阅读说明：本技术 一种水轮机座环尾水管减沙抗磨的方法 (Method for reducing sand and resisting wear of water turbine seat ring draft tube ) 是由 张续钟 任尚洁 朱卫娜 于 2021-09-15 设计创作，主要内容包括：本发明公开了一种水轮机座环尾水管减沙抗磨的方法,所述水轮机为立式混流式水轮机,包括若干活动导叶、支承活动导叶的座环,所述座环包括和活动导叶下端转动连接的轴套,在轴套和活动导叶下端之间具有配合间隙,包括如下步骤：a.用水泵将轴套内含有泥沙的水流抽出并形成压力水流；b.将压力水流从座环上表面靠近活动导叶入水边处的射流口向外喷出,从而在座环上表面形成若干微射流；c.微射流冲击从配合间隙射出的磨蚀水流,并形成低速的混合水流,混合水流沿座环上表面流动,并从尾水管流向下游。本发明可显著地减少甚至消除含有泥沙的水流对座环表面的不断冲刷形成的腐蚀沟槽,从而提高水轮机的发电效率,延长使用寿命。(The invention discloses a method for reducing sand and resisting wear of a water turbine seat ring draft tube, wherein the water turbine is a vertical mixed-flow water turbine and comprises a plurality of movable guide vanes and a seat ring for supporting the movable guide vanes, the seat ring comprises a shaft sleeve which is rotatably connected with the lower ends of the movable guide vanes, and a fit clearance is formed between the shaft sleeve and the lower ends of the movable guide vanes, and the method comprises the following steps: a. pumping water flow containing silt in the shaft sleeve by using a water pump to form pressure water flow; b. the pressure water flow is sprayed out from a jet opening on the upper surface of the seat ring close to the water inlet edge of the movable guide vane, so that a plurality of micro-jets are formed on the upper surface of the seat ring; c. the micro-jets impinge the abrasive water stream emitted from the mating gap and form a low velocity mixed water stream that flows along the upper surface of the seat ring and downstream from the draft tube. The invention can obviously reduce or even eliminate the corrosion groove formed by the continuous scouring of the water flow containing silt on the surface of the seat ring, thereby improving the power generation efficiency of the water turbine and prolonging the service life.)

1. A method for reducing sand and resisting wear of a turbine seat ring draft tube is characterized by comprising the following steps:

pumping water flow containing silt in the shaft sleeve by using a water pump to form pressure water flow;

the pressure water flow is sprayed out from a jet opening on the upper surface of the seat ring close to the water inlet edge of the movable guide vane, so that a plurality of micro-jets are formed on the upper surface of the seat ring;

the micro-jets impinge the abrasive water stream emitted from the mating gap and form a low velocity mixed water stream that flows along the upper surface of the seat ring and downstream from the draft tube.

2. The method for reducing sand and resisting wear of the draft tube of the seat ring of the water turbine as claimed in claim 1, wherein said jet ports are oriented at an angle α with respect to the upper surface of the seat ring, and wherein α is 70 ° or more and 110 ° or less.

3. The method for reducing sand and resisting wear of the draft tube of the seat ring of the water turbine as claimed in claim 1, wherein at least one jet port is formed in the upper surface of the seat ring corresponding to the water inlet edge of each movable guide vane.

4. The method for reducing sand and resisting wear of the water turbine seat ring draft tube according to claim 2, wherein the number of the jet orifices corresponding to the water inlet edge of each movable guide vane is 2, and an included angle smaller than 20 degrees is formed between the two jet orifices.

5. The method as claimed in claim 4, wherein the water turbine has a casing with water outlet holes at its lower part, a ring pipe connected to the water outlet holes at its lower part, a plurality of jet pipes extending upward and arranged on the casing, the jet pipes having upper openings at their upper ends to form the jet ports, and a booster pump connected to the ring pipe via a flow dividing pipe and to the lower ends of the jet pipes.

