CN110439722B - An anti-wear Francis turbine suitable for high water head, high rotational speed and high sand content - Google Patents

Abstract

The invention relates to an abrasion-resistant mixed-flow water turbine suitable for high water head, high rotating speed and high sand content, which comprises a volute, a fixed guide vane, a movable guide vane, a rotating wheel and a tail water pipe, wherein the molded lines of the movable guide vane are two symmetrical cubic curve groups, so that the flow velocity of a guide vane area and the resistance loss in a flow channel are smaller, the flow is smoother, and the abrasion of silt to the outlet area of the guide vane is effectively reduced; the newly designed long and short blade rotating wheel, the diameter of the rotating wheel, the wrap angle of the blades, the installation angle of the inlet of the blades and the change rule of the thickness of the blades from the inlet to the outlet can better match the structural strength of the flow field and the rotating wheel, and the abrasion of silt to the outlet edge of the rotating wheel is obviously reduced. The water turbine can greatly reduce the flow velocity of the guide vane area and the rotating wheel area, remarkably improve the abrasion resistance of the rotating wheel and the guide vane under the condition of high sand-containing water flow, reduce the vibration and pressure pulsation of a unit, remarkably prolong the overhaul and replacement period of the rotating wheel and the guide vane, and improve the operation stability and the safe operation life of the water turbine.

Description

An anti-wear Francis turbine suitable for high water head, high rotational speed and high sand content

technical field

The invention belongs to the technical field of fluid machinery and engineering equipment, and in particular relates to a Francis turbine, in particular to a Francis turbine that is suitable for high water head, high rotational speed and high sand content, low specific rotational speed and anti-sand abrasion resistance.

Background technique

The flow of many rivers in my country has a high sediment content, and the sand particle diameter is too large. Therefore, the impact of sediment wear on the long-term stable operation of the turbine is a key factor to be considered in the design process. Francis turbine units are mostly used in power stations built on silt-sand rivers, and the flow channel forms are rich and varied.

The main feature of the flow channel is that the runner adopts a lower speed. However, the actual power station survey found that the guide vane wear rate has far exceeded the runner, which has become a restrictive factor affecting the normal operation of the unit and controlling the overhaul period. This is because in a Francis turbine with a high head and a low specific speed, the turbine reaches its rated power at a small opening of the guide vane, which causes the absolute velocity of the flow around the guide vane to be greater than the relative rotational speed of the runner. Extend to guide vanes. At the same time, the runner matches the direction of the flow velocity at the outlet of the guide vane, the blade inlet is seriously bent, and the flow velocity at the inlet and outlet of the runner is relatively high. As a result, the wear speed of the runner and guide vane is greatly increased.

SUMMARY OF THE INVENTION

In order to overcome a series of defects existing in the prior art, the purpose of the present invention is to provide an anti-wear Francis turbine to solve the problems raised in the above background art.

An anti-wear Francis turbine suitable for high water head, high rotational speed and high sand content of the present invention comprises a volute (1), a fixed guide vane (2), a movable guide vane (3), a runner (4) and a Draft pipe (5), wherein,

The movable guide vane profile is a closed curve composed of two symmetrical cubic curves, and the equation of the cubic curve is:

y=0.000003x3-0.006x2-0.112x ^{+ 29.514}

The structure of the runner (4) is that a plurality of water turbine blades (7) are installed on the lower side of the upper crown (8) of the upper runner, and the lower ends of the turbine blades (7) are installed coaxially with the upper crown (8) of the runner. The lower ring (6) of the runner, the highest point where the upper crown (8) of the runner is in contact with the turbine blades (7) to the highest point corresponding to the lower ring (6) of the runner and the turbine blades (7) The distance h between them is 125-135mm;

The middle section of the long blade and the short blade of the water turbine blade (7) is a closed curve composed of two curves connected end to end.

