阅读说明：本技术 能实现大可调比和高调节精度的阀芯结构及调节阀和方法 (Valve core structure capable of realizing large adjustable ratio and high adjustment precision, adjusting valve and method ) 是由 钱锦远 徐毅翔 罗宇轩 仇畅 金志江 于 2021-08-25 设计创作，主要内容包括：本发明公开了一种能实现大可调比和高调节精度的阀芯结构及调节阀和方法。其中,阀芯由阀杆、外套筒、阀塞、内套筒和套筒调整杆组成。阀杆与阀塞直接相连,控制阀塞的上下运动；外套筒为空心圆筒状,其壁上设有第一节流窗口,沿圆周方向均布；阀塞外壁与内套筒内壁紧密贴合,同时能保证阀塞的自由上下运动；内套筒为空心圆筒状,其外壁与外套筒的内壁紧密贴合,同时能保证内套筒的自由旋转运动,其壁上设有第二节流窗口,沿圆周方向均布；套筒调整杆与内套筒直接连接,控制内套筒的旋转运动。本发明大幅增加了调节阀可调比,同时又实现了调节阀的高调节精度。(The invention discloses a valve core structure capable of realizing a large adjustable ratio and high adjustment precision, an adjusting valve and a method. Wherein, the valve core comprises valve rod, outer sleeve, valve plug, inner sleeve and sleeve adjusting lever. The valve rod is directly connected with the valve plug to control the valve plug to move up and down; the outer sleeve is hollow and cylindrical, the wall of the outer sleeve is provided with first throttling windows which are uniformly distributed along the circumferential direction; the outer wall of the valve plug is tightly attached to the inner wall of the inner sleeve, and the free up-and-down movement of the valve plug can be ensured; the inner sleeve is in a hollow cylindrical shape, the outer wall of the inner sleeve is tightly attached to the inner wall of the outer sleeve, free rotary motion of the inner sleeve can be guaranteed, and second throttling windows are arranged on the wall of the inner sleeve and are uniformly distributed in the circumferential direction; the sleeve adjusting rod is directly connected with the inner sleeve to control the rotation of the inner sleeve. The invention greatly increases the adjustable ratio of the adjusting valve and simultaneously realizes high adjusting precision of the adjusting valve.)

1. A valve core structure capable of realizing large adjustable ratio and high adjustment precision is characterized by comprising a valve rod (1), an outer sleeve (2), a valve plug (3), an inner sleeve (4) and a sleeve adjusting rod (5); the outer sleeve (2) is of a hollow cylindrical structure, and the wall of the outer sleeve is uniformly provided with through first throttling windows along the circumferential direction; the inner sleeve (4) is a hollow cylindrical structure coaxially sleeved in the outer sleeve (2), and the outer wall of the inner sleeve is sealed with the inner wall of the outer sleeve (2); the lower part of the inner sleeve (4) is externally connected with a sleeve adjusting rod (5), the inner sleeve (4) can be controlled to freely rotate by taking the axis as a rotating shaft through the sleeve adjusting rod (5), and the inner sleeve (4) and the outer sleeve (2) jointly form a revolute pair; the wall of the inner sleeve (4) is uniformly provided with through second throttling windows along the circumferential direction, and the shape, the number, the distribution angle and the distribution height of the second throttling windows are the same as those of the first throttling windows; by rotating the inner sleeve (4), the coincidence degree theta of the first throttling window and the second throttling window can be changed from 0 to 1; the valve plug (3) is coaxially sleeved in the inner sleeve (4), the outer wall of the valve plug is sealed with the inner wall of the inner sleeve (4), and the second throttling window can be completely sealed by the valve plug (3); the external valve rod (1) of upper portion of valve plug (3), can control valve plug (3) through valve rod (1) and realize reciprocating along inner skleeve (4).

2. The valve core structure capable of realizing large adjustable ratio and high adjustment precision according to claim 1, characterized in that the valve rod (1) is externally connected with an actuating mechanism capable of controlling the valve rod to move up and down, and the valve rod (1) is marked with scales capable of reading the movement stroke of the valve rod along the axial direction; the sleeve adjusting rod (5) is externally connected with an actuating mechanism which can control the sleeve adjusting rod to rotate.

3. The valve core structure capable of realizing large adjustable ratio and high adjustment precision according to claim 1, characterized in that the movement stroke of the valve plug (3) is slightly larger than the height of the first and second throttling windows.

