installation angle, the blade outlet installation angle, and the outer dimensions and blade shape of the axial flow pump turbine runner blades are obtained. Finally, the axial flow pump turbine runner is obtained to realize the optimization and transformation of the runner. The method of the invention can quickly achieve the purpose of transforming the runner part of a conventional hydropower station into pumped storage, greatly shorten the construction period of a conventional pumped storage power station, reduce construction costs, have good hydraulic performance, and have significant social and economic benefits. .

Description

A method for transforming axial flow turbine runner into pumped storage energy

Technical field

The invention relates to the field of hydraulic turbines, in particular to a method for transforming an axial flow turbine runner into pumped water storage.

Background technique

Affected by its own working characteristics, pumped storage power stations have high initial investment and construction costs, long construction cycles, time-consuming exploration planning and site selection, and will bring problems such as ecological protection and resettlement. At present, these problems have been restricting water pumping. Development of energy storage power stations. Therefore, how to carry out small and medium-sized pumped storage construction according to local conditions and explore and promote the integration and transformation of hydropower stations has always been a technical problem. The reasons are: on the one hand, conventional hydropower stations are limited by storage capacity and incoming water, and the annual utilization hours are generally low, about 3000 hours / Years, and there are currently a large number of small hydropower stations built, but there are fewer hydropower stations that meet the power generation requirements, and conventional small hydropower resources have been wasted to a certain extent; on the other hand, there are more cascade hydropower stations operating in some large river basins. Such as the Yangtze River Basin, the upper Yellow River Basin, the Yalong River Basin, the Lancang River Basin, etc. in my country. Therefore, in order to make full use of hydropower station resources to build pumped storage power stations, it has certain technical orientation and practical value to carry out research on the pumped storage transformation of conventional hydropower stations.

Axial flow turbines are the main models of conventional hydropower stations. They have the characteristics of large flow and low water head, with the water head ranging from 3 to 80m. However, the runner of a conventional turbine can often only meet the characteristics of one-way operation. Therefore, in the process of transforming a conventional turbine into a pump turbine, it is necessary to comprehensively consider the flow characteristics of the two working conditions. On the premise that the flow path of the original conventional hydropower station remains unchanged, Without changing the axial surface size of the turbine, especially without changing the axial surface size of the runner part, the runner of the conventional axial flow turbine can be transformed into pumped water storage, and the axial flow turbine generator unit can be transformed into pumped water storage. By optimizing and designing a unit that meets the two-way operating conditions, it is expected to transform a conventional hydropower station into a pumped storage power station that can combine power generation, peak load regulation and valley filling, and frequency regulation and phase adjustment. However, there has been no public report so far.

Contents of the invention

In view of the above situation, in order to overcome the shortcomings of the existing technology, the purpose of the present invention is to provide a method for transforming the axial flow turbine runner into pumped water storage, which can effectively solve the problem that the conventional hydropower station runner does not meet the two-way operation requirements and serve the purpose of pumping water. The construction of energy storage power stations provides equipment and technical support for the transformation of conventional hydropower stations into pumped storage.

In order to achieve the above object, the technical solution solved by the present invention is a method for transforming the axial flow turbine runner into pumped water storage. Using the operating parameters of the original power station axial flow turbine, the working parameters of the transformed water pump turbine are formulated, including characteristics. Based on the water head, head H ₁ , flow rate Q, rotation speed n and specific rotation speed n _s , use the preliminary working parameters to calculate the main geometric parameters of the runner blade, including the blade inlet diameter D ₁ and the runner hub ratio. The cascade density s, the runner blade airfoil chord length L, the grating pitch t, the blade inlet placement angle β ₁ , and the blade outlet placement angle β ₂ are used to obtain the overall dimensions and blade shape of the axial flow pump turbine runner blade. Finally, Obtain the runner of the axial flow pump turbine and realize the optimization and transformation of the runner.

