Measurement of hydrogen flow rate in pipes

Abstract

To provide a measuring device for measuring the flow rate of hydrogen, which can be easily calibrated regardless of the installation conditions of the measuring device, and therefore can provide a reproducible measurement value with certainty. The present invention relates to a pipe member (12) that is partitioned into a first upstream longitudinal end portion (31) and a second downstream longitudinal end portion (32) each having a first inner diameter D1 (nominal connection diameter) and provided for connection to a pipe, a central longitudinal portion (37) having a second inner diameter D2 larger than D1, and longitudinal transition portions (34, 35) that have in each case varying inner diameters and are provided between the longitudinal end portions (31, 32) and the central longitudinal portion (37), and a radially extending portion (36) that runs from the first longitudinal end portion (31) to the central longitudinal portion (37) and a flow regulator element (50) provided at an upstream end of the central longitudinal portion (37); a circular baffle element (70) disposed at a downstream end of the central longitudinal portion (37) and concentric with the tubular member (12) and defining an annular gap (76) through which flow can pass; and a sensor element (22) having a measurement point (21) for measuring the flow rate located on the central longitudinal axis (L) of the tubular member (12) away from the circular baffle element (70) by a distance corresponding to a second inner diameter D2.

Description

[Technical Field]

[0001] The present invention relates to a measuring device for measuring the flow rate of hydrogen in a pipe. [Background technology]

[0002] Although measuring devices for measuring hydrogen flow rates already exist on the market, they do not function satisfactorily. This is due, among other things, to the difficulty of calibrating the measuring devices due to the material and physical properties of hydrogen. Using less hazardous media, such as helium or other substitute gases, would be expensive or of limited useful value.

[0003] Additionally, flow-related effects external to the measurement device, such as those caused by upstream or downstream control valves, sharp bends in the piping before or after the measurement device, etc., can have a significant effect on the measurement results and are extremely difficult to reproduce during calibration, further complicating calibration. Summary of the Invention [Problem to be solved by the invention]

[0004] In this context, it is an object of the present invention to provide a measuring device for measuring the flow rate of hydrogen that is easy to calibrate and therefore capable of providing reliably reproducible measurements, regardless of the mounting conditions of the measuring device.

[0005] This object is achieved by the measurement device for measuring the flow rate of hydrogen disclosed below. [Means for solving the problem]

[0006] The measuring device comprises a pipe element having a first upstream longitudinal end portion and a second downstream longitudinal end portion each having a first inner diameter D1 (nominal connection diameter) and provided for connection to a pipe, a central longitudinal portion having a second inner diameter D2 larger than D1, and in each case a longitudinal transition portion having a varying inner diameter and provided between the longitudinal end portions and the central longitudinal portion.

[0007] Additionally, there are provided a plurality of radially inwardly extending baffle plates running from the first longitudinal end portion to the central longitudinal portion, a flow conditioner element provided at the upstream end of the central longitudinal portion, and a circular baffle element disposed at the downstream end of the central longitudinal portion so as to be concentric with the tubular member and define an annular gap through which flow can pass.

[0008] Further, a sensor element is provided which measures the flow rate at a measurement point, the measurement point being located on the central longitudinal axis of the pipe member at a distance corresponding to the second inner diameter D2 from the baffle element, i.e., in other words, the measurement point is located at what is known as the stagnation point in front of the baffle element.

[0009] The advantage of this measuring device according to the invention is that the incoming hydrogen gas is perfectly conditioned, so that any influences caused by preceding or succeeding elements of the tube are effectively blocked, in particular blocking external influences makes it possible to effectively calibrate the measuring device.

[0010] In this way, the objective is fully achieved.

[0011] In a preferred development of the invention, the flow conditioner element is configured as a perforated or slotted plate. Perforated plates of this type with a large number of through-openings can be provided simply and cost-effectively. When used for hydrogen with a central longitudinal section having an enlarged diameter D2, a very low pressure drop is also obtained. It should be noted in this respect that the term "perforated plate" is used to mean both perforated and slotted plates. In other words, the geometric shape of the through-openings in the perforated plate may be different, i.e., they may be circular, slotted, etc., or preferably a combination thereof.