4. The valve core structure capable of realizing a large adjustment ratio and high adjustment accuracy according to claim 1, wherein the width of the first throttling window is smaller than the distance between two adjacent first throttling windows.

5. The valve core structure capable of realizing large adjustable ratio and high adjustment precision according to claim 1, wherein the first throttling window and the second throttling window are both rectangular openings and are respectively arranged at the lower part of the sleeve.

6. The valve core structure capable of realizing a large adjustment ratio and high adjustment accuracy according to claim 1, wherein an angle dial (5-1) with a pointer (5-2) is provided on a portion of the sleeve adjusting lever (5) protruding outside the adjusting valve; the dial surface of the angle dial (5-1) is vertical to the axis of the sleeve adjusting rod (5) and is used for indicating the rotating angle of the inner sleeve (4).

7. A regulating valve with a valve core structure as defined in any one of claims 1 to 6, characterized in that the valve rod (1) and the sleeve adjusting rod (5) both partially extend out of the valve body, and the joints of the valve rod (1) and the sleeve adjusting rod (5) and the valve body are closed.

8. A method for achieving a large turndown ratio and a high turndown accuracy using the regulating valve of claim 7, characterized in that the following are specified:

s1: obtaining valve flow coefficients corresponding to different theta values and eta values through an experimental method or a computational fluid mechanics method; wherein the value theta is the contact ratio of the first throttling window and the second throttling window, and the value theta is more than or equal to 1 and more than or equal to 0; the eta value is the opening formed by the valve plug (3) and the first throttling window and the second throttling window, and eta is more than or equal to 1 and more than or equal to 0;

s2: on the basis of the data obtained in step S1, let η be x, θ be y, and the valve flow coefficient be z, to obtain a spatial flow characteristic surface xyz;

s3: obtaining the point with the minimum slope in the curve corresponding to the flow coefficient value of each valve by utilizing the space flow characteristic curved surface, and obtaining an optimal space flow characteristic curve after extracting and fitting all the points with the minimum slope;

s4: and obtaining the optimal theta value and eta value corresponding to the flow coefficient value of each valve through the optimal space flow characteristic curve to obtain the optimal regulation change mode of the regulating valve, thereby realizing the large adjustable ratio and high regulation precision of the regulating valve.

9. The method for achieving large adjustable ratio and high adjustment accuracy according to claim 8, wherein the experimental method of the step S1 is specifically as follows:

adjusting a valve rod (1) and a sleeve adjusting rod (5) to enable a first throttling window and a second throttling window to be mutually staggered and completely closed, so that a valve plug (3) is positioned at the bottom of the second throttling window, and the valve is in a closed state at the moment; introducing a target medium into the regulating valve, and regulating the valve rod (1) and the sleeve regulating rod (5) simultaneously to enable the valve plug (3) to move upwards and the inner sleeve (4) to rotate; in the movement process of the valve plug (3) and the inner sleeve (4), the movement stroke of the valve plug (3) and the rotation angle of the inner sleeve (4) are recorded, and valve flow coefficients corresponding to different theta values and eta values are obtained through measurement and calculation.

10. The method for achieving large turndown ratio and high turndown accuracy as claimed in claim 8, wherein said computational fluid dynamics method of step S1 is specifically as follows:

establishing a three-dimensional model of the regulating valve; in the initial state of the three-dimensional model, the first throttling window and the second throttling window have a small overlap ratio, and the valve plug (3) is slightly higher than the bottom of the second throttling window; then extracting an internal flow channel of the three-dimensional model, and carrying out grid division on the three-dimensional model; and by adopting a dynamic grid technology, the valve plug (3) and the inner sleeve (4) respectively and independently move according to a set motion function to obtain valve flow coefficients corresponding to different theta values and eta values.

Technical Field

The invention belongs to the field of valve structure design, and particularly relates to a valve core structure capable of realizing a large adjustable ratio and high adjustment precision, an adjusting valve and a method.

