FLOW METER

Description

[0001] The invention relates to a flow meter for measuring the flow velocity of a fluid, comprising a measuring tube which forms a measuring chamber through which the fluid can flow, and comprising at least one disruptive body which is arranged in the measuring chamber, and wherein in the measuring chamber downstream of the disruptive body there is further arranged a measuring sensor which can be deflected due to the formation of vortices on the disruptive body when the fluid flows around it, wherein the measuring tube has an elliptical cross-section at least in the region of the arrangement of the disruptive body. STATE OF THE ART

[0002] Flow meters of the type of interest here are also known as eddy current sensors and are widely used for measuring the flow of fluids, especially liquids. They are characterized by high reliability and low manufacturing costs. However, due to the vortex formation in the fluid necessary for the measurement, the disadvantage is a comparatively high pressure drop during the flow of the fluid, which is accompanied by an energy loss in the fluid system into which the flow meter is integrated.

[0003] Several approaches are known for minimizing pressure loss. For example, according to a first approach, pressure loss can be minimized by optimizing the geometry of the bluff body. Thus, a variety of bluff body geometries are now known that deviate from the standard shapes of a cylindrical body or a delta bluff body.

[0004] Another approach to reducing pressure loss is to minimize the cross-section of the measuring tube in the area of ​​the bluff body. Flow meters are known that have a measuring chamber that tapers down to the bluff body and widens again downstream of the bluff body. As a result, the measuring cross-section is also smaller than approximately the nominal diameter of the flow meter's connections. Thus, the attempt is made to limit the necessary measuring cross-section to the smallest possible space in order to minimize the overall pressure loss. In this description, cross-sections of the measuring chamber or measuring tube always refer to cross-sections on whose cross-sectional area the flow axis forms a surface normal, i.e., the surface normal is perpendicular to the cross-sectional area.

[0005] A third approach involves optimizing the dimensions between the bluff body and the flow cross-section. To do this, the pressure loss in the measured value can initially be considered separately from the pressure loss of the bluff body. For a defined volume flow, the pressure loss for the measuring tube increases with a smaller cross-section. For the bluff body, the pressure loss also increases with a larger inflow area. When determining the relationship between the cross-section of the measuring tube and the dimensions of the bluff body, an optimum can also be sought according to the third approach.

[0006] For example, DE 10 2018 101 278 A1 describes a flow meter for measuring the flow velocity of a fluid, comprising a measuring tube that forms a measuring chamber through which the fluid can flow, and at least one bluff body arranged in the measuring chamber. A measuring sensor is also arranged in the measuring chamber downstream of the bluff body, which sensor can be deflected due to vortex formation on the bluff body when the fluid flows around it. To optimize vortex formation, at least one projection extending into the measuring chamber is formed upstream of the bluff body on an inner wall delimiting the measuring chamber. This amplifies the vortexes that form on the bluff body, so that a comparatively high voltage level can be output via the measuring sensor with an overall low pressure loss.

[0007] The geometry of the bluff body primarily affects two fluid mechanics properties that are important in an eddy current sensor. One of these properties is the pressure drop, which is comparatively low, for example, with cylindrical geometries in relation to the inflow area. The other desired property is a Strouhal number that is as constant as possible over a wide range of the Reynolds number. This ensures that the vortex frequency, as the primary measured variable, has a linear relationship to the flow velocity calculated from it. In contrast to the cylindrical bluff body, the delta-shaped bluff body displays particularly good properties. Other forms of bluff bodies, which attempt to combine the advantages of both geometries, are usually much more complicated and therefore, in practice, considerably more complex to manufacture.

[0008] However, simply reducing the pressure loss during flow through the flow meter does not necessarily lead to increased efficiency in data acquisition. A high voltage level with a low overall pressure loss is desirable.