[0012] In principle, the function of the perforated plate is to create a flow with as homogeneous a flow profile as possible in the following sections, for example by means of holes with different diameters and slots in the outer area. The holes and slots, as well as their position and free through-flow area, may be determined by CFD (Computational Fluid Dynamics) flow simulations using approximation methods. Only as a second priority should the free cross section be ensured to be as large as possible, for example, 40-50% of the cross-sectional area of ​​the central section, which corresponds to approximately 70-80% of the connecting cross-sectional area.

[0013] In a preferred development, four deflection plates are provided, uniformly spaced apart from one another around the circumference of the tubular member, the use of four deflection plates having been found to be particularly effective in homogenizing the tangential flow.

[0014] In a preferred development, the baffle element has a curved surface, in particular similar to a flattened hemisphere, with the curvature pointing in the opposite direction to the flow. Components of this type can be provided cost-effectively and provide effective flow conditioning, resulting in a reproducible, homogenized annular flow within the pipe. The baffle element in particular has two functions: on the one hand, to create a stagnation point for the measurement, and on the other hand, to prevent flow-related influences caused by subsequent components from acting at the measurement point.

[0015] In a preferred development, the two longitudinal end sections are each provided with a flange for connection to the pipe, this measure having the advantage that the measuring device can be very easily attached to an existing pipe system.

[0016] In a preferred development, the deflector plate has a radially inner edge extending at least partly parallel to the longitudinal axis of the tubular member, this configuration having also proven advantageous.

[0017] In a preferred development, the measuring elements are provided in the form of one or more measuring tips, which are arranged such that they lie at the measuring points.

[0018] As a result of the aforementioned flow conditioning, particularly the reduction in flow velocity, the measurement results are not distorted, the measuring tip is not subjected to excessive cooling, and for some measurement methods, for example mass flow rate measurements using thermal methods, the measurement span is advantageously increased.

[0019] In a preferred embodiment, the inner diameters D2 and D1 are selected to have a ratio of 1.17 to 1.3 (D2 / D1=1.17-1.3), preferably about 1.25. If the inner diameter D1 is, for example, about 80 mm, the second inner diameter D2 is approximately about 100 mm.

[0020] In a preferred development, the baffle elements are formed as dished heads in accordance with German standard DIN 28011. This measure has the advantage that the baffle elements can be provided cost-effectively, since they are standard components. However, it should be noted in this respect that other dished heads deviating from this DIN standard exist and may also be used.

[0021] In a preferred development, the length of the tubular member is 7 to 12 times the first internal diameter D1, and the flow regulator element is positioned 0.5 times D2 from the end of the central longitudinal portion when viewed in the direction of flow.

[0022] In a preferred development, the first longitudinal end portion is provided with a plurality of, preferably four, plates or tabs projecting obliquely inwards in the direction of flow, which has the advantage that the flow can be further regulated to mitigate swirling flows.

[0023] In a preferred development, the flow regulator element has a number of openings of about 30 to 85, the number of openings depending, inter alia, on the nominal diameter of the connection used. It is more preferred if the flow regulator element has both circular and slotted openings, the circular openings having a diameter of about 5 mm to 10 mm, preferably 5 mm to 8 mm.

[0024] In a preferred development, the ratio of the total area of ​​the openings of the flow regulator element to the total cross-sectional area of ​​the central longitudinal portion is between 40% and 50%.

[0025] The aforementioned features have been found to be particularly advantageous with regard to flow straightening.

[0026] The object underlying the present invention is also achieved by using the above-described measuring device in a tube for measuring the flow rate of hydrogen.

