System for measuring temporally resolved flow processes of gases

Abstract

Systems for measuring temporally resolved flow processes are known, comprising a rotational displacer (18) arranged in a gas line (10) between an inlet (12) and an outlet (14), a translational pressure difference sensor (26), which is arranged in a bypass line (16) bypassing the rotational displacer (18) and which comprises a displacement body (30) that is translationally movable in a measurement chamber (28), a detection device (32) that records the deflection of the displacement body (30) in the measurement chamber (28) and is connected to a control and evaluation unit (24), and a drive motor (20) via which the rotational displacer (18) is driven in a manner regulated via the control and evaluation unit (24) as a function of the measured values of the detection device (32). In order to be able to use these systems for measuring gases as well, it is proposed that the displacement body (30) comprises a body part (42) which is produced from a diamagnetic material and interacts with a magnetic field which is generated by magnets (40) in the measurement chamber (28) and which has an alternating polarity in a width direction (Y), which is directed perpendicularly to the displacement direction (X) of the displacement body (30) and perpendicularly to the gravitational force (Z), and has a constant polarity in the displacement direction (X).

Description

[0001] System for measuring time-resolved flow processes of gases

[0002] The invention relates to a system for measuring time-resolved flow processes of gases, which system comprises a rotary displacer arranged in a gas line between an inlet and an outlet, a translatory pressure difference sensor arranged in a bypass line bypassing the rotary displacer, and which has a displacement body which is translationally movable in a measuring chamber, a detection device which records the deflection of the displacement body in the measuring chamber and is connected to a control and evaluation unit, and a drive motor via which the rotary displacer is driven in a controlled manner via the control and evaluation unit as a function of the measured values ​​of the detection device.

[0003] Such systems have been known for many years for measuring the quantity of liquids and are used, for example, to measure the injection quantity in internal combustion engines. For example, DE 1 798 080 describes an electronically controlled flow meter with an inlet and an outlet, between which a rotary displacer in the form of a gear pump and a piston in a measuring chamber in a line parallel to the displacer are arranged. To determine the flow rate, the deflection of the piston in the measuring chamber is measured using an optical sensor. Based on this signal, the speed of the gear pump is continuously adjusted via an evaluation and control unit in such a way that the piston is always returned to its starting position, so that only small flows arise in the bypass line.The flow rate within a given time interval is calculated from the number of revolutions or partial revolutions of the gear pump measured by a sensor and the known delivery volume of the gear pump during one revolution.

[0004] A flow meter constructed in this way is also described in DE 10331 228 B3. To determine the precise injection flow curves, the gear pump is set to a constant speed before the start of injection, so that the piston movement is subsequently measured and used to determine the injection curves.

[0005] This measuring principle has become established for the measurement of liquids due to its very high accuracy and, at the same time, very precise temporal resolution.

[0006] However, there is the problem that transfer is not possible for measuring gases, as there are no materials available for manufacturing the piston that allow it to float in a gas, as is possible for pistons with the same density as the surrounding liquid. This is necessary, however, because contact between the piston and the inner walls of the measuring chamber, which is unavoidable for a body with a higher density in a gas due to the gravitational force acting on it, leads to friction losses that would significantly distort the measurement result.

[0007] The task therefore arises to create a system for measuring time-resolved flow processes in which the established measuring principle can also be used to measure time-resolved flow processes of gases, such as hydrogen or oxygen for fuel cell applications.

[0008] This object is achieved by a system for measuring time-resolved flow processes of gases having the features of claim 1.

[0009] The system according to the invention for measuring time-resolved flow processes of gases has a rotary displacer arranged in a gas line between an inlet and an outlet. The gas line forms the line through which the measurement gas flows or is conveyed. The rotary displacer is a rotary-driven conveying unit, such as a pump or compressor, that is suitable for conveying gas in the line. Furthermore, the system has a translational pressure difference sensor arranged in a bypass line bypassing the rotary displacer. This bypass line branches off from the gas line between the inlet and the rotary displacer and opens back into the gas line between the rotary displacer and the outlet. The translational pressure difference sensor has a measuring chamber in which a translationally movable displacement body is arranged.This can be designed as a type of piston, whereby its shape must be adapted to the shape of the measuring chamber in such a way that only a small gap remains between the inner walls of the measuring chamber and the outer walls of the displacement body. This is necessary to ensure that any pressure difference between the ends of the measuring chamber acts entirely on the displacement body and does not lead to a flow along the displacement body. Furthermore, a detection device is provided which records the deflection of the displacement body in the measuring chamber and is connected to a control and evaluation unit. The detection device must be suitable for measuring the path of the displacement body that it travels in the measuring chamber as synchronously and accurately as possible.The results of this measurement are transmitted to the control and evaluation unit, which is also connected to a drive motor that drives the rotary displacer. The control and evaluation unit regulates the drive motor and thus the rotary displacer depending on the measured values ​​from the recording device. This is done in such a way that the pressure difference across the displacement body is zero and the displacement body therefore remains largely in a defined position in the measuring chamber or, in the case of a flow measurement, is briefly moved back to this position. Since each rotation of the drive motor and thus of the rotary displacer can be assigned to a defined volume flow, the speed of the drive motor is monitored by a sensor such as an encoder, and the volume flow is calculated accordingly from the speed.In addition to controlling the rotary displacer, the displacement of the displacement body can also be used to determine the volume flow rate in order to resolve flow processes over time.