Background

The valve core is one of key control components in the valve, and realizes the adjustment and control of parameters such as flow, pressure and the like of flowing media in a pipeline system by changing the flowing direction and the flowing cross section area of the media. The traditional valve core structure is limited by the structural form and the shape of the through-flow section, the flow characteristic of the valve cannot meet the design requirement of large adjustable ratio, and the ratio of the maximum flow to the minimum flow which can be controlled by the existing valve is mostly below 100; in addition, because the traditional valve core structure is easily influenced by pressure fluctuation, the outlet flow of the valve can be unstable, namely, high regulation precision is difficult to realize. With the continuous emergence of complex working conditions such as high temperature, high pressure, ultra supercritical and the like and integration technology, the demand for valves with large adjustable ratios in process industry and hydraulic transmission systems is more urgent. Therefore, a combined valve core principle model is constructed, the research on the large adjustable ratio and the high adjustment precision of the valve core structure is carried out, a new idea is provided for the design of the valve core under extreme working conditions such as high temperature and high pressure, ultra supercritical, large flow, high pressure difference and the like, the combined valve core principle model becomes an important leading-edge problem of the current valve core design research, and the combined valve core principle model is also an important basic research related to the independent innovation of future high-end equipment.

Therefore, it is desirable to provide a valve core structure, a regulating valve and a method capable of realizing a large regulating ratio and high regulating precision.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a valve core structure, a regulating valve and a method, which can realize large regulating ratio and high regulating precision. The invention greatly increases the adjustable ratio of the adjusting valve and simultaneously realizes high adjusting precision of the adjusting valve.

The invention adopts the following specific technical scheme:

in a first aspect, the invention provides a combined valve core structure capable of realizing a large adjustable ratio and high adjustment precision, which comprises a valve rod, an outer sleeve, a valve plug, an inner sleeve and a sleeve adjusting rod; the outer sleeve is of a hollow cylindrical structure, and the wall of the outer sleeve is uniformly provided with through first throttling windows along the circumferential direction; the inner sleeve is a hollow cylindrical structure coaxially sleeved in the outer sleeve, and the outer wall of the inner sleeve is sealed with the inner wall of the outer sleeve; the lower part of the inner sleeve is externally connected with a sleeve adjusting rod, the inner sleeve can be controlled to freely rotate by taking the axis as a rotating shaft through the sleeve adjusting rod, and the inner sleeve and the outer sleeve jointly form a rotating pair; the inner sleeve wall is uniformly provided with through second throttling windows along the circumferential direction, and the shape, the number, the distribution angle and the distribution height of the second throttling windows are the same as those of the first throttling windows; by rotating the inner sleeve, the overlap ratio theta of the first throttling window and the second throttling window can be changed from 0 to 1; the valve plug is coaxially sleeved in the inner sleeve, the outer wall of the valve plug is sealed with the inner wall of the inner sleeve, and the valve plug can completely seal the second throttling window; the external valve rod in upper portion of valve plug can control the valve plug through the valve rod and realize reciprocating along the inner skleeve.

Preferably, the valve rod is externally connected with an actuating mechanism capable of controlling the valve rod to move up and down, and scales capable of reading the movement stroke of the valve rod are marked on the valve rod along the axial direction; the sleeve adjusting rod is externally connected with an actuating mechanism which can control the sleeve adjusting rod to rotate.

Preferably, the movement stroke of the valve plug is slightly larger than the height of the first throttling window and the second throttling window.

Preferably, the width of the first throttling window is smaller than the distance between two adjacent first throttling windows.

Preferably, the first throttling window and the second throttling window are both rectangular openings and are respectively arranged at the lower part of the sleeve.

Preferably, an angle dial with a pointer is arranged on the part of the sleeve adjusting rod extending out of the adjusting valve; the dial face of the angle dial is perpendicular to the axis of the sleeve adjusting rod and used for indicating the rotating angle of the inner sleeve.

In a second aspect, the invention provides a regulating valve with the combined valve core structure of any one of the first aspects, wherein the valve rod and the sleeve adjusting rod both partially extend out of the valve body, and the joints of the valve rod and the sleeve adjusting rod and the valve body are closed.

In a third aspect, the present invention provides a method for implementing a large adjustable ratio and high adjustment accuracy by using the adjusting valve of the second aspect, specifically as follows:

s1: obtaining valve flow coefficients corresponding to different theta values and eta values through an experimental method or a computational fluid mechanics method; wherein the value theta is the contact ratio of the first throttling window and the second throttling window, and the value theta is more than or equal to 1 and more than or equal to 0; the eta value is the opening formed by the valve plug and the first throttling window and the second throttling window, and eta is more than or equal to 1 and more than or equal to 0;

s2: on the basis of the data obtained in step S1, let η be x, θ be y, and the valve flow coefficient be z, to obtain a spatial flow characteristic surface xyz;

s3: obtaining the point with the minimum slope in the curve corresponding to the flow coefficient value of each valve by utilizing the space flow characteristic curved surface, and obtaining an optimal space flow characteristic curve after extracting and fitting all the points with the minimum slope;

s4: and obtaining the optimal theta value and eta value corresponding to the flow coefficient value of each valve through the optimal space flow characteristic curve to obtain the optimal regulation change mode of the regulating valve, thereby realizing the large adjustable ratio and high regulation precision of the regulating valve.

