DE102015222777A1 - Motor vehicle with fuel discharge openings and method for discharging fuel - Google Patents

Abstract

The technology disclosed herein relates to a motor vehicle 10 having: at least one exhaust port 3 and a method for blowing fuel from a motor vehicle 10. The method comprises the step of discharging fuel into the ambient air 1 from a fuel-carrying region 2 of the motor vehicle 10 through a plurality of exhaust ports third

Description

The technology disclosed herein relates to a motor vehicle having exhaust ports for fuel and a method for discharging fuel.

Motor vehicles with cryogenic pressure vessel systems (also called "CcH2 systems") are known from the prior art. Cryogenic pressure vessel systems are used, for example, for motor vehicles, in which a gaseous fuel or fuel is cold-cooled under ambient conditions and thus stored in the liquid or supercritical state of aggregation. A pressure vessel of such a system comprises an inner vessel and an outer vessel surrounding it to form a super-isolated (eg, evacuated) (intermediate) space. Therefore, highly effective insulation sheaths (eg vacuum envelopes) are provided. For example, the EP 1 546 601 B1 such a pressure vessel.

Despite good thermal insulation, the stored fuel heats up slowly. At the same time, the pressure in the pressure vessel rises slowly. If a limit pressure is exceeded, the fuel must escape via suitable safety devices in order to avoid damage to the cryogenic pressure vessel, which can also be referred to as blow-off of blow-off gas. For this purpose, pressure-operated relief valves are used, which allow a gradual escape of the medium. Downstream of the relief valves, for example, a so-called blow-off management system or boil-off management system (hereinafter BMS) can be used. A BMS may include a catalytic converter or catalyst that converts fuel (eg, hydrogen) with oxygen from the ambient air (in the case of hydrogen, the reaction product is water).

Such a blow-off management system is relatively expensive and requires a relatively expensive catalyst with precious metals. The fuel, z. On the other hand, hydrogen, on the other hand, must not be conducted directly into the ambient air, since otherwise the ignitability limit (eg 4% by volume of hydrogen in air) could be exceeded and "jet flames" could then occur, ie the fire of continuously flowing fuel, similar to a gas burner.

It is an object of the technology disclosed herein to reduce or eliminate the disadvantages of the prior art solutions. Other objects arise from the beneficial effects of the technology disclosed herein. The object (s) is / are solved by the subject matter of claim 1. The dependent claims are preferred embodiments.

The technology disclosed here is based on the consideration that a sufficiently mixed hydrogen-air mixture does not separate again under ambient conditions. Consequently, fuel can be disposed of without catalytic conversion, if sufficient and reliable mixing of fuel and air care is taken.

The technology disclosed herein relates to a motor vehicle, preferably a motor vehicle powered by a fuel cell system. The motor vehicle comprises at least one outflow opening, which is designed to discharge fuel from a fuel-carrying region of the motor vehicle into the ambient air.

The fuel-carrying region is in particular an area in which fuel accumulates, preferably an area in which fuel is conducted and / or stored, preferably the fuel-carrying components of the pressure vessel system and / or of the fuel cell system.

The ambient air is the air that surrounds the motor vehicle. The ambient air, which may be present in the interior or in the fuel-carrying area, does not belong to the ambient air. As the ambient air so in particular not the exhaust air from the cathode and / or anode of the fuel cell is considered. Suitably, the at least one outflow opening flows around ambient air sucked in from the external vehicle environment.

Preferably, the motor vehicle comprises a plurality of outflow openings, which are designed to discharge fuel from a fuel-carrying region of the motor vehicle into the ambient air.

The at least one, preferably a plurality, outflow opening (s) may be designed such that they limit the fuel mass flow that can escape from each of the outflow openings. The maximum fuel mass flow may in particular be selected so that the maximum fuel mass flow is in the ambient air below the fuel mass flow limit, which can receive a fuel flame and / or can arise. The fuel mass flow limit value thus specifies the minimum mass flow which is necessary for the preservation or the formation of a fuel flame ("fame quenching limit"). If hydrogen is used as the fuel, the at least one outflow opening can be designed such that a maximum hydrogen mass flow of less than 0.028 mg / s, preferably less than 0.005 mg / s and particularly preferably less than 0, 003 mg / s can escape from each of the at least one outflow opening. If the mass flow of hydrogen into the ambient air is below this value, no hydrogen flame can be obtained or produced under ideal conditions. This is known in the scientific literature and described, for example, in the following article:
Butler, M., Axelbaum, R., Moran, C., and Sunderland, P., "Flame Quenching Limits of Hydrogen Leaks," SAE Int. J. Passeng. Cars-Mech. Syst. 1 (1): 605-612, 2009, doi: 10.4271 / 2008-01-0726 , The individual outflow openings can each be arranged spaced apart from one another such that the fuel does not form a common fuel flame from adjacent outflow openings.