[0009] JP 2004 191 173 A D1 shows a flow meter for measuring the flow velocity of a fluid, comprising a measuring tube forming a measuring chamber through which the fluid can flow, and at least one bluff body arranged in the measuring chamber. A measuring sensor is also arranged in the measuring chamber downstream of the bluff body, which sensor can be deflected by the fluid flowing around it due to vortex formation on the bluff body. The measuring tube, at least in the region where the bluff body is arranged, has an elliptical cross-section with a longer major axis and a shorter minor axis. The minor axis of the ellipse is smaller than the diameter upstream of the elliptical cross-section, but the major axis of the ellipse is also smaller than the circular cross-section of the fluid inlet or outlet of the measuring tube. DISCLOSURE OF THE INVENTION

[0010] The object of the invention is to further improve a flow meter for measuring the flow velocity of a fluid, whereby the aim is to achieve the highest possible ratio of the voltage potential of the measuring sensor to the pressure loss of the flowing fluid in the measuring tube by geometrically optimizing the flow cross-section in the measuring tube.

[0011] This object is achieved by a flow meter according to the preamble of claim 1 in conjunction with the characterizing features. Advantageous developments of the invention are specified in the dependent claims.

[0012] The invention includes the technical teaching that the circular cross-section of the fluid inlet and / or the fluid outlet has a diameter that corresponds to the length of the main axis of the elliptical cross-section, so that the width of the measuring space remains constant transversely to the bluff body axis from the fluid inlet to the fluid outlet.

[0013] By choosing an advantageous elliptical shape of the cross section of the measuring tube, at least in the area where the bluff body is arranged, the ratio of usable measuring signal to pressure loss can be specifically improved, thus maximizing the efficiency of the flow meter.

[0014] The elliptical shape of the measuring chamber along the flow axis thus, according to the invention, ensures that the cross-section of the fluid inlet and / or the fluid outlet has a diameter that corresponds to the length of the main axis of the elliptical cross-section. As a result, the width of the measuring chamber remains constant transversely to the flow axis from the fluid inlet to the fluid outlet. By forming the elliptical cross-section according to the invention in the region where the bluff body is arranged within the measuring tube, the cross-section of the measuring tube narrows only in the direction of the bluff body axis, while the cross-section in the direction of the main axis remains unchanged and corresponds to the diameter of the circular cross-section of the fluid inlet and / or the fluid outlet.

[0015] The elliptical shape of the cross-section of the measuring tube can be present exactly in the plane of the arrangement of the disruptive body and in an adjacent area in front of and behind the disruptive body, for example in a range between 10% and 20%, between 20% and 30%, between 30% and 40%, between 40% and 50%, between 50% and 60%, between 60% and 70% and / or between 70% and 80% based on the total length of the measuring tube or based on the length between the disruptive body and the fluid inlet or the fluid outlet of the measuring tube.

[0016] Due to the horizontal ellipse shape relative to the vertical axis of the bluff body, a continuously wide area is provided along a major axis of the ellipse in the width direction, in which the vortices can form spatially well to the sides of the bluff body. While the ellipse narrows toward the bluff body along the minor axis, and widens again in the vertical direction after the bluff body in the flow direction. This increases the flow velocity toward the bluff body, and the flow velocity reaches a maximum in the area of ​​the bluff body.

[0017] The vortices form primarily in the area of ​​the ellipse's main axis, whereby the effect of pressure fluctuations on the sensor and thus on its deflection has a beneficial influence on a high voltage level of the sensor's output voltage. At the same time, the flow is accelerated, thus also increasing the intensity of the fluidic influence on the sensor. The positive effect results from a better relationship between the sensor's measurement signal and the pressure loss.

[0018] The measuring chamber of the measuring tube extends between a fluid inlet and a fluid outlet along a flow axis, with the fluid inlet having a circular cross-section which, along the flow axis up to the position of the disruptive body, transitions into an elliptical cross-section. In this respect, the elliptical cross-section transitions into a circular cross-section from the position of the disruptive body along the disruptive axis up to the fluid outlet. Over its entire length, the measuring chamber of the measuring tube is shaped such that the measuring chamber begins with a circular cross-section and ends with a circular cross-section. In particular, the elliptical shape is at its maximum in the area of ​​the disruptive body, which means that there is a maximum ratio between the major axis and the minor axis of the ellipse in the position of the disruptive body. This ratio decreases with increasing distance from the disruptive body to the fluid inlet and from the disruptive body to the fluid outlet.

