Method and apparatus for generating and measuring liquid-gas mixtures; computer program product

Abstract

The invention relates to a method for generating and measuring liquid-gas mixtures, in particular oil foams. A liquid is introduced into a container (1). A portion of the liquid from the container (1) is conveyed through a mixing circuit (2), whereby a gas is added to the liquid to generate a liquid-gas mixture, particularly one containing gas bubbles. The liquid-gas mixture is then returned to the container (1). Furthermore, a portion of the liquid-gas mixture is conveyed through a measuring circuit (3), whereby optical image data of the liquid-gas mixture are acquired in a measuring area (3a) to measure any gas bubbles contained therein. The liquid-gas mixture is then returned to the container (1). The image data are analyzed to determine a measured value of the contact area per volume between the liquid and the gas from the total surface area of ​​the gas bubbles.Furthermore, it is planned that a target value for the contact area per volume in the liquid-gas mixture will be set by iteratively repeating process steps.

Description

[0001] The invention relates to a method for producing and measuring liquid-gas mixtures, in particular oil foams.

[0002] The invention also relates to a device for producing and measuring liquid-gas mixtures, in particular oil foams.

[0003] The invention further relates to a computer program product.

[0004] Liquid-gas mixtures are important in various contexts. For example, the foaming of oils, especially gear oils, is highly significant in machine operation, as oil oxidation by dissolved oxygen and / or gas or air bubbles introduced during operation is one of the most important chemical damage mechanisms for oil aging. To optimally match the oil selection to the intended application, experimental investigations of the oils are essential.

[0005] To predict the service life of oils under various operating conditions and thus the maintenance intervals of machines, realistic tests and experiments are essential, in which the oil is deliberately exposed to gas or air. In practice, it has proven necessary to simulate the aging of the oil through foaming in an accelerated timeframe, as otherwise the tests would be prohibitively time-consuming.

[0006] Methods and devices for analyzing liquid-gas mixtures are known, for example, from US 10,809,202 B2 and JP 6558315 B2.

[0007] According to the current state of the art, to produce a liquid-gas mixture, a gas is first introduced into a liquid, which can lead to the formation of gas bubbles. These are then measured by optical detection. The resulting image data can be analyzed, for example, with regard to the size or size distribution of the gas bubbles.

[0008] However, precisely controlling the experimental conditions to obtain meaningful results that can be generalized to other situations presents a challenge. For example, information on how much oxygen was dissolved through contact with the air is essential. Furthermore, it has been found that the measurement itself can influence the result, particularly due to pressure variations at different measuring points. This can lead to inaccurate results, especially in the case of compressible media or mixtures.

[0009] The present invention is based on the objective of improving the methods known from the prior art for analyzing liquid-gas mixtures, in particular enabling the production of liquid-gas mixtures with predefined properties.

[0010] According to the invention, this problem is solved by a method having the features mentioned in claim 1.

[0011] The present invention also aims to improve devices known from the prior art for the analysis of liquid-gas mixtures, in particular to enable the production of liquid-gas mixtures with predefined properties.

[0012] According to the invention, this problem is solved by a device having the features mentioned in claim 8.

[0013] The present invention also aims to create a computer program product to carry out an improved method for analyzing liquid-gas mixtures on a suitable device, compared to the prior art.

[0014] According to the invention, this problem is solved by a computer program product with the features mentioned in claim 19.

[0015] Advantageous embodiments of the inventive method, the inventive device and the inventive computer program product are shown, among other things, in the respective dependent claims and in the following description.

[0016] The inventive method for producing and measuring liquid-gas mixtures, in particular oil foams, includes at least the following steps: (a) Putting a liquid into a container; (b) Pumping a portion of the liquid from the container through a mixing circuit, adding a gas to the liquid to produce a liquid-gas mixture, in particular with gas bubbles, after which the liquid-gas mixture is returned to the container; (c) Pumping a portion of the liquid-gas mixture through a measuring circuit, in which optical image data of the liquid-gas mixture are recorded in a measuring area in order to measure gas bubbles contained therein, after which the liquid-gas mixture is returned to the container; (d) Analyzing the image data to determine a measurement of the contact area per volume between the liquid and the gas from the total surface area of ​​the gas bubbles; and (i) Setting a target value of the contact area per volume in the liquid-gas mixture by iteratively repeating steps (b) to (d) at least until the target value is reached.

[0017] The method according to the invention has proven particularly advantageous for analyzing liquid-gas mixtures. By controlling the contact surface between the liquid and the gas, determined by the total surface area of ​​the gas bubbles contained in the mixture, the properties of the resulting liquid-gas mixture can be adjusted or specifically influenced as desired. In contrast to the prior art, the method according to the invention thus makes it possible to reproduce predefined properties of the liquid-gas mixture experimentally, for example, to investigate the oxidation of oil, to generate specific byproducts of reactions between oil and air or oxygen, and / or to control or catalyze the reaction rate.

[0018] The method according to the invention can be carried out particularly advantageously with a device for generating and measuring liquid-gas mixtures, which will be described below. However, the method according to the invention can also be carried out independently of this specific device.

[0019] Within the scope of the invention, a liquid-gas mixture or mixture can be understood as a mixture of a liquid and a gas. Preferably, it is such a mixture in which the gas dissolves only partially in the liquid or fluid, leaving gas bubbles suspended in the liquid. This can also be described as foaming.

[0020] It should be noted that the steps of the method according to the invention do not necessarily have to be carried out in the specified order. The steps can also be carried out at least partially in parallel or overlap in time.

[0021] The container or tank can have a significantly larger capacity than the mixing circuit and / or the measuring circuit. Preferably, the container is at least approximately pressureless or at least at approximately atmospheric pressure. The mixing circuit and / or the measuring circuit, through which the liquid or liquid-gas mixture is conveyed or through which the liquid or liquid-gas mixture flows, can represent a constriction, in particular a throttle.

