RU2339084C1 - Device of bench automated laboratory complex for studying hydrodynamic processes witt measurements and processing of results in program medium lab view - Google Patents

Abstract

FIELD: information technology.

SUBSTANCE: invention can be used while studying Reinhold's criterion, modes of transformation of forms of energy of the stream of a liquid (Bernoulli's equation), examples of practical application of Bernoulli's equation - Ventura's flow-meter, hydraulic resistance with construction of virtual hydraulic schemes, with measurement of hydraulic parameters and simultaneous construction of graphic dependences on the monitor of a personal computer and copying on rigid data carriers.

EFFECT: increase in accuracy and quality of maintenance of measurements at the stand of all necessary parameters; maintenance of their automation; obtaining the necessary calculated assigned functional dependences and output to electronic and paper data carriers.

8 cl, 12 dwg

Description

The invention relates to special equipment intended for demonstration and practical training of university students and technical colleges in technical disciplines, and more specifically for demonstration and practical study of the main hydrodynamic processes in the study of the Reynolds criterion, modes of transformation of the forms of energy of a fluid flow (Bernoulli equation), examples of practical application of the equation Bernoulli - a flowmeter of Venturi, hydraulic resistance with the construction of virtual hydraulic circuits, measurement hydraulic parameters and the simultaneous construction of graphical dependencies on a personal computer monitor and copying on hard data carriers.

The well-known hydraulic universal bench ТМЖ-2 for studying hydrodynamic processes in a university [1]. The stand is made of one table having a horizontal mounting surface, on which one of several interchangeable devices - modules, for example, for determining hydraulic resistance, made of metal pipes, is placed, and several glass tubes are located on a vertical surface attached to the rear edge of the horizontal mounting surface (piezometers) for visual observation of pressure drops in various sections of round, metal pipes interconnected in series. In addition, several float rotameters are attached to the vertical surface, which make it possible to measure the flow rate of the fluid flowing in the pipes supplied by a centrifugal pump placed under the horizontal surface.

The disadvantage of such a stand is that all changes in the parameters of the studied hydrodynamic processes carried out at a well-known stand can be recorded only visually and then mathematically processed according to known formulas using the data obtained. In addition, when studying the modes of fluid movement (determination of the Reynolds criterion), the replaceable module (transparent glass tube) is located horizontally, that when a color tracer is introduced into the fluid flow, due to the difference in the specific gravity of the studied and tinted liquids, the tracer settles and erodes, leading to distortion the investigated process. To measure the flow rate of the liquid, float rotameters are used, which cannot provide sufficient accuracy, and the recording of readings can be done only visually. When studying the Bernoulli equation, there is no way to visually show the student the energy costs in the stream.

Known laboratory bench for the study of hydrodynamics and heat transfer during fluid flow in pipes [2]. The stand is designed to study hydrodynamics and heat transfer during the flow of liquids in pipes, methods of probe measurements in fluid flows. The stand can be used in secondary and higher technical educational institutions at the department, faculty, institute level. The stand is equipped with hardware-software and instrumental tools to support and support the educational process and scientific research.

A disadvantage of the well-known stand is that it is not equipped with an element for studying the modes of transformation of the forms of energy of the fluid flow (Bernoulli equation) and, just as in [1], it is not possible to visually show the student the energy costs in the flow.

Known educational equipment for universities - stand "Hydraulics DG" [3], adopted as a prototype. The stand is made of one having vertical table legs, on a horizontal surface of which there is a device made of glass pipes of different diameters, which allows fluid to study their hydraulic resistance at different Reynolds numbers while moving along them, and on a vertical surface attached to the rear edge of the horizontal surface , several glass tubes (piezometers) are located for visual observation of pressure drops in various sections of round, glass pipes connected between have it consistently. In addition, several float rotameters are attached to the vertical surface, which make it possible to measure the flow rate of water flowing in the pipes supplied by a centrifugal pump placed under the horizontal mounting surface. The stand, also on a vertical wall, has a reinforced glass funnel for studying laminar and turbulent flow regimes.

