A method for for a pressurized gas fuel system, an arrangement for a pressurized gas fuel system, and a vehicle comprising the arrangement

Abstract

A method (200) for a pressurized gas fuel system (130) of a vehicle (100) is presented. The pressurized gas fuel system (130) comprises a filling conduit (131), at least one gas fuel tank (132) connected to the filling conduit (131), and a gas fuel conduit (133) arranged from the at least one fuel tank (132) to an engine (101). The method (200) comprises: - determining (210) a pressure Pdet(Tdet) and a corresponding temperature Tdet of the gas fuel (135) in the pressurized gas system (130); - providing (220) an error indication (E) if the determined pressure Pdet(Tdet) is higher than a constant density pressure PD(Tdet) for the gas fuel (135) at the determined temperature Tdet; Pdet(Tdet) > PD(Tdet); wherein - the constant density pressure PD(T) is a function of a temperature T of the gas fuel (135) in the pressurized gas system (130), defines a constant density for the gas fuel (135), and comprises a predefined normal working pressure PNWP(Tref) for the gas fuel (135) at a reference temperature Tref.

Description

[0001] A METHOD FOR FOR A PRESSURIZED GAS FUEL SYSTEM, AN ARRANGEMENT FOR A PRESSURIZED GAS FUEL SYSTEM, AND A VEHICLE COMPRISING THE ARRANGEMENT

[0002] Technical field

[0003] The present invention relates to robustness and safety of pressurized gas fuel systems, and more specifically to a method for a pressurized gas fuel system, to an arrangement for a pressurized gas fuel system, and to a vehicle comprising the control arrangement.

[0004] Background

[0005] The following background description constitutes a description of the background to the present invention, which does not, however, necessarily have to constitute prior art.

[0006] Gas fuel driven vehicles, such as vehicles driven by fuel being a compressed natural gas (CNG) or hydrogen gas (H₂), operate in a similar way as vehicles comprising a spark ignited internal combustion engine driven by e.g. gasoline or ethanol, or in a similar way as vehicles comprising a diesel cycle combustion engine. The compressed gas is stored in one or more gas tanks, and the pressurized gas fuel system transfers the pressurized gas from the one or more gas tanks to the engine through its gas lines. A pressure regulator then reduces the pressure to a level compatible with the engine fuel injection system. Finally, the gas fuel is introduced into the intake manifold or combustion chamber of the engine, where it is mixed with air, and is then compressed and ignited by a spark plug.

[0007] In order to provide safety for the pressurized gas fuel systems, the allowed gas pressure in such pressurized gas fuel systems is regulated in for example the United Nations economic commission for Europe regulation no. R.110 (UN ECE R110). According to the regulation, a normal working pressure (NWP) of 200 bar at 15 °C is defined for compressed natural gas. Thus, a normal working density for the gas fuel which comprises the normal working pressure of 200 bar at 15 °C is hereby defined. Also, a maximum allowed working pressure (MAWP) of 260 bar at any temperature is defined in the regulation. The pressure of the gas fuel in the vehicles is conventionally ensured by the tank stations being configured not to supply a too high density of gas fuel, i.e. by the tank stations not supplying a higher density than the normal working density defined for the gas fuel. The tank station is therefore programmed to ensure a correct gas fuel pressure being fuelled by using a temperature compensation control method, such that the pressure of the gas fuel being fuelled into the vehicle at the current temperature at the tank station is low enough to not exceed the normal working density for other possible temperatures experienced by the vehicle. The temperature compensation control method used by the tank stations is meant to ensure that unsafe gas fuel pressures should never occur by the possible temperature swings experienced when the vehicle is parked and / or driven around.

[0008] More in detail for compressed natural gas fuel, the temperature compensation control method is designed such that if the temperature would change to 15 °C, the gas fuel pressure in the vehicle should be 200 bar or less. Thus, if it is cold when during filling of the tank, e.g. colder than 15 °C, a lower tank pressure than 200 bar should be used by the tank station, since the pressure will increase with increasing temperatures. Conversely, if it is warm when fuelling, e.g. warmer than 15 °C, a higher fuelling pressure than 200 bar may be used by the tank station, since the pressure would drop to or below 200 bar if the temperature would drop to 15 °C. A maximal allowed working pressure may also be defined for the temperature compensation control method, such as for example 260 bar at a maximum temperature of for example 57 °C. However, the tank stations are often configured to limit the pressure to a slightly lower pressure, such as for example 250 bar, and at a lower maximum temperature, in order to ensure that the maximal allowed working pressure of 260 bar is never exceeded.

[0009] Most conventional pressurized gas fuel systems are designed to ensure that the gas fuel tanks do not explode during a fire. There are two common gas fuel tank types, steel tanks commonly used for trucks, and composite tanks often used for busses. The gas fuel tanks often comprise some kind of safety devices designed to ensure that gas fuel is released prior to a tank rupture. Tank ruptures may occur due to overpressure, high temperatures and / or weakened tanks. For example, composite tanks and / or steel tanks may rupture due to heat and / or material properties although the pressure is not very high, for example during a fire event. One such safety device is a pressure relief device (PRD or P-PRD), in which a thin disc bursts at high pressure and releases the gas fuel into the atmosphere. The pressure relief device may for example activate at 340 bar ±10% for compressed natural gas. Another such safety device is a temperature activated pressure relief valve (TPRD), which may for example be designed to activate at 110±10 °C. These safety devices are designed to protect the vehicle against fires. However, the safety devices components thus break themselves when being activated, since either a thin metal disc or a glass bulb inside of them is broken at the activation.

[0010] Brief description of the invention

[0011] If the pressure in the pressurized gas fuel system exceeds the maximal allowed working pressure, for example 260 bar for compressed natural gas, there is conventionally no simple way of knowing whether it is safe or not to continue using the pressurized gas fuel system after that. A supplier of the pressurized gas fuel system could possibly after examination and safety checking of the system determine if the pressurized gas fuel system is safe to use, but such a process would take a significant time and would probably have to be aligned with authorities, where additionally the legal interpretation of the legislation is unclear. The vehicle owner therefore most probably has a costly vehicle off road situation, and would probably find it easier and more economically attractive to buy spare parts to the pressurized gas fuel system instead of performing a time-consuming safety check.

[0012] Further, there is conventionally no reliable way of protecting the vehicle against a tank station delivering gas fuel at a pressure being too high. All the intelligence for preventing too high gas fuel pressures is conventionally at the tank station side, and the vehicle is commonly required to be turned off, i.e. the ignition has to be turned off, during fuelling.

[0013] Historically, there has been several cases of pressure relief device being activated due of too high pressures in the pressurized gas fuel system because of a failing or inaccurate temperature compensation control in a tank station. The temperature compensation control in these tank stations has in these cases not worked as defined in the regulations, such that the gas fuel has been delivered at too high densities, i.e. at densities above the normal working density, to the vehicles when fuelling at the tank station.

[0014] In some cases, the pressure of the supplied gas fuel has not been above the maximal allowed working pressure, i.e. has not exceeded 260 bar or even 250 bar for compressed natural gas, at the point in time for the fuelling. However, due to later temperature increases experienced by the vehicle, the resulting pressure of the gas fuel has become significantly higher than the maximal allowed working pressure.

[0015] For example, the vehicle may have been fuelled at low temperature, such as for example -30°C, with a gas fuel density exceeding the normal working density. After fuelling the vehicle, the weather may have changed, resulting in significantly increased temperatures, or the vehicle may have been taken indoors, such as into a washing facility, a workshop, a garage or a painting facility, resulting in an abrupt temperature increase. Such temperature increases may then lead to increasing gas fuel pressures exceeding the maximal allowed working pressure. Pressure relief devices may then in some instances become activated due to the high pressure, and gas fuel may be released into the atmosphere, causing a considerable risk for fires and / or explosions damaging the vehicle and also adjacent vehicles.

[0016] It is therefore an objective of the present invention to provide a method for a pressurized gas fuel system such that these problems are at least partly solved.