[0010] In order to be able to use this system for gases, the displacement body has a body part which is made of a diamagnetic material and interacts with a magnetic field generated in the measuring chamber by magnets, which has an alternating polarity in a width direction which is directed perpendicular to the displacement direction of the displacement body and perpendicular to the gravitational force, and has a constant polarity in the displacement direction.

[0011] The magnets can be permanent magnets or electromagnets with active feedback circuitry. A body is called diamagnetic if it has a magnetic susceptibility of less than 0 or a relative permeability of less than 1. Such a material is levited by the inhomogeneous magnetic field of alternating poles. This is called diamagnetic levitation. Upon application of the magnetic field, dipoles are induced in a diamagnetic material. According to Lenz's law, these dipoles are directed opposite to the generating magnetic field and are thus repelled. This causes the body part, and with it the displacing body, to levitate if the repulsive force acting on the body part is directed opposite to the gravitational force.By maintaining a field that is as homogeneous as possible in the direction of movement, potential valleys acting in this direction are avoided, which would otherwise result in a force acting on the diamagnetic part of the displacement body in the direction of displacement. This makes it possible to let the displacement body levitate at a fixed distance from the magnets and thus move it contact-free within the measuring chamber. This makes it possible to use the measuring principle also for gases, whose volume flows can be measured with correspondingly high precision and temporal resolution.

[0012] Preferably, the diamagnetic body part forms a surface of the sliding body that faces the magnets. Since the force acting on the diamagnetic body part against gravity by the magnetic field strongly depends on the distance from the magnets, the sliding body can be made to levitate more easily in this way, even if it has a somewhat higher density.

[0013] In a preferred embodiment, the diamagnetic body part is made of pyrolytic graphite, particularly highly oriented pyrolytic graphite. Graphite has strong diamagnetism, which is further enhanced in pyrolytic graphite because the graphite molecules are layered, whereby the diamagnetism perpendicular to the layers is significantly higher than parallel to them. Accordingly, a particularly strong repulsive force exists. Preferably, at least two magnets of opposite polarity are arranged side by side, viewed in the width direction of the measuring chamber, to generate the magnetic field. The number of two magnets of opposite polarity forms the minimum unit for generating an inhomogeneous magnetic field suitable for generating levitation.

[0014] It is particularly advantageous if, viewed in the width direction of the measuring chamber, at least four magnets are arranged next to one another, with each magnet having a polarity opposite to that of the adjacent magnet, and the diamagnetic body part being formed by a plate extending parallel to the magnets, with the repulsive force acting on the plate acting opposite to the gravitational force. The number of magnets arranged next to one another can be selected depending on the width of the displacement body. Preferred magnet widths are between 5 and 20 mm. Using at least four magnets creates greater inhomogeneity of the magnetic field across the width of the measuring chamber, which leads to a higher repulsive force.

[0015] Viewed in the width direction, the extension of the diamagnetic plate is slightly smaller than the total extension of all adjacent magnets. This results in the diamagnetic plate, and with it the displacement body, being centered over the magnet, as it is located in a field with the lowest possible potential. This centering is particularly strong when the laterally limiting magnets extend beyond the diamagnetic plate by approximately half their width. Accordingly, this also prevents lateral displacement or tilting of the body part and thus the displacement body.

[0016] A particularly simple design is achieved when the measuring chamber and the displacement body are cuboid-shaped, with one surface of the cuboid being formed by the diamagnetic plate. This simplifies precise manufacturing and enables good guidance while maintaining small gaps around the displacement body. In an alternative embodiment, two magnets of alternating polarity form a magnet pair, with several magnet pairs evenly distributed around the circumference of the measuring chamber. In this way, the levitate of the displacement body can be ensured regardless of the positioning of the measuring chamber relative to the weight.

