GB2579403A

GB2579403A - Pressure sensing

Info

Publication number: GB2579403A
Application number: GB1819561.0A
Authority: GB
Inventors: Anderson Stewart; Philby Rhoy; Peter Duffy Liam; Powell Gareth
Original assignee: Haskel Europe Ltd
Current assignee: Haskel Europe Ltd
Priority date: 2018-11-30
Filing date: 2018-11-30
Publication date: 2020-06-24
Anticipated expiration: 2038-11-30
Also published as: GB2579403B; GB201819561D0

Abstract

A station for replenishing a gas vessel (10, figure 1) of a recipient unit, (8, figure 1) such as a refuelling station for a hydrogen-powered vehicle, comprising a source of gas 22, a filling line 23, terminating in a coupling 24, a controllable valve 25, a check valve 27, and a pressure sensor 26 located between the controllable valve and the check valve. The controllable valve is controlled by a controller 28. Also disclosed is a method of using such a station comprising i) momentarily opening the controllable valve, to increase filling line pressure ii) closing the controllable valve whilst the check valve is open, to allow the filling line pressure to equilibrate with the gas vessel iii) reading the pressure sensed. The controllable valve may be a pressure regulating valve

Description

PRESSURE SENSING

This invention relates to sensing the pressure in a gas receiver, for example when dispensing fuel gas to vehicles.

A typical gas-fuelled vehicle has a reservoir or tank for holding fuel gas in a pressurised state. When the vehicle comes to be refuelled, gas under pressure is introduced into the vehicle's tank. In order to manage the refuelling process it is useful to estimate the pressure of gas in the tank at the start of the process. Then the filling procedure can be controlled in dependence on the estimated pressure, for example to meet a desired filling time or to prevent the contents of the tank exceeding a certain temperature.

The vehicle may have an onboard sensor for sensing the pressure in the tank. The output of the onboard sensor may be transmitted to a refuelling station to permit the refuelling station to control its filling procedure. However, this relies on the vehicle and the fuelling station supporting a common communication protocol. In some situations this might not be feasible. It would then be desirable for the filling station to remotely sense the pressure in the tank.

Figure 1 is a schematic view of one design of refuelling station for filling the fuel tanks of gas-fuelled vehicles. The station comprises a reservoir 1 of pressurised fuel gas and a filling line 2 by which the reservoir can be coupled to a vehicle in order to refill the vehicle's fuel tank. Set in the line 2 are a control valve 3 which can be actuated by a controller 4 to permit gas to flow to the vehicle, a pressure sensor 5 and a check valve 6. The purpose of the check valve is to resist backflow of gas from the vehicle into the reservoir 1. Backflowing gas might contaminate the contents of the reservoir. A nozzle 7 is provided on the distal end of the line 2 for coupling the line to a vehicle 8. The nozzle can be coupled to a filling port 9 of the vehicle. The filling port communicates with the vehicle's fuel tank 10. In a system of this type, when the nozzle 7 is first coupled to the vehicle the pressure sensor 5 cannot straightforwardly be used to sense the initial pressure in the vehicle's tank because sensor 5 is isolated from the vehicle's tank by the check valve 6. One solution to this might be to locate an additional pressure sensor between the nozzle 7 and the check valve 6. However, this would increase cost; and the vehicle might be fitted with its own check valve 11, which would mean that a pressure sensor located downstream of the check valve 6 could still not straightforwardly sense the base pressure of the vehicle's tank.

There is a need for a gas filling system which can remotely sense the pressure of a tank to which it is connected notwithstanding the presence of one or more check valves.