The method of the present invention can quickly achieve the purpose of transforming the runner part of a conventional hydropower station into pumped water storage, and obtain axial flow pump turbine blades that meet the requirements of two-way operation and have better performance. Through this method, the pumped water storage energy transformation of the axial flow hydropower station can be completed. , which greatly shortens the construction period of conventional pumped storage power stations and reduces construction costs. The designed axial flow pump turbine runner has good hydraulic performance, meets user operation requirements, and has significant social and economic benefits.

Description of drawings

Figure 1 is an airfoil diagram of a runner blade according to the present invention.

Figure 2 is a diagram of the modified shape of the blade according to the embodiment of the present invention.

Figure 3 is a model diagram of the axial flow water pump turbine runner according to the embodiment of the present invention.

Figure 4 is a graph showing the change pattern of the initial runner performance of the axial flow pump turbine according to the embodiment of the present invention; among them, (a) the change pattern of the head H ₁ with the flow rate Q, (b) the change pattern of the efficiency η with the flow rate Q picture.

Detailed ways

The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings and specific situations.

The present invention takes the axial-flow turbine of a conventional hydropower station as the object of transformation, and aims at the transformation of its guide vane part and runner part into pumped water storage. While keeping the original flow path basically unchanged, the invention is modified according to the original conventional hydropower station. Working parameters, the guide vane type and runner type of the original conventional axial flow turbine are modified and designed. The modified axial flow pump turbine flow path relies on the conventional axial flow turbine flow path, including volute and fixed guide vanes. The five parts of the flow path, including the movable guide vane, runner and draft tube, will not undergo major changes. Only the runner and guide vane types will be modified and designed. The operating parameters of the original conventional power station axial flow turbine will be used to formulate the axial flow turbine. The design parameters for flow pump turbine modification include: head H ₁ , flow rate Q ₁ , speed n and specific speed n _s . According to the proposed parameters and based on the conventional pump turbine design principles, the optimal design parameters were selected and the modification design of the axial flow pump turbine runner was completed, and finally the axial flow pump turbine runner was obtained. The modified water pump turbine meets the requirements of pumped storage power stations in terms of main performances such as head, head, and flow rate. The one-way operating axial flow turbine is transformed into an axial flow pump turbine that meets the requirements of two-way operation, and the conventional hydropower station is transformed into a pumped storage power station that can combine power generation, peak regulation and valley filling, frequency regulation and phase adjustment.

A method for transforming an axial flow turbine runner into pumped water storage, including the following steps:

(1) Selection of the working speed of the axial flow pump turbine: According to the relationship between the pump turbine speed and the specific speed coefficient, refer to the specific speed statistical curve of the water pump operating conditions, back-calculate the pump turbine speed, take the value of the speed n as a multiple of 100, and get the power generation Machine synchronous speed, the calculation formula is:

In the formula: K _P is the specific speed coefficient; n _r is the rated speed; Q _P is the design flow rate;

(2) Renovation of the runner inlet diameter D ₁ of the water pump turbine: refer to the original runner flow channel size, and calculate the runner inlet diameter D ₁ according to the proposed axial flow pump turbine lift H ₁ , flow rate Q and rotation speed n, and the calculation formula for:

In the formula, wheel hub ratio Selected by specific speed; Q - flow rate, unit m ³ /s; n - speed, unit r/min; D ₁ - runner inlet diameter, unit m;

(3) Use the runner inlet diameter parameter D ₁ obtained in step (2) to calculate the runner hub ratio and the geometric parameters of the blade density s, to obtain the runner blade airfoil chord length L and pitch t. The calculation formula is:

In the formula: z is the number of blades; s is the cascade density;

(4) Based on the runner parameters obtained in the above steps, use the streamline method to modify the shape of the modified runner, and calculate the blade inlet and outlet angles β ₁ and β ₂ ; according to the design process of the streamline method, first establish different runner For the blade splitting surface, five cylindrical flow layers of different diameters are established according to the principle of equal spacing, and then the inlet and outlet velocity triangles of each flow surface are calculated to determine the blade inlet and outlet angles of different flow surfaces;

