RU2502957C2 - Level-flow meter for liquid in tank - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: level-flow meter for liquid in a tank comprises a body, a differential pressure sensor, a pneumatically hydraulic unit comprising a tight cavity, a tube with a through channel for its vertical submersion onto the tank bottom with controlled liquid by one end, and with the other end connected with one of the inlets of the differential pressure sensor, tight elastic elements. Besides, the tight elastic elements are made in the form of membrane boxes, some sides of which, in particular, one side, is made as elastic, and others, accordingly, rigid. The flow-lever meter in the tank additionally comprises a flow converter into pressure, the second differential pressure sensor with two inlets connected to the indicator and a unit of liquid level variation compensation with a compensating channel. Besides, the flow converter into pressure comprises a chamber, which in its turn consists of two compartments - receiving one and the one separated from it with a separating membrane of the outlet compartment. The outlet compartment is connected with a through hydraulic channel made in the form of a small diameter tube to one of two inlets of the second differential pressure sensor.

EFFECT: simultaneous measurement of level and flow of different liquids in tanks of transport facilities designed for operation under especially heavy road and climate conditions with temperature variations in a wide range and under low temperatures.

9 cl, 3 dwg

Description

The invention relates to a control and measuring technique, and in particular to devices for measuring the level and flow rate of various liquids, for example, fuel in the tanks of vehicles, in particular in all-terrain vehicles of fuel carriers and snow and swamp vehicles, designed to work in especially difficult weather conditions with temperature changes wide range up to 100 ° C and at especially low temperatures up to -70 ° C.

The use of such devices is most effective when it is required to measure the level and flow rate in a large number of tanks in compliance with the requirements of high reliability and accuracy. For example, in two-link fuel carriers, up to twelve fuel tanks can be installed. In each of them, the measurement of the fuel level is mandatory, and the flow rate is desirable. To measure these two; parameters, separate independent devices are used - level meters and flow meters, respectively, the number of these devices will be quite large. As a result, 24 separate measuring devices will have to be installed on such a fuel carrier. A large number of measuring devices reduces reliability, complicates operation and increases cost. At the same time, the feature of such vehicles is the increased requirements for the reliability of equipment, especially fuel equipment - increased explosion and fire safety in difficult road climatic conditions, while maintaining high accuracy and sensitivity. The proposed flowmeter meets these requirements.

If the level changes during the flow of fluid under the tank cover above the controlled fluid, a vacuum can be generated. This happens when the throttle openings in the tank cap are clogged, for example, icy, dirty or structurally absent. The latter has (1 place in cases where the liquid is in several tanks communicating with each other or when the tanks have an internal pressing shell. In addition, even with throttle openings, with a rapid change in the liquid level - at a high flow rate, the pressure under the tank cover will not equal to atmospheric.In this case, the measurement of level and flow rate using known devices will contain a large error.This also happens in tanks that do not communicate with the environment, i.e. in a sealed volume. ktam may include tanks of aircraft and spacecraft (aircraft, missiles), submarines and tanks, in which the pair of the pumped liquid must not enter the environment due to environmental hazards, explosion-fire.

A known device for measuring flow [RF patent No. 2362123. Flow meter G01F 1/34. Publ. July 20, 2009], comprising a housing consisting of two halves, and including a supply nozzle and a nozzle directing the measured medium stream into a receiving hole made in the housing, a membrane with a positive buoyancy body, dividing the housing chamber filled with the measured medium into two cavities - the submembrane and submembrane communicating with the vacuum cavity between the nozzles, the output pipe and the differential-transformer transducer moving the membrane into an output signal, characterized in that up to a filling chamber, divided by a membrane with a second body of positive buoyancy into two cavities, a submembrane and a submembrane, filled with a test medium - water, alcohol, ether or another test liquid with a known density equal to the density of one of the components of a two-component measured medium, the chamber chambers are separated by a partition and a membrane, the submembrane cavity of the additional chamber is connected by a channel containing the membrane to the rarefaction cavity between the nozzles into the channels connecting the submembrane cavities of the housing chambers and a rarefaction cavity between the nozzles, two sealing elements are introduced, the channels being combined with two differential transformer transducers for moving the membranes of cameras with moving cores, the transducers are connected to an analog-to-digital system that is connected to a single-chip microcontroller.

In addition, a magnetically conductive solid body or non-wettable magnetic fluid placed in the connecting channels is used as the cores of the differential transformer of displacement transducers.

In addition, the sealing elements are made in the form of pistons rigidly fixed to bodies of positive buoyancy.

The known device has the following disadvantages.

1. The inability to measure simultaneously with the flow rate of the liquid from the tank and the level of this liquid in the tank.

2. Large measurement errors arising for the following reasons:

- due to changes in the pressure of the vapor-air atmosphere under the tank cap arising from a change in the volume of liquid in the tank when it is evacuated when the throttle openings in the tank cap are clogged, for example, icy, dirty or absent, and since this pressure affects the flow measurement results, then this leads to an increase in error;

- due to changes in the pressure of the liquid column when it is evacuated from the tank and, accordingly, changes in the liquid level, and since this pressure also affects the flow measurement results, this leads to an increase in the error;

- during the movement of the vehicle over rough terrain, variable dynamic loads are created - a "chatter", which are perceived as changes in the liquid level in the tank, which leads to large dynamic errors in determining the flow rate.

