RU2531072C1 - Controller of low liquid flow rates - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: proposed invention relates to the field of instrument making and may be used to set and maintain low liquid flow rates in technological processes of various industries. A controller of low liquid flow rates, including a body with inlet and outlet holes for liquid, a profiled needle with a stem for variation of the specified cross section. At the same time the profiled needle connected by a control stem with a control drive is made as capable of full closure of the central channel of the seat of the specified cross section, in parallel to the control stem in the body of the controller there is a fixed cartridge tightly, closed on top with a flexible membrane and having inside a movable stepped slide, supported at the bottom with a spring with a replaceable orifice. In the lower part of the cartridge there is a protruding edge for the slide support and a circular gap for liquid discharge from the controller via an output hole, besides, the output hole of the controller and the space above the seat of the setting cross section are hydraulically connected with a stabilising channel of small diameter at the outer side of the flexible membrane of the cartridge, and the central channel of the seat of the setting cross section is hydraulically tied by a bypass channel with the lower end part of the slide.

EFFECT: increased accuracy of control of low fluid flow rates.

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Description

The present invention relates to the field of instrumentation and can be used to install and maintain low liquid flow in technological processes of various industries.

To regulate and maintain constant fluid flow rates, a flow regulator / 1 / is known, comprising a housing with inlet and outlet channels connected through a control valve formed by a window-seat and an elastic plate located above it, one end of which is fixed to the housing, and the other, free, in contact with the support surface of the elastic element setting element. The supporting surface is made flat and is located at an angle relative to the window-saddle. For a more accurate implementation of the hyperbolic control law, it is envisaged that the supporting surface of the elastic element setting element is in the form of a parabolic profile. The flow regulator may include a clamp for the initial deflection of the elastic plate, made in the form of a clamping screw with an adjustable overhang, mounted in the middle part of the elastic plate, the free end of which, in turn, can be pressed against the supporting surface of the setting element by springs located on its both sides . In this version of the regulator, a loading scheme of an elastic plate with two moving support points, which are simultaneously the contact points of the plate with the throttling edges of the window-saddle and the supporting surface of the setting element, is used.

The disadvantage of this regulator is the design complexity and low reliability of the regulator.

Another analogue of the proposed flow controller is a hydraulic control device / 2 /, including a regulatory body made in the form of a bellows with a working chamber and a guide axis. One of the ends of the bellows is closed by a lid and connected to the body and the guide axis, in which a bypass channel is made, blocked by a control valve, and the other is a movable end, which is closed by a control valve with an axial hole for placement in it with an annular clearance of the guide axis with inclined grooves or flats. This makes the area of the annular gap variable as the control valve opens and interconnects it with the operation of the control valve by dosing the working fluid into the working chamber. The drive of the control valve is made in the form of a low-power manometric thermosystem with a thermal bulb equipped with an electric heating system. When the control valve is closed, the bore of the device is blocked by the movable end of the bellows, and when opened, its corresponding opening with a flow of the working fluid is skipped.

Significant disadvantages of the control device are the low accuracy of fluid flow control due to a violation of the linear dependence of the movement of the bellows end on external conditions (pressure and temperature), as well as the possibility of curvilinear deformation of the bellows with respect to its axis.

Closest to the claimed device is a flow controller / 3 /, comprising a housing with input and output channels, a spring-loaded step plunger with a throttling edge. A movable sleeve is placed on the sleeve with a diffuser, which regulates the main reference section for the passage of fluid, and a rod with a profiled needle is placed inside the sleeve, which forms an additional reference section. Both sides of the stepped plunger are connected by a bypass tube.

The flow rate through the regulator is set by the main setting section. With a change in the inlet or outlet pressure of the liquid, a constant pressure drop across the master sections is ensured, and therefore, a constant flow of liquid through the regulator.

The disadvantage of the considered fluid flow controller is the uncontrollability of the additional master section during operation of the device. A change in the position of the stepped plunger depending, for example, on the outlet pressure, will lead to a change in the value of both the throttling section and the position of the profiled needle in an additional reference section. To maintain a constant flow rate, it is necessary that the position of the profiled needle is set constant for a given flow rate.

