DK177824B1

DK177824B1 - Flow channel

Info

Publication number: DK177824B1
Application number: DK201300197A
Authority: DK
Inventors: Frands Wulff Voss; Hans Byrdal Nielsen
Original assignee: Flonidan As
Priority date: 2013-04-02
Filing date: 2013-04-02
Publication date: 2014-08-18

Abstract

The present invention relates to a device for flow measuring primary for gas flow in a flow channel cooperating with a first and a second ultrasound transducers are placed in connecting branches with an angle T in relation to the flow channel, which connection branches comprises set back filters. It is the object of the pending patent application to achieve a highly efficient and accurate measurement of a gas flow. The object can be fulfilled if the set back filter is formed as a plate of a rigid material, which plate comprises a plurality of longitudinal openings, which longitudinal openings have a length related to the angle T. Because the transducers are placed in side branches to the housing, a flow of gas or liquid through the housing will generate a vortex, where the gas streaming through the device is in contact with mostly stagnant gas in the pipe branch carrying the transducer. As one transducer often is placed upstream and another one is placed downstream, different vortex flow can be generated in relation to the two transducers. Because the vortex depends on the flow, the set point of the measured values is highly influenced, if these vortexes are not reduced.

Description

DK 177824 B1 i

Flow channel Field of the Invention

The present invention relates to a device for flow measuring primarily for gas flow, 5 which device comprises an inlet and an outlet and there between at least one flow channel, which flow channel cooperates with at least a first and a second ultrasound transducer, which first or second ultrasound transducer transmits ultrasound across the flow channel towards the second or first ultrasound transducer, which ultrasound transducers are placed in connecting branches, which connection branches are placed 10 by an Z T in relation to the flow channel, which connection branches comprises setback filters in the connection branches connected to the flow channel.

Background of the Invention A device for flow measuring is known from an unpublished patent application DK PA 15 2012 70241 which invention relates to a system or a method for measuring flow in a flow duct comprising at least two ultrasound transducers. It is the object of that application to measure the flow of air in a duct by one or more transducers transmitting beams of ultrasound controlled by a microcontroller based electronic system. The object can be achieved, if the microcontroller stores a vector of data samples for each 20 direction of transmission, which vector comprises an appropriate number of N samples forming a frame, which microcontroller multiplies each value of the frame with a complex number, which microcontroller based on the result calculates the flow in the duct. By the invention according to the present patent application an efficient flow measurement of air flowing in a duct can be achieved.

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Object of the Invention

It is the object of the pending patent application to achieve a highly efficient and accurate measurement of a gas flow. A further object of the pending application is to perform an efficient closing of the device to stop a gas flow.

30 DK 177824 B1 2

Description of the Invention

The object can be fulfilled by a device as disclosed in the preamble of claim 1 which is further modified so the device comprises a valve, which valve is placed for closing the inlet, which inlet is formed as a valve seat, which valve seat cooperates with a 5 valve closure element, which valve closure element is carried by at least one arm, which arms rotates around an axel by motor means. Closing the inlet automatically gives the possibility that if there is measured a value so high that it indicates that a leak exist somewhere after the device in a gas supply line. A too high flow can therefore be interrupted by closing of the valve. The electronic circuit controlling the valve 10 functions as well as the system calculates the measured flow can in that way supervise a supply line in a rather efficient way. It should be possible to tell the device >vhat the maximum allowed flow is, and if that value is reached by actual flow, the valve could be closed. The electronic control of the valve can be performed by a step motor such as a micro DC gear motor which is controlled by the electronic device. By using a step 15 motor the electronic system will know the exact axial position of the step motor. Hereby the actual valve position can be calculated without any kind of detectors. By a simple gear mechanism it is possible to control the position of the valve to an extremely high degree. The valve is constructed so that when the valve is closed, the gas or water pressure will further close the valve. Opening of the valve will therefore only 20 be possible, if the step motor can generate sufficient force for the gear mechanism to open the valve.

In a further preferred embodiment of the invention the housing can basically constitute the bearings of the drive shaft of the valve. Hereby it can be achieved that the shaft 25 bearings are generated automatically by the moulding process for the upper part of the housing.

In a further preferred embodiment of the invention the port can be mounted on the arm(s) in such a way that it may vary by a small angle of up to e.g. app. 15 degrees in 30 angle around the neutral position in order to absorb tolerances in the construction so as to ensure proper sealing when the valve is closed. Hereby the valve can be manufactured in a moulding process where even a rather large tolerance has no effect on the closing function of the valve.

