Device for flow measurement

Abstract

Device for measuring the flow of a medium (11) in a pipe section (2'), with an ultrasonic sensor (5) arranged in the pipe section (2'), wherein the ultrasonic sensor (5) comprises two spaced-apart ultrasonic elements (5', 5"), such that a measuring region (6) for the medium (11) is formed between the two ultrasonic elements (5', 5"), and with an inlet (3) for the medium (11) to the pipe section (2') and with an outlet (4) for the medium (11) from the pipe section (2'), characterized in that the medium (11) flows substantially uniformly into the pipe section (2') in the region of the inlet (3) at a flow-around region (7) circumferentially adjacent to the pipe section (2'), that the medium (11) flows substantially uniformly in the region of the outlet (4) at a flow-around region (8) circumferentially adjacent to the pipe section (2'). flows out of the pipe section (2'),and that the medium (11) flows essentially uniformly through the measuring area (6).,

Description

[0001] The invention relates to a device for flow measurement according to the preamble of patent claim 1.

[0002] Such a flow measuring device is used to measure the velocity of a fluid medium flowing through a pipeline.

[0003] Such a device has an ultrasonic sensor arranged in a section of the pipeline. The ultrasonic sensor comprises two spaced-apart ultrasonic elements, such that a measuring area for the medium is formed between the two ultrasonic elements. Furthermore, the device has an inlet for the medium to the pipeline section and an outlet for the medium from the pipeline section. It has been found that the following problems occur with this device: - There are vortex flows in front of the ultrasonic elements, which are very large, especially at high volume flows in the pipeline. - The signal noise of the measurement signal generated by the ultrasonic elements is very high due to turbulent flows. - Furthermore, the signal noise is very high due to secondary flows in the pipeline. - The risk of functional failure of the device due to the inclusion of air bubbles is very high. - The signal difference of the measuring signal generated by the ultrasonic elements between a small and a high volume flow is very small.

[0004] The invention is based on the object of further developing the flow measurement device in such a way that eddy currents in front of the ultrasonic elements are reduced. In particular, the above-mentioned disadvantages are to be largely avoided.

[0005] This object is achieved in a generic device for flow measurement by the characterizing features of claim 1.

[0006] In the flow measurement device according to the invention, the medium flows essentially uniformly into the pipeline, in particular into the pipeline section, in the inlet region at a flow area surrounding the pipeline. Furthermore, the medium flows essentially uniformly out of the pipeline, in particular out of the pipeline section, in the outlet region at a flow area surrounding the pipeline. The respective flow area at the inlet and at the outlet thus essentially completely surrounds the corresponding circumference of the pipeline section. Furthermore, the medium flows essentially uniformly through the measuring area. This advantageously largely prevents eddy currents of the medium at the ultrasonic elements, so that a significant improvement in the signal quality of the ultrasonic sensor is achieved.Further embodiments of the invention are the subject of the subclaims.

[0007] In a further compact embodiment, one ultrasonic element can be arranged in the inlet area of the pipe section. The other ultrasonic element can be arranged in the outlet area of the pipe section. With such an arrangement, the respective ultrasonic element advantageously limits or closes off the measuring range and / or the pipe section.

[0008] In a simple embodiment, the pipe section can be substantially cylindrical with a circular cross-section. It may then be appropriate to arrange a plurality of openings, which are in particular substantially evenly spaced from one another and / or substantially evenly distributed around the circumference of the pipe section, in the flow region within the pipe section. This arrangement ensures, or can at least be selected such that, the medium flows substantially evenly along the respective ultrasonic element. The opening can expediently be elongated oval, in particular in the manner of an elongated hole.

[0009] The flow area at the inlet and / or outlet can be provided with a sealing element to seal off the medium, thus increasing the operational reliability of the flow measurement device. The sealing element can be an O-ring for a cost-effective solution. Furthermore, the ultrasonic element can be a piezo element for a more reliable solution.

[0010] In a further embodiment, which is characterized by both simplicity and high operational and / or functional reliability, the flow element forming the flow area can be essentially cylindrical and annular with a circular cross-section. The diameter of the circular cross-section of the flow element is expediently larger than that of the pipe section. Furthermore, the flow element can be arranged essentially concentrically to the pipe section. Finally, the inlet and / or outlet can be formed on the outer surface of the cylindrical flow element. Furthermore, for the sake of ease of assembly, the flow element can be placed on the pipe section. For example, the flow element can be pushed or screwed onto the pipe section.The flow-around element can rest on at least one bearing and / or the flow-around element can rest on a stop.

[0011] The following can be stated for a particularly preferred embodiment of the invention.

[0012] The aim is to develop a geometry for ultrasonic flow measurement that essentially avoids the following previous disadvantages: - The vortex flows in front of the ultrasonic elements, which occur particularly at high volume flows, are very large. - The signal noise due to turbulent flows is very large. - The signal noise due to secondary currents is very large. - The functional risk due to the inclusion of air bubbles is very high. - The signal difference between low and high volume flow is very small.