According to one aspect there is provided a station for replenishing a gas vessel of a recipient unit, the station comprising: a source of gas at elevated pressure; a filling line coupled to the source of gas and terminating in a coupling; a controllable valve located in the filling line; a check valve located in the filling line between the controllable valve and the coupling, the check valve being configured to resist the flow of gas in a direction from the coupling towards the source of gas; a pressure sensor communicating with the filling line between the controllable valve and the check valve; and a controller for controlling the controllable valve, the controller being configured to, when a recipient unit having a gas vessel is coupled to the coupling, perform the following steps in order to estimate an initial pressure in the gas vessel of the recipient unit: (i) momentarily opening the controllable valve so as to increase the pressure in the filling line and thereby cause the check valve to open; (ii) closing the controllable valve whilst the check valve is open so as to permit the pressure in the filling line between the controllable valve and the check valve to equilibrate with the pressure in the gas vessel of the recipient unit; and (iii) reading the pressure sensed by the pressure sensor.

The controllable valve may be a pressure regulating valve and the step of opening the controllable valve may comprise causing the pressure regulating valve to operate so as to adjust the pressure in the filling line towards a series of target pressures, the target pressures increasing over time.

The controllable valve may be a pressure regulating valve and the step of closing the controllable valve may comprise causing the pressure regulating valve to operate so as to adjust the pressure in the filling line towards a series of target pressures, the target pressures decreasing over time.

The controllable valve may be open for a time less than two seconds during the said steps.

The check valve may be a one-way valve configured to resist flow of gas through the filling line in a direction towards the source of gas.

The station may further comprise a control unit for controlling the station to perform a replenishment operation in order to replenish the gas vessel of the recipient unit, the control unit being configured to determine at least one of (i) an amount of gas to be passed to the recipient unit in the replenishment operation and (ii) a flow rate of gas to the recipient unit in the replenishment operation in dependence on the said pressure sensed by the pressure sensor.

The gas may be a combustible gas such as hydrogen.

The coupling may be releasably couplable to the recipient unit.

The station may be a vehicle refuelling station.

The present invention also provides a method for replenishing a gas vessel of a recipient unit by means of a station, the station comprising: a source of gas at elevated pressure; a filling line coupled to the source of gas and terminating in a coupling; a controllable valve located in the filling line; a check valve located in the filling line between the controllable valve and the coupling, the check valve being configured to resist the flow of gas in a direction from the coupling towards the source of gas; and a pressure sensor communicating with the filling line between the controllable valve and the check valve; the method comprising, when the recipient unit is coupled to the coupling, performing the following steps in order to estimate an initial pressure in the gas vessel of the recipient unit: (i) momentarily opening the controllable valve so as to increase the pressure in the filling line and thereby cause the check valve to open; (ii) closing the controllable valve whilst the check valve is open so as to permit the pressure in the filling line between the controllable valve and the check valve to equilibrate with the pressure in the gas vessel of the recipient unit; and (iii) reading the pressure sensed by the pressure sensor.

The present invention will now be described by way of example with reference to the accompanying drawings.

In the drawings: Figure 1 shows a first design of refuelling system for refuelling a vehicle.

Figure 2 shows schematically a second design of refuelling system for refuelling a vehicle.

Figure 3 shows a vehicle capable of being refuelled by the system of figure 2.

Figure 2 shows at 20 a refuelling station for refuelling a gas-fuelled vehicle. In this instance the gas is hydrogen, but it could be another combustible gas such as propane. The system could be used for charging units other than vehicles with gas. For example, it could be used for recharging domestic or industrial fuel tanks. The system could be used for charging vessels with gases other than fuel gas: for example with non-combustible gases such as air or nitrogen.

The station 20 comprises a reservoir 21 of gas. In this instance that gas is hydrogen. The reservoir may be a single container (e.g. a tank or cylinder) or it may be composed of multiple containers 22 coupled together. The reservoir may be topped up from time to time from other storage units, or it may be topped up from a local gas generator. A gas generator may synthesise or concentrate gas from another resource: for instance it may extract hydrogen from water by electrolysis. In the system of figure 2 the gas is held in the reservoir 21 at a pressure greater than the expected initial pressure of a vessel that is to be replenished. This means that gas can flow to the vessel under the action of the pressure pre-existing in the reservoir. The reservoir may be pressurised by a pump. In other arrangements, a pump may be provided to pressurise gas flowing from the reservoir 21 to the vessel that is to be replenished. Such a pump may be located between the reservoir 21 and check valve 27.