The at least one outflow opening can be formed by at least one hydrogen-permeable membrane. Preferably, the membrane is hydrogen permeable and waterproof. For example, a fabric material can be used which is waterproof and permeable to hydrogen.

At the at least one outflow opening, a valve may be provided. The at least one valve may be configured to control or regulate the outflow of fuel. Preferably, the valve is a passive valve, in particular purely mechanical valve. The at least one valve may expediently discharge the fuel into the environment when a pressure limit in the fuel-carrying region is exceeded. The at least one valve may in particular be designed as a check valve which prevents a return flow of fuel and the penetration of ambient air into a fuel-carrying area. The valve may for example comprise an elastic layer. The elastic layer may be configured to release the at least one outflow opening when the pressure in the fuel-carrying area exceeds the pressure limit value. For example, perforations or holes may be provided in the elastic layer, which are closed at atmospheric pressure, and from the pressure limit, z. B. 1.5 bar _ü (ie 1.5 bar over atmospheric pressure), preferably 0.5 bar _ü and more preferably 0.1 bar _ü , open.

The at least one outflow opening and / or the at least one valve can be provided at least partially on the outer skin of the vehicle or on the outer contour of the motor vehicle, in particular in a region of the outer contour which does not cover in the vertical direction or only to a small extent by another component becomes. The at least one outflow opening and / or the at least one valve are particularly preferably provided on the vehicle roof, on the engine hood, on the boot cover, on a rear spoiler, and / or on a front or rear wing. Advantageously, the fuel can thus escape quickly and safely from the motor vehicle without fuel gas accumulating on other vehicle components. The at least one outflow opening and / or the at least one valve may be designed to be exposed to the vehicle surroundings. Furthermore, a cover can be provided for visual protection and / or weather protection, in which case preferably the device disclosed here for increasing the flow rate of the ambient air at the at least one outflow opening can likewise be present.

The technology disclosed herein further relates to a device for increasing the flow rate of the ambient air at the at least one outflow opening. The device for increasing the flow rate may in particular be designed to generate a flow of the ambient air at the at least one outflow opening during an inactive phase of the motor vehicle, preferably a turbulent flow. The term "inactive phase of the motor vehicle" is to be regarded as a phase of non-use, in particular a longer time interval during which the motor vehicle actively receives no instruction from the vehicle driver which requires the operation of the fuel cell. An inactive phase of the motor vehicle is, for example, the parking of the motor vehicle, in particular over a longer period. In other words, an inactive phase of the motor vehicle is a phase in which no vehicle component - except the components of the fuel cell system including the cryogenic pressure vessel system - actively requests energy from the fuel cell.

In other words, these are phases in which the fuel cell system could remain switched off with regard to other electrical consumers of the motor vehicle if fuel that was not to be discharged were to be disposed of. In particular, non-driving operating states of the motor vehicle are meant. The motor vehicle disclosed herein further includes a controller configured to operate the device in the inactive state of the motor vehicle. The controller may be configured to activate the device when the pressure in the cryogenic pressure vessel is greater than a blowoff pressure limit. The bleed limit pressure is the pressure at which fuel is to be released from the cryogenic pressure vessel. For example, the blowoff limit pressure may be about 5% or about 10% greater than the maximum operating pressure of the pressure vessel. Especially in the inactive phase of the motor vehicle falls blow-off gas, which is to be blown off. With the device disclosed here, the blow-off gas can be safely mixed with the ambient air on the outer contour, without causing an ignitable mixture. The Device may comprise at least one ambient air pressure accumulator, at least one fan of a cooling system, and / or at least one oxidant conveyor of a fuel cell system. An ambient air pressure accumulator is, for example, in the returning to the applicant German patent application DE 2014 10 2015 209621.1 disclosed, whose content with respect to the compressed gas storage (there reference numeral 20 ) is incorporated by reference into the subject of this patent application. In particular, the fan and the oxidant conveyor are usually already provided in the motor vehicles. If these components generate the ambient air flow, costs, installation space and weight can be reduced. On the aforementioned BMS can then be advantageously dispensed with. Furthermore, it is conceivable that a hydrogen-permeable catalyst layer (for example a perforated layer or a grid) is provided at the openings, in particular at the elastic layer and / or at the membrane. As with a conventional motor vehicle, the catalytic reaction could then take place on the catalyst layer.

