Device and method for characterizing fluid flows

Abstract

A device for characterizing fluid flows comprises a flow channel (1) configured to allow the at least one fluid flow (2) to flow through it. Furthermore, at least one radiation source (4) is provided, arranged in the cross-section of the flow channel (1), wherein the radiation source (4) is enclosed 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). Additionally, at least one detector (5), configured to detect emitted radiation (6) from the radiation source (4), is arranged, wherein the at least one detector (5) is positioned on the surface of the flow channel (1) facing away from the fluid flow (2).

Description

[0001] The invention relates to a device and a method for characterizing fluid flows.

[0002] Precise characterization and monitoring of fluid flows is used in many different areas of engineering, 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.

[0003] One option is radiographic flow meters, also known as densitometers. In this method, the (gamma) radiation source and detector are positioned outside the pipe cross-section under investigation, so that they are opposite each other. Densitometers with isotope sources suffer primarily from low data rates due to a low quantum flux, which is limited by the complete penetration of the object's cross-section. The vast majority of such measuring devices use only a single collimated beam and a single detector (so-called pencil-beam setup). This assumes that the density distribution of the flow detected along this beam is representative of the entire cross-section.

[0004] 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 most extreme case, completely filled with fluid). This leads to a limited dynamic range for measuring minute structural changes, such as those of a single bubble. Furthermore, the quantum flux is naturally limited by the radioactive decay of the isotope source. Both of these factors limit the measurement speed and data rate due to the minimum integration times required at the detector to achieve a reasonable signal-to-noise ratio (SNR).

[0005] A few X-ray densitometers are also known, some of which have multiple detectors. While these achieve significantly higher data rates due to their inherently higher photon flux, they also suffer from the problem of the entire cross-section of the object being measured being penetrated. This leads to an increase in the acceleration voltage and thus necessitates heavy and bulky system designs that must also comply with stringent radiation protection regulations. Consequently, these systems are very energy-intensive and costly to produce and operate.

[0006] Furthermore, established tomographic measurement techniques using X-rays are maintenance-intensive and technically complex to design due to the use of moving parts. These methods also require significant time for post-processing (image reconstruction). Alternative electron beam CT (CT - computed tomography) systems without moving components are complex to handle and, due to the use of high accelerating voltages required for the necessary radiation penetration, can only be used with considerable effort from a radiation protection perspective. The inevitably high photon energy also leads to limited contrast between the phases being examined (typically gas / liquid). Additionally, pin-beam densitometers only provide a very vague indication of the phase distribution or liquid holdup.

[0007] In the prior art, these problems are addressed, for example, by WO 2010 034 584 A1. This involves integrating a flow sensor based on an organic photodetector into a flow-carrying system. The integration is provided in the wall of the flow-carrying 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; two-phase measurement in larger pipe cross-sections, as typically found in process engineering, is therefore impossible. A disadvantage of this invention is that this solution requires a high degree of design complexity and also makes flexible adaptation of the device to different flow conditions difficult. Furthermore, the information gained is quite limited, since, for example,A gas bubble acts as a total absorber for light as an information carrier, which is why underlying structures along the scanning light beam cannot be detected.

[0008] The present invention therefore aims to provide a device and a method for characterizing fluid flows, enabling fast and high-resolution characterization of fluid flows with a high information content while simultaneously reducing the integration effort.

[0009] This problem is solved 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.

[0010] A device for characterizing fluid flows comprises a flow channel configured to allow the at least one fluid flow to pass through it. Furthermore, at least one radiation source is provided, arranged within the cross-section of the flow channel, wherein the radiation source is enclosed by a first housing in a media-tight manner, so that there is no direct mechanical contact between the radiation source and the fluid flow. Finally, at least one detector, configured to detect emitted radiation from 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.

[0011] 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., it can be multiphase. Typically, the flow channel is a tubular flow channel. A tubular, and 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 introduced or discharged. Furthermore, the fluid flow exhibits a defined flow direction, which is parallel to the normal of the cross-section of the typically tubular flow channel, thus resulting in a flow from the inlet opening to the outlet opening.

[0012] Preferably, the at least one radiation source is centrally located within the cross-section of the flow channel. The term "centrally located" means that the distances from the radiation source to the inner surface of the flow channel are equal in all directions, or approximately equal within tolerances of installation. In other words, the radiation source is located in the center, i.e., at the midpoint of the cross-section of the flow channel. It is also possible to design and position the radiation source within the cross-section of the flow channel such that (during operation) the radiation source emits radiation perpendicular to the flow direction.

[0013] Furthermore, "media-tight" refers to the property that the first housing prevents direct exchange processes, including chemical reactions and diffusion processes, between the radiation source and the fluid flow. This eliminates impurities or contamination of the fluid flow.

[0014] Additionally, the term "surface facing away from the fluid flow" shall be understood to mean the surface located on the outside of the flow channel.

[0015] Due to the preferably central arrangement of the radiation source and the associated reduced transmission length, the device according to the invention allows the use of comparatively low radiation energies, thereby enabling better phase contrast and correspondingly lower radiation protection requirements. Because of the preferably central arrangement, the transmission length is only half the diameter of the flow channel and thus also half the transmission lengths in conventional devices. Furthermore, the required radiation energy is also reduced because the wall of the flow channel only needs to be penetrated once.

