Flow cell with constant flow in pressure fluctuation environment

Abstract

The invention relates to the technical field of water quality monitoring, and discloses a flow cell with constant flow in a pressure fluctuation environment, the flow cell comprises an inlet, an outlet, a flow control chamber and an instrument detection chamber arranged on the upper part of the flow control chamber, the flow control chamber comprises a first flow control chamber and a second flow control chamber; the first flow control chamber is connected with the inlet, the second flow control chamber is communicated with the instrument detection chamber, and the outlet is formed in the instrument detection chamber; a valve is arranged between the first flow control chamber and the second flow control chamber, and the valve can change the opening degree through rotation so as to adjust the pressure difference between the first flow control chamber and the second flow control chamber, so that the instrument detection chamber becomes a constant flow velocity area. The flow can be kept constant when the pressure fluctuates by adjusting the valve.

Description

Technical Field

[0001] The invention relates to the technical field of water quality monitoring, and in particular to a flow cell with a constant flow rate in a pressure fluctuation environment. Background Art

[0002] At present, in many areas, secondary water supply pump rooms and drinking water sources in residential areas are required to install multi-parameter water quality monitoring instruments to ensure the water quality and ensure the drinking water safety of residents.

[0003] The main indicators for monitoring water quality parameters include: turbidity, residual chlorine, conductivity, pH, total phosphorus, total nitrogen and other parameters. Among them, pH and residual chlorine indicators are the most critical indicators, because the residual chlorine content in tap water is considered safe between 0.3 mg / L and 2 mg / L. At present, the online detection methods of residual chlorine and total chlorine are mostly based on electrochemical methods. Among them, the online residual chlorine sensor with three-electrode method has the highest measurement accuracy, which can reach 0.01 mg / L measurement accuracy (range 0-10 mg / L), and the stability is also good. However, when the electrode residual chlorine sensor is working, the water in the circulation pool needs to maintain a relatively constant flow rate, and the flow rate is controlled at about 30L / h. The change of flow rate will have a great impact on the measurement accuracy. This is the key reason why many residual chlorine measuring instruments are inaccurate (when the water flow is stationary, the electrochemical reaction will gradually consume the chloride ions, causing the measurement value to continue to decline). Water supply pressure fluctuations often occur in secondary water supply pump rooms due to pipe network reasons, sudden increase or decrease in user load, etc. The minimum inlet pressure is 0.2 bar / 2.9 psi and the maximum is 6 bar / 87 psi. Ordinary flow cells will cause flow rate fluctuations due to water pressure fluctuations, which will have a great impact on the accuracy of multi-parameter water quality detection. At present, most domestic instruments use simple flow cells, which do not have the function of constant flow control under pipe network pressure fluctuations. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a flow cell with a constant flow rate under a pressure fluctuation environment, which can maintain a constant flow rate when the pressure fluctuates by adjusting a valve.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A flow cell with a constant flow rate under a pressure fluctuation environment comprises an inlet, an outlet, a flow control chamber and an instrument detection chamber arranged on the upper part of the flow control chamber, wherein the flow control chamber comprises a first flow control chamber and a second flow control chamber, wherein the first flow control chamber is connected to the inlet, the second flow control chamber is connected to the instrument detection chamber, and the outlet is arranged in the instrument detection chamber; a valve is arranged between the first flow control chamber and the second flow control chamber, wherein the valve can rotate and its opening can be changed by rotation to adjust the pressure difference between the first flow control chamber and the second flow control chamber, thereby making the instrument detection chamber a constant flow rate zone.

[0007] Furthermore, the valve includes a baffle, a rotating shaft and a torsion spring, the rotating shaft is vertically arranged at the bottom of the circulation pool, one end of the torsion spring is connected to the rotating shaft, and the baffle is connected to the rotating shaft. The baffle is in a left limit position under the pre-pressure of the torsion spring, and when there is a pressure difference between the first flow control chamber and the second flow control chamber, the baffle can rotate rightward with the rotating shaft as the central axis under the combined force of the pressure difference and the torsion spring; the baffle is in a "7" shape, and the short side of the "7" shape is an arc shape matched with the wall of the circulation pool, a baffle hole is provided in the vertical direction of the baffle, a groove is provided on the wall of the circulation pool corresponding to the rotation travel area of ​​the baffle, and a curved groove is also provided on the groove, a throttling orifice is formed between the curved groove and the baffle hole, and the position of the baffle hole is changed by the rotation movement of the baffle, thereby realizing the size adjustment of the throttling orifice.