DK 177824 B1 3

In a farther preferred embodiment of the invention the device can comprise a pilot valve, which pilot valve controls a main valve. By an alternative embodiment of the invention a pilot valve can be controlled by the electronic circuit, and this pilot valve 5 will then open for a gas or water flow, which flow will open the main valve. Pilot operated valves are well-known, and therefore the pilot valve system is not farther disclosed.

In a farther preferred embodiment of the invention the device can be placed in an out-10 er pressure-tight housing, which device is carried at a first set of legs at the inlet and a second set of higher legs at the outlet, whereby a cleaning activity of the gas is performed in that liquid or solid drops or particles are falling down in the outer housing. Hereby cleaning of the gas can be performed arid pollution in the form of liquid drops or solid particles remains in the outer housing where the pollution can be stored for a 15 longer period of time.

In a farther preferred embodiment of the invention can the device be farther modified so that a setback filter is formed as a plate of a rigid material, which plate comprises a plurality of longitudinal openings, which longitudinal openings have a length related 20 to the ZT.

Because the transducers are placed inside branches of the housing, a flow of gas or liquid through the housing may generate a vortex where the gas streaming through the device is in contact with mostly stagnant gas in the pipe branch carrying the transduc-25 er. As one transducer often is placed upstream and another one is placed downstream, different vortex flows can be generated in relation to the two transducers. Because the vortex depends on the flow, the set points of the measured values are highly influenced, if these vortexes are not reduced. It is well-known to use a mesh as setback filter but a mesh has the disadvantage that it reduces the oscillations generated by the 30 transducers. By the pending application instead there is used a rigid material comprising a plurality of holes. The number of holes is relatively high whereby the setback filter is kept as open as possible and for reducing the possibility of generating vortexes result in the oscillations generated from one of the transducers being transmitted throughthe holes in the rigid plate, At the receiving transducer it is highly efficient DK 177824 B1 4 that the setback filter is as open as possible, and at the receiving setback filter it is possible that the oscillations are transmitted through the rigid material. As already mentioned, the effect of the setback filters is well-known but the effect of the setback filter is further improved as previously described by using the rigid setback filter.

5

In a preferred embodiment of the invention the flow tube can be divided in the longitudinal direction in at least two separate flow channels by at least one straightener.

Dividing a flow channel by straighteners will divide the flow channel into two or more 10 separate flow channels. As the straighteners formed as rigid plates are placed horizon tally and in that way perpendicularly to the ultrasound, the ultrasound can be transmitted through the gas between the rigid straightener plates. Hereby it is achieved that the flow of gas or maybe a liquid through the device will primarily be linearly flowing in the area where ultrasound measurement is performed. Hereby it can be achieved that 15 the flow measurement will be performed linearly over a large spectrum of different flow velocities.

In a further preferred embodiment of the invention the ultrasound transducers are kept in place in the connection branches in sleeves, which sleeves are formed of an elastic 20 material such as rubber. Hereby it is achieved that the oscillations generated by the ultrasound transducers are isolated so that no oscillations are transmitted to the housing. If oscillations were transmitted to the housing, false signals could in that way greatly influence the efficiency of the measured signals. Because the received signals are relatively weak, the weak signals might disappear completely in mechanical vibra-25 tions transmitted through the housing. Therefore soft fixing of the transducers is highly efficient.

In a further preferred embodiment of the invention the device can comprise a housing, which housing is formed of at least a lower and an upper main part, which lower main 30 part comprises one or more slits for fastening a first lower straightener, which housing in the connection zone between the lower and upper main parts the housing comprises one further slit for fastening a second upper straightener. In this way a housing can be formed e.g. as a moulded plastic component which component is designed in such a way that a plurality of straightener plates automatically can be fitted into different DK 177824 B1 5 slits. Hereby no further fastening means for the straighteners are necessary. As soon as they are placed in the slits, they can be fixed by e.g. snap actions in the slits so they remain in place during operation of the device.

5 In a preferred embodiment of the invention the two parts of the housing can comprise one or more click locks whereby the flow channel is simply pressed together and then basically being gas-tight to a differential pressure of up to 0.5 bar. Hereby a highly efficient assembly can be achieved, and the tightening to pressure difference to an outer housing is sufficient.

10

In a further preferred embodiment of the invention, two parts of the housing can be clicked together, and at the same time as a gluing or 'welding' is performed, whereby the device is leak-proof against up to at least 0.5 bar differential pressure. Hereby efficient tightening to a much higher pressure difference can be achieved.

