Device and method for characterizing fluid flows

Abstract

The invention relates to a device for characterizing fluid flows, comprising a flow channel (1) designed to allow throughflow of the at least one fluid flow (2). Moreover, at least one radiation source (4) arranged in the cross section of the flow channel (1) is provided, the radiation source (4) being media-tightly surrounded by a first housing (3), such that there is no direct mechanical contact between the radiation source (4) and the fluid flow (2). In addition, at least one detector (5) designed to detect emitted radiation (6) from the radiation source (4) is arranged, the at least one detector (5) being positioned on the surface of the flow channel (1) facing away from the fluid flow (2).

Description

[0001] Device and method for characterizing fluid flows

[0002] The invention relates to a device and a method for characterizing fluid flows.

[0003] Precise characterization and monitoring of fluid flows is used in many different areas of technology, for example, to detect changes in flow behavior caused by impurities or defects or to ensure defined process conditions. Therefore, a wide variety of devices and methods exist for characterizing fluid flows.

[0004] One possibility is radiographic flow meters, so-called densitometers. In these, the (gamma) radiation source and detector are arranged opposite each other outside the pipe cross-section to be examined. Densitometers with isotope sources suffer primarily from low data rates due to low quantum flux, which is limited by the complete penetration of the object cross-section. The vast majority of such measuring devices use only a single collimated measuring beam and a single detector (so-called pencil-beam setup). It is assumed that the density distribution of the flow recorded along this beam is representative of the entire cross-section.

[0005] This represents a drastic simplification, resulting in a significant reduction in information content. The radiation used as a signal carrier must penetrate not only the pipe walls but also the entire cross-section of the flow under investigation (in the best case, completely filled with a fluid). This results in a narrow dynamic range for measuring subtle structural changes, such as a single bubble. In addition, there is the natural limitation of the quantum flux due to the radioactive decay of the isotope source. Both factors lead to a limitation of the measurement speed or data rate due to the necessary minimum integration times at the detector to achieve a reasonable SNR (signal-to-noise ratio).

[0006] A few X-ray densitometers are also known, some of which also feature multiple detectors. While these achieve significantly higher data rates due to the inherently higher photon flux, they also suffer from the problem of material penetration across the entire cross-section of the measurement object, which leads to an increase in the accelerating voltage and thus necessitates heavy and bulky system designs that must also comply with stringent radiation protection regulations. As a result, these systems are very energy- and cost-intensive both in production and operation.

[0007] Furthermore, conventional tomographic measurement techniques using X-rays are maintenance-intensive and technically complex to construct due to the use of moving parts. Furthermore, these methods require a significant amount of time for post-processing (image reconstruction). Furthermore, alternative electron beam CTs (CT - computed tomography) without moving components are complex to handle and, due to the use of high accelerating voltages and the necessary penetrability of the radiation, require considerable effort in terms of radiation protection. The inevitably high photon energy also leads to limited contrast between the phases under investigation (usually gas / liquids). Furthermore, pencil beam densitometers only allow very vague statements regarding the phase distribution or liquid holdup.

[0008] In the prior art, these problems are attempted to be solved, for example, by WO 2010034584 A1. Here, a flow sensor based on an organic photodetector is integrated into a flow-guiding system. The integration is provided in the wall of the flow-guiding system, so that the photodetector is part of the microfluidic channel. The integrated photodetector detects changes in light intensity depending on the liquid column. Ambient light is sufficient as a light source. The invention is specifically designed for microchannel structures; a two-phase measurement in larger pipe cross-sections, as typically encountered in process engineering, is therefore impossible. The fundamental disadvantage of this invention is that this solution requires a high level of design effort and also makes flexible adaptation of the device to different flow tasks difficult. Furthermore, the information gained is quite limited, since, for example,a gas bubble represents a total absorber for light as an information carrier, which is why structures behind it cannot be detected along the scanning light beam.

[0009] The present invention is therefore based on the object of providing a device and a method for characterizing fluid flows, whereby a fast and high-resolution characterization of fluid flows with a high information content is enabled, while at the same time the integration effort is reduced.

[0010] This object is achieved according to the invention by a device for characterizing fluid flows according to claim 1 and by a method for characterizing fluid flows according to claim 10. Advantageous embodiments are described in the dependent claims.

[0011] A device for characterizing fluid flows comprises a flow channel configured for the at least one fluid flow to flow through. Furthermore, at least one radiation source is provided, which is arranged in the cross-section of the flow channel. The radiation source is enclosed in a media-tight manner by a first housing, so that there is no direct mechanical contact between the radiation source and the fluid flow. Furthermore, at least one detector configured to detect radiation emitted by the radiation source is integrated, wherein the at least one detector is arranged on the surface of the flow channel facing away from the fluid flow.