6. The method of claim 1, wherein a water collector is disposed in the draft tube, the center of the water collector is connected to the lower end of the main shaft, a circular isolation rib and a plurality of radial flow guide ribs are disposed on the bottom surface of the water collector, the outer ends of the flow guide ribs are connected to the isolation rib, the isolation rib separates a central water purification area and a peripheral muddy water area in the water collector, the height of the isolation rib is lower than that of the flow guide ribs, the height of the bottom surface of the water collector gradually increases from the center to the outside until the isolation rib is flush with the muddy water area, and in step a, the water pump simultaneously pumps out water flows in the shaft sleeve and the clean water area of the water collector to form a pressure water flow.

7. The method of claim 1, wherein a slow flow cover is covered at the upper opening of the water pan, a plurality of drainage tubes extending radially to the edge are disposed on the lower side of the slow flow cover, the drainage tubes are evenly distributed in the circumferential direction, a plurality of sets of drainage holes are disposed on the upper side of the slow flow cover, each set of drainage holes penetrates through the corresponding drainage tube, and when water flows onto the slow flow cover, the water flows into the corresponding drainage tube through the drainage holes and flows along the drainage tube to the muddy water region at the edge of the water pan.

Technical Field

The invention relates to the technical field of hydraulic generators, in particular to a method for reducing sand and resisting wear of a water turbine seat ring draft tube.

Background

With the enhancement of energy-saving and environment-friendly consciousness of people, clean and efficient power generation equipment is being developed vigorously, and the mixed-flow water turbine plays an important role in the clean energy industry of China. It is known that a francis turbine generally includes a vertical main shaft, a francis runner provided with blades at a lower end of the main shaft, and a metal volute provided around the francis runner, an inner side of the metal volute is provided with a water outlet, and a plurality of vertically arranged fixed guide vanes and movable guide vanes are further provided at a periphery of the francis runner, wherein an angle of the fixed guide vanes is fixed and is not adjustable, an angle of the movable guide vanes is adjustable, the fixed guide vanes are provided at the periphery, the movable guide vanes are located at an inner side of the fixed guide vanes and are rotatably connected to a seat ring, and the fixed guide vanes and the movable guide vanes are equidistantly distributed in a circumferential direction of the seat ring. The water flow of the reservoir, which is introduced by the metal volute through the water conduit, impacts the fixed guide vane through the water outlet, the water flow impacts the mixed-flow rotating wheel after being guided by the fixed guide vane and the movable guide vane, the mixed-flow rotating wheel rotates and then drives the main shaft to rotate, the main shaft can drive the generator to work to generate electricity, and the 'tail water' with weakened energy after impacting the mixed-flow rotating wheel is discharged downstream through a tail water pipe at the lower part of the mixed-flow rotating wheel.

In order to facilitate the flexible rotation of the movable guide vane, the pivot of the movable guide vane is rotatably arranged on the seat ring, and because the movable guide vane has large external dimension and heavy weight, a large fit clearance exists between the pivot of the movable guide vane and the seat ring, and correspondingly, high-pressure water flow flows outwards through the fit clearance to form abrasive water flow to wash the upper surface of the seat ring. Since the water flow of the reservoir contains a certain amount of silt, when the abrasive water flow containing silt flows out through the fitting clearance to flush the surface of the seat ring, the abrasive water flow containing silt forms an abrasive groove along the moving track of the movable guide vane on the surface of the seat ring.

It is known that, when the water turbine is in operation, the water inlet side of the movable guide vane facing the water flow is impacted by the water flow to form a tendency to move towards the water outlet side, so that the fit clearance close to the water inlet side is larger than the fit clearance close to the water outlet side, and the change of the fit clearance is not a simple linear change. Particularly, when the water turbine is in operation, the movable guide vane can continuously rotate to change the angle so as to adjust the water flow impacting on the mixed flow type rotating wheel and then adjust the power of the generator. Therefore, the flow pattern of the water flow flowing out of the matching gap, especially the water flow flowing out of the matching gap on the water inlet side, is extremely unstable, and even serious flow separation is generated. The flow shedding of the movable guide vane means that when the water flow attack angle reaches the vicinity of a critical value, water flow leaves the surface of the seat ring to generate boundary layer separation, so that a large number of regional vortexes are generated, and the phenomenon similar to cavitation is generated.