A filling line 23 extends from the gas reservoir 21 to a dispensing nozzle 24. The dispensing nozzle is configured to mate with a receiving orifice in the article to be provided with gas. In this case that is orifice 41 of the vehicle 40 shown in figure 3. The nozzle may, for example, be configured as set out in SAE J2600.

The proximal, or most upstream, end of the filling line 23 terminates at the gas reservoir 21. The distal, or most downstream, end of the filling line terminates at the dispensing nozzle.

Set in the filling line 23 are a controllable valve 25, a pressure sensor 26 and the check valve 27.

The controllable valve 25 is operable to open or close the filling line. When the controllable valve 25 is open, flow of gas from the gas reservoir 21 towards the nozzle 24 is permitted. When the controllable valve is closed, flow of gas from the gas reservoir 21 towards the nozzle 24 is prevented. The controllable valve is configured so as to be controlled by a control unit 28. The controllable valve is controlled by a control signal on signal line 29. Signal line 29 interconnects the control unit and the controllable valve. The control signal may be, for example, an electrical signal. In one example, the controllable valve may comprise a valve body defining a passageway for gas through the valve, and a closure element such as a needle or a moveable plug that can be moved across the passageway to adjust the flow therethrough. The closure element may be coupled to a solenoid or a motor so that it can be moved in response to the control signal. The controllable valve may be an automatic pressure regulator valve. An automatic pressure regulator valve receives a signal indicating a target pressure at an outlet of the valve, and is configured to automatically control flow through the valve with the aim of achieving the target pressure at the valve's outlet.

Figure 2 depicts the valve 25 as an automatic pressure regulator valve. The valve comprises a closure mechanism 30, a pressure sensor 31 located to measure pressure at the outlet of the valve and a valve controller 32. The valve controller 32 receives on line 29 a signal indicating a target pressure at the outlet of the valve. It compares that pressure with the pressure indicated by the pressure sensor 31. If the target pressure is greater than the indicated pressure then the valve controller causes the closure mechanism to open or open further, which allows flow from the inlet of the valve to the outlet to increase. If the target pressure is less than the indicated pressure then the valve controller causes the closure mechanism to close or close further, which reduces flow from the inlet of the valve to the outlet. In this way, the valve controller automatically adjusts flow through the valve with the aim of achieving the target pressure at the outlet. In an alternative embodiment the controllable valve could be of a simpler design.

The pressure sensor 26 is located between the controllable valve 25 and the check valve 27. The pressure sensor 26 senses pressure in the line 23. It signals the sensed pressure to the control unit 28 over signal line 33. Where the controllable valve incorporates a pressure sensor at its outlet, as in the controllable valve of figure 2, that sensor could serve the function of sensor 26.

The check valve 27 is located downstream of the pressure sensor 26. The check valve is located between the pressure sensor 26 and the outlet nozzle 24. The check valve is configured to resist backflow of gas (i.e. in an upstream direction) in line 23. The check valve may be of any suitable design. In one design, the check valve may comprise a passageway in which a valve seat is defined, and a moveable valve element which is biased by a spring against the valve seat to close the valve. Such a check valve may be configured so that it is closed unless the pressure immediately upstream of the check valve exceeds the pressure immediately downstream of the check valve by a threshold amount. The threshold amount may be governed by the strength of the spring. The threshold amount may be small in comparison to the absolute values of the pressures used in the system. The check valve permits flow through itself when the pressure on the upstream side of the valve exceeds the pressure on the downstream side of the valve, and resists flow through itself otherwise.

