CN103114953A - Mixed-flow type water turbine reversed S-shaped rotating wheel with long and short blades - Google Patents

Abstract

The reverse S-shaped runner of the Francis water turbine of the present invention comprises an upper crown, a lower ring and several long blades and short blades connected between the upper crown and the lower ring. The water inlet edge of the blade presents a reverse "S" shape, through the wrapping angle of the long blade and the short blade, the inlet and outlet angle of the blade, the length of the axial flow channel of the short blade, the size of the opening from the short blade to the back of the adjacent long blade, etc. Optimized to greatly reduce the draft tube pressure pulsation under partial load conditions, reduce the diameter of the runner, thereby improving the efficiency of the runner, improving the flow state of the blade inlet at small flow and large flow, and at the same time, it can also keep the head of the inlet side small , to obtain higher optimal efficiency; lengthen the blade to achieve a wider high-efficiency operating range; the shape of the upper crown line of the blade and the shape of the lower ring line of the special blade are slightly reversed "S", Reduce the outlet flow velocity, improve the flow state in the runner, and improve the stability of the unit operation.

Description

Francis turbine reverse S-type long and short blade runner

Technical field:

The invention relates to a reverse S-shaped runner with long and short blades of a Francis water turbine.

technical background:

In recent years, especially after the introduction of the Three Gorges technology, the hydraulic design level of Francis turbines in my country has made great progress. However, with the development of technology, domestic and foreign power stations have gradually increased their requirements on the efficiency and stability of Francis turbines. For small flow, large flow and optimal working conditions, the power station needs the runner energy performance to have a wider operating range, that is, to have a higher energy index. Higher requirements are placed on the cavitation and pressure pulsation of the blade. At the same time, due to the large fluctuation of water head in many power stations, the runners must operate under different water head sections, which determines that in many cases the unit must inevitably run under conditions that deviate from the working conditions, which will cause cavitation of the runners and draft tube pressure pulsations become severe.

Due to the large diameter of the runner of the turbine, the disk loss increases, which greatly reduces the efficiency of the turbine; at the same time, the high flow rate also leads to strong dynamic and static interference at the inlet of the runner under partial load conditions , a series of problems such as strong pressure pulsation and high-intensity cavitation appear at the draft tube inlet. In such a power station, if a conventional water turbine runner is used, not only the runner efficiency level is low, but also serious instability problems will be brought to the operation of the unit. Existing mixed-flow runner blades are generally conventional blades and negative-inclination blades. The top view of a conventional blade is shown in Figure 4, and its water inlet edge 4 is a straight line or a parabola with at most one inflection point. The top view of the blade with a negative inclination angle is shown in Figure 5, and its water inlet edge 4 is a straight line or a parabola, with at most only one inflection point.

SUMMARY OF THE INVENTION: The object of the present invention is to disclose a Francis turbine with reverse S-shaped long and short blades that operates with high efficiency and improves stability. The technical solution of the present invention is: a reverse S-type long and short blade runner of a Francis turbine, including an upper crown (1), a lower ring (3) and several ), and each blade has a water inlet edge (4) facing the upstream flow guide mechanism of the turbine and a water outlet edge (5) facing the downstream, which is characterized by: the blade (2) The water inlet edge (4) has two inflection points between point A and point D, that is, the water inlet edge (4) of the blade (2) has two inflection points P1 and P2, and the water inlet edge of the blade (2) (4) is a reverse "S" shape; the upper crown line (6) of the blade (2) is the intersection line between the blade and the upper crown, and there are two inflection points between point D and point C, that is, the blade (2 ) has two inflection points S1 and S2, and the upper crown line (6) presents a reverse "S" shape; the lower ring line (7) of the blade (2) is the blade and the lower ring There are two inflection points between point A and point B. The lower circular line (7) of the blade (2) has two inflection points X1 and X2, and the lower circular line (7) presents a reverse "S ” type, the definition of blade-related points and lines: point A is the intersection of the blade water inlet (4) and the lower ring (3), point B is the intersection of the blade water outlet (5) and the lower ring (3), point C Point D is the intersection point of the leaf outlet edge (5) and the upper crown (1), point D is the intersection point of the blade inlet edge (4) and the upper crown (1), line AD is the blade inlet edge (4), and line BC is The water edge (5) of the blade.