The motor vehicle may contain at least one cryogenic pressure vessel ( 100 ) for storing fuel, wherein the fuel-carrying portion is fluidly connected to the cryogenic pressure vessel. The cryogenic pressure vessel may store fuel in the liquid or supercritical state. A supercritical state of aggregation is a thermodynamic state of a substance which has a higher temperature and a higher pressure than the critical point. The critical point denotes the thermodynamic state in which the densities of gas and liquid of the substance coincide, that is, it is single-phase. While one end of the vapor pressure curve in a pT diagram is marked by the triple point, the critical point represents the other end. For hydrogen, the critical point is 33.18 K and 13.0 bar. A cryogenic pressure vessel is particularly suitable for storing the fuel at temperatures significantly below the operating temperature (meaning the temperature range of the vehicle environment in which the vehicle is to be operated) of the motor vehicle, for example at least 50 Kelvin, preferably at least 100 Kelvin or At least 150 Kelvin below the operating temperature of the motor vehicle (usually about -40 ° C to about + 85 ° C). The fuel may be, for example, hydrogen, which is stored at temperatures of about 34 K to 360 K in the cryogenic pressure vessel. The pressure vessel can be used in a motor vehicle which is operated, for example, with compressed natural gas (CNG) or liquefied natural gas (LNG). The cryogenic pressure vessel may in particular comprise an inner container which is designed for max. Operating pressures (MOPs) up to about 350 barü, preferably up to about 500 barü, and particularly preferably up to about 700 barü. The cryogenic pressure vessel preferably comprises a vacuum having an absolute pressure in the range from 10 ^-9 mbar to 10 ^-1 mbar, furthermore preferably from 10 ^-7 mbar to 10 ^-3 mbar and particularly preferably from approximately 10 ^-5 mbar. Storage at temperatures (just) above the critical point has the advantage over storage at temperatures below the critical point that the storage medium is present in a single phase. For example, there is no interface between liquid and gaseous.

The technology disclosed herein further relates to a method for blowing off fuel from a motor vehicle 10 , It includes the step of discharging fuel into the ambient air 1 from a fuel-carrying area 2 of the motor vehicle 10 through at least one outflow opening. A maximum fuel mass flow, with which the fuel can be discharged, may be limited. The maximum fuel mass flow of the at least one outflow opening 3 In particular, it may be below a fuel mass flow limit that can be obtained and / or created by a fuel flame. The method may further include the step of: increasing the flow rate of the ambient air 1 at the at least one outflow opening 3 , in particular during an inactive phase of the motor vehicle. Further, the method disclosed herein may also include method steps disclosed herein in connection with the structural features of the motor vehicle.

In other words, the technology disclosed herein relates to a system that achieves sufficient mixing of the hydrogen with the ambient air. Using gas conveyors to increase the flow rate and the controlled addition of hydrogen in an ideally turbulent flow can also achieve good mixing of much air and little hydrogen. By a large number of Ausströmoffnungen to the ambient air, which may have a sufficient distance from each other, the blow-off can be released into the ambient air, without it comes to exceeding or reaching the Zündfähigkeitsgrenze. The outflow openings may preferably be located on the vehicle outer skin. Preferably, there is in each case a device at the outflow openings, which can exert a valve function and / or can exclude a backflow of air into the hydrogen-carrying region. This is preferably achieved by a rigid outer skin with a correspondingly perforated elastic lower layer. Measures for increasing the rate of air exchange in enclosed spaces (eg garages) are, for example, in the German patent application, which is based on the applicant DE 2014 10 2015 209621.1 disclosed, whose content with respect to the increase in the rate of air exchange is made by reference to the subject of this patent application. Appropriately, a BMS can be made smaller or completely omitted. Advantageously, can be completely dispensed with the relatively expensive catalyst. In combination with the measures to increase the rate of indoor air exchange, the technology disclosed herein enables safer parking in a garage, which avoids the release of explosive mixtures. The air conveyors mentioned above could also be existing fans in the vehicle (for air conditioning, for the fuel cell, etc.), so that the hardware costs are comparatively low.

