DE102018209047A1 - Device for temperature pressure relief of a fuel tank - Google Patents

Abstract

A device (20) for the temperature pressure relief of a fuel tank (8, 8a-8d) is described, wherein the device (20) has a heat-conducting line (22, 22a-22d) which can be filled with a gaseous or liquid medium, wherein a first end (24) of the conduit (22) is connectable to a pressure controlled bleed valve (18) disposed in a bleed line (16) for bleeding fuel from the fuel tank (8, 8a-8d), the device (20 ) is designed so that the device (20), when a pressure of the medium in the conduit (20) is greater than a pressure threshold (P_2), the blast valve (18) is pressurized, so that the blow-off valve (18) opens, to empty the fuel from the fuel tank (8, 8a-8d) into the exhaust line (16).

Description

State of the art

It is known in the art that hydrogen-based fuel cells or natural gas-based internal combustion engines are used in vehicles to reduce carbon-based exhaust gases while reducing refueling time compared to battery-powered vehicles. The storage of hydrogen or natural gas (CNG) in the vehicle, however, is a challenge because of the low density of the gas. Associated fuel tanks for the gaseous storage of hydrogen, for example, are usually made of metal and are under a pressure between 350 bar and 700 bar. Also, multiple fuel tanks for hydrogen may be installed in a vehicle, such as buses, to allow for greater range of the vehicle. United Nations Standardization UNECE R No. 134 requires each hydrogen fuel tank to have a "thermally activated relief device (TPRD)" designed to prevent the fuel tank from bursting at high pressure or temperature. This principle is known by the English term "leak before burst". Such a rupture may be caused, for example, by a temperature increase in or near the fuel tank above a predetermined threshold, e.g. B. 105 ° C, arise, which is connected to an increase in pressure in the fuel tank. The fuse is to ensure that a bleed valve in a bleed line connected to the fuel tank opens in time to release the fuel from the fuel tank to prevent a tank explosion. It is also prescribed in Germany by the Technical Inspection Association (TÜV) that a fuse at each extremity of each fuel tank is provided to secure the opposite ends of the usually elongated fuel tanks.

Such fuses typically present high costs to the vehicle and, for example, can not detect fires in a central region of the tank.

There is a need to prevent the bursting of a fuel tank in a simple and inexpensive manner and with high safety.

Disclosure of the invention

According to a first aspect of the invention, there is provided a device for thermally depressurizing a fuel tank, the device comprising a heat conducting conduit capable of being filled with a gaseous or liquid medium, a first end of the conduit having a pressure controlled bleed valve disposed in a bleed conduit of fuel from the fuel tank is arranged, the device being designed so that the device, when a pressure of the medium in the conduit is greater than a pressure threshold value, the blow-off valve is pressurized, so that the blow-off valve opens to the To empty fuel from the fuel tank into the discharge line.

In order to secure a fuel tank, which can be filled with gaseous hydrogen or gaseous natural gas (CNG), for example, against bursting, the device according to the invention can have a, in particular thin, heat-conducting conduit which can be filled with a gaseous or liquid medium. A first end of the conduit may be connected to a pressure controlled bleed valve in an installed state of the device such that when external heat input (for example in a fire) acts on the conduit, a pressure of the medium in the conduit will be greater than a bleed valve pressure threshold will, and the pressure-controlled blow-off valve can open by the pressure. This allows the fuel to escape from the fuel tank into the exhaust line, so that the pressure in the fuel tank may drop again. Consequently, the bursting of the fuel tank can be prevented in a secure manner, since the blow-off valve can respond even in the case of long tanks even if the external heat input can occur far away from a tank extremity. Furthermore, the device can passively, so no power, work, and it must be necessary no additional electrical control of the blow-off valve. Due to the simple construction of the device, this can be realized inexpensively.

In this case, the line may, for example, run along the fuel tank (for example, on the side of the tank, under the tank or above the tank) and / or be either in the fuel tank or outside the fuel tank. Alternatively, for example, the conduit may be disposed adjacent to the battery of a vehicle having the apparatus or adjacent to a vehicle body to promptly trigger the blow-off valve before the fuel tank is allowed to warm. The conduit may also be spaced from the fuel tank so that there is no direct input of heat to the conduit, but the apparatus may still respond in a fire. Further, the line in this case can not lose heat to the fuel tank, so that the temperature increase in the line can be registered faster and the response times of the device can be shorter. It is too it is possible for the duct to be located at a distance from the lowest point of the fuel tank, ie adjacent to the carriageway, so that the effect of heat from below on the duct can be particularly effective.

It is possible that the blow-off valve is attached to one end of the blow-off line, or in other words forms a termination of the blow-off line. Alternatively, the blow-off valve may be provided anywhere along the conduit. The blow-off valve can be arranged in the fuel tank, for example in a tank neck, so that a fracture-proof design can be ensured. It is also possible that the blow-off valve is arranged directly on the fuel tank or in the vicinity of the tank opening.

The line can be made of a thermally conductive material, in particular steel. Alternatively, the line may be made of plastic, if the medium has, for example, a low pressure.

