METHOD FOR DETERMINING A GAS AMOUNT AND DEVICE FOR CARRYING OUT SAID METHOD

Abstract

A method is for determining a gas amount, which can be dispensed by a dispensing device, in particular in the form of a hydrogen gas amount, by a gas meter (36). A part of the main gas stream flowing to the dispensing device (26) is branched off by a flow divider (20) mounted upstream of the dispensing device (26), when viewed in the direction of the gas stream, for a quantitative measurement in the secondary flow by the gas meter (36).

Claims

1-10. (canceled)

11. A method for determining a gas amount dispensed by a dispensing device, comprising the steps of: branching off a part of a main flow flowing toward a dispensing device by a flow divider to provide a secondary flow, the flow divider being mounted upstream of the dispensing device in a direction of gas mass flow; and quantitatively measuring the secondary flow by a gas meter.

12. A method according to claim 11 wherein the main flow is hydrogen gas.

13. A method according to claim 11 wherein a total gas mass flow upstream of the flow divider is proportionally divided by the flow divider at a specifiable ratio of the secondary flow to the main flow.

14. A method according to claim 13 wherein a gas amount in the secondary flow is smaller than a gas amount in the main flow and is adjusted by a differential control valve on an outlet side of the differential central valve to a respective pressure in the main flow independently of an actuation status of the dispensing device.

15. A method according to claim 14 wherein a gas pressure in the secondary flow is higher than a gas pressure in the main flow; and the differential control valve is a pressure control valve opening a measuring line into which the gas amount in the secondary flow is discharged until a pressure balance is restored in the main flow and in the secondary flow.

16. A method according to claim 15 wherein the gas amount in the measuring line is expanded and tempered by a heat exchanger.

17. A method according to claim 16 wherein the gas amount in the measuring line is brought to ambient temperature

18. A method according to claim 16 wherein the gas amount in the measuring line is supplied to the gas meter after being expanded and tempered by the heat exchanger; and the gas meter is connected at an outlet side thereof via a dispensing line to a prestressing device such that the gas amount discharged from the gas meter into the dispensing line proportionally corresponds to the gas amount discharged in the main flow by the dispensing device.

19. A method according to claim 18 wherein the gas meter comprises a low pressure gas meter.

20. A method according to claim 18 wherein the prestressing device comprises a check valve.

21. A method according to claim 11 wherein an electronic volume converter is connected to a gas meter such that a pressure and a temperature of a gas amount in the gas meter is determined for precisely calibrated conversion of the gas amount in the gas meter to standard cubic measurements as an amount dispensed by the dispensing device.

22. A method according to claim 18 wherein the gas amount discharged from the gas meter into the dispensing device is discharged into at least one of a surrounding environment via a chimney or to a tank from which the dispensing device takes stored gas.

23. A measuring device for determining a gas amount dispensed by a dispensing device, the measuring device comprising: a gas dispenser; a flow divider connected to said dispenser upstream of said dispenser; a differential control valve connected to said flow divider downstream of said flow divider; and a gas meter connected to said differential control valve downstream of said differential control valve.

24. A measuring device according to claim 23 wherein a volume converter is connected to said gas meter; a prestressing device is connected to said gas meter downstream of said gas meter; and a tank is connected to said flow divider upstream of said flow divider.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Referring to the drawings that form a part of this disclosure and that are schematic and not to scale:

[0017] FIG. 1 is a fluid connection diagram of the basic construction of the measuring device according to an exemplary embodiment of the invention, with reference to a practical example in the form of the dispensing of hydrogen that can be tanked up with at a hydrogen filling station;

[0018] FIG. 2 is a perspective view of the essential components of the measuring device and a dispensing device connected thereto in the form of a hydrogen tanking nozzle according to the exemplary embodiment of the invention;

[0019] FIG. 3 is a side view in section of a flow divider required as part of the measuring device according to the exemplary embodiment of the invention;

[0020] FIGS. 4a, 4b, 5a and 5b are a top view, a side view in section, a top view and a side view in section, respectively, of individual diaphragm bodies, as used for the flow divider according to FIG. 3; and