Preferably, the experimental method of step S1 is specifically as follows:

adjusting the valve rod and the sleeve adjusting rod to enable the first throttling window and the second throttling window to be mutually staggered and completely closed, so that the valve plug is positioned at the bottom of the second throttling window, and the valve is in a closed state at the moment; introducing a target medium into the regulating valve, and regulating the valve rod and the sleeve regulating rod simultaneously to enable the valve plug to move upwards and the inner sleeve to rotate; in the movement process of the valve plug and the inner sleeve, the movement stroke of the valve plug and the rotation angle of the inner sleeve are recorded, and the valve flow coefficients corresponding to different theta values and eta values are obtained through measurement and calculation.

Preferably, the computational fluid dynamics method of step S1 is specifically as follows:

establishing a three-dimensional model of the regulating valve; in the initial state of the three-dimensional model, a first throttling window and a second throttling window have a small overlap ratio, and the valve plug is slightly higher than the bottom of the second throttling window; then extracting an internal flow channel of the three-dimensional model, and carrying out grid division on the three-dimensional model; and by adopting a dynamic grid technology, the valve plug and the inner sleeve respectively and independently move according to a set movement function to obtain valve flow coefficients corresponding to different theta values and eta values.

Compared with the prior art, the invention has the following beneficial effects:

1) the invention realizes the design concept of large adjustable ratio and high adjustment precision of the adjusting valve by providing the flow characteristic curved surface and space flow characteristic curve concepts, and provides a new idea for designing the valve core under extreme working conditions of high temperature and high pressure, ultra supercritical, large flow, high pressure difference and the like.

2) Because the adjustable ratio refers to the ratio of the maximum flow and the minimum flow which can be adjusted, the adjustable minimum flow of the adjusting valve can be further reduced so as to increase the adjustable ratio. The principle of further reducing the minimum flow is that the flow coefficient changes more stably under the working condition of small opening degree (the corresponding description is that the point with the minimum curvature on the curve is selected), that is, the flow change is small under the working condition of small flow rate, so that the regulating precision of the regulating valve is improved under the working condition of small opening degree, and the adjustable minimum flow rate value is reduced. When the opening degree is small, the change of the flow coefficient corresponding to the curvature minimum point is minimum, the adjustable minimum flow value of the regulating valve can be reduced due to the small change of the flow coefficient, and the whole adjustable ratio is increased after the adjustable minimum flow value is reduced.

3) The invention can realize high-precision adjustment of the adjusting valve, because the required flow characteristic curve can be automatically extracted by the method, and the more stable the change of the flow characteristic curve is (reflected on the point of taking the minimum slope), the higher the adjustment precision of the adjusting valve is.

Drawings

FIG. 1 is a schematic view (a) and a front cross-sectional view (b) of a valve cartridge configuration;

FIG. 2 is a schematic view of a sleeve adjuster rod;

FIG. 3 is a schematic front cross-sectional view of the regulator valve;

FIG. 4 is an exemplary graph of a flow characterizing surface;

FIG. 5 is a diagram illustrating an exemplary process for extracting an optimal spatial flow profile from a flow profile;

the reference numbers in the figures are: 1. a valve stem; 2. an outer sleeve; 3. a valve plug; 4. an inner sleeve; 5. a sleeve adjusting rod; 5-1, angle dial scale; 5-2, a pointer.

Detailed Description

The invention will be further elucidated and described with reference to the drawings and the detailed description. The technical features of the embodiments of the present invention can be combined correspondingly without mutual conflict.