[0019] The bluff body extends in a conventional manner along a bluff body axis, wherein the bluff body axis forms the axis along which the bluff body preferably does not change its cross-section. The bluff body axis runs perpendicular to the flow axis extending through the measuring chamber. In conjunction with the features according to the invention, the bluff body can have a round, elliptical, streamlined, trapezoidal, or triangular cross-section.

[0020] The elliptical cross-section is spanned by a longer major axis and a shorter minor axis running perpendicular to the major axis. The alignment of the major axis and minor axis is designed so that the minor axis coincides with the bluff body axis. This results in the advantage that the perpendicular major axis creates a wider space to the side of the bluff body in which the vortices can form, allowing the vortices to migrate more effectively downstream to impact the sensor.

[0021] In particular, it is provided that the length ratio of the major axis to the minor axis has a value of 1.1 to 2.0, preferably 1.25 to 1.8, and particularly preferably 1.3 to 1.6. In particular, the numerical ratio of the length of the major axis to the contact surface of the disruptive body has a value of 0.15 to 0.6, preferably 0.2 to 0.5, and particularly preferably 0.25 to 0.45.

[0022] The sensor is arranged in a section along the flow axis in the measuring chamber, with the cross-section of the measuring chamber having an elliptical cross-section, which, however, transitions back to a circular cross-section towards the fluid outlet. The ratio between the major axis and minor axis of the elliptical cross-section is therefore slightly smaller in the area of ​​the sensor arrangement than in the area of ​​the bluff body.

[0023] With even more advantage, at least one projection protruding into the measuring chamber is formed upstream of the disruptive body on an inner wall bounding the measuring chamber. This achieves the effect of vortex amplification, so that a high level of the output voltage of the measuring sensor can be achieved even at low flow velocities of the fluid in the measuring tube. The reason for this effect can be assumed that the arrangement of at least one and preferably two opposing projections upstream of the disruptive body generates pre-turbulence at the projection. The turbulence generated at the projection detaches from the projection and can amplify the vortices generated at the disruptive body in a developing Karmann vortex street. The result is a stronger impact on the measuring sensor due to the intensified vortices that periodically detach themselves from the disruptive body.It is particularly advantageous if there are two diametrically opposed projections on the inner wall of the measuring tube in the area of ​​the fluid inlet, with a diametrical line defined by the projections lying parallel to the main axis of the elliptical cross-section.

[0024] In this case, downstream and upstream are understood to mean the direction with the flow axis towards the fluid outlet and upstream is understood to mean the direction opposite the flow axis towards the fluid inlet. PREFERRED EMBODIMENT OF THE INVENTION

[0025] Further measures improving the invention are described in more detail below, together with the description of a preferred embodiment of the invention, with reference to the figures. It shows: Figure 1 is a cross-sectional view of the flow meter with a measuring chamber having the geometric shape according to the invention, Figure 2 is a cross-sectional view of the flow meter with a cross-sectional plane rotated 90° to the cross-sectional plane of the cross section according to Figure 1, Figure 3a shows a first advantageous cross-sectional geometry of the disruptive body, Figure 3b shows a second advantageous cross-sectional geometry of the disruptive body, Figure 4 shows a view of the flow meter with a view into the measuring chamber from the flow axis, Figure 5 shows a schematic representation of the disruptive body with different cross-sectional geometries of the measuring chamber, Figure 6 shows a schematic view of vortex formation on the disruptive body and Figure 7 shows a modified embodiment of the measuring tube of the flow meter with a cladding tube and with a tube insert, Figure 8 shows a diagram of the difference in percent of the measuring voltages with an elliptical flow cross-section to a circular flow cross-section, in each case normalized to the resulting pressure difference, and Figure 9 shows a diagram of the measuring voltages versus the pressure difference when flowing through the measuring chamber from inlet to outlet with an elliptical flow cross-section to a circular flow cross-section.