[0027] It is understood that the features mentioned above and those to be described below may be used not only in the combination specified in each case, but also in other combinations or alone without departing from the scope of the invention. Further advantages and configurations of the invention are explained in this specification and in the accompanying drawings. [Brief explanation of the drawings]

[0028] [Figure 1a] FIG. 1a shows a longitudinal cross-sectional side view of a measuring device according to the invention. [Figure 1b] FIG. 1b shows a plan view of the measurement device of FIG. 1a as seen from the upstream side of the flow. [Figure 1c] FIG. 1c shows a plan view of the measurement device of FIG. 1a as seen from the downstream side. [Figure 2a] FIG. 2a shows an end view of the measurement device of FIG. 1a looking upstream from the BB plane. [Figure 2b] FIG. 2b shows an end view of the measurement device of FIG. 1a looking upstream from the CC plane. [Figure 2c] Figure 2c shows a perforated plate. [Figure 3] FIG. 3 is a cross-sectional side view of the measuring device of FIG. 1a with dimensions. DETAILED DESCRIPTION OF THE INVENTION

[0029] 1 shows in longitudinal section a metering device according to the invention for measuring the flow rate of hydrogen, the device being designated by the reference numeral 10. The metering device 10 comprises a tubing member 12 adapted for insertion into a pipe (not shown). To this end, the metering device 10 or tubing member 12 has flanges 14, 16 at each of its ends, allowing connection to adjacent pipes at each end.

[0030] Since the measuring device 10 has to be inserted into the pipe depending on the direction or flow, the terms "upstream" and "downstream" are used below, with flange 14 located at the upstream end of the pipe member 12 and flange 16 located at the downstream end, i.e., in other words, the gas to be measured, e.g., hydrogen in this case, enters the pipe member 12 in the region of flange 14 and leaves the pipe member 12 in the region of flange 16, as represented by arrow P.

[0031] To measure the flow rate, the metering device 10 includes a meter 20, the construction and arrangement of which will be described in detail below.

[0032] The tubular member 12 is an elongated structural element having a cavity or interior 13 and is divided into various longitudinal sections, which are designated by reference numerals 31, 32, 34, 35 and 37 in Figure 1a.

[0033] Portion 31 is an end portion 31 of pipe member 12, which is located at the upstream end. As shown in Figure 1a, flange 14 is provided on end portion 31.

[0034] At the opposite end of the tubular member 12, a section 32 also forms an end section 32, which is therefore located at the downstream end and is provided with a flange 16.

[0035] The end portion 31 and the end portion 32 have an inlet opening 15 and an outlet opening 17, respectively, and the opening diameters are the same. Hereinafter, this inner diameter will be represented as D1.

[0036] End portion 31, when viewed in the direction of flow, is adjacent to transition portion 34, the inner diameter of which increases from D1 to a larger inner diameter D2. As shown in Figure 1a, this increase from D1 to D2 is preferably linear.

[0037] When viewed in the direction of flow, this transition section 34 is adjacent to a central section 37, which is provided with a measuring channel for measuring the flow rate. The inner diameter of the central section 37 is constant over its entire length and corresponds to a value D2.

[0038] A transition section 35 is provided between the central section 37 and the end section 32 to reduce the internal diameter D2 to the internal diameter D1 of the outlet opening 17. When viewed in the direction of flow, the transition section 35 initially has an internal diameter D2 which gradually decreases, preferably linearly, to the value D1.

[0039] As shown in Figure 1a, the aforementioned longitudinal portions 31, 34, 37, 35 and 32 extend concentrically about a common longitudinal axis L. The longitudinal extent of central portion 37 is several times greater than the longitudinal extent of each of the other longitudinal portions, the relative proportions of which are explained in more detail below with reference to Figure 3.

[0040] The tubing 12 includes various elements that act to condition the flow in order to provide effective, and particularly repeatable, flow rate measurements. Without these various elements within the tubing 12, the flow conditions within the tubing would vary significantly depending on the geometry of the tubing before and after the tubing 12.

[0041] Provided at the upstream end of the tubular member 12 are a plurality of deflector plates 40, preferably four, uniformly spaced about the periphery of the tubular member. The deflector plates 40 extend radially inward from the inner wall of the tubular member 12, with their radially inner edges 42 running substantially parallel to the longitudinal axis L. Only the two longitudinal end edges 44 and 46 of the deflector plates 40 are angled relative to the longitudinal axis L.