The wrapping angle θL of the long blades of the present invention is optimized and determined according to the hydraulic performance required by the runner, and the wrapping angle of the short blades is determined in the following manner: θS/θL=0.35~0.45. The inlet angle βL2 of the long blade is different from the inlet angle βS2 of the short blade. The difference between the two is Δβ2=βL2-βS2, and the size of Δβ2 is related to the ratio of θS/θL. The larger the ratio of θS/θL, the smaller the Δβ2. The length of the axial surface of the short blade is determined by the ratio of the middle streamline GH of the axial surface of the short blade to the middle streamline GK of the axial surface of the long blade: GH/GK=0.60~0.70. The opening a0 of the negative pressure surface from the short blade to the long blade is related to the two parameters of the short blade wrap angle θS and the middle streamline GH of the short blade axial surface. The value of a0 must be small enough to play a corresponding role. The smaller the θS, the shorter the GH length , the smaller the value of a0 is. The pitch θp between adjacent blades has the same size. The number of blades of the runner with long and short blades of the Francis turbine is: 13 long blades and 13 short blades, or 15 long blades and 15 short blades.

By changing the shape of the inlet side, a wider range of high-efficiency operation can be achieved while improving stability; through the optimized design of the long blades and short blades of the Francis turbine, the problem of draft tube pressure pulsation under partial load conditions can be alleviated, and high The water head and large-capacity turbine inlet cavitation problems can improve the operating range of the turbine; the design of long and short blades doubles the number of blades, minimizes the stress load of a single blade, and improves the overall strength performance of the runner, so that it can be applied to more The range of high water head, which is expanded from the originally applied 200m head to 300m head; is the radial length of the blade, the shape of the special upper crown line of the blade (the intersection line between the blade and the upper crown) and the special lower ring shape of the blade The shape of the line (blade and lower ring intersection line) improves the efficiency and stability of the runner.

The working principle of the invention is as follows: the water turbine is a device for converting the energy of water flow into mechanical energy. Impact turbines utilize the potential and kinetic energy of water flow. The water flow fills the flow channel of the entire water turbine. The entire flow channel is a pressurized closed system. The water flow is a pressurized flow. The water flow enters the water along the outer circumference of the runner, and the water flow pressure gradually decreases from the inlet paper outlet of the runner. When the water flow impacts the runner blades of the water turbine, the inertial force causes the force acting on the blades. In turn, the blades change the speed (direction or magnitude) and pressure of the water flow.

According to the present invention, the rational design of reverse S-shaped long and short runner blades at the water inlet will benefit the Francis turbine in the following aspects.

1. Turbine efficiency

(1) The water inlet side of the blade is in reverse "S" shape, the lower part of which is adapted to the incoming flow of small flow, and the upper part of which is adapted to the incoming flow of large flow, so as to improve the flow state of the blade inlet at the same time when small flow and large flow. Only in this way can the head of the water inlet side be kept small, which is conducive to improving the efficiency of the optimal working condition of the runner. The ratio of the arc length of the water inlet A, D and the water outlet B, C of the blade to the nominal diameter φ is increased, which is equivalent to lengthening the blade, increasing the work area, improving the energy conversion rate, and achieving a wider high-efficiency operating range, namely Realize that the power station has high-efficiency performance indicators in the operating conditions of small flow, large flow and optimal working conditions.

(2) The shape of the upper crown line of the blade (the intersection line between the blade and the upper crown) has a greater impact on the efficiency of a large-flow turbine, increasing the pressure difference between the pressure surface and the suction surface of the blade near the upper crown, which is beneficial to the efficiency of the runner improvement. At the same time, the outlet flow velocity is reduced to improve the flow state in the runner.

(3) The shape of the lower ring line of the blade (the intersection line between the blade and the lower ring) has a great influence on the small flow efficiency of the turbine, which increases the pressure difference between the pressure surface and the suction surface of the blade near the lower ring, which is beneficial to the efficiency of the runner improve. At the same time, the outlet flow velocity is reduced to improve the flow state in the runner.

