CN105363656A - Method for lowering water conveying pipe head losses - Google Patents

Abstract

The invention provides a method for reducing water head loss of a water delivery pipeline. A layer of anti-friction material is pasted or coated on the inner wall of the water delivery pipeline. The anti-friction material is an imitation shark skin anti-friction material or a nanometer superhydrophobic material. The anti-friction material imitating sharkskin can be directly pasted on the surface of the water pipeline, or a layer of base material can be sprayed first to improve the adhesion between the imitation sharkskin material and the pipe wall; the nano-hydrophobic material can be directly coated on the water pipeline The surface can also be sprayed with a layer of base material to improve the adhesion between the nanomaterial and the tube wall. Nano-hydrophobic materials can be mixed with nano-anti-abrasion materials to achieve the two purposes of reducing frictional resistance and resisting abrasion. This method can reduce the adhesion force and flow resistance on the solid-liquid surface, effectively improve the hydrophobic performance of the surface of the water pipeline, and reduce the loss along the pipeline during the water transportation process.

Description

A Method for Reducing Head Loss of Water Pipeline

technical field

The invention relates to the technical fields of water conservancy and hydropower engineering, hydrology and water resources engineering, and water environment engineering, in particular to a method for reducing water head loss of a water delivery pipeline.

Background technique

Hydropower is an important means of converting water energy into electrical energy and obtaining electricity. The installed capacity of my country's hydropower stations has reached 300 million kilowatts (300,000 MW), accounting for 27% of my country's total power generation, and occupies an important position in my country's energy structure.

Most hydroelectric power generation requires the use of water diversion pipes to lead water from the reservoir to the hydroelectric generator. The long-term distance of the water diversion pipe to the reservoir is between tens of meters and several kilometers, and the pipe diameter and water flow in the pipe vary depending on the scale of power generation. . The flow of high-speed water in the diversion pipe will cause head loss due to turbulent friction between the water and the pipe wall. According to incomplete statistics, the head loss of the diversion pipe section of the built power station is 1-8m, accounting for 1-8% of the total head. Head loss consumes water energy, reduces power generation, and causes energy loss.

The head loss of the water pipe comes from the friction between the flowing water and the pipe wall, and the calculation of the head loss is as follows:

Darcy's formula $h_f=\mathrm{\λ}\frac{l}{d}\frac{v^2}{2g}---\left(1\right)$

Chezy formula $v=C\sqrt{Ri}---\left(2\right)$

in: $\frac{1}{\sqrt{\mathrm{\λ}}}=-2\lg (\frac{\mathrm{\Δ}}{3.7d}+\frac{2.51}{\mathrm{Re}\sqrt{\mathrm{\λ}}})---\left(3\right)$

$\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; Re</span>}}^{\mathrm{<span\; class="notranslate">\; the\; y</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

$\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 2.5</span>}\sqrt{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.13</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.75</span>}\sqrt{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; (</span>\sqrt{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

In the formula: h _f is the loss along the way, m; λ is the resistance coefficient along the way; l is the length of the pipe section, m; d is the calculated inner diameter of the pipeline, m; g is the acceleration of gravity, m/s ² ; i is hydraulic gradient; R is hydraulic radius, m; v is flow velocity, m/s; Re is Reynolds number; n is roughness coefficient.

It can be seen from formulas (1) to (5) that the head loss has a linear relationship with the roughness coefficient, and the friction and head loss can be reduced by taking measures to reduce the roughness coefficient n.