[0042] As shown in Figure 1a, deflector plate 40 extends downstream from inlet opening 15 across end portion 31 and transition portion 34, terminating in the region of central portion 37. When viewed in the direction of flow, this region is located in approximately the first third of central portion 37.

[0043] The function of the deflector plates 40 is, among other things, to reduce what is known as swirl in the incoming hydrogen, which can be caused by elbows or the like upstream of the tubing 12.

[0044] To further homogenize the flow, a flow conditioner 50 is provided in the region of the deflection plate 40 in the central part 37. Preferably, the flow conditioner 50 is configured as a perforated plate 52. Figure 2c shows a perforated plate 52 of this type in detail.

[0045] The perforated plate 52 has a circular shape and a diameter smaller than the inner diameter D2 of the central portion 37. The perforated plate 52 has a plurality of radial notches 54 formed so that one deflector plate 40 can fit into each notch. In this way, the perforated plate 52 can be fixed to the deflector plates 40. As a result, the number of notches 54 corresponds to the number of deflector plates 40 provided, and the diameter of the perforated plate is greater than the diameter of an imaginary circle along the inner edge 42 of the deflector plates 40.

[0046] A plurality of through openings 56 are provided in a circular ring around the peripheral region of the perforated plate 52, with each through opening extending along a circular segment between adjacent notches 54.

[0047] Preferably, a plurality of circular through-openings 58 are provided in the inner region of the perforated plate 52, which inner region is delimited by the through-openings 56. A number of 30 to 85 through-openings has proven particularly advantageous. The diameter of the circular through-openings is in the range of 5 to 10 mm, preferably 5 to 8 mm. Particularly preferably, the ratio of the total area of ​​the through-openings to the total area of ​​the central portion 37 is between 40% and 50%, which corresponds to approximately 70-80% of the cross-sectional area of ​​the end portion 31.

[0048] A further element for adjusting the flow is provided in the end portion 31. It is formed by a plurality of, in particular four, plates 60, which are connected at uniform intervals in the circumferential direction to the inner wall of the end portion 31. The plates 60 are provided as trapezoidal plates that project obliquely inward with respect to the longitudinal axis L and are inclined in the direction of the flow, in other words, the plates 60 deflect the impinging flow in the direction of the flow and towards the longitudinal axis.

[0049] As shown in Figure 1a, four plates 60 are provided, the latter being configured so that they fit or are connected to the deflection plates 40. However, it should be noted in this respect that the plates 60 are optional, i.e. they are not essential elements of the arrangement according to the invention.

[0050] A further element for regulating flow is provided at the other end of central portion 37 in the form of a baffle element 70. Baffle element 70 is formed to be circular and is held concentrically about longitudinal axis L by a plurality of, preferably four, retaining elements 72 on the inner wall of central portion 37. The diameter of baffle element 70 is smaller than inner diameter D2, such that an annular gap 76 is defined between retaining element 72 and the inner wall of central portion 37.

[0051] 1a, the baffle element 70 is positioned immediately before the transition portion 35. The baffle element 70 preferably has two nominal diameters that are smaller than the diameter of the measurement path, i.e., the inner diameter D2 of the central longitudinal portion 37. The ratio of the diameter of the baffle element to the inner diameter D2 of the central longitudinal portion 37 is preferably in the range of 45% to 60%.

[0052] Baffle element 70 is preferably formed to be hemispherical or dome-shaped with angled edge regions 78 generally parallel to longitudinal axis L. Baffle element 70 is also oriented with the curvature pointing upstream, so that the center of the circular baffle element represents the most upstream point when viewed longitudinally. Baffle element 70 could also be formed as what is known as a dish head, preferably in accordance with German standard DIN 28011.

[0053] The function of the baffle element 70 is to build up back pressure, thus forcing the flow into the annular gap 76 while producing a flow profile with as high stability as possible. In this way, the upstream region within the inner portion 37 is flow regulated so that the flow rate can be advantageously metered within this region.