The controller 28 comprises a processor 34 and a memory 35. The memory 35 stores in a non-transient manner program code that is executable by the processor to implement the functions described of the controller herein.

Figure 3 illustrates the nozzle 24 of the filling station 20 coupled to vehicle 40 for replenishing fuel gas into the vehicle. The vehicle comprises external orifice 41 configured to couple with the nozzle 24 and a fuel tank 42 coupled to the orifice 41 by a delivery pipe 43. Set in the delivery pipe 43 is a check valve 44 which resists flow of gas out of the fuel tank. The check valve 44 is closed unless the pressure on the inlet side of the check valve (i.e. the side facing the orifice 41) exceeds the pressure on the outlet side of the check valve (i.e. the side facing the tank 42) by a threshold amount. That predetermined amount may be relatively small in comparison to the absolute values of the pressures used in the system. The orifice 41 may also comprise a valve which closes the inlet of the delivery pipe 43 unless the nozzle is coupled to the orifice. The vehicle has an engine 45 configured to drive the vehicle to move through combustion of gas from the tank 42. The orifice 41 may, for example, be configured as set out in SAE J2799.

In a simple mode of operation, the nozzle 24 is coupled to a receiver of gas such as vehicle 40. The receiver comprises a vessel such as a fuel tank 42 for holding gas. The controller 28 causes the controllable valve 25 to open. If the pressure in the receiving vessel is less than the pressure in the reservoir 21 of the filling station 20, the check valve 27 will open (as will any check valve such as 44 in the receiver) and gas will flow from the reservoir 21, through the filling line 23 and into the delivery pipe 43. When filling is complete the controller 28 closes the controllable valve 25. A switch may be provided on the nozzle 24 to sense when it is properly mated with a receiving orifice 41. The controller may be configured to open valve 25 to initiate flow of gas in response to the switch detecting that the nozzle is properly mated. Alternatively, a user-actuable switch 36 may be provided to command the controller to initiate the flow of gas.

In practice, it may be desirable to adapt the process of dispensing the gas in dependence on the initial state of the receiver. For example, it may be desirable to dispense gas such that the receiver is replenished to a desired pressure in a predetermined time, or to avoid the temperature of the gas with which the receiver is being replenished exceeding a predetermined upper or lower bound. In order to do this it may be desirable to know the initial pressure in the gas-receiving vessel of the receiver. To determine this the system may operate in a more complex mode of operation which will be described below.

The valve 25 is normally closed. When the nozzle 24 is initially coupled to the receiver, and before replenishment of the receiver begins, the controller 28 causes the system to undergo a pressure sensing operation. The pressure sensing operation is conducted as follows. The controller 28 causes the controllable valve 25 to open momentarily and then to shut. The gas upstream of the controllable valve is at a relatively high pressure, i.e. it is at a higher pressure than that in the receiving vessel (e.g. 42). While the controllable valve is momentarily open it permits gas to flow momentarily from the reservoir 21 into the filling line 23 downstream of the controllable valve. The pressure in the filling line at the upstream side of the check valve 27 rises. The pressure in the filling line on the downstream side of the check valve 27 will typically be at atmospheric pressure (if the recipient has a check valve 44) or at the pressure of the receiving vessel 42 (if the distal end of the filling line is already communicating with the receiving vessel). This pressure differential across the check valve 27 causes that valve to open. If the recipient has a check valve 44 then once check valve 27 is open and the conduits immediately downstream of it are pressurised there will be a pressure differential across check valve 44, which will cause check valve 44 to open in an analogous way. Once the or each check valve is open, the region of the line 23 in which the pressure sensor 27 is located is communicating with the vehicle tank 42. As a result, when the controllable valve 25 shuts, pressure in the line 23 will equilibrate with the pressure in the vehicle tank 42. As the pressure equilibrates, the pressure difference across each check valve 27, 44 will become negligible, and as a result those valves will close. This results in the region of the line 23 between the controllable valve 25 and the check valve 27 being held tight at a pressure that is substantially equilibrated with the pressure of the vehicle tank 42. The pressure measured by sensor 26 can then be read to obtain an estimate of the pressure in the vehicle's tank. That pressure can be provided to the control unit 28 over line 33. Thus, the valve 25 is controlled to impose a pressure spike on the line to the unit that is to be replenished. That spike causes momentary fluid communication of a pressure sensor in the filling station with the gas vessel of the unit that is to be replenished.