In the past, reducing head loss in water pipelines was mainly achieved by reducing water flow velocity and increasing pipe diameter; in addition, some anti-friction and drag-reducing materials such as epoxy resin and sprayed polyurea have also begun to be applied to gas and oil pipelines. However, the coating of superhydrophobic materials in existing water pipes only stays in the experimental stage. The diameter of the pipes is small, and the pipes are mainly made of metal pipes and plastics. The water flow rate is usually between 5 and 20m/s. With the implementation of projects such as the South-to-North Water Diversion Project, large-scale high-head hydropower stations have begun to be constructed one after another. Most of the water delivery pipelines used in high-head hydropower stations such as pumped storage are large-diameter and concrete pipes, which have higher surface energy and greater resistance to water flow. , while the maximum discharge velocity of high-head hydropower stations can reach 50m/s. According to the formula, it can be seen that the head loss will rapidly increase with the square of the flow velocity, resulting in greater energy loss. Therefore, the establishment of high-head hydropower stations puts forward higher requirements on the drag reduction performance and hydrophobicity of materials, and the existing technologies for reducing head loss cannot meet the requirements of reducing head loss in high-head hydropower stations.

Contents of the invention

The purpose of the present invention is to provide a method for reducing the friction of the inner wall of the water delivery pipe to reduce the loss of water head against the deficiencies of the prior art.

In order to achieve the above object, the present invention provides a method for reducing the head loss of the water pipeline, coating or sticking a layer of anti-friction material on the inner wall of the water pipeline, the anti-friction material is an imitation shark skin anti-friction material, nano-hydrophobic materials or nano-superhydrophobic materials.

Further, the antifriction material imitating sharkskin is pasted on the surface of the water delivery pipeline in the following manner: 1) using an adhesive to directly paste the antifriction imitation sharkskin material on the surface of the water delivery pipeline; or 2) spraying a The base material with a layer thickness of 0.02-0.15 mm, and then use an adhesive to stick the imitation shark skin wear-reducing material to the base material.

Further, the nano-hydrophobic material or nano-super-hydrophobic material is sprayed on the surface of the water delivery pipeline in the following manner: 1) directly coating the nano-hydrophobic material or nano-super-hydrophobic material on the surface of the water delivery pipeline, or 2) spraying a layer first base material, and then coated with nano-hydrophobic material or nano-super-hydrophobic material.

Further, the antifriction material imitating sharkskin is silicone rubber overmolding PU (polyurethane for short) imitating sharkskin, silicone rubber overmolding PDMS (polydimethylsiloxane) imitating sharkskin or polyurethane-based Imitation shark skin.

Further, the nano-hydrophobic material or nano-superhydrophobic material is one of nano-organosilicon or its modified resin, nano-fluorine resin or its modified resin.

Further, the adhesive is a neutral silicone sealant, and the base material is an adhesion promoter, preferably a 3M94 primer adhesion promoter.

Further, add 10-30% nano anti-abrasion material to the nano-superhydrophobic material or nano-hydrophobic material, and then paint after the two are mixed to achieve the two purposes of reducing frictional resistance and resisting abrasion. The nano anti-abrasion material is preferably an anti-abrasion coating of nano Al ₂ O ₃ /ZrO ₂ epoxy resin.

Further, the coating method includes brush coating, roller coating, dip coating, air spray coating, high-pressure airless spray coating and electrostatic spray coating, etc. According to different pipe materials, one or several coating methods can be used at the same time. .

Further, before coating the inner wall of the water pipeline by pasting or painting, the surface of the pipeline needs to be treated.

Further, when dealing with water pipelines to reduce head loss and improve water delivery efficiency, related equipment should be adjusted. For example, if used in a hydropower station, surge wells and turbines need to be adjusted to adapt to the new water head.

The anti-friction material selected in the present invention is an imitation shark skin anti-friction material, a nano-hydrophobic material or a nano-super-hydrophobic material.

Among them, according to research, the rough V-shaped folds on the surface of the shark's skin can subtly generate water eddies, greatly reducing the friction of the water flow, allowing the water around the body to flow through more efficiently, and the shark can swim quickly. In addition, there is a water film on the outer surface of the shark skin. This water film converts the friction between water and skin into the friction between water and water, which reduces the friction force during the running process and plays a role in reducing drag. The physical properties of this water film have low surface energy, which makes it difficult for marine organisms to attach or even if attached, its cohesive force is very small, and it is easy to be automatically removed. The structure imitating shark skin can simulate this V-shaped fold, and form a water film on the inner surface of the water pipeline, so that the friction between the pipe wall and the water flow is reduced, the roughness coefficient is reduced, and the head loss is reduced. At the same time, it can also reduce the chance of foreign matter sticking to the hydrophobic pipe, which is easy to clean.