A device for measuring the liquid level in a tank is known [RF patent No. 2301971. A method of measuring the liquid level in a tank and a device for its implementation. G01F 23/16. Publ. June 27, 2007], comprising a housing with a capacitive pressure sensor installed in a sealed cavity connected to a master oscillator connected through a frequency meter to a digital indicator. The measurement circuit of the device is equipped with a processor, the program of which is configured to track the shape of the internal cavity of the tank. The sealed cavity is divided by a capacitive pressure sensor into two - lower and upper sealed cavities. The lower membrane is located in the lower sealed cavity and is a measuring one. The device is also equipped with a tube connected to the lower sealed cavity with a through channel for vertical immersion of it on the bottom of the tank with a controlled fluid. The upper membrane of the capacitive sensor is located in the upper sealed cavity. The sealed cavity of the sensor is equipped with a tube with a through channel (hole) for connection with the atmosphere. Both tubes are filled with 5-10 mm non-wetting liquid (for example, gel, mercury, etc.), which forms plugs. Columns of non-wetting liquid are closed from harmful fumes on both sides by any industrial oil, for example Nigrol, Tad, etc. An electrical circuit of measurements is located above the upper sealed cavity.

When measuring the liquid level in the tank under pressure, the device is equipped with an additional channel for installation in the gas array of the tank, which is also filled with 5-10 mm non-wetting liquid. The device is also equipped with a magnetic element for mounting the device in any selected position and place. The capacitive pressure sensor has a cylindrical shape with flexible round membranes.

The internal cavity of the pressure sensor is connected by a channel to the atmosphere and is made with two communicating cavities separated by a fixed plate with a hole. The middle plate is shielded by outer membranes and is a rigid frame with a large thickness. When working in liquid media under pressure, the internal cavity of the sensor is connected by a channel to a gas cushion present in the measured tank.

The known device has the following disadvantages.

1. The inability to simultaneously measure the level and flow rate of the liquid from the tank.

2. The device cannot work at low temperatures (up to -70 ° C). Columns of non-wetting liquid are closed from harmful fumes on both sides with industrial oil, for example Nigrol, Tad, etc., which will thicken and clog the tubes at low temperatures. Due to the fact that the principle of operation of this device is based on the movement of liquid through the tube, with a through channel installed on the bottom of the tank with liquid, its blockage means loss of operability of the device.

3. In addition, with large changes in temperature, the physical properties of the liquid change, up to the precipitation of its components (paraffins, sulfur, etc.) and their deposition on parts of the measuring equipment. Condensation of water vapor from the air leads to the formation of ice crystals on the suction structures, especially located in the lower part of the tank (because water is heavier than fuel). The known design has a tube with a through channel for vertical immersion of it on the bottom of the tank. A column of controlled fluid rises through the tube. Therefore, during operation, dirt can accumulate in it, deposits from sulfur and paraffin compounds and other contaminants, including crystals of frozen water. At low temperatures, the deposition rate is significantly accelerated. Due to the fact that the principle of operation of this device is based on the movement of a controlled fluid (fuel) through a tube with a through channel, its clogging means a loss of operability of the device. Since this tube is actually a capillary with a small diameter, this can happen quite quickly. Cleaning the tube will be a daunting task, as it contains a multilayer column of various liquids - a water trap, consisting of a non-wetting dividing liquid, which is insulated from industrial oil on both sides. When cleaning the tube, you will have to replace the water seal, which is quite difficult, especially in the field.

A device is known for measuring the liquid level in a tank (positive decision on application 2009136291-28 (051247) dated 12/21/2010. Liquid level gauge in a tank. G01F 23/16. Publ. 10.042011), taken as a prototype, containing a differential housing a pressure sensor with two inputs connected to the indicator, a pneumohydraulic unit including a sealed cavity, a tube with a through channel for immersing it vertically on the bottom of the tank with a controlled liquid at one end and the other end connected to one of the inputs of the differential pressure sensor, the second input which is connected to one end of the tube with a through channel, the other end of which is brought into the vapor-air atmosphere under the tank cover, characterized in that the end of the tube with a through channel brought to the bottom of the tank and the end of the pipe brought into the steam-air atmosphere under the tank cover with appropriate sealed elastic elements, while forming the internal cavity of the corresponding pneumatic channel, isolated from the external environment.

Moreover, the sealed elastic elements are made in the form of membrane boxes, part of the sides of which or all, in particular one side, are elastic and the rest respectively rigid, while the elastic sides can be made in the form of stakes - membranes or flexible films or corrugated plates or elastic hollow ball.

In addition, a sealed elastic element placed inside the tank in the liquid is made in the recess at the bottom of the tank, for example in the drain neck.

In addition, a sealed elastic element placed inside the tank in the area of the vapor-air atmosphere is made inside the tank cover, which consists of an inlet flange attached to the tank and through screw connections through the seal with the neck and body, and to the body with screws through spring washers and gasket the plate is screwed, the pneumatic channel tubes through the nipples and connecting tubes are connected to the inputs of the differential pressure sensor, which is attached to the housing with a bolt with a washer and a spring washer, electrically Differential pressure sensor wires are connected to the power terminal "+" on-board network and the casing is connected to the "weight" bolt, the information signal is removed from the signal terminal.

In addition, a measuring tank was introduced, in which the pneumohydraulic block of the level gauge is located.

In addition, both sealed elastic elements are interconnected by a body made in the form of a damping cup, inside of which a sealed elastic element is installed, installed on the bottom of the tank with a controlled fluid, and the body contains a fixing axis coaxial with the damping cup connecting the sealed elastic elements, and the damping cup and the fixing axis of the housing coaxial with it are interconnected by stiffness disks.

In addition, the damping cup of the housing is cylindrical.