When the abrasion groove reaches a certain depth, the operation safety of the whole unit is affected, and the unit needs to be stopped for replacement or overhauled and maintained, so that the normal operation and power generation of the water turbine are affected, and the power generation efficiency is reduced.

Disclosure of Invention

The invention aims to provide a method for reducing sand and resisting wear of a water turbine seat ring draft tube, which can remarkably reduce or even eliminate corrosion grooves formed by continuous scouring of water flow containing sand on the surface of a seat ring, thereby improving the power generation efficiency of the water turbine and prolonging the service life.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method for reducing sand and resisting wear of a turbine seat ring draft tube, wherein the turbine is a vertical mixed-flow turbine and comprises a plurality of movable guide vanes and a seat ring for supporting the movable guide vanes, the seat ring comprises a shaft sleeve rotatably connected with the lower ends of the movable guide vanes, and a fit clearance is formed between the shaft sleeve and the lower ends of the movable guide vanes, and the method comprises the following steps:

a. pumping water flow containing silt in the shaft sleeve by using a water pump to form pressure water flow;

b. the pressure water flow is sprayed out from a jet opening on the upper surface of the seat ring close to the water inlet edge of the movable guide vane, so that a plurality of micro-jets are formed on the upper surface of the seat ring;

c. the micro-jets impinge the abrasive water stream emitted from the mating gap and form a low velocity mixed water stream that flows along the upper surface of the seat ring and downstream from the draft tube.

The invention uses a water pump to pump the water flow containing silt out of the shaft sleeve to form a pressure water flow with a certain pressure, and guides the pressure water flow to the jet orifice on the upper surface of the seat ring near the water inlet edge of the movable guide vane to be sprayed out, at the moment, the micro jet on the upper surface of the seat ring near each movable guide vane forms a micro jet upwards approximately, the micro jet impacts the abrasive water flow sprayed out from the matching gap, and the abrasive water flow flows approximately in the horizontal direction, so that the abrasive water flow and the micro jet form a sufficient 'mixing' to form a mixed water flow flowing at a low speed in the horizontal direction, the mixed water flow can effectively eliminate cavitation bubbles and the like in the original abrasive water flow, and effectively reduce the flow speed of the abrasive water flow. That is, the mixed water flow only slowly flows over the upper surface of the seat ring, so that the erosion effect of the sand-containing corrosive water flow on the surface of the seat ring can be basically eliminated, at least greatly slowed down, and the service life of the seat ring can be effectively prolonged.

In particular, the micro-jet flow comes from the water flow in the shaft sleeve, namely, additional water resources are not consumed, and the cost is reduced.

Preferably, the jet orifice is oriented at an included angle alpha with the upper surface of the seat ring, and alpha is greater than or equal to 70 degrees and less than or equal to 110 degrees.

The invention controls the included angle alpha between the orientation of the jet orifice and the upper surface of the seat ring in the following range: alpha is more than or equal to 70 degrees and less than or equal to 110 degrees, and the mixing area of the micro-jet and the corrosive water flow can be fully increased, so that the micro-jet can play a role in mixing the corrosive water flow to the maximum extent.

When α is less than 70 ° or α is greater than 110 °, on the one hand, the processing difficulty of the jet orifice is increased, and on the other hand, the velocity component of the micro jet in the horizontal direction is increased, which is not favorable for reducing the horizontal flow velocity of the mixed water flow.

Preferably, at least one jet opening is arranged on the upper surface of the seat ring corresponding to the water inlet edge of each movable guide vane so as to ensure that the corrosive water flow at the water inlet edge of each movable guide vane can be effectively mixed to form mixed water flow.

It can be understood that two or more jet orifices can be arranged at the water inlet edge of each movable guide vane so as to enlarge the mixing area of the micro jet and the corrosive water flow and enable the corrosive water flow to fully form mixed water flow.

Preferably, the number of the jet orifices corresponding to the water inlet edge of each movable guide vane is 2, and an included angle smaller than 20 degrees is formed between the orientations of the two jet orifices.