The technical task of the proposed fluid flow controller is to increase the accuracy of regulation of small fluid flow rates.

The technical problem is solved in that in the known device comprising a housing with inlet and outlet openings for liquid, a profiled needle with a rod for changing the setting section, according to the invention, a profiled needle connected by an adjusting rod with a control drive is configured to completely overlap the central channel of the setting saddle sections parallel to the adjusting rod in the regulator body hermetically located stationary sleeve, closed on top with a flexible membrane and having a movable inside a stepped spool, supported by a spring with a replaceable washer from the bottom, a protruding edge for supporting the spool and an annular gap for fluid exit from the regulator through the outlet are made in the lower part of the sleeve, and the outlet of the regulator and the space above the saddle of the setting section are hydraulically connected by a small diameter stabilizing channel with the outer side of the flexible membrane of the sleeve, and the Central channel of the saddle of the master section is hydraulically connected bypass channel with the lower end of the spool.

In the drawings 1, 2, 3 and 4 shows a diagram of the regulator of small fluid flow. It consists of a housing 1 (Fig. 1), a control drive 2, a mounting support 3 of the housing, guides 4, a movable carriage 5, an adjusting rod 6 with a latch 7. In the housing 1 of the controller (Fig. 2), a sleeve 8 with an oil seal 9 is hermetically placed and a packing follower 10, a saddle 11, a cover 12. In addition, a sleeve 13 is sealed in the housing, overlapped by a flexible membrane 14 from above, a spool 15 included in the sleeve 13, a spring 16 supporting the spool 15 from the bottom and placed in the cover 17, as well as a plug eighteen.

In the housing 1, an inlet 19 and an outlet 20 for liquid are made, a channel 21 connecting the central channel of the seat 11 with the lower end part of the spool 15, a stabilizing channel 22 of small diameter, communicating the inlet 19 with the outer side of the membrane 14.

In the Central channel of the seat 11 (figure 3) includes a profiled needle 23 of the adjusting rod 6 with a small taper, passing into the cylindrical part. The cylindrical part of the needle is also configured to enter the channel of the seat 11 with a negligible gap, at which the fluid flow through the gap between the needle 23 and the channel of the seat 11 is completely stopped.

Between the spool 15 and the sleeve 13 from a level below the outlet 20 is made an annular gap 25 for the flow of fluid (figure 4). The spool 15 with the chamfer of its bottom end rests on the inwardly protruding edge of the sleeve 13, forming a height-varying annular gap through which the liquid passes to the outlet 20. The cross-sectional area cut off by the chamfer of the bottom end of the spool strictly corresponds to the area of the upper section of the spool. The width of this gap is automatically adjusted depending on the pressure difference in the gap between the profiled needle 23 and the seat 11, the spring force of the spring 16, supporting the spool 15 from below. The adjusting washer 26 is located under the spring. The gap between the needle 23 and the channel of the seat 11 forms a regulating section of the regulator for fluid flow.

The work of the regulator is as follows.

The required liquid flow rate to the consumer through the regulator is set by changing the position of the stem 6 using the actuator 2. The flow rate is monitored using a flow meter (not shown in the drawings) installed either on the line supplying liquid to the inlet 19 or on the line leading to the outlet 20 regulators.

The regulating movement of the rod 6 allows you to change the position of the needle 23 in the channel of the seat 11 and the width of the resulting set section for the fluid flow. When the fluid flows through this section, a certain pressure drop ΔP ₁ = P ₁ -P _{2 is formed} (where P ₁ is the pressure before the fluid enters the section; P ₂ is the pressure at the outlet of it). The pressure P ₁ through the channel 22 will be transmitted through the flexible membrane 14 to the upper end of the spool 15, and the pressure P ₂ through the channel 21 will be transmitted to the lower end of the spool 15. Thus, the force F ₁ = ΔP ₁ ∗ S (where S - the area of the ends of the spool), directed from top to bottom. At the same time, the elastic force F _{2 of the} spring 16 will act on the spool 15 from below. In accordance with the balance of these forces (F ₁ and F ₂ ), the spool 15 will occupy a strictly defined position, opening the corresponding gap between the lower end of the spool and the protrusion of the sleeve 13 (FIG. .4) for the fluid to flow through the gap 25 to the outlet 20. In this case, a pressure drop ΔP ₂ = P ₂ -P _out (where P _out is the pressure in the outlet 20) is formed on both sides of the opening slit.

