CN115822839A

CN115822839A - Energy recovery turbine draft tube with guide vanes

Info

Publication number: CN115822839A
Application number: CN202211453033.2A
Authority: CN
Inventors: 耿琳琳; 张德胜; 杨飞; 蒋文军
Original assignee: Yatai Pump Valve Co ltd; Wenling Institute Of Fluid Machinery Jiangsu University; Jiangsu University
Current assignee: Yatai Pump Valve Co ltd; Wenling Institute Of Fluid Machinery Jiangsu University; Jiangsu University
Priority date: 2022-11-19
Filing date: 2022-11-19
Publication date: 2023-03-21

Abstract

The invention provides an energy recovery turbine draft tube with guide vanes, belongs to the technical field of fluid machinery, and is mainly applied to an energy recovery turbine. After high-pressure water flows through the volute and the impeller, under the influence of self inertia and impeller rotation, the high-pressure water has a larger peripheral speed to form a vortex when entering the draft tube, and when the turbine operates under the working conditions of small flow and large flow, the vortex rotating direction in the draft tube is opposite, and the vortex flow field causes larger kinetic energy loss in the draft tube and generates additional pressure pulsation. The guide vane is installed in the tail water pipe and has the main structure of movable upper vane and lower vane fixed to the inner wall of the tail water pipe. The effect of reducing the peripheral speed of the tail water is realized by adjusting the angle of the upper blades, and the tail water is guided to move downstream along the axial direction through the axial arrangement of the lower blades. The swirl strength in the draft tube is reduced by adding the guide vanes, pressure pulsation in the draft tube is weakened, and efficient and stable operation of the energy recovery turbine is facilitated.

Description

Energy recovery turbine draft tube with guide vanes

Technical Field

The invention relates to the technical field of fluid machinery, in particular to an energy recovery turbine draft tube with guide vanes.

Background

The energy recovery turbine is added into the reverse osmosis seawater desalination system, so that the effect of recycling the energy of high-pressure water which does not penetrate through the desalination membrane can be realized. The method is one of the most effective ways to reduce the construction cost and the operation cost. The common energy recovery turbine in engineering mainly has two forms, one is a special hydraulic turbine, and the other is a centrifugal pump reverse rotation turbine, wherein the centrifugal pump reverse rotation turbine has the economic and technical advantages of simple structure, small volume, easy maintenance and the like, and is widely applied to actual production.

The structure of the energy recovery turbine is very similar to that of a centrifugal pump, except that the main shaft and the impeller rotor rotate in opposite directions. Therefore, in order to save design and processing cost, the energy recovery turbine is usually used by selecting a centrifugal pump meeting certain design requirements to reversely rotate as the turbine. In the using process, high-pressure water enters from the volute to drive the turbine impeller to rotate, the pressure energy of the fluid is converted into mechanical energy, the purpose of energy recovery is achieved, and then the fluid flowing through the impeller is discharged through the draft tube.

However, when fluid flows through the impeller into the draft tube, a vortex is generated in the draft tube due to the high speed rotation of the impeller and the influence of the flow of high pressure water in the impeller. And the direction of rotation of such a vortex will vary with the flow. As shown in fig. 2, when the flow rate of the turbine operating condition is much larger than the flow rate of the design condition, the rotation direction of the vortex in the tail water pipe is opposite to the rotation direction of the impeller; and when the flow rate of the turbine operating condition is much smaller than that of the designed working condition, the rotation direction of the vortex is the same as that of the impeller.

The existence of the vortices causes extra kinetic energy loss in the tail water pipe, so that the hydraulic efficiency of the turbine is reduced, and meanwhile, certain pressure pulsation is brought, so that the safe, stable and long-term operation of the turbine is threatened. Therefore, how to effectively improve the swirling flow field in the draft tube is very important for the efficient and stable operation of the energy recovery turbine.