[0017] In a further embodiment, viewed in cross-section relative to the direction of displacement, at least four further magnets with alternating polarity are arranged on either side of the first at least four magnets, each at an angle to the first at least four magnets, and each parallel to a further plate forming the diamagnetic body part. Adjacent poles of a row of four magnets naturally also have reversed polarity. This design provides additional, reliable centering and guidance of the displacement body in the direction of displacement, which is also subject to a repulsive force that acts at least partially in the width direction. This prevents contact between the displacement body and the laterally delimiting inner walls of the measuring chamber.

[0018] Furthermore, in an alternative embodiment, magnets of alternating polarity can be arranged over the entire circumference of the measuring chamber, viewed in cross-section relative to the displacement direction, with the diamagnetic body portion extending over the circumference of the displacement body parallel to the respective opposing magnets. This design results in a fully enclosed guide with a repulsive force evenly distributed over the circumference, preventing any friction caused by contact between the inner walls of the measuring chamber and the outer walls of the displacement body. This prevents measurement errors caused by additional forces.

[0019] In a further embodiment, at least four magnets are arranged next to each other to form a magnet row, and several of these rows are arranged at an angle to each other. The magnetic polarity is alternated over the entire circumference. Depending on the angle used, rectangular, hexagonal, or octagonal measuring chambers can be created in cross-section, which are suitable for reliable guidance.

[0020] It is further particularly preferred if a magnetic return element made of a ferromagnetic material is arranged on the side of the magnets facing away from the displacement body. This creates a magnetic return element by preventing further scattering of the magnetic field lines and correspondingly amplifies the inhomogeneous magnetic field acting on the diamagnetic body part, thereby achieving a stronger repulsive force.

[0021] In a further embodiment, the return element is formed by a steel plate on which the permanent magnets are arranged. This can be achieved, for example, by simple gluing. The plate has the same dimensions as the entire assembly of magnets. This results in very simple manufacturing.

[0022] In an advantageous embodiment, the magnets extend over the entire length of the measuring chamber, viewed in the direction of displacement of the displacement body. This design creates a completely homogeneous magnetic field in the direction of displacement, thus avoiding holding forces caused by potential valleys in this direction.

[0023] A particularly simple manufacturing process is achieved when each magnet is designed as a permanent magnet cuboid. These are particularly easy to process and assemble.

[0024] In an alternative embodiment, the magnets are formed by a polymagnetic plate. Such a polymagnetic plate is magnetized in sections to form the desired arrangement of magnets.

[0025] In yet another alternative design, several magnets of the same polarity are arranged directly adjacent to each other in the direction of displacement of the displacement body. The magnetic field generated by this arrangement is not completely homogeneous, but the potential differences are so small that any resulting measurement errors can be neglected, at least for larger flow rates.

[0026] The displacement body is preferably designed to be closed in cross-section in the direction of displacement, with a gap of a maximum of 0.7 mm, in particular less than 0.5 mm, between an outer wall of the displacement body and a surrounding inner wall of the measuring chamber. The optimal gap range is between 0.01 and 0.3 mm. For even smaller gaps, very precise manufacturing is necessary, which results in high technical effort and, at the same time, little technical benefit. For larger gaps, leakage increases significantly. A flow develops between the two ends of the piston, which falsifies the measurement results. With the gaps mentioned, very good measurement results are achieved with manageable manufacturing effort.

[0027] It is also advantageous if the magnets form at least part of the inner wall of the measuring chamber, as this allows very small distances to the diamagnetic body part to be maintained, thus achieving a strong repulsive force. This allows the use of a heavier displacement body.

[0028] In an alternative preferred embodiment, a wall of the measuring chamber is formed between the magnets and the measuring chamber. This wall is less than 2 mm thick and is made of a non-magnetizable material. This design is particularly necessary for flow measurement of gases that may react with the material used for the magnets. Damage can be avoided accordingly in this case. The thin wall still provides a sufficient magnetic field to generate the levitation of a light moving body.

[0029] Preferably, the outer wall of the displacement body, facing the inner wall of the measuring chamber, extends in the displacement direction over a length that is greater than the extent of the displacement body perpendicular to the displacement direction. This creates an elongated displacement body. This has the advantage that the resulting long gap creates greater flow resistance, preventing flow around the displacement body. This results in more accurate measurement results.