15

In a further preferred embodiment of the invention both the lower and upper main parts of the housing comprise one or more slits for said setback filters. The said back filters can be placed in slits in the housing. This will also lead to automatic fixation of 20 said setback filters.

In a further preferred embodiment of the invention the setback filter can be made of a metal sheet which metal sheet comprises a number of small openings, which openings comprise a first and a second dimension, where an optimized relation between the 25 dimensions is achieved when the dimensions are almost equal as seen from one of the transducers. Hereby it can be achieved that the ultrasound waves will penetrate the openings in the setback filter as the openings are mainly circular. If the length of the opening is designed in accordance with the actual angle T, a simple mathematical calculation can read the correct length of the opening in order to fulfil a request for 30 achieving a mostly circular opening in the direction of the ultrasound wave propagation. As an alternative to the previously disclosed openings, other profiles can be a possible solution, such as rectangles seen as a square from the transducers. All profiles are in fact possible; the only limitation seems to be the production of a plurality of holes in a plate.

DK 177824 B1 6

This invention further concerns a method for flow measuring in a device as disclosed 5 previously, which method is disclosed in the following sequence of steps: a. Inlet of gas into an outer gas-tight housing surrounding the device disclosed in one of the claims 1-12, b. Let the gas perform a 90 degrees turn in passing into the device, 10 c. Let the gas flow into the device upwards from inlet to outlet d. direct the gas flow by straighteners to perform a mostly laminar flow e. reduce vortex generation by setback filters f. let transducers one by one transmit ultrasound across the flow channel g. perform flow measuring 15 h. let the gas perform a mostly 90 degrees turn at the outlet of the device.

Hereby is achieved that flow measurement is performed highly effective independent of the flow of gas. Further is performed a cleaning of the gas because of the distance between outer housing and the device an in that the lowest point for the flow is the 20 inlet to the device. Further cleaning of the gas is achieved by the upwards direction of the outlet of the device.

The flow channel can be designed with the aim of reducing the flow resistance for the gas flow, which flow channel comprises at least the following features or just some of 25 these: a. the inlet is designed with larger area than actually optimal for the gas flow of a certain meter size, 30 b. the channel is formed straight for generating a laminar flow, c. the channel continues smooth to fit into the outlet, d, the outlet is designed with larger area than the minimum area for the actual gas flow.

DK 177824 B1 7

Hereby it can be achieved that the same device can be used in at least two different gas measuring systems designed for different flows, such as for example G4 and G6.

5 Description of the Drawing

Fig. 1 shows a possible embodiment for a device.

Fig. 2 shows an exploded view of some of the components of the device shown at fig. 1.

Fig. 3 shows a sectional view of a part of fig. 1.

10 Fig. 4 shows an embodiment for a setback filter.

Fig. 5 shows a preferred embodiment for a setback filter.

Fig. 6 shows an enlarged sectional view of the setback filter at fig. 5 Fig. 7 shows mostly the same embodiment as fig. 6, but now seeing in a 45 degrees side view.

15 Fig. 8 shows another embodiment for a setback filter, where

Fig. 9 shows the same embodiment, but now seen from a 45 degrees angle.

Detailed Description of the Invention

Fig. 1 shows a device 2 which device comprises an outlet 4 and a not shown inlet. The 20 device comprises a housing 6 which housing has supporting legs 8 and 10, which houses 6 comprise a lower section 12 and an upper section 14. The upper section is closed by a top 15. Further, comprises the device 2 a transducer locking mechanism 16 and 18, where a transducer is seen and indicated as 20. Further, are indicated arms 22 and 24. These arms are connected to a valve closing element 26, which is cooperat-25 ing with a rubber closure 28.

In operation will the valve element 26,28 be opened because the arm 22 and 24 are rotated so that the valve is open and a flow to the device will be possible. The ultrasound transducers 20 are transmitting ultrasound across the flow channel in an angle 30 of approx. 45 degrees where the transducers are transmitting one-by-one and shifting between transmitter and receiver. A not shown electronic system which is placed below the cover 15 calculates the actual flow through the device. The electronic device as such can also comprise communication means so such as Wi-Fi communication or DK 177824 B1 8 maybe Bluetooth. The electronic system also controls the valve 26,28 by a not shown step motor, it is possible to rotate an axle and then rotate the arms 22 and 24. The use of a step motor is very effective in that the position of the step motor is in nearly all situations well-known from the control electronics. That means no further sensors are 5 necessary to indicate the position of the valve 26,28. The control system will always know exactly where the position of the valve is.