[0012] The fluid flow to be characterized is not limited to single-phase fluid flows, but can consist of a mixture of different phases, i.e., be multiphase. Typically, the flow channel is a tubular flow channel. A tubular, in particular a cylindrical, flow channel is understood here to be a channel with at least one inlet opening and at least one outlet opening through which the fluid is admitted or discharged. In this case, the fluid flow also has a defined flow direction, which is parallel to the normal of the cross-section of the typically tubular flow channel, thus flowing from the inlet opening to the outlet opening.

[0013] Preferably, the at least one radiation source is arranged centrally in the cross-section of the flow channel. The term "centrally arranged" means that the distances from the radiation source to the inner surface of the flow channel in the cross-section of the flow channel are equal on all sides or approximately equal within error tolerances during installation. In other words, the radiation source is arranged in the middle, i.e., at the center point of the cross-section of the flow channel. It can also be provided to design the radiation source and arrange it in the cross-section of the flow channel in such a way that (during operation) the radiation source emits radiation perpendicular to the flow direction.

[0014] Furthermore, "media-tight" means that the first housing prevents direct exchange processes, including chemical reactions and diffusion processes, from taking place between the radiation source and the fluid flow. This eliminates any contamination of the fluid flow.

[0015] In addition, the "surface facing away from the fluid flow" should be understood as the surface located on the outside of the flow channel.

[0016] Due to the preferably central arrangement of the radiation source and the associated reduced transmission length, the device according to the invention enables the use of comparatively low radiation energies, thus enabling better phase contrast and correspondingly reducing radiation protection requirements. Due to the preferably central arrangement, the transmission length is only half the diameter of the flow channel and thus also half the transmission length in conventional devices. Furthermore, the required radiation energy is also reduced by the fact that the wall of the flow channel only needs to be irradiated once.

[0017] Preferably, the first housing is made of a material that only slightly attenuates the radiation used, for example, absorbing a maximum of 10 percent of the originally present radiation, so that as much of the radiation energy emitted with the radiation as possible penetrates the fluid flow. Furthermore, the device is essentially maintenance-free, as no mechanically moving parts are formed. This further reduces the operating costs of the device. The design of the first housing as a tubular channel open on one side is also preferred.

[0018] In addition, the first housing can extend through an opening made in the wall of the flow channel, whereby a media-tight separation between the interior of the flow channel and the interior of the first housing is ensured between the flow channel and the first housing.

[0019] The fact that the first housing can be understood as a separate structural element ensures that flexible replacement is possible. This is particularly advantageous when the radiation source needs to be replaced or the first housing needs to be replaced. Thus, the device can be flexibly adapted to various characterization tasks. This design is particularly suitable for retrofitting existing flow channels to accommodate the device. This allows for easy integration of the device into existing system concepts.

[0020] Furthermore, the first housing can also be designed as an inwardly shaped bulge of the flow channel.

[0021] By forming the first housing as part of the flow channel, it is easily ensured that the interior of the first housing and the interior of the flow channel are separated from each other in a media-tight manner. The first housing is formed directly during the manufacture of the flow channel. The term "inwardly formed bulge of the flow channel" refers in particular to a one-piece bulge of the flow channel material into the interior of the flow channel. This means that the flow channel wall has a bulge such that the flow channel wall extends partially or regionally into the flow channel. This design is particularly suitable where a new flow channel is to be implemented, since the geometry of the channel (including the bulge) can be defined before the flow channel is manufactured.This allows for a one-piece production of the flow channel with the provided bulge forming the first housing. A finger-shaped bulge can be provided particularly preferably. By forming the first housing as a bulge of the flow channel, the costs incurred with subsequent integration can be avoided. Furthermore, the first housing can be designed with a streamlined shape. A "streamlined shape" refers to a special shape of flow-around bodies, which is characterized by a low drag coefficient X, which is typically less than 0.5 (preferably 0.055 < X < 0.5, in particular 0.055 < X < 0.3, particularly preferably 0.055 < X < 0.065). A rounded head section is characteristic of the streamlined shape.The one-sided rounded shape of the first housing keeps the turbulence caused in the fluid flow as low as possible, so that the recorded measurement data is not distorted.

[0022] In addition, the first housing can be connected to at least one second housing arranged outside the flow channel, in which at least one electron beam generator and / or at least one source container is formed.