[0013] The geometry according to the invention forms a closed pipe through which the medium flows. To ensure a uniform flow pattern, the medium is fed to the sensor area via an inlet. The sensor area is evenly flowed through several openings by a circumferential flow area, with the medium to be measured. The medium then flows through a straight sensor section matched to the ultrasonic elements before being returned to the outlet in a manner analogous to the described inflow behavior.

[0014] This concept allows for a positive influence on the secondary flows and resulting vortex flows caused by centrifugal forces, reliably reducing the signal noise present in the metrological evaluation of the ultrasonic signal. Furthermore, the inclusion of air bubbles in the sensor area relevant to the measurement signal is avoided.

[0015] The geometry according to the invention allows the useful signal to be noticeably improved and consequently the flow velocity to be better determined.

[0016] The actual ultrasonic measurement can be performed using state-of-the-art measurement methods. Methods based on the entrainment effect, such as phase difference measurement, frequency difference measurement, the pulse method, or the deflection method, are suitable for this purpose.

[0017] This creates a flow sensor geometry for low-noise ultrasonic measurement within closed pipelines.

[0018] The advantages achieved by the invention are in particular the following: - Reliable and / or accurate flow measurement is achieved, especially at high flow rates. - Vortex flows in front of the ultrasonic elements are avoided. - Reduced signal noise is achieved. - There is a reduction of secondary flows in the relevant section. - The inclusion of air bubbles is effectively prevented. - The signal distance can be adjusted by a simple change in geometry. - There is only a slight pressure drop at the flow measuring device. - It is a durable and / or efficient solution that does not require additional components in the customer application. - It is a wear-free flow measurement, so replacing wearing parts is not necessary. - The signal evaluation can be carried out internally in the flow measurement device and / or externally to it. - It is a fast flow measurement.

[0019] An embodiment of the invention with various developments and refinements is shown in the drawings and is described in more detail below. Fig. 1 a device for flow measurement with an inlet and an outlet in perspective view, Fig. 2 the device from Fig. 1, with the inlet and outlet removed, and Fig. 3 a section through the device Fig. 1.

[0020] In Fig. 1 is a device 1 for measuring the flow of a medium 11 (see Fig. 3) in a pipeline 2, hereinafter referred to as flow measuring device 1. The flowable medium 11 is a liquid or a gas, i.e. a fluid that flows in the pipeline 2. The flow measuring device 1 comprises a closed pipeline section 2' and an inlet 3 for the medium 11 to the pipeline section 2' as well as an outlet 4 for the medium 11 from the pipeline section 2'. An ultrasonic sensor 5 is arranged in the pipeline section 2', as shown in Fig. 3. The ultrasonic sensor 5 comprises two spaced-apart ultrasonic elements 5', 5", such that a measuring area 6 for the medium 11 is formed between the two ultrasonic elements 5', 5". The medium 11 flows essentially uniformly into the pipe section 2' in the area of the inlet 3 at a flow-around area 7 circumferentially adjacent to the pipe section 2'. Furthermore, the medium 11 flows essentially uniformly out of the pipe section 2' in the area of the outlet 4 at a flow-around area 8 circumferentially adjacent to the pipe section 2'. Finally, the medium 11 flows essentially uniformly through the measuring area 6. In Fig. 3, the flow direction of the medium 11 is marked with arrows.

[0021] How to proceed based on Fig. 3, one ultrasonic element 5' is arranged in the area of the inlet 3 in the pipe section 2'. The other ultrasonic element 5" is arranged in the area of the outlet 4 in the pipe section 2'. The ultrasonic elements 5', 5" are arranged in the pipe section 2' in such a way that the respective ultrasonic element 5', 5" closes off or limits the measuring area 6 and / or the pipe section 2'.

[0022] As in Fig. 2, the pipe section 2' is essentially cylindrical with a circular or annular cross-section, wherein the cross-section has a diameter d1 (see Fig. 3). Several openings 9 are arranged in the flow area 7, 8 in the pipe section 2'. The openings 9 are substantially evenly spaced from one another and / or substantially evenly distributed around the circumference of the pipe section 2'. As a result, the medium 11 flows substantially evenly along the respective ultrasonic element 5', 5". The opening 9 is elongated oval, specifically in the manner of a slot. The flow area 7, 8 is provided at the inlet 3 and / or at the outlet 4 with a sealing element 10 for sealing the medium 11, as can be seen from the Fig. 3. The sealing element 10 is expediently according to Fig. 2 around an O-ring.

[0023] As in Fig. 1, the flow element 7', 8' forming the flow region 7, 8 is designed as a substantially cylindrical, annular element with a circular cross-section. The flow element 7', 8' has a diameter d2, wherein the diameter d2 of the circular cross-section of the flow element 7', 8' is larger than the diameter d1 of the pipe section 2', as can be seen from Fig. 3. The flow-around element 7', 8' is arranged essentially concentrically to the pipe section 2'. The flow-around element 7', 8' surrounds the circumference of the pipe section 2' essentially completely, wherein according to Fig. 3 between the pipe section 2' and the flow element 7', 8' a channel-like intermediate space 14 is formed as a flow area 7, 8 for the medium 11. The inlet 3 and / or the outlet 4 are according to Fig. 1 formed on the lateral surface of the cylindrical flow element 7', 8'.