In one embodiment, a second end of the line can be closed pressure-tight, so that a particularly simple implementation of the device can be effected. The unilaterally open line can be connected directly to the blow-off valve. A pressure in the line must, for example, in the normal case, i. without the external heat input, be less than the pressure threshold at which the blow-off valve can open. The pressure threshold can be suitably selected depending on the design of the blow-off valve.

In one embodiment, the device may comprise a plurality of heat-conducting conduits, each of which may be filled with a gaseous or liquid medium and each separately connected to the blow-off valve, and the apparatus may be designed so that the apparatus, when a pressure of the medium in at least one the lines is greater than the pressure threshold value, the blow-off valve is pressurized so that the blow-off valve opens to drain the fuel from the fuel tanks into the blow-off line. In this case, for example, the lines may be connected to a common container, which in turn may be connected to the blow-off valve. In the event of fire, a pressure in the container can correspond to the pressure threshold at which the blow-off valve can open accordingly. It is also possible that the lines are connected via corresponding non-return valves directly or via a common container connected to the check valves with the blow-off valve. In the event of fire, a pressure in the container can correspond to the highest pressure in the lines. In this case, the pressure threshold value may correspond to the opening pressure of each check valve, at the opening of which the pressure on the blow-off valve (in particular for short connecting lines between the check valves and the container and / between the container and the blow-off valve and / or for small volumes of the container) rise to the pressure threshold and the bleed valve can open accordingly. By this measure, an early emptying of all fuel tanks can be made possible even without direct heat to a part of these fuel tanks, so that the fire safety of the tank is improved. The device can also be integrated into the vehicle in a particularly cost-effective manner since only a single blow-off valve and a single device for temperature pressure relief of the fuel tanks can be provided.

In the latter two embodiments, the medium may be gas, for example gaseous hydrogen, or a liquid. The liquid, such as water, can evaporate when exposed to heat and lead to an increase in pressure in the line. Alternatively, such a liquid may be selected which has a sufficiently large thermal diffusion coefficient and an expansion gradient to increase the pressure in the conduit upon thermal expansion of the liquid and initiate the opening of the blow-off valve. Such a liquid may be, for example, mercury.

In one embodiment, the device may further comprise a first valve and a second valve arranged in (in particular different) end regions of the conduit, and the conduit may be filled with the medium by means of the first valve when opened, and by means of of the second valve, when opened, the blowoff valve disposed adjacent to the second valve may be pressurized so that the blowdown valve opens (particularly when the pressure threshold is exceeded) to exhaust the fuel from the fuel tank into the blowdown line. The pressure threshold may be associated with the second valve and correspond to the opening pressure of the second valve and at the same time the opening pressure of the blow-off valve. This measure can cause the line always, ie repeated during operation, for example, during refueling or at a later date, filled with the medium and thus calibrated to a defined amount of medium in the line or to a defined line temperature and a defined line pressure is, so that a safety-related testing requirements with regard to tightness of the line and pressure of the medium in the line, as it may consist in the above-described, unilaterally open line, can be omitted.

The first valve may be located far away from the second valve. For example, both valves can be arranged at opposite ends of the tank, so that a fire can be detected equally at both tank extremities.

In one embodiment, the first end of the conduit to which adjacent or at which the second valve may be disposed is connected to the exhaust line connected to a fuel tank supply between a fuel tank check valve, in particular, a solenoid check valve, and the fuel tank. connectable. One end of the line may indicate an end point of the line. In the case that the second valve is arranged at the end of the line, the second valve can sit directly on the blow-off valve and both valves can be formed together. In this case, the magnetic shut-off valve can enable the medium to enter the tank when the fuel tank is refueled in the de-energized state of the shut-off valve, but the medium can only emerge from the tank when a coil in the magnetic shut-off valve is activated. By means of this measure, the blow-off valve and the second valve (and, depending on the arrangement of the first valve, also first valve) and optionally the shut-off valve can be integrated in a common (valve) housing in a particularly space-saving and cost-effective manner.

The supply for the fuel tank may have a corresponding supply line, which may have a high-pressure fuel line in the region of the shut-off valve.

In an alternative embodiment, the first end of the conduit to which adjacent or at which the second valve may be disposed may be connectable to the blow-off conduit provided downstream of the fuel tank. One direction of the medium flow may be defined in the direction of a supply line to the fuel tank, through the fuel tank and in the direction of the discharge line at a tank outlet. As a result, a limb of the fuel tank can be effectively secured.

In one embodiment, the device may comprise a plurality of second valves, by means of which, when open, a corresponding blow-off valve which can be arranged adjacently to the respective second valve may be pressurized so that the respective blow-off valve opens to remove the fuel from the respective one Fuel tank to empty in the respective discharge line. In this case, only a first valve may be provided in the common line, which opens into one of the exhaust lines and may extend along the fuel tanks due to suitable branches. In this way, a backup of several fuel tanks can be guaranteed at the same time particularly cost, all of which can be emptied simultaneously.

