Torsion pipe type water outlet runner and design method thereof

Abstract

The invention relates to the technical field of water conservancy and municipal administration, and discloses a design method of a twisted tube type water outlet runner, the design input condition of the water outlet runner is determined, and the width B and height H of the rectangular inner wall of the outlet surface of the water outlet runner are reasonably determined according to the design flow Q of a pump device and the water flow velocity V of the outlet surface of the water outlet runner; calculating an equivalent divergence angle beta according to the area of the inlet surface and the outlet surface of the water outlet flow channel and the length of the flow channel; preliminarily drawing up the constraint range of the torsion angle, and constructing a three-dimensional coordinate system by taking the circle center of the inlet circle of the water outlet runner as the origin of the coordinate system; in the three-dimensional coordinate system, the twisted surfaces of the twisted tube type water outlet flow channel in the four quadrant areas are preliminarily designed respectively, the twisted surfaces of the flow channel are optimized through the NSGA-II algorithm with the minimum spiral flow intensity and hydraulic loss as the target, and the finally optimized twisted tube type water outlet flow channel is obtained. Compared with the prior art, on the basis of an existing pump station water outlet flow channel optimization technology, the water outlet flow channel efficiency can be further improved.

Description

Technical Field

[0001] The present invention relates to the fields of water conservancy and municipal engineering, and in particular to a twisted-tube water outlet channel and a design method thereof. Background Art

[0002] The outlet flow channel refers to the flow passage from the outlet of the guide vane to the outlet pool of the water pump, and mainly has straight pipe type, siphon type, hump type and other structural forms. The function of the outlet flow channel is to better turn and diffuse the water flow in the process of flowing from the guide vane outlet into the outlet pool. However, due to the dual influence of the residual circulation at the outlet of the guide vane and its own inertia, the flow distribution of water in the outlet flow channel is uneven and the flow state is poor, which is easy to produce spiral water flow, increase the head loss, and thus reduce the efficiency of the pump device. At present, the structural design of the outlet flow channel of the pump station is often limited by the flow velocity of the outlet section and the outlet surface of the guide vane. The length of the outlet flow channel along the center line of the water flow direction is determined by calculating the equivalent diffusion angle, and it is ensured that the cross-sectional area of the outlet flow channel changes uniformly along the center line of the flow channel. With the development of visualization experiment technology and computational fluid dynamics technology, both the engineering and scientific communities have realized that the water flow inside the outlet flow channel of low-lift pump stations is often spiral. However, the current design of the outlet flow channel does not take into account the diffusion effect of spiral flow, resulting in a bottleneck in the efficiency optimization of the outlet flow channel, which is difficult to break through. Summary of the Invention

[0003] Purpose of the invention: In response to the problems existing in the prior art, the present invention provides a design method for a twisted tube water outlet flow channel, which can further improve the efficiency of the water outlet flow channel on the basis of the existing pump station water outlet flow channel design technology, reduce the energy consumption of the pump station, and save the operating cost of the pump station.

[0004] Technical solution: The present invention discloses a design method for a twisted tube water outlet flow channel, comprising the following steps:

[0005] Step 1: Determine the design input conditions of the outlet flow channel. Based on the design flow rate Q of the pump device and the water flow velocity V at the outlet of the outlet flow channel, calculate and determine the radius R of the circular inner wall of the outlet flow channel inlet and the width B and height H of the rectangular inner wall of the outlet flow channel according to the standard requirements;

[0006] Step 2: Calculate the equivalent diffusion angle based on the inlet and outlet surface areas and the length of the outlet flow channel to determine whether the equivalent diffusion angle meets the standard requirements. If so, proceed to step 3. If not, adjust the inlet and outlet surface areas and the length of the outlet flow channel until they meet the standard requirements.

