CN2766054Y - Wheel with L-type blades of mixed flow turbine - Google Patents

Abstract

The utility model discloses an L-shaped blade runner of a mixed-flow water turbine. The part involved is the water outlet edge of the blade, and the purpose of improving the hydraulic performance of the water turbine is achieved by changing the geometric shape and size of the water outlet edge of the blade. The utility model mainly includes: an upper crown 1, a lower ring 2 and several curved blades 3 connected between the upper crown 1 and the lower ring 2; The low-pressure side of the wheel, that is, the axial outflow side of the water flow, is the blade outlet edge 5; the connection point between the blade outlet edge 5 and the lower ring 2 is A, the connection point between the blade outlet edge 5 and the upper crown 1 is B, and the outlet edge 5 shape line The midpoint is M, and G is any point between A and M on the 5-shaped line of the water outlet edge. The rotation center of the runner is O, and the rotation direction is n. There is at least one inflection point between lines A and M.

Description

Francis turbine L-blade runner

Technical field:

The utility model relates to a runner of a water turbine, in particular to the improvement of each unit blade in the rotation.

technical background:

After long-term technological development, the Francis turbine has been basically finalized, but a slight improvement of the blade airfoil of the runner may have a greater impact on the efficiency of the turbine. Seeking a more reasonable airfoil structure is still the designer's constant pursuit of goals, and as the turbine With the increase of the specific speed and the increase of the amplitude of the water head, the qualitative problem of the stability of the turbine operation has become increasingly prominent. In the past 30 years, some large-scale units at home and abroad have experienced vibration problems of varying degrees in a considerable number of turbines. The stability of the turbine operation is A world problem. With the continuous increase of the unit capacity of the hydro-generator set, the size of the hydro-turbine increases accordingly, and the rigidity of the runner is relatively weakened. Chinese patent ZL97195388.0 proposes an improved impeller of the Francis-type hydro-turbine. Its cavitation and water flow characteristics It has been improved, but the indicators in the above aspects are still not ideal. The existing Francis turbine blades have the following two situations at the water outlet edge:

1. As shown on the left side of Figure 3, in the top view of the runner, the two points A, M and any point G between them are on the same straight line, that is, the water outlet edge is located in the same axial section.

2. As shown on the right of Figure 3, in the top view of the runner, for any point G between A and M, it is located below or on the line AM along the direction of rotation G.

In short, for the existing blades in the direction of looking down on the runner, the straight line AM is always in the blade area.

Invention content:

The purpose of the utility model is to disclose an L-shaped blade runner of a Francis water turbine. The part involved is the water outlet edge of the blade, and the purpose of improving the hydraulic performance of the water turbine is achieved by changing the geometric shape and size of the water outlet edge of the blade.

The utility model mainly includes: an upper crown 1, a lower ring 2 and several curved blades 3 connected between the upper crown 1 and the lower ring 2; The low-pressure side of the wheel, that is, the axial outflow side of the water flow, is the blade outlet edge 5; the connection point between the blade outlet edge 5 and the lower ring 2 is A, the connection point between the blade outlet edge 5 and the upper crown 1 is B, and the outlet edge 5 shape line The midpoint is M, and G is any point between A and M on the 5-shaped line of the water outlet. The rotation center of the runner is O, and the rotation direction is n. It is characterized in that: in the plan view of the runner, the blades are There is at least one inflection point between the shape lines A and M.

In the top view of the runner of the utility model, for the point between A and M, along the direction of rotation n, there is always a point G located above the straight line AM, that is, the straight line AM is not completely in the blade (3) area.

The included angle (α) between the endpoints A and B of the water outlet of the utility model and the center of rotation O is relatively small, not more than 20 degrees.

The included angle (θ) between the straight line AG extension line of the utility model and the tangent line of the lower ring here is not less than 90 degrees.

The length of the bone line of the blade at the lower ring of the utility model is greater than the length of the bone line of the blade at the upper crown, and the ratio thereof is greater than 1.1.

Description of drawings

Fig. 1 is the perspective view of the utility model embodiment;

Fig. 2 is another perspective view of the utility model embodiment;

Fig. 3 is the runner top view transition diagram of the existing blade plan view;

Fig. 4 is the angular transition diagram of the blade plan view of the embodiment of the utility model;

Fig. 5 is the top view of the blade of the embodiment of the utility model;

Figure 6 The stress diagram of the outlet edge at the lower ring of the conventional blade;

Fig. 7 is the stress diagram of the water edge at the lower ring of the blade of the embodiment of the utility model;

The runner top view circular transition figure of Fig. 8 existing blade plan view;

Fig. 9 is a circular transition diagram of the plane view of the blade of the embodiment of the utility model.

