A method and apparatus for naturally aerating a poppet valve spool

Abstract

The natural aeration method and device for protecting the valve core of a conical valve belong to the field of high-end water conservancy equipment. The natural aeration method for protecting the valve core of a conical valve comprises the following steps: arranging an annular aeration sill; arranging an aeration hole; the size of the aeration sill is set according to the diameter of the pipeline; the aeration hole is connected with aeration pipes at different levels. The conical valve with the valve core protected by natural aeration comprises the following parts: an aeration sill is arranged on the valve core of the conical valve; the length of the aeration sill is 1 / 4-1 / 6 of the nominal diameter of the valve; the height of the aeration sill is 1 / 10 of the length of the aeration sill; under the arrangement condition, the influence of the aeration sill on the flow capacity of the valve is less than 10%; the beneficial effect of the present application is that the aeration water flow can effectively cover the surface of the valve core after entering the valve body, including the water stop position of the valve seat, and the vibration amount of the valve is significantly reduced.

Description

Technical Field

[0001] This invention relates to a method and apparatus for natural air mixing to protect the valve core of a conical valve, belonging to the field of high-end equipment for water conservancy projects. Background Technology

[0002] In fluid systems, industrial valves, as control elements, are used to regulate the pressure, direction, and flow rate of fluids within pipelines, and are therefore widely used in water conservancy projects, petrochemical projects, and municipal engineering projects. There are many types of industrial valves; in water conservancy and waterway engineering, the main types include ball valves, gate valves, butterfly valves, piston valves, and cone valves.

[0003] The structural diagram of the fixed cone valve is as follows: Figure 1 As shown. The fixed cone valve contains a fixed cone valve core, which is generally fixed to the valve body by 4 to 6 blades. The end of the cone valve core is equipped with a sealing seat, i.e., the valve seat. The opening and closing of the valve is achieved by the back and forth movement of the sleeve. By changing the gap between the sleeve and the valve seat, the flow area of ​​the fluid in the valve is changed, thereby achieving precise control of the flow rate.

[0004] The valve core of a fixed cone valve is a crucial component. If the valve core is damaged, the cone valve will not function properly. If the valve seat is damaged, it will cause the valve to leak.

[0005] During the opening and closing of a valve, the fluid velocity increases abruptly and the pressure decreases due to the existence of a throttling and contraction section. When the pressure at a certain point in the fluid is lower than the saturated vapor pressure under local temperature conditions, the bubbles generated by vaporization inside the fluid will continue to grow and increase in volume, resulting in cavitation. When these bubbles formed in the low-pressure area flow with the fluid to the high-pressure area, they will collapse under the influence of the pressure difference inside and outside the bubbles, generating a huge instantaneous impact force, which can reach hundreds of atmospheres. This causes erosion of the solid wall surface in contact with the cavitation erosion, i.e., cavitation damage. Cavitation erosion damage is a problem that needs to be avoided for the safe and efficient operation of valves.

[0006] Regarding the cavitation problem of conical valves, relevant research indicates that air entrainment is an effective measure to reduce corrosion. Different air entrainment methods have also been proposed:

[0007] (1) The air mixing point is located on the pipe wall before the valve. The disadvantage is that an air compressor is required, the pressure of the pipe before the valve is high, the energy consumption of the compressor is also very high, and the layout is inconvenient.

[0008] (2) The gas injection point is located in the sleeve. The gas injection covers the outside of the main flow but cannot cover the inside of the main flow. Although it can effectively protect the valve core from cavitation damage to the pipe wall after the valve, its protective effect on the valve core is limited.

[0009] (3) The aeration point is located on the pipe wall downstream of the valve. This method is only used when the conical valve is used as a vent valve. When used as a valve in a pressurized pipeline, natural aeration cannot be achieved, and the aerated water flow only covers the pipe wall downstream of the valve. The specific reason is that when the conical valve is used as a flow control valve in a pressurized pipeline, it is subjected to water pressure both before and after the valve, and cannot obtain negative pressure in the pipeline, so it cannot naturally draw in air. There are no particularly effective engineering measures for cavitation erosion damage caused by conical valves used in pressurized pipelines. Therefore, conical valves are generally only used in projects with low head differences when used as flow control valves. At the same time, in order to reduce cavitation erosion damage caused by high-speed water flow inside the conical valve in a pressurized pipeline, some engineering measures have been taken, including:

[0010] (1) Adding energy dissipation devices such as fan blade rings, annular guide plates or nozzles to increase the energy dissipation rate of cone valves. After the water flow inside the valve passes through the fan blade rings and nozzles, it will form a counter-jet, which will reduce the flow velocity of the jet at the valve outlet and reduce the initial cavitation number of the valve. This measure has limited corrosion reduction effect and cannot fundamentally suppress cavitation.