[0016] 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 original radiation, so that as much of the radiation energy as possible passes through the fluid flow. Furthermore, the device is essentially maintenance-free, as it has no mechanically moving parts. This further reduces the operating costs of the device. The design of the first housing as a tubular channel open at one end is also preferred.

[0017] Furthermore, the first housing can pass through an opening in the wall of the flow channel, ensuring a media-tight separation between the interior of the flow channel and the interior of the first housing.

[0018] Because the first housing can be considered a separate structural element, flexible replacement is ensured. This is particularly advantageous when the radiation source needs to be changed or the first housing replaced. Thus, the device can be flexibly adapted to various characterization tasks. This design is especially suitable for retrofitting existing flow channels to accommodate the device. Therefore, simple integration of the device into existing system designs is possible.

[0019] Furthermore, the first housing can also be designed as an inwardly shaped bulge of the flow channel.

[0020] 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 media-tightly separated. The first housing is formed directly during the manufacturing of the flow channel. This design is particularly advantageous where a new flow channel is to be implemented. By forming the first housing as a bulge of the flow channel, the costs incurred during subsequent integration can be avoided.

[0021] Furthermore, 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.

[0022] By positioning the electron beam generator or source container outside the flow channel, the operational reliability of the system and the replaceability of individual components are improved through easier accessibility. In this context, "connected" means that the interior of the first housing is accessible via the second housing. This implies that a continuous, barrier-free connection between the first and second housings can be provided.

[0023] Furthermore, multiple radiation sources can be integrated into the first housing. The arrangement of multiple radiation sources is not limited to sources of the same type, but can also include arrangements of different types. Preferably, multiple radiation sources with differing energy potentials are used, 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.

[0024] By arranging several radiation sources with different energy levels, a more precise characterization can be achieved, as the radiation sources can be better adapted to the phases present in the fluid flow.

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

[0026] Here, a defined distance x can be established between the first housings in a direction parallel to the fluid flow. By arranging them one behind the other (viewed from the direction parallel to the fluid flow), additional velocity measurements can be performed. This further increases the amount of information about the fluid flow properties that can be obtained from the device.

[0027] Furthermore, a large number of detectors can form an almost completely closed detector ring around the flow channel.

[0028] In this context, "almost completely closed" means that the flow channel is continuously covered with detectors along its entire circumference on the outer surface of the channel. This allows for the simultaneous reading of radiation detectors located at different circumferential positions. This enables the simultaneous measurement of radiation attenuation for multiple transmission directions, thus facilitating characterization with high temporal and spatial resolution simply and without complex image reconstruction.

[0029] Furthermore, the radiation source can be designed as an isotope source, an X-ray source, or a laser source.

[0030] By selecting different radiation sources, the device can be easily adapted to different characterization tasks depending on the fluid flow, the geometry of the flow channel used, and the process conditions, in order to use the optimal radiation source for the respective characterization task.

[0031] Furthermore, the first housing can be designed in an angular range of 5° to and including 175°, in particular from 45° to 135° with respect to the direction of flow of the fluid flow.

[0032] By precisely aligning the angle of the first housing, the ideal flow volume of the fluid flow can once again be set with regard to the present characterization task. This minimizes the influence of the first housing on changes in the fluid flow.

[0033] In a method for characterizing fluid flows, a fluid flow passes through a flow channel. The fluid flow also passes around at least one radiation source arranged in a first housing, the radiation source being located 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 located on the surface of the flow channel facing away from the fluid flow.

[0034] This method enables a fast, high-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 established pin-beam densitometers.

[0035] The method is designed to use the device already described, i.e., the described method can be carried out with the device.

[0036] Exemplary embodiments of the device are shown in the drawings and are described below with reference to the Fig. 1 and Fig. 2 described. Recurring features are provided with identical reference symbols.

[0037] They show: Fig. 1 a schematic drawing of the device in cross-section perpendicular to the direction of fluid flow and Fig. 2 a schematic drawing of the device in cross-section parallel to the direction of fluid flow.

[0038] Fig. Figure 1 discloses a device for characterizing fluid flows with a radiation source 4, which is centrally arranged in a tubular flow channel 1 and emits radiation 6 that 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 first housing 3 and connected to a second housing 7 located outside the flow channel 1. In this embodiment, the device is to be understood as a radiographic flow sensor.

[0039] The first housing 3 projects into the interior of the flow channel 1, so that it is surrounded by the fluid flow 2. This ensures that the radiation source 4 formed in the first housing 3 is almost completely, i.e., almost all around indirectly, surrounded by the fluid flow 2. The only exception is the direction in which the first housing 3 runs and is connected to the second housing 7 through the flow tube 1.