Fig. 2 shows an exploded view of the device 2 as seen at fig. 1. The housing 6 seen at fig. 1 shows at fig. 2 a bottom part 12 and an upper part 14. The lower part 12 com-10 prises a slit 13 for a straightener. The upper part of the housing 14 comprises a slit 17 for a straightener. Further, at fig. 2 is indicated fixation means 16 and 18 for fixing not shown ultrasound transducers. The upper part 14 of the housing comprises a cavity 19, which is covered by a closure 15. The cavity 19 forms a housing for an electronic circuit not shown. This electronic circuit comprises analog interphase for as well trans-15 mitting and receiving ultrasound by the transducers 20. Further, comprises the electronic device computer means which performs also analog digital conversion of measured values. This computer means further comprises different communication means such as Wi-Fi or Bluetooth communication. Electronic circuit further comprises a control circuit for controlling a step motor not shown. This step motor is connected to a 20 tooth wheel mechanism where one tooth wheel 40 is shown, the tooth wheel always together with a shaft 38. To this shaft is connected arm 22 and 24. These arms are further connected to first a mechanical valve closure 26 which further is connected to a rubber packing material 28.

25 In use the device 2 will be able to measure a flow that is passing through the valve channel placed below the cavity 19. The flow will be measured because ultrasound waves are transmitted across the flow in both directions and difference in travelling velocity for ultrasound is used to calculate the speed of the flow. In situation where for example the flow increases and reach a critical value it is important that a valve as 30 indicated also at fig. 2 can be closed to stop the flow. Especially if it is a device for measuring a gas flow it can be important to close for the flow in an emergency situation. Therefore, a valve with a valve seat 28 and valve actuation means 26 and arms 22 and 24 perform an active closing the valve because the rubber closure 28 will be pressed against the valve seat. This valve seat is formed as the end of the lower sec- DK 177824 B1 9 tion 12 of the housing and the upper section 14. Further, is indicated at fig. 2 a first lower slit 13 and an upper slit 17. These slits are used for receiving straighteners for dividing the flow channel into three parallel sections. In this way can be avoided that a gas flow is flowing in a turbulent manner. By separating in small flow channels it is 5 possible to have a mostly linear flow through the device. Measuring by ultrasound is always performed with a best result if there is a linear flow through the flow channel.

Fig. 3 shows a sectional view of the device shown in fig. 1. This sectional view shows two slits 30 and 32 for the straighteners. Further, is shown a setback filter 34. Both the 10 straighteners and the setback filters have more or less the same purpose of reducing turbulent flow in the flow channel. The setback filter has that effect that gas or maybe water that is around the transducers is kept mostly as silent as possible. Therefore, is the setback filter able to let at least some of the ultra-wave oscillations passing through the filter. But the filter has to have relative small openings in order to separate 15 the linear flow through the channel to the flow in the side branches housing the trans ducers. If no setback filters were in placed a vortex in the side branches could be generated. Such a vortex will have negative influence in the measurement that is performed by ultrasound. The reliability of the measured signals will be reduced and there will maybe be a negative influence of the accurate of the measurement.

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Fig. 4 shows one possible embodiment for a setback filter 36; This setback filter is made with circular openings 42. In the setback filter 36 are the holes placed nearly as close to each other as possible in order to have a high degree opening in the setback filter.

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Fig. 5 shows a preferred embodiment for a setback filter 44. The holes 46 that are used in the embodiment shown as figure 5 are longitudinal.

The holes are further indicated at the fig. 6 where it is to be seen that the hole 46 in 30 one dimension has the size of 0.24 mm and in the other dimension has a size of 0.5 mm. The centre of said off set between holes in the first direction is 0.3 mm and in the other direction 0.25 mm.

DK 177824 B1 10

Fig. 7 shows the same section of a filter 44 as fig. 6, but now seen in an angle of 45 degrees. The longitudinal holes 46 are now seen as circular openings. Hereby is received that if a transducer is placed in a side branch that has an angle of 45 degrees seen from the transducer openings are circular. Hereby can be achieved a relative ef-5 fective setback filter with a relative good degree of opening for the ultrasound waves.

Fig. 8 shows a sectional view of a filter 36 as disclosed as fig. 4, where fig. 9 shows the same filter seen from an angle of 45 degrees. Here it can be seen that there is a very limited opening 42 for ultrasound waves to pass through the filter.