[0017] According to a first aspect of the present invention, this objective is achieved through the above-mentioned method for a pressurized gas fuel system of a vehicle. The pressurized gas fuel system comprises a filling conduit, at least one gas fuel tank connected to the filling conduit, and a gas fuel conduit arranged from the at least one fuel tank to an engine.

[0018] The method comprises:

[0019] - determining a pressure Pdet(Tdet) and a corresponding temperature Tdet of the gas fuel in the pressurized gas system;

[0020] - providing an error indication if the determined pressure Pdet(Tdet) is higher than a constant density pressure Po(Tdet) for the gas fuel at the determined temperature Tdet;

[0021] Pdet(Tdet) > Po(Tdet); wherein - the constant density pressure PD(T) is a function of a temperature T of the gas fuel in the pressurized gas system, defines a constant density for the gas fuel, and comprises a predefined normal working pressure PNWP(Tref) for the gas fuel at a reference temperature Tref

[0022] Too high pressure in the pressurized gas fuel system of a vehicle may hereby be early detected, for example before any pressure relief device is activated and start releasing gas fuel. It is thus avoided that the pressure relief devices break when they are activated, and that gas fuel hereby is released, which might result in a fire and / or an explosion.

[0023] It is hereby also avoided that the pressure exceeds the maximal allowed working pressure, e.g. 260 bar. This is advantageous, since many gas fuel system components are only certified by its manufacturer for pressures below the maximal allowed working pressure, and therefore might need to be replaced, irrespective if they are damaged or not, if the pressure at least once has exceeded the the maximal allowed working pressure. Thus, by overall avoiding pressures above the maximal allowed working pressure, the risk for damages of components in the pressurized gas fuel system is considerably reduced. Also, costs for repairing the pressurized gas fuel system, and for replacing damaged components of the system, as well as unnecessarily replacing non-damaged components, are avoided. Also, the vehicle off road (VOR) time is likely reduced to zero. Further, the risk of fires related to overpressure in the pressurized gas fuel system is considerably reduced.

[0024] Also, by the presented method for a pressurized gas fuel system of a vehicle, tank stations delivering gas fuel at a too high pressures may be detected earlier. Actually, such inaccurately calibrated tank stations may be detected essentially immediately after fuelling has been completed. Inaccurately set up and / or dangerous tank stations may also be detected based on error indications collected from more than one vehicle, and statistically analysed, such that patterns related to dangerously high gas fuel pressures being delivered from tank stations may be determined. Thus, tank stations having an inaccurate and potentially dangerous set up for its gas fuel pressure regulation may quickly be taken out of operation before any accident happens. According to an embodiment, the determination of the pressure Pdet(Tdet) and the corresponding temperature Tdet of the gas fuel is performed at one point in time in the group of:

[0025] - when an ignition of the vehicle is turned on;

[0026] - during filling of the at least one fuel tank with gas fuel;

[0027] - when the at least one fuel tank has been filled with gas fuel; and

[0028] - when the vehicle is in operation.

[0029] Hereby, a problematic gas fuel pressure in the pressurized gas fuel system, and thus possibly also an inaccurate set up of a tank station, may be quickly detected. For example, a problematic gas fuel pressure may be detected essentially directly after the fuel tank has been filled with gas fuel, i.e. essentially directly after the filling of gas fuel has stopped.

[0030] According to an embodiment,

[0031] - the gas fuel is a compressed natural gas;

[0032] - the reference temperature Tref has a value in an interval of 10°C to 20°C; and - the predefined normal working pressure PNWP(Tref) has a value in an interval of 150 bar to 250 bar.

[0033] Hereby, an error indication is provided for example if the determined pressure exceeds the allowed gas pressure regulated in the United Nations economic commission for Europe regulation no. R.110 (UN ECE R110) for compressed natural gas, i.e. if the determined pressure is higher than a pressure corresponding to the constant density pressure Po(Tdet) comprising a normal working pressure of 200 bar at 15 °C for compressed natural gas. Thus, an error indication may here be provided if this regulation is not followed by a tank station.

[0034] As us understood by a skilled person, the principles of the herein described solutions are also generally applicable on other national, regional, international and / or proprietary regulations for compressed natural gas, which may have other values for the normal working pressure and related temperature associated with a suitable constant density pressure Po(Tdet). According to an embodiment, the constant density pressure PD(T1) at a first temperature T1 is equal to a maximal allowed working pressure PMAWP; PD(T1) = PMAWP.

[0035] Hereby, it may be accurately and robustly determined if the determined pressure for the gas fuel is likely to exceed the maximal allowed working pressure PMAWP at any foreseeable operation temperature for the vehicle.

[0036] According to an embodiment,

[0037] - the gas fuel is a compressed natural gas;

[0038] - the first temperature T1 has a value in an interval of 50 °C to 85 °C; and

[0039] - the maximal allowed working pressure PMAWP has a value an interval of 250 bar to 330 bar for the gas fuel being a compressed natural gas.

[0040] Hereby, it may be safely avoided to exceed the maximal allowed working pressure PMAWP with the pressurized gas fuel system, since an error indication is provided if the determined pressure Pdet(Tdet) is higher than a constant density pressure PD(Tdet) at the determined temperature Tdet. This efficiently reduces the risk for damages in the pressurized gas fuel system and / or fires.

[0041] According to an embodiment, the method further comprises:

[0042] - defining at least one additional constant density pressure PD_ad1(T), PD_ad2(T), PD_ad3(T), wherein

[0043] -- the at least one additional constant density pressure PD_ad1(T), PD_ad2(T), PD_ad3(T) is a function of the temperature T of the gas fuel in the pressurized gas system, defines a constant density for the gas fuel, and comprises at least one additional working pressure PAWP1(Tref), PAWP2(Tref), PAWP3(Tref), for the gas fuel at the reference temperature Tref, respectively; and

[0044] -- each of the at least one additional working pressure PAWP1(Tref), PAWP2(Tref), PAWP3(Tref) has a higher value than the predefined normal working pressure PNWP(Tref) at the reference temperature Tref; PAWP1(Tref) > PNWP(Tref), PAWP2(Tref) > PNWP(Tref), PAWP3(Tref) > PNWP(Tref); and

[0045] - providing one or more additional error indications (E1, E2, E3) if the determined pressure Pdet(Tdet) has a higher value than one or more of the at least one additional constant density pressure PD_ad1(Tdet), PD_ad2(Tdet), PD_ad3(Tdet) for the gas fuel at the determined temperature Tdet; Pdet(Tdet) > PD_ad1(Tdet), Pdet(Tdet) > PD_ad2(Tdet), Pdet(Tdet) > PD_ad3(Tdet); respectively.

[0046] By defining additional constant density pressure functions for the gas fuel, alternative density lines and areas are added into a pressure-temperature representation for the gas fuel. By then determining the current pressure and temperature in the pressurized gas fuel system, the problem of too high densities being delivered from the tank station may be detected earlier and with higher accuracy. Also, to provide different error indications associated with the different additional constant density pressure functions makes it possible to provide much more information about the potential problems, such that more efficient counter actions may be made. Hereby, significant losses in form of repairs and component replacements of pressurized gas fuel system, and in form of fires may be avoided. Also, the vehicle off road time is reduced, likely to zero.

[0047] According to an embodiment,

[0048] - the at least one additional constant density pressure PD_ad1(T), PD_ad2(T), PD_ad3(T) comprises a first additional constant density pressure PD_ad1(T) comprising a first additional working pressure PAWP1(Tref) for the gas fuel at the reference temperature Tref;

[0049] - the first additional working pressure PAWP1(Tref) has a higher value than the predefined normal working pressure PNWP(Tref); PAWP1(Tref) > PNWP(Tref); and

[0050] - a maximal value PD_ad1_max of the first additional constant density pressure PD_ad1(T) has a value equal to a maximal allowed working pressure PMAWP minus an offset Δ; PD_ad1_max = PMAWP − Δ.