[0030] Furthermore, it is advantageous if the rotary displacement device is a pump, a turbine gas meter, a rotary piston meter, a scroll compressor, or a screw conveyor. For these devices, the rotational speed and thus the flow rate can be determined very precisely, for example, using an encoder, allowing an exact flow rate to be determined.

[0031] The detection device is preferably designed as an optical sensor, ultrasonic sensor, camera, capacitive sensor, or lidar sensor. These detection devices enable a high-resolution, very precise measurement of the displacement of the displacement body in the measuring chamber.

[0032] To further prevent friction that could distort the measurement results and thus counteract the displacement in the event of contact between the displacement body and the inner wall of the measuring chamber, the inner wall of the measuring chamber or the outer wall of the displacement body opposite the inner wall, outside the diamagnetic body section, is coated with a material with a friction coefficient of less than 0.2, such as Teflon. This significantly reduces the displacement force caused by the pressure difference.

[0033] Preferably, the measuring chamber can be set into vibration in the width direction. This prevents a sliding body with its smooth surface from adhering to the smooth inner wall of the measuring chamber. Furthermore, even if the measuring device is tilted in the y direction, it is guaranteed that the piston is at least temporarily repelled from the wall and that there is a free floating phase. This reliably prevents hysteresis effects. Such vibration can be generated using various actuators. Examples include a small electric motor with an asymmetrically mounted weight attached to its shaft as an eccentric, the rotation of which causes vibrations, or a piezoelectric actuator, in which electrical energy is converted into mechanical movement to generate the desired vibrations. Such piezoelectric actuators can be controlled very precisely, so that the desired vibration frequency can also be set.Linear resonant actuators can also be used. These are types of vibration motors that move a small weight at its resonant frequency via a spring mechanism, creating a high-frequency, linear motion, and can be used to control correspondingly precise vibration patterns. Voice coils can also be used, which generate vibrations by moving in a magnetic field, or solenoid valve coils, whose magnetic field, created by applying an electric current, deflects a plunger in the longitudinal direction.

[0034] Furthermore, it is advantageous if the displacement body is manufactured by selective laser sintering using a 3D printing process and bonded to the diamagnetic body part. This allows the displacement body to be manufactured with high precision from a very lightweight material, so that low repulsive forces are sufficient to achieve levitation of the displacement body.

[0035] This provides a system for measuring temporally resolved flow processes, which can also measure gas flow rates with high temporal accuracy and precision. Accordingly, highly accurate dosing of hydrogen for a fuel cell system is possible, for example.

[0036] The system according to the invention for measuring time-resolved flow processes of gases is described below with reference to non-limiting embodiments shown in the figures.

[0037] Figure 1 shows a schematic of the basic structure of a system according to the invention for measuring time-resolved flow processes of gases.

[0038] Figure 2 shows a perspective view of a measuring chamber of the system for measuring time-resolved flow processes of gases from Figure 1 in a cut-away view.

[0039] Figure 3 shows an alternative embodiment to Figure 2 in a horizontal section through the measuring chamber. Figure 4 shows another alternative embodiment in a vertical section through the measuring chamber.

[0040] The system according to the invention for measuring time-resolved gas flow processes shown in Figure 1 consists of a gas line 10 extending from an inlet 12 to an outlet 14, as well as a bypass line 16, via which a rotary displacer 18 arranged in the gas line 10 can be bypassed. Accordingly, the bypass line 16 branches off from the gas line 10 between the inlet 12 and the rotary displacer 18 and flows back into the gas line 10 between the rotary displacer 18 and the outlet 14. The rotary displacer 18 can be designed as a pump, driven turbine gas meter, rotary piston meter, scroll compressor, or screw conveyor and is driven by a drive motor 20. A sensor 23 for detecting the rotational speed of the drive motor 20 or the conveyor wheel 22 is arranged on the drive motor 20 or on a conveyor wheel 22 of the rotary displacer 18.The drive motor 20 is speed-controlled via a control and evaluation unit 24.

[0041] A translational pressure difference sensor 26 is arranged in the bypass line 16. The sensor consists of a measuring chamber 28 and a translationally movable displacement body 30 arranged in the measuring chamber 28. When a pressure difference is present between the front and rear of the displacement body 30, the displacement body 30 is deflected from its rest position. Accordingly, the deflection of the displacement body 30 is a measure of the existing pressure difference. A detection device 32 in the form of an optical sensor designed as a laser sensor is arranged on the measuring chamber 28. The optical sensor is operatively connected to the displacement body 30 and via which a deflection of the displacement body 30 from its defined starting position is determined. Alternatively, other displacement sensors, such as ultrasonic sensors, cameras, capacitive sensors, or lidar sensors, can be used instead of the laser sensor.