[0007] Step 3: Preliminary formulation of the optimization range of the torsion angle θ, the optimization range of the torsion angle θ is limited to between;

[0008] Step 4: Construct a three-dimensional coordinate system with the center of the circle at the flow channel inlet as the origin of the coordinate system;

[0009] Step 5: In the three-dimensional coordinate system, based on the input conditions designed in step 1, arrive Quadrant area, arrive Quadrant area, arrive Quadrant area, arrive Conduct preliminary design of the twisted surface of the twisted tube outlet flow channel in the quadrant area;

[0010] Step 5: Based on the analytical equation of the flow channel twist surface designed in step 4, a complete initial solution of the twisted tube outlet flow channel is obtained. With the goal of minimizing the spiral flow intensity and hydraulic loss, the NSGA-Ⅱ algorithm is used to optimize the twist angle of the twisted tube outlet flow channel, and the twisted tube outlet flow channel corresponding to the optimal twist angle θ is selected.

[0011] Furthermore, in step 4, the three-dimensional coordinate system sets the direction of the water outlet channel along the water flow as the positive direction of the coordinate system X axis, the width B direction of the outlet rectangle as the positive direction of the coordinate system Y axis, and the height H direction of the outlet rectangle as the positive direction of the coordinate system Z axis.

[0012] Furthermore, the analytical equation of the flow channel distortion surface designed in step 5 is as follows:

[0013] arrive The equation for the quadrant area is:

[0014]

[0015] arrive The equation for the quadrant area is:

[0016]

[0017] arrive The equation for the quadrant area is:

[0018]

[0019] arrive The equation for the quadrant area is:

[0020]

[0021] where θ is calculated in radians.

[0022] Furthermore, the calculation formula for the spiral flow intensity and hydraulic loss is:

[0023] Spiral flow intensity:

[0024]

[0025] Where: R is the radius of the outlet channel inlet surface, v θ is the tangential velocity of the outlet channel inlet, m / s, v Z is the axial velocity of the outlet channel inlet, m / s; r t is the radius of each point of the spiral flow, m; θ is the azimuth angle of each point of the spiral flow, rad;

[0026] Hydraulic loss:

[0027]

[0028] Where: P out is the total pressure at the outlet of the water flow channel, Pa; P in is the total pressure at the inlet of the outlet channel, Pa.

[0029] Beneficial effects:

[0030] 1. The twisted-tube outlet flow channel designed in this invention can further improve efficiency compared to existing straight-tube outlet flow channels. In a specific project, the flow channel length L can be set to a fixed value based on standards and experience from projects of similar scale. The equivalent diffusion angle is then calculated. If the equivalent diffusion angle meets the requirements of the "Pump Station Design Standard (GB50265-2022)", the optimal profile of the twisted-tube flow channel can be obtained by simply optimizing the twist angle θ.

[0031] 2. The present invention can improve the efficiency of the pump device under different head conditions by optimizing the straight pipe flow channel to a twisted pipe flow channel without increasing the project investment.

[0032] 3. The present invention aims to minimize the spiral flow intensity and hydraulic loss, and uses the NSGA-Ⅱ algorithm to optimize the torsion angle of the twisted tube water outlet flow channel. The twisted tube water outlet flow channel corresponding to the optimal torsion angle θ is selected. The NSGA-Ⅱ algorithm can select the optimal torsion angle to achieve the minimum spiral flow intensity and hydraulic loss, which can improve the efficiency value of the pump device. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Flowchart for the implementation of the present invention

[0034] Figure 2 The twist angle defined in the present invention is

[0035] Figure 3Schematic diagram of the twisted tube water outlet flow channel structure when the twist angle θ=0 of the present invention;

[0036] Figure 4 Schematic diagram of the twisted tube water outlet flow channel structure when the torsion angle θ≠0 of the present invention;

[0037] Figure 5 A three-dimensional structural diagram of a vertical axial flow pump device according to an embodiment of the present invention;

[0038] Figure 6 The implementation process of the torsion angle optimization for the present invention;

[0039] Figure 7 The pressure and streamline diagram of the middle cross section of the conventional straight pipe outlet flow channel (Q = 250l / s);

[0040] Figure 8 The pressure and streamline diagram of the middle cross section of the outlet channel of the optimized solution (Q=250l / s). DETAILED DESCRIPTION

[0041] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0042] The present invention discloses a design method for a twisted-tube water outlet flow channel, comprising the following steps:

[0043] Step 1: Determine the design input conditions for the outlet flow channel. Based on the design flow rate Q of the pump device and the water velocity V at the outlet of the outlet flow channel, calculate and determine the radius R of the circular inner wall of the outlet flow channel inlet and the width B and height H of the rectangular inner wall of the outlet flow channel in accordance with standard requirements. Step 2: Calculate the equivalent diffusion angle β based on the area of the outlet flow channel inlet surface, the area of the outlet surface, and the length of the outlet flow channel. Determine whether the equivalent diffusion angle β meets the standard requirements. If it does, proceed to Step 3. If it does not, adjust the area of the outlet flow channel inlet surface, the area of the outlet surface, and the flow channel length L until the standard requirements are met. The calculation method for the equivalent diffusion angle β is:

[0044]

[0045] Step 3: Preliminary formulation of the optimization range of the torsion angle θ, the optimization range of the torsion angle θ is limited to between.

[0046] Step 4: Establish a three-dimensional coordinate system, set the center of the flow channel inlet circle as the origin of the coordinate system, the direction of the water flow of the outlet flow channel as the positive direction of the coordinate system X axis, the width B direction of the outlet rectangle as the Y direction of the coordinate system, and the height H direction of the outlet rectangle as the positive direction of the coordinate system Z axis.

[0047] Step 5: In the three-dimensional coordinate system, arrive Quadrant area, arrive Quadrant area, arrive Quadrant area, arrive The twisted surface of the quadrant area is designed, and based on the input conditions, the twisted surface analytical equation of the initial scheme twisted tube outlet flow channel is obtained.

[0048] arrive The equation for the quadrant area is:

[0049]

[0050] arrive The equation for the quadrant area is:

[0051]

[0052] arrive The equation for the quadrant area is:

[0053]

[0054] arrive The equation for the quadrant area is:

[0055]

[0056] where θ is calculated in radians.

[0057] Step 6: Based on the analytical equation of the flow channel twist surface designed in step 4, a complete initial solution of the twisted tube outlet flow channel is obtained. With the goal of minimizing the spiral flow intensity and hydraulic loss, the NSGA-Ⅱ algorithm is used to optimize the twist angle of the twisted tube outlet flow channel. Before optimization, the restriction range of the twist angle θ is given, and the twisted tube outlet flow channel profile corresponding to the optimal twist angle θ is selected.

[0058] Spiral flow intensity:

[0059]

[0060] Where: R is the radius of the outlet channel inlet surface, v θ is the tangential velocity of the outlet channel inlet, m / s, v Z is the axial velocity of the outlet channel inlet, m / s; r t is the radius of each point of the spiral flow, m; θ is the azimuth angle of each point of the spiral flow, rad;

[0061] Hydraulic loss:

[0062]

[0063] Where: P out is the total pressure at the outlet of the water flow channel, Pa; P in is the total pressure at the inlet of the outlet channel, Pa.

[0064] Example:

[0065] A large pumping station in Anhui Province was selected as the research object. The pumping station has 9 sets of equipment and a drainage flow of 101m 3 / s. The equivalent diffusion angle of the outlet flow channel of the pump station is calculated and the equivalent diffusion is relatively 9.6°, which meets the requirement of Section 10.2.5 of the "Pump Station Design Standard (GB50265-2022)" that the equivalent diffusion angle should be 8° to 12°. With the goal of minimizing the spiral flow intensity and hydraulic loss, the NSGA-Ⅱ algorithm is used to optimize the torsion angle of the twisted tube outlet flow channel. Given the constraint range of the torsion angle (-90°<θ<90°, that is, The hydraulic performance parameters of the twisted pipe outlet flow channel of the final optimization scheme and the straight pipe outlet flow channel of the initial scheme are compared in Table 1. The three-dimensional model of the initial and optimized vertical axial flow pump device is shown in Figure 5 Table 1 Comparison of pump device parameters before and after optimization