[0051] The first additional constant density pressure Po_adi(T), never reaches the maximal allowed working pressure PMA P. Thus, the maximal value PD_ _ad1_max of the first additional constant density pressure Po_adi(T) is less than the maximal allowed working pressure PMA P; PD_ _ad1_max<PMAWP. Also, a corresponding first error indication E1 is only provided if the determined pressure Pdet(Tdet) is higher than the first additional constant density pressure Po_adi(Tdet) at the determined temperature Tdet. Therefore, it may be concluded that the determined pressure Pdet(Tdet) has not exceeded the maximal allowed working pressure PMA P if no first error indication E1 has been provided. For example, if an error indication E is provided because the determined pressure Pdet(Tdet) is higher than the constant density pressure Po(Tdet) for the gas fuel at the determined temperature Tdet, but no first error indication E1 is provided because the determined pressure Pdet(Tdet) is lower than the first additional constant density pressure Po_adi(Tdet) at the determined temperature Tdet, it may be concluded that the pressurized gas fuel system is operative and not damaged.

[0052] According to an embodiment,

[0053] - the gas fuel is a compressed natural gas; and

[0054] - the first additional working pressure PAWP1(Tref) has a value in an interval of 210 bar to 230 bar; and

[0055] - the offset Δ has a value in an interval of 5 bar to 15 bar.

[0056] Hereby, there is a safety margin between the first additional constant density pressure PD_ad1(T) and the maximal allowed working pressure PMAWP.

[0057] According to an embodiment,

[0058] - the at least one additional constant density pressure PD_ad1(T), PD_ad2(T), PD_ad3(T) comprises a second additional constant density pressure PD_ad2(T) comprising a second additional working pressure PAWP2(Tref) for the gas fuel at the reference temperature Tref;

[0059] - the second additional working pressure PAWP2(Tref) has a higher value than the first additional working pressure PAWP1(Tref); PAWP2(Tref) > PAWP1(Tref); and

[0060] - a value of the second additional constant density pressure PD_ad2(T2) at a second temperature T2 is equal to the maximal allowed working pressure PMAWP; PD_ad2(T2) = PMAWP.

[0061] Hereby, the second temperature T2 may be chosen to correspond to one or more conditions to possibly be experienced by the pressurized gas fuel system. Thus, if a corresponding second error indication E2 is provided because the determined pressure Pdet(Tdet) is higher than the second additional constant density pressure Po_ad2(Tdet) at the determined temperature Tdet, then it may be concluded that there is a risk that the gas fuel pressure will exceed the maximal allowed working pressure PMAWP if the vehicle will enter into such one or more conditions corresponding to the second temperature T2.

[0062] According to an embodiment,

[0063] - the gas fuel is a compressed natural gas;

[0064] - the second additional working pressure PAWP2(Tref) has a value in an interval of 230 bar to 250 bar; and

[0065] - the second temperature T2 has a value in an interval of 20 °C to 30 °C.

[0066] Hereby, it may be concluded that there is a risk that the gas fuel pressure will exceed the maximal allowed working pressure PMAWP if the vehicle for example will enter an indoor temperature environment, such as if the vehicle is taken into a workshop or a painting facility having a temperature above the second temperature T2. Further, if the ambient temperature surrounding the vehicle would quickly increase to exceed the second temperature T2, e.g. due to increasing temperatures at the current vehicle position and / or due to the vehicle travelling to a warmer geographical position, there is a corresponding risk that the gas fuel pressure will exceed the maximal allowed working pressure PMAWP.

[0067] According to an embodiment,

[0068] - the at least one additional constant density pressure PD_ad1(T), PD_ad2(T), PD_ad3(T) comprises a third additional constant density pressure PD_ad3(T) comprising a third additional working pressure PAWP3(Tref) for the gas fuel at the reference temperature Tref;

[0069] - the third additional working pressure PAWP3(Tref) has a higher value than the second additional working pressure PAWP2(Tref); PAWP3(Tref) > PAWP2(Tref); and

[0070] - a value of the third additional constant density pressure PD_ad3(T3) at a third temperature T3 is equal to the maximal allowed working pressure PMAWP; PD_ad3(T3) = PMAWP.

[0071] Hereby, the third temperature T3 may be chosen to correspond to one or more conditions that may possibly occur for the vehicle and the pressurized gas fuel system. Thus, if a corresponding third error indication E3 is provided because the determined pressure Pdet(Tdet) is higher than the third additional constant density pressure PD_ad3(Tdet) at the determined temperature Tdet, then it is probable that the gas fuel pressure will exceed the maximal allowed working pressure PMAWP if the vehicle will enter into such one or more conditions corresponding to the third temperature T3.

[0072] According to an embodiment,

[0073] - the third additional working pressure PAWPs(Tref) is higher than the maximal allowed working pressure PMA P; PAWP3(Tref) > PMAWP; and

[0074] - the third temperature T3 has a value in an interval of 0 °C to 10 °C.

[0075] Hereby, it may be concluded that there is a risk that the gas fuel pressure will exceed the maximal allowed working pressure PMAWP if the ambient temperature surrounding the vehicle would quickly increase to above the third temperature T3, or if the vehicle would enter into for example a washing facility having a temperature exceeding the third temperature T3, for example during winter in colder countries.

[0076] According to an embodiment,

[0077] - the gas fuel is a compressed natural gas; and

[0078] - the maximal allowed working pressure PMAWP has a value in an interval of 250 bar – 330 bar.

[0079] Thus, the presented method for a pressurized gas fuel system may be utilized for compressed natural gas fuel, such that the safety, reliability and robustness of compressed natural gas vehicles is improved.

[0080] According to an embodiment, the determination of the pressure Pdet(Tdet) is performed by utilization of at least one pressure sensor in the pressurized gas fuel system.

[0081] Hereby, at least one pressure sensor, which is present in the pressurized gas fuel system anyway, may be utilized for the pressure determination. Pressure sensors are conventionally arranged in the pressurized gas fuel system in order to be able to determine the level of fuel in the gas fuel tanks and / or system. The additional mechanical complexity is hereby minimized. According to an embodiment, the determination of the temperature Tdet is performed by utilization of one or more in the group of:

[0082] - at least one temperature sensor arranged in the pressurized gas fuel system;

[0083] - at least one ambient temperature sensor;

[0084] - temperature information provided by an offboard entity; and

[0085] - a temperature model for the pressurized gas fuel system.

[0086] There are thus various ways to determine the temperature Tdet of the gas fuel, such that a determination suitable for the current implementation may be chosen. Also, temperature sensors conventionally being arranged in the vehicle for other reasons may here, possibly in combination with a temperature model, be utilized for determining the temperature Tdet, such that the additional mechanical complexity is minimized.

[0087] According to an embodiment, the error indication comprises one or more in the group of:

[0088] - the determined pressure Pdet(Tdet);

[0089] - the determined temperature Tdet;

[0090] - at least one error code;

[0091] - a geographical position at which an ignition of the vehicle was last turned off before the determination of the pressure Pdet(Tdet) and the temperature Tdet;

[0092] - a geographical position at which the pressure Pdet(Tdet) and the temperature Tdet are determined;

[0093] - a point in time when an ignition of the vehicle was last turned off before the determination of the pressure Pdet(Tdet) and the temperature Tdet;

[0094] - a point in time when the determination of the pressure Pdet(Tdet) and the temperature Tdet is performed; and

[0095] - a point in time when the at least one fuel tank is filled with gas fuel.

[0096] Thus, depending on how the error indications are to be used by the receiver of the error indications, their content may be tailored for the receiver. For example, if the error indications are to only be used locally onboard the vehicle, it might be enough to provide the at least one error code, possibly together with a determined pressure Pdet(Tdet) and / or temperature Tdet, to a driver interface and / or another vehicle system. However, if the if the error indications are to be provided externally to an offboard entity, more information may be included in the error indications, for example geographical position information of some kind and / or temporal information of some kind, such that the determined pressure Pdet(Tdet) and / or temperature Tdet values may be correctly interpreted and analyzed by the offboard entity.

[0097] According to an embodiment, the error indication is provided to one or more in the group of:

[0098] - a driver interface of the vehicle;

[0099] - a control device configured for autonomous control of the vehicle.

[0100] - an offboard entity; and

[0101] - a workshop.