In addition, the damping cup consists of separate parts and movable couplings covering the joints of the individual parts, the number of parts being determined based on the ratio of the maximum height of the tank to the length of the individual part, the pneumatic channel tube has the form of an elastic spiral, the movable couplings have through holes in which the balls are located , on the outside, the balls are covered by elastic clamps, or in the form of elastic rings (spring washers), on the outside of the individual parts of the damping cup, located under the movable couplings, there are grooves located at a distance from each other equal to the minimum fixed position of the individual parts with respect to each other.

In addition, the lower separate part of the damping cup is connected to the upstream separate part of the damping cup using a threaded connection, the maximum length of the separate lower part in the extended state is not less than the minimum fixed position of the individual parts with respect to each other, dowels are installed above and below the sealed elastic element, throttle openings are made near the lower end of the damping cup, or throttle cutouts are directly at its end.

The disadvantages of the known device include the inability to measure simultaneously with the liquid level in the tank and the flow rate of this liquid from the tank, as well as low accuracy and sensitivity.

The main task solved by this invention is to measure simultaneously with the liquid level in the tank and its flow rate from the tank. Tasks to be solved also include ensuring high reliability of the device, including:

- explosion and fire safety, which is important when the controlled environment is explosive and fire hazardous liquids;

- metrological reliability of measuring the level (quantity) of fuel and its consumption when using the device on vehicles, for example, all-terrain vehicles, fuel carriers and fueling vehicles (snow and swamp vehicles) designed to operate in especially difficult climatic conditions when temperature changes over a wide range and at low temperatures up to -70 ° C.

The problems to be solved by this invention are also to ensure high accuracy and sensitivity of the device, reducing the dynamic measurement error, which occurs for the following reasons:

- due to changes in the pressure of the vapor-air atmosphere under the tank cap, and since this pressure affects the flow measurement results, a corresponding error will appear;

- at a flow rate of liquid from the tank, its level changes and, as a result, the pressure of the liquid column changes, which also leads to the appearance of the corresponding error;

- due to changes in fluid pressure, when the vehicle is moving over rough terrain and the resulting fluid vibrations in the tank, a corresponding error also occurs.

The solution to these problems is achieved by the fact that in the proposed liquid level meter, a tank containing a housing, a differential pressure sensor with two inputs connected to a liquid level indicator, a pneumohydraulic unit including a sealed cavity, a tube with a through channel for vertical immersion of it on the bottom of the tank with controlled by liquid at one end and the other end connected to one of the inputs of the differential pressure sensor, the second input of which is connected to one end of the second tube with a through channel , the other end of which is withdrawn into the vapor-air atmosphere under the tank cover, in addition, the end of the tube with a through channel brought out to the bottom of the tank and the end of the tube brought into the steam-air atmosphere under the tank cover are connected to the corresponding sealed elastic elements, forming an internal pneumatic cavity channels, isolated from the external environment, unlike the prototype, an additional flow-to-pressure converter, a second differential pressure sensor with two inputs, connected to the indicator a liquid ode and a liquid level change compensation unit with a compensating channel, the flow-to-pressure converter consisting of a chamber, which, in turn, consists of two compartments - a receiving compartment and an output compartment separated from it by a separation membrane, and the output compartment is connected through a channel made in the form of a tube of small diameter to one of the two inputs of the second differential pressure sensor.

In addition, in the liquid level meter-flowmeter in the tank in the unit for compensating for changes in the liquid level, the compensating channel is a discharge pipe at one end connected to a pipe coming from a sealed element located at the bottom of the tank with a controlled liquid, the second end of the discharge pipe is connected to one of the inputs of the second differential pressure sensor.

In addition, in the liquid level meter-flowmeter in the tank, the unit for compensating for changes in the liquid level is connected to the flow-to-pressure transducer, and the compensating channel is a tube withdrawn from the tank with controlled liquid, the second end of this tube being connected to the flow-to-pressure transducer between the additional membrane and a sealed outlet compartment, with an additional membrane separating the flow into pressure transducer into two halves, the first half is connected to the intake and flow nozzle si, the second half is connected to a through channel made in the form of a small-diameter tube connected to one of the two inputs of the second differential pressure sensor, in addition, the center of the additional membrane is connected by a rod to the center of the separation membrane of the sealed outlet compartment.

In addition, in the liquid level meter-flowmeter in the tank, a sealed element located at the bottom of the tank with a controlled liquid and connected to it through a channel made in the form of a tube of small diameter connected at the other end to the input of the first differential pressure sensor, as well as a second sealed element located in vapor-air atmosphere above the controlled liquid - under the tank cover and a through channel connected to it, made in the form of a tube connected to another input of the first differential pressure sensor I, filled with special non-freezing liquid, for example, silicone oil or antifreeze.

In addition, in the liquid flow meter in the tank, the output compartment of the flow to pressure transducer and the through channel made in the form of a small-diameter tube are filled with a special non-freezing liquid, for example, silicone oil or antifreeze.

In addition, in the liquid level meter, in the tank, in front of the first and second inlets of the first differential pressure sensor connected to the through channels, one of which goes to a sealed element located at the bottom of the tank with a controlled liquid, and the second to a sealed elastic element located in a vapor-air atmosphere above the controlled fluid - under the tank cap, there is an air bubble.

In addition, in the liquid level meter-flowmeter in the tank, the tube of the compensating channel diverted from the tube coming from the sealed element is filled with special non-freezing liquid, for example, silicone oil or antifreeze.

In addition, an air bubble is located in the liquid level meter in the tank in front of the inlet of the second differential pressure sensor connected to the second end of the compensating channel tube.

In addition, an air bubble is located in the liquid level gauge in the tank in front of the inlet of the second differential pressure sensor connected to the second end of the through channel, made in the form of a small diameter tube connected to the output compartment of the flow to pressure transducer.