The disadvantage of this stand is that in the study of the conversion of energy forms of the fluid flow (Bernoulli equation), sensors were used to measure only the static pressure, and the dynamic pressure is determined by calculation. In addition, when studying the flow regimes of the fluid (determining the Reynolds criterion), a funnel located above the level of the fluid under investigation leads to the fact that when the tracer is introduced into the flow of the investigated fluid, the tracer increases the velocity of the tracer relative to the fluid flow under study. And just as in [1], all measurements of parameters studied by students of hydrodynamic processes carried out at a well-known stand can be registered only visually and, further, according to the data obtained, be subjected to mathematical processing. To measure the flow rate of the liquid, float rotameters are used, which cannot provide sufficient accuracy, and the recording of readings can be done only visually. When studying the Bernoulli equation, there is no way to visually show the student the energy costs in the stream.

The problem to which the invention is directed, is to increase the accuracy and quality of providing measurements at the bench of all the necessary parameters obtained both with the help of measuring sensors and on a virtual image of the laboratory bench, and ensuring their comparison in automatic mode, as well as providing automation measurements of all necessary parameters, obtaining the necessary calculated predetermined functional dependencies and output to electronic and paper media used in the form of a report.

This is achieved by the fact that the device is a bench-mounted automated laboratory complex for studying hydrodynamic processes with measurements and processing the results in the Lab View software environment, made of a table with horizontal and vertical mounting surfaces, of which tubular elements of the bench are placed on the horizontal, simulating fluid movement along their variables sections, and for studying the laminar and turbulent flow regimes by introducing a color tracer into the flow, as well as instruments for measuring p liquid gathering and piezometers for measuring parameters of fluid pressure in various sections of tubular elements, while to ensure the circulation of fluid through the tubular elements under the horizontal mounting surface there is a pump buried in a container installed under the table on the floor, while the device of the complex is equipped with a second table, the first of which is equipped with horizontal and vertical mounting surfaces, on the first of which a U-shaped metal pipe with a straight line is placed with a specified length, with a pipe turning section of 180 ° and a section with a large diameter, designed to study linear and local hydraulic resistance, and, in addition, to its lateral surface, at the entrance and exit of the straight section, as well as at the entrance and the outlet of the pipe turning section, at the inlet and outlet of the section with a large diameter, pipes with sensors for measuring static and total pressure are connected perpendicularly, with elastic pipes connected to them connected to their piezometers, In the form of transparent tubes, and placed on a vertical mounting surface, in addition, on a vertical mounting surface for studying the phenomena described by the Bernoulli equation, a tubular element with a transparent front wall inclined from the input end to the output end and having a rectangular inner section is placed, while its axis relative to the horizontal surface is placed at an angle α equal to 5 to 10 °, and its input end is set higher than the output, while the inclined element is made in the form of five therefore, connected and made of one continuous material of parts, the first, in the form of a tetrahedral rectangular prism, which is connected with one base to the second part, having the shape of a tetrahedral rectangular pyramid, the flat top of which is rigidly connected to the third part in the form of a tetrahedral rectangular prism with a square in cross section, the second base of which is rigidly connected to the flat top of the fourth part, of exactly the same pyramid as the second part, the base of which is connected to the fifth part, made in in the form of a tetrahedral rectangular prism, with a rectangle in cross section and equal opposite pairs in pairs, as in the first part, in addition, for measuring the total and static pressure on the axis of the fluid flow in the inner cavity of this element, along its entire length, at the inlet end of the first part , in the middle of the second part, in the middle of the third part, in the middle of the fourth part and at the output end of the fifth part, sensors for measuring the total pressure are built in perpendicular to the axis of the inclined element, each of which is made of two tubes, p a ditch, in the direction of flow of the liquid, for measuring the static pressure made of a straight tube, the working end of which is installed perpendicular to the flow, and a second tube, the working end of which is bent to meet the movement of the fluid flow, and the non-working ends of these tubes are connected by elastic tubes to their pairs of piezometers made of rigid transparent tubes and rigidly mounted on a vertical mounting surface, while in the interval between each pair of piezometers a metric scale is rigidly installed, which like piezometers, it is attached to a vertical mounting surface; in addition, to visually fix the liquid level in the tubes of each piezometer and to demonstrate the potential energy costs of the liquid flow in each section of the inclined element to study the phenomena described by the Bernoulli equation, rigidly placed near each piezometer vertical racks with lateral grooves, in which the clips are movably placed, on which two colored ropes are sequentially and movably fixed, one of them being assigned to mark the liquid level in all piezometers of static pressure, and the second to mark the liquid level in all piezometers of full pressure, and a shut-off valve is installed at the output end of the inclined element, in addition, to supply liquid to the U-shaped pipe and to the inclined element on a vertical mounting surface there is a pressure tank filled with liquid by means of a pump installed in a special plastic container secretly placed in the volume of the left cabinet of the first table, the pressure pipe of which connected to the ceiling part of the pressure tank, while the ceiling part is installed not lower than the upper ends of all piezometers placed on the vertical mounting surface, and a vertically located pipe is attached to the bottom of the pressure tank, the lower end of which is equipped with a tee, one tap of which is connected to the input end of the inclined element and the second - to the inlet end of the pipe in a U-shape, while the outlet end of the inclined element is connected through a shut-off valve to its liquid flow meter, the outlet pipe whose window is filled into a special plastic container with a pump, in addition, a transparent tube made of rigid material is vertically connected to the bottom of the pressure tank to study the laminar and turbulent modes of fluid flow (determining the Reynolds criterion) with a vertical tracer along its axis in its tank, which is located in the cavity of the pressure tank, and the output end of which is connected to its liquid flow meter, the output pipe of which is connected to its shut-off valve, in the running end of which is connected to a pipe filled into a container, covertly placed in the right pedestal of the first table, in addition, on the second two-pedestal table on a horizontal installation surface there is a personal computer system unit, its monitor, speakers and a multi-tier unit made of analog-to-digital converters (ADC), the keyboard control unit is located on a pull-out panel located under the horizontal mounting surface, in the center of the second table.