[0023] By locating the electron beam generator or source container outside the flow channel, the operational reliability of the system and the interchangeability of the individual components are improved through easier accessibility. "Connected" in this context means that the interior of the first housing is accessible via the second housing. This means that a continuous, barrier-free connection can be provided between the first housing and the second housing.

[0024] Furthermore, a plurality of radiation sources can be formed in the first housing. The arrangement of a plurality of radiation sources is not limited to radiation sources of the same type, but should also include arrangements of a plurality of radiation sources of different types. The arrangement of a plurality of radiation sources with different energy potentials is preferred, enabling dual-energy operation. In other words, at least one radiation source with a low-energy component and at least one radiation source with a high-energy component can be provided. The energy component of the first radiation source can be lower than the energy component of the second radiation source.By arranging several radiation sources with different energy levels, a more precise characterization can be achieved, since the radiation sources can be better adapted to the phases present in the fluid flow.

[0025] In addition, at least two first housings can be arranged one behind the other parallel to the flow direction of the fluid flow.

[0026] In this case, a defined distance x can be formed between the first housings in a direction parallel to the flow direction of the fluid flow.

[0027] By arranging them one behind the other (viewed from a direction parallel to the fluid flow direction), additional velocity measurements can be performed. This further increases the information content about the fluid flow properties that can be obtained with the device.

[0028] In addition, a large number of detectors can form an almost completely closed detector ring around the flow channel.

[0029] Here, "almost completely closed" means that the flow channel is continuously covered with detectors along its entire circumference on the outer surface of the flow channel. This enables simultaneous readout of the radiation detectors arranged at different circumferential positions. This allows simultaneous detection of the radiation attenuation for several beam directions, enabling characterization with high temporal and spatial resolution in a straightforward manner and without complex image reconstruction.

[0030] In addition, the radiation source can be designed as an isotope source, an X-ray source or a laser source.

[0031] By selecting different radiation sources, the device can be easily adapted to different characterization tasks depending on the existing fluid flow, the geometry of the flow channel used and the existing process conditions in order to use the optimal radiation source for the respective characterization task.

[0032] Furthermore, the first housing can be formed in an angular range of 5° up to and including 175°, in particular from 45° to 135° with respect to the flow direction of the fluid flow.

[0033] By precisely adjusting the angle of the first housing, the ideal flow volume of the fluid flow can be adjusted with regard to the characterization task at hand. This minimizes the influence of the first housing on the change in fluid flow.

[0034] In a method for characterizing fluid flows, a fluid flow flows through a flow channel. The fluid flow also flows around at least one radiation source arranged in a first housing, the radiation source being positioned in the cross-section of the flow channel. The radiation source emits radiation that passes through the first housing, then through the fluid flow, and then through the wall of the flow channel. The radiation is then detected by at least one detector arranged on the surface of the flow channel facing away from the fluid flow.

[0035] This method enables a fast, high-spatial-resolution densitometric measurement technique in which the fluid flow under investigation is scanned in cross-section, typically perpendicular to the flow direction, from its center in all directions. This represents a significant gain in information compared to conventional pencil-beam densitometers.

[0036] In addition, information about the fluid flow can be obtained directly from the detected radiation. In particular, the flow pattern, flow rate, particle concentration, and / or flow velocity can be determined directly. This means that this information can be obtained from the measurement data, ie, from the detected radiation, without feature reconstruction, as is necessary, for example, in tomography procedures.

[0037] The method is designed to use the device already described, ie the device can be used to carry out the described method.

[0038] Embodiments of the device are illustrated in the drawings and are described below with reference to Figures 1 and 2. Recurring features are provided with identical reference numerals.

[0039] They show:

[0040] Fig. 1 is a schematic drawing of the device in cross section perpendicular to the direction of fluid flow and

[0041] Fig. 2 is a schematic drawing of the device in cross section parallel to the flow direction of the fluid flow.

[0042] Fig. 1 discloses a device for characterizing fluid flows with a radiation source 4, which is arranged centrally in a tubular flow channel 1 and emits radiation 6, which radiates through the fluid flow 2 and is detected by detectors 5 arranged on the outer surface of the flow channel 1. The radiation source 4 is enclosed in a media-tight manner by a first housing 3 and connected to a second housing 7 formed outside the flow channel 1. In this embodiment, the device is to be understood as a radiographic flow sensor.