[0042] The detection device 32 is also connected to the control and evaluation unit 24, which also serves to evaluate the measurements of the detection device 32 and converts them into control signals for the drive motor 20, which is controlled in such a way that the displacement body 30 is always in a defined starting position, if possible. The rotary displacer 18 thus constantly compensates for the pressure difference created by the flowing gas on the displacement body 30 by conveying gas. This means that when the displacement body 30 is deflected to the right, the speed of the rotary displacer 18 is increased depending on the magnitude of this deflection, and vice versa.For this purpose, the deflection of the displacement body 30 or the volume displaced by it in the measuring chamber 28 is converted by means of a transfer function into a desired delivery volume of the rotary displacer 18 or a speed of the drive motor 20 and the drive motor 20 is energized accordingly.

[0043] The measurements are carried out in such a way that when calculating a total flow to be determined in the control and evaluation unit 24, both a flow in the bypass line 16 resulting from the movement or position of the displacement body 30 and the volume displaced thereby in the measuring chamber 28 and an actual flow of the rotary displacer 18 in a specified time interval are taken into account, and both flow rates are added together to determine the total flow. If no time-resolved flow processes are to be mapped, only the flow determined at the rotary displacer 18 can be taken into account, since this is controlled in such a way that the pressure difference across the displacement body 30 always returns to zero and thus the displacement body is always pushed back to its starting position.

[0044] The flow rate at the displacement body 30 is determined, for example, by differentiating the deflection of the displacement body 30 in the control and evaluation unit 24, which is connected to the detection device 32, and then multiplying it by the base area of ​​the displacement body 30, so that a volume flow in the bypass line 16 results in this time interval.

[0045] The flow through the rotary displacer 18 and thus in the gas line 10 can either be determined from the determined control data for controlling the displacer 18 or can be calculated via the rotational speed if this is measured directly on the displacer 18 or on the drive motor 20 via the sensor 23, which can be designed, for example, as an optical encoder or magnetoresistive sensor.

[0046] For proper functionality, the sliding body 30 must float freely within the measuring chamber 28. Otherwise, friction would develop between the outer walls 34 of the sliding body 30 and the inner walls 36 of the measuring chamber 28, generating a force component counter to the direction of movement of the sliding body 30. This would distort the measurements because the sliding body 30 would no longer be moved solely in response to the applied differential pressure. Since no materials exist that have the same density as the gas, which would be required for such floating, the floating of the sliding body 30 must be achieved by another means.

[0047] In the present case, the effect of diamagnetic levitation is used for this purpose. To achieve this, as can be seen in Figure 2, magnets 40 are arranged on a floor 38 of the measuring chamber 28. In the present embodiment, these magnets are designed as cuboid-shaped permanent magnets. Four of these magnets 40 are arranged next to one another in the width direction Y of the measuring chamber 28 and extend in the displacement direction X of the displacement body 30 over the entire length of the measuring chamber 28. Adjacent magnets 40 each have opposite polarity, such that the first magnet 40.1 has a north pole pointing upwards into the measuring chamber 28 and a south pole pointing downwards, while the adjacent magnet 40.2 has a south pole pointing upwards into the measuring chamber 28 and a north pole pointing downwards. The third magnet 40.3 is in turn oriented in the same way as the first magnet 40.1 and the fourth magnet 40.4 is oriented in the same way as the second magnet 40.2.

[0048] Furthermore, the displacement body 30 has a diamagnetic body part 42, which is designed as a diamagnetic plate 44 and consists of pyrolytic graphite and forms a surface of the displacement body 30 that is directed towards the magnets 40. The diamagnetic plate 44 can be attached, for example, by adhesive bonding to the rest of the displacement body 30, which, like the measuring chamber 28, is cuboid-shaped and whose cross-section in the displacement direction X is slightly smaller than the internal cross-section of the measuring chamber 28. The diamagnetic plate 44 is located above the magnets 40, so that it is loaded by the gravitational force G in the direction Z toward the magnets 40.