The technology disclosed herein will now be explained with reference to the figures. Show it:

1 a schematic view of the disclosed here motor vehicle 10 ;

2 a schematic view of the detail A of 1 ;

3 another schematic view of the detail A of 1 ;

4 schematically a perspective view of a plurality of outflow openings 3 ;

5 schematically another view of the disclosed here motor vehicle 10 ; and

6 schematically another view of the disclosed here motor vehicle 10 ,

The 1 shows the motor vehicle disclosed here 10 schematically. In the center tunnel of the motor vehicle here is a cryogenic pressure vessel 100 arranged. The pressure vessel 100 is via a blow-off line 120 with the blow-off chamber 130 connected. Behältertern here is a blow-off valve (ABV) 110 intended. The blow-off valve 110 opens as soon as the inner container pressure of the cryogenic pressure vessel 100 exceeds a blow-off limit pressure. Both the blow-off line 120 as well as the blow-off chamber 130 count here to the fuel-carrying areas 2 of the motor vehicle.

The 2 shows an enlarged view of the detail A, when no fuel through the outflow openings 3 should flow out. For example, during normal operation of the motor vehicle or when the pressure vessel internal pressure is less than the Abblasegrenzdruck. The discharge opening 3 is here formed on or in a vehicle outer contour 31 of the motor vehicle, in particular in the hood. Furthermore, at the outflow openings 3 an elastomeric layer 32 intended. In the elastomeric layer 32 holes or perforations are formed, which are closed in this operating condition and thus the valves closed here 33 form. So the fuel does not come from the fuel-carrying area 2 in the vehicle environment 1 , Other components of the pressure vessel system and the fuel cell system have been omitted for simplicity.

The 3 shows an enlarged view of the detail A, when the fuel through the outflow openings 3 should flow out. In this phase is the blow-off valve 120 open. The result is a pressure difference between the fuel-carrying area 2 , here the blow-off chamber 130 , and the environment 1 , This pressure difference causes the closed holes or perforations, so the valves 33 , open and the fuel through the exhaust ports 3 can escape. The discharge opening 3 is formed here by the elastomeric material and the punch in the hood, which is a rigid outer skin. The outflow openings 3 can be designed such that a maximum fuel mass flow can escape from each of the outflow openings. The maximum fuel mass flow may be below a fuel mass flow limit that can maintain and / or create a fuel flame. In other words, it comes to the increase in pressure on the hydrogen side by the attack of blow-off 2 , then by the pressure difference, the elastic lower layer is deformed so that the outflow openings 3 be given freely. The rigid outer skin supports and stabilizes the lower layer.

The 4 schematically shows a perspective view of a plurality of outflow openings 3 , as in the vehicles of the 1 . 5 and 6 can be installed. The individual outflow openings 3 are each spaced from each other. Every single outflow opening 3 can be limited in their mass flow.

The 5 shows the motor vehicle disclosed here 10 schematically. Alternatively or in addition to the arrangement on the hood, the technology disclosed here can also be arranged in the vehicle roof. For this purpose, for example, the blow-off line 120 be arranged running through a side rail.

Also the 6 shows the motor vehicle disclosed here 10 schematically. Unlike the previous embodiments, here is a device 20 to increase the flow rate of the ambient air 1 shown. The device 20 is here via an ambient air supply line 22 with the blow-off chamber 130 fluidly connected. The blow-off chamber 130 For example, it can not be integrated into the bonnet be and point outward, but be arranged underneath. Thus, the outflow openings 3 protected against weathering and other interventions and, where appropriate, a better aerodynamics can be achieved. In the blow-off chamber 130 here are the outflow openings 3 and / or the valves 33 provided, which may be formed as described above. The blow-off chamber 130 Here is divided into two parts in a fuel-carrying area 2 and an ambient air-conducting area 1 that is above the ambient air supply 22 with the environment 1 connected is. Advantageously, the fuel-ambient air mixture from the blow-off chamber 130 directly or indirectly, in particular siphon-free, into the environment 1 escape.

Instead of a planar configuration of the at least one outflow opening 3 Other forms may be provided. For example, in the blow-off chamber 130 be arranged a jet pump, from which the fuel exits and is surrounded by ambient air. It is also not necessary to provide the at least one valve. The outflow openings 3 may also be provided in a fabric which is suitably waterproof and permeable to fuel. The device 20 to increase the flow rate may also be provided in the embodiments according to the other figures.

The above description and the claims introduce the elements partly in the number. At the same time, however, their plurality should also be included. For example, is the talk of the fuel-carrying area 2 , the device 20 to increase the flow rate, the ambient air supply 22 , the valve 33 , the pressure vessel 100 , the blow-off valve 110 , the blowdown pipe 120 and / or the blow-off chamber 130 , so should at least one fuel-carrying area at the same time 2 that have at least one device 20 to increase the flow rate, the at least one ambient air supply 22 that has at least one valve 33 , the at least one pressure vessel 100 that has at least one blow-off valve 110 that have at least one blow-off line 120 and / or the at least one blow-off chamber 130 to be revealed with.