[0022] The fact that a portion of the liquid is circulated through the mixing circuit and / or the measuring circuit does not mean that the same portion is always circulated. Rather, it is intended that only a portion of the total quantity flows through the two circuits at any given time for mixing or measurement.

[0023] Preferably, the container has a known capacity, in particular a known liquid level after the first step (a) of the method. Furthermore, it can be advantageous if the length of the measuring circuit or the measuring section and / or the length of the mixing circuit or the mixing section is known. When determining the capacity or the fill level of the container, the connected circuits or pipes or lines of the device are preferably also taken into account in order to obtain a value for the total volume of the liquid.

[0024] It may be planned that a portion of the liquid or liquid-gas mixture from the container is continuously pumped through the mixing circuit and / or the measuring circuit. If both circuits are operated continuously, this can occur simultaneously.

[0025] Alternatively, discontinuous and / or iterative conveying through the mixing circuit and / or the measuring circuit can be implemented. Generally, the circulation within these circuits gradually mixes the liquid or liquid-gas mixture in the container. The time required for complete mixing of the liquid or liquid-gas mixture in the container depends on the flow rate through the mixing circuit and / or the measuring circuit.

[0026] A camera can be used to record optical image data.

[0027] The optical image data acquired in step (c) are preferably used to characterize any gas bubbles that may be present in the liquid-gas mixture, for example, with regard to their size, diameter, or surface area. The characterization of the gas bubbles can also relate to their number per volume, their number per diameter, their number per surface area, or their total surface area per liquid volume. Furthermore, the optical image data can be used to analyze the color of the liquid or other properties.

[0028] Different units of measurement for the size of the gas bubbles, such as diameter, radius, surface area or volume, can be converted using generally known mathematical tools or methods from the field of geometry.

[0029] For simplification purposes, when analyzing two-dimensional image data, it can preferably be assumed that the gas bubbles have an ideal geometry and / or that the shape of the gas bubbles is symmetrical in three-dimensional space.

[0030] It can be assumed, at least during a partial step of the analysis, that the gas bubbles have a spherical or cylindrical shape. Assuming a cylindrical shape can be particularly useful if the gas bubbles are deformed within the measurement area, as, without external influence, the gas bubbles would be larger in at least one spatial direction than the available space allows. For example, it can be assumed that the distance or gap defined by the lateral boundaries of the measurement area, such as viewing windows, corresponds to the height of the cylinder. The diameter or radius of the cylinder is derived from the respective diameter of the gas bubble depicted in the optical image data, assuming an ideal circular shape. Using the height and the diameter or radius of the cylinder, the surface area of ​​the gas bubble can then be estimated.

[0031] In addition to acquiring optical image data, other analysis and measurement methods can also be used. For example, samples can be taken from the liquid-gas mixture for chemical analysis.

[0032] It may preferably be provided to determine a percentage ratio of liquid and gas, in particular free, i.e. undissolved gas, in the liquid-gas mixture.

[0033] The contact area refers specifically to the sum of the surface areas of the gas bubbles in the liquid-gas mixture. This contact area can be expressed absolutely, relative to a specific volume, or relatively / normalized to the volume in which the gas bubbles were analyzed. The contact area per volume can, for example, be expressed in square meters per liter. If gas bubbles are present in a liquid, their surface area corresponds to the contact surface between the liquid and the gas.

[0034] To determine the contact area per unit volume, a measurement volume of the measuring range, i.e., the volume of the liquid-gas mixture covered by the optical image data, can be related to the container's capacity or initial fill level, or the initial total volume of the liquid. Preferably, the contact area can be normalized to a unit volume.

[0035] The target value for the contact area per volume can preferably be an actual contact area per volume, i.e., a value determined during operation of the machine or system for which the fluid is intended. The actual contact area per volume may depend on the operating parameters of the machine or system, for example, the rotational speed and / or the operating temperature.

[0036] The target value can be set by comparison with the measured value, particularly the current measured value. Preferably, further analysis steps may be provided to correct errors in the measured value and then use the corrected measured value for comparison with the target value. Reference is also made to the following description.

[0037] Preferably, it is provided that the target value is approached step by step, i.e., that a difference between the measured value or the corrected measured value is not compensated for in a single iteration of the procedure, but that this is done by repeating steps (b) to (d) several times.

[0038] If the measured value is below the target value, additional gas can be added to the liquid-gas mixture in step (b) of the mixing circuit, preferably with less gas being added as the measured value approaches the target value. If the amount of liquid is constant, increasing the amount of gas generally leads to an increase in the number and / or size of the gas bubbles in the liquid-gas mixture, depending, for example, on the viscosity of the liquid. In this way, the total surface area of ​​the gas bubbles, and thus the contact area per volume, can be influenced or adjusted as required.

[0039] The size of the gas bubbles, and thus the contact area per unit volume, can also be influenced by adjusting the flow rate of the liquid-gas mixture through the measuring circuit in step (b). Increasing the flow rate generally intensifies the turbulence, which is associated with the fragmentation of the gas bubbles. Smaller gas bubbles have a larger surface area relative to their volume than larger gas bubbles. Therefore, increasing or decreasing the flow rate can also be used to influence or adjust the contact area per unit volume.

[0040] Another way to adjust the contact area is via the amount of liquid in the container, either absolute or relative to the mixing and measuring circuit, and / or via the container's fill level or the height to which the gas bubbles rise within the container. The liquid quantity or fill level can also be adjusted during the process. Similar to adjusting the gas quantity, adjusting the liquid quantity also affects the air-to-gas ratio or the respective proportions in the liquid-gas mixture, and thus the total surface area of ​​the gas bubbles or the contact area per unit volume. Furthermore, changes in the liquid quantity and / or fill level can alter the pressure conditions, which in turn affect the size of the gas bubbles.