As shown in fig. 1, the present invention provides a valve core structure capable of achieving a large adjustable ratio and high adjustment accuracy, and the valve core structure mainly includes a valve rod 1, an outer sleeve 2, a valve plug 3, an inner sleeve 4, and a sleeve adjusting rod 5. The valve plug 3, the inner sleeve 4 and the outer sleeve 2 are sequentially coaxially sleeved from inside to outside, the adjacent joints between the two are tightly attached to realize sealing, and the adjacent parts can freely move. The outer sleeve 2 is a hollow cylindrical structure, a plurality of through first throttling windows are formed in the side wall of the outer sleeve, and all the first throttling windows are uniformly distributed along the side wall of the outer sleeve 2. In practice, the first throttling windows may be arranged in a rectangular opening structure, and all the first throttling windows are located at the lower part of the side wall of the outer sleeve 2.

The inner sleeve 4 is coaxially sleeved inside the outer sleeve 2 and is also of a hollow cylindrical structure. The lower part of the inner sleeve 4 is connected with a sleeve adjusting rod 5, and the inner sleeve 4 can be controlled to rotate freely by the sleeve adjusting rod 5 by taking the axis as a rotating shaft. The outer sleeve is fixed, the inner sleeve can rotate around the axis, and the inner sleeve 4 and the outer sleeve 2 jointly form a revolute pair. In practice, a radial connection may be provided at the bottom of the inner sleeve 4, through which the sleeve adjustment rod 5 is subsequently connected, so that the sleeve adjustment rod 5 is arranged coaxially with the inner sleeve 4. A plurality of through second throttling windows are formed in the side wall of the inner sleeve 4, and all the second throttling windows are uniformly distributed along the side wall of the outer sleeve 2. The shape, number, distribution angle and distribution height of the second throttle windows should be set to be the same as those of the first throttle windows so that the variation of the degree of overlap theta of the first throttle windows and the second throttle windows from 0 to 1 is achieved by rotating the inner sleeve 4. That is, when the inner sleeve rotates, the first throttling windows and the second throttling windows are distributed in a staggered manner to form an overlapping region, the overlapping region can allow a target medium entering the regulating valve to pass through, and the ratio of the area of the overlapping region to the area of the maximum overlapping region (namely, the area of the first throttling window or the area of the second throttling window) is recorded as the window overlapping degree θ. Therefore, in practical applications, the second throttling windows may also be provided in a rectangular opening structure, and all the second throttling windows are located at the lower part of the side wall of the inner sleeve 4.

The rotating movement of the inner sleeve is controlled by a sleeve adjusting rod, as shown in fig. 2, an angle dial and a pointer are arranged at the bottom of the sleeve adjusting rod, the dial surface of the angle dial 5-1 is perpendicular to the axis of the sleeve adjusting rod 5 and used for indicating the rotating angle of the inner sleeve 4 through the pointer 5-2, and the window contact ratio theta can be calculated through the rotating angle.

The valve plug 3 is coaxially sleeved in the inner part of the inner sleeve 4, the outer wall of the valve plug is sealed with the inner wall of the inner sleeve 4, and the valve plug 3 can completely seal the second throttling window, so that the closing state of the whole valve is realized. The external valve rod 1 of upper portion of valve plug 3 can control valve plug 3 through valve rod 1 and realize reciprocating along inner skleeve 4.

In practical application, the valve rod 1 can be externally connected with an actuating mechanism capable of controlling the valve rod to move up and down, and scales capable of reading the movement stroke of the valve rod 1 are marked along the axial direction. The sleeve adjusting rod 5 is externally connected with an actuating mechanism which can control the sleeve adjusting rod to rotate. The movement stroke of the valve plug 3 should be slightly larger than the height of the first and second throttle windows so that the maximum adjustment of the opening degree can be achieved. The width of the first throttling window (second throttling window) should be smaller than the distance between two adjacent first throttling windows (second throttling windows), so that the window overlapping ratio can cover any value within 0-1.

That is, the valve plug contacts the inner wall of the inner sleeve and is driven by the valve rod to move in the vertical direction. The rotation of the inner sleeve controls the width of the throttle window overlapping area circumferentially, while the vertical movement of the valve plug controls the height of the throttle window overlapping area. The ratio of the valve plug movement height to the valve plug movement maximum height (namely the height of the rectangular throttling window) is recorded as a valve plug opening eta, scales are marked on the valve rod, the movement height of the valve plug can be read, and the valve plug opening eta can be calculated through the height value. Therefore, the flow area of the combined valve core is determined by the motion height of the valve plug and the rotation angle of the inner sleeve, and the motion height of the valve plug and the rotation angle of the inner sleeve can be represented by the valve plug opening eta and the window coincidence degree theta.