A device has been installed as a liquid flow meter, which provides the creation of electrical pulses at the output, which ensure coordination with the Lab View analog-to-digital converters block.

The stand can be equipped with three cold and hot water flow meters of the Sayany brand IVKA 407323 PS, with an electronic output signal.

The clamp for each piezometer, each pair of piezometers connected to the sensors of the inclined element can be made in the form of a metal plate spring-loaded to its stand, having an eye for the free movement of its own cord in it.

Each of the two ropes is rigidly fixed in the eye on only one, the most left retainer.

The Lab View analog-to-digital converters block is located on the second table, from the side closest to the first table.

The metric scale can be made of a standard metal ruler according to GOST 427-75.

The supporting legs of both tables can be made in the form of a Z-shaped.

The invention is illustrated by drawings, where figure 1 shows a General view of the stand on two tables. Figure 2 shows the view of the bench table in arrow A (horizontal mounting surface). Figure 3 from the dashed line shows 70% of the vertical mounting surface, and down - 30% of the horizontal mounting surface of the elements of the first stand table. Figure 4 shows the main elements (sections) of the U-shaped pipe. Figure 5 shows the inclined element. Figure 6 shows a section aa. Figure 7 shows the placement of sensors full and static pressure. On Fig depicted the cutout of the piezometer and rack with a latch. Figure 9 shows a cross section of a pair of piezometers with racks and clamps. Figure 10 shows the latch. Figure 11 shows a view of B. Figure 12 shows a virtual sketch of an inclined element with devices.