[0041] The aforementioned options for adjusting the contact area, i.e., the supply of additional gas, the adjustment of the turbulence or flow rate in the measuring circuit and / or the adjustment of the amount of liquid or the fill level of the container, can be combined, if necessary, to set the target value of the contact area per volume in the liquid-gas mixture within step (i) or by iteratively repeating steps (b) to (d).

[0042] Even after reaching the target value or desired contact area, the process can be continued iteratively for any length of time to maintain and continuously monitor the target value. This can be useful, for example, if an experiment, such as investigating the oxidation behavior or air separation capacity of oil, takes significantly longer than setting the target value, as gas can escape from the liquid-gas mixture in the container over time.

[0043] If gas escapes unintentionally from the liquid-gas mixture, the lost amount should be compensated for by adding more gas. However, gas escaping can also be intentional if the target value was previously exceeded or if there is too much gas in the liquid-gas mixture.

[0044] If the process has already been carried out at least once, in particular as part of the iterative repetition according to step (i), further gas can be added to the existing liquid-gas mixture in step (b). The term "liquid" here includes, in particular, the liquid-gas mixture.

[0045] The method may be particularly suitable if the liquid is an oil, especially a gear oil, and / or the supplied gas contains oxygen.

[0046] The liquid-gas mixture can, in particular, represent an oil foaming or an oil-air dispersion.

[0047] The oil could be, for example, a gear oil. It could also be a power transmission oil, a hydraulic oil, or a lubricating oil. The fluid could also be another type of liquid lubricant. The oil or lubricant is preferably intended for use in a machine, a system, a test bench, or a power plant component, for example, as hydraulic or lubricating oil in an engine, a gearbox, or a turbine. It could, for example, be used in a paper machine or a wind turbine.

[0048] The gas can be, in particular, air or ambient air, a gas mixture with oxygen, or pure oxygen.

[0049] The method can also be advantageously suited for generating and measuring other liquid-gas mixtures. For example, the method can be advantageously used to investigate the behavior of perfumes, cooling media, especially water-glycol mixtures, pharmaceuticals, such as vaccines, or foodstuffs in air or in a protective atmosphere. Precursors of these products can also be investigated during their manufacture using the method described here, for example, when the production of a foodstuff, such as a confectionery, especially aerated or foamed chocolate, requires foaming or the introduction of bubbles.

[0050] The material properties of the liquid and the gas, as well as their interaction, can influence the parameters suitable or preferred for the process.

[0051] For conveying the liquid or the liquid-gas mixture in steps (b) and (c), preferably at least one pump, and more preferably one pump each for the mixing circuit and the measuring circuit, may be provided.

[0052] Preferably, the respective flow rate or conveying speed can be adjusted via the mixing circuit and / or the measuring circuit.

[0053] The flow rate can be influenced in particular by the viscosity of the liquid.

[0054] It may be designed so that the flow rate in the measuring circuit is significantly lower than in the mixing circuit. For example, the flow rate in the mixing circuit may be up to 300 l / min, while the flow rate in the measuring circuit may be up to 4 l / min.

[0055] Preferably, the flow velocity in the measuring circuit is limited to prevent gas bubbles from collapsing and to enable shake-free or blur-free acquisition of optical image data. This can depend, among other things, on the amount or proportion of gas, as well as on the camera's shutter speed. In particular, it can be advantageous to reduce or throttle the flow velocity with increasing gas proportion or increasing size of the gas bubbles.

[0056] For the acquisition of the optical image data in step (c), it may be advantageous to illuminate the liquid-gas mixture.

[0057] It may preferably be provided that a size distribution of the gas bubbles is determined when analyzing the image data in step (d).

[0058] The size distribution can, in particular, be a frequency distribution of the size, diameter, or surface area of ​​the gas bubbles. Preferably, the size distribution can be represented as a histogram.

[0059] It may also be possible to determine only an average value of the size of the gas bubbles, although this is not preferable.

[0060] In a preferred further development of the process, an additional step is provided: (e) Determining a pressure difference of the measuring circuit, in particular of the measuring range, compared to the container.

[0061] The pressure difference between the measuring circuit and the container, or the pressure change or pressure gradient across the measuring section, can result, in particular, from the fact that the liquid in the container is at least approximately at zero pressure or at least approximately at atmospheric pressure, while a different pressure is established in the measuring circuit due to the constriction or throttle through which the liquid flows at a certain velocity. The pressure gradient can depend on the length of the measuring circuit or measuring section, as well as on the flow resistance within the measuring circuit.

[0062] Under external pressure, the size of gas bubbles typically changes because gas is compressible. If there is a pressure difference between the measuring circuit or the measuring area and the container, the same gas bubble will have a different size in the container than when measured in the circuit. This can lead to inaccuracies or errors in determining the contact area. Therefore, the pressure difference must be taken into account, especially when comparing the measured value with the target value. The influence of the pressure difference can depend on the media properties, particularly the compressibility of the gas and thus the liquid-gas mixture.

[0063] The optional step (e) leads to a further improvement over the state of the art, as the correction or compensation of the pressure difference increases the measurement accuracy and allows for a more precise characterization of the gas bubbles. This makes the testing of liquid-gas mixtures or foams more representative and better transferable to real-world conditions compared to the state of the art.

[0064] Step (e) can also be repeated iteratively within step (i).

[0065] At least one pressure sensor can be used to determine the pressure difference. Preferably, at least one pressure sensor can be arranged in the measuring circuit, particularly in the measuring area. Additionally, another pressure sensor can be arranged in the container. The pressure sensor(s) can be configured and designed to measure either absolute pressure or differential pressure.

[0066] The measurement of the pressure or the determination of the pressure difference can be provided at different times during the process, for example before, during or after step (c), as part of step (d) or as a separate step in between.

[0067] Preferably, the pressure difference is determined in order to take into account the pressure difference through physical pressure equalization or pressure change and / or through computational correction when setting the target value, in particular when comparing the measured value with the target value.