The foregoing description of the present invention is for illustrative purposes only, and not for the purpose of limiting the invention. Various changes and modifications are possible within the scope of the invention without departing from the scope of the invention and its equivalents.

LIST OF REFERENCE NUMBERS

1

ambient air

2

fuel carrying area

10

motor vehicle

20

contraption

22

Ambient air supply line

31

Vehicle outer contour

32

elastomer

33

Valve

100

pressure vessel

110

Relief valve

120

blow-off line

130

blow-off

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1546601 B1 [0002]
• DE 2014102015209621 [0016, 0019]

Cited non-patent literature

• Butler, M., Axelbaum, R., Moran, C., and Sunderland, P., "Flame Quenching Limits of Hydrogen Leaks," SAE Int. J. Passeng. Cars-Mech. Syst. 1 (1): 605-612, 2009, doi: 10.4271 / 2008-01-0726 [0011]

Claims (13)

Motor vehicle ( 10 ) with several outflow openings ( 3 ), which are formed, fuel from a fuel-carrying area ( 2 ) of the motor vehicle ( 10 ) in the ambient air ( 1 ), the outflow openings ( 3 ) are designed such that a maximum fuel mass flow can escape from each of the outflow openings, wherein the maximum fuel mass flow is below a fuel mass flow limit, which can receive a fuel flame and / or can arise. Motor vehicle according to claim 1, wherein the individual outflow openings ( 3 ) are each spaced apart from each other such that the fuel from adjacent outflow openings ( 3 ) does not form a common fuel flame. Motor vehicle according to claim 1 or 2, wherein the plurality of outflow openings ( 3 ) are formed by at least one hydrogen-permeable membrane. Motor vehicle according to one of the preceding claims, wherein at the outflow openings ( 3 ) Valves ( 33 ) are provided, and wherein the valves ( 32 ) are configured to control the flow of fuel or regulate. Motor vehicle according to claim 4, wherein the valves ( 33 ) as check valves ( 33 ) are formed which a return flow in the fuel-carrying area ( 2 ) stop. Motor vehicle according to one of the preceding claims, wherein the valves ( 33 ) in an elastic layer ( 32 ) are provided, which is formed, the outflow openings ( 3 ) when the pressure in the fuel-carrying area exceeds a limit. Motor vehicle according to one of the preceding claims, wherein the motor vehicle ( 10 ) at least one cryogenic pressure vessel ( 100 ) for storing fuel, and wherein the fuel-carrying area ( 2 ) with the cryogenic pressure vessel ( 100 ) is fluidly connected. Motor vehicle according to one of the preceding claims, wherein the at least one outflow opening ( 3 ) and / or the at least one valve ( 33 ) are provided at least partially on the vehicle outer contour, in particular on the vehicle roof, on a hood, on a boot cover, on a rear spoiler, and / or on a wing. Motor vehicle according to one of the preceding claims, further comprising a device ( 20 ) for increasing the flow rate of the ambient air ( 1 ) at the outflow openings ( 3 ), the device ( 20 ) is designed to increase the flow rate at the outflow openings ( 3 ) during an inactive phase of the motor vehicle to generate the flow of ambient air. Motor vehicle according to one of the preceding claims, wherein the device ( 20 ) comprises at least one ambient air pressure accumulator, at least one fan of a cooling system, and / or at least one oxidant conveyor of a fuel cell system. Motor vehicle according to one of the preceding claims, wherein a control is formed, the device ( 20 ) operate during an inactive phase of the motor vehicle. Motor vehicle according to claim 11, wherein the controller is designed to operate the device ( 20 ) for increasing the flow rate of the ambient air ( 1 ) when the pressure in the cryogenic pressure vessel ( 100 ) is greater than a bleed limit pressure. Method for blowing off fuel from a motor vehicle ( 10 ), comprising the step of: - discharging fuel into the ambient air ( 1 ) from a fuel-carrying area ( 2 ) of the motor vehicle ( 10 ) through several outflow openings ( 3 ), - wherein a maximum fuel mass flow, with which the fuel can be discharged, is limited, and - wherein the maximum fuel mass flow is below a fuel mass flow limit, which can receive a fuel flame and / or can arise.

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