The implementation in the device of an additional flow-to-pressure transducer, a second differential pressure transducer with two inputs, connected to a liquid flow indicator and a liquid level change compensation unit with a compensating channel, and the flow to pressure transducer consists of a chamber consisting, in turn, of two compartments - receiving and, separated from it by a separation membrane, output compartment, and the output compartment is connected through hydraulic channel, made in the form of a tube of small diameter to one mu of two inputs of a second differential pressure sensor can be measured simultaneously with the liquid level in the tank and its discharge from the tank.

High reliability of the device for explosion and fire safety and high metrological reliability of measuring the level (quantity) of fuel and its consumption when using the device on vehicles designed to work in especially severe road and climatic conditions when temperature changes in a wide range and at low temperatures up to -70 ° C is ensured due to the fact that the electrical parts of the level meter-flowmeter are placed outside the controlled fluid, the level and flow rate of which is measured, and the cavities and connecting e tube are sealed separate from the controlled liquid separation membranes.

Ensuring high reliability of the device when used on vehicles designed to move over rough terrain (all-terrain vehicles) and therefore working in conditions of increased shaking causing the controlled fluid to swing, which creates large dynamic loads on the device and high accuracy of the device, reducing the dynamic measurement error during changes the pressure of the vapor-air atmosphere under the tank cap and due to changes in the pressure of the liquid column during its flow and correspondingly The change in the liquid level, as well as due to changes in the fluid pressure when the vehicle is moving over rough terrain and the resulting fluid oscillations in the tank, is ensured by the fact that in the compensation unit for changing the fluid level, the compensating channel is a discharge tube from the tube going from the sealed cavity designed to be placed on the bottom of the tank with a controlled fluid, the second end of the outlet pipe is connected to one of the inputs of the second differential pressure sensor or by the fact that the unit for compensating for changes in the liquid level is connected to the flow to pressure transducer, and the compensating channel is a tube removed from the tank with controlled liquid, and the second end of this tube is connected to the flow to pressure transducer between the additional membrane and the sealed outlet compartment, and an additional membrane divides the flow into pressure transducer into two halves, the first half is connected to the intake and flow fittings, the second half is connected to through a channel made in the form of a small-diameter tube connected to one of the two inputs of the second differential pressure sensor, in addition, the center of the additional membrane is connected by a rod to the center of the separation membrane of the sealed outlet compartment.

High sensitivity of the device is ensured by the fact that the through channel, made in the form of a tube coming from an airtight cavity designed to be placed at the bottom of a tank with a controlled liquid, is filled with special non-freezing liquid, for example, silicone oil or antifreeze.

Thus, the essential features of the present invention allow the simultaneous measurement of the level (quantity) and flow rate of various liquids, for example, fuel in the tanks of vehicles, in particular in all-terrain vehicles of fuel carriers and snow and swamp vehicles, designed to operate in especially difficult climatic conditions when temperature changes in wide range and at low temperatures up to -70 ° C. In addition, the essential features of the present invention contribute to a lesser dependence of the operation of the level meter on the environment and operating conditions, increase the reliability of the device when temperature changes in a wide range and at low temperatures to -70 ° C, explosion and fire safety, including metrological reliability.

The invention is illustrated by drawings, which show the following materials:

figure 1 shows the functional diagram of the developed level gauge-liquid flow meter in the tank;

figure 2 shows the unit for compensating for changes in fuel level connected to the Converter flow to pressure;

figure 3 is a drawing of the developed level gauge-liquid flow meter in the tank.

The liquid level meter in the tank according to the functional diagram of FIG. 1 contains a pneumohydraulic unit 1 located in the tank 2. The maximum level of filling the tank 2 with liquid is H. The current level is h _x . In the tank 2 above the liquid there is a space 3 filled with a vapor-air atmosphere. The developed liquid level-flow meter in the tank also contains an electronic unit 4 located outside the tank 2, for example, in the instrument compartment 5 of the snow and swamp path or in an airtight unit near the tank 2 — outside the explosion and fire hazard zone. The electronic unit 4 consists of two differential pressure sensors of the first 6 and second 7, respectively, including pressure transducers 8 and 9 each with two inputs for pneumatic or hydraulic pressure signals - "Input-1" and "Input-2" and analog-to-digital converters ( ADC) 10 and 11. Pressure transducers 8 and 9 can be based on inductive, capacitive, semiconductor operating principles, be a strain gauge (for example, a pneumatic pressure sensor MPX5010DP CASE 867С-05 or a hydraulic pressure sensor ST005PG1SPCF from HONEYWELL []) or and other principle of action. Differential pressure sensors 6 and 7 are connected respectively to the liquid level indicator 12 and to the liquid flow indicator 13 located on the dashboard 14 of the snow and swamp path or, if equipped with a snow and swamp path, to the on-board computer 15, or to the on-board information and control system (BIUS). To connect to a computer, the pressure sensors 6 and 7 include ADCs 10 and 11.

Pneumohydraulic unit 1 consists of two parts. The first part 16 is located in the liquid. It consists of a sealed element 17, which may be one or more interconnected membrane boxes. The membrane box part of the parties, in particular one side (separation membrane) 18, is flexible, and the rest, respectively, rigid. Flexible sides can be made in the form of inserts - membranes, flexible films, corrugated plates, hollow ball, etc.

The sealed element 17 is connected through a pneumatic, hydraulic or pneumohydraulic channel made in the form of a tube 19 of small diameter to the input "Input-2" of the first differential pressure sensor 6. This channel transmits pressure proportional to the liquid level in the tank 2 to the differential pressure sensor 6, respectively, through a column of air or a special fluid filling the tube 19 and the sealed element 17.