[0066] category Straight pipe outlet Twisted tube water outlet Luffing Torsion angle 0° 45° 45° Pump unit efficiency 64.651％ 65.243％ +0.592％ Hydraulic loss 6.19cm 3.67cm -2.52cm Spiral flow intensity 0.25 0.17 0.08

[0067] Under low flow conditions (Q = 250 L / s), the efficiency of the pump device of the twisted tube water outlet flow channel is higher than that of the conventional straight tube water outlet flow channel. After optimization, the efficiency of the pump device of the twisted tube water outlet flow channel is increased by 0.592%, the hydraulic loss of the twisted tube water outlet flow channel is reduced by 40.71%, and the spiral flow intensity is reduced by 0.08. The design method proposed in the present invention can not only improve the hydraulic loss of the pump device, but also increase the stability of the water flow in the water outlet flow channel.

[0068] The pressure and streamlines of the middle cross section of the conventional straight pipe outlet flow channel and the optimal twisted pipe outlet flow channel are as follows: Figure 7 and Figure 8 As shown, it can be seen that the velocity distribution in the middle section of the twisted tube outlet flow channel is more uniform, indicating that the pressure energy is recovered more fully and the water flow is diffused more evenly, which is consistent with the result of improved pump device efficiency.

[0069] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A design method for a twisted tube water outlet channel, characterized in that: The following steps are involved: Step 1: Determine the design input conditions of the outlet flow channel. Based on the design flow rate Q of the pump device and the water flow velocity V at the outlet of the outlet flow channel, calculate and determine the radius R of the circular inner wall of the outlet flow channel inlet and the width B and height H of the rectangular inner wall of the outlet flow channel according to the standard requirements; Step 2: Calculate the equivalent diffusion angle based on the inlet and outlet surface areas and the length of the outlet flow channel to determine whether the equivalent diffusion angle meets the standard requirements. If so, proceed to step 3. If not, adjust the inlet and outlet surface areas and the length of the outlet flow channel until they meet the standard requirements. Step 3: Preliminary formulation of the optimization range of the torsion angle θ, the optimization range of the torsion angle θ is limited to between; Step 4: Construct a three-dimensional coordinate system with the center of the circle at the flow channel inlet as the origin of the coordinate system; Step 5: In the three-dimensional coordinate system, based on the input conditions designed in step 1, arrive Quadrant area, arrive Quadrant area, arrive Quadrant area, arrive Conduct preliminary design of the twisted surface of the twisted tube outlet flow channel in the quadrant area; Step 5: Based on the analytical equation of the flow channel twist surface designed in step 4, a complete initial solution of the twisted tube outlet flow channel is obtained. With the goal of minimizing the spiral flow intensity and hydraulic loss, the NSGA-Ⅱ algorithm is used to optimize the twist angle of the twisted tube outlet flow channel, and the twisted tube outlet flow channel corresponding to the optimal twist angle θ is selected.

2. The design method of a twisted tube water outlet channel according to claim 1, characterized in that: In step 4, the three-dimensional coordinate system sets the direction of the water outlet channel along the water flow as the positive direction of the coordinate system X axis, the width B direction of the outlet rectangle as the positive direction of the coordinate system Y axis, and the height H direction of the outlet rectangle as the positive direction of the coordinate system Z axis.

3. The design method of a twisted tube water outlet channel according to claim 1, characterized in that: The analytical equation of the flow channel distortion surface designed in step 5 is as follows: arrive The equation for the quadrant area is: arrive The equation for the quadrant area is: arrive The equation for the quadrant area is: arrive The equation for the quadrant area is: where θ is calculated in radians.

4. The design method of a twisted tube water outlet channel according to claim 1, characterized in that: The calculation formula of the spiral flow intensity and hydraulic loss is: Spiral flow intensity: Where: R is the radius of the outlet channel inlet surface, v θ is the tangential velocity of the outlet channel inlet, m / s, v Z is the axial velocity of the outlet channel inlet, m / s; r t is the radius of each point of the spiral flow, m; θ is the azimuth angle of each point of the spiral flow, rad; Hydraulic loss: Where: P out is the total pressure at the outlet of the water flow channel, Pa; P in is the total pressure at the inlet of the outlet channel, Pa.

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