Disclosure of Invention

Aiming at the characteristics of the internal vortex field of the tail water pipe of the energy recovery turbine, the invention provides the tail water pipe of the energy recovery turbine with the guide vanes, and the guide vanes in the tail water pipe can adjust the angle of the upper vanes according to the flow so as to achieve the effect of reducing the velocity component in the inner circumferential direction of the tail water pipe, thereby reducing the internal vortex strength of the tail water pipe, reducing the energy loss and weakening the pressure pulsation.

In order to achieve the purpose, the technical scheme of the invention is as follows: at a position slightly downstream from the draft tube inlet, guide vanes are installed, which mainly serve to reduce the circumferential velocity component of the fluid in the draft tube and at the same time guide the fluid to move axially.

Further, the guide vanes are divided into upper vanes and lower vanes, the upper vanes are rotating vanes, and the lower vanes are fixed vanes.

Further, the number of guide vanes is 3, and the included angle is 120 degrees.

Furthermore, the lower blades of the guide vanes are fixedly connected with the draft tube, and the upper blades and the lower blades are connected through hinges.

Furthermore, the axial section of the lower blade is rectangular, the thickness h of the lower blade of the guide vane is 2mm, the width b of the lower blade is one half of the radius R of the draft tube, and the length a of the lower blade is equal to the radius R of the draft tube.

Furthermore, the thickness h of the upper blade of the guide vane is 2mm, the cross section of the upper blade is in a right trapezoid shape, the upper short edge d of the trapezoid is three fourths of the length b of the lower short edge, and the height c of the trapezoid is three fourths of the length b of the lower short edge.

Further, the included angle theta between the upper blade and the lower blade of the guide vane is adjustable between 150 degrees and 210 degrees.

Furthermore, a gap exists between the right inclined surface of the upper blade of the guide vane and the inner wall of the tail water pipe so as to ensure that the upper blade rotates within an adjustable angle range.

The invention provides an energy recovery turbine draft tube with guide vanes, which has the following beneficial effects:

the invention provides an energy recovery turbine draft tube with guide vanes. The circumferential component of the incoming flow of the draft tube is weakened through the angle of the upper blades, and the incoming flow is guided to move along the axial direction through the axial arrangement of the lower blades. The number of the guide vanes is 3, so that the swirl flow field in the draft tube can be effectively inhibited, and the impact loss of water flow and the guide vanes is weakened. The invention reduces the circumferential component of the incoming flow in the draft tube by introducing the guide vanes, thereby playing the roles of inhibiting the internal vortex strength of the draft tube, weakening the pressure pulsation of the draft tube and improving the energy recovery efficiency of the turbine.

Drawings

In order to more clearly illustrate the technical solution of the present invention, the drawings needed for the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

FIG. 1 is a schematic diagram of the direction of a swirling flow field in a draft tube of an energy recovery turbine of the prior art;

FIG. 2 is a schematic diagram of an energy recovery turbine according to an embodiment of the present invention;

FIG. 3 is a three-dimensional schematic view of a guide vane in a tailwater pipe according to an embodiment of the present invention;

fig. 4 is a three-dimensional schematic view of a guide vane provided in an embodiment of the present invention, where an included angle between an upper blade and a lower blade is 180 degrees;

fig. 5 is a cross-sectional view of an axial plane where a guide vane is located in a tail water pipe according to an embodiment of the present invention.

Wherein the reference numerals in the figures correspond to: 1-volute, 2-impeller, 3-draft tube, 4-guide vane, 5-upper vane, and 6-lower vane.

Detailed Description

The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

Example (b):

referring to fig. 2, fig. 2 is a three-dimensional block diagram of a centrifugal pump in reverse rotation for use as an energy recovery turbine. The energy recovery turbine mainly comprises a volute 1, an impeller 2 and a draft tube 3; wherein the draft tube 3 is internally provided with guide vanes 4, and as shown in fig. 3-5, the guide vanes 4 comprise upper vanes 5 and lower vanes 6.