As shown in fig. 3, the regulator valve has the above-described valve body structure. Wherein, the upper part of the valve rod 1 extends out of the valve body so as to control the up-and-down movement of the valve plug through the valve rod 1 outside the valve body; the lower part of the sleeve adjustment rod 5 protrudes out of the valve body so that the rotational movement of the inner sleeve is controlled outside the valve body by the sleeve adjustment rod 5. The joints of the valve rod 1 and the sleeve adjusting rod 5 with the valve body are in a closed state, so that when the adjusting valve is used, a target medium introduced into the valve flows out from the joints to cause valve leakage.

The method for realizing the large adjustable ratio and the high adjusting precision by utilizing the adjusting valve comprises the following specific steps:

s1: firstly, valve flow coefficients corresponding to different theta values and eta values are obtained through an experimental method or a computational fluid mechanics method. Wherein the value theta is the contact ratio of the first throttling window and the second throttling window, and 1 is more than or equal to theta and more than or equal to 0. The eta value is the opening formed by the valve plug 3 and the first throttling window and the second throttling window, and eta is more than or equal to 1 and more than or equal to 0.

The experimental method comprises the following specific steps:

the valve rod 1 and the sleeve adjusting rod 5 are adjusted to enable the first throttling window and the second throttling window to be completely staggered to achieve sealing, the valve plug 3 is located at the bottom of the second throttling window, and the valve is in a closed state at the moment. Then, the target medium is introduced into the regulating valve, and the valve rod 1 and the sleeve adjusting rod 5 are simultaneously regulated, so that the valve plug 3 moves upwards, and the inner sleeve 4 rotates. In the movement process of the valve plug 3 and the inner sleeve 4, the movement stroke of the valve plug 3 and the rotation angle of the inner sleeve 4 are recorded, and the valve flow coefficients corresponding to different theta values and eta values are obtained through measurement and calculation.

The computational fluid dynamics method is specifically as follows:

and establishing a three-dimensional model of the regulating valve. In the initial state of the three-dimensional model, a certain tiny overlap ratio is ensured to exist between the first throttling window and the second throttling window, and the valve plug 3 is slightly higher than the bottom of the second throttling window. And then extracting an internal flow channel of the three-dimensional model, and carrying out meshing on the three-dimensional model. And by adopting a dynamic grid technology, the valve plug 3 and the inner sleeve 4 respectively and independently move according to a set motion function to obtain valve flow coefficients corresponding to different theta values and eta values.

S2: based on the data obtained in step S1, the data is subjected to data processing, i.e., η is x, θ is y, the valve flow coefficient value is z, and a spatial flow characteristic curved surface xyz is drawn as shown in fig. 4.

S3: the obtained space flow characteristic curve is utilized to obtain the point with the minimum slope in the curve corresponding to the flow coefficient value of each valve, and after all the points with the minimum slope are extracted and fitted, the optimal space flow characteristic curve with the generally lower slope is obtained, as shown in fig. 5.

S4: and obtaining the optimal theta value and eta value corresponding to the flow coefficient value of each valve through the obtained optimal space flow characteristic curve, and obtaining the molded line coordination change mode of the rectangular throttling window of the valve core. Because the adjustable ratio refers to the ratio of the maximum flow and the minimum flow which can be adjusted, the adjustable minimum flow of the adjusting valve can be further reduced so as to increase the adjustable ratio. The principle of further reducing the minimum flow is that the flow coefficient changes more stably under the working condition of small opening degree (the corresponding description is that the point with the minimum curvature on the curve is selected), that is, the flow change is small under the working condition of small flow rate, so that the regulating precision of the regulating valve is improved under the working condition of small opening degree, and the adjustable minimum flow rate value is reduced. When the opening degree is small, the change of the flow coefficient corresponding to the curvature minimum point is minimum, the adjustable minimum flow value of the regulating valve can be reduced due to the small change of the flow coefficient, and the whole adjustable ratio is increased after the adjustable minimum flow value is reduced. Therefore, a large adjustment ratio and a high adjustment accuracy of the adjustment valve can be achieved by the above method.

The above-described embodiments are merely preferred embodiments of the present invention, which should not be construed as limiting the invention. Various changes and modifications may be made by one of ordinary skill in the pertinent art without departing from the spirit and scope of the present invention. Therefore, the technical scheme obtained by adopting the mode of equivalent replacement or equivalent transformation is within the protection scope of the invention.