(4) The design of the runner with long and short blades can reduce its diameter, thereby reducing the size of the whole machine, thereby reducing the manufacturing cost of the runner, reducing the excavation volume of the power station, and bringing a series of economic benefits; and the reduction in the diameter of the runner A smaller disc loss results in lower disc loss, which increases the efficiency of the runner.

(5) The model test of the turbine shows that the water inlet edge of the blade with a reasonable shape, the upper crown line of the blade (the intersection line between the blade and the upper crown) and the lower ring line of the blade (the intersection line between the blade and the lower ring) are reverse S-shaped Long and short blades can increase the optimal efficiency of the turbine by 5~10‰, and greatly improve the efficiency of small flow and large flow turbines.

2. Turbine stability

(1) The practice shows that there is a direct relationship between the outlet circulation of the runner and the pressure fluctuation of the draft tube, and it is an important index to measure the stability of the turbine. The shape of the upper crown line of the blade (the intersection line between the blade and the upper crown) and the shape of the special lower ring line of the blade (the intersection line between the blade and the lower ring) change, and the design of the long and short blades changes the shape of the water edge accordingly. The blade load is reduced, so as to control the circulation distribution at the outlet of the runner when it deviates from the optimal working condition, fundamentally avoid energy accumulation, reduce the pressure pulsation in the draft tube, and improve the stability of the unit operation. At the same time, due to the lengthening of the blades, the surface velocity of the blades is reduced, which helps to improve the stability of the unit.

(2) In the operating range of partial load, the secondary flow to the lower ring side of the runner decreases, and the swirl rate also decreases, where the swirl rate is defined as the ratio of angular momentum to axial momentum. The vortex rate is closely related to the pressure pulsation at the draft tube, and the decrease of the vortex rate will reduce the pressure pulsation of the draft tube.

(3) The reduction of the diameter of the runner and the angle of the blade reduces the change of the liquid flow angle at the blade inlet under the working condition of the turbine, thereby improving the cavitation characteristics of the runner inlet.

(4) The design of long and short blades doubles the number of blades, minimizes the stress load of a single blade, and improves the overall strength performance of the runner, so that it can be applied to a higher water head range, that is, from the original application of 200 meters of water head Expanded to 350 meters head.

Description of drawings:

Figure 1 Schematic diagram of axial surface structure of reverse S-shaped long and short blades of Francis turbine

Figure 2 Schematic diagram of plane structure of reverse S-shaped long and short blades of Francis turbine

Figure 3 Assembly drawing of long and short blade runners of Francis pump turbine

Figure 4 Top view of conventional runner blades of Francis turbine

Figure 5 Top view of the negative-inclination runner blades of the Francis turbine

Figure 6 Top view of the blades of the reverse S-shaped long and short blade runner of the Francis turbine

Figure 7 Stereoscopic view of the blades of the reverse S-shaped long and short blade runner of the Francis turbine

Detailed ways:

As shown in Figure 1 and Figure 2, a Francis turbine reverse S-shaped long and short blade runner, including an upper crown 1, a lower ring 3 and several long and short blades connected between the upper crown 1 and the lower ring 3 2. Each blade has a water inlet edge 4 facing the upstream flow guide mechanism of the turbine and a water outlet edge 5 facing downstream. The feature is: the water inlet edge 4 of the blade 2 is from point A to point D. There are two inflection points, that is, the water inlet edge 4 of the blade 2 has two inflection points P1 and P2, and the water inlet edge 4 of the blade 2 is a reverse "S" shape; the upper crown line 6 of the blade 2 is the blade and the upper crown. There are two inflection points between point D and point C, as shown in Figure 5, that is, the upper crown line 6 of the blade 2 has two inflection points S1 and S2, and the upper crown line 6 is reversed. "S" type; the lower ring line 7 of the blade 2 is the intersection line between the blade and the lower ring, with two inflection points between point A and point B, and the lower ring line 7 of the blade 2 has two X1 and X2 The inflection point, the lower ring line 7 presents a reverse "S" shape, the definition of blade related points and lines: point A is the intersection point of the blade water inlet edge 4 and the lower ring 3, and point B is the intersection point of the blade water outlet edge 5 and the lower ring 3 Intersection point, point C is the intersection point of the blade water outlet edge 5 and the upper crown 1, point D is the intersection point of the blade water inlet edge 4 and the upper crown 1, line AD is the water inlet edge 4 of the blade, and line BC is the water outlet edge 5 of the blade.