Nano-hydrophobic materials refer to surfaces with a contact surface of greater than 90° and a rolling angle of less than 10°. Nano-superhydrophobic materials are surfaces with a contact surface of greater than 150° and a rolling angle of less than 10°. Super-hydrophobic surfaces such as the surface of lotus leaves , can produce a slip effect, thereby reducing the frictional resistance of the water pipeline, thereby reducing the roughness coefficient and reducing head loss. The nano-organosilicon or its modified resin and the nano-fluorine resin or its modified resin can be made into nano-hydrophobic materials or nano-super-hydrophobic materials according to different processes.

Use the method of painting/pasting to paint the inner wall of the water pipeline. Before painting, the surface of the pipeline needs to be treated. The steps are as follows:

(1) Mechanical cleaning: the inner and outer walls of the pipe are polished with sandpaper to wipe off the rust and retain a certain roughness;

(2) Chemical cleaning: use nitrate hydrochloric acid mixed solution, sodium hydroxide solution or deionized water for cleaning;

(3) Drying: Blow dry with cold wind, and wait for painting after drying.

After the surface treatment is completed, the inner wall of the water delivery pipe can be pasted with imitation shark skin material or sprayed with nano-hydrophobic material and nano-super-hydrophobic material. The coating methods include brushing, rolling, dipping, Air spraying, high-pressure airless spraying and electrostatic spraying, etc., depending on the pipe material, one or several coating methods can be used at the same time.

The specific steps for pasting are as follows:

(1) Apply the adhesive evenly on the inner surface of the water pipeline with brushes, rollers (without fiber shedding), and the general coating thickness is 0.02-0.04mm.

(2) Drying time: The drying time generally depends on the temperature, humidity and coating thickness. The normal drying time is 1 minute to 1 hour. During the drying period, care must be taken that the coating surface is absolutely free from contamination.

(3) Stick the imitation sharkskin material to the surface of the coating, and apply a certain pressure to make the imitation sharkskin material closely adhere to the inner surface of the water pipeline.

The specific steps of painting are as follows:

(1) For large-scale water pipelines, methods such as brushing and spraying can be used. When spraying inside the pipe, it can be sprayed with a spray gun. Nano-hydrophobic/super-hydrophobic materials or base materials are atomized by the spray gun and attached to the inner surface of the water pipeline; after spraying Dry at 60°C for 2-8 hours or at room temperature for 12-48 hours.

(2) Dip-coating and other methods can be used for water pipelines with small diameters. When dip-coating, pour the nano-hydrophobic/super-hydrophobic coating or base material into the dip-coating container and let it stand for 3-8 minutes; slowly and evenly Put the water pipe vertically into the paint liquid at the same speed, stay for 20-100s, take it out from the paint at the same speed, and put it in a clean place to drip dry for 10-30 minutes. Control the drying degree of the first paint film to ensure that the paint film will not hang, bite or wrinkle after the second dipping; turn the water pipe upside down 180°, and carry out the second dipping according to the above method. Dip coating, drip dry; after dip coating, dry at 60°C for 2-8h or at room temperature for 12-48h.

When replacing the original drainage pipeline with the drainage pipeline prepared according to the method of the present invention to improve water delivery efficiency, it is necessary to adjust related equipment, such as being used in a hydropower station, it is necessary to adjust the surge well and the water turbine to adapt to the new water head .

The beneficial effects of the present invention are:

The invention provides a method for reducing the head loss of the water delivery pipeline. By sticking or coating the anti-friction material on the inner wall of the water delivery pipeline, the friction between the pipe wall and the water flow is reduced, thereby reducing the head loss during the water delivery process. , the maximum drag reduction rate can reach 24.6% in the actual test, breaking through the 10% drag reduction bottleneck of the bionic trench structure.