When the number of the jet orifices on the water inlet edge of each movable guide vane is 2, because the orientation of each jet orifice is the same, microjets formed by the 2 jet orifices can form a symmetrical relation, or extend upwards and intersect to form an included angle of 20 degrees, or extend downwards and intersect to form an included angle of 20 degrees, and on the basis of ensuring that the 2 microjets and the corrosive water flow are fully mixed, the horizontal flow velocity component of the microjets is reduced to the maximum extent, and then the flow velocity of the mixed water flow is reduced.

It can be understood that when the two jet ports are oppositely arranged, the flow velocity components of the formed micro-jets in the horizontal direction can be mutually counteracted, so that the horizontal flow velocity of the mixed water flow can be reduced to the maximum extent.

Preferably, the lower part of the shaft sleeve is provided with water outlet holes, the lower side of the seat ring is provided with a ring pipe communicated with the water outlet holes, the seat ring is provided with a plurality of jet pipes extending upwards, the upper ends of the jet pipes are provided with openings to form the jet ports, the ring pipe is communicated with the lower ends of the jet pipes through flow dividing pipes, and the flow dividing pipes are provided with booster pumps.

Because the lower part of the shaft sleeve is provided with the water outlet hole communicated with the ring pipe, when the booster water pump operates, water flow mixed with silt at the lower part of the shaft sleeve can be extracted through the ring pipe, and the water flow is sprayed out through the jet orifice at the upper end of the jet pipe.

It should be noted that, we can set the water outlet at the position near the lower end face of the shaft sleeve, so as to be beneficial to the sediment in the water flow depositing in the shaft sleeve, and reduce the sediment content in the water flow pumped out from the water outlet as much as possible. At this time, the lower end face of the shaft sleeve can be arranged to be conical, and a sand discharge port and a corresponding sealing cover are arranged at the lowest position of the lower end face. When we open the cover, we can discharge the deposited silt.

Preferably, a water receiving tray is arranged in the tail water pipe, the center of the water receiving tray is connected with the lower end of the main shaft, a circular isolation convex rib and a plurality of radial flow guide ribs are arranged on the bottom surface of the water receiving tray, the outer ends of the flow guide ribs are connected with the isolation convex ribs, the isolation convex ribs separate a central water purification area and a peripheral muddy water area in the water receiving tray, the height of the isolation convex ribs is lower than that of the flow guide ribs, the height of the bottom surface of the water receiving tray gradually rises from the center to the outside until the isolation convex ribs are flush connected with the water receiving tray, and in the step a, the water pump simultaneously extracts water flow in the shaft sleeve and the water purification area of the water receiving tray and forms pressure water flow.

The invention is characterized in that a water receiving tray connected with the lower end of a main shaft is arranged in a draft tube, a round isolation convex rib and a plurality of radial flow guide ribs are arranged in the water receiving tray, the isolation convex rib separates a peripheral muddy water area in the water receiving tray, and the flow guide ribs separate a plurality of fan-shaped water purification areas in an inner area surrounded by the isolation convex rib. Therefore, when the water turbine runs, the spindle can drive the water receiving disc to rotate at a high speed, water flow discharged to the downstream in the tail water pipe can be partially stored in the water receiving disc, the water receiving disc rotating at a high speed enables water stored inside to form a great centrifugal force, at the moment, sediment mixed in water can move radially from the water purification area to the muddy water area preferentially and enters the muddy water area, and accordingly, the sediment amount contained in water in the water purification area in the isolation convex ribs is greatly reduced. Therefore, the water pump can extract water flow in the water purifying area of the water receiving disc and eject the water flow outwards through the jet opening to form micro jet flow, so that the content of silt in the micro jet flow is effectively reduced.

Particularly, the height of the bottom surface of the water pan gradually rises from the center to the outside until the bottom surface is flush connected with the isolation convex rib. That is to say, the bottom surface of the water receiving tray is a conical surface with a low middle part and high periphery, and the muddy water area and the pure water area are blocked by the raised isolation convex ribs. Therefore, silt in the water purification area in the isolation convex rib can gradually move outwards and radially under the action of centrifugal force until the silt crosses the isolation convex rib and enters the muddy water area, and the sediment can be furthest reduced to be deposited due to obstruction when the silt moves radially, so that the silt can be ensured not to be deposited in the water purification area but only to be deposited in the muddy water area, and the silt in the muddy water area can be prevented from flowing back to the water purification area when the water is pumped outwards through the water pump in the water purification area.