[0043] The first housing 3 projects into the interior of the flow channel 1 so that the fluid flow 2 flows around it. This ensures that the radiation source 4 formed in the first housing 3 is almost completely, i.e. indirectly, surrounded by the fluid flow 2 on almost all sides. The exception is the direction in which the first housing 3 runs and is connected to the second housing 7 through the flow tube 1. In this exemplary embodiment, the first housing 3 is designed as an independent component which projects into the flow channel 1 through an opening in the flow channel 1. The first housing 3 and / or the second housing 7 are connected to the flow channel 1 in a media-tight manner so that the opening of the flow channel 1 is closed in a media-tight manner. Alternatively, the first housing 3 can also be designed as a bulge of the flow channel 1 into the interior of the flow channel 1.This means that the first housing 3 and the flow channel 1 can be formed as a single piece. In other words, the channel wall of the flow channel 1 can be bulged inward or into the interior of the flow channel 1 in sections such that the first housing 3 is formed.

[0044] The formed fluid flow 2 is a two-phase flow comprising a liquid and a solid phase. Water, for example, can be used as the liquid phase, although any other liquid or gaseous fluid can also be used. In this exemplary embodiment, the solid phase represents impurities that are not soluble in the liquid phase. Here, too, any combination of a liquid or gaseous fluid in combination with a second liquid, gaseous, or solid phase is generally considered. The characterization of multiphase fluid flows 2 can also be carried out without difficulty.

[0045] This arrangement makes it possible to completely irradiate the fluid flow 2, i.e., in all directions simultaneously, in the cross-section of the fluid flow 2 perpendicular to the flow direction. The radiation 6 emitted in all directions is then detected by the detectors 5 arranged on the outside of the flow channel 1 and subsequently evaluated. This represents a significant gain in information compared to known pencil beam densitometers, both due to the multiple measurement channels and due to increased phase contrast with high temporal resolution.

[0046] In this exemplary embodiment, a first housing 3 in the form of a source tube is inserted obliquely into the flow channel 1 to be examined, the rounded tip of which is located in the center of the flow channel 1. The radiation source 4 is inserted into this tip, either in the form of an encapsulated isotope source (e.g., Co60), or a bremsstrahlung target is built into the tip, which is bombarded with an electron beam from an obliquely mounted electron beam gun. The first housing 3 and the second housing 7 can be made of an identical material, but different materials can also be used. For example, titanium, aluminum, stainless steel, or a carbon fiber reinforced plastic can be used.

[0047] The acceleration voltage can be adjusted accordingly to the substances present in the fluid flow 2 under investigation (and their attenuation behavior). Several detectors 5 are arranged in a circle outside the flow channel 1. The circular plane is aligned with the tip of the first housing 3. The detectors 5 can be read out in parallel, allowing radiographic attenuation values ​​to be recorded along beam fans distributed over 360° of the cross-section of the flow channel 1 perpendicular to the flow direction.

[0048] The cycle time of this radiography depends on the flux of the radiation source 4 and, when using X-rays, can be up to several kilohertz, thus achieving a time resolution in the millisecond range. By reducing the measuring beam length to less than half the secant from the center to the detectors 5, less material needs to be penetrated, which reduces the photon energy and, in turn, increases the contrast within the phases under investigation.

[0049] Furthermore, radiation protection requirements are lower, which significantly increases the acceptance of such a device in industrial environments. In known radiographic measuring systems with a radiation source 4 located outside the flow channel 1, each scanning beam experiences a different cross-sectional length and therefore a different object attenuation. This leads to varying sensitivity across the cross-section.

[0050] The present invention overcomes this significant disadvantage, as each scanning beam has the same geometry and therefore the same reference attenuation. Furthermore, simply by reducing the scanning length to less than d / 2 (half the diameter of the flow channel 1), a higher sensitivity is achieved, which is the same for all measuring channels or detectors 5. This azimuthal division of the measuring cross-section (cross-section of the flow channel 1 perpendicular to the flow direction of the fluid flow 2) also results in a significant increase in information compared to conventional fan beam densitometers. For example, with the arrangement according to the invention, it would be possible to directly determine whether a ring flow or a stratified flow is present by evaluating the two vertically opposed detectors 5. The quantification accuracy for the liquid phase fraction is thus significantly increased.

[0051] Fig. 2, like Fig. 1, shows an embodiment of the device according to the invention, with the cross-section of the device being shown parallel to the flow direction of the fluid flow 2. This again illustrates that the entire cross-section of the flow channel 1 is irradiated by the radiation source 1 through the device, with the maximum radiation length being only half the diameter of the flow channel 1. Thus, despite a significant reduction in the radiation length, full radiation penetration is still ensured.