The device of the bench automated laboratory complex consists of two tables: table 1, with mounting surfaces, horizontal 2 and vertical 3, and also table 4. On a horizontal mounting surface 2 there is a U-shaped pipe 5 having a straight section 6 of a given length, section 7 with rotation of the pipe by 180 ° and section 8 with a large diameter, designed to study linear and local hydraulic resistance. At the same time, pipes 15 with sensors 16 are connected perpendicularly to the input 9 and the output 10 of section 6, to the input 11 and the output 12 of section 7, to the input 13 and the output 14 of section 8 to measure the static and total pressure in the sections of the U-shaped pipe . These sensors are connected using transparent and elastic tubes 17 with their piezometers 18, made in the form of transparent rigid tubes placed on a vertical mounting surface 3. On the same surface 3 there is an inclined tubular element 19 having a rectangular inner section and a transparent front wall. The input end 20 of the element 19 is placed above its output end 21. The element 19 is made in the form of five series-connected parts, the first 22 in the form of a tetrahedral rectangular prism, the second 23 in the form of a tetrahedral rectangular pyramid, the flat top of which is rigidly connected to the third part - the base of the tetrahedral rectangular prism 24, the second base of which is connected to the fourth part - the flat top of the tetrahedral rectangular pyramid 25, the base of which is connected to the fifth part 26, made in the form of tetrahedral th rectangular prism. Sensors are installed in pairs at the inlet ends of all parts of element 19: at the inlet end 20, on the first part 22, on part 23, on part 24, on part 25, on part 26 and on output end 21, sensors 27 are built perpendicular to the axis of element 19 for measuring the total pressure, made from the tube 28, and for measuring the static pressure from the tube 29. Each pair of sensors 27 is connected by its elastic transparent tubes 30 with their pairs of piezometers 31 located on the surface 3. Between the tubes of each pair of piezometers 31 on the surface 3 posted metric scale 32. On the outer sides of each pair of piezometers 31, vertical posts 33 are attached, having grooves 34, in which position locks 35 are movably placed, on which two colored ropes 36 and 37 are sequentially and movably fixed, the first 36 of which is intended for marking the liquid level in the tubes of static pressure, and the second 37 of them in the tubes of full pressure. The output end 21 of the element 19 is connected to the shut-off valve 38. To supply fluid to the U-shaped pipe 5 and the inclined element 19, a pressure tank 39 is placed on the surface 3, filled with liquid by means of a pump 40 installed in a plastic container 41, hidden in the left cabinet 42 tables 1. The pressure pipe 43 of the pump 40 is connected to the ceiling part 44 of the tank 39. A pipe 45 is connected to the bottom of the tank 39, the lower end of which is equipped with a tee 46, one tap of which is connected to the input end 20 of the element 19, and the second through a shut-off valve 47 to input 9 y part 6 of the pipe 5, and the output 14 of the output section 8 is connected to its flow meter 48, the output pipe of which is connected to the shut-off valve 49, the output pipe of which is recessed into the tank 41. The output end 21 of the element 19 is connected to the shut-off valve 50, the output pipe of which is connected with a flow meter 51, the outlet pipe of which is buried in the tank 41. In addition, a transparent pipe 52 is vertically connected to the bottom of the tank 39, designed to visually demonstrate the regimes of laminar and turbulent fluid flows using a wind tracer located in its tank 53 and placed in the cavity of the tank 39. The output end of the tube 52 through the shut-off valve 54 and the flow meter 55 is tucked into a container 57 which is hidden in the right cabinet 56. On the second (right) two-table table 4 on a horizontal surface 58 is placed the system unit 59 of the personal computer, its monitor 60, the speakers 61 and the device of the multi-tier block 62 of analog-to-digital converters (ADCs), the key control unit 63 is located on the sliding panel 64 of the table 4. The latches 35 on each rack 33 issue ying with two spring-loaded plates 65 and 66 have an eyelet with a circular hole 67.

The device operates as follows.

1. The study of hydraulic resistance to friction (or length) and local resistance.

The study of hydraulic friction resistance in the inner cavity of the pipe in a straight section (stainless steel pipe with a length of 820 mm and an inner diameter of 8 mm) is carried out according to the following method:

1. Turns on email. the engine of the pump 40, which is installed in a plastic container 41, located in the left pedestal of the first table 1, and using the pump 40, water is pumped into the pressure tank 39.

2. With the maximum opening of the shut-off valve:

- register the readings of the piezometers 18 installed next to the ruler scales 32;

- visually register against the background of scale 32, the water level in the transparent tubes of two piezometers 18, the first connected to a static pressure sensor installed at the inlet to a straight pipe section of a given length, and the second connected to a static pressure sensor installed at the output of a straight pipe section of a given lengths;

- with the established flow regime, we determine the numerical value of the water flow through the counter 47 for a given time, for example, in one minute.

3. We change the position of the shut-off valve 48 (we cover it by a small angle) and repeat the operations of step 2.

We carry out similar measurements for other positions of the shut-off valve 48, up to its complete closure. The number of fixed positions of the valve 48 determines the accuracy of the experiment. For laboratory work, six valve openings 48 are sufficient.