In addition, the water diversion ribs separate a plurality of fan-shaped water purification areas in the water receiving tray, so that the silt can move outwards in the radial direction under the action of centrifugal force.

As preferred, the upper portion opening part lid of water collector is equipped with the slow flow lid, and the slow flow lid downside is equipped with a plurality of radial drainage tubes that extend to the edge, and the drainage tube is evenly distributed in circumference, and the slow flow covers the upside and is equipped with a plurality of groups drainage hole, and every group drainage hole link up the drainage tube that corresponds, when rivers fall to slow flow and cover, can get into in the drainage tube that corresponds through the drainage hole to in the muddy water region of water collector edge along the drainage tube.

The opening at the upper part of the water pan is provided with the slow flow cover, so that the water flow which is discharged from the tail water pipe can be prevented from directly entering the water pan to stir silt. Because the lower side of the slow flow cover is provided with a plurality of drainage tubes which radially extend to the edge, and the upper side of the slow flow cover is provided with a plurality of groups of drainage holes which are communicated with the corresponding drainage tubes. Therefore, when the water flow in the tail water pipe falls to the slow flow cover on the water receiving tray, the water flow can enter the drainage pipe through the drainage holes and then enter the muddy water area along the drainage pipe. It can be understood that we can reduce the diameter of the draft tube properly, thus slowing down the flow rate and impact force of the water flow and avoiding the draft tube 'turbidness' of the water flow in the muddy water area.

In particular, in the scheme, the water flow is supplemented to the muddy water area, when the water level of the muddy water area rises and is higher than the isolation convex rib, the water flow reversely flows to the water purification area, and the sediment mixed in the water is deposited in the muddy water area under the action of centrifugal force. That is to say, the radial convection of the upper layer and the lower layer is formed in the water receiving tray, the clear water of the upper layer flows back to the water purifying area, and the silt of the lower layer flows to the muddy water area.

Therefore, the invention has the following beneficial effects: the erosion groove formed by continuous scouring of the water flow containing silt on the surface of the seat ring can be obviously reduced or even eliminated, so that the power generation efficiency of the water turbine is improved, and the service life is prolonged.

Drawings

Fig. 1 is a schematic structural view of a vertical mixed-flow water turbine according to the present invention.

Fig. 2 is an enlarged view at a in fig. 1.

FIG. 3 is a schematic view of one configuration of a seat ring.

Fig. 4 is a schematic view of a connection structure of the water pan.

Fig. 5 is a schematic view of a connection structure of the water pan and the slow flow cover.

In the figure: 1. the device comprises a movable guide vane 11, a pivot 2, a seat ring 21, a shaft sleeve 221, a water outlet 22, a jet pipe 221, a jet port 3, an annular pipe 4, a water pump 5, a draft tube 6, a water pan 61, an isolation convex rib 62, a flow guide rib 63, a water purification area 64, a muddy water area 7, a main shaft 8, a slow flow cover 81, a drainage tube 82 and a drainage hole.

Detailed Description

The invention is further described with reference to the following detailed description and accompanying drawings.

A method for reducing sand and resisting wear of a turbine seat ring draft tube is a vertical francis turbine, as shown in figures 1 and 2, the vertical francis turbine comprises a plurality of movable guide vanes 1 with pivots and a seat ring 2 supporting the movable guide vane pivots 11, the seat ring comprises a shaft sleeve 21 rotatably connected with the lower ends of the movable guide vane pivots, and a fit clearance is formed between the shaft sleeve and the movable guide vane pivots, and the method specifically comprises the following steps:

a. pumping water flow containing silt in the shaft sleeve by using a water pump to form pressure water flow;

b. the pressure water flow is sprayed out from a jet opening on the upper surface of the seat ring close to the water inlet edge of the movable guide vane, so that a plurality of micro-jets are formed on the upper surface of the seat ring;

c. the micro-jets impinge the abrasive water stream emitted from the mating gap and form a low velocity mixed water stream that flows along the upper surface of the seat ring and downstream from the draft tube.