The control unit can then determine and implement a program for replenishing gas into the vehicle in dependence on the estimated pressure of the vehicle's tank 42. For example, the control unit may determine a desired flow rate of gas, which may vary over time, in dependence on one or more inputs including the estimated initial pressure of the receiving reservoir. The control unit may then implement that program so as to replenish the recipient's tank with gas. The program may be terminated when a predetermined end state is achieved. That may, for example be the dispensing of a predetermined amount of gas to the recipient, or the achievement of a predetermined pressure in the recipient's receiving vessel. Once the replenishment operation is complete, the nozzle 24 may be detached from the recipient. Then another recipient (e.g. another vehicle) may be replenished in a similar way. The control unit may determine one or both of (i) the volume of gas to be passed to the receiver in the replenishment operation and (ii) the flow rate of gas to be passed to the receiver in the replenishment operation in dependence on the estimated initial pressure in the vessel of the receiver that is to be filled.

If the controllable valve 25 is responsive only to a signal to open or close then it may be fully opened during the momentary pressurising phase, and then fully closed. In a more sophisticated embodiment, the controllable valve may be capable of being controlled so as to cause the pressure in the filling line to progressively increase during the momentary pressurising phase. This can reduce stress on the equipment. One way in which this can be done, if the controllable valve is a pressure regulator valve, is to transmit a series of signals to the valve to indicate a series of target outlet pressures which progressively increase. Optionally, the reverse may be done to end the momentary pressurising phase. Thus, the momentary pressurising phase may be implemented by a ramping up followed by a ramping down of the target pressure for the controllable valve 25.

The optimum duration of the momentary pressurising phase (i.e. the time for which the valve 25 is at least partially open during the momentary pressurising step) may depend on the response times of the valves and the dimensions of the pipework. However, for a typical vehicle fuelling installation it has been found that a duration in the region of 1 second is suitable. The duration may, for example be longer than any of 0.2, 0.5 or 0.8 seconds. The duration may, for example, be less than 8, 5 or 2 seconds. The duration may be between 0.8 and 1.5 seconds. During the momentary pressurising phase gas flows from the reservoir 21 towards the vessel 42. This will to some extent increase the pressure in the vessel 42 from its initial value. Preferably the duration of the momentary pressurising phase is such as to cause the pressure in the receiving vessel to rise by less than 2, 5, 10 or 20 bar. Limiting the increase in pressure of the receiving vessel can reduce constraints on the performance of the momentary pressurising phase because it is unlikely to result in significant over-pressurisation or overheating of the receiving vessel.

In the example described above, the source reservoir 21 comprises one or more tanks storing pre-pressurised gas. Conveniently the gas source is at a higher pressure than the receiving vessel. For example, it may be at a pressure at least 100 bar above the initial pressure of the receiving vessel. The reservoir 21 may store gas at a pressure in the range from 100 to 500 bar, conveniently more than 400 bar. The initial pressure in the receiving vessel may be in the range from 40 to 400 bar, conveniently less than 200 bar. Other pressures are also suitable. In an alternative embodiment the gas source may be at the same or a lower pressure than the receiving reservoir. Then, as discussed above, gas coming from the gas source may be pressurised by a pump before passing to the check valve 27.

The check valve may be a one-way valve.

In figure 2 the pressure sensor 26 is shown located in the filling line on the flow path between the controllable valve 25 and the check valve 27. It could alternatively be located on a branch from that flow path.