The method provided by the invention can be used in water diversion pipelines, water pipelines, oil pipelines and urban water supply pipelines of hydropower stations to reduce frictional resistance of water flow, reduce water head loss and improve operating efficiency.

Description of drawings

Fig. 1 is the structural representation of the imitation sharkskin material directly pasting the inner wall of the water pipeline in the present invention.

Fig. 2 is a structural schematic diagram of the inner wall of the water delivery pipeline in which the base material is first sprayed and then the imitation shark skin material is pasted in the present invention.

Fig. 3 is a structural schematic diagram of the nano-hydrophobic material or the nano-super-hydrophobic material directly spraying the inner wall of the water delivery pipeline in the present invention.

Fig. 4 is a schematic structural view of the inner wall of the water delivery pipeline in which the base material is sprayed first and then coated with nano-hydrophobic material or nano-superhydrophobic material in the present invention.

Reference signs:

1: water pipeline; 2: imitation shark skin material; 3: substrate material; 4: nano-hydrophobic material or nano-super-hydrophobic material.

detailed description

The present invention will be described in detail below in conjunction with the implementations shown in the drawings, but it should be noted that these implementations are not limitations of the present invention, and those of ordinary skill in the art based on the functions, methods, or structural changes made by these implementations Equivalent transformations or substitutions all fall within the protection scope of the present invention.

The polyurethane-based imitation shark skin used in the present invention is purchased from Beijing Zema New Technology Co., Ltd.

The silicone rubber molded PU imitation shark skin used in the present invention, the silicone rubber molded PDMS imitation shark skin are self-made in the laboratory, and the main process is:

1. Prepare the shark skin sample: remove the meat and tendons on the back of the fresh shark skin and soak it in 10% formalin solution; pave the soaked shark skin flat and clamp it on a smooth and flat hard board ( Such as glass) or stretched in a cylinder, placed in an oven at 50 ° C to dry; on the back of the dried shark skin coated with about 1cm of Belzona 1311 repair material, on the side with the shield scales covered with a piece A hard board with a smooth and flat surface, slightly pressurized to flatten the repair material layer, and cured in the room for 24 hours to obtain a flat shark skin sample.

2. Liquid silicone replica mold: Spray an appropriate amount of dry high-efficiency release agent on the shark skin sample, pour the evenly mixed two-component liquid silicone rubber on the shark skin, and put it in a vacuum device to vacuum for 30 seconds. Then slowly open the air valve to inflate to fully discharge the air bubbles in the liquid silicone; cure at room temperature for more than 30 minutes, and then demould, use this as a replica mold, transfer the surface microstructure to PU or PDMS, and obtain a silicone rubber molded PU Imitation shark skin or silicone rubber overmolded PDMS imitation shark.

Nano-organosilicon and its modified resin, nano-fluorine resin and its modified resin used in the present invention are commercially available products, and according to different processes, it can be nano-organosilicon and its modified resin, nano-fluorine resin and its Modified resin, or nano organosilicon and its modified resin, nano fluorine resin and its modified resin belonging to nano superhydrophobic material.

Adhesion promoter 3M94 primer adhesion promoter used in the present invention is a commercially available product.

The nanometer Al ₂ O ₃ /ZrO ₂ epoxy resin used in the present invention is purchased from Nanjing Epurui Nano Material Co., Ltd.

Example 1

As shown in Figure 1, the imitation sharkskin material 2 is directly pasted on the inner wall of the water delivery pipe 1, and the imitation sharkskin material used is a silicone rubber molded PU imitation sharkskin. The specific process is as follows:

1. Surface treatment: (1) The inner and outer walls of the pipe are polished with sandpaper to wipe off the rust and retain a certain roughness; (2) Use 2% sodium hydroxide solution to clean; (3) Blow dry with cold wind, and the drying is completed waiting for painting;

2. Paste imitation shark skin material:

(1) Apply the neutral silicone sealant evenly on the inner surface of the surface-treated water pipeline with a brush, and the coating thickness is 0.03mm.