[0054] 1a, at least one metering tip 22 of the metering device 20 is located at a defined metering point 21 (stagnation point) exactly in this flow conditioning area. In particular, the metering tip 22 is located in the area of ​​the longitudinal axis L, i.e., in the center (when viewed radially) of the central portion 37. The exact distance from the metering tip 22, i.e., the metering point 21, to the baffle element 70 will be explained in more detail below.

[0055] In this respect, it should be noted that in this embodiment a measuring device with one or more measuring tips is used to measure the flow rate, but it is understood that other measuring methods may also be used that do not require a measuring tip of this kind, provided that the measurement is performed at a defined measuring point 21. By way of example, possible methods include thermal or even ultrasonic methods.

[0056] The meter 20 comprises a tubular element 24 which projects into the interior 13 through an opening in the wall of the tubular element 12. Furthermore, a metering tip 22 projects from the end of the tubular element 24. It will be seen that a seal 19 is provided in the opening, designated by the reference numeral 18. This seal 19 ensures that hydrogen cannot escape from the interior 13 to the outside through the opening 18, while still allowing the metering tip to be replaced. As already pointed out above, the meter 20 serves to measure the flow rate of hydrogen flowing through the tubular element 12. Since flow meters of this type are known in principle, their mode of operation will not be described further at this time.

[0057] It should also be noted that in connection with the measuring device 20, the increase in the inner diameter from D1 to D2 causes a decrease in the flow velocity, in order to ensure that the flow velocity never exceeds a maximum threshold value in thermal measurement methods, due to the associated cooling of the measuring tip 22. This measure consequently has a positive effect on the measurement results and the measuring range.

[0058] Figures 1b and 1c show plan views of both ends of tubular member 12. For simplicity, the same reference numerals are used in these two figures to represent the same parts as in Figure 1a. Figure 1b clearly shows plate 60 extending radially inward toward longitudinal axis L, the radial extent of which in this case is less than one-third of the radius of inlet opening 15.

[0059] Figures 2a and 2b show the tubular member 12 in two different end views taken along the intersection of lines BB and CC, respectively, again using the same reference numerals as in Figure 1a.

[0060] The dimensions of the tube member 12 and the location of various elements within the tube member 12 will be described with reference to FIG.

[0061] As already mentioned, the diameter of both the outlet opening 17 and the inlet opening 15 has a value D1. This diameter D1 depends on what is known as the nominal diameter (commonly referred to as DN) of the pipe to which the pipe member 12 is connected. Here, a nominal diameter of DN 80 is taken as an example. With a nominal diameter of DN 80, the internal diameter is approximately 80 mm. Therefore, in this case, the internal diameter D2 has a nominal diameter of DN 100, i.e. approximately 100 mm.

[0062] The overall length of the tubular member 12 is 7 to 12 times, preferably 10 times, the inner diameter D1. The distance between the center of the baffle element 70 and the metering tip 22 or generally the metering point 21 is or preferably corresponds to D2, and the distance from the metering tip 22 / metering point 21 to the outlet end 17 of the tubular member 12 is about 2.5 times D2.

[0063] 3 also shows that flow conditioner 50 is preferably located 0.5 times D2 from the beginning of central portion 37. Finally, note that deflector 40 extends radially inward into central portion 37 by approximately 1 / 4 times D2. These dimensions and the location of the elements relative to one another have been found to be particularly advantageous.

[0064] In operation, when tubing 12 is attached to a pipe, hydrogen gas flows into tubing 12 through opening 15 according to arrow P and is further regulated directly by deflector plate 40, and optionally plate 60, and flow regulator 50. Due to the low density and viscosity of hydrogen, the pressure drop across flow regulator 50 is only a few millibars, which is easily acceptable in practice. However, the use of other gases will produce very different results, and so metering device 10 is specifically configured for, and preferably used to, measure the flow rate of hydrogen.

[0065] The increased inner diameter reduces the flow velocity and softens the flow itself, a purpose also served by the downstream baffle element 70. Located at the stagnation point of the baffle element 70 is the measuring point 21, i.e., the measuring tip 22, which allows the flow velocity to be measured. The flow through the annular gap and the baffle element 70 itself also has the advantage that downstream, i.e., subsequent elements or control valves, do not influence the measurement process. Any backward influence of such subsequent control valves is, so to speak, prevented by the baffle element or the annular gap.