[0049] The width of the diamagnetic plate 44, for example, corresponds approximately to the width of three of the adjacent magnets 40. The adjacent magnets generate a magnetic field that is inhomogeneous in the y-direction and homogeneous in the x-direction. This means that, viewed in the y-direction, strongly fluctuating potentials are present. Potential peaks are created whose extent is only slightly smaller than that of the magnets, as well as relatively narrow valleys between the magnets. Although a diamagnetic material does not have dipoles, it has the property that the application of a magnetic field induces dipoles in the material that, according to Lenz's law, are directed opposite to the generating magnetic field and are thus repelled. This is an induction effect. The resulting force is thus opposite to the gravitational force. In addition, the diamagnetic plate 44 attempts to achieve an energy minimum through its position.It achieves this by covering as many potential valleys as possible. With the described width of plate 44, as many potential valleys as possible are covered when plate 44 is located in the center of the four magnets 40 with respect to the z-direction, since only in this position does it cover the three potential valleys created between the magnets 40. This means that plate 44 assumes a stable position with respect to the z-direction and also assumes a stable position with respect to the y-direction above the magnets 40, namely at the position where the repulsive force between plate 44 and magnets 40 is in equilibrium with the gravitational force acting on the displacement body 30, including body part 42.In the X-direction, i.e. the direction of displacement of the displacement body 30 and simultaneously the direction in which the differential pressure prevails, no force acts other than the force due to the differential pressure, since the magnetic field is homogeneous in this direction and has no potential peaks or valleys. Accordingly, the displacement body 30 is displaced exclusively by the pressure difference in the x-direction, so that a reliable measurement is possible. It should also be noted that, if possible, the displacement body 30 and the surrounding measuring chamber 28 should be coordinated in their cross-sections so that, if possible, only a circumferential gap 46 of 0.01 to 0.3 mm is created between the outer wall 34 of the displacement body 30 and the inner wall 36 of the measuring chamber 28. Such a gap 46 largely prevents contact.To minimize unintentional wall contact in the event of sudden pressure surges, the outer wall 34 and / or the inner wall 36 can also be coated with Teflon to keep the friction coefficient as low as possible. Additionally, the measuring chamber 28 can be vibrated in the y-direction relative to the displacement body 30 to prevent the displacement body 30 from sticking with its outer wall 34 to the inner wall 36 of the measuring chamber 28. These vibrations can be continuously generated by appropriate actuators, such as small electric motors with an imbalance, piezoelectric actuators, linear resonance actuators, voice coils, or solenoid valve coils.

[0050] To create the desired gap 46, the magnetic force and density of the displacement body 30 must first be adjusted so that the displacement body 30 hovers at a corresponding height above the magnet 40. To keep its weight low, the displacement body 30 is designed as a cuboid hollow body with only one inflow surface closing the inner cross-section.

[0051] In order to generate a sufficiently large magnetic field with as little scattering as possible, a ferromagnetic return element 50 is arranged below the magnets 40. In the present embodiment, this element is designed as a steel plate 52 on which the magnets 40 are arranged and which has the same dimensions in the X and Y directions as the four magnets 40. This steel plate 52 has a thickness of, for example, 1 to 10 mm in the Z direction and serves to concentrate the magnetic field lines, thereby amplifying the magnetic field.

[0052] Furthermore, the magnets 40 form a lower inner wall 36 of the measuring chamber 28, thus limiting it at the bottom, eliminating the need for additional gaps to be overcome by the magnetic field. For chemically active gases that may react with the material of the magnets 40, a wall a few tenths of a millimeter thick and made of a non-magnetizable material can also be used.

[0053] Figure 3 shows an alternative embodiment, in which identical parts are provided with identical reference numerals. In comparison to the first embodiment, in addition to the lower magnet row 54, consisting of four magnets 40, further magnet rows 56 are arranged on both sides, which also consist of four adjacent magnets 57. However, the magnets 40, 57 have alternating polarities over the entire covered circumference. The magnet rows 56 are each positioned at an angle of approximately 45° to the lower magnet row 54. These magnet rows 56 are now used in the same way as the lower magnet row 54 to generate levitation and accordingly have another steel plate 52 on their underside to concentrate the magnetic field lines. The measuring chamber 28, like the displacement body 30, has a corresponding shape and can, for example, be designed as an octagon.In the areas opposite the magnet rows 56, further diamagnetic body parts 58 in the form of further graphite plates 60 are of course arranged, which at least partially form an outer wall 34 of the displacement body 30.