(2) Dry for 30 minutes. During drying, care must be taken that the surface of the coating is absolutely free from contamination.

(3) Paste the silicone rubber molded PU imitation shark skin on the surface of the coating, and apply a certain pressure to make the imitation shark skin closely adhere to the inner surface of the water pipeline.

Example 2

As shown in Figure 2, in order to first spray the base material 3 on the inner wall of the water pipeline 1, and then paste the imitation sharkskin material 2, the imitation sharkskin material used is polyurethane-based imitation sharkskin, and the specific process is as follows:

1. Surface treatment, (1) sand the inner and outer walls of the pipe to wipe off the rust and retain a certain roughness; (2) use deionized water to clean; (3) dry it with cold wind, and wait for coating after drying. Pack;

2. Spray base material: 3M94 primer adhesion promoter is atomized by a spray gun and attached to the inner surface of the water pipe; the thickness of the spray is 0.1mm, and it is dried at 60°C for 7 hours after spraying;

3. Paste the imitation shark skin material:

(1) Apply the neutral silicone sealant evenly on the inner surface of the surface-treated water pipeline with a brush, and the coating thickness is 0.04mm.

(2) Dry for 40 minutes. During drying, care must be taken that the surface of the coating is absolutely free from contamination.

(3) Paste the polyurethane-based imitation shark skin on the surface of the coating, and apply a certain pressure to make the imitation shark skin material closely adhere to the inner surface of the water pipeline.

Example 3

As shown in Figure 3, the inner wall of the water pipeline 1 is directly coated with the nano-superhydrophobic material 4, and the nano-superhydrophobic material used is nano-organosilicon, and the specific process is as follows:

1. Surface treatment: (1) The inner and outer walls of the pipeline are polished with sandpaper to wipe off the rust and retain a certain roughness; (2) Use a mixed solution of 5% nitric acid and 5% hydrochloric acid to clean; (3) Use cold air Blow dry and wait for painting after drying;

2. Spray nano-superhydrophobic material: atomize the nano-organosilicon material with a spray gun and attach it to the inner surface of the water pipe; after spraying, dry it at 60°C for 5 hours.

Example 4

As shown in Figure 4, in order to first spray the base material 3 on the inner wall of the water pipeline 1, and then spray the nano-hydrophobic material 4, the coated nano-hydrophobic material is a modified nano-fluorine resin, and the specific process is as follows:

1. surface treatment, method is with the step 1 of embodiment 1;

2. Spray base material: 3M94 primer adhesion promoter is atomized by a spray gun and attached to the inner surface of the water pipe; the spray thickness is 0.04mm, and it is dried at room temperature for 15 hours after spraying;

3. Dip-coating nano-hydrophobic material: add nano-Al ₂ O ₃ /ZrO ₂ epoxy resin (the mass ratio of the two is 4:1) to the modified nano-fluororesin powder and mix evenly, then pour it into a dip-coating container, and let it stand. Put the water pipe vertically into the paint at a slow and uniform speed, stay for 60 seconds, take it out of the paint at the same speed, and put it in a clean place to drip dry for 20 minutes. Control the drying degree of the first paint film to ensure that the paint film will not hang, bite or wrinkle after the second dipping; turn the water pipe upside down 180°, and carry out the second dipping according to the above method. Dip coating, drip dry; after dip coating, dry at room temperature for 24 hours.

Adding nano anti-abrasion materials to nano-hydrophobic materials or nano-super-hydrophobic materials can simultaneously achieve the two purposes of reducing frictional resistance and resisting abrasion.

The method for reducing head loss provided by the present invention can effectively reduce the friction between the pipe wall and the water flow. In the actual test, according to the roughness coefficient of the same pipe before and after pasting or coating friction-reducing materials, the sticking Or the drag reduction rate of the coating antifriction material is not less than 20%, and the maximum can reach 24.6%. This method breaks through the bottleneck of 10% drag reduction of the bionic groove structure, and effectively reduces the head loss in the process of water delivery.