[0021] FIG. 6 is a side view in section of a mechanically working differential control valve, as is required to adjust the gas pressure in the secondary flow to the extraction pressure in the main flow according to the exemplary embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0022] Firstly, the basic construction of the measuring device according to an exemplary embodiment of the invention shall be explained in greater detail with reference to the connection depiction according to FIG. 1. FIG. 1 thus symbolically depicts a filling station storage 10, which is connected at the outlet side to a dispensing network 12 of a filling station that is not depicted in greater detail. A coupling point 14 is used for the connection of the measuring device to the dispensing network 12, at which coupling point a tank nipple 16 can be connected in a detachable manner to a filling nipple 18 of the dispensing network 12. When the two nipples 16, 18 are correspondingly coupled via the coupling point 14, a fluid-conducting or medium-conducting passage is created from the filling station storage 10 to a flow divider 20.

[0023] Using individual diaphragms 22, 24, the flow divider 20 divides the gas flow flowing towards its inlet side P0 at a specifiable flow divider ratio into a main flow P1 and a secondary flow P2. A flow divider ratio of the secondary flow P2 to the main flow P1 of 1:64 has proved to be particularly suitable. However, other division ratios are also possible here, for example 1:50 or 1:100. For the measurement in the secondary flow P2, only a partial amount that is significantly smaller compared with the main flow P1 is important to e branched off by the flow divider 20. On the dispensing side of the flow divider 20, a dispensing device 26 is connected to the line with the main flow P1, which dispensing device is in the form of a hydrogen dispensing delivery nozzle here.

[0024] The line carrying the secondary flow P2 is connected to the inlet of a differential control valve 28, so that the secondary flow P2 is conveyed between the diaphragms 24 of the flow divider 20 and the inlet or inflow side of the differential control valve 28. On the two opposite control sides of the valve 28, the control pressure is applied to the secondary flow P2 and the gas pressure is applied to the main flow P1, which, tapped before the dispensing device 26 in the main flow P1, is conducted via a branching point 30 to the one control side of the control valve 28. The control valve 28 additionally experiences a holding shut in its unactuated locking position depicted in FIG. 1 by a suction operation on the dispensing side of the control valve 28, which is thus formed by the measuring line P3. This holding shut is symbolically depicted in FIG. 1 with regards to the control valve 28 by the pressure spring 32 acting as an energy storage. When the pressure in the main flow P1 is equal to the pressure in the secondary flow P2, the valve is closed.

[0025] Measuring line P3 coming from the control valve 28 is connected to the outlet side thereof, and the measuring line P3 continues onwards to a gas meter 36, which is in particular formed as a low pressure gas meter. A heat exchanger 34 is connected between the control valve 28 and the gas meter 36, which heat exchanger, formed as a spiral, brings the gas coming from the valve 28 to room temperature RT or ambient temperature, and at the same time expands it, for example brings the gas from 300 bar to 0.5 to 16 bar (cf. the relevant details in FIG. 1). A bursting disk 40 can in turn be arranged between the outlet side of the heat exchanger 34 and the inlet side of the gas meter 36. The bursting disk 40 forms an overpressure protection so that it will burst in the event of an incident, e.g., at too high a pressure, in order to thus protect the sensitive gas meter 36 against overpressure or pressure pulsations. A prestressing device 42 is connected on the outlet side of the gas meter 36, which prestressing device is formed in particular in the form of a spring-loaded check valve with an opening pressure of 0.5 to 1 bar. The direction of closing of the check valve is in the direction of the outlet side of the gas meter 36 and cooperates with same. In addition, an electronic volume converter 38 is connected to the gas meter 36.

[0026] The gas allowed through by the prestressing device 42 in the opened state can then optionally either be discharged into the environment via a chimney 44 or returned to the filling station storage 10 by a combined compressor/storage device 46. For this purpose, the device 46 has a collection tank 48 and a readings recorder 50, which actuates an electric motor unit 52 in the case of a correspondingly filled tank 48. The motor unit 52 drives a compressor 54, which extracts the gas from the collection tank 48 and returns it to the filling station storage means 10.