If a pneumatic pressure sensor is used as a differential pressure sensor 6, the channel is pneumatic, the tube 19 and the sealed element 17 are filled with air. In this case, the flexible side of the sealed element 17 is elastic, the air will be supplied to the inlet ("Inlet-2") through the tube 19.

If a hydraulic pressure sensor is used as a differential pressure sensor 6, the channel is hydraulic, the tube 19 and the sealed element 17 are filled with a special liquid, for example, silicone oil or some kind of antifreeze. In this case, the flexible side of the sealed element 17 is in the form of a non-elastic flexible film ("flaccid membrane"), and a special liquid will be supplied to the inlet ("Input-2"). This design has higher accuracy and sensitivity, but hydraulic pressure transmitters are much more expensive.

The advantages of pneumatic (low cost) and hydraulic methods (high accuracy and sensitivity) can be obtained by using a combined - pneumohydraulic channel. In this case, the tube 19 and the sealed element 17 are filled with a special liquid, for example, silicone oil or some kind of antifreeze (as in the hydraulic method), but there is an air bubble in front of the “Input-2” differential pressure sensor 6.

The second part 20 of the pneumohydraulic unit 1 is located in the vapor-air atmosphere 3 above the liquid (under the tank cover). It consists of a second sealed elastic element 21, similar to a sealed elastic element 17. The sealed elastic element 21 is connected through a channel-tube 22 to the input "Input-1" of the first differential pressure sensor 6. The through channel, made in the form of a tube 22, can be made as well as the tube 19 pneumatic, hydraulic or pneumohydraulic.

The construction of the second part 20 of the pneumohydraulic unit 1 contains a mounting unit for the cover of the tank 2. For level gauges with a large measuring range (H> 0.3-10.5 m and more), to increase the rigidity of the structure, the sealed elastic elements 17 and 21 are interconnected by a housing. The housing is made in the form of a damping cup 23. The pneumohydraulic unit 1 is placed inside the damping cup 23. To increase the rigidity, the sealed elastic elements 17 and 21 are interconnected by a fixing axis 24 connecting the centers of both sealed elastic elements and passing coaxially inside the damping cup 23. 23 is leaky and is filled with a controlled fluid.

In the lower part of the tank 2 there is an intake nozzle 25, and in the upper part of the tank there is a filler neck 26. A converter 27 of the liquid flow to pressure is connected to the intake nozzle 25. The liquid consumed from the tank 2 is discharged from the transducer 27 of the fluid to pressure c through the supply nozzle 28. When using the fittings, a special boss with an internal thread is welded to the tank 2 for connection with the fitting (Fig. 3). In addition to the fitting connection, a flange connection can be used (FIG. 2).

The liquid flow to pressure transducer 27 consists of a chamber consisting of two compartments — a receiving 29 and a sealed outlet compartment 31 separated from it by a separation membrane 30. The compartment 31 is made similar to a sealed elastic element 17 and may comprise one or more interconnected membrane boxes. The membrane box part of the parties, in particular one side (separation membrane) 30, is flexible, and the rest, respectively, rigid. Flexible sides can be made in the form of inserts - membranes, flexible films, corrugated plates, hollow ball, etc.

The hermetic outlet compartment 31 is connected through a pneumatic, hydraulic or pneumohydraulic channel made in the form of a small diameter tube 32 to the input "Input-2" of the second differential pressure sensor 7. This channel transmits pressure proportional to the flow rate of the liquid from the tank 2 to the differential pressure sensor 7, respectively, through a column of air or a special liquid filling the tube 32 and the sealed outlet compartment 31.

If a pneumatic pressure sensor is used as a differential pressure sensor 7, the channel is pneumatic, the tube 32 and the sealed outlet compartment 31 are filled with air. In this case, the flexible side of the sealed outlet compartment 31 is elastic, air will be supplied to the input "Input-2" of the differential pressure sensor 7 through the tube 34.

If a hydraulic pressure sensor is used as a differential pressure sensor 7, the channel is hydraulic, the tube 32 and the sealed outlet compartment 31 are filled with a special liquid, for example, silicone oil or some kind of antifreeze. In this case, the flexible side of the sealed outlet compartment 31 is in the form of a non-elastic flexible film (“flaccid membrane”), and liquid will be supplied to the input “Input-2” of the differential pressure sensor 7. This design has higher accuracy and sensitivity, but hydraulic pressure transmitters are much more expensive.

The advantages of pneumatic (low cost) and hydraulic methods (high accuracy and sensitivity) can be obtained by using a combined - pneumohydraulic channel. In this case, the tube 32 and the sealed outlet compartment 31 are filled with a special liquid, for example, silicone oil or some kind of antifreeze (as in the hydraulic method), but there is an air bubble in front of the “Inlet-2” input of the differential pressure sensor 7.

To improve the accuracy of measuring the flow rate at the input "Input-1" of the second differential pressure sensor 7, a compensation unit for changing the liquid level is connected. It can be made in the form of a compensating pneumatic, hydraulic or pneumohydraulic channel (similar to the channel with the tube 32) representing a tube 33 diverted from the tube 19 coming from the sealed element 17.