1) Import velocity triangle:

In the formula: D is the diameter of the cylindrical flow surface; η _v is the volumetric efficiency, which is taken as 0.98; the circumferential velocity component of v ₁ ; v _m1 is the inlet axial surface velocity;

2) Exit velocity triangle:

In the formula: u ₁ is the inlet circumferential speed, u ₂ outlet circumferential speed, u runner circumferential speed; H _t is the theoretical lift of the pump; v _m is the shaft surface speed; v _m2 is the outlet shaft surface speed; v _u2 is the absolute speed The circumferential component of

3) Speed triangle relationship:

In the formula: β ₁ is the blade inlet placement angle, unit °; β ₂ is the blade outlet placement angle, and the value of β retains one integer;

The above velocity triangle relationship determines the blade inlet and outlet placement angles β ₁ and β ₂ . Based on the parameters of the above runner components, calculate the blade inlet and outlet angles β ₁ and β ₂ for the five flow surfaces from the hub to the rim respectively;

(5) According to the calculation results of the blade inlet and outlet, the calculation formula of the placement angle β _L of the airfoil chord line and the blade height H ₂ is:

β _L =(β ₁ +β ₂ )/2 Formula (8)

H ₂ =L sinβ _L formula (9)

Draw the airfoil bone lines on each flow surface based on the calculation results of the airfoil parameters, and thicken the bone lines to form an airfoil. The airfoils on each flow surface are combined to complete the three-dimensional drawing of the blade;

(6) During the transformation process, the number of blades should be kept consistent with the number of original runner blades, so that the turbine has good flow capacity and cavitation performance; refer to the blade calculation parameters to realize the three-dimensional modeling of the runner blades, and use the blade array to Complete the model establishment of all blades, and then obtain the modified axial flow pump turbine runner model;

(7) Use computational fluid dynamics to conduct a full-flow numerical simulation of the modified axial flow pump turbine to verify the rationality of parameter selection during the modification design process, including the selection of the runner operating speed n and the design flow rate Q; according to the numerical simulation Based on the calculation results, the design parameters are continuously modified and optimized to optimize the design parameters of the axial flow pump turbine, and then the final runner blade shape is obtained to achieve the optimized transformation of the runner.

The specific implementation of the present invention can be given by the following examples.

Example 1

A conventional power station is based on a large reservoir in the Yangtze River Basin. The reservoir is mainly used for flood control and power generation, as well as irrigation, shipping and other tasks. The reservoir basin area reaches 2,500km ² , with an average annual water inflow of 2.5 billion m ³ . The power plant building type is behind the dam, with a single installed capacity of 23,500 kW. The water quality of the power station is clean and contains less sand. This conventional hydropower station is equipped with two hydro-turbine generator units and adopts a joint water supply method. The original turbine parameters are shown in Table 1. The maximum water head of the power station is about 30m. The volute type is a steel metal volute. Concrete is laid outside the volute. The volute wrap angle is 345° and the working speed is 200r/min.

Table 1 Original turbine parameter table

Keeping the flow channel parameters of the original power station unchanged, the models of each flow-passing component are established completely according to the flow channel parameters of the original power station. The water diversion chamber adopts a metal volute type. The base circle diameter of the volute is D ₁ =6.6m, the inlet diameter D ₂ =6.0m, and the outlet width B =1.42m. The number of guide vanes is 24, the height of the guide vanes is B ₁ =1.4m, and the angle between the guide vane chord line and the inlet circle is β=50°. The water outlet chamber is the elbow-type water outlet chamber of the original power station, and the size parameters do not need to be adjusted. The modified design of the runner part includes the following steps:

(1) Referring to the design flow of the original power station, the design flow rate of the pump turbine in the primary selection is 80m ³ /s; considering that the design head of the original turbine is 27m, the characteristic head of the primary pump turbine is 35m; when selecting the pump turbine speed, Priority needs to be given to the specific speed and specific speed coefficient of the water pump turbine. The specific speed coefficient is a comprehensive indicator that reflects the level of hydraulic machinery parameters and economy.