[0011] (2) Improve the corrosion resistance of the wetted surface of the cone valve structure by using higher strength materials to reduce the adverse effects of cavitation damage. This measure uses a special coating, which is expensive, and long-term cavitation damage will still lead to erosion damage.

[0012] In view of the shortcomings of the gas-entraining corrosion reduction scheme for conical valves, the engineering field needs a natural ventilation measure to protect the conical valve core from cavitation damage. Summary of the Invention

[0013] The technical problem to be solved by the present invention is to provide a method and apparatus for natural gas entrainment to protect the valve core of a conical valve from cavitation damage.

[0014] A method for protecting the valve core of a cone valve from natural air ingress, comprising the following steps:

[0015] 1) Arrange an annular air-entraining sill at an appropriate position on the flow surface of the valve core of the conical valve body;

[0016] 2) Aeration holes are evenly distributed adjacent to the downstream of the aeration sill;

[0017] 3) The dimensions of the air-entraining sill are set according to the pipe diameter;

[0018] 4) The air mixing hole, together with the air mixing pipes at each stage, finally extends to the outside of the valve and connects with the atmosphere through a main air mixing pipe.

[0019] Natural aeration is achieved by utilizing the negative pressure zone downstream of the aeration sill and the atmospheric pressure difference. The aerated water flow effectively covers the valve core flow surface, thus reducing corrosion.

[0020] The appropriate position of the flow surface in step 1) above refers to: simulating the flow field inside the conical valve, obtaining the position of the contraction flow through the flow field simulation when the valve is fully open, and the starting position of the valve core air-entraining sill is located at the beginning of the contraction flow; since the entire valve body is centrally symmetrical, the air-entraining sill is arranged circumferentially around the longitudinal axis of the conical valve core to achieve full coverage of the conical cavitation zone;

[0021] Step 2) above, "uniformly arranging air-entraining holes close to the downstream of the air-entraining sill" means that the distance between the air-entraining holes and the air-entraining sill does not exceed 1 times the height of the air-entraining sill.

[0022] Step 3) Design dimensions of the air-entraining sill: The length of the air-entraining sill is 1 / 4 to 1 / 6 of the valve diameter, and the height of the air-entraining sill is 1 / 10 of the length of the air-entraining sill. This ensures a stable cavity and satisfactory flow pattern behind the sill, reducing the impact of the air-entraining sill on the valve's flow capacity. Tests have verified that under this arrangement, the impact of the air-entraining sill on the valve's flow capacity is less than 10%.

[0023] A conical valve with a valve core protected by natural gas mixing includes the following parts:

[0024] An air-injection sill is installed on the valve core of the cone valve;

[0025] The length of the aforementioned air-injection sill is 1 / 4 to 1 / 6 of the nominal diameter of the valve;

[0026] The height of the aforementioned air-entraining sill is 1 / 10 of its length; under this arrangement, the air-entraining sill has less than 10% influence on the valve's flow capacity.

[0027] The aforementioned air-entraining chute is wedge-shaped in longitudinal section;

[0028] The longitudinal section of the aforementioned aeration sill has an inner curved surface of an equiangular spiral on the water-facing side and an outer curved surface of an equiangular spiral on the water-repelling side.

[0029] Aeration holes are evenly arranged downstream of the aeration sill, with the diameter of the aeration holes not exceeding 3 mm.

[0030] The air-injection port is connected inside the valve core and extends to the outside of the valve through a main air-injection pipe, communicating with the atmosphere.

[0031] Regarding the selection of the size of the aeration sill, under various operating conditions, a stable cavity and satisfactory flow state must be maintained behind the sill. Otherwise, separation-type cavitation will occur when high-speed water flows through the aeration sill, which will lead to human-caused damage. During the design, the sill height should be minimized as much as possible to reduce the additional impact of the jet on the valve core surface.

[0032] The decompression model test shows that after the air-infused water flow of the present invention enters the valve body, it can effectively cover the surface of the valve core, including the water-stopping position of the valve seat, and the valve vibration is significantly reduced.