[0026] In Figure 1a cross-sectional view of the flow meter 1 is shown, and the flow meter 1 is shown cut from left to right along the flow axis 16 according to the arrow shown and through which flow can pass. The flow meter 1 is used to determine a flow rate per unit of time that flows through the measuring tube 10 of the flow meter 1. The flow-through area of ​​the measuring tube 10 is referred to as the measuring chamber 11, and in the measuring chamber 11 and thus in the flow region of the fluid there is a bluff body 12 and a downstream measuring sensor 13. The bluff body 12 is located upstream of the measuring sensor 13 with respect to the flow axis 16, and the flow against the bluff body 12 creates periodically shedding vortices on it, which lead to a deflection of the measuring sensor 13 in a deflection direction transverse to the flow axis 16.The deflection of the sensor 13 also occurs periodically, allowing a measurement signal to be derived by arranging a measuring element 21 in connection with the sensor 13, which can be configured with the measuring electronics 22. The measuring element 21 is preferably designed as a piezo element.

[0027] The bluff body 12 extends along a bluff body axis 12a, which runs transversely to the flow axis 16. Parallel to, but downstream of, the bluff body axis 12a extends the measuring sensor 13, which protrudes like a sword into the measuring chamber 11 and is arranged below the measuring electronics 22, which is accommodated on the outside of the measuring tube 10 in a measuring electronics receptacle 27.

[0028] The measuring tube 10 extends from a fluid inlet 14 to a fluid outlet 15, wherein a connection piece 28 is shown in the fluid inlet 14.

[0029] According to the invention, the cross-section of the measuring tube 10 in the region of the arrangement of the disruptive body 12 has an elliptical cross-section Q1. In contrast, the measuring tube 10 has a cross-section in the region of the fluid inlet 14 and in the region of the fluid outlet 15 that is designed according to a circular cross-section Q0. The cross-section of the measuring chamber 11 along the flow axis 16 consequently changes, starting with a circular cross-section Q0 in the fluid inlet 14 and ending with an elliptical cross-section Q1 in the region of the arrangement of the disruptive body 12, and further downstream along the flow axis 16, transitions back into a circular cross-section Q0 at the fluid outlet 15. The circular cross-section Q0 only returns after the arrangement of the measuring sensor 13, whereby, only by way of example, a longer region downstream along the flow axis 16 has the circular cross-section Q0 than before the arrangement of the disruptive body 12, which can also be provided the other way round.For visualization, the cross-sections Q0 and Q1 are rotated 90° around a vertical axis in the section plane.

[0030] The elliptical shape of the elliptical cross-section Q1 is designed to be horizontal with respect to the direction of extension of the disruptive body axis 12a, wherein the longer main axis of the elliptical cross-section Q1 corresponds to the diameter of the circular cross-section Q0.

[0031] To optimize vortex formation, two projections 20 extending into the measuring chamber 11 are formed upstream of the bluff body 12 on an inner wall 19 defining the measuring chamber 11. This allows the vortices forming on the bluff body 12 to be amplified, so that a comparatively high voltage level can be output via the sensor with an overall low pressure loss.

[0032] Consequently, the width of the measuring tube 10 does not change on the half plane between the fluid inlet 14 and the fluid outlet 15, as the 90° rotated cross-sectional shape in Figure 2 This means that the major axis 17 of the elliptical cross-section corresponds to the diameter of the circular cross-section Q0, so that the representation in Fig. 2 shows a measuring chamber 11 in the measuring tube 10, which does not change in width from the fluid inlet 14 to the fluid outlet 15. The illustration also shows, in particular, that two diametrically opposed projections 20 are arranged on the inner wall 19 of the measuring chamber 11, which are positioned opposite each other such that they are positioned on the outer sides along the main axis 17 of the elliptical cross-section Q1, wherein the projections 20 are provided in front of the elliptical cross-section Q1 in the region of the circular cross-section Q0 at the level of the fluid inlet 14.