[0054] Due to the resulting repulsion, which functions in the same way as described for exemplary embodiment 1, the displacement body 30 is additionally guided without contact and contact with the inner walls 36 of the measuring chamber 28 is prevented. This creates a type of guidance for the displacement body in the X direction. It should also be noted that in this exemplary embodiment, instead of the long magnetic rods 40.1 - 40.4, smaller magnetic cubes 62 are used, with the same pole pointing towards the interior of the measuring chamber 28 in the X direction. With such an arrangement, in which these magnets 40 are in direct contact with one another, only very small potential valleys exist between the potential peaks, so that the magnetic field in the x direction is no longer completely homogeneous and therefore less precise measurements are possible. Depending on the application, however, the accuracy may be sufficient.The embodiment according to Figure 4 differs from the embodiment according to Figure 3 only in that the magnet rows 56, each consisting of four adjacent magnets 40, and the associated return path elements 50 extend over the entire circumference of the measuring chamber 28 and are each arranged at an angle of 45° to the adjacent magnet row 56 or return path element 50. Accordingly, the displacement body 30 is also octagonal, with a diamagnetic body part 42 arranged on each of its side surfaces. This can, of course, also be designed as a one-piece octagon.This design allows the entire system to be rotated around the x-axis for measuring time-resolved flow processes, as repulsion occurs from all sides, thus preventing contact between the sliding body 30 and the inner wall 36 of the measuring chamber 28, regardless of the rotational position, due to the all-round repulsive force. Accordingly, the desired gaps can be maintained over the entire circumference, regardless of the rotational position of the measuring chamber.

[0055] The described systems and pressure differential sensors reveal the possibility of highly accurate and temporally resolved measurement of flow processes of gases, such as hydrogen. The established measurement method for measuring fluids can be further used with the modifications according to the invention. Such a measurement with such precise temporal resolution is previously unknown for measuring gases.

[0056] It should be clear that the arrangement of the magnets is not limited to the described embodiments. For example, electromagnets or a polymagnetic plate can also be used to generate the magnetic field, or a larger number of magnets can be placed in a row. It is also possible, for example, to arrange the magnets in a circle and to give the measuring chamber and displacement body a cylindrical shape. Further modifications will also be apparent to those skilled in the art.

Claims

P A T E N T A N S P R Ü C H E 1 . A system for measuring time-resolved flow processes of gases, comprising: a rotary displacer (18) arranged in a gas line (10) between an inlet (12) and an outlet (14), a translational pressure difference sensor (26) arranged in a bypass line (16) bypassing the rotary displacer (18), and having a displacement body (30) movable in translation in a measuring chamber (28), a detection device (32) which records the deflection of the displacement body (30) in the measuring chamber (28) and is connected to a control and evaluation unit (24), a drive motor (20) via which the rotary displacer (18) is driven in a controlled manner via the control and evaluation unit (24) depending on the measured values ​​of the detection device (32), characterized in that the displacement body (30) has a body part (42),which is made of a diamagnetic material and interacts with a magnetic field generated in the measuring chamber (28) by magnets (40), which has an alternating polarity in a width direction (Y) which is perpendicular to the displacement direction (X) of the displacement body (30) and perpendicular to the gravitational force (Z), and has a constant polarity in the displacement direction (X).

2. System for measuring time-resolved flow processes of gases according to claim 1, characterized in that the diamagnetic body part (42) forms a surface of the displacement body (30) which is directed towards the magnets (40).

3. System for measuring time-resolved flow processes of gases according to claim 1 or 2, characterized in that the diamagnetic body part (42) is made of a pyrolytic graphite.

4. System for measuring time-resolved flow processes of gases according to one of the preceding claims, characterized in that, viewed in the width direction (Y) of the measuring chamber (28), at least two magnets (40) of opposite polarity are arranged next to one another, which generate the magnetic field.

5. System for measuring time-resolved flow processes of gases according to claim 4, characterized in that at least four magnets (40.1, 40.2, 40.3, 40.4) are arranged next to one another in the width direction of the measuring chamber (28), each magnet (40.1, 40.2, 40.3, 40.4) having a polarity opposite to that of the adjacent magnet (40.1, 40.2, 40.3, 40.4) and the diamagnetic body part (42) is formed by a diamagnetic plate (44) which extends parallel to the magnets (40.1, 40.2, 40.3, 40.4), the repulsion force acting on the diamagnetic plate (44) by the magnetic field acting opposite to the gravitational force (Z).

6. System for measuring time-resolved flow processes of gases according to claim 5, characterized in that, viewed in the width direction (Y) of the measuring chamber (28), the extension of the diamagnetic plate (44) is slightly smaller than the total extension of all adjacent magnets (40.1, 40.2, 40.3, 40.4).

7. System for measuring time-resolved flow processes of gases according to one of the preceding claims, characterized in that the measuring chamber (28) and the displacement body (30) are cuboid-shaped.