[0008] Furthermore, the valve also includes a central chamber, which is vertically arranged, with a side wall at one end connected to the bottom of the circulation pool and the other end connected to the top of the flow control chamber, and the rotating shaft and the torsion spring are arranged in the central chamber; the long side end of the "7"-shaped baffle is provided with a rib plate connected to the rotating shaft; a thin opening for the rib plate to pass through is provided at the side wall of the central chamber corresponding to the torsion spring above, and the baffle is connected to the rotating shaft through the rib plate; the central chamber is not connected to the first flow control chamber and the second flow control chamber; the other end of the torsion spring is connected to the side wall of the central chamber.

[0009] Furthermore, the central chamber is cylindrical, and the baffle is also provided with an arc-shaped groove, through which the baffle forms a dynamic seal with the circular side wall of the central chamber. The arc-shaped groove on the baffle and the circular side wall of the central chamber are required to have high machining accuracy, and the concentricity and machining error are not less than 0.01 mm, so as to form a good sliding seal and prevent the water in the circulation pool from entering the central chamber.

[0010] Furthermore, when the baffle rotates, the overlapping area between the curved groove and the baffle hole changes, thereby realizing automatic pressure difference adjustment of the throttle size. The specific adjustment method is as follows:

[0011] When the overlap area of ​​the curved groove and the baffle hole Deflection angle with baffle When the following functional relationship is satisfied, constant flow control can be achieved when the pressure difference changes;

[0012] ;

[0013] in, is a constant.

[0014] Furthermore, an upper bearing and a lower bearing are arranged in the central chamber, and the two ends of the rotating shaft are connected to the top of the flow control chamber and the bottom of the circulation pool through the upper bearing and the lower bearing respectively.

[0015] Furthermore, an upper bearing end cover and a lower bearing end cover are also provided in the central chamber, wherein the lower bearing end cover is provided at the upper portion of the lower bearing, and the upper bearing end cover is provided at the lower portion of the upper bearing.

[0016] Furthermore, the circulation pool of the present invention also includes a lower end cover, which is arranged at the lower part of the central chamber and is used to seal the central chamber and serve as an inspection port.

[0017] Furthermore, the instrument detection room is provided with a water quality detection probe for detecting water quality.

[0018] Compared with the prior art, the present invention provides a flow cell with a constant flow rate under a pressure fluctuation environment, which has the following beneficial effects:

[0019] (1) The present invention can maintain a constant flow rate when the pressure fluctuates by adjusting the valve.

[0020] (2) In order to solve the problem of pressure change when the circulation pool is connected to the pipeline network, the present invention adds a valve with automatically adjustable opening between the water inlet pipe and the working area of ​​the circulation pool. When the inlet pressure increases, the valve opening is automatically reduced, and vice versa, thereby eliminating the influence of pipeline network pressure fluctuations on the flow rate.

[0021] (3) In order to adapt to the cylindrical flow pool structure, the present invention innovatively proposes a throttling adjustment form of a circular torsion spring + a central rotating baffle, which makes the flow pool structure more compact. The valve opening adjustment degree changes with the rotation angle. A reverse throttling overlap curve is cleverly used to realize pressure negative feedback control, making the flow control closer to the theoretical curve. The manufacturing is also very simple and feasible. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the main structure of the automatic differential pressure constant flow flow cell in Example 1;

[0023] Figure 2 The cross-sectional structure of the automatic pressure difference constant flow flow cell in Example 1 is shown in FIG. Figure 1; Among them, the valve is adjusted to the left limit position (here P1 and P2 are the positions with the minimum pressure difference);

[0024] Figure 3 The cross-sectional structure of the automatic pressure difference constant flow flow cell in Example 1 is shown in FIG. Figure 2 ; The valve is adjusted to the right limit position (here P1 and P2 are the positions with the maximum pressure difference);

[0025] Figure 4 Schematic diagram of the ideal orifice throttling flow surface, where d1 and d2 represent the diameter of the orifice and the diameter of the water flow after passing through the orifice respectively;

[0026] Figure 5 It is a schematic diagram of the overlapping curve of the throttle port in Example 1;

[0027] Figure 6 This is a schematic diagram of the main cross-sectional structure of the central chamber in Example 1.