Among them, the equations of the two curves of the long blade are:

y=0.0000001x ⁴ +0.00001x ³ -0.0081x ² +0.1904x+67.165

y=0.00000001x ⁴ +0.00002x ³ -0.0103x ² +0.4251x+62.951

The equations of the two curves for the short blade are:

y=0.000002x4-0.0012x3 ^{+ 0.2179x2-18.193x +} 624.89

y=0.0000006x4-0.002x3 ^{+ 0.0233x2-1.3429x +} 88.844

Adjust the length of the straight cone section of the draft tube (5) and the diameter of the inlet section, so that the height difference H from the center of the guide vane on the runner (4) to the bottom plate of the draft tube is 3200-3250mm, and the diameter of the inlet section Dd is 650-680mm.

The beneficial effects of the present invention are:

1. Using the long and short blade runner, the runner diameter, the blade wrap angle, the blade inlet placement angle, and the blade thickness variation law from the inlet to the outlet are newly designed, which not only better matches the flow field and the strength of the runner structure, but also significantly Reduce the wear and tear of sediment on the outlet side of the runner.

2. The flow velocity in the movable guide vane area and the resistance loss in the flow channel are smaller, and the flow is smoother, which can effectively reduce the wear and tear of the sediment on the guide vane outlet area.

3. Compared with other existing units, the anti-sand wear performance of the runner and guide vanes is greatly improved, and the vibration, pressure pulsation and dynamic stress of the runner blades are reduced, so that the probability of cracks in the runner blades is greatly reduced. The operating stability and safe operating life of the machine are improved.

Description of drawings

Fig. 1 is the structural representation of Francis turbine of the present invention;

Fig. 2 is the runner sectional view of Francis turbine of the present invention;

Fig. 3 is the arrangement diagram of the fixed guide vane and the movable guide vane of the Francis turbine of the present invention;

Fig. 4 is the shape schematic diagram of the movable guide vane of the Francis turbine of the present invention;

Fig. 5 is a schematic diagram of the middle section of the runner blade of the Francis turbine of the present invention;

The reference numbers in the figure are:

1- volute; 2- fixed guide vane; 3- movable guide vane; 4- turbine runner; 5- draft tube; 6- runner lower ring; 7- turbine blade; 8- runner upper crown.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be described in more detail below with reference to the accompanying drawings in the embodiments of the present invention. Throughout the drawings, the same or similar reference numbers refer to the same or similar elements or elements having the same or similar functions. The described embodiments are some, but not all, of the embodiments of the present invention. The embodiments and directional words described below with reference to the accompanying drawings are all exemplary, and are intended to be used to explain the present invention, but should not be construed as limiting the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

In a broad embodiment of the present invention, the present invention provides an anti-wear Francis turbine suitable for high water head, high rotational speed and high sand content. The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

As shown in FIG. 1 , the water turbine includes a volute 1 , a fixed guide vane 2 , a movable guide vane 3 , a water turbine runner 4 and a draft tube 5 .

As shown in FIG. 2 , the structure of the water turbine runner 4 is as follows: a plurality of water turbine blades 7 are installed on the lower side of the upper crown 8 of the upper runner, and the lower end of the water turbine blade 7 is installed under the runner that is coaxial with the upper crown 8 of the runner. Ring 6, the distance h between the highest point of the contact between the upper crown 8 of the runner and the turbine blades 7 to the highest point corresponding to the lower ring 6 of the runner and the turbine blades 7, that is, the upper crown 8 of the runner and the runner The height difference of the lower ring surface is 125-135mm.