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Claims

Device (2) for flow measurement, preferably for gas streams, said device comprising an inlet and an outlet (4) and therebetween at least one flow channel, which flow channel cooperates with at least one first and a second ultrasonic transducer (20), which first or second second ultrasonic transducer (20) transmits ultrasound across the flow channel toward the second or first ultrasonic transducer (20), which ultrasonic transducers (20) are located in terminal blocks located with a ZT relative to the flow channel, characterized in that the device comprises a valve ( 26, 28), which valve (26, 28) is arranged for closing the inlet, which inlet is formed as a valve seat cooperating with a vertebral closure element (26, 28), the valve closure element (26, 28) being carried by at least an arm (22, 24) pivoting about a shaft (38), the arm (s) (22, 24) rotating about the shaft (38) with motor means.

Device for flow measurement according to claim 1, characterized in that the housing is essentially a bearing for the drive shaft of the valve (38).

Flow measurement device according to claim 1 or 2, characterized in that the gate (26, 28) is mounted on the arm (s) in such a way that it can vary with a small angle up to 20 approx. 15 ° at an angle about the initial position to absorb tolerances in the structure to ensure proper sealing when the valve is closed.

Device for flow measurement according to one of the preceding claims, characterized in that the device comprises a pilot valve which controls the main valve. 25

Device for flow measurement according to one of the preceding claims, characterized in that the device (2) is located in an outer pressure-tight housing, which device is carried by a first set of legs (8) at the inlet and a second set of higher legs (10). at the outlet (4), whereby a cleaning activity of the gas is effected by liquid or solid droplets or particles 30 falling into the outer housing.

Flow measurement device according to one of the preceding claims, characterized in that the connection nozzles comprise non-return filters (34,36,44) in the connection nozzles of the flow channel, which non-return filter (34,36,44) is formed as a plate of rigid material comprising a plurality of longitudinal openings (46) having a length related to Z T.

Device for flow measurement according to claim 6, characterized in that the flow channel is longitudinally divided into at least two separate flow channels with at least one baffle (30.32).

Device for flow measurement according to claim 6 or 7, characterized in that the ultrasonic transducers (20) are held in place in the connection pins in cuffs formed of an elastic material such as rubber.

Device for flow measurement according to one of claims 6-8, characterized in that the device (2) comprises a housing formed by at least one lower (12) and an upper (14) main part, which lower main part (12) comprises one or more slots (13) for attaching a first lower baffle (30), which housing in the connection zone between the lower and upper parts further comprises one or more slots (17) for attaching a second upper baffle (32).

Device according to one of claims 6-9, characterized in that the two parts (12, 14) comprise one or more snap locks, whereby the flow duct is simply compressed and then is basically gas tight with a differential pressure of up to 0.5 bar.

Device according to claim 10, characterized in that the two parts (12, 14) are clicked together and at the same time a bonding or welding is performed, the device being close to a differential pressure of up to at least 0.5 bar.

Flow measurement device according to one of claims 6 to 11, characterized in that both the lower (12) and the upper (14) main part of the housing comprise one or more slots for the recoil filters (34, 36, 44).

Device for flow measurement according to one of claims 6-8, characterized in that the non-return filter (34,36,44) is made of a metal plate comprising a plurality of small openings (40), which openings (40) comprise a first and second dimensions, where an optimized relation between the dimensions is obtained when the dimensions are almost identical from one of the transducers (20).

Method for flow measurement in a device according to any of the preceding claims, characterized by the following sequence of steps: a. Inlet of gas into an outer gas-tight housing surrounding the device described in one of claims 1-13, b. perform an approximately 90 ° turn when passing into the device, 10 c. allow the gas stream to flow upwardly from inlet to outlet, d. direct the flowing gas with baffles to provide a substantially laminar flow, e. reduce vortex generation with non-return filters. , f. allow to transduce one by one transmitting ultrasound across the flow channel, 15 g. perform flow measurement, h. allow the gas to perform a substantially 90 ° turn at the outlet of the device.

Method according to claim 14, characterized in that the flow channel is designed to reduce the flow resistance of the gas flow, which flow channel 20 comprises at least one of the following features: a. The inlet is designed with a larger area than the actual optimum for the gas flow for a particular meter size, b. The duct is designed just for generating a largely laminar flow, c. The duct goes smoothly into the outlet, 25 d. The outlet is designed with a larger area than the minimum area for the actual gas flow.