[0068] In particular, it may be possible to eliminate inaccuracies or errors in the measured value caused by the pressure difference, so that any influence of the measurement on the measurement result is at least reduced, and preferably prevented. This is especially important for compressible liquid-gas mixtures.

[0069] It may be advantageous if the pressure difference is at least partially corrected by adjusting the pressure in the measuring circuit in step (c).

[0070] Preferably, the pressure difference is at least partially corrected by adjusting the flow rate of the liquid-gas mixture through the measuring circuit and / or by a bypass line around the measuring range in step (c).

[0071] In particular, reducing the flow velocity can reduce the pressure difference.

[0072] The bypass line can, in particular, be a bypass.

[0073] With the aforementioned solutions for physical pressure equalization, the pressure difference may not be completely corrected. Nevertheless, these solutions may at least be suitable for reducing the pressure difference.

[0074] Physical pressure adjustment is preferably performed before the acquisition and analysis of the optical image data.

[0075] It has proven advantageous if, when analyzing the image data in step (d), an actual value of the contact surface per volume in the container is determined from the measured value of the contact area per volume in the measuring area, whereby the pressure difference is at least partially corrected computationally.

[0076] To correct for the pressure difference, the influence of the pressure difference on the size, preferably the surface area, of the gas bubbles can be calculated. The pressure difference correction thus serves to calculate, estimate, or simulate the actual size of the gas bubbles in the container.

[0077] The computational correction can be used as an alternative or supplement to physical pressure equalization, preferably to obtain an actual value that is completely independent of the pressure difference.

[0078] In a simple embodiment of the invention, the target value can be set based on the measured value from the measuring range by comparing the target value with the measured value. For this purpose, the target value can preferably refer to the desired contact area in the measuring circuit, particularly in the measuring range.

[0079] In a preferred embodiment of the invention, the target value can be set in the container based on a corrected or actual value, i.e., the actual value described above, by comparing the target value with the actual value. For this purpose, the target value can preferably refer to the desired contact area per unit volume in the container.

[0080] The invention also relates to a device for generating and measuring liquid-gas mixtures, in particular oil foams, which has at least one container for receiving a liquid. A mixing circuit with an inlet for supplying a gas to the liquid is provided, wherein a liquid-gas mixture, in particular with gas bubbles, can be generated or is generated by supplying the gas to the liquid. Furthermore, a measuring circuit with a camera for recording optical image data of the liquid-gas mixture in a measuring area for measuring gas bubbles contained therein, as well as an analysis unit for analyzing the image data, is provided, wherein the analysis unit can determine a measured value of a contact area per volume between the liquid and the gas from the total surface area of ​​the gas bubbles.Within the scope of the invention, it is provided that a target value of the contact area per volume in the liquid-gas mixture can be adjusted or set by iterative supply of gas in the mixing circuit and verifying measurement in the measuring circuit.

[0081] The device is particularly well-suited for carrying out the above-described method for generating and measuring liquid-gas mixtures. However, the device can also be used independently of this specific method.

[0082] The advantages of the device according to the invention result analogously from the advantages of the method according to the invention already described.

[0083] The camera should preferably be a CCD camera for taking photos.

[0084] Preferably, the camera has a lens. The camera lens can preferably be a telecentric lens. This is an optical lens in which the entrance pupil and / or exit pupil are located at infinity, so that the beam path is generally at least partially parallel and optical distortions are minimized. This is particularly advantageous for metrological applications. However, the camera lens can also be a conventional lens.

[0085] The optical image data can consist of both photographs and video footage. Snapshots can be extracted from the video footage if needed.

[0086] The time interval between repeated acquisitions of optical image data can be arbitrary. The interval between the images can be selected based on the flow rate of the liquid-gas mixture through the measuring circuit. It is not necessary to photograph the same gas bubble multiple times. For example, at a flow rate of 2 to 3 l / min in the measuring circuit, an interval of a few seconds between images may be suitable. However, it is also possible to take images at intervals of fractions of a second or several minutes. Furthermore, the time interval between images can be tailored to the total duration of an experiment conducted during the procedure or to the duration of the processes under investigation in the liquid-gas mixture.

[0087] The target value for the contact area per volume can preferably be a real contact area per volume based on the intended use of the liquid.

[0088] It is preferably possible to adjust the target value by comparing the measured value with the target value, in order to add more gas to the mixing circuit if necessary when the measured value is lower than the target value. If the measured value is higher than the target value, one can wait until the amount of gas in the liquid-gas mixture, or the gas content, has decreased on its own. When adjusting the target value, the gas content is preferably continuously monitored in the measuring circuit until the target value is reached. Instead of comparing it with the measured value, the target value can preferably be compared with a corrected measured value or an actual value. Reference is also made to the preceding description of the method according to the invention and the following description of preferred embodiments of the device according to the invention.

[0089] The device may be particularly suitable if the liquid is an oil, especially a gear oil, and / or the supplied gas contains oxygen.

[0090] The container preferably has two connecting elements, in particular two connecting pipes, to the mixing circuit and the measuring circuit. The mixing circuit and the measuring circuit are closed loops in that the liquid or the liquid-gas mixture can flow from the container back into the container through the respective circuit.

[0091] The mixing circuit can preferably include a static mixer or be designed as a static mixer.

[0092] The measuring circuit has the measuring range.

[0093] A particularly suitable embodiment of the device is one in which the mixing circuit and the measuring circuit are each connected to the container, wherein at least one pump is provided to pump the liquid or the liquid-gas mixture from the container through the mixing circuit and / or the measuring circuit.

[0094] It can be advantageous to have a lighting device for illuminating the liquid-gas mixture in the measuring area.

[0095] The lighting device can be designed for continuous lighting and / or for flashing lighting.

[0096] Flash lighting can be particularly suitable when the gas bubbles in the liquid-gas mixture move quickly or when the flow rate is high, as the flash allows for a sharper image of the gas bubbles.

[0097] Preferably, the lighting device is designed to illuminate the liquid-gas mixture over a wide area within the measuring range.