It is known that when the turbine is operating, water flow under pressure enters the inside of the sleeve through the fitting clearance and is mixed with silt. The invention uses the water pump 4 to pump the water flow with silt in the shaft sleeve outwards to form a pressure water flow with a certain pressure, and the pressure water flow is guided to the jet orifice 221 on the upper surface of the seat ring near the water inlet edge of the movable guide vane to be sprayed outwards, at the moment, micro-jet flows upwards are respectively formed on the upper surface of the seat ring near each movable guide vane, the micro-jet impacts the abrasive water flow ejected from the matching gap, and the abrasive water flow flows in the horizontal direction approximately, so that the abrasive water flow and the micro-jet form sufficient 'mixing' to form mixed water flow flowing at low speed in the horizontal direction, the mixed water flow can effectively eliminate cavitation bubbles and the like in the original abrasive water flow, the phenomenon of flow shedding is avoided, and the flow speed of the abrasive water flow is effectively reduced. That is, the mixed water flow only slowly flows over the upper surface of the seat ring, so that the erosion effect of the sand-containing corrosive water flow on the surface of the seat ring can be basically eliminated, at least greatly slowed down, and the service life of the seat ring can be effectively prolonged.

It should be noted that the vertical francis turbine belongs to the prior art, and the basic structure and the working principle thereof are not described in detail in this embodiment. In addition, the term "micro-jet" refers to a relatively small jet.

Preferably, we can control the angle α between the orientation of the jet orifice and the upper surface of the seat ring to be in the range: alpha is more than or equal to 70 degrees and less than or equal to 110 degrees so as to fully increase the mixing area of the micro jet and the corrosive water flow and ensure that the micro jet can play a role of mixing the corrosive water flow to the maximum extent.

Furthermore, at least one jet opening can be arranged on the upper surface of the seat ring corresponding to the water inlet edge of each movable guide vane, so that the corrosive water flow at the water inlet edge of each movable guide vane can be effectively mixed to form mixed water flow. Certainly, the number of the jet orifices corresponding to the water inlet edge of each movable guide vane is 2, and an included angle smaller than 20 degrees is formed between the orientations of the two jet orifices so as to enlarge the mixing area of the micro jet flow and the corrosive water flow and enable the corrosive water flow to fully form mixed water flow. Particularly, because the orientation of each jet orifice is the same, the microjets formed by 2 jet orifices can form a symmetrical relation, or extend upwards and intersect at an included angle of 20 degrees, or extend downwards and intersect at an included angle of 20 degrees, and on the basis of ensuring that the 2 microjets are fully blended with the corrosive water flow, the horizontal flow velocity component of the microjets is reduced to the maximum extent, and then the flow velocity of the mixed water flow is reduced.

It should be noted that, a corrugated pipe may be disposed in the middle of the jet pipe to facilitate bending and installation of the jet pipe.

As a preferable scheme, as shown in fig. 3, water outlet holes 211 are arranged at the lower part of the shaft sleeve, a ring pipe 3 communicated with the water outlet holes is arranged at the lower side of the seat ring, a plurality of jet pipes 22 extending upwards are arranged on the seat ring, the upper ends of the jet pipes are opened to form the jet ports, the ring pipe is communicated with the lower ends of the jet pipes through a shunt pipe, and a booster water pump is arranged on the shunt pipe. Of course, the booster pump is the above-mentioned pump.

When the booster water pump operates, the water flow mixed with silt at the lower part of the shaft sleeve can be extracted through the ring pipe and is sprayed out through the jet orifice at the upper end of the jet pipe.

Certainly, we can set the apopore at the lateral wall of the axle sleeve near the lower end face, that is to say, the apopore has certain distance with the axle sleeve lower end face to be favorable to the sediment in the rivers to deposit in the axle sleeve, reduce the content of sediment in the rivers that follow the apopore and take out as far as possible. In particular, the lower end face of the shaft sleeve can be provided with a taper, and a sand discharge port and a corresponding sealing cover are arranged at the lowest part of the lower end face. When we open the cover, we can discharge the deposited silt.