[0052] The device thus enables the temporally and spatially high-resolution measurement of the phase distribution in the cross-section of a flow channel 1 perpendicular to the flow direction of the fluid flow 2. It requires no moving parts and is therefore maintenance-free for field use. The arrangement exceeds the performance of known radiological flow meters in terms of measurement speed and spatial resolution. By arranging the radiation source 4 in the center of the cross-section of the flow channel 1 under investigation, the energy of the radiation 6 can be significantly reduced compared to conventional radiographic methods. The comparatively low photon energy provides better contrast between the phases of the fluid flow 2 involved and facilitates radiation protection.

[0053] Furthermore, tomographic image reconstruction can be dispensed with, thus achieving direct output of the desired flow pattern, flow rate, and measured values. This makes such a device suitable for direct process control without time-consuming post-processing. Its maintenance-free design and ease of use make the device particularly well-suited for industrial applications. Furthermore, Fig. 2 clearly shows that the radiation source 4 is not in direct contact with the fluid flow 2, although it is arranged centrally in the fluid flow 2. The design of the first housing 3, in this case as a measuring tube, enables the introduction of the radiation source 4 in a simple manner. The rounded shape of the first housing 3 on one side keeps the turbulence caused in the fluid flow 2 as low as possible.Thus, the first housing 3 is streamlined to prevent falsification of the measured data. A "streamlined shape" refers to a special shape of flow-around bodies characterized by a low drag coefficient (preferably 0.055-0.065). A rounded head section is characteristic of the streamlined shape. Furthermore, the media-tightness of the first housing 3 ensures that no contamination of the fluid flow 2 by the radiation source 4 occurs.

Claims

Patent claims 1. A device for characterizing fluid flows, comprising: a flow channel (1) designed to have at least one fluid flow (2) flowing through it, at least one radiation source (4) arranged in the cross-section of the flow channel (1), wherein the radiation source (4) is surrounded by a first housing (3) in a media-tight manner so that there is no direct mechanical contact between the radiation source (4) and the fluid flow (2), and at least one detector (5) designed to detect radiation (6) emitted by the radiation source (4), wherein the at least one detector (5) is arranged on the surface of the flow channel (1) facing away from the fluid flow (2).

2. Device for characterizing fluid flows according to claim 1, characterized in that the first housing (3) extends through an opening made in the wall of the flow channel (1), wherein a media-tight separation between the interior of the flow channel (1) and the interior of the first housing (3) is ensured between the flow channel (1) and the first housing (3).

3. Device for characterizing fluid flows according to claim 1, characterized in that the first housing (3) is designed as an inwardly shaped bulge of the flow channel (1), in particular finger-shaped.

4. Device for characterizing fluid flows according to one of the preceding claims, characterized in that the first housing (3) is streamlined.

5. Device for characterizing fluid flows according to one of the preceding claims, characterized in that the first housing (3) is connected to at least one second housing (7) arranged outside the flow channel (1), in which at least one electron beam generator and / or at least one source container is formed.

6. Device for characterizing fluid flows according to one of the preceding claims, characterized in that several radiation sources (4) are formed in the first housing (3).

7. Device for characterizing fluid flows according to one of the preceding claims, characterized in that at least two first housings (3) are arranged one behind the other parallel to the flow direction of the fluid flow (2).

8. Device for characterizing fluid flows according to one of the preceding claims, characterized in that a plurality of detectors (5) form an almost completely closed detector ring around the flow channel (1).

9. Device for characterizing fluid flow according to one of the preceding claims, characterized in that the radiation source (4) is designed as an isotope source or X-ray source or laser source.

10. Device for characterizing fluid flows according to one of the preceding claims, characterized in that the first housing (3) is formed in an angular range of 5° up to and including 175°, in particular from 45° to 135° with respect to the flow direction of the fluid flow (2).

11. Method for characterizing fluid flows, in which a fluid flow (2) flows through a flow channel (1) and the fluid flow (2) flows around at least one radiation source (4) arranged in a first housing (4), wherein the radiation source (4) is arranged in the cross-section of the flow channel (1) and the radiation source (4) emits radiation (6) which passes through the first housing (3), through the fluid flow (2) and through the wall of the flow channel (1) and the radiation (6) is then detected by at least one detector (5) arranged on the surface of the flow channel (1) facing away from the fluid flow (2).

12. A method for characterizing fluid flows according to claim 11, characterized in that information about the fluid flow (2), in particular about the flow shape, the flow rate, the particle concentration and / or the flow velocity, is obtained directly from the detected radiation.

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