[0098] The liquid-gas mixture should be illuminated over a wide area, preferably as uniformly and homogeneously as possible, particularly in the image area where the optical image data is acquired. This can improve the quality of the optical image data and simplify subsequent analysis.

[0099] It has proven particularly advantageous if the lighting equipment is designed and configured to illuminate the liquid-gas mixture in the measuring area with collimated light.

[0100] Compared to diffuse illumination, non-diffuse, and especially collimated, light can achieve significantly better edge sharpness in the images of the liquid-gas mixture with the gas bubbles, which greatly simplifies the analysis of the optical image data. Furthermore, the use of collimated light can also lead to more uniform and homogeneous illumination of the liquid-gas mixture within the measurement area.

[0101] The lighting device can preferably be designed for telecentric lighting.

[0102] Preferably, the lighting device is designed to illuminate the liquid-gas mixture in the measuring area with broadband, in particular white, light.

[0103] Preferably, the lighting device may have at least one LED diode.

[0104] The light intensity and / or the light color or wavelength of the radiation used for illumination is preferably tailored to the liquid under investigation, in particular its optical properties such as absorption, reflection or scattering, and transmission. Preferably, the light intensity and / or the light color is continuously adjustable.

[0105] It has proven particularly suitable if the measuring area has at least one viewing window and / or is transparent to allow the recording of optical image data and / or the illumination of the liquid-gas mixture through the viewing window.

[0106] For this purpose, the camera and / or the lighting device is preferably arranged in a suitable manner. It has proven particularly suitable if the camera and the lighting device are arranged on opposite sides of the measuring area, with the measuring area having a viewing window on both of these sides and / or being transparent. Then the lighting device on one side can shine into the measuring area through the viewing window, and the camera can simultaneously capture the optical image data in backlighting. This can be advantageous for achieving high contrast, which can simplify the evaluation and analysis of the image data.

[0107] Particularly with relatively opaque liquids such as oils, it can be advantageous to choose a sufficiently small distance between two opposing, preferably plane-parallel, viewing windows in the measuring area to allow illumination and the acquisition of optical image data with sufficiently high contrast for analysis. For example, the viewing windows may have a distance or gap of up to 5.0 mm, preferably 0.5 mm to 1.0 mm. When passing through the gap between the viewing windows, gas bubbles within the liquid may be deformed, at least in one spatial direction, if they would have a larger diameter than the gap without the external boundary.This must be taken into account in the analysis, particularly when determining the surface area of ​​the gas bubbles, for example by assuming a cylindrical shape, as described in connection with the method according to the invention.

[0108] A viewing window can be understood to mean, in particular, a transparent or see-through glass. It can also be the case that a section of the measuring area's enclosure is transparent.

[0109] It can be advantageous for the viewing window to have a reference mark or scale to compare the size of the gas bubbles and to better evaluate the optical image data with regard to bubble size. The scale can be used in the analysis, in particular, to scale the optical image data in order to obtain absolute values ​​for the size of the gas bubbles. The scale can, for example, have a line pattern, a slit pattern, and / or a grid pattern with defined intervals.

[0110] Preferably, the analysis unit is set up and designed to determine a size distribution of the gas bubbles.

[0111] Furthermore, the analysis unit can preferably be configured and designed to determine the percentage of gas in the liquid. For this purpose, the determined contact surface area and / or the size of the gas bubbles can be used in conjunction with the initial total volume of the liquid or the original fill level of the container.

[0112] It has proven advantageous to have a temperature control device to adjust the temperature of the liquid-gas mixture.

[0113] In addition to controlling the contact area, this can be advantageous for investigating and, if necessary, controlling chemical reactions. Furthermore, temperature control can ensure reproducible experimental conditions.

[0114] The temperature control device can, for example, be located in or on the mixing circuit or the container, or connected to it.

[0115] In a particularly advantageous embodiment of the device, at least one pressure sensor is provided to determine a pressure difference of the measuring circuit, in particular of the measuring range, compared to the container.

[0116] The pressure sensor or manometer can be designed as a relative pressure measuring instrument or as an absolute pressure measuring instrument, for example as a barometer.

[0117] Preferably, at least one pressure sensor is arranged in the measuring circuit or measuring area. A further pressure sensor can, in particular, be arranged in the container.

[0118] The advantages of determining the pressure difference result analogously from the advantages already described of the optional step (e) of the method according to the invention.

[0119] Preferably, a control unit is provided which is designed and configured to at least partially correct the pressure difference by adjusting the pressure in the measuring circuit.

[0120] It has proven advantageous if the flow rate of the liquid-gas mixture through the measuring circuit can be adjusted and / or if part of the liquid-gas mixture can be diverted around the measuring area via a bypass line in order to at least partially correct the pressure difference.

[0121] The flow rate is preferably adjustable or adaptable by controlling the pump, in particular the pump of the measuring circuit. The bypass line preferably has a controllable valve to divert a certain proportion of the liquid-gas mixture. The pump and / or the bypass line or the valve can preferably be controlled via the control unit.

[0122] It is advantageous if the analysis unit is set up and designed to determine an actual value of the contact surface per volume in the container from the measured value of the contact area per volume in the measuring range, whereby the pressure difference can be corrected at least partially by calculation or is already corrected.

[0123] If a real contact area per volume is to be used as the target value for the contact area per volume, it can preferably be provided that, prior to the production and measurement of the liquid-gas mixture in question, for which the above-described method and / or the above-described device is preferably used (hereinafter also referred to as the first device), the real contact area per volume is determined in the operation of the machine or plant for which the liquid is intended, i.e. under real conditions.

[0124] Preferably, a second device for measuring liquid-gas mixtures, in particular oil foams, produced during the intended use of a liquid in a plant may be provided.

[0125] The second device has at least one connection for the system containing the liquid, through which at least one sample of the liquid-gas mixture produced during the intended use of the liquid can be supplied to the second device during operation of the system, wherein a measuring circuit with a camera for recording optical image data of the liquid-gas mixture in a measuring area for measuring gas bubbles contained therein is provided.