Detailed ways

After long-term development, the Francis turbine has been basically finalized. The runner structure mainly includes: an upper crown, a lower ring, and a number of curved blades connected between the upper crown and the lower ring, as shown in Figure 1. The high-pressure side of the runner, that is, the radial inflow side of the water flow is the water inlet edge of the blade, and the low-pressure side of the runner, that is, the axial outflow side of the water flow is the water outlet edge of the blade. As shown in Figure 3, the connection point between the outlet edge of the Francis turbine blade and the lower ring is A, the midpoint of the outlet edge shape line is M, and G is any point between A and M on the water outlet edge shape line. The remarkable feature of the blade is that: For the point between the outlet edge line A and M, the total existence point G is located above the straight line AM along the direction of rotation n, that is, the straight line AM is not completely in the blade area in the direction of the runner, as shown in the figure 4.

According to the utility model, the L-shaped blades on the water outlet edge at the lower ring are reasonably abducted, so that the Francis turbine can benefit from the following aspects.

1. Turbine efficiency

The airfoil near the lower ring of the runner has a great influence on the efficiency of the turbine. The partial outreach of the lower ring of the blade not only reduces the hydraulic friction loss caused by the overall outreach of the water outlet, but also increases the pressure surface of the blade near the lower ring. The pressure difference on the suction surface is conducive to the improvement of the efficiency of the runner. The model test of the water turbine also shows that: a reasonable L-shaped blade on the water outlet edge of the lower ring can optimally improve the water turbine by (2-5)‰.

2. Turbine stability

With the increase of the specific speed of the turbine and the increase of the amplitude of the water head, the problem of the stability of the operation of the turbine has become increasingly prominent. In the past 30 years, some large units at home and abroad, a considerable number of water turbines have experienced vibration problems to varying degrees one after another, and the operation stability of water turbines is a worldwide problem.

The practice shows that the pressure pulsation at partial load is the main source of the vibration of the turbine unit. The circulation at the outlet of the runner is directly related to the pressure pulsation of the draft tube, which is an important index to measure the stability of the turbine. The partial outreach of the water outlet edge of the lower ring of the blade can change the circulation distribution of the water outlet edge of the runner blade and reduce the outlet circulation of the runner, thereby reducing the pressure pulsation amplitude in the draft tube and improving the operation stability of the turbine.

3. Runner Strength

As the unit capacity of modern hydroelectric generating units continues to increase, the size of the hydroturbine increases accordingly, and the rigidity of the runner is relatively weakened. While improving the hydraulic performance of the turbine, the L-shaped blade can also increase the rigidity of the runner, reduce the stress of the blade, and improve the operation reliability of the turbine unit.

Comparing the stress numerical calculation results in Figure 6 and Figure 7, after the water edge at the lower ring of the blade is partially abducted, the stress value at the lower ring of the blade drops from 105MPa to 68.4MPa, and the maximum stress value also decreases. The L-shaped blade greatly improves the rigidity of the runner.

From the above analysis, it can be seen that the L-shaped blade runner can not only improve the hydraulic performance of the turbine, improve the efficiency and stability of the turbine operation, but also improve the rigidity of the runner, which has high application value in engineering.

Claims (5)

1. A Francis turbine L-shaped blade runner, mainly comprising: an upper crown (1), a lower ring (2) and several curved blades (3) connected between the upper crown (1) and the lower ring (2); The high-pressure side of the runner, that is, the radial inflow side of the water flow, is the water inlet edge (4) of the blade, and the low-pressure side of the runner, that is, the axial outflow side of the water flow, is the water outlet edge of the blade (5); the water outlet edge (5) of the blade and the lower ring The connecting point of (2) is A, and the connecting point of blade outlet edge (5) and upper crown (1) is B, and the middle point of the outlet edge (5) shape line is M,, G is the outlet edge (5) shape line At any point between A and M, the center of rotation of the runner is O, and the direction of rotation is n. It is characterized in that there is at least one inflection point between the edge lines A and M of the blades of the runner. 2. The L-shaped blade runner of Francis water turbine according to claim 1, characterized in that: for the point between A and M, there is always point G located above the straight line AM along the direction of rotation n, that is, the straight line AM is incomplete. In the blade (3) area. 3. The L-shaped blade runner of the Francis turbine according to claim 1, wherein the angle α between the end points A and B of the water outlet and the center of rotation O is relatively small, not greater than 20 degrees. 4. The L-shaped blade runner of the Francis turbine according to claim 1, wherein the angle θ between the extension line of the straight line AG and the tangent line of the lower ring is not less than 90 degrees. 5. The L-shaped blade runner of the Francis turbine according to claim 1, wherein the length of the bone line of the blade at the lower ring is greater than the length of the bone line of the blade at the upper crown, and the ratio is greater than 1.1.

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