[0033] The beneficial effects of this invention are as follows:

[0034] The advantages of this invention are: (1) It can effectively suppress cavitation damage at the valve core and valve seat water stop, protect the valve core and water stop device, and avoid damage to the valve core structure or leakage of the valve due to cavitation damage during use; (2) The air-injection pit is arranged in a ring and has a wide coverage area, which can effectively protect the valve core and valve seat water stop; (3) The air-injection pit can realize autonomous air injection, and the facility is simple and easy to maintain, which greatly reduces the cost and construction difficulty.

[0035] In addition, the device in this invention has the following advantages: 1) The annular ventilation measure is adopted, and the entire annular range of the valve body is protected. It has been found through experiments that even if the valve core floats due to the buoyancy of the air bubbles, the valve core bottom can still be protected because the air-injection branch pipes are densely and evenly distributed.

[0036] 2) Air is introduced at the beginning of the contraction flow. The air-infused water flows through the valve channel and is fully mixed. The bubbles are dispersed smaller and the buoyancy they experience is less obvious. The dispersed bubbles are mixed more evenly and better surround the cavitation bubbles, absorbing the energy of the cavitation bubbles collapsing.

[0037] The anti-cavitation design of cone valves has always been a challenge, as it directly relates to the safe operation of engineering projects. This invention has a simple structure, reliable operation, greatly saves engineering investment, improves engineering safety, and has excellent application prospects. Attached Figure Description

[0038] Figure 1 This is a schematic longitudinal section of the cone valve of the present invention;

[0039] Figure 2 This is a partially enlarged cross-sectional schematic diagram of the wedge-shaped arrangement of the gas-incorporating sill of the present invention;

[0040] Figure 3 This is a partially enlarged cross-sectional schematic diagram of the gas-entraining sill of the present invention, which is arranged in an equiangular spiral.

[0041] Figure 4 This is a schematic diagram comparing the cavitation noise intensity before and after the valve core of the present invention is injected with gas.

[0042] 21. Air-injection sill, 22. Air-injection hole, 23. Air-injection branch pipe, 24. Main air-injection pipe. Detailed Implementation

[0043] Example 1

[0044] In order to use the conical valve as a flow control valve in a hydraulic ship lift, it needs to be protected. The specific methods are as follows:

[0045] A method for protecting the valve core of a cone valve from natural air ingress, comprising the following steps:

[0046] 1) Arrange an annular air-entraining sill at an appropriate position on the flow surface of the valve core of the conical valve body;

[0047] 2) Aeration holes are evenly distributed adjacent to the downstream of the aeration sill;

[0048] 3) The size of the air-entraining sill is related to the pipe diameter;

[0049] 4) The air mixing hole, together with the air mixing pipes at each stage, finally extends to the outside of the valve and connects with the atmosphere through a main air mixing pipe.

[0050] Natural aeration is achieved by utilizing the negative pressure zone downstream of the aeration sill and the atmospheric pressure difference. The aerated water flow effectively covers the valve core flow surface, thus reducing corrosion.

[0051] The appropriate position of the flow surface in step 1) above refers to: simulating the flow field inside the conical valve, obtaining the position of the contraction flow through the flow field simulation when the valve is fully open, and the starting position of the valve core air-entraining sill is located at the beginning of the contraction flow; since the entire valve body is centrally symmetrical, the air-entraining sill is arranged circumferentially around the longitudinal axis of the conical valve core to achieve full coverage of the conical cavitation zone;

[0052] Step 2) above, "uniformly arranging air-entraining holes adjacent to the downstream of the air-entraining sill" means that the distance between the air-entraining holes and the air-entraining sill does not exceed one time the height of the air-entraining sill.

[0053] Step 3) Design dimensions of the air-entraining sill: The length of the air-entraining sill is 1 / 4 to 1 / 6 of the valve diameter, and the height of the air-entraining sill is 1 / 10 of the length of the air-entraining sill. This ensures a stable cavity and satisfactory flow pattern behind the sill, reducing the impact of the air-entraining sill on the valve's flow capacity. Tests have verified that under this arrangement, the impact of the air-entraining sill on the valve's flow capacity is less than 10%.

[0054] Take the DN200 cone valve as an example.