[0028] Figure 7 This is a schematic diagram of the top-down cross-sectional structure of the central chamber in Example 1.

[0029] Meaning of the reference numerals in the figures:

[0030] 0-water quality detection probe; 1, instrument detection room; 2, flow control room; 21-first flow control room; 22-second flow control room; 3-torsion spring; 4-baffle; 41-baffle hole, 42-opening; 5-side wall; 51-groove; 52-curved groove; 6-inlet; 7-outlet; 8-rotating shaft; 9-upper bearing; 10-upper bearing end cover; 11-lower bearing end cover; 12-lower end cover; 13-lower bearing; 14-flow pool bottom; 15-throttling overlap area; 16-center chamber. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Example 1

[0033] like Figures 1 to 7 As shown, this embodiment proposes an automatic pressure difference constant flow regulating flow cell, which has the ability to keep the flow constant when the inlet and outlet pressures fluctuate. The specific structure is as follows:

[0034] The circulation pool is divided into two parts, the upper part is the instrument detection chamber 1, and the lower part is the flow control chamber 2.

[0035] The lower flow control chamber 2 is composed of two areas, the first flow control chamber 21 and the second flow control chamber 22, wherein the first flow control chamber 21 is connected to the inlet 6, and the pressure is the water pipe inlet pressure P1, and the second flow control chamber 22 is connected to the upper instrument detection chamber 1, and the pressure is the same, which is P2. A valve is arranged between the first flow control chamber 21 and the second flow control chamber 22, and the valve includes a movable baffle 4, a rotating shaft 8, a torsion spring 3 and a central chamber 16, the rotating shaft 8 is vertically arranged at the bottom of the circulation pool, one end of the torsion spring 3 is connected to the rotating shaft 8, and the baffle 4 is connected to the rotating shaft 8, and the baffle 4 can rotate with the rotating shaft 8 as the central axis (the rotation angle range is 0℃~θ℃); the baffle 4 is a "7" shape, and the short side of the "7" shape is an arc shape matched with the wall of the circulation pool, and a baffle hole 41 is provided in the vertical direction of the baffle 4, and the baffle hole 4 is a rectangular vertical bar hole. A groove 51 is provided on the side wall 5 corresponding to the rotation travel area of ​​the circulation pool and the baffle 4, and a curved groove 52 is provided in the circumferential direction of the groove 51. When the baffle 4 rotates, the overlapping area between the curved groove 52 and the baffle hole 41 changes, so a throttle opening is formed between the curved groove 52 and the baffle hole 41. The rotational movement of the baffle 4 drives the position of the baffle hole 41 to change, thereby realizing the size adjustment of the throttle opening.

[0036] The central chamber 16 is arranged vertically, and the side wall at one end is connected to the bottom of the circulation pool, and the other end is connected to the top of the flow control chamber 2. The rotating shaft 8 and the torsion spring 3 are arranged in the central chamber 16; the long side end of the "7"-shaped baffle 4 is provided with a rib plate connected to the rotating shaft 8; an arc-shaped opening 42 for the rib plate to pass through is provided at the side wall of the central chamber 16 corresponding to the torsion spring 3 above the torsion spring 3, and the baffle 4 is connected to the rotating shaft 8 through the rib plate; the central chamber 16 is not connected to the first flow control chamber 21 and the second flow control chamber 22; the other end of the torsion spring 3 is connected to the side wall of the central chamber 16.

[0037] An upper bearing 9, a lower bearing 13, an upper bearing end cover 10, a lower bearing end cover 11 and a lower end cover 12 are arranged in the central chamber 16. The two ends of the rotating shaft 8 are respectively connected to the top of the flow control chamber 2 and the bottom of the circulation pool through the upper bearing 9 and the lower bearing 13; the lower bearing end cover 11 is arranged on the upper part of the lower bearing 13, and the upper bearing end cover 10 is arranged on the lower part of the upper bearing 9; the lower end cover 12 is arranged at the lower part of the central chamber 16, which is used to seal the central chamber 16 and serve as an inspection port; the instrument detection chamber 1 is provided with a water quality detection probe 0 for detecting water quality.