The invention provides the method, material and structural form for reducing the friction of the inner wall of the water delivery pipe, thereby reducing the head loss.

It will be apparent to those skilled in the art that the invention is not limited to the details of the above-described exemplary embodiments, but that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Accordingly, the embodiments should be regarded in all points of view as exemplary and not restrictive, the scope of the invention being defined by the appended claims rather than the foregoing description, and it is therefore intended that the scope of the invention be defined by the appended claims rather than by the foregoing description. All changes within the meaning and range of equivalents of the elements are embraced in the present invention. Any reference sign in a claim should not be construed as limiting the claim concerned.

In addition, it should be understood that although this specification is described according to implementation modes, not each implementation mode only includes an independent technical solution, and this description in the specification is only for clarity, and those skilled in the art should take the specification as a whole , the technical solutions in the various embodiments can also be properly combined to form other implementations that can be understood by those skilled in the art.

Claims (10)

1. reduce a method for the aqueduct loss of flood peak, it is characterized in that, paste or application one deck antifriction material at aqueduct inwall, this antifriction material is imitative sharkskin antifriction material, nano-sized hydrophobic material or nano superhydrophobic material.

2. the method for the reduction aqueduct according to claim 1 loss of flood peak, it is characterized in that, described imitative sharkskin antifriction material is pasted on aqueduct surface in the following manner: 1) use and paste agent and directly to be pasted by imitative sharkskin antifriction material on aqueduct surface; Or 2) first to spray a layer thickness be the base material of 0.02 ~ 0.15mm, re-use and paste agent imitative sharkskin antifriction material is pasted on base material.

3. the method for the reduction aqueduct according to claim 1 loss of flood peak, it is characterized in that, described nano-sized hydrophobic material or nano superhydrophobic material are sprayed on aqueduct surface in the following manner: 1) directly nano-sized hydrophobic material or nano superhydrophobic material are coated with and are contained in aqueduct surface, or 2) first spray one deck base material, then coating nano hydrophobic material or nano superhydrophobic material.

4. the method for the reduction aqueduct loss of flood peak according to any one of claim 1-3, is characterized in that, described imitative sharkskin antifriction material is that silicon rubber turns over that mould PU imitates sharkskin, PDMS imitates sharkskin or polyurethane-base imitates sharkskin.

5. the method for the reduction aqueduct loss of flood peak according to any one of claim 1-3, is characterized in that, described nano-sized hydrophobic material or nano superhydrophobic material are nano-organosilicon or its modified resin, nanometer fluororesin or its modified resin one wherein.

6. the method for the reduction aqueduct loss of flood peak according to any one of claim 1-3, is characterized in that, described in paste agent be sealing neutral silicone resin, described base material is adhesion promoter, and this adhesion promoter is preferably 3M94 primary coat adhesion promoter.

7. the method for the reduction aqueduct loss of flood peak according to claim 1 or 3, it is characterized in that, the nanometer resistant abrasion material of 10-30% is added in described nano superhydrophobic material or nano-sized hydrophobic material, carry out application again after the two is used in combination, described nanometer resistant abrasion material is preferably nanometer Al ₂o ₃/ ZrO ₂epoxy resin resistant abrasion coating.

8. a kind of method reducing the aqueduct loss of flood peak according to any one of claim 1-3, it is characterized in that, described coating process comprises brushing, roller coating, dip-coating, aerial spraying, airless spraying, electrostatic spraying, different according to tubing during application, can use wherein a kind of or use several application mode simultaneously.

9. a kind of method reducing the aqueduct loss of flood peak according to any one of claim 1-3, is characterized in that, before employing application or the method pasted carry out application to aqueduct inwall, carries out surface treatment to aqueduct, increases cohesive force.

10. a kind of method reducing the aqueduct loss of flood peak according to any one of claim 1-3, it is characterized in that, to aqueduct process, reduce the loss of flood peak, when improving emptying effectiveness, relevant device is adjusted, as power station, need adjust surge shaft and the hydraulic turbine, to adapt to new head.