[0102] The driver of the vehicle may hereby be efficiently warned if there is a risk for a possibly dangerous upcoming situation. Alternatively, a control device of an autonomous vehicle may be alerted if there is a risk for a dangerous situation. If this is the case, the driver, or alternatively the autonomous control device, may be instructed to visit a workshop, or may in some extreme cases be requested to take drive a certain distance along a recommended route to consume fuel and thereby reduce the gas fuel pressure in the system. For example, the recommended route may comprise roads outside of the city, along which a potential fire would be less dangerous. Also, the offboard entity and / or the workshop may be informed that there is an upcoming vehicle off road situation. Further, the offboard entity, which may for example be a local technician helpdesk or some other kind of service / information centre, may utilize the provided error indications for identifying tank stations having an inaccurate or dangerous gas fuel pressure set up.

[0103] According to an embodiment, the gas fuel is a compressed hydrogen gas.

[0104] Thus, the presented method for a pressurized gas fuel system may be utilized for compressed hydrogen gas fuel, such that the safety, reliability and robustness of compressed hydrogen gas vehicles is improved.

[0105] According to a second aspect of the present invention, the objective is achieved through an arrangement for a pressurized gas fuel system of a vehicle, the pressurized gas fuel system comprising a filling conduit, at least one gas fuel tank connected to the filling conduit, and a gas fuel conduit arranged from the at least one fuel tank to an engine;

[0106] the arrangement comprising a control unit configured to:

[0107] - determine a pressure Pdet(Tdet) and a corresponding temperature Tdet of the gas fuel in the pressurized gas system;

[0108] - provide an error indication if the determined pressure Pdet(Tdet) is higher than a constant density pressure PD(Tdet) for the gas fuel at the determined temperature Tdet; Pdet(Tdet) > PD(Tdet); wherein

[0109] - the constant density pressure PD(T) is a function of a temperature T of the gas fuel in the pressurized gas system, defines a constant density for the gas fuel, and comprises a predefined normal working pressure PNWP(Tref) for the gas fuel at a reference temperature Tref.

[0110] According to a third aspect of the present invention, the objective is achieved through a vehicle comprising:

[0111] - a pressurized gas fuel system; and

[0112] - a herein described arrangement for a pressurized gas fuel system.

[0113] According to a fourth aspect, the invention relates to a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the herein described methods.

[0114] The computer program has corresponding advantages as mentioned for the method according to the first aspect.

[0115] According to a fifth aspect, the invention relates to a computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the herein described methods.

[0116] The computer-readable medium has corresponding advantages as mentioned for the method according to the first aspect. It will be appreciated that all the embodiments described for the method aspect of the invention are applicable also to one or more of the arrangement aspect, the vehicle aspect, the computer program aspect and the computer-readable medium aspect of the invention. Thus, all the embodiments described for the method aspect of the invention may be performed / implemented by the herein described arrangement, vehicle, computer program and / or the computer-readable medium. The control unit of the arrangement may also be a processing device, i.e. a device. The arrangement aspect, the vehicle aspect, the computer program aspect and the computer-readable medium aspect, and their embodiments, have advantages corresponding to the advantages mentioned above for the method aspect and its embodiments.

[0117] Brief list of figures

[0118] Embodiments of the invention will be illustrated in more detail below, along with the enclosed drawings, where similar references are used for similar parts, and where: Figure 1 schematically illustrates an example vehicle, in which aspects and embodiments of the present invention may be implemented,

[0119] Figure 2 shows a flow chart diagram for a method for a pressurized gas fuel system of a vehicle according to some aspects and / or embodiments of the present the invention,

[0120] Figure 3 schematically shows a pressure and temperature representation / diagram, illustrating a constant density pressure function PD(T),

[0121] Figure 4 schematically shows a pressure and temperature representation / diagram, illustrating a constant density pressure function PD(T) and some additional constant density pressure functions PD_ad1(T), PD_ad2(T), PD_ad3(T),

[0122] Figure 5 schematically illustrates a control unit according to various embodiments of the present invention.

[0123] Description of preferred embodiments Figure 1 schematically shows an exemplary heavy vehicle 500, such for example a truck or a bus, which will be used to explain the herein presented solution and its aspects and embodiments. The aspects and embodiments are, however, not limited to use in vehicles as the ones shown in figure 1, but may also be used in other vehicles, such as lighter vehicles, for example cars or other types of vehicles.

[0124] A vehicle 100, as shown schematically in Figures 1, comprises multiple wheels, of which at least one pair comprises drive wheels 110, 111. The vehicle 100 furthermore comprises a powertrain 120 configured to transfer a torque between at least one power source 101, such as e.g. at least one combustion engine, or a combination of a combustion engine and at least one electric machine, implementing a so-called hybrid drive, to the at least one pair of drive wheels 110, 111.

[0125] The combustion engine 101 may be driven by gas provided by a pressurized gas fuel system 130. The pressurized gas fuel system 130 comprises a filling conduit 131, at least one gas fuel tank 132 connected to the filling conduit 131, and a gas fuel conduit 133 arranged from the at least one fuel tank 132 to the combustion engine 101. The pressurized gas fuel system 130 is thus configured to receive gas fuel 135 from a tank station, to store the gas fuel 135 in the at least one gas fuel tank 132, and to provide the gas fuel 135 to the combustion engine 101.

[0126] The torque provided by the at least one power source 101 may be provided to the at least one pair of drive wheels 110, 111 via a central gear, such as e.g. a customary differential, and drive shafts connected with the central gear.

[0127] The vehicle 100 may further comprise an exhaust treatment system 140, configured to purify exhaust gases resulting from the combustion of the gas fuel 135 in the combustion engine 101.

[0128] A control unit / device / system 150 may be configured for supervising and / or controlling the pressurized gas fuel system 130. For example, the control unit / device / system 150 may be connected to one or more pressure sensors 136, and / or one or more temperature sensors 137. The one or more one or more pressure sensors 136 may for example be positioned in the pressurized gas fuel system 130, such as in or at the filling conduit 131, the at least one gas fuel tank 132 and / or the gas fuel conduit 133. The one or more one or more temperature sensors 137 may for example be positioned in the pressurized gas fuel system 130, such in or at the filling conduit 131, the at least one gas fuel tank 132 and / or the gas fuel conduit 133, and / or may be positioned externally on the vehicle to sense an ambient temperature surrounding the vehicle 100. The control unit / device / system 150 is in figure 1 illustrated as one single unit / device / system. However, as is understood by a skilled person, the unit / device / system 150 may be implemented by utilization of essentially any number of units / devices / systems.

[0129] In figure 1, only the components / units / devices / entities of the vehicle being useful for understanding the present invention are schematically illustrated. However, the vehicle 100 may of course comprise a large number of other components / units / devices / entities.

[0130] Figure 2 shows a flow chart diagram for a method 200 for for a pressurized gas fuel system 130 of a vehicle 100 according to some aspects and embodiments of the present the invention. The the pressurized gas fuel system 130 comprises a filling conduit 131, at least one gas fuel tank 132 connected to the filling conduit 131, and a gas fuel conduit 133 arranged from the at least one fuel tank 132 to an engine 101, as explained above.

[0131] The method steps of figure 2 may be performed in another order than illustrated in figure 2, as long as the information needed for performing a method step is available when the step is to be performed.

[0132] In a first step 210 of the method 200 illustrated in figure 2, a pressure Pdet(Tdet) and a corresponding temperature Tdet of the gas fuel 135 in the pressurized gas system 130 is determined.

[0133] According to various embodiments, the determination 210 of the pressure Pdet(Tdet) and the corresponding temperature Tdet of the gas fuel 135 may be performed at one of a number of points in time, for which it is suitable to perform such determinations, i.e. for which such determined pressure and temperature values may be useful.

[0134] For example, the pressure Pdet(Tdet) and the corresponding temperature Tdet may be determined 210 when an ignition of the vehicle 100 is turned on. Thus, the determination 210 is then for example performed directly after filling of the at least one fuel tank has been completed, since the ignition is normally turned off during filling of gas, and is turned on again after the filling is completed. Hereby, the pressure Pdet(Tdet) and the corresponding temperature Tdet may be determined 210 when the at least one fuel tank has been filled with gas fuel 135, i.e. when the at least one fuel tank is full.