In the formula: K _P is the specific speed coefficient; n _r is the rated speed; Q _P is the design flow rate;

Based on the statistical experience of past power stations, for water pump operating conditions, it is recommended that the specific speed coefficient does not exceed 3700, and the maximum limit is below 4000. Referring to the domestic and foreign water pump operating condition specific speed statistical curves, the specific speed coefficient of the water pump operating condition is 3000. According to the specific speed coefficient of the water pump turbine, the back-calculated speed of the water pump turbine is 335r/min, and the working speed n of the water pump is 300r/min. (2) Refer to the original runner flow channel size, select the runner diameter of the modified water pump turbine, and calculate the runner inlet diameter D ₁ according to the proposed axial flow water pump turbine head H ₁ , flow rate Q and rotation speed n, the calculation formula for:

Putting the proposed design head and design flow rate into Equation (2), the runner inlet diameter D ₁ is 2.95. Taking into account the principle that the original flow channel size will not change during the transformation research process, the runner inlet diameter needs to be based on the original flow channel size. Make appropriate increases or decreases, here take the runner diameter D ₁ as 3.6m to meet normal operating requirements.

(3) Use the runner parameter D ₁ obtained in step (2) to calculate the runner hub ratio and cascade density s and other geometric parameters;

Bring in D ₁ =3.6m, corresponding to the wheel hub ratio Taking 0.4, when the number of blades z is 5, the cascade density S = 0.88. The preliminary design parameter selection of the modified water pump turbine impeller is shown in Table 2.

Table 2 Water pump turbine runner design parameters

(4) Based on the partial parameters of the runner obtained in the above steps, use the streamline method to design the shape of the modified runner, and calculate the blade inlet and outlet angles β ₁ and β ₂ . According to the design process of the streamline method, different runner blade splitting surfaces are first established, and five cylindrical flow layers of different diameters are established according to the principle of equal spacing. Then the inlet and outlet velocity triangles of each flow surface are calculated to determine the blade entry and exit of different flow surfaces. quarrel; quarrel;

1) Import velocity triangle:

In the formula: D is the diameter of the cylindrical flow surface; η _v is the volumetric efficiency, which is taken to be 0.98; the circumferential velocity component of v ₁ ;

2) Exit velocity triangle:

In the formula: u ₁ is the inlet circumferential speed, u ₂ outlet circumferential speed, u runner circumferential speed; H _t is the theoretical lift of the pump; v _m is the shaft surface speed; v _m2 is the outlet shaft surface speed; v _u2 is the absolute speed The circumferential component of

3) Speed triangle relationship:

In the formula: β ₁ is the blade inlet placement angle, unit °; β ₂ is the blade outlet placement angle, and the value of β retains one integer;

The blade inlet and outlet placement angles β ₁ and β ₂ can be determined from the above velocity triangle relationship. Based on the above runner component design parameters, calculate the blade inlet and outlet angles β ₁ and β ₂ on the five flow surfaces from the hub to the rim, and the blade streamlines There are no strict numerical requirements for the given principle of the setting angle change rule from the inlet to the outlet, but it is necessary to ensure a smooth transition from the blade inlet to the outlet. Calculate the blade inlet and outlet angles on the five flow surfaces from the hub to the rim as shown in Table 3. shown.

Table 3 Inlet and outlet angles of blades on each flow surface

(5) According to the calculation results of the blade inlet and outlet, the placement angle of the airfoil chord line can be calculated according to β _L = (β ₁ + β ₂ )/2, and the blade height H ₂ is calculated using the formula H ₂ = L sin β _L. According to the airfoil The parameter calculation results are used to draw the airfoil bone lines of each flow surface as shown in Figure 1. The bone lines are thickened to form an airfoil. The airfoils of each flow surface are combined to complete the three-dimensional drawing of the blade.