[0066] The independence of the measuring device 10 from preceding and succeeding elements in the pipe has the great advantage that the measuring device can be calibrated very accurately on a test bench without having to consider flow conditions outside the tubing 12. These effects are largely counteracted by the elements described.

Claims

1. A measuring device for measuring the flow rate of hydrogen through a pipe, comprising: a pipe element (12) divided into a first upstream longitudinal end portion (31) and a second downstream longitudinal end portion (32) each having a first internal diameter D1 (nominal connection diameter) and intended for connection to a pipe, a central longitudinal portion (37) having a second internal diameter D2 greater than D1, and longitudinal transition portions (34, 35) having in each case varying internal diameters and provided between the longitudinal end portions (31, 32) and the central longitudinal portion (37); a plurality of deflector plates (40) running from the first longitudinal end portion (31) to the central longitudinal portion (37) and extending radially inward; a perforated plate (52) provided at the upstream end of the central longitudinal portion (37); a circular baffle element (70) disposed at the downstream end of said central longitudinal portion (37) so as to be concentric with said tubular member (12) and defining an annular gap (76) through which flow may pass; a sensor element (22) for measuring a flow rate at a measurement point (21), the measurement point (21) being located on the central longitudinal axis (L) of the pipe member (12) at a distance from the circular baffle element (70) corresponding to the second inner diameter (D2); A measuring device comprising:

2. 2. The measuring device according to claim 1, wherein four deflection plates (40) are provided and are uniformly spaced apart from one another in the circumferential direction of the pipe member.

3. 2. The measuring device according to claim 1, wherein the baffle element (70) has a curved surface, in particular similar to a flattened hemisphere, the curvature of which faces against the direction of flow.

4. 2. A measuring device according to claim 1, wherein the two longitudinal end portions (31, 32) are each provided with a flange (14, 16) for connection to a pipe.

5. 3. The measuring device of claim 1 or 2, wherein the deflector (40) has a radially inner edge (42) extending at least in part parallel to the longitudinal axis (L) of the tubular member.

6. 2. The measuring device according to claim 1, wherein the tubular member (12) has an opening (18) in its wall through which a sensor chip (22) can be inserted as a sensor element.

7. 2. The measuring device according to claim 1, wherein the ratio of the second inner diameter D2 to the first inner diameter D1 is in the range of 1.17 to 1.3, preferably 1.

25.

8. 2. The measurement device of claim 1, wherein the perforated plate (52) has a number of openings between 30 and 85.

9. 9. The measurement device of claim 8, wherein the perforated plate (52) has both circular and slot-shaped openings, the circular openings having a diameter of 5 mm to 8 mm.

10. 10. The measuring device according to claim 8 or claim 9, wherein the ratio of the total area of ​​the openings in the perforated plate (52) to the total cross-sectional area of ​​the central longitudinal portion (37) is between 40% and 50%.

11. 2. The measuring device according to claim 1, wherein the baffle element (70) is configured as a dish head, preferably in accordance with German standard DIN 28011.

12. 12. The measuring device of claim 11, wherein the ratio of the diameter of the baffle element (70) to the inner diameter D2 of the central longitudinal portion (37) is in the range of 45% to 60%.

13. 13. The measuring device of claim 1, 11 or 12, wherein the baffle element (70) is connected to the tubular member by a plurality of, preferably four, radially arranged support plates (72).

14. 2. The measuring device according to claim 1, wherein the length of the tubular member (12) is 7 to 12 times, preferably 10 times, the first inner diameter D1.

15. 2. The measuring device according to claim 1, wherein the perforated plate (52) is spaced 0.5*D2 from the beginning of the central longitudinal portion (37) when viewed in the direction of flow.

16. 2. A measuring device according to claim 1, characterized in that the first longitudinal end portion (31) is provided with a plurality of, preferably four, plates (60) which project obliquely inwards in the direction of flow.

17. 10. Use of a measuring device according to claim 1 for measuring the flow rate of hydrogen through a tube.

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