FLOW MEASUREMENT

Abstract

A device for measuring a flow of a medium through a pipe, wherein the device includes multiple pitot tubes and multiple sensing units, each of the pitot tubes has a respective total pressure outlet and a respective static pressure outlet, each of the sensing units has a respective total pressure inlet and a respective static pressure inlet, all of the total pressure outlets are fluidly connected to all of the total pressure inlets by respective first connection lines, all of the static pressure outlets are fluidly connected to all of the static pressure inlets by respective second connection lines, and each of the sensing units is configured to determine the flow of the medium through the pipe by comparing the pressures at the respective total pressure inlet and the respective static pressure inlet with each other.

Claims

1. A device for measuring a flow of a medium through a pipe, wherein the device comprises multiple pitot tubes and multiple sensing units, wherein each of the pitot tubes has a respective total pressure outlet and a respective static pressure outlet, wherein each of the sensing units has a respective total pressure inlet and a respective static pressure inlet, wherein all of the total pressure outlets are fluidly connected to all of the total pressure inlets by respective first connection lines, wherein all of the static pressure outlets are fluidly connected to all of the static pressure inlets by respective second connection lines, wherein each of the sensing units is configured to determine the flow of the medium through the pipe by comparing the pressures at the respective total pressure inlet and the respective static pressure inlet with each other, and wherein all first connection lines include a first shared tube segment and/or all second connection lines include a second shared tube segment.

2. The device according to claim 1, wherein the pitot tubes are averaging pitot tubes.

3. The device according to claim 1, wherein the first connection lines have the same length and/or wherein the second connection lines have the same length.

4. The device according to claim 1, wherein at least two of the total pressure outlets are connected to the first shared tube segment via a T-junction and/or wherein at least two of the static pressure outlets are connected to the second share tube segment via a T-junction.

5. The device according to claim 1, wherein the first shared tube segment is connected to the total pressure outlets via a first manifold of T-junctions and/or wherein the second shared tube segment is connected to the static pressure outlets via a second manifold of T-junctions.

6. The device according to claim 1, wherein all total pressure inlets are connected directly to the first shared tube segment and/or wherein all static pressure inlets are connected directly to the second shared tube segment.

7. The device according to claim 1, wherein all total pressure inlets are connected directly to an axial center of the first shared tube segment and/or wherein all static pressure inlets are connected directly to an axial center of the second shared tube segment.

8. The device according to claim 1, wherein all first connection lines cover the same length between the respective total pressure outlet and the first shared tube segment and/or wherein all second connection lines cover the same length between the respective static pressure outlet and the second shared tube segment.

9. An arrangement comprising a pipe and a device for measuring a flow of a medium through the pipe, wherein the device is configured according to claim 1.

10. The arrangement according to claim 9, wherein the pitot tubes are spaced apart from each other along an axis of the tube.

11. The arrangement according to claim 9, wherein in a cross-section of the pipe each of the pitot tubes is oriented differently.

12. The arrangement according to claim 11, wherein in a cross-section of the pipe all pitot tubes enclose an angle in the range of 30 and 60° with the respective neighboring pitot tube.

13. The arrangement according to claim 9, wherein in a cross-section of the pipe the pitot tubes are arranged parallel to each other.

14. The arrangement according to claim 9, wherein the pipe has a cross-sectional area of at least 1 m.sup.2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In the following the invention will be described with respect to the figures. The figures show a preferred embodiment, to which the invention is not limited. The figures and the dimensions shown therein are only schematic. The figures show that:

[0052] FIG. 1 is a first embodiment of a device according to the invention,

[0053] FIG. 2 is a perspective view of an arrangement according to the invention including the device of FIG. 1,

[0054] FIG. 3 is a cross-sectional view of the arrangement of FIG. 2,

[0055] FIG. 4 is a second embodiment of a device according to the invention,

[0056] FIG. 5 is a perspective view of an arrangement according to the invention including the device of FIG. 4,

[0057] FIG. 6 is a cross-sectional view of the arrangement of FIG. 5.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0058] FIG. 1 shows a device 1 for measuring a flow of a medium through a pipe 2 (which is shown in FIGS. 2 and 3). The device 1 can be used, in particular, to measure the flow of an exhaust gas flowing through the pipe 2.

[0059] The device 1 comprises four pitot tubes 3 that are configured as averaging pitot tubes. The pitot tubes 3 can be used to measure the dynamic pressure within the pipe 2, from which the flow of the medium can be determined. The dynamic pressure can be obtained as the difference between the total pressure and the static pressure. In order to be able to use these two parameters, each of the pitot tubes 3 has a respective total pressure outlet 5 and a respective static pressure outlet 6. The outlets 5,6 are fluid outlets at which a pressure equals the total pressure or the static pressure within the pipe 2, respectively. That is, at the outlets 5,6 the pressure is output as an actual physical quantity and not as an electrical signal. The device 1 further comprises four sensing units 4. With the sensing units 4, the pressures from the outlets 5,6 are processed. Therefore, each of the sensing units 4 has a respective total pressure inlet 7 and a respective static pressure inlet 8. Each of the sensing units 4 is configured to determine the flow of the medium through the pipe 2 by comparing the pressures at the respective total pressure inlet 7 and the respective static pressure inlet 8 with each other.