As another preferred scheme, as shown in fig. 1 and 4, a circular water pan 6 may be further disposed in the draft tube 5, and the center of the water pan is connected to the lower end of the spindle 7, so that the spindle can drive the water pan to rotate at a high speed. In addition, a round isolation convex rib 61 and a plurality of radial flow guide ribs 62 are arranged on the bottom surface of the water receiving tray, the isolation convex rib is coaxially arranged with the water receiving tray, the outer end of the flow guide rib is connected with the isolation convex rib, and the isolation convex rib separates a central water purification area 63 and a peripheral muddy water area 64 in the water receiving tray. In addition, the height of the isolation convex rib is lower than that of the flow guide rib, the height of the bottom surface of the water receiving tray gradually rises from the center to the outside until the bottom surface of the water receiving tray is flush connected with the isolation convex rib, and therefore the bottom surface of the water receiving tray forms a conical surface with a low middle part and high periphery.

Thus, when the water turbine is running, the water flow discharged to the downstream in the draft tube falls to the water receiving tray and is stored in the water receiving tray. Meanwhile, the spindle drives the water receiving disc to rotate at a high speed, the water stored in the water receiving disc forms a great centrifugal force by the high-speed rotating water receiving disc, at the moment, silt mixed in the water can move radially from the water purification area to the muddy water area along the conical bottom surface preferentially and enters the muddy water area, and the sediment can be reduced to the greatest extent from being blocked and deposited when moving radially, so that the silt can be ensured not to be deposited in the water purification area and be deposited to the muddy water area as much as possible, and the silt in the muddy water area can be prevented from flowing back to the water purification area when the water is pumped outwards in the water purification area through the water pump. Accordingly, the amount of silt contained in the water purification area in the isolation convex rib is greatly reduced. In the step a, when the water pump is started, the water pump can pump out the water flow in the shaft sleeve and the water purification area of the water receiving disc to form pressure water flow, so that the sufficiency of a pressure water flow water source can be ensured, and the content of silt in the pressure water flow can be reduced. It can be understood that a water outlet which penetrates through the water purifying area and is connected with the water pump through a pipeline is arranged on the lower side of the water receiving tray.

It can be understood that the diversion ribs separate a plurality of fan-shaped water purification areas in the water pan, thereby facilitating the silt to move radially outwards under the action of centrifugal force.

Finally, as shown in fig. 5, a slow flow cover 8 can be covered at the upper opening of the water pan, a plurality of drainage tubes 81 extending to the edge in the radial direction are arranged on the lower side of the slow flow cover, the drainage tubes are uniformly distributed in the circumferential direction, a plurality of groups of drainage holes 82 are arranged on the upper side of the slow flow cover, each group of drainage holes penetrates through the corresponding drainage tube, and each group of drainage holes are distributed at intervals in the length direction of the drainage tube.

When rivers fall to slowly flow and cover, can get into in the drainage tube that corresponds through the drainage hole to in the muddy water region of drainage tube flow to water collector edge. By reasonably setting the number and the aperture of the drainage holes, water in the wake pipe can be ensured to quickly enter the water pan, and the 'dumped' water flow in the wake pipe can be prevented from directly entering the water pan to stir silt.

When water flow in the tail water pipe falls on the slow flow cover on the water receiving tray, the water flow can enter the drainage pipe through the drainage holes and then radially flow along the drainage pipe under the action of centrifugal force to enter a muddy water area.

That is, the water flow is first supplemented to the muddy water region, and when the water level of the muddy water region rises and is higher than the isolation convex rib, the water flow reversely flows to the water purification region, and the sediment mixed in the water is deposited in the muddy water region by the action of the centrifugal force. That is to say, rivers can form the reposition of redundant personnel in the defrosting tray, and the upper and lower two-layer radial convection current of reposition of redundant personnel, the clear water of upper strata returns to the water purification region, and the silt of lower floor then flows to the muddy water region.