[0135] The pressure Pdet(Tdet) and the corresponding temperature Tdet may also be determined 210 during filling of the at least one fuel tank 132 with gas fuel 135.

[0136] The pressure Pdet(Tdet) and the corresponding temperature Tdet may also be determined 210 when the vehicle 100 is in operation, e.g. when the vehicle is driven by its driver.

[0137] The determination 210 of the pressure Pdet(Tdet) and the corresponding temperature Tdet may, according to some embodiments, utilize one or more sensors 136, 137 for measuring present pressure and / or temperature values, as above mentioned and schematically illustrated in figure 1.

[0138] For example, the determination 210 of the pressure Pdet(Tdet) of the gas fuel 135 may be performed by utilization of at least one pressure sensor 136 in the pressurized gas fuel system 130. Such pressure sensors 136 may be arranged in or at the filling conduit 131, in or at the at least one gas fuel tank 132, and / or in or at the gas fuel conduit 133.

[0139] The determination 210 of the temperature Tdet of the gas fuel 135 may, according to an embodiment, be performed by utilization of at least one temperature sensor 137 arranged in the pressurized gas fuel system 130. Such temperature sensors 137 may be arranged in or at the filling conduit 131, in or at the at least one gas fuel tank 132, and / or in or at the gas fuel conduit 133.

[0140] Alternatively, the determination 210 of the temperature Tdet of the gas fuel 135 in the pressurized gas system 130 may, according to an embodiment, be performed by utilization of at least one ambient temperature sensor 137. The temperature Tdet of the gas fuel 135 may then be approximated as having the same temperature as the ambient temperature. According to an embodiment, the determination 210 of the temperature Tdet of the gas fuel 135 in the pressurized gas system 130 is based on a temperature model for the pressurized gas fuel system 130. The temperature model may then be utilized together with one or more temperature measurements provided by one or more temperature sensors 137 arranged in the pressurized gas fuel system 130 and / or by an ambient temperature sensor 137 for determining 210 the temperature Tdet of the gas fuel 135 in the pressurized gas system 130.

[0141] Further, the determination 210 of the pressure Pdet(Tdet) and the corresponding temperature Tdet may, according to some embodiments, be performed based on temperature information provided by an offboard entity 170, such as a weather / meteorological association / institute / company.

[0142] The determination 210 of the pressure Pdet(Tdet) and the corresponding temperature Tdet may comprise one or more estimations, calculations, predictions and / or extrapolations based on one or more pressure and / or temperature measurements performed previously and / or at another position of the vehicle. The one or more estimations, calculations and / or extrapolations may here also be based on a temperature model for the pressurized gas fuel system 130. Also, the determination 210 of the pressure Pdet(Tdet) and / or the corresponding temperature Tdet may, according to some embodiments, be based on temperature information provided by an offboard entity 170, i.e. based on externally obtained weather conditions / data / predictions and / or positioning information, such as global positioning system (GPS) information.

[0143] The determination 210 of the pressure Pdet(Tdet) and the corresponding temperature Tdet may, according to some embodiments, comprise predictions of the pressure Pdet(Tdet) based on one or more predictions of the temperature Tdet. The one or more predictions of the temperature Tdet may be based on weather forecast information for an upcoming route ahead of the vehicle. The one or more predictions of the temperature Tdet may also be based on temperature information associated with an indoor space the vehicle is travelling to, such as a garage, a workshop, a washing facility, or a painting facility. In a second step 220, an error indication E is provided if the determined pressure Pdet(Tdet) is higher than a constant density pressure PD(Tdet) for the gas fuel 135 at the determined temperature Tdet; Pdet(Tdet) > PD(Tdet). The constant density pressure PD(T) is a function of a temperature T of the gas fuel 135 in the pressurized gas system 130 which defines a constant density for the gas fuel 135. The constant density pressure PD(T) comprises a predefined normal working pressure PNWP(Tref) for the gas fuel 135 at a reference temperature Tret

[0144] One non-limiting example of a constant density pressure PD(T) is schematically illustrated in figure 3 for a for a compressed natural gas fuel. In this non-limiting example, the constant density pressure PD(T) comprises a predefined normal working pressure PNWP(Tref) of 200 bar at a reference temperature Tref of 15 °C.

[0145] Thus, if the determined pressure Pdet(Tdet) is higher than the constant density pressure PD(Tdet) at the determined temperature Tdet; Pdet(Tdet) > PD(Tdet); which means that the determined pressure Pdet(Tdet) is above the constant density pressure function PD(Tdet), as illustrated in figure 3, then the error indication E is provided.

[0146] According to an embodiment, for which the gas fuel 135 is a compressed natural gas, the reference temperature Tref is in an interval of 10°C to 20°C, for example 20°C, as exemplified in figure 3. The predefined normal working pressure PNWP(Tref) is then in an interval of 150 bar to 250 bar, for example 200 bar, as exemplified in figure 3.

[0147] Also, the constant density pressure PD(T1) at a first temperature T1 is equal to a maximal allowed working pressure PMAWP; PD(T1) = PMAWP.

[0148] If the gas fuel 135 is a compressed natural gas, the first temperature T1 may for example be in an interval of 50 °C to 85 °C, such as 57 °C. The maximal allowed working pressure PMAWP may for example be in an interval of 250 bar to 330 bar, such as 260 bar, as schematically illustrated in figure 3.

[0149] According to an embodiment, in a third step 230 of the method 200 in figure 2, at least one additional constant density pressure PD_ad1(T), PD_ad2(T), PD_ad3(T) is defined. Some non-limiting examples of such at least one additional constant density pressure PD_adi(T), PD_ad2(T), Po_ad3(T) for a compressed natural gas fuel are schematically illustrated in figure 4.

[0150] Each of the at least one additional constant density pressure PD_ad1(T), PD_ad2(T), PD_ad3(T) is here a function of the temperature T of the gas fuel 135 in the pressurized gas system 130. Each of the at least one additional constant density pressure PD_ad1(T), PD_ad2(T), PD_ad3(T) further defines an individual / separate constant density for the gas fuel 135, and comprises an additional working pressure PAWP1(Tref), PAWP2(Tref), PAWP3(Tref) for the gas fuel 135 at the reference temperature Tref.

[0151] Further, each of the at least one additional working pressure PAWPi(Tref), PAWP2(Tref), PAWP3(Tref) illustrated in figure 4 is at the reference temperature Tref higher than the above mentioned predefined normal working pressure PNWP(Tref) at the reference temperature Tref for the above-mentioned constant density pressure PD (TI). Thus, PAWPl(Tref) > PNWP(Tref), PAWP2(Tref) > PNWP(Tref), and PAWP3(Tref) > PNWP(Tref).

[0152] In a fourth step 240 of the method, one or more corresponding additional error indications E1, E2, E3 are provided if the determined pressure Pdet(Tdet) is higher than one or more of the at least one additional constant density pressure PD_adi(Tdet), PD_ad2(Tdet), Po_ad3(Tdet) for the gas fuel 135 at the determined temperature Tdet;

[0153] Pdet(Tdet) > PD_ad1(Tdet), Pdet(Tdet) > PD_ad2(Tdet), Pdet(Tdet) > PD_ad3(Tdet); respectively.

[0154] For example, if the determined pressure Pdet(Tdet) is has a value as exemplified in figure 4, then an error indication E is provided because the determined pressure Pdet(Tdet) exceeds the above-mentioned constant density pressure PD(Tdet) at the determined temperature Tdet. Also, since the determined pressure Pdet(Tdet) exceeds a first additional constant density pressure PD_ad1(Tdet), then a first error indication E1 is further provided. However, neither a second error indication E2 associated with a second additional constant density pressure PD_ad2(Tdet) nor a third error indication E3 associated with a third additional constant density pressure PD_ad3(Tdet) are provided because the determined pressure Pdet(Tdet) is below both of the second second additional constant density pressure PD_ad2(Tdet) and the a third additional constant density pressure PD_ad3(Tdet) at the determined temperature Tdet. According to an embodiment, the first additional constant density pressure PD_adi(T) comprises a first additional working pressure PAWPi(Tref) for the gas fuel 135 at the reference temperature Tret, which is higher than the predefined normal working pressure PNWP(Tref) at the reference temperature Tret for the constant density pressure PD(T). Thus, PAWp-i(Tref) > PNWP(Tref). Further, a maximal value PD_adi_max of the first additional constant density pressure Po_adi(T) is equal to a maximal allowed working pressure PMA P minus an offset A, such that the shape of the function of the first additional constant density pressure Po_adi(T) changes at higher temperatures, from a slope to a horizontal line at an offset below the maximal allowed working pressure PMA P. Thus, Po_adi_max = PMA P - A.