The range of the number of leaves: thirteen long leaves and thirteen short leaves; or fourteen long leaves and fourteen short leaves; or fifteen long leaves and fifteen short leaves.

The wrapping angle θL of the long blade is optimized and determined according to the hydraulic performance required by the runner, and the wrapping angle θS of the short blade is determined as follows: θS/θL=0.35~0.45, the inlet angle βL2 of the long blade is equal to the inlet angle βS2 of the short blade Not the same, the difference between the two is Δβ2=βL2-βS2, and the length of the short blade axial surface is determined by the ratio of the middle streamline GH of the short blade axial surface to the middle streamline GK of the long blade axial surface: GH/GK=0.60~0.7.

The technical parameters and component descriptions shown in Figure 1-Figure 7:

β1: Blade outlet angle;

βL2: long blade inlet angle;

βS2: short blade inlet angle;

θL: long blade wrap angle;

θS: short blade wrap angle;

θp: blade pitch;

a0: short blade to long blade negative pressure surface opening;

AD: Into the water

BC: long leaves out of the water

EF: short blades out of the water

GH: middle streamline of short blade axial surface

GK: the middle streamline of the axial surface of the long blade

1: crown

2: long and short leaves

3: Lower ring

4: Into the water

5: out of the water

6: long leaves

7: short blade

1. The reverse S-shaped design of the runner blade

As shown in Figure 3, the present invention comprises an upper crown 1, a lower ring 3 and several three-dimensional twisted blades 2 connected between the upper crown 1 and the lower ring 3, and each blade has a blade facing the upstream flow guiding mechanism of the water turbine. The water inlet edge 4 and the water outlet edge 5 facing downstream. In Figure 1, ABCD is the axial plane of the blade, which is the figure formed by the blade rotation projection onto a plane passing through the turbine rotation center Z, φ is the diameter of point A (also known as the nominal diameter), P represents the water inlet side, and O represents the water outlet side, Z represents the center of rotation of the turbine. Definition of blade-related points and lines: Point A is the intersection point of blade water inlet edge 4 and lower ring 3, point B is the intersection point of blade water outlet edge 5 and lower ring 3, and point C is the intersection point of blade water outlet edge 5 and upper crown 1 , point D is the intersection point of blade water inlet edge 4 and crown 1, line AD is blade water inlet edge 4, and line BC is blade water outlet edge 5.

There are two inflection points between the water inlet edge 4 of the blade 2 from point A to point D. In Figure 6, the two inflection points are located on both sides of the straight line AD, starting from point A, running along the water inlet 4 from point A, first passing through an inflection point on the right side of the straight line AD, and then passing through an inflection point on the left side of the straight line AD. Inflection point, and finally reach point D. In Fig. 7, it is shown that the water inlet edge 4 of the blade 2 has two inflection points P1 and P2, and it is in an obvious reverse "S" shape;

There are two inflection points between the upper crown shape line 6 of the blade 2 (blade and upper crown intersection line) from D point to C point. In Figure 6, the two inflection points are respectively located on both sides of the straight line DC, starting from D, running along the intersection line 6 between the back of the blade and the upper crown from point D, first passing through an inflection point on the right side of the straight line DC, and then passing through the left side of the straight line DC An inflection point on the side, and finally reaches point C. In Fig. 7, it is shown that the upper crown line 6 of the blade 2 has two inflection points S1 and S2, and is slightly reversed "S" shape;

There are two inflection points between the lower ring profile line 7 of the blade 2 (the intersection line between the blade and the lower ring) from point A to point B. In Figure 6, the two inflection points are located on both sides of the straight line AB, starting from point A, running along the intersection line 7 between the working surface or the back of the blade and the lower ring from point A, first passing through an inflection point on the right side of the straight line AB, and then passing through An inflection point on the left side of the straight line AB, and finally reaches point B. In Fig. 7, it is shown that the lower circular line 7 of the blade 2 has two inflection points X1 and X2, and is slightly reversed "S".