[0027] With regards to the dimensioning of the overall system in accordance with the connection diagram depiction according to FIG. 1, the following information is noted. In the filling station storage 10, hydrogen gas is frequently stored at −40° C. and 875 bar working pressure. The hydrogen gas is pure, highly-pressurized hydrogen. Both in the dispensing network 12 and on the main flow side P1 line cross sections DN04 are used with a compressive strength of PN875. This results in a gas amount of 2403 Nm3/h (standard cubic meters per hour) at a hypothetical flow rate of 60 grams/second. The proportional flow divider ratio of 1:64 in the flow divider 20 results in a flow rate of approx. 1 gram/second in the secondary flow P2, which corresponds to 11.2 liters/second or 40 Nm3/h. A maximum pressure difference Δp of approximately 5 bar is then obtained between the inlet side P0 and the outlet side of the flow divider 20 both on the main flow side P1 and in the secondary flow P2. The line cross sections DN04, DN2.1 and DN25 used for the individual line sections are also depicted FIG. 1.

[0028] Instead of another merging of the gas flow divided by f the flow divider 20, the pressure at the outlet of the differential control valve 28, in other words, at the point of the connected measuring line P3, is maintained by this control valve 28 at exactly the same pressure as the pressure in the main flow P1 between the flow divider 20 and the dispensing device 26 in the form of the delivery nozzle. The hysteresis of the control valve 28 should preferably be less than 0.6 bar. The gas, which is dispensed by the differential control valve 28 and is in particular “blown off” and which is brought to ambient temperature by the heat exchanger 34, expands and is then constantly converted to standard cubic meters and added up by the gas meter 36 calibrated to a maximum of 25 Nm3/h at a dynamic pressure of 1 bar.

[0029] Line cross section DN25 having the stability PN16 are used in this area. In addition, at a mass flow of 1 gram hydrogen/second, a volume of 20.16 Nm3/h at 1 bar prestress pressure is obtained in the measuring branch of the measuring line P3, which passes through the gas meter 36. The thus measured gas, which is stored by the check valve of the prestressing device 42 preferably with this 1 bar of opening pressure, is then, as already stated, either discharged into the environment via the chimney 44 or conveyed to the compressor/storage device 46 for the purpose of feeding back to the filling station storage means 10. The electronic volume converter 38 allows the pressure and temperature fluctuations inside the gas meter 36 to be determined. Those fluctuations then correspondingly serve to determine the gas volume at room temperature and normal air pressure that value is required by the user for exact monetary accounting for the hydrogen gas amount dispensed via the delivery nozzle of the dispensing device 26.

[0030] The principle of flow divider measurement illustrated by way of an example in FIG. 1 can of course also be used for larger gas amounts and other line nominal diameters. The respective pressures or pressure ranges and the temperatures to be anticipated including the line cross sections and pressure parameters are correspondingly specified in FIG. 1, wherein the abbreviation RT stands for room temperature. FIG. 2 shows the corresponding components of the connection depiction according to FIG. 1 with their specific structural design, wherein the delivery nozzle of the dispensing device 26 is connected to the flow divider 20 preferably via a flexible line of the main flow P1.

[0031] FIG. 3 shows, in the manner of a longitudinal sectional depiction, the flow divider 20 according to FIG. 1. Extending between two end plates 56, 58 is a receiving body 60 having two through-holes, in which individual diaphragm bodies 62, 64 are received to form the overall diaphragms 22 or 24 of the flow divider 20. To obtain a pressure value drop Δp of 5 bar inside the flow divider 20 from the inlet side P0 to the outlet side both for the main flow P1 and for the secondary flow P2, twenty diaphragm bodies 62 or 64 are arranged in each receiving channel of the central receiving body 60.

[0032] To obtain the described division between the secondary flow P2 and the main flow P1 of 1:64, the diaphragm body 62 illustrated by way of an example in FIGS. 4a, 4b has a plurality of individual diaphragm bores 66, wherein, with respect to the desired division ratio, 64 diaphragm bores 66 are evidently used. In accordance with the depiction according to FIGS. 5a and 5b, only one in particular centrally arranged diaphragm bore 66 is logically then used for the respective diaphragm body 64, in order to obtain an individual redispensable gas portion in the secondary flow P2.