[0126] Preferably, the second device can also include an analysis unit for analyzing the image data, wherein the analysis unit can determine a measured value of a real contact area per volume between the liquid and the gas from the total surface area of ​​the gas bubbles. Alternatively, the image data analysis can also be performed externally, preferably with the analysis unit of the first device.

[0127] The measuring circuit and / or the optional analysis unit of the second device can preferably be designed analogously to the measuring circuit or analysis unit of the first device according to the above description.

[0128] Essentially, the second device is analogous to the first device but without the mixing circuit and, if applicable, without the analysis unit. Instead of generating the liquid-gas mixture in the mixing circuit, in the case of the second device it is drawn from the plant during its normal operation.

[0129] The second device enables the measurement of the liquid-gas mixture or the foaming process under near-real-world conditions, thus allowing the determination of a so-called real contact area per volume, which relates to the intended use of the liquid. For example, if the liquid is gear oil, the foamed gear oil in the running gearbox can be measured using the second device.

[0130] The first device can preferably be designed as a stationary measuring unit. The second device can preferably be designed as a mobile measuring unit.

[0131] While the first device is particularly advantageous for the production and measurement or simulation of liquid-gas mixtures, especially oil foams, under laboratory conditions or for experimental purposes, the second device has proven to be particularly advantageous for use in the field or under real conditions.

[0132] Preferably, the first and second devices are used in combination, with the actual contact area per volume preferably being determined first using the second device. This value can then serve as the target value for the contact area per volume in the subsequent simulation using the first device. This is particularly advantageous for investigating oil oxidation or aging, allowing for realistic yet accelerated simulation.

[0133] The invention further relates to a computer program product with program code means for carrying out a method according to the invention as described above, when the program is executed on a device according to the invention or on a suitable device of the device according to the invention, in particular according to the preceding and following description.

[0134] The advantages of the computer program product according to the invention arise analogously from the advantages of the method and device according to the invention already described. Furthermore, reference is made to the preceding description analogously with regard to preferred embodiments of the computer program product according to the invention.

[0135] The device can be designed as a microprocessor. Instead of a microprocessor, any other device can be used to implement the device, for example, one or more arrangements of discrete electrical components on a printed circuit board, a programmable logic controller (PLC), an application-specific integrated circuit (ASIC), or any other programmable circuit, such as a field-programmable gate array (FPGA), a programmable logic assembly (PLA), and / or a standard computer.

[0136] It may be provided that the device is designed as an analysis unit and / or control unit, has an analysis unit and / or control unit, or is part of the analysis unit and / or control unit of the device.

[0137] It is particularly advantageous to implement the computer program product on a device which is intended for operation and control of functionality in a device for generating and measuring liquid gas mixtures and which is already implemented in this device according to the prior art.

[0138] Features described in connection with one of the subject matter of the invention, namely the inventive method, the inventive device, or the inventive computer program product, can also be advantageously implemented for the other subject matter of the invention. Likewise, advantages mentioned in connection with one of the subject matter of the invention can also be understood to relate to the other subject matter of the invention.

[0139] It should also be noted that terms such as "comprehensive", "exhibiting" or "with" do not exclude other characteristics or steps.

[0140] Furthermore, terms such as "a" or "the", which indicate a singular number of steps or features, do not exclude a plurality of features or steps - and vice versa.

[0141] In a purist embodiment of the invention, however, it may also be provided that the features introduced in the invention with the terms "comprising," "comprising," or "with" are exhaustively listed. Accordingly, one or more lists of features within the scope of the invention may be considered complete, for example, for each claim. The invention may, for instance, consist exclusively of the features mentioned in claim 1.

[0142] Exemplary embodiments of the invention are described in more detail below with reference to the drawing.

[0143] The figures each show preferred embodiments in which individual features of the present invention are combined with one another. Features of an embodiment can also be implemented independently of the other features of the same embodiment and can therefore be readily combined by a person skilled in the art to form further meaningful combinations and subcombinations with features of other embodiments.

[0144] In the figures, functionally identical elements are provided with the same reference symbols.

[0145] The figures represent the invention only as an example and in a highly schematic way.

[0146] It shows: Fig. 1 a basic representation of a possible implementation of the method according to the invention with an embodiment of the device according to the invention.

[0147] The Fig. Figure 1 shows a schematic representation of a possible implementation of a method according to the invention for producing and measuring liquid-gas mixtures, in particular oil foams. At least the following steps are provided: (a) Introducing a liquid into a container 1; (b) Transferring part of the liquid from the container 1 through a mixing circuit 2, wherein a gas is added to the liquid to produce a liquid-gas mixture, in particular with gas bubbles, after which the liquid-gas mixture is returned to the container 1; (c) Conveying a portion of the liquid-gas mixture through a measuring circuit 3, in which optical image data of the liquid-gas mixture are recorded in a measuring area 3a in order to measure gas bubbles contained therein, after which the liquid-gas mixture is returned to the container 1; (d) Analyzing the image data to determine a measurement of the contact area per volume between the liquid and the gas from the total surface area of ​​the gas bubbles; and (i) Setting a target value of the contact area per volume in the liquid-gas mixture by iteratively repeating steps (b) to (d) at least until the target value is reached.

[0148] In some cases, two or more steps of the process may occur at least partially simultaneously or overlap in time. Additional steps may also be included.

[0149] The Fig. Reference 1 also serves to disclose an embodiment of a device 4 according to the invention for generating and measuring liquid-gas mixtures, in particular oil foams. The device 4 has at least one container 1 for receiving a liquid. According to the invention, a mixing circuit 2 with an inlet 5 for supplying a gas to the liquid is provided, wherein a liquid-gas mixture, in particular with gas bubbles, can be generated by supplying the gas to the liquid. Furthermore, a measuring circuit 3 with a camera 6 for recording optical image data of the liquid-gas mixture in a measuring area 3a, for measuring gas bubbles contained therein, as well as an analysis unit 7 for analyzing the image data, is provided. The analysis unit 7 allows a measured value of a contact area per volume between the liquid and the gas to be determined from the total surface area of ​​the gas bubbles.It is intended that a target value of the contact area per volume in the liquid-gas mixture can be set by iteratively adding gas in mixing circuit 2 and verifying measurement in measuring circuit 3.