[0038] The specific working principle of the above throttle port is described as follows:

[0039] According to the fluid Bernoulli equation flow equation, when the fluid flows through the interface, the fluid parameters will change due to the sudden change of the flow surface, causing turbulence and loss of part of the fluid's mechanical energy, which is called local resistance loss. In fluid mechanics, according to the ideal state of the fluid Bernoulli equation, we can get:

[0040] (1)

[0041] in, is the water inlet pressure, is the average flow velocity at the water inlet, is the flow surface pressure, is the average flow velocity on the flow surface, is the inlet water surface height, is the outlet water surface height, is the density of the fluid, is a constant.

[0042] Generally, the water pipe network is a horizontal pipe, so In the present invention, since the size of the flow cell is not large, the height difference between the inlet and outlet is negligible, and the ideal small hole throttling flow surface is as follows Figure 4 As shown ( Figure 4 ), so the Bernoulli equation can be expressed as:

[0043] (2)

[0044] After finishing, we can get:

[0045] (3)

[0046] Since the energy loss caused by local resistance is ignored when deriving formulas (2) and (3), the energy loss caused by the fluid passing through the orifice plate in real conditions needs to be taken into account. In order to correct the influence of these factors, a correction parameter is introduced , then the flow The equation is:

[0047] (4)

[0048] The flow surface of the self-operated flow control valve is a curved hole with a small gap. It can be approximated to 0, so the flow equation of the throttle port of the present invention is:

[0049] (5)

[0050] Wherein, Q is the volume of the fluid flowing through the throttle; k is a parameter related to the fluid and the flow surface, which is a known quantity in the present invention; A is the flow surface area; Δp is the pressure difference before and after the throttle.

[0051] According to the derived formula, when the throttle opening is constant, k is a constant value. If the self-operated flow control valve is to ensure the dynamic constant of the output flow, it is necessary to ensure The value of the valve is kept constant. This requires that the flow surface area changes accordingly with the pressure difference before and after the valve. When the pressure difference decreases, the flow surface area increases; when the pressure difference increases, the flow surface area decreases. In the present invention, a torsion spring system is introduced into the self-powered flow control flow cell as an adjusting element for changing the size of the flow surface.

[0052] To maintain The value is constant, and the working principle of the device we designed is as follows:

[0053] The average pressure of the first flow control chamber 21 on the baffle 4 The size of is shown as follows:

[0054] (6)

[0055] The average pressure of the second flow control chamber 22 on the baffle 4 The size of is shown as follows: (7)

[0056] One end of the torsion spring 3 is connected to the rotating shaft, and the other end is connected to the side wall of the central chamber. The torsion spring 3 has a certain preload force. When it starts working, the torsion spring 3 drives the rotating shaft 8 to drive the baffle to rotate, which satisfies the torque balance relationship:

[0057] (8)

[0058] Wherein, S is the cross-sectional area of ​​the baffle 4, is the outer radius of the baffle 4, is the inner radius of the baffle 4, is the height of baffle 4, is the liquid pressure in the first flow control chamber 21, is the liquid pressure in the second flow control chamber 22, is the pressure of the liquid in the first flow control chamber 21 on the baffle 4, is the pressure of the liquid in the second flow control chamber 22 on the baffle 4, - the deflection angle of the baffle 4, —Torque coefficient of torsion spring 3.

[0059] Right now:

[0060] (9)

[0061] Therefore, only the overlap area of ​​the curved groove 52 on the side wall of the flow cell and the baffle hole 41 is required. With deflection angle Satisfies the functional relationship:

[0062] (10)

[0063] in, is a constant.

[0064] From the previous analysis, we can get: When the pressure increases, the baffle is pushed to the right by the pressure difference, and the angle becomes larger, query the throttle overlap curve (curve equation of the curve slot) see formula (10, the throttle overlap curve is the throttle overlap area 15), the flow cross-sectional area decreases. On the contrary, when When the pressure decreases, the baffle 4 is pushed to rotate to the left by the pressure difference, and the flow cross-sectional area increases. In this way, it can be ensured that the pressure change automatically adjusts the size of the throttle to ensure a constant flow rate.