As shown in Figures 3 and 4, the fixed guide vane 2 is located on the outer ring of the movable guide vane 3; in order to reduce the outlet speed of the guide vane and achieve the purpose of reducing wear, the shape of the movable guide vane 3 is designed as a symmetrical guide vane, and The tail of the guide vane is specially designed to reduce the thickness and local speed, and improve its anti-wear ability. The guide vane profile is a closed curve composed of two symmetrical cubic curves. The equation of the cubic curve is:

y=0.000003x3-0.0006x2-0.112x ^{+ 29.514}

As shown in Figure 2 and Figure 5, in order to reduce the relative velocity in the runner flow channel, improve the anti-wear performance of the runner, and comprehensively consider the reasonable matching with the guide vane outflow, the hydraulic performance of the turbine, the structural strength and other factors, this study adopts Long and short blade runner type. The middle section of the long and short blades of the turbine blade is a closed curve composed of two end-to-end curves. The equations of the two curves of the long blade are:

y=0.0000001x ⁴ +0.00001x ³ -0.0081x ² +0.1904x+67.165

y=0.00000001x ⁴ +0.00002x ³ -0.0103x ² +0.4251x+62.951

The equations of the two curves for the short blade are:

y=0.00002x4-0.0012x3 ^{+ 0.2179x2-18.193x +} 624.89

y=0.0000006x4-0.0002x3 ^{+ 0.0233x2-1.3429x +} 88.844

As shown in Figure 1, increase the length of the straight cone section of the draft tube 5 and the diameter of the inlet section, so that the height difference H between the center of the guide vane on the runner and the bottom plate of the draft tube is 3200-3250mm, and the diameter of the inlet section Dd It is 650-680mm, which can effectively recover the energy in the draft tube, reduce the hydraulic loss and improve the efficiency of the unit.

The invention has carried out numerical simulation and field test on the prototype Francis turbine, analyzed the relative velocity of the flow field in the runner and guide vane domain, analyzed the influence of the change of the flow channel shape on the energy performance, cavitation performance and stability, and analyzed the The flow loss of each part of the flow channel and the hydraulic performance of different operating conditions. Through the test data and actual effects, it can be found that compared with other existing units, the use of the unit of the present invention can greatly reduce the flow rate of the guide vane area and the runner area, and significantly improve the wear resistance of the runner and guide vane in the condition of high sand content water flow. performance. In addition, the vibration and pressure pulsation of the unit are reduced, the dynamic stress of the runner blades is reduced, the maintenance and replacement cycle of the runner and guide vanes in the sand-laden water flow can be significantly prolonged, and the operation stability and safe operation life of the turbine can be improved.

Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements to some of the technical features; and these Modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (1)

1. An abrasion-resistant mixed-flow water turbine adapting to high water head, high rotating speed and high sand content, which comprises a volute (1), a fixed guide vane (2), a movable guide vane (3), a rotating wheel (4) and a draft tube (5),

the movable guide vane molded line is a closed curve formed by two symmetrical cubic curves, and the equation of the cubic curve is as follows:

y＝0.000003x³-0.0006x²-0.112x+29.514

the runner (4) is structurally characterized in that a plurality of water turbine blades (7) are arranged on the lower side of a runner upper crown (8) at the upper part, a runner lower ring (6) coaxial with the runner upper crown (8) is arranged at the lower end of each water turbine blade (7), and the distance h from the highest point of the runner upper crown (8) in contact with the water turbine blades (7) to the highest point of the runner lower ring (6) corresponding to the water turbine blades (7) is 125-135 mm;

the middle sections of the long blades and the short blades of the water turbine blades (7) are closed curves formed by two sections of end-to-end connected curves;

the equations of the two curves of the long blade are respectively as follows:

y＝0.0000001x⁴+0.00001x³-0.0081x²+0.1904x+67.165

y＝0.00000001x⁴+0.00002x³-0.0103x²+0.4251x+62.951

the equations for the two curves for the short blade are:

y＝0.000002x⁴-0.0012x³+0.2179x²-18.193x+624.89

y＝0.0000006x⁴-0.0002x³+0.0233x²-1.3429x+88.844

and adjusting the length of the straight cone of the tail water pipe (5) and the diameter of the inlet section to ensure that the height difference H from the center of the guide vane on the rotating wheel (4) to the bottom plate of the tail water pipe is 3200-and-3250 mm, and the diameter Dd of the inlet section is 650-and-680 mm.

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