[0155] As a non-limiting example for a compressed natural gas fuel, the first additional working pressure PAWP1(Tref) at the reference temperature Tref is in an interval of 210 bar to 230 bar, for example 220 bar. The offset A from the maximal allowed working pressure PMAWP may then for example be in an interval of 5 bar to 15 bar, such as 10 bar.

[0156] According to an embodiment, a second additional working pressure PAWP2(Tref) for the gas fuel 135 at the reference temperature Tref is higher than the first additional working pressure PAWP1(Tref) at the reference temperature Tref. Thus, PAWP2(Tref) > PAWP1(Tref), as illustrated in figure 4. Also, a value of the second additional constant density pressure PD_ad2(T2) at a second temperature T2 is equal to the maximal allowed working pressure PMAWP; PD_ad2(T2) = PMAWP.

[0157] As a non-limiting example for a compressed natural gas, the second additional working pressure PAWP2(Tref) at the reference temperature Tref is in an interval of 230 bar to 250 bar, for example 240 bar, and the second temperature T2 is in an interval of 20 °C to 30 °C, for example 25 °C. The second temperature T2 may then for example correspond to a temperature of a workshop, a garage and / or a painting facility.

[0158] As a non-limiting example for a compressed natural gas, a third additional constant density pressure PD_ad3(T) comprises a third additional working pressure PAWP3(Tref) for the gas fuel 135 at the reference temperature Tret, as schematically shown in figure 4. The third additional working pressure PAWP3(Tref) is higher than the second additional working pressure PAWP2(Tref) at the reference temperature Tret Thus, PAWP3(Tref) > PAWP2(Tref). A value of the third additional constant density pressure PD_ad3(T3) at a third temperature T3 is equal to the maximal allowed working pressure PMAWP; PD_ad3(T3) = PMAWP.

[0159] As a non-limiting example for a compressed natural gas, the third additional working pressure PAWP3(Tref) at the reference temperature Tref is higher than the maximal allowed working pressure PMAWP at the reference temperature Tref; PAWP3(Tref) > PMAWP. Also, the third temperature T3 may for example be in an interval of 0 °C to 10 °C, such as 5 °C. The third temperature T3 may for example correspond to a temperature of a washing facility.

[0160] According to the non-limiting example illustrated in figure 4, in which the gas fuel is a compressed natural gas, the maximal allowed working pressure PMAWP in an interval of 250 bar - 330 bar, for example 260 bar or 325 bar.

[0161] As explained above, figure 4 is a schematic illustration of the constant density pressure PD(T) and the one additional constant density pressure PD_ad1(T), PD_ad2(T), PD_ad3(T). These functions are in figure 4 illustrated as straight lines. However, as understood by a skilled person, these functions may also define non-straight lines.

[0162] At the reference temperature Tret, the third additional constant density pressure PD_ad3(Tref) has a higher value than the second additional constant density pressure PD_ad2(Tref), the second additional constant density pressure PD_ad2(Tref) has a higher value that the first additional constant density pressure PD_ad1(Tref), and the first additional constant density pressure PD_ad1(Tref) has a higher value than constant density pressure PD(Tref); PD_ad3(Tref) > PD_ad2(Tref) > PD_ad1(Tref) > PD(Tref). A pressure difference between the constant density pressure PD(T) and the at least one additional constant density pressure PD_ad1(T), PD_ad2(T), PD_ad3(T) may be determined based on the functions of one or more of the constant density pressure PD(T) and the one additional constant density pressure PD_ad1(T), PD_ad2(T), PD_ad3(T), and also based on suitable temperatures where each function exceeds the maximal allowed working pressure PMAWP for the system. According to an embodiment, the error indication E and / or the one or more additional error indications E1, E2, E3 comprise a suitable amount of information for its further utilization. For example, the error indication E and / or the one or more additional error indications E1, E2, E3 may comprise the determined pressure Pdet(Tdet), the determined temperature Tdet, and / or at least one error code.

[0163] The error indication E and / or the one or more additional error indications E1, E2, E3 may also comprise positioning information, such as global positioning system (GPS) information, indicating a geographical position at which an ignition of the vehicle 100 was last turned off before the determination 210 of the pressure Pdet(Tdet) and the temperature Tdet and / or indicating a geographical position at which the pressure Pdet(Tdet) and the temperature Tdet are determined 210.

[0164] The error indication E and / or the one or more additional error indications E1, E2, E3 may also comprise temporal information, such as information indicating a point in time when an ignition of the vehicle 100 was last turned off before the determination 210 of the pressure Pdet(Tdet) and the temperature Tdet, indicating a point in time when the determination 210 of the pressure Pdet(Tdet) and the temperature Tdet is performed, and / or indicating a point in time when the at least one fuel tank 132 is filled with gas fuel 135.

[0165] The error indication E and / or the one or more additional error indications E1, E2, E3 may, according to various embodiments, be provided 220 to a driver interface 160 of the vehicle 100, to a control device 180 configured for autonomous control of the vehicle 100, to an offboard entity 170, and / or a workshop. The error indication E and / or the one or more additional error indications E1, E2, E3 may be provided to the driver interface 160 and / or the control device 180 via an onboard network or connection of some kind, comprising e.g. a controller area network (CAN). The error indication E and / or the one or more additional error indications E1, E2, E3 may also be provided to an offboard entity 170 and / or a workshop via a suitable radio connection. The offboard entity 170 may for example be a local technician helpdesk or some other kind of service / information centre, or may be connected to a local technician helpdesk, some other kind of service / information centre and / or a workshop via some kind of wired and / or wireless network. Based on the provided error indication E and / or the one or more additional error indications E1, E2, E3, the offboard entity, the workshop, the local technician helpdesk, and or the service / information centre may perform an analysis of the gas fuel situation. For example, faulty or inaccurately set up tank stations, i.e. tank stations having an inaccurate gas pressure set up, may be detected and / or identified. Suitable steps and measures, such as contact with proper authorities and / or the faulty or inaccurate tank stations, may be taken based on the analysis.

[0166] Also, vehicles that need to be checked at a workshop due to too high experienced pressures may be detected and / or identified. Such vehicles may by suitable alarm indications via the driver interface be requested to visit a workshop.

[0167] Alternatively, if the determined pressure Pdet(Tdet) is very high, for example if it exceeds the maximal allowed working pressure PMAWP, the error indication E and / or the one or more additional error indications E1, E2, E3 provided to the driver interface 160 may generate an alarm to the driver, instructing the driver to drive a certain distance along a recommended route, until some gas fuel has been consumed in the combustion engine, such that the amount of gas fuel in the at least one gas fuel tank has been reduced enough to reduce the pressure in the pressurized gas fuel system 130 to a less dangerous level. The recommended route may comprise roads outside of the city, along which a potential fire would be less harmful.

[0168] Correspondingly, for an autonomous vehicle, the error indication E and / or the one or more additional error indications E1, E2, E3 provided to the control device 180 configured for autonomous control may be utilized by the control device 180 to autonomously control the vehicle to drive a suitable distance, such that the amount of gas fuel, and thereby also the pressure, in the at least one gas fuel tank has been reduced if the determined pressure Pdet(Tdet) is very high, for example if it exceeds the maximal allowed working pressure PMA P.