The number of the guide vanes 4 is 3, the upper vanes 5 of the guide vanes can rotate, the lower vanes 6 of the guide vanes are fixed on the inner wall of the draft tube, and the upper vanes and the lower vanes are connected through a hinge, so that the included angle theta between the upper vanes 5 and the lower vanes 6 can be adjusted between 150 degrees and 210 degrees.

As shown in fig. 1-2, when the operating condition of the energy recovery turbine is greater than the design flow rate, high-pressure water enters from the volute 1 to drive the impeller 2 to rotate so as to convert the pressure energy of the high-pressure water into mechanical energy. In this condition, the water flow is influenced by the rotation of the impeller and its own inertia, and has a strong peripheral speed when entering the draft tube 3, thereby forming a vortex having a direction of rotation opposite to that of the impeller 2. When the turbine operates at a flow rate less than the design flow rate, a vortex is formed which rotates in the same direction as the direction of rotation of the impeller 2. The existence of the two types of vortexes causes the flow field of the turbine in the draft tube to be disordered, the energy loss is increased, and an additional pressure pulsation phenomenon is generated. As shown in fig. 3-5, the present invention employs three guide vanes 4 added to the draft tube 3 to guide the draft to move axially. When the turbine operates in a low-flow working condition, the angle theta between the upper blade 5 of the guide vane and the lower blade 6 is adjusted to be between 190 degrees and 210 degrees by rotating the upper blade 5 of the guide vane, so that the included angle between the tangential direction of the circumferential direction of the tail water and the upper blade 5 is smaller than 180 degrees, and the direction of the tail water is changed. And the tail water is further guided to move axially by the lower blades 6 arranged axially. When the turbine operates under the working condition of large flow, the angle theta between the upper guide vane blade 5 and the lower guide vane blade 6 is adjusted to be within the range of 150 degrees and 170 degrees, tail water opposite to the rotation direction of the impeller is forced to impact the upper guide vane blade 5, and then the flow direction is changed to start to move along the axial direction.

Through above embodiment, the effect of drainage has been played in the interpolation of guide vane in the draft tube for draft circumferential velocity reduces to some extent, and kinetic energy loss and vortex intensity that arouse by the circumferential velocity and then reduce, and pressure pulsation weakens in the draft tube, thereby effectively improves energy recovery turbine's recovery efficiency and operating stability.

The embodiments described above are only a part of the embodiments of the present invention, and not all of the embodiments. Its purpose is to enable one of ordinary skill in the art to understand the disclosure of the present invention and to practice it without undue experimentation. Therefore, equivalent changes made by the claims of the present invention are also covered by the scope of the present invention.

Claims

1. An energy recovery turbine draft tube with guide vanes is characterized by comprising a draft tube and guide vanes; the draft tube is of a cylindrical structure, and the guide vanes are arranged at the position slightly downstream of the inlet of the draft tube.

2. The draft tube of an energy recovery turbine with guide vanes according to claim 1, wherein said guide vanes are divided into upper vanes and lower vanes, said upper vanes are rotatable, said lower vanes are fixed to the inner wall of the draft tube, and said upper and lower vanes are connected by hinges.

3. The draft tube of an energy recovery turbine with guide vanes according to claim 1, wherein the number of guide vanes is 3 and the angle between the vanes is 120 °.

4. The draft tube of an energy recovery turbine according to claim 3, wherein the axial cross-section of the upper blade is rectangular trapezoid and the axial cross-section of the lower blade is rectangular.

5. The draft tube of an energy recovery turbine with guide vanes according to claim 3, wherein the length of the long side of the cross section of the lower vane is equal to the radius of the inner wall surface of the draft tube, and the length of the wide side is equal to one half of the radius of the inner wall surface of the draft tube; the length of the right-angle side of the section of the upper blade is equal to three-thirds of the radius of the inner wall surface of the draft tube, and the length of the short side is three-eighths of the radius of the inner wall surface of the draft tube.

6. An energy recovery turbine draft tube according to claim 3, wherein the angled edge of the upper blade is spaced from the inner wall of the draft tube.