[0150] Device 4 can be designed as a test stand or test setup.

[0151] The method according to the invention can be implemented particularly advantageously using the device 4 according to the invention. This is demonstrated by the exemplary embodiment shown in the figure. Fig. Figure 1 demonstrates and is explained in more detail in the following description. However, it should be noted that the method can also be implemented analogously independently of device 4, and device 4 can also be used independently of the method.

[0152] The one in Fig. The arrows shown in the diagram are intended to symbolize a flow or current of gas or liquid, or of a liquid-gas mixture.

[0153] The method and / or device 4 is particularly suitable for generating and measuring liquid-gas mixtures where the liquid is an oil, especially a gear oil, and / or where the supplied gas contains or is oxygen. The term "liquid-gas mixture" can also refer to an oil foam.

[0154] Preferably the capacity volume, in particular the initial fill level, of the container 1 of the device 4 according to step (a) is known or determinable.

[0155] In the embodiment according to the Fig. 1. The mixing circuit 2 and the measuring circuit 3 of the device 4 are each connected to the container 1, with at least one pump 8 being provided to pump the liquid or the liquid-gas mixture from the container 1 through the mixing circuit 2 and / or the measuring circuit 3. Fig. Figure 1 shows, as an example, one pump 8 each in the mixing circuit 2 and in the measuring circuit 3.

[0156] A particularly suitable embodiment of the device 4 is one in which a lighting device 9 is provided for illuminating the liquid-gas mixture in the measuring range 3a.

[0157] Furthermore, it has proven advantageous if the measuring area 3a of the device 4 has at least one viewing window 10 and / or is transparent to allow the recording of optical image data and / or the illumination of the liquid-gas mixture through the viewing window 10.

[0158] According to the exemplary embodiment, two opposing viewing windows 10 are provided. The viewing windows 10 are in the Fig. 1 indicated by dotted lines in the boundary of the measuring area 3a. The camera 6 and the lighting device 9, in which Fig. 1 marked with symbols, are arranged in such a way that the optical image data can be recorded with the camera 6 in step (c) of the procedure in the backlight of the lighting device 9 with a view through the viewing windows 10.

[0159] In a preferred embodiment of the method, when analyzing the image data in step (d), a size distribution of the gas bubbles is determined, i.e., a frequency distribution of the diameters and surface areas of the gas bubbles. This can preferably be carried out using the analysis unit 7 of the device 4, provided it is configured and designed for this purpose.

[0160] According to an advantageous further development of the procedure, an additional step may be provided: (e) Determining a pressure difference of measuring circuit 3, in particular of measuring range 3a, compared to container 1.

[0161] If the method is carried out using the device 4, or if the device 4 is used to carry out the method, then the device 4 preferably provides at least one pressure sensor 11 for step (e) in order to determine the pressure difference. In the exemplary embodiment according to the Fig. In 1, only one pressure sensor 11 is arranged at measuring area 3a. For example, another pressure sensor could be arranged on container 1.

[0162] If the pressure difference is known, it is advantageous to at least partially correct it by adjusting the pressure in measuring circuit 3 in step (c). For this purpose, a suitably configured and designed control unit 12 can be provided for the device 4. This can be considered a physical pressure equalization.

[0163] If the pressure difference is to be physically corrected in step (c), then step (e), i.e., determining the pressure difference, is preferably carried out before the acquisition of the optical image data in step (c).

[0164] Preferably, the pressure difference can be at least partially corrected by adjusting the flow rate of the liquid-gas mixture through the measuring circuit 3 and / or through a bypass line 13 around the measuring range 3a in step (c) using the device 4. It can be provided that the flow rate in the measuring circuit 3 is adjustable by means of the pump 8. Furthermore, it can be provided that the bypass line 13 has a controllable valve to divert a portion of the liquid-gas mixture.

[0165] It has proven advantageous if, during the analysis of the image data in step (d), an actual value of the contact surface area per volume in container 1 is determined from the measured value of the contact area per volume in measuring area 3a, whereby the pressure difference is at least partially corrected computationally. This can preferably be carried out using the analysis unit 7 of the device 4, provided it is configured and designed accordingly.

[0166] If the pressure difference is to be corrected mathematically in step (d), then step (e), i.e., determining the pressure difference, can be performed during step (d). However, the pressure difference can also be determined beforehand, for example, before or during step (d). It is also possible to combine the physical and mathematical correction of the pressure difference to obtain a result for the contact area that is as pressure-independent as possible.

[0167] To adjust the target value of the contact area per volume, additional gas can be gradually added to the liquid-gas mixture, and the resulting change in the contact area can be checked against the measured value or the actual value. After the first iteration of steps (a) to (d) or (e) of the procedure, steps (b) to (d) or (e) are repeated at least until the target value is reached. This procedure was also referred to above as step (i). Device 4 can be used analogously.

[0168] The setpoint can be adjusted by comparison with the measured value in measuring circuit 3, particularly in measuring range 3a. If the measured value has been corrected mathematically with respect to the pressure difference and the actual value in container 1 has thereby been determined, then the setpoint can preferably be adjusted by comparison with the actual value.

[0169] It is advantageous if parameters such as the flow rate of the liquid or liquid-gas mixture, the shutter time of the camera 6, the time interval between the recording of two data sets of optical image data, as well as the stability of the gas bubbles which depends on the viscosity of the liquid and the size of the gas bubbles are coordinated.