In addition, a fuel level change compensation unit may be integrated in the pressure flow converter 27. In this case, the unit for compensating for changes in the liquid level is a compensating channel in the form of a tube 34 (Fig. 2), withdrawn from the tank 2, for example, together with a suction fitting 25. The opposite end of the tube 34 is connected to the pressure flow transducer 27 between the additional membrane 35 and a sealed outlet compartment 31. The membrane 35 divides the Converter 27 flow to pressure in two halves. A consumable liquid passes through one half, and the second half transmits the pressure of the liquid for measurement using a differential pressure sensor 7. For this, the center of the additional membrane 35 is connected by a rod 36 to the center of the separation membrane 30 of the sealed outlet compartment 31.

Placing one sealed elastic element in a recess at the bottom of the tank, and the second sealed elastic element inside the tank cover, connecting them with a body in the form of a damping cup in FIG. not shown and carried out as in the prototype.

The developed level meter-liquid flow meter in the tank works as follows. A column of a controlled liquid with a height h _x - level, according to the functional diagram in figure 1, exerts a pressure P _nx on a sealed elastic element 17 located at the level of the bottom of the tank 2. In addition to the pressure of a liquid column, a pressure equal to the pressure P _{ax of the} vapor-air atmosphere acts above the controlled fluid in the space 3 inside the tank 2 - under its cover. The total pressure P _Σ on the sealed elastic element 17 is equal to

$$P_{\Sigma }=P_{nx}+P_{ax}.\left(\mathrm{one}\right)$$

The level measurement is based on determining the pressure of the liquid column P _hx exerted on the sealed elastic element 17. This pressure depends on the level of the controlled liquid and its relative density ρ and does not depend on the shape and volume of the tank. It is calculated by the formula:

$$P_{nx}=h_x\cdot \rho \cdot g,\left(2\right)$$

where g is the acceleration of gravity.

From this formula it can be seen that if the density of the controlled fluid is unchanged, the variable in the formula is the height h _x . Therefore, the pressure of the liquid column will be directly proportional to the height h _x , i.e. liquid level in tank 2, which can be determined by the formula

$$h_x=P_{hx}/\rho \cdot g.\left(3\right)$$

According to equation (1), the liquid column pressure in the tank is determined as the difference between the total pressure P _Σ exerted on the sealed elastic element 17 and the vapor-air pressure P _ax inside the tank 2 - under its cover in space 3 acting on the second sealed elastic element 21.

$$P_{hx}=P_{\Sigma }-P_{ax}.\left(\mathrm{four}\right)$$

The pressure on the sealed elastic element 17 Ps is transmitted through a channel made in the form of a tube 19 to the "Input-2" of the differential pressure sensor 6. In turn, the pressure of the vapor-air atmosphere P _ax acts on the sealed elastic element 21. It is structurally located in the pneumohydraulic part 20 block 1 of the level gauge, which is located under the cover of the tank 2. The pressure exerted on the elastic element 21 P _ax is transmitted through a channel made in the form of a tube 22 to the input "Input-1" of the differential pressure sensor 6. As a result, the differential sensor Pressure IR 6 implements the solution of equation (4) and its output electrical signal will be proportional to the pressure of the liquid column P _hx . From formula (1) - (4) it can be seen that the vapor pressure is fully compensated and the electrical signal of the differential pressure sensor 6 is proportional only to the pressure of the liquid column and, accordingly, the liquid level in the tank 2.

When using a pneumatic channel and, accordingly, an elastic membrane, its flexible side bends in proportion to the pressure of the liquid column. Stretching the membrane leads to a decrease in air volume in the sealed element 17 and the tube 19 and, consequently, to an increase in pressure on the pressure transducer 8. The advantage of the pneumatic channel is the low cost of the differential pneumatic pressure sensor. However, when the temperature changes, the air changes its volume (more strongly than a special liquid). This is perceived by the sensor as a change in pressure and, accordingly, as a change in liquid level and increases the measurement error. In addition, due to air compressibility, sensitivity to level changes will be less.

When using a hydraulic channel, a non-elastic membrane is used. The pressure in the tank, proportional to the level of the controlled fluid, is transmitted through this membrane through a column of special fluid in the tube 19 to the input of the hydraulic differential sensor 6. Since the fluid is not compressed, the pressure is transmitted without loss, which can significantly increase the sensitivity of the flowmeter. The advantage of the hydraulic channel is the high accuracy and sensitivity of the hydraulic differential pressure sensor 68.

When using a pneumohydraulic channel, the liquid pressure in the tank 2 is transmitted through the flexible membrane of the sealed element 17 through a column of special incompressible liquid in the tube 19 to the differential pressure sensor 6. However, just before the inlet ("Input-2") of the differential pressure sensor 6, in this case, an air bubble is placed, which allows the use of a cheaper pneumatic pressure sensor. In this case, a change in the volume of the air bubble due to its small size does not significantly affect the accuracy and sensitivity of the level measurement.

When the flow rate of the liquid from the tank 2 through the intake nozzle 25 on the membrane 30 will be a pressure P ₀ equal to the sum of the two components. The first component P _Σ is the same pressure as the pressure exerted on the sealed elastic element 17, i.e. determined by the liquid level and the pressure of the vapor-air atmosphere under the tank cap. The second component is the hydrodynamic pressure P _{gd ..} , determined by the flow rate of the liquid. Given formula (1), we can write

$$P_0=P_{g.d.}+P_{\Sigma }=P_{g.d.}+P_{hx}+P_{ax}.\left(5\right)$$

The pressure P ₀ through the tube 32 is supplied to the "Input-2" of the differential pressure sensor 7. The tube 32, similar to the tube 19, is a pressure transmission channel. Like the channel based on the tube 19, it can be made pneumatic, hydraulic or pneumohydraulic.