4. In parallel with the “manual” experiment, turn on the PC, display the Lab View program, create a virtual sketch of measuring instruments (piezometers connected to the straight section of the pipe, virtually a liquid flow meter) on the monitor. In accordance with the experimental procedure, we set from the keyboard the readings of piezometers in millimeters of water. At the end of the experiment, we give a command to build a graph of the dependences of hydraulic resistance on fluid flow through the pipe. In addition, by command, we obtain the numerical calculated value of the hydraulic resistance and compare it with the experimental value obtained by the “manual” method, and calculate the error. A virtual installation diagram, for example, studying the energy characteristics of a hydroflow (Bernoulli equation), is presented in Fig. 12.

Using a bench automated laboratory complex for studying hydrodynamic processes with measurements and processing results in the Lab View software environment, other laboratory works are carried out, the methodology of which is described in [4].

The interval of the angle α of the inclined element location from 5 ° to 10 ° is explained by the fact that when the stand is included in the pressure tank, the inclined element, the piezometers get a lot of air bubbles, which take a lot of time to be removed, and the smaller the angle α, the greater time is spent on it, but constructive manufacturing is simplified. Therefore, it has been experimentally established that 5 ° is the optimal minimum angle. At 10 °, the time for removing air bubbles from the stand elements is noticeably reduced. At an angle greater than 10 °, the constructive manufacture of the inclined element is complicated.

The rectangular internal section of the inclined element allows, firstly, to exclude the effect of the lens during visual observation, and secondly, to simplify the manufacture and fastening of the inclined element with nozzle narrowing, as well as to simplify the calculation of the area in the "live section" of the fluid flow.

The supporting legs of the tables, made in the form of a Z-shaped shape, can improve access to them, facilitate their weight and at the same time maintain high stability of the equipment placed on them.

The use of colored ropes allows the student to clearly demonstrate to the student the energy characteristic of the hydroflow in a channel of complex shape, since the area under the cord characterizes the potential flow energy at the points of connection of the piezometers.

The usefulness of the claimed invention is to increase the technical level of knowledge transfer to students in the discipline "Hydraulics" taught at the university by equipping the stand with modern instruments and devices that allow to obtain high accuracy and reliability of work and, in addition, allowing to transfer the received information to a computer for later processing and obtaining both analytical equations and graphical dependencies about the process under study. The usefulness also lies in introducing students to modern technical capabilities in the field of quick and accurate processing of experimental studies.

Information sources

1. www.samgtu.ru/research/katalog/PDF/007.pdf

2. www.cati.ru/edu/voda.htm

3. www.intos.ru/tehn1.htm

4. Semenova E.V., Kireev D.V., Tretyak P.V., Koryachkin V.P., Vanin B.C. Using LabVIEW graphical programming environment for laboratory stands. Department "Machines and equipment for food production". Eagle GTU. Eagle, 2007.

Claims (8)