[0169] According to some above mentioned embodiments, the determination 210 of the pressure Pdet(Tdet) and the corresponding temperature Tdet may comprise predictions of the pressure Pdet(Tdet) based on one or more predictions of the temperature Tdet for an upcoming route ahead of the vehicle. The predicted pressure Pdet(Tdet) may then indicate that it will become dangerously high if the vehicle continues to travel along the route, which is indicated in the the error indication E and / or the one or more additional error indications E1, E2, E3. For a manually driven vehicle, such error indications may be presented to the driver as a warning that the route might be dangerous to travel, possibly together with a suggestion for an alternative route to travel instead, where the alternative route is predicted to result in lower gas fuel pressure. For an autonomous vehicle, such error indications may be provided to the control device 180, and will be interpreted as a request to change to another route, which is predicted to result in lower pressures.

[0170] Above, the herein presented method 200 for a pressurized gas fuel system 130 of a vehicle has been exemplified by some embodiments for a pressurized gas fuel system 130 for compressed natural gas. However, the herein described method and arrangement aspects, and their corresponding embodiments, may also be implemented in other pressurized gas fuel systems 130. For example, the herein described method and arrangement may also be utilized for a pressurized gas fuel system 130 for compressed hydrogen gas fuel.

[0171] Compressed hydrogen gas fuel is compressed to relatively high pressures in the pressurized gas fuel system 130. As non-limiting examples, a normal working pressure PNWP(Tref) for the compressed hydrogen gas may be predefined to an interval of 300 bar to 400 bar, for example 350 bar, or even to an interval of 600 bar till 800 bar, for example 700 bar, in order to increase the reach / range of the vehicle. Also, the hydrogen gas fuel temperatures may become relatively high in a pressurized hydrogen gas fuel system.

[0172] For compressed hydrogen gas fuel, corresponding functions for a constant density pressure PD(T), and possibly also for at least one additional constant density pressure PD_ad1(T), PD_ad2(T), PD_ad3(T) may be defined. These functions will have higher pressure and temperature values than shown in figure 4 for compressed natural gas fuel. However, the method principles explained above for compressed natural gas fuel apply also to compressed hydrogen gas fuel. Thus, the pressure Pdet(Tdet) and a corresponding temperature Tdet of the gas fuel 135 in the pressurized gas system 130 are determined, and are compared to the functions for the constant density pressure PD(T), and possibly also for the at least one additional constant density pressure PD_ad1(T), PD_ad2(T), PD_ad3(T). Error indications are then provided if the determined pressure Pdet(Tdet) exceeds one or more of the functions at the determined temperature Tdet. Thus, the aspects and embodiments explained above for compressed natural gas fuel may also be utilized for compressed hydrogen gas fuel, but at higher levels for the pressures and temperatures.

[0173] According to an aspect, an arrangement 400 for a pressurized gas fuel system 130 of a vehicle 100 presented. As mentioned above, the pressurized gas fuel system 130 comprises a filling conduit 131, at least one gas fuel tank 132 connected to the filling conduit 131, and a gas fuel conduit 133 arranged from the at least one fuel tank 132 to an engine 101.

[0174] The arrangement 400 further comprises a control unit 150 configured to determine 210 a pressure Pdet(Tdet) and a corresponding temperature Tdet of the gas fuel 350 in the pressurized gas system 130.

[0175] The control unit 150 is also configured to provide 220 an error indication E if the determined pressure Pdet(Tdet) is higher than a constant density pressure Po(Tdet) for the gas fuel 135 at the determined temperature Tdet; Pdet(Tdet) > Po(Tdet).

[0176] As explained above, the constant density pressure PD(T) is a function of a temperature T of the gas fuel 135 in the pressurized gas system 130, defines a constant density for the gas fuel 135, and comprises a predefined normal working pressure PNWP(Tref) for the gas fuel 135 at a reference temperature Tref.

[0177] According to an aspect, a vehicle 100 is presented. The vehicle 100 comprises a pressurized gas fuel system 130 and a herein presented arrangement 400.

[0178] Figure 5 shows in schematic representation a control unit 150. The control unit 150 comprises a computing unit 501, which can be constituted by essentially any suitable type of processor or microcomputer, for example a circuit for digital signal processing (Digital Signal Processor, DSP), or a circuit having a predetermined specific function (Application Specific Integrated Circuit, ASIC). The computing unit 501 is connected to a memory unit 502 arranged in the control unit 150, which memory unit provides the computing unit 501 with, for example, the stored program code and / or the stored data which the computing unit 501 requires to be able to perform computations. The computing unit 501 is also arranged to store partial or final results of computations in the memory unit 502.

[0179] In addition, the control unit 150 is provided with devices 511, 512, 513, 514 for receiving and transmitting input and output signals. These input and output signals can contain waveforms, impulses, or other attributes which, by the devices 511, 513 for the reception of input signals, can be detected as information and can be converted into signals which can be processed by the computing unit 501. These signals are then made available to the computing unit 501. The devices 512, 514 for the transmission of output signals are arranged to convert signals received from the computing unit 501 in order to create output signals by, for example, modulating the signals, which can be transmitted to other parts of and / or systems in the vehicle. Each of the connections to the devices for receiving and transmitting input and output signals can be constituted by one or more of a cable; a data bus, such as a CAN bus (Controller Area Network bus), a MOST bus (Media Orientated Systems Transport bus), or some other bus configuration; an ethernet connection; or by a suitable wireless connection. A person skilled in the art will appreciate that the above-stated computer can be constituted by the computing unit 501 and that the above- stated memory can be constituted by the memory unit 502.

[0180] Control systems in modern vehicles commonly comprise communication bus systems consisting of one or more communication buses for linking a number of electronic control units (ECU's), or controllers, and various components located on the vehicle. Such a control system can comprise a large number of control units and the responsibility for a specific function can be divided amongst more than one control unit. Vehicles of the shown type thus often comprise significantly more control units than are shown in figures 1 and 5, which is well known to the person skilled in the art within this technical field. In a shown embodiment, the present invention may be implemented by the one or more herein mentioned control units or processing arrangements 150. The invention can also, however, be implemented wholly or partially in one or more other control units already present in the vehicle, or in some control unit dedicated to the present invention.

[0181] Here and in this document, control units, control entities or processing arrangements are sometimes described as being arranged for performing the methods and / or steps 210, 220, 230, 240 according to the invention. This also includes that the units, entities or processing arrangements are designed to and / or configured to perform these method steps.

[0182] One or more control entities 310, 320, 330, 340 may be arranged for performing the methods and / or steps. Such entities 310, 320, 330, 340 may be arranged as separate entities, or may be logically separated but physically implemented in the same unit, or may be both logically and physically arranged together. These control entities 310, 320, 330, 340 may for example correspond to groups of instructions, which can be in the form of programming code, that are input into, and are utilized by a processor / computing unit 501 when the entities are active and / or are utilized for performing its method steps, respectively.

[0183] The present invention is not limited to the above described embodiments. Instead, the present invention relates to, and encompasses all different embodiments being included within the scope of the independent claims.

Claims

Claims1. A method (200) for a pressurized gas fuel system (130) of a vehicle (100), the pressurized gas fuel system (130) comprising a filling conduit (131), at least one gas fuel tank (132) connected to the filling conduit (131), and a gas fuel conduit (133) arranged from the at least one fuel tank (132) to an engine (101); the method (200) comprising:- determining (210) a pressure Pdet(Tdet) and a corresponding temperature Tdet of the gas fuel (135) in the pressurized gas system (130);- providing (220) an error indication (E) if the determined pressure Pdet(Tdet) is higher than a constant density pressure PD(Tdet) for the gas fuel (135) at the determined temperature Tdet; Pdet(Tdet) > PD(Tdet); wherein- the constant density pressure PD(T) is a function of a temperature T of the gas fuel (135) in the pressurized gas system (130), defines a constant density for the gas fuel (135), and comprises a predefined normal working pressure PNWP(Tref) for the gas fuel (135) at a reference temperature Tref2. The method (200) as claimed in claim 1, wherein the determination (210) of the pressure Pdet(Tdet) and the corresponding temperature Tdet of the gas fuel (135) is performed at one point in time in the group of:- when an ignition of the vehicle (100) is turned on;- during filling of the at least one fuel tank (132) with gas fuel (135);- when the at least one fuel tank (132) has been filled with gas fuel (135); and -when the vehicle (100) is in operation.