Hydrodynamic pressure P _g. determined from the following equation

$$P_{g.d.}=Q^2\frac{\rho }{S_{memb.}^2}sin\alpha \text{A.},\left(6\right)$$

where S _memb. - membrane area 30; α is the angle between the axis of the liquid jet and the membrane 30.

The developed device allows you to compensate for the pressure P _Σ , determined by the liquid level and the pressure of the vapor-air atmosphere under the cover of the tank 2. As a result, the output of the differential pressure sensor 7 will be a signal proportional to the hydrodynamic pressure P _{gd ..} , which is determined by the flow rate of the liquid from the tank 2

$$P_{g.d.}=P_0-P_{\Sigma }=P_0-\left(P_{hx}+P_{ax}\right).\left(7\right)$$

Knowing the hydrodynamic pressure P _{gd ..} , from equation (6), you can determine the flow rate of the liquid from the tank 2 at a known density and known design parameters of the device

$$Q=S_{memb.}\sqrt{\frac{P_{g.d.}}{\rho Sin\alpha }}.\left(8\right)$$

To compensate for the pressure P _Σ acting on the membrane 30 together with the hydrodynamic pressure, it is possible with the help of a liquid level change compensation unit, which can have two manufacturing options.

In the first embodiment, the pressure P _Σ through the tube 33, diverted from the tube 19 of the sealed element 17, is supplied to the input "Input-1" of the differential pressure sensor 7. In the differential pressure sensor 7, the pressure supplied to the "Input-1" and "Input-2 "are subtracted from each other according to equation (7).

In the second embodiment, the pressure compensation P _{Σ is} carried out in the Converter 27 flow of fluid into pressure. To do this, the pressure P £ is supplied through the tube 34 to the flow into pressure transducer 27 between the additional membrane 35 and the hermetic outlet compartment 31. As a result, the pressure P _Σ will act counter to the total hydraulic fluid pressure P ₀ as described by equation (7). In this case, only the hydrodynamic pressure P _gd will be supplied through the tube 32 to the “Input-2” of the differential pressure sensor 7 _. . The "Input-1" of the differential pressure sensor 7 must be plugged.

Thus, the developed design of the level meter-flowmeter allows to measure with high accuracy both the level and the flow rate of the controlled liquid from the tank. Inside the tank with a controlled fluid placed only pneumohydraulic structural elements that do not contain mechanical moving elements. Therefore, the reliability of the level gauge is significantly increased in comparison with analogues, including in comparison with float level gauges containing mechanical movable structural elements in the tank with a controlled fluid.

Controlled liquid, the level and flow rate of which is measured, can be explosive and fire hazardous liquids, various types of fuel. The proposed device allows for explosion and fire safety since all electrical elements and connections (electronic unit 4) of the device are located outside the tank with a controlled fluid - outside the explosion and fire hazard zone. They can be placed, for example, in the instrument compartment 5, or in a special sealed unit near the tank. Therefore, the reliability of the developed level gauge-flow meter is significantly increased in comparison with analogues.

The internal cavity of the channels 22 and 19, as well as of the sealed elements 17 and 22, as well as of the sealed outlet compartment 31, are isolated from the external environment, which makes the flowmeter insensitive to condensation due to temperature changes, the corrosive effects of aggressive controlled liquids and other disturbing influences of the external media and controlled fluids.

When the liquid level in the tank changes, for example, when pumping out the liquid, under the cap of the tank above the controlled liquid a vacuum can be created (with an increase in the level, a corresponding increase in pressure). This occurs when the throttle openings (not shown in FIG.) In the lid of the tank 2 are clogged, for example, iced up, dirty or absent. The latter can occur in cases where the fluid is in several tanks communicating with each other or when internal clamping shells are used. In addition, even with throttle openings, with a rapid change in liquid level, the pressure under the tank cover will not be equal to atmospheric. That is, the pressure P _ax with a change in the level h _x will also change. In this case, the results of measuring the level and flow rate using known devices that do not take into account the change in the pressure of the vapor-air atmosphere inside the tank above the controlled liquid will contain a large error.

The proposed design is less dependent on environmental and operating conditions while maintaining high accuracy and reliability of the device, with ease of maintenance and low cost.

The proposed design has higher reliability, since the sensitive elements are sealed and the change in the properties of the controlled fluid (increase in viscosity at low temperatures, precipitation of its components of paraffins, sulfur, etc.) does not affect their performance. The proposed design has a higher metrological reliability, since when measuring the level and flow there is no error from changes in pressure in the tank, which is especially important for especially severe road-climatic conditions, as well as higher dynamic accuracy when measuring during vehicle movement due to vibration damping fluid at the pneumatic channel.

In addition, the proposed design is simpler in manufacturing, assembly technology, maintenance and operation, i.e. simpler and cheaper. The advantage of the developed level meter-flowmeter is high accuracy with high reliability.

At present, a pilot prototype of the level meter and flowmeter has been manufactured on the basis of OJSC Vityaz Engineering Company. Benchmark comparative tests of the level gauge with the closest analogues have been carried out, which confirmed the solution of the tasks.