[0040] The fluid flow 2 described is a two-phase flow comprising a liquid and a solid phase. Water is used as an example of the liquid phase, although any other liquid or gaseous fluid can also be used. In this embodiment, the solid phase represents impurities that are insoluble in the liquid phase. Here, too, any combination of liquid or gaseous fluid with a second liquid, gaseous, or solid phase is fundamentally possible. The characterization of multiphase fluid flows 2 can also be carried out without difficulty.

[0041] This arrangement makes it possible to completely irradiate the fluid flow 2 perpendicular to the flow direction in its cross-section, i.e., in all directions simultaneously. 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 pin-beam densitometers, firstly due to the many measurement channels, and secondly due to the increased phase contrast at high temporal resolution.

[0042] In this embodiment, a first housing 3 in the form of a source tube is used, inserted obliquely into the flow channel 1 under investigation, with its rounded tip positioned 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 integrated into the tip, which is bombarded with an electron beam from an obliquely positioned electron gun. The first housing 3 and the second housing 7 can be made of the same material, but it is also possible to use different materials. For example, titanium, aluminum, stainless steel, or a carbon fiber reinforced plastic can be used.

[0043] The accelerating voltage can therefore be adapted 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 plane of the circle is aligned with the apex of the first housing 3. The detectors 5 can be read out in parallel, and thus radiographic attenuation values ​​can be recorded along beam fans distributed over 360° of the cross-section of the flow channel 1 perpendicular to the flow direction.

[0044] The cycle time of this radiography depends on the flux of the radiation source 4 and, when using X-rays, can reach up to several kilohertz, thereby achieving a temporal resolution in the millisecond range. Due to the reduced measurement 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 thus, in turn, increases the contrast within the phases under investigation.

[0045] Furthermore, the requirements for radiation protection are reduced, which significantly increases the acceptance of such a device in industrial environments. In known radiographic measuring devices with a radiation source 4 located outside the flow channel 1, each scanning beam experiences a different path length in the cross-section and therefore a different object attenuation. This leads to varying sensitivity across the cross-section.

[0046] The present invention overcomes this significant disadvantage, since each scanning beam has the same geometry and therefore the same reference attenuation. Furthermore, a higher sensitivity is achieved simply by reducing the scanning length to less than d / 2 (half the diameter of the flow channel 1), which is the same for all measuring channels or detectors 5.

[0047] 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 gain in information compared to conventional fan-beam densitometers. For example, with the arrangement according to the invention, it would be possible to directly determine, by evaluating the two perpendicularly opposing detectors 5, whether an annular flow or a stratified flow is present. The quantification accuracy for the liquid phase fraction is thus significantly increased.

[0048] Fig. 2 shows how Fig. Figure 1 shows an embodiment of the device according to the invention, wherein the cross-section of the device is 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, even with a significant reduction in the radiation length, complete irradiation is still ensured.

[0049] This device enables high-resolution temporal and spatial 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 operates entirely without moving parts and is therefore maintenance-free in the field. The arrangement surpasses the performance of known radiological flow meters in terms of measurement speed and spatial resolution. By positioning the radiation source 4 in the center of the cross-section of the flow channel 1 under investigation, the radiation energy 6 can be significantly reduced compared to classical radiographic methods. The comparatively low photon energy provides better contrast between the phases of the fluid flow 2 and facilitates radiation protection.

[0050] Furthermore, tomographic image reconstruction is unnecessary, allowing for 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 it particularly suitable for industrial applications.

[0051] Furthermore, through Fig.Figure 2 clearly shows that the radiation source 4 is not in direct contact with the fluid flow 2, although it is centrally located within the fluid flow 2. The first housing 3, in this case a measuring tube, facilitates the simple insertion of the radiation source 4. The one-sided rounded shape of the first housing 3 minimizes the turbulence it creates in the fluid flow 2. Thus, the first housing 3 is streamlined to prevent distortion of the measurement data. Furthermore, the media-tight seal of the first housing 3 ensures that the fluid flow 2 is not contaminated by the radiation source 4. 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] WO 2010 034 584 A1

[0007]

Claims

[1] Device for characterizing fluid flows, comprising: a flow channel (1) which is designed for at least one fluid flow (2) to flow through, 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) which is designed to detect emitted radiation (6) of 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 bythat the first housing (3) runs 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 by that the first housing (3) is designed as an inwardly shaped bulge of the flow channel (1). [4] Device for characterizing fluid flows according to one of the preceding claims, characterized by 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. [5] Device for characterizing fluid flows according to one of the preceding claims, characterized bythat several radiation sources (4) are formed in the first housing (3). [6] Device for characterizing fluid flows according to one of the preceding claims, characterized by that at least two first housings (3) are arranged one behind the other parallel to the flow direction of the fluid flow (2). [7] Device for characterizing fluid flows according to one of the preceding claims, characterized by that a plurality of detectors (5) form an almost completely closed detector ring around the flow channel (1). [8] Device for characterizing fluid flow according to one of the preceding claims, characterized by that the radiation source (4) is designed as an isotope source or X-ray source or laser source. [9] Device for characterizing fluid flows according to one of the preceding claims, characterized bythat 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). [10] 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 then the radiation (6) is detected by at least one detector (5) arranged on the surface of the flow channel (1) facing away from the fluid flow (2).

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