[0033] As FIG. 3 furthermore shows, the top end plate 56 has connection options for the main flow P1 and the secondary flow P2 and the bottom end plate 58 has an inlet P0 for connection to the filling station dispensing network 12. All of the diaphragm bodies 62, 64 are sealed and held in position at the outer circumference by of ring seals, which can be received in groove-shaped recesses 68 (cf. the sectional depictions along the line A-A according to FIGS. 4b and 5b), which situation is not depicted in greater detail. Furthermore, the channels for receiving the respective diaphragm bodies 62, 64 are sealed at the respective end of the central receiving body 60 by conventional ring seals, which are not depicted in greater detail, relative to the top and bottom end plate 56, 58, as depicted in FIG. 3. Each diaphragm body 62, 64 of a category, in other words, provided in each case with 64 bores or only one diaphragm bore 66, is constructed as inexpensively producible identical parts and is formed temperature-resistant and high pressure-tight.

[0034] The longitudinal sectional depiction according to FIG. 6 relates to a schematic depiction of the differential control valve 28 used in FIG. 1 and shows the connection points for the main flow P1, the secondary flow P2 and for the measuring line P3. In view of the high pressures and the low temperatures, the differential control valve 28 is formed screwed in a flange construction in a particularly robust manner. Enclosed between a top flange part 70 and a bottom flange part 72 is a hollow chamber 74 with a mobile valve part 76 of the valve plate kind.

[0035] The valve plate 76 is surrounded at the edge sides by a bellows membrane 78, which extends in a planar manner, which engages at the edges between the two flange parts 70, 72 and which is fixed there in an appropriately sealed manner. The valve plate 76 is able to realize a small stroke inside the hollow chamber 74. In the raised position, valve plate 76 releases a valve seat 80 of PEEK steel, which has a fluid-conducting connection to the measuring line P3. During operation of the differential control valve 28, in view of the rapid and constant infeed of the pressure in the secondary flow P2 compared with the main flow P1, the valve plate 76 will, depending on the extraction situation at the delivery nozzle 26, start to oscillate. If appropriate, with a frequency of 100 Hz for example, in other words, 100 oscillations per second, valve plate 26 releases or shuts off the fluid flow 77 between the secondary flow P2 and the measuring line P3 via the valve seat 80. In this way, a gas amount in the secondary flow P2 with the same pressure as in the main flow P1 is conveyed “in a quantized form” to the measuring line P3 for subsequent measured value processing by the gas meter 36 and the volume converter 38.

[0036] The holding shut of the control valve 28 in its unactuated neutral position, symbolically depicted in FIG. 1 by the pressure spring 32, occurs by a partial suction at the valve seat 80 by the measuring line P3. An effect of the sort is known from bathtub plugs during plughole closing or opening by those plugs, which are then frequently briefly sucked up by the plughole opening. Very advantageously, the components of the differential control valve 28 are all designed as mechanical components, in other words, without electronics, which plays a significant role in view of the high flammability of the hydrogen.

[0037] The low pressure gas meter 36 in FIG. 2 is formed as a rotary piston gas meter. According to the latest data sheet issued by the company Itron, from whom this gas meter can be purchased under the trademark name Delta®, permits precise gas amount determination, even in the case of intermittent operation, and which, in particular in the case of a low pressure application, can determine gas amounts in a highly precise manner on the basis of the volume or the amount. A volume converter 38, which can also be purchased from the company Itron, which is available under the trade name CORUS PTZ, also permits, according to the data sheet specification, an integrated data storage acquisition and analysis. That CORUS converter 38 converts the gas amount measured by the gas meter 36 during operation into the corresponding volume under standard conditions. In its microprocessor determines the compressibility factor and also the conversion factor and the reevaluated gas amount from the operating values for amount, pressure and temperature. In this way, determining in a precise commercial manner at the dispensing side by the delivery nozzle as a component of the dispensing device 26 the amount of gas dispensed at the filling station which is relevant for determining the purchase price is possible. The method according to the invention and the associated measuring device thus for the first time allow a practical dispensing at filling stations of hydrogen for end users to be reliably undertaken, with the end users then only having to pay for the gas amount that they have actually filled their vehicle with.

[0038] While one embodiment has been chosen to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined in the claims.