[0170] The Fig. 1 further serves to disclose an embodiment of a computer program product according to the invention with program code means to carry out the method according to the preceding description when the program is executed on the device 4 according to the preceding description or on a suitable device 14 of the device 4 according to the invention.

[0171] The analysis unit 7, the control unit 12, and the device 14 are in the Fig.Figure 1 is only shown schematically. It may be provided that the device 14 is configured as an analysis unit 7 and / or control unit 12, includes the analysis unit 7 and / or control unit 12, or is part of the analysis unit 7 and / or control unit 12. Reference symbol list: 1 container 2 Mixing circuit 3 measuring circuit 3a Measuring range 4 Device 5 Admission 6 cameras 7 analysis units 8 pump 9 Lighting equipment 10 viewing windows 11 Pressure sensor 12 Control unit 13 Bypass line 14. Establishment QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 10,809,202 B2

[0006] JP 6558315 B2

[0006]

Claims

[1] Method for producing and measuring liquid-gas mixtures, in particular oil foams, comprising at least the following steps: (a) Putting a liquid into a container (1); (b) Pumping a portion of the liquid from the container (1) through a mixing circuit (2), wherein a gas is added to the liquid to produce a liquid-gas mixture, in particular with gas bubbles, after which the liquid-gas mixture is returned to the container (1); (c) Conveying a portion of the liquid-gas mixture through a measuring circuit (3), wherein optical image data of the liquid-gas mixture are recorded in a measuring area (3a) in order to measure gas bubbles contained therein, after which the liquid-gas mixture is returned to the container (1); (d) Analyzing the image data to determine a measurement of the contact area per volume between the liquid and the gas from the total surface area of ​​the gas bubbles; and (i) Setting a target value of the contact area per volume in the liquid-gas mixture by iteratively repeating steps (b) to (d) at least until the target value is reached. [2] Method according to claim 1, wherein the liquid is an oil, in particular a gear oil and / or the supplied gas contains oxygen. [3] Method according to claim 1 or 2, wherein, in step (d) the analysis of the image data, a size distribution of the gas bubbles is determined. [4] Method according to claim 1, 2 or 3, wherein an additional step is provided: (e) Determining a pressure difference of the measuring circuit (3), in particular of the measuring range (3a), compared to the container (1). [5] Method according to claim 4, wherein the pressure difference is at least partially corrected by adjusting the pressure in the measuring circuit (3) in step (c). [6] Method according to claim 4 or 5, wherein the pressure difference is at least partially corrected in step (c) by adjusting a flow rate of the liquid-gas mixture through the measuring circuit (3) and / or through a bypass line (13) around the measuring range (3a). [7] Method according to claim 4, 5 or 6, wherein, in step (d) the image data is analyzed, an actual value of the contact surface per volume in the container (1) is determined from the measured value of the contact area per volume in the measuring area (3a), wherein the pressure difference is at least partially corrected computationally. [8] Device (4) for producing and measuring liquid-gas mixtures, in particular oil foams, at least comprising a container (1) for receiving a liquid, characterized by, that a mixing circuit (2) with an inlet (5) for supplying a gas into the liquid is provided, wherein a liquid-gas mixture, in particular with gas bubbles, can be produced by supplying the gas into the liquid, wherein a measuring circuit (3) with a camera (6) for recording optical image data of the liquid-gas mixture in a measuring area (3a) for measuring gas bubbles contained therein, and an analysis unit (7) for analyzing the image data is provided, wherein a measured value of a contact area per volume between the liquid and the gas can be determined from the total surface area of ​​the gas bubbles by the analysis unit (7), and wherein a target value of the contact area per volume in the liquid-gas mixture can be set by iterative supply of gas in the mixing circuit (2) and verifying measurement in the measuring circuit (3). [9] Device (4) according to claim 8, characterized bythat the liquid is an oil, in particular a gear oil, and / or that the supplied gas contains oxygen. [10] Device (4) according to claim 8 or 9, characterized by , that the mixing circuit (2) and the measuring circuit (3) are each connected to the container (1), wherein at least one pump (8) is provided to pump the liquid or the liquid-gas mixture from the container (1) through the mixing circuit (2) and / or the measuring circuit (3). [11] Device (4) according to claim 8, 9 or 10, characterized by , that a lighting device (9) is provided for illuminating the liquid-gas mixture in the measuring area (3a). [12] Device (4) according to claim 11, characterized by , that the lighting device (9) is designed and configured to illuminate the liquid-gas mixture in the measuring area (3a) with collimated light. [13] Device (4) according to any one of claims 8 to 12, characterized by, that the measuring area (3a) has at least one viewing window (10) and / or is transparent to allow the acquisition of optical image data and / or the illumination of the liquid-gas mixture through the viewing window (10). [14] Device (4) according to any one of claims 8 to 13, characterized by , that the analysis unit (7) is set up and designed to determine a size distribution of the gas bubbles. [15] Device (4) according to any one of claims 8 to 14, characterized by , that at least one pressure sensor (11) is provided to determine a pressure difference of the measuring circuit (3), in particular of the measuring range (3a), compared to the container (1). [16] Device (4) according to claim 15, characterized by , that a control unit (12) is provided which is set up and designed to at least partially correct the pressure difference by adjusting the pressure in the measuring circuit (3). [17] Device (4) according to claim 15 or 16, characterized by , that the flow rate of the liquid-gas mixture through the measuring circuit (3) can be adjusted and / or a part of the liquid-gas mixture can be diverted around the measuring area (3a) via a bypass line (13) in order to at least partially correct the pressure difference. [18] Device (4) according to claim 15, 16 or 17, characterized by , that the analysis unit (7) is set up and designed to determine an actual value of the contact surface per volume in the container (1) from the measured value of the contact area per volume in the measuring area (3a), wherein the pressure difference is at least partially computationally correctable. [19] Computer program product comprising program code means for carrying out a method according to any one of claims 1 to 7 when the program is executed on a device (4) according to any one of claims 8 to 18.

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