2. Long and short blade design.

In the hydraulic design of long and short blade runners of Francis turbines, since the long blades play a decisive role in the cavitation performance of the runner, the parameters of the long blades are optimized first. The cavitation performance of the runner can be satisfied by adjusting the wrap angle θL and blade outlet angle β1 of the long blade in Fig. 2, and the operating range of the runner can be satisfied by adjusting the blade inlet angle βL2 of the long blade. At this time, the wrap angle θS and blade inlet angle βS2 of the short blade are determined according to the wrap angle θL of the long blade and the inlet angle βL2 of the blade, so as to design the preliminary airfoil of the short blade. Then, find the opening a0 of the negative pressure surface from the short blade to the long blade, and evaluate the size of a0. If the value of a0 is too large, it can be adjusted by adjusting the length of the short blade axial surface middle streamline GH and the value of its wrap angle θS. Make a0 smaller. In the process of adjusting a0, attention should be paid to the influence of changes in the value of short blade wrap angle θS on inlet cavitation and operating range. In all design processes, CFD numerical simulation method is used to jointly calculate long and short blades. After the CFD numerical simulation, the model runner with long and short blades of the turbine can be processed according to the design data, and the model test can be carried out to further evaluate its performance, and at the same time, the final evaluation of the design results can be carried out.

Claims (3)

1. A Francis turbine reverse S-shaped long-short blade runner, including an upper crown (1), a lower ring (3) and several lengths connected between the upper crown (1) and the lower ring (3) The blades (2), each blade has a water inlet edge (4) facing the upstream flow guide mechanism of the turbine and a water outlet edge (5) facing the downstream, which is characterized in that: the water inlet edge of the blade (2) ( 4) There are two inflection points between point A and point D, that is, the water inlet edge (4) of the blade (2) has two inflection points P1 and P2, and the water inlet edge (4) of the blade (2) is reversed. "S" shape; the upper crown shape line (6) of the blade (2) is the intersection line between the blade and the upper crown, and there are two inflection points between point D and point C, that is, the upper crown shape of the blade (2) The line (6) has two inflection points S1 and S2, and the upper crown line (6) presents a reverse "S" shape; the lower ring line (7) of the blade (2) is the intersection line between the blade and the lower ring, from There are two inflection points between point A and point B. The lower ring profile line (7) of the blade (2) has two inflection points X1 and X2. The lower ring profile line (7) presents a reverse "S" shape, and the blades are related Definition of points and lines: Point A is the intersection of the blade water inlet (4) and the lower ring (3), point B is the intersection of the blade water outlet (5) and the lower ring (3), and point C is the blade outlet water ( 5) The point of intersection with the upper crown (1), point D is the intersection point between the water inlet edge (4) of the blade and the upper crown (1), the line AD is the water inlet edge (4) of the blade, and the line BC is the water outlet edge of the blade ( 5). 2. A Francis turbine reverse S-type long and short blade runner according to claim 1, characterized in that: the number range of the blades: thirteen long blades and thirteen short blades; or fourteen long blades and fourteen short blades; or fifteen long blades and fifteen short blades. 3. A Francis turbine reverse S-type long and short blade runner according to claim 1, characterized in that: the long blade wrap angle θL is optimized and determined according to the hydraulic performance required by the runner, and the short blade wrap angle θS is determined in the following way: θS/θL=0.35~0.45, the inlet angle βL2 of the long blade is different from the inlet angle βS2 of the short blade, the difference between the two is Δβ2=βL2-βS2, the length of the axial surface of the short blade is determined by the axial surface of the short blade The ratio of the middle streamline GH to the middle streamline GK on the axial surface of the long blade is determined: GH/GK=0.60~0.7.

Images