8. System for measuring time-resolved flow processes of gases according to claim 4, characterized in that two magnets (40) of alternating polarity form a magnet pair, wherein several magnet pairs are arranged evenly distributed over the circumference of the measuring chamber (28).

9. System for measuring time-resolved flow processes of gases according to claim 5, characterized in that, viewed in cross section to the direction of displacement (X), at least four further magnets (57) with alternating polarity are arranged on both sides of the first at least four magnets (40.1, 40.2, 40.3, 40.4), which are arranged at an angle to the first at least four magnets (40.1, 40.2, 40.3, 40.4), and which are each arranged parallel to a further plate (60) forming the diamagnetic body part (58).

10. System for measuring time-resolved flow processes of gases according to one of claims 1 to 3, characterized in that, viewed in cross section to the direction of displacement, magnets (40, 57) of alternating polarity are arranged over the entire circumference of the measuring chamber (28), wherein the diamagnetic body part (42) extends over the circumference of the displacement body (30) parallel to the respective opposite magnets (40, 57).

11. System for measuring time-resolved flow processes of gases according to claim 10, characterized in that at least four magnets (40) are arranged next to one another to form a row of magnets (54, 56) and several of these rows of magnets (54, 56) are each arranged at an angle to one another.

12. System for measuring time-resolved flow processes of gases according to one of the preceding claims, characterized in that a magnetic return element (50) made of a ferromagnetic material is arranged on the side of the magnets (40, 57) facing away from the displacement body (30).

13. System for measuring time-resolved flow processes of gases according to claim 12, characterized in that the return element (50) is formed by a steel plate (52) on which the magnets (40, 57) designed as permanent magnets are arranged.

14. System for measuring time-resolved flow processes of gases according to one of the preceding claims, characterized in that the magnets (40, 57) extend over the entire length of the measuring chamber (28) when viewed in the direction of displacement of the displacement body (30).

15. System for measuring time-resolved flow processes of gases according to one of the preceding claims, characterized in that each magnet (40, 57) is designed as a permanent magnet cuboid.

16. System for measuring time-resolved flow processes of gases according to one of claims 1 to 14, characterized in that the magnets (40, 57) are formed by a polymagnet plate.

17. System for measuring time-resolved flow processes of gases according to one of claims 1 to 14, characterized in that viewed in the direction of displacement of the displacement body (30), a plurality of magnets (40, 57) of the same polarity are arranged directly adjacent to one another.

18. System for measuring time-resolved flow processes of gases according to one of the preceding claims, characterized in that the displacement body (30) is designed to be closed in cross section to the displacement direction (X) and a gap (45) of a maximum of 0.7 mm is formed between an outer wall (34) of the displacement body (30) and a surrounding inner wall (36) of the measuring chamber (28).

19. System for measuring time-resolved flow processes of gases according to claim 18, characterized in that the magnets (40, 57) at least partially form the inner wall (36) of the measuring chamber (28).

20. System for measuring time-resolved flow processes of gases according to claim 18, characterized in that a wall of the measuring chamber (28) is formed between the magnets (40, 57) and the measuring chamber (28), which wall is less than 2 mm thick and which consists of a non-magnetizable material.

21. System for measuring time-resolved flow processes of gases according to one of claims 18 to 20, characterized in that the outer wall (34) of the displacement body (30) directed towards the inner wall (36) of the measuring chamber (28) extends in the displacement direction (X) over a length which is greater than an extension of the displacement body (30) perpendicular to the displacement direction (X).

22. System for measuring time-resolved flow processes of gases according to one of the preceding claims, characterized in that the rotary displacer (18) is a pump, a turbine gas meter, a rotary piston meter, a scroll compressor or a screw conveyor.

23. System for measuring time-resolved flow processes of gases according to one of the preceding claims, characterized in that the detection device (32) is designed as an optical sensor, ultrasonic sensor, camera, capacitive sensor or lidar sensor.

24. System for measuring time-resolved flow processes of gases according to one of claims 18 to 23, characterized in that the inner wall (36) of the measuring chamber (28) or the outer wall (34) of the displacement body (30) opposite the inner wall (36) is coated outside the diamagnetic body part (42) with a material having a friction coefficient of less than 0.

2.

25. System for measuring time-resolved flow processes of gases according to one of the preceding claims, characterized in that the measuring chamber (28) can be set into vibration in the width direction (Y).

26. System for measuring time-resolved flow processes of gases according to one of the preceding claims, characterized in that the displacement body (30) is produced by selective laser sintering in a 3D printing process and is glued to the diamagnetic body part (42).

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