Claims (9)

1. The level meter-liquid flow meter in the tank, comprising a housing, a differential pressure sensor with two inputs, connected to a liquid level indicator, a pneumohydraulic unit including a sealed cavity, a tube with a through channel for vertical immersion of it on the bottom of the tank with a liquid controlled at one end, and the other end connected to one of the inputs of the differential pressure sensor, the second input of which is connected to one end of the second tube with a through channel, the other end of which is led into the vapor-air atmosphere under the lid of the tank, in addition, the end of the tube with a through channel led out to the bottom of the tank and the end of the tube brought into the vapor-air atmosphere under the lid of the tank are connected to the corresponding sealed elastic elements, thus forming an internal cavity of the pneumatic channels isolated from the external environment, moreover, the sealed elastic elements are made in the form of membrane boxes, part of the sides of which or all, in particular one side, are elastic, and the rest, respectively, are rigid, while the elastic sides can be filled in the form of rates - membranes or flexible films or corrugated plates or an elastic hollow ball, in addition, a sealed elastic element placed inside the tank in a liquid is made in a recess on the bottom of the tank, for example, in a drain neck, in addition, a sealed elastic element placed inside the tank in the area of vapor-air atmosphere, is made inside the tank cover, which consists of an inlet flange attached to the tank and through screw connections through the seal with the neck and body, and to the body with screws through spring the washer and gasket are screwed on the plate, the pneumatic channel tubes through the nipples and connecting tubes are connected to the inputs of the differential pressure sensor, which is attached to the housing with a bolt and washer and spring washer, the electric wires of the differential pressure sensor are connected to the power supply terminal "+" from the vehicle electrical system, and the housing is connected to the mass with a bolt, the information signal is removed from the signal terminal, in addition, a measuring tank is introduced in which the pneumohydraulic unit of the level gauge is located, in addition, both the taut elastic elements are interconnected by a casing made in the form of a damping cup, inside of which a sealed elastic element is installed, which is installed on the bottom of the tank with a controlled fluid, the casing containing a fixing axis coaxial with the damping cup, connecting the sealed elastic elements, and the damping cup and the coaxial fixing axis of the housing is interconnected by stiffeners, in addition, the damping housing of the housing is cylindrical, in addition, damping The cup consists of separate parts and movable couplings, covering the joints of the individual parts, the number of parts being determined based on the ratio of the maximum height of the tank to the length of the separate part, the tube of the pneumatic channel looks like an elastic spiral, the movable couplings have through holes in which the balls are located, on the outside, the balls are covered by elastic clamps, or in the form of elastic rings (spring washers), on the outside of the individual parts of the damping cup located under the movable couplings, there are grooves, extending at a distance from each other equal to the minimum fixed position of the individual parts with respect to each other, in addition, the lower separate part of the damping cup is connected to the upstream separate part of the damping cup using a threaded connection, the maximum length of the separate lower part in the extended state is not less the minimum fixed position of the individual parts with respect to each other, dowels are installed above and below the sealed elastic element, near the lower end throttle holes have throttle openings, or throttle cutouts directly at its end, characterized in that it further comprises a flow to pressure transducer, a second differential pressure sensor with two inputs connected to a liquid flow indicator, and a liquid level change compensation unit with a compensating channel, moreover, the flow to pressure transducer, including connecting intake and consumable fittings, consists of a chamber, which, in turn, consists of two compartments - a receiving and a sealed outlet compartment separated from it by a separation membrane, the outlet compartment is connected through a channel made in the form of a tube of small diameter to one of the two inputs of the second differential pressure sensor. 2. The liquid level meter in the tank according to claim 1, characterized in that in the block for compensating for changes in the liquid level, the compensating channel is a discharge tube connected at one end to a pipe coming from the sealed element located at the bottom of the tank with the controlled liquid, the second the end of the discharge tube is connected to one of the inputs of the second differential pressure sensor. 3. The liquid level meter in the tank according to claim 1, characterized in that the unit for compensating for changes in the liquid level is connected to the flow to pressure transducer, and the compensating channel is a tube removed from the tank with a controlled liquid, the second end of this tube being connected a flow to pressure transducer between the additional membrane and the sealed outlet compartment, wherein the additional membrane divides the flow into pressure transducer into two halves, the first half being connected to the intake by similar fittings, the second half is connected to a through channel made in the form of a small-diameter tube connected to one of the two inputs of the second differential pressure sensor, in addition, the center of the additional membrane is connected by a rod to the center of the separation membrane of the sealed outlet compartment. 4. The liquid level meter in the tank according to claim 1, characterized in that the sealed element located on the bottom of the tank with the controlled fluid, and connected to it through the channel, made in the form of a tube of small diameter connected at the other end to the input of the first differential sensor pressure, as well as a second sealed element located in the vapor-air atmosphere above the controlled liquid - under the cap of the tank, and a through channel connected to it, made in the form of a tube connected to another input of the first differential Occupancy pressure, filled with a special antifreeze fluid, e.g. silicone oil, or antifreeze. 5. The liquid level flow meter in the tank according to claim 1, characterized in that the output compartment of the flow to pressure transducer and the through channel, made in the form of a small diameter tube, are filled with special non-freezing liquid, for example silicone oil or antifreeze. 6. The liquid level meter in the tank according to any one of claims 1 and 4, characterized in that in front of the first and second input of the first differential pressure sensor connected to the through channels, one of which goes to a sealed element located at the bottom of the tank with liquid, and the second to a sealed elastic element located in the vapor-air atmosphere above the controlled liquid - under the tank cover, is an air bubble. 7. The liquid level meter in the tank according to any one of claims 1, 2, and 4, characterized in that the compensating channel tube diverted from the tube extending from the sealed element is filled with a special non-freezing liquid, for example silicone oil or antifreeze. 8. The liquid level meter in the tank according to any one of claims 1, 2 and 4, characterized in that an air bubble is located in front of the second differential pressure sensor connected to the second end of the compensating channel tube. 9. The liquid level meter in the tank according to any one of claims 1, 3 and 5, characterized in that before the inlet of the second differential pressure sensor connected to the second end of the through channel, made in the form of a small diameter pipe connected to the output compartment of the flow transducer in pressure, there is an air bubble.

Images