[0024] How to continue in Fig. As can be seen in Figure 3, the flow-circulating element 7', 8' is placed on the pipe section 2'. For example, the flow-circulating element 7', 8' can be pushed or screwed onto the pipe section 2'. The flow-circulating element 7', 8' then rests on at least one rib-shaped or helical bearing 12 of the pipe section 2'. Furthermore, the flow-circulating element 7', 8' rests on a flange-like stop 13 of the pipe section 2'.

[0025] The ultrasonic element 5', 5" may be a piezoelectric element. The flow velocity of the medium 11 can then be determined by a method measuring the entrainment effect for the medium 11 in the measuring area 6. For example, the flow velocity can be determined by measuring the transit time difference of the ultrasonic waves between the two piezoelectric elements 5', 5", by measuring a phase difference, by measuring a frequency difference, by using a pulse method, by using a deflection method, or the like. The signal path between the ultrasonic elements 5', 5" can be easily adapted by modifying the pipe section 2'.

[0026] The invention is not limited to the described and illustrated embodiment. Rather, it also encompasses all expert developments within the scope of the invention defined by the patent claims. Thus, such a flow measuring device 1 can be used not only in household appliances, such as washing machines, dishwashers, wet and / or dry vacuum cleaners, or the like, but also in a variety of ways in heating, ventilation, and / or air conditioning (HVAC) technology or in other applications, for example, in laboratory and chemical process engineering. Reference symbol list: 1 flow measuring device / flow measuring device 2 pipeline 2' pipe section 3 Inlet 4 Procedure 5 Ultrasonic sensor 5'.5" ultrasonic element / piezo element 6 Measuring range 7.8 Flow area 7',8' flow element 9 Opening 10 Sealing element 11 Medium 12 camps 13 stop 14 space

Claims

[1] Device for measuring the flow of a medium (11) in a pipe section (2') with an ultrasonic sensor (5) arranged in the pipe section (2'), wherein the ultrasonic sensor (5) comprises two spaced-apart ultrasonic elements (5', 5") such that a measuring area (6) for the medium (11) is formed between the two ultrasonic elements (5', 5"), and with an inlet (3) for the medium (11) to the pipe section (2') and with an outlet (4) for the medium (11) from the pipe section (2'), characterized bythat the medium (11) flows essentially uniformly into the pipe section (2') in the area of the inlet (3) at a flow-around area (7) circumferentially adjacent to the pipe section (2'), that the medium (11) flows essentially uniformly out of the pipe section (2') in the area of the outlet (4) at a flow-around area (8) circumferentially adjacent to the pipe section (2'), and that the medium (11) flows essentially uniformly through the measuring area (6). [2] Flow measuring device according to claim 1, characterized by that one ultrasonic element (5') is arranged in the region of the inlet (3) in the pipe section (2'), and that the other ultrasonic element (5") is arranged in the region of the outlet (4) in the pipe section (2'), in particular such that the respective ultrasonic element (5', 5") closes off the measuring area (6) and / or the pipe section (2'). [3] Flow measuring device according to claim 1 or 2, characterized by that the pipe section (2') is substantially cylindrical with a circular cross-section. [4] Flow measuring device according to claim 1, 2 or 3, characterized by that a plurality of openings (9), in particular substantially uniformly spaced from one another and / or substantially uniformly distributed around the circumference of the pipe section (2'), are arranged in the flow region (7, 8) in the pipe section (2'), in particular such that the medium (11) flows substantially uniformly along the respective ultrasonic element (5', 5"), and that preferably the opening (9) is designed to be elongated oval, in particular in the manner of an elongated hole. [5] Flow measuring device according to one of claims 1 to 4, characterized bythat the flow area (7, 8) at the inlet (3) and / or at the outlet (4) is provided with a sealing element (10), in particular with an O-ring, for sealing the medium (11). [6] Flow measuring device according to one of claims 1 to 5, characterized by that the flow-around element (7', 8') forming the flow-around region (7, 8) is essentially cylindrically annular with a circular cross-section, wherein the diameter of the circular cross-section of the flow-around element (7', 8') is larger than that of the pipe section (2'), that preferably the flow-around element (7', 8') is arranged essentially concentrically to the pipe section (2'), and that further preferably the inlet (3) and / or the outlet (4) are formed on the outer surface of the cylindrical flow-around element (7', 8'). [7] Flow measuring device according to one of claims 1 to 6, characterized bythat the flow-around element (7', 8') is placed on the pipe section (2'), that preferably the flow-around element (7', 8') rests on at least one bearing (12), and that further preferably the flow-around element (7', 8') rests on a stop (13). [8] Flow measuring device according to one of claims 1 to 7, characterized by that the ultrasonic element (5', 5") is a piezo element.

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