1. A bench automated laboratory complex for studying hydrodynamic processes with measurements and processing the results in the Lab View software environment, made from a table with horizontal and vertical mounting surfaces, of which tubular bench elements are placed on the horizontal, simulating fluid movement over their variable cross sections and for studying laminar and turbulent flow regimes by introducing a color tracer into the flow, as well as instruments for measuring fluid flow, and piezo meters for measuring fluid pressure parameters in various sections of tubular elements, in order to ensure fluid circulation through the tubular elements, a pump is placed under the horizontal mounting surface, buried in a container installed under the table, on the floor, characterized in that the device of the complex is equipped with a second table, the first of which is equipped with horizontal and vertical mounting surfaces, on the first of which a U-shaped metal pipe is placed, with a rectilinear rear section length, with a section of pipe rotation of 180 ° and a section with a large diameter, designed to study linear and local hydraulic resistance, and, in addition, to its lateral surface, at the entrance and exit of the straight section, as well as at the entrance and exit pipe turning section, at the input and output sections of the section with a large diameter, pipes are connected perpendicularly with sensors for measuring static and total pressure, with elastic pipes connected to them, connected to their piezometers made in the form of transparent tubes, and placed on a vertical mounting surface, in addition, on a vertical mounting surface for studying the phenomena described by the Bernoulli equation, a tubular element with a transparent front wall inclined from the input end to the output end and having a rectangular inner section, with its axis relative to the horizontal surface is placed at an angle α equal to from 5 to 10 °, and its input end is set higher than the output, while the inclined element is made in the form of five rows parts that are connected and made of one continuous material, the first, in the form of a tetrahedral rectangular prism, which is connected with one base to the second part, having the shape of a tetrahedral rectangular pyramid, the flat top of which is rigidly connected to the third part in the form of a tetrahedral rectangular prism with a square in cross section, the second base of which is rigidly connected to the flat top of the fourth part, exactly the same pyramid as the second part, whose base is connected to the fifth part, made in the form of even a reverted rectangular prism, with a rectangle in cross section and equal opposite pairs in pairs, as in the first part, while for measuring the total and static pressure on the axis of the fluid flow in the inner cavity of this element, along its entire length, at the inlet end of the first part, in the middle of the second part, in the middle of the third part, in the middle of the fourth part and at the output end of the fifth part, sensors for measuring the total pressure are built in perpendicular to the axis of the inclined element, each of which is made of two tubes, the first one in the direction of fluid flow, to measure the static pressure made of a straight tube, the working end of which is installed perpendicular to the flow, and the second tube, the working end of which is bent towards the movement of the fluid flow, and not the working ends of these tubes are connected by elastic tubes to their pairs of piezometers made of rigid transparent tubes and rigidly mounted on a vertical mounting surface, while in the interval between each pair of piezometers a metric scale is rigidly installed, which, like piezometers are attached to a vertical mounting surface, in addition, to visually fix the liquid level in the tubes of each piezometer and to demonstrate the cost of potential energy of the fluid flow in each section of the inclined element to study the phenomena described by the Bernoulli equation, vertical racks with lateral racks are rigidly placed near each piezometer grooves in which the clips are movably placed, on which two colored ropes are sequentially and movably fixed, one of them being intended to mark the liquid level in all piezometers of static pressure, and the second to mark the liquid level in all piezometers of full pressure, and a shut-off valve is installed at the output end of the inclined element, in addition, to supply liquid to the U-shaped pipe and to the inclined element, on a vertical mounting surface contains a pressure tank filled with liquid by means of a pump installed in a special plastic container and secretly placed in the volume of the left cabinet of the first table, the pressure pipe of which is connected n to the ceiling part of the pressure tank, while the ceiling part is installed not lower than the upper ends of all piezometers located on the vertical mounting surface, and a vertically located pipe is attached to the bottom of the pressure tank, the lower end of which is equipped with a tee, one tap of which is connected to the input end of the inclined element and the second to the inlet end of the pipe in a U-shape, while the outlet end of the inclined element is connected through a shut-off valve to its liquid flow meter, the outlet pipe of which it is filled in a special plastic container with a pump, in addition, a transparent tube made of rigid material is vertically connected to the bottom of the pressure tank to study the laminar and turbulent modes of fluid flow (determination of the Reynolds criterion) with a vertical tracer along its axis, placed in color its tank, which is located in the cavity of the pressure tank, and the output end of which is connected to its liquid flow meter, the output pipe of which is connected to its shut-off valve, the output the end of which is connected to a pipe tucked into a container, covertly placed in the right pedestal of the first table, in addition, on the second two-pedestal table on a horizontal installation surface there is a personal computer system unit, its monitor, speakers and a multi-tier unit made of analog-to-digital converters ( ADC), the key control unit is located on a pull-out panel located under the horizontal mounting surface, in the center of the second table. 2. The device according to claim 1, characterized in that a device is installed as a liquid flow meter that provides the creation of electrical pulses at the output, which ensures coordination with the Lab View analog-to-digital converters block. 3. The device according to claim 2, characterized in that the stand is equipped with three flow meters for cold and hot water of the Sayany brand IVKA 407323 PS with an electronic output signal. 4. The device according to claim 1, characterized in that the latch for each piezometer, each pair of piezometers connected to the sensors of the inclined element is made in the form of a metal plate spring-loaded to its rack, having an eye for free movement of its cord in it. 5. The device according to claim 4, characterized in that each of the two ropes is rigidly mounted in the eye only on one, the most left retainer. 6. The device according to claim 1, characterized in that the block of analog-to-digital converters of the Lab View program is located on the second table, from the side closest to the first table. 7. The device according to claim 1, characterized in that the metric scale is made of a standard metal ruler according to GOST 427-75. 8. The device according to claim 1, characterized in that the support legs of both tables are made in the form of a Z-shaped.

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