Thus, the flow rate through the regulator for the same spring and the thickness of the washer 26 will be determined only by the position of the needle 23 in the channel of the seat 11, i.e. the defining cross section between them or the pressure drop ΔP ₁ . The ranges of fluid flow rates for the same spring are regulated by the thickness of the washer 26, the installation of which changes the elastic force of the spring 16 acting on the spool 15.

The constancy of the established, thus, low liquid flow through the regulator is ensured as follows. For example, there was a decrease in the external pressure P _o in the outlet 20. A decrease in the value of P _o should also lead to a decrease in pressure P ₂ at the entrance to the slot between the spool 15 and the protrusion of the sleeve 13. But at the same time, the pressure P will continue to act on the upper end of the spool ₁ . The increase in pressure drop ΔP ₁ will lead to the movement of the spool 15 by a certain amount down and a decrease in the height of the slit. This, in turn, will lead to the restoration of pressure P ₂ to the initial value. Thus, the pressure drop ΔP ₁ in the needle will instantly recover in the regulator despite the change in pressure drop ΔP ₂ . Keeping ΔР ₁ constant allows you to keep the flow rate through the regulator also constant.

In another case, the increase in the magnitude of the external P _o will be the opposite. The desire P _{2 to} increase will lead to the movement of the spool 15 up and lower P ₂ to the initial value. In this case, ΔP _{1 will} remain the same as the amount of fluid flow through the regulator.

Thus, a change in external factors will only lead to a change in the height of the gap between the spool 15 and the protrusion of the sleeve 13. The fluid flow through the regulator will be saved.

The small diameter of the channel 22 (0.5 ... 1.0 mm) allows you to dampen the pulsating nature of the movement of the fluid and the spool 15 and to stabilize the flow rate and pressure of the fluid.

The small taper of the needle 23 allows you to accurately control low fluid flow rates due to the fact that even for a small change in flow rate, a significant vertical movement of the adjusting rod 6 is required. The taper of the needle 23 for practical cases is about 0.4 deg. A smooth transition of the cone into the cylinder allows to reduce fluid flow from vanishingly small values to zero. Therefore, the proposed device allows you to adjust low fluid flow with high accuracy.

The presence of a flexible membrane 14 eliminates fluid leakage through the gap between the spool 15 and the sleeve 13 and significantly increase the accuracy of regulation of small fluid flow rates.

The technical and economic advantage of the proposed device is the high accuracy of regulation of small fluid flow rates. In addition, the device can be used as a dispenser for low liquid flow rates (chemicals, additives, diluents, etc.) in technological processes and apparatuses of various industries.

Literature

1. RF patent No. 2032927. Flow regulator (options). Claim 10.21.92. Publ. 04/10/95.

2. RF patent No. 2111140. Hydraulic control device. Claim 06/10/97. Publ. 05/27/99.

3. RF patent №2164034 C1. Flow regulator. Claim 08/10/1999. Publ. 03/10/2001.

Claims (1)

The regulator of low fluid flow rates, including a housing with inlet and outlet openings for liquid, a profiled needle with a rod for changing the setting section, characterized in that the profiled needle connected by the adjusting rod to the control drive is configured to completely overlap the central channel of the saddle of the setting section, in parallel the adjusting rod in the regulator body is hermetically sealed stationary sleeve, closed on top with a flexible membrane and having a movable stepped spool inside, supported by a spring with a removable washer from the bottom, a protruding edge for supporting the slide valve and an annular gap for fluid exit from the regulator through the outlet are made in the lower part of the sleeve, the outlet of the regulator and the space above the reference section saddle are hydraulically connected by a small diameter stabilizing channel to the outer side of the flexible membrane sleeves, and the central channel of the saddle of the master section is hydraulically connected by the bypass channel with the lower end part of the spool.

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