[0033] Figure 3ashows a possible cross-sectional shape of a bluff body 12, which essentially corresponds to a triangular shape, wherein the base section of the triangle of the cross-sectional shape has a rectangular extension that points opposite to the flow and is therefore directly subjected to flow when the flow meter 1 is in use. Measured transversely from this rectangular extension, the bluff body 12 has a width B, which, with reference to the installation position of the bluff body 12 in the measuring chamber 11, extends in the same direction as the main axis 17 of the elliptical cross-section Q1.

[0034] Figure 3b shows another possible form of a disruptive body 12 with a trapezoidal cross-section, which also has a rectangular base section.

[0035] The disruptive bodies 12 in the Figures 3a and 3b are flowed according to the arrow shown, so that the wide, flat front of the triangular shape and the trapezoidal shape points opposite to the flow.

[0036] In particular, the Figures 3a and 3b The cross-sectional shapes of the disruptive body 12 shown can be used particularly advantageously in conjunction with the measuring chamber 11 formed according to the invention in the measuring tube 10.

[0037] Figure 4shows a view of the flow meter 1 from the direction of the flow axis 16, so that one can look into the measuring chamber 11 of the measuring tube 10. The view shows the circular cross-section Q0 on the front, into which the two diametrically opposed projections 20 on the inner wall 19 of the measuring chamber 11 also protrude, whereby the circular cross-section Q0 merges into the elliptical cross-section Q1 in the area of ​​the disruptive body 12. The measuring sensor 13 is shown on the top side, which is connected to the measuring electronics 22, which is accommodated in the measuring electronics holder 27 on the outside of the measuring tube 10. The illustration once again clarifies the horizontal arrangement of the ellipse of the elliptical cross-section Q1, as in connection with the following Figure 5 explained in more detail.

[0038] Figure 5shows a schematic view of the changing cross-section, starting with the circular cross-section Q0 and transitioning into the elliptical cross-section Q1 in the region of the disruptive body 12. The ellipse of the elliptical cross-section Q1 has a major axis 17 that is horizontal, so that the major axis 17 and the disruptive body axis 12a are perpendicular to each other. In contrast, the minor axis 18 of the ellipse of the elliptical cross-section Q1 runs vertically together with the disruptive body axis 12a, as shown.

[0039] The ellipse is formed by the longer major axis 17 and the shorter minor axis 18, whereby the length of the major axis 17 corresponds to the diameter of the circular cross-section Q0.

[0040] If the measuring tube 10 were to retain a circular cross-section that decreases up to the position of the bluff body 12, the reference circular cross-section Q0' would result. It is clear that the area to the side of the bluff body 12, where the vortices are intended to form, is shortened, since the diameter of the tapered circular cross-section is smaller than the major axis 17, which remains unchanged and corresponds to the diameter of the circular cross-section Q0. In contrast, the shortened minor axis 18 ensures a shortening 26 of the bluff body 12 along the bluff body axis 12a. This shortening 26 has no significant influence on the achievable voltage level that can be output by the measuring sensor 13, but does reduce the pressure loss.

[0041] Figure 6shows schematically a section of the measuring tube 10 with the inner measuring chamber 11 in the area of ​​the arrangement of the disruptive body 12. The flow axis 16 is shown as a flow arrow and the measuring sensor 13 is located downstream of the disruptive body 12.

[0042] Vortices 25 form on the bluff body 12, which periodically detach and cause pressure fluctuations laterally from the transducer 13, which deflect the transducer 13, which can ultimately be detected by the measuring element 21. The main axis 17, due to its greater length, creates a very large width even in the area of ​​the bluff body 12, although the secondary axis 18 of the elliptical cross-section Q1, which is perpendicular to the image plane, is shortened. Due to the decreasing flow cross-section, the flow is accelerated, which intensifies the vortex formation and allows a higher measuring voltage to be generated at the measuring element 21 even at low flow velocities. However, due to the expanded area of ​​the measuring chamber 11 in the area of ​​the bluff body 12 in the lateral direction, which corresponds to the main axis 17 of the elliptical cross-section Q1, the diameter remains the same compared to the circular cross-section Q0' according to Figure 5a spatially wide area must exist so that the vertebrae 25 can develop advantageously.