3. The method (200) as claimed in any one of claims 1-2, wherein- the gas fuel (135) is a compressed natural gas;- the reference temperature Tref has a value in an interval of 10°C to 20°C; and - the predefined normal working pressure PNWP(Tref) has a value in an interval of 150 bar to 250 bar.

4. The method (200) as claimed in any one of claims 1-3, wherein the constant density pressure PD (TI) at a first temperature Ti is equal to a maximal allowed working pressure PMAWP; PD(T1) = PMAWP.

5. The method (200) as claimed in claim 4, wherein- the gas fuel (135) is a compressed natural gas;- the first temperature T1 has a value in an interval of 50 °C to 85 °C; and- the maximal allowed working pressure PMA P has a value in an interval of 250 bar to 330 bar for the gas fuel (135) being a compressed natural gas.

6. The method (200) as claimed in any one of claims 1-5, further comprising:- defining (230) at least one additional constant density pressure PD_adi(T), Po_ad2(T), Po_ad3(T), wherein-- the at least one additional constant density pressure PD_ad1(T), PD_ad2(T), PD_ad3(T) is a function of the temperature T of the gas fuel (135) in the pressurized gas system (130), defines a constant density for the gas fuel (135), and comprises at least one additional working pressure PAWP-i(Tref), PAWP2(Tref), PAWP3(Tref), for the gas fuel (135) at the reference temperature Tret, respectively; and-- each of the at least one additional working pressure PAWP-i(Tref), PAWP2(Tref), PAWP3(Tref) has a higher value than the predefined normal working pressure PNWP(Tref) at the reference temperature Tret; PAWPi(Tref) > PNWP(Tref), PAWP2(Tref) > PNWP(Tref), PA Ps(Tref) > PNWP(Tref); and- providing (240) one or more additional error indications (E1, E2, E3) if the determined pressure Pdet(Tdet) has a higher value than one or more of the at least one additional constant density pressure PD_ad1(Tdet), PD_ad2(Tdet), PD_ad3(Tdet) for the gas fuel (135) at the determined temperature Tdet; Pdet(Tdet) > PD_ad1(Tdet), Pdet(Tdet) > PD_ad2(Tdet), Pdet(Tdet) > PD_ad3(Tdet); respectively.

7. The method (200) as claimed in claim 6, wherein- the at least one additional constant density pressure PD_ad1(T), PD_ad2(T), PD_ad3(T) comprises a first additional constant density pressure Po_adi(T) comprising a first additional working pressure PAWp-i(Tref) for the gas fuel (135) at the reference temperature Tret;- the first additional working pressure PAWP1(Tref) has a higher value than the predefined normal working pressure PNWP(Tref); PAWP1(Tref) > PNWP(Tref); and- a maximal value PD_ _ad1_max of the first additional constant density pressure Po_adi(T)has a value equal to a maximal allowed working pressure PMAWP minus an offset Δ; PD_ad1_max = PMAWP – Δ.

8. The method (200) as claimed in claim 7, wherein- the gas fuel (135) is a compressed natural gas; and- the first additional working pressure PAWPi(Tref) has a value in an interval of 210 bar to 230 bar; and- the offset Δ has a value in an interval of 5 bar to 15 bar.

9. The method (200) as claimed in any one of claims 7-8, wherein- the at least one additional constant density pressure PD_adi(T), Po_ad2(T), Po_ad3(T) comprises a second additional constant density pressure Po_ad2(T) comprising a second additional working pressure PAWP2(Tref) for the gas fuel (135) at the reference temperature Tret;- the second additional working pressure PAWP2(Tref) has a higher value than the first additional working pressure PAWp-i(Tref); PAWP2(Tref) > PAWp-i(Tref); and- a value of the second additional constant density pressure Po_ad2 (T2) at a second temperature T2 is equal to the maximal allowed working pressure PMA P; Po_ad2 (T2) = PMA P.

10. The method (200) as claimed in claim 9, wherein- the gas fuel (135) is a compressed natural gas;- the second additional working pressure PAWP2(Tref) has a value in an interval of 230 bar to 250 bar; and- the second temperature T2 has a value in an interval of 20 °C to 30 °C.

11. The method (200) as claimed in any one of claims 9-10, wherein- the at least one additional constant density pressure PD_ad1(T), PD_ad2(T), PD_ad3(T) comprises a third additional constant density pressure Po_ad3(T) comprising a third additional working pressure PA Ps(Tref) for the gas fuel (135) at the reference temperature Tret;- the third additional working pressure PA Ps(Tref) has a higher value than the second additional working pressure PAWP2(Tref); PA Ps(Tref) > PAWP2(Tref); and- a value of the third additional constant density pressure Po_ad3 (T3) at a thirdtemperature T3 is equal to the maximal allowed working pressure PMAWP; PD_ad3 (T3) = PMAWP.

12. The method (200) as claimed in claim 11, wherein- the third additional working pressure PAWP3(Tref) has a higher value than the maximal allowed working pressure PMAWP; PAWP3(Tref) > PMAWP; and- the third temperature T3 has a value in an interval of 0 °C to 10 °C.

13. The method (200) as claimed in any one of claims 7-12, wherein- the gas fuel (135) is a compressed natural gas; and- the maximal allowed working pressure PMAWP has a value an interval of 250 bar – 330 bar.

14. The method (200) as claimed in any one of claims 1-13, wherein the determination (210) of the pressure Pdet(Tdet) is performed by utilization of at least one pressure sensor (136) in the pressurized gas fuel system (130).

15. The method (200) as claimed in any one of claims 1-14, wherein the determination (210) of the temperature Tdet is performed by utilization of one or more in the group of:- at least one temperature sensor (137) arranged in the pressurized gas fuel system (130);- at least one ambient temperature sensor (137);- temperature information provided by an offboard entity (170); and- a temperature model for the pressurized gas fuel system (130).

16. The method (200) as claimed in any one of claims 1-15, wherein the error indication (E) comprises one or more in the group of:- the determined pressure Pdet(Tdet);- the determined temperature Tdet;- at least one error code;- a geographical position at which an ignition of the vehicle (100) was last turned off before the determination (210) of the pressure Pdet(Tdet) and the temperature Tdet; - a geographical position at which the pressure Pdet(Tdet) and the temperature Tdet are determined (210);- a point in time when an ignition of the vehicle (100) was last turned off before the determination (210) of the pressure Pdet(Tdet) and the temperature Tdet;- a point in time when the determination (210) of the pressure Pdet(Tdet) and the temperature Tdet is performed; and- a point in time when the at least one fuel tank (132) is filled with gas fuel (135).

17. The method (200) as claimed in any one of claims 1-16, wherein the error indication (E) is provided (220) to one or more in the group of:- a driver interface (160) of the vehicle (100);- a control device (180) configured for autonomous control of the vehicle 100.- an offboard entity (170); and- a workshop.

18. The method (200) as claimed in any one of claims 1 -2, 4, 6-7, 9, 11-12, and 14-17, wherein the gas fuel (135) is a compressed hydrogen gas.

19. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method (200) according to any one of claims 1 -18.

20. A computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the method (200) according to any one of claims 1 -18.

21. An arrangement (400) for a pressurized gas fuel system (130) of a vehicle (100), the pressurized gas fuel system (130) comprising a filling conduit (131 ), at least one gas fuel tank (132) connected to the filling conduit (131 ), and a gas fuel conduit (133) arranged from the at least one fuel tank (132) to an engine (101);the arrangement (400) comprising a control unit (150) configured to:- determine (210) a pressure Pdet(Tdet) and a corresponding temperature Tdet of the gas fuel (350) in the pressurized gas system (130);- provide (220) an error indication (E) if the determined pressure Pdet(Tdet) is higher than a constant density pressure PD(Tdet) for the gas fuel (135) at the determined temperature Tdet; Pdet(Tdet) > PD(Tdet); wherein- the constant density pressure PD(T) is a function of a temperature T of the gas fuel (135) in the pressurized gas system (130), defines a constant density for the gas fuel (135), and comprises a predefined normal working pressure PNWp(Tref) for the gas fuel (135) at a reference temperature Tret22. A vehicle (100) comprising:- a pressurized gas fuel system (130); and- an arrangement (400) as claimed in claim 21.

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