(6) During the modification and design process, the number of blades should be kept consistent with the number of blades of the original runner, so that the turbine has good flow capacity and cavitation performance under working conditions. The three-dimensional modeling of the runner blades is realized with reference to the blade calculation parameters, and the model establishment of all blades is completed through the blade array, and then the modified axial flow pump turbine runner model is obtained, as shown in Figure 2.

After the axial flow pump turbine runner is obtained according to the above method, it is combined with the flow channel model of each component of the original power station, including the volute, fixed guide vane, and draft pipe, to form the entire axial flow pump turbine, as shown in Figure 3.

After performing three-dimensional modeling, meshing and numerical calculation on the entire axial flow pump turbine, the hydraulic performance of the axial flow pump turbine completed using the modification design method of the present invention is obtained. Figure 4 shows the performance change pattern of the axial flow pump-turbine pump operating conditions when the initial design flow rate is 80m ³ /s. It can be seen from the figure that the corresponding water head and efficiency show a trend of first increasing and then decreasing as the flow rate increases. And when working at the flow operating point of 110m ³ /s, the unit's water pump operating efficiency reaches a maximum of 68.04%. Taking efficiency as the main influencing index of the runner design, taking the highest efficiency as the optimization design standard, selecting the flow condition of 110m ³ /s as the optimized design flow rate, and redesigning the runner according to the above runner modification design steps, Thereby improving the design accuracy of the runner and achieving the goal of improving the working efficiency of the water pump.

The modification method of the present invention is used to continuously modify and optimize the modification design parameters, thereby optimizing the design parameters of the axial flow pump turbine, thereby obtaining a suitable runner blade shape and realizing the optimized design of the runner. The reconstructed and designed axial flow pump turbine meets the requirements of two-way operation and has good hydraulic efficiency.

In summary, it can be seen that the design method of the present invention obtains an axial flow pump turbine runner, which meets the requirements of transformation design, has good hydraulic performance, and reduces the problems of long construction period and high cost of conventional pumped storage power stations. After calculation, the construction period can be shortened by 2-3 times and the cost reduced by 1/3. Effectively solve the problems of resettlement and ecological damage caused by the new pumped storage power station. It provides services for the utilization of clean energy, and the transformation design method has a wide practical scope. It provides technical support for the pumped storage transformation of conventional Francis and diagonal flow turbines, and has significant social and economic benefits.

Claims (2)

1. A pumped storage reforming method for an axial flow turbine runner is characterized in that the operating parameters of a pump turbine after reforming are planned by utilizing the operating parameters of an axial flow turbine of an original power station, and the operating parameters comprise a characteristic water head and a lift H ₁ Flow Q, rotation speed n and specific rotation speed n _s Calculating main geometric parameters of the runner blade including the inlet diameter D of the blade by using the preliminarily drawn working parameters ₁ Hub ratio of runnerBlade cascade density s, runnerBlade airfoil chord length L, pitch t, blade inlet setting angle beta ₁ Blade outlet setting angle beta ₂ And obtaining the overall dimension and the blade shape of the runner blade of the axial flow water pump turbine, and finally obtaining the runner of the axial flow water pump turbine, thereby realizing the optimization and transformation of the runner.