[0043] Figure 7 shows a modified form of the measuring tube 10 with a cladding tube 10a and with an inner tube 10b as the base body of the flow meter, wherein the inner tube 10b is inserted into the cladding tube 10a, so that the measuring tube 10 is designed in two parts according to this variant.

[0044] The advantage of the two-part design is particularly the simplified manufacture of the measuring tube 10 for high pressures of the measuring fluid, since the elliptical cross sections Q1 of the inner wall of the measuring chamber 11 as well as the disruptive body 12 in the measuring chamber 11 can be manufactured in one piece with the actual inner tube 10b, advantageously by plastic injection molding, the inner tube 10b with the more complex geometries can therefore be manufactured from plastic by injection molding, whereby the complexity of the geometry for the plastic injection molding process for the inner tube 10b is secondary compared to machining.

[0045] Another advantage is the manufacture of the cladding tube 10a from a metallic material, allowing the flow meter to be designed for higher to very high pressures of the measuring fluid. It is also advantageous that, for example, the inner passage 29 in the cladding tube 10a can easily have a continuous cylindrical cross-section and can be machined, for example, by drilling or by boring. The base body of the cladding tube 10a can, for example, be provided as a metal die-cast component or manufactured as a turned part from a correspondingly dimensioned cylinder body or a cylinder sleeve as a blank.

[0046] The outer diameter of the inner tube 10b corresponds to the inner diameter of the cladding tube 10a, so that preferably a transition fit is formed or a slight pressing is caused.

[0047] The advantage of qualifying the flow meter for very high pressures and simplifying manufacturability is achieved in particular by producing the inner tube 10b with essentially the same length as the length of the cladding tube 10a and / or wherein the cladding tube 10a and the inner tube 10b have a closed, full-circumference cross-section, which is pressure-tight in itself, apart from small openings or the passage for the measuring sensor.

[0048] Figure 8This diagram shows the difference in percent of the measured voltages between an elliptical flow cross-section and a circular flow cross-section plotted against the volume flow in liters per minute, normalized to the resulting pressure difference. The diagram clearly shows that the elliptical design of the measuring chamber, especially at low flow velocities, enables a significant increase in the measured signal compared to the measured signal with a circular cross-section, in each case relative to the pressure difference.

[0049] Figure 9 Finally, a diagram of the measured voltage U versus the pressure difference Δp, measured from the inlet to the outlet of the measuring tube, is shown. The voltage U1 versus the pressure loss with the elliptical cross-section according to the invention is, as the graph shows, higher than the voltage U2 versus the pressure loss without the elliptical cross-section design.

[0050] Within the scope of the present invention, the specified elliptical cross-section of the measuring chamber also includes cross-sections that are elliptical in shape, meaning they do not necessarily have to correspond to a mathematical ellipse. Thus, a rectangular cross-section with radiated or rounded corners, or with flat wall sections in the area where the main and secondary axes intersect the interior wall of the measuring chamber, can also fall under the claimed elliptical cross-section within the meaning of the invention. List of reference symbols:

[0051] 1Flow meter 10Measuring tube 10aCover tube 10bInner tube 11Measuring chamber 12Bullet 12aBullet axis 13Measuring sensor 14Fluid inlet 15Fluid outlet 16Flow axis 17Major axis 18Minor axis 19Inner wall 20Protrusion 21Measuring element 22Measuring electronics 23Cone 24Shadow area 25Vortex 26Reduction 27Measuring electronics receptacle 28Connecting piece 29Inner passage UMeasuring voltage U1Voltage across pressure loss with ellipse U2Voltage across pressure loss without ellipse ΔpPressure difference inlet to outlet Q1Elliptical cross-section Q0Circular cross-section Q0'Reference circular cross-section BWidth of the bluff body