[0055] An air-injection sill 21 is installed on the valve core of the fixed cone valve;

[0056] The length of the air-injection sill 21 is 1 / 5 of the nominal diameter of the valve, i.e., 40 mm;

[0057] The height of the air-entraining sill 21 is 1 / 10 of the length of the air-entraining sill, i.e., 4 mm; under this arrangement, the air-entraining sill 21 has less than 10% influence on the valve's flow capacity;

[0058] The aforementioned air-entraining chute 21 is wedge-shaped in longitudinal section;

[0059] Aeration holes 22 are evenly arranged downstream of the aeration sill 21. The diameter of the aeration holes is 2 mm and the spacing is 10 mm.

[0060] A circumferential air-injecting branch pipe 23 with a diameter of 10 mm is welded inside the cone body. The air-injecting branch pipe 23 is connected to the air-injecting branch hole 22. The air-injecting branch pipe 23 is connected to the air outside the valve through a main air-injecting pipe 24.

[0061] Example 2

[0062] Take the DN300 cone valve as an example.

[0063] An air-injection sill 21 is installed on the valve core of the fixed cone valve;

[0064] The length of the air-injecting sill 21 is 1 / 5 of the nominal diameter of the valve, i.e., 60 mm;

[0065] The height of the air-entraining sill 21 is 1 / 10 of the length of the air-entraining sill, i.e., 6 mm; under this arrangement, the air-entraining sill has less than 10% influence on the valve's flow capacity;

[0066] The upstream side of the longitudinal section of the aforementioned aeration sill 21 is an inner curved surface of an equiangular spiral, and the downstream side is an outer curved surface of an equiangular spiral.

[0067] The equation of an equiangular spiral is: r = ae bθ The range of values ​​for the water-facing side a is [10, 15], and b = 1; the range of values ​​for the water-repelling side a is [0.1, 5], and b = 1.

[0068] Aeration holes 22 are evenly arranged downstream of the aeration sill 21. The diameter of the aeration holes is 1.5 mm and the spacing is 10 mm.

[0069] A circumferential air-infusing branch pipe 23 with a diameter of 10 mm is welded inside the cone. The air-infusing branch pipe 23 is connected to the air-infusing hole 22. The air-infusing branch pipe 23 is connected to the external air of the valve through a main air-infusing pipe 24.

Claims

1. A method for protecting the valve core of a cone valve by natural air intake, comprising the following steps: 1) Arrange an annular air-entraining sill at an appropriate position on the flow surface of the valve core of the valve cone; 2) Air-injection holes are evenly distributed adjacent to the downstream side of the air-injection sill; 3) The dimensions of the air-entraining sill are set according to the pipe diameter; 4) The air mixing hole, together with the air mixing pipes at each stage, finally extends to the outside of the valve and connects with the atmosphere through a main air mixing pipe; Natural aeration is achieved by utilizing the negative pressure zone downstream of the aeration sill and the atmospheric pressure difference. The aerated water flow effectively covers the valve core flow surface, thus reducing corrosion. The appropriate position of the flow surface in step 1) above refers to: simulating the flow field inside the conical valve, obtaining the position of the contraction flow through the flow field simulation when the valve is fully open, and the starting position of the valve core air-entraining sill is located at the beginning of the contraction flow; Step 2) above, "uniformly arranging air-entraining holes adjacent to the downstream of the air-entraining sill" means that the distance between the air-entraining holes and the air-entraining sill does not exceed one time the height of the air-entraining sill. The design dimensions of the air-injection sill in step 3 above are as follows: the length of the air-injection sill is 1 / 4 to 1 / 6 of the valve diameter, and the height of the air-injection sill is 1 / 10 of the length of the air-injection sill.

2. A cone valve with a valve core protected by natural gas mixing, comprising the following parts: An air-injection sill is installed on the valve core of the cone valve; The length of the air-injection sill is 1 / 4 to 1 / 6 of the nominal diameter of the valve; The height of the air-entraining sill is 1 / 10 of its length; under this arrangement, the air-entraining sill has less than 10% influence on the valve's flow capacity. The gas-incorporating chute is wedge-shaped in longitudinal section; Evenly distribute air-injection holes downstream of the air-injection sill, with the diameter of the air-injection holes not exceeding 3 mm.

3. The conical valve with valve core protected by natural gas mixing according to claim 2, characterized in that: The longitudinal section of the aeration sill has an inner curved surface of an equiangular spiral on the water-facing side and an outer curved surface of an equiangular spiral on the water-repelling side. The air-injection port is connected inside the valve core and extends to the outside of the valve through a main air-injection pipe, communicating with the atmosphere.

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