[0065] Compared with the common pipeline vertical self-acting flow valve, the present invention has a simpler and more compact structure, does not require a diaphragm structure, and is more suitable for a cylindrical flow pool structure. A reverse throttling overlap curve is cleverly used to achieve pressure negative feedback control.

[0066] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0067] While the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that many changes, modifications, substitutions and variations can be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. A flow cell with a constant flow rate under a pressure fluctuation environment, characterized in that: It includes an inlet, an outlet, a flow control chamber and an instrument detection chamber arranged on the upper part of the flow control chamber, the flow control chamber includes a first flow control chamber and a second flow control chamber, the first flow control chamber is connected to the inlet, the second flow control chamber is connected to the instrument detection chamber, and the outlet is arranged in the instrument detection chamber; a valve is arranged between the first flow control chamber and the second flow control chamber, and the valve can change its opening by rotation to adjust the pressure difference between the first flow control chamber and the second flow control chamber, so that the instrument detection chamber becomes a constant flow rate area.

2. The flow cell with a constant flow rate under a pressure fluctuation environment according to claim 1, characterized in that: The valve includes a baffle, a rotating shaft and a torsion spring, wherein the rotating shaft is vertically arranged at the bottom of the circulation pool, one end of the torsion spring is connected to the rotating shaft, and the baffle is connected to the rotating shaft, and the baffle can rotate around the rotating shaft as the central axis; the baffle is in the shape of a "7", and the short side of the "7" shape is an arc shape matched with the wall of the circulation pool, a baffle hole is provided in the vertical direction of the baffle, a groove is provided on the wall of the circulation pool corresponding to the rotation stroke area of ​​the baffle, and a curved groove is also provided on the groove, a throttling orifice is formed between the curved groove and the baffle hole, and the position of the baffle hole is changed by the rotation movement of the baffle, thereby realizing the size adjustment of the throttling orifice.

3. The flow cell with a constant flow rate under a pressure fluctuation environment according to claim 2, characterized in that: The valve also includes a central chamber, which is vertically arranged, with a side wall at one end connected to the bottom of the circulation pool and the other end connected to the top of the flow control chamber, and the rotating shaft and the torsion spring are arranged in the central chamber; a rib plate connected to the rotating shaft is arranged at the long side end of the "7"-shaped baffle; an opening for the rib plate to pass through is arranged at the side wall of the central chamber corresponding to the torsion spring above, and the baffle is connected to the rotating shaft through the rib plate; the central chamber is not connected to the first flow control chamber and the second flow control chamber; the other end of the torsion spring is connected to the side wall of the central chamber.

4. The flow cell with a constant flow rate under a pressure fluctuation environment according to claim 2, characterized in that: When the baffle rotates, the overlapping area between the curved groove and the baffle hole changes, thereby adjusting the size of the throttle. The specific adjustment method is as follows: When the overlap area of ​​the curved groove and the baffle hole Deflection angle with baffle When the following functional relationship is satisfied, constant flow control can be achieved when the pressure difference changes; ； in, is a constant.

5. The flow cell with a constant flow rate under a pressure fluctuation environment according to claim 2, characterized in that: An upper bearing and a lower bearing are arranged in the central chamber, and two ends of the rotating shaft are connected to the top of the flow control chamber and the bottom of the circulation pool through the upper bearing and the lower bearing respectively.

6. The flow cell with a constant flow rate under a pressure fluctuation environment according to claim 5, characterized in that: An upper bearing end cover and a lower bearing end cover are also provided in the central chamber. The lower bearing end cover is provided at the upper portion of the lower bearing, and the upper bearing end cover is provided at the lower portion of the upper bearing.

7. The flow cell with a constant flow rate under a pressure fluctuation environment according to claim 6, characterized in that: It also includes a lower end cover, which is arranged at the lower part of the central chamber and is used to seal the central chamber and serve as an inspection port.

8. The flow cell with a constant flow rate under a pressure fluctuation environment according to claim 1, characterized in that: The instrument detection room is provided with a water quality detection probe for detecting water quality.

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