Claims

1. A flowmeter (1) for measuring the flow rate of a fluid having a measuring tube (10) that forms a measuring space (11) through which the fluid can flow and having at least one baffle (12) that is arranged in the measuring space (11) and wherein a measured value sensor (13) that is deflectable when flowed around by the fluid due to a vortex formation at the baffle (12) is furthermore arranged downstream of the baffle (12) in the measuring space (11), wherein the measuring tube (12) has an elliptical cross-section (Q1) at least in the region f the arrangement of the baffle (12), characterized in that a circular cross-section (Q1) of a fluid inlet (14) and / or of a fluid outlet (15) has a diameter measurement that corresponds to the length of a main axis (17) of the elliptical cross-section (Q1) so that the width of the measuring space (11) transversely to the baffle axis (12a) remains constant from the fluid inlet (14) up to the fluid outlet (15).

2. A flowmeter (1) in accordance with claim 1, characterized in that the measuring space (11) of the measuring tube (10) extends between the fluid inlet (14) and the fluid outlet (15) along a flow axis (16), with the fluid inlet (14) having the circular cross-section (Q0) that merges into the elliptical cross-section (Q1) along the flow axis (16) extending up to the position of the baffle (12).

3. A flowmeter (1) in accordance with claim 1 or claim 2, characterized in that the elliptical cross-section (Q1) merges into the circular cross-section (Q0) from the position of the baffle (12) along the flow axis (16) up to the fluid outlet (15).

4. A flowmeter (1) in accordance with one of the claims 1 to 3, characterized in that the baffle (12) has the baffle axis (12a) along which the baffle (12) extends, with the baffle axis (12a) being aligned perpendicular to the flow axis (16) extending through the measuring space (11) and / or with the baffle (12) having a round, elliptical, streamlined, trapezoidal, or triangular cross-section.

5. A flowmeter (1) in accordance with claim 4, characterized in that the elliptical cross-section (Q1) is spanned by the longer main axis (17) and a shorter secondary axis (18) extending transversely to the main axis (17), with the elliptical cross-section (Q1) being aligned such that the secondary axis (18) coincides with the baffle axis (12a).

6. A flowmeter (1) in accordance with one of the preceding claims, characterized in that the length ratio from the main axis (17) to the secondary axis (18) has a value from 1.1 to 2.0, preferably from 1.25 to 1.8, and particularly preferably from 1.3 to 1.6.

7. A flowmeter (1) in accordance with one of the preceding claims, characterized in that the ratio of the length of the main axis (17) to the surface of attack of the baffle (12) has a value from 0.15 to 0.6, preferably from 0.2 to 0.5, and particularly preferably from 0.25 to 0.45.

8. A flowmeter (1) in accordance with one of the preceding claims, characterized in that the measured value sensor (13) is arranged in a section along the flow axis (16) in the measuring space (11) in which the cross-section of the measuring space (11) has an elliptical cross-section (Q1) and merges into the circular cross-section in the direction toward the fluid outlet (14).

9. A flowmeter (1) in accordance with one of the preceding claims, characterized in that at least one projection (20) projecting into the measuring space (11) is formed downstream of the baffle (12) at an inner wall (19) bounding the measuring space (11).

10. A flowmeter (1) in accordance with one of the preceding claims, characterized in that the measuring tube (10) is formed with a sheath (10a) and with an inner tube (10b), with the inner tube (10b) being pushed into the sheath (10a).

11. A flowmeter (1) in accordance with claim 10, characterized in that the inner tube (10b) and the sheath (10a) have the same length in the flow axis (16); and / or in that the inner tube (10b) has 70% to 100% of the length of the sheath (10a).

12. A flowmeter (1) in accordance with claim 10 or claim 11, characterized in that the inner tube (10b) and / or the sheath (10a) has / have a fully circumferentially closed cross-section.

13. A flowmeter (1) in accordance with claims 10 to 12, characterized in that the inner tube (10b) comprises a plastic; and / or in that the sheath (10a) comprises a metal.

14. A flowmeter (1) in accordance with claims 10 to 13, characterized in that the inner tube (10b) is manufactured in an injection molding process; and / or in that the sheath (10a) is manufactured in a cutting production process.