The principles described above may be employed for replenishing reservoirs other than fuel reservoirs, and with gases other than fuel gases. The gas may be a fuel gas. The gas may be a combustible gas. The gas may be an inert gas. The gas may be hydrogen. The gas may be air.

The gas may be refrigerated in the reservoir 21, for example to below 0°C.

In one example, the station 20 may be a filling station for hydrogen-powered vehicles.

A practical replenishment station may have other pipes, valves sensors and other fittings than those shown in figure 2.

The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention.

Claims

CLAIMS1. A station for replenishing a gas vessel of a recipient unit, the station comprising: a source of gas at elevated pressure; a filling line coupled to the source of gas and terminating in a coupling; a controllable valve located in the filling line; a check valve located in the filling line between the controllable valve and the coupling, the check valve being configured to resist the flow of gas in a direction from the coupling towards the source of gas; a pressure sensor communicating with the filling line between the controllable valve and the check valve; and a controller for controlling the controllable valve, the controller being configured to, when a recipient unit having a gas vessel is coupled to the coupling, perform the following steps in order to estimate an initial pressure in the gas vessel of the recipient unit: (i) momentarily opening the controllable valve so as to increase the pressure in the filling line and thereby cause the check valve to open; (ii) closing the controllable valve whilst the check valve is open so as to permit the pressure in the filling line between the controllable valve and the check valve to equilibrate with the pressure in the gas vessel of the recipient unit; and (Hi) reading the pressure sensed by the pressure sensor.
2. A station as claimed in claim 1, wherein the controllable valve is a pressure regulating valve and the step of opening the controllable valve comprises causing the pressure regulating valve to operate so as to adjust the pressure in the filling line towards a series of target pressures, the target pressures increasing over time.
3. A station as claimed in claim 1 or 2, wherein the controllable valve is a pressure regulating valve and the step of closing the controllable valve comprises causing the pressure regulating valve to operate so as to adjust the pressure in the filling line towards a series of target pressures, the target pressures decreasing over time.
4. A station as claimed in any preceding claim, wherein the controllable valve is open for a time less than two seconds during the said steps.
5. A station as claimed in any preceding claim, wherein the check valve is a one-way valve configured to resist flow of gas through the filling line in a direction towards the source of gas.
6. A station as claimed in any preceding claim further comprising a control unit for controlling the station to perform a replenishment operation in order to replenish the gas vessel of the recipient unit, the control unit being configured to determine at least one of (i) an amount of gas to be passed to the recipient unit in the replenishment operation and (ii) a flow rate of gas to the recipient unit in the replenishment operation in dependence on the said pressure sensed by the pressure sensor.
7. A station as claimed in any preceding claim, wherein the gas is a combustible gas.
8. A station as claimed in any preceding claim, wherein the gas is hydrogen.
9. A station as claimed in any preceding claim, wherein the coupling is releasably couplable to the recipient unit.
10. A station as claimed in any preceding claim, wherein the station is a vehicle refuelling station.
11. A method for replenishing a gas vessel of a recipient unit by means of a station, the station comprising: a source of gas at elevated pressure; a filling line coupled to the source of gas and terminating in a coupling; a controllable valve located in the filling line; a check valve located in the filling line between the controllable valve and the coupling, the check valve being configured to resist the flow of gas in a direction from the coupling towards the source of gas; and a pressure sensor communicating with the filling line between the controllable valve and the check valve; the method comprising, when the recipient unit is coupled to the coupling, performing the following steps in order to estimate an initial pressure in the gas vessel of the recipient unit: (i) momentarily opening the controllable valve so as to increase the pressure in the filling line and thereby cause the check valve to open; (ii) closing the controllable valve whilst the check valve is open so as to permit the pressure in the filling line between the controllable valve and the check valve to equilibrate with the pressure in the gas vessel of the recipient unit; and (iii) reading the pressure sensed by the pressure sensor.