[0060] In order to be able to process the pressures from the outlets 5,6 by the sensing units 4, the outlets 5,6 are connected fluidly to the inlets 7,8. Thereby, all of the total pressure outlets 5 are fluidly connected to all of the total pressure inlets 7 by respective first connection lines 9 and all of the static pressure outlets 6 are fluidly connected to all of the static pressure inlets 8 by respective second connection lines 10. All first connection lines 9 include a first shared tube segment 11 and all second connection lines 10 include a second shared tube segment 12. Thereby, the total pressure from the four total pressure outlets 5 is averaged and the static pressure from the four static pressure outlets 6 is averaged. This averaging is an addition to the averaging obtained because the pitot tubes 3 are already averaging pitot tubes 3. Hence, at all total pressure inlets 7 the same total pressure is present and at all static pressure inlets 8 the same static pressure is present. All four sensing units 4 are therefore provided with the same pressures to determine the flow of the medium through the pipe 2. This is even true if some of the pitot tubes 3 fail. That is, the flow can be determined if at least one of the four sensing units 4 and at least one of the four pitot tubes 3 are operational. This applies to any combination of the sensing units 4 and the pitot tubes 3. Due to this redundancy, the device 1 is particularly fail-safe.

[0061] In order to have the pressures at the total pressure inlets 7 of the sensing units 4 to be as similar to each other as possible, the first connection lines 9 have the same overall length and cover the same length between the respective total pressure outlet 5 and the first shared tube segment 11. Similarly, in order to have the pressures at the static pressure inlets 8 of the sensing units 4 to be as similar to each other as possible, the second connection lines 10 have the same overall length and cover the same length between the respective static pressure outlet 6 and the second shared tube segment 12. Also, all total pressure inlets 7 are connected directly to an axial center of the first shared tube segment 11 and all static pressure inlets 8 are connected directly to an axial center of the second shared tube segment 12.

[0062] Each of the total pressure outlets 5 is connected to the first shared tube segment 11 via a T-junction 13 and each of the static pressure outlets 6 is connected to the second shared tube segment 12 via a T-junction 13. To this end, the first shared tube segment 11 is connected to the total pressure outlets 5 via a first manifold 14 of T-junctions 13 and the second shared tube segment 12 is connected to the static pressure outlets 6 via a second manifold 15 of T-junctions 13.

[0063] One of the sensing units 4 is connected to a basic process control system (BPCS) 17. The further sensing units 4 are connected to an emergency shutdown device (ESD) 18.

[0064] FIG. 2 shows a perspective view of an arrangement 16 including the device 1 of FIG. 1 as well as a pipe 2. The pitot tubes 3 of the device 1 are arranged within the pipe 2. This means that the pitot tubes 3 are arranged such that they can be used to measure the flow of the medium through the pipe 2. In particular the total pressure outlets 5 and the static pressure outlets 6 can be placed outside of the pipe 2. The pitot tubes 3 are spaced apart from each other along an axis A of the tube 2. In a cross-section of the pipe 2 perpendicular to the axis A each of the pitot tubes 3 is oriented differently in that all pitot tubes 3 enclose an angle of 45° with the respective neighboring pitot tubes 3. The pipe 2 has a cross-sectional area of at least 1 m.sup.2.

[0065] With the described device 1 the flow of a medium through a pipe 2 can be measured reliably and accurately even if the flow is not uniform across the cross-section of the pipe 2. This is due to the fact that the connection lines 13,14 between the outlets 5,6 of the pitot tubes 3 and the inlets 7,8 of the sensing units 4 include the shared tube segments 11,12.

[0066] FIG. 3 shows a cross-sectional view of the arrangement 16 of FIG. 2. In particular from this figure it can be seen that all pitot tubes 3 enclose an angle of 45° with the respective neighboring pitot tubes 3.

[0067] FIG. 4 shows a second embodiment of a device 1 for measuring a flow of a medium through a pipe 2. This embodiment is similar to the embodiment of FIG. 1. The difference is that according to FIG. 4 there are only three pitot tubes 3. The connection lines 9,10 are configured accordingly.

[0068] FIG. 5 shows a perspective view of an arrangement 16 including the device 1 of FIG. 4. Herein, it can be seen that all pitot tubes 3 enclose an angle of 60° with the respective neighboring pitot tubes 3. This can be seen even better in FIG. 6, which is a cross-sectional view of the arrangement 16 of FIG. 5.

LIST OF REFERENCE NUMERALS

[0069] 1 device [0070] 2 pipe [0071] 3 pitot tube [0072] 4 sensing unit [0073] 5 total pressure outlet [0074] 6 static pressure outlet [0075] 7 total pressure inlet [0076] 8 static pressure inlet [0077] 9 first connection line [0078] 10 second connection line [0079] 11 first shared tube segment [0080] 12 second shared tube segment [0081] 13 T-junction [0082] 14 first manifold [0083] 15 second manifold [0084] 16 arrangement [0085] 17 basic process control system (BPCS) [0086] 18 emergency shutdown device (ESD) [0087] A axis

[0088] It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above.