2. The pumped storage reforming method of an axial flow turbine runner of claim 1, comprising the steps of:

(1) Selecting the working rotation speed of the axial flow water pump turbine: according to the relation between the rotating speed of the water pump turbine and the coefficient of specific speed, referring to a working condition specific rotating speed statistical curve of the water pump, reversely calculating the rotating speed of the water pump turbine, wherein the rotating speed n is a multiple of 100, and taking the synchronous rotating speed of the generator, wherein the calculation formula is as follows:

wherein: k (K) _P Is a specific speed coefficient; n is n _r Is rated rotation speed; q (Q) _P To design flow;

(2) Diameter D of runner inlet of water pump turbine ₁ And (3) transformation: according to the flow channel size of the original runner and the proposed water lift H of the axial flow water pump ₁ Calculating the inlet diameter D of the rotating wheel by the flow Q and the rotating speed n ₁ The calculation formula is as follows:

in the hub ratioSelecting by the specific rotation speed; q-flow, unit m ³ S; n-rotation speed, r/min; d (D) ₁ -rotor inlet diameter, unit m;

(3) Using the rotor inlet diameter parameter D obtained in the step (2) ₁ Calculating the hub ratio of the rotating wheelAnd geometrical parameters of the cascade density s to obtain the wing-shaped chord length L and the grid distance t of the runner blade, wherein the calculation formula is as follows:

wherein: z is the number of blades; s is the density of the cascade;

(4) According to the parameters of the rotating wheel obtained by the steps, the modified rotating wheel is subjected to modeling modification by adopting a streamline method, and the inlet and outlet angles beta of the blades are calculated ₁ 、β ₂ The method comprises the steps of carrying out a first treatment on the surface of the According to the design process of the streamline method, firstly, different runner blade flow dividing surfaces are established, 5 cylindrical flow layers with different diameters are established according to the principle of equal spacing, then, inlet and outlet speed triangles of each flow surface are calculated, and blade inlet and outlet angles of different flow surfaces are determined;

1) Inlet speed triangle:

wherein: d is the diameter of the cylindrical flow surface; η (eta) _v Taking 0.98 for volume efficiency; v ₁ Is a circumferential velocity component of (a); v _m1 Is the inlet axial surface speed;

2) Exit velocity triangle:

u ₁ ＝u ₂ ＝u，v _m2 ＝v _m1 ＝v _m ，

wherein: u (u) ₁ For inlet peripheral speed u ₂ Outlet peripheral speed, u-wheel peripheral speed；H _t Is the theoretical lift of the pump; v _m Is the axial surface speed; v _m2 Is the exit face velocity; v _u2 Is the circumferential component of absolute velocity;

3) Velocity triangle relationship:

wherein: beta ₁ Setting angle for blade inlet, unit degree; beta ₂ Reserving a bit of integer for the value of the angle beta of the blade outlet;

the above-mentioned speed triangle relation can be used for defining blade inlet and outlet mounting angle beta ₁ And beta ₂ According to the parameters of the rotating wheel component, respectively calculating the inlet and outlet angles beta of the blades from the hub to the five flow surfaces of the rim ₁ 、β ₂ ；

(5) According to the calculated result of the inlet and outlet of the blade, the setting angle beta of the airfoil chord line _L Blade height H ₂ The calculation formula of (2) is as follows:

β _L ＝(β ₁ +β ₂ ) 2 (8)

H ₂ ＝L sinβ _L (9)

Drawing wing profile bone lines of each flow surface according to wing profile parameter calculation results, thickening the bone lines to form wing profiles, and combining the wing profiles of each flow surface to complete three-dimensional drawing of the blade;

(6) In the transformation process, the number of blades is kept consistent with that of the original runner, so that the working condition of the water turbine has good overcurrent capacity and cavitation performance; the three-dimensional modeling of the runner blades is realized by referring to the blade calculation parameters, and the model establishment of all the blades is completed through the blade array, so that a modified runner model of the axial flow pump water turbine is obtained;

(7) The improved axial flow pump water turbine is subjected to full flow channel numerical simulation by utilizing computational fluid dynamics, and the rationality of parameter selection in the improvement design process is verified, wherein the rationality comprises the selection of the rotating wheel working rotating speed n and the design flow Q; according to the numerical simulation calculation result, the design parameters are continuously modified and optimized to achieve optimization of the design parameters of the axial flow pump water turbine, so that the final shape of the runner blade is obtained, and optimization and transformation of the runner are achieved.