In one embodiment, the conduit may extend along a plurality of fuel tanks, so that with only a first and a second valve, securing of a plurality of fuel tanks and in particular of all tank extremities can be made particularly cost-effective. In this case, only one discharge line with a blow-off valve and / or only one shut-off valve may be provided in a supply line common to all fuel tanks. All valves can then be integrated in a common (valve) housing, provided that the discharge line can branch off from a supply line for the fuel tank between the fuel tank and the shut-off valve.

It is also possible that a plurality of fuel tanks are provided with associated bleed lines and pressure-controlled bleed valves, wherein a separate device is provided per fuel tank, so that the fuel tanks can be emptied individually. Thereby, a cost-effective securing of multiple fuel tanks can be achieved, since each of the devices can be designed uniformly with the same valves and lines.

In one embodiment, a second end of the conduit to which the first valve is located adjacent to the bleed line, which in particular branches from a (fuel) high pressure line between a shut-off valve (for example, a magnetic shut-off valve) for the fuel tank and the fuel tank, or downstream of Fuel tank is provided, or with the fuel tank, or with a fuel-medium pressure line, in particular upstream of the check valve and the fuel high-pressure line, which in turn may be located upstream of the check valve, or with a fuel low-pressure line, in particular upstream of the check valve and the high-pressure fuel line ( and in particular upstream of the fuel-medium pressure line), or connectable to the high-pressure fuel line upstream of the shut-off valve. The fuel high pressure, fuel low pressure and fuel medium pressure lines may be part of the fuel supply line for the fuel tank. In the event that the discharge line between the shut-off valve and the fuel tank, that is arranged in the supply line to the fuel tank, the first and second valve and optionally the shut-off valve and optionally the blow-off valve can be integrated space-saving and cost in a common (valve) housing , In the event that the vent line is located downstream of the fuel tank, can the line is designed to be particularly short. When connecting the line to the fuel medium pressure or the fuel low pressure line, a wall thickness of the line may be thinner than in the connection of the line to the fuel high pressure line, which may contribute to a cost reduction of the device. Further, in these cases, a heat capacity of the line may be lower, so that the device may allow a faster response in case of fire and safer detection of the fire. While the line at a connection of the line to the feed (or the supply line) or the fuel high pressure line during the refueling process can be filled with fuel and calibrated to a pressure and temperature value, the line at a connection of the line with the fuel supply pressure line or the fuel low pressure line after refueling, so during operation for the detection of a fire, be filled with fuel and calibrated to a pressure and temperature value.

The high-pressure fuel line may have a pressure of greater than about 700 bar. The fuel medium pressure line may have a pressure of greater than about 10 bar and less than about 30 bar. The fuel low pressure line may have a pressure of less than about 4 bar.

In one embodiment, a second end of the line, to which the first valve is arranged, can be connectable to a coolant line (in particular a low-pressure refrigerant line), that is to say in a low-pressure region, or an air-low-pressure line, so that media other than hydrogen or CNG are particularly simple for securing the fuel tank, which may be designed in particular as a hydrogen fuel tank, can be used. The line can then have a corresponding low pressure (less than about 3 bar). In these measures, a wall thickness of the line can be made thin, which can contribute to a cost reduction of the device. Furthermore, a heat capacity of the line may be low, so that the device can enable a fast response in case of fire and safe detection of the fire. The conduit may also be made of a low cost material, such as plastic, instead of the steel. The calibration of the lines can for example be done at full load, where the pressure is usually highest. The use of low pressure in the line can increase safety of the device. Further, use of air or coolant may provide design flexibility of the device.

The connection of the second end of the line to the low-pressure air line, in particular, in the flow direction of the air, downstream of a heat exchange, which may be provided in the air circuit, be provided, since the air can then be tempered.

In one embodiment, the first valve and the second valve may be formed as a check valve, so that a particularly cost-effective implementation of the device may be possible. For example, a first pressure threshold at which the first check valve can open must be smaller than a second pressure threshold at which the second check valve can open.

In the case of connecting the line to the high-pressure fuel line, the first pressure threshold may be about 850 bar and the second pressure threshold may be about 970 bar. In the case of connection of the line with the fuel medium pressure line, the first pressure threshold value may also be about 20 bar and the second pressure threshold value about 23 bar. In the case of the connection of the line to the fuel low pressure line, the first pressure threshold can be about 3.7 bar and the second pressure threshold about 4.7 bar, so that inexpensive low-pressure check valves can be used. If the medium is air, the first pressure threshold may be 3.0 bar and the second pressure threshold may be 3.2 bar. If the medium is coolant, the first pressure threshold may be 2.5 bar and the second pressure threshold may be 2.9 bar.

In an alternative embodiment, the first valve may be designed as a shut-off valve, in particular as a magnetic shut-off valve, and the second valve as a non-return valve. This measure has the advantage that the pressure in the line does not have to be higher than the normal system pressure of the medium. This measure can be combined in particular with the connection of the line to the low-pressure air line. It is also possible that this measure is applicable to devices that are based on other medium than air, so for example, fuel or coolant. This measure can also represent a cost-effective implementation of the device, since a low-pressure check valve is used.

In an embodiment, a temperature of the medium to be filled in the conduit may be adaptable. This measure can be provided in particular for a medium in the form of air or coolant.

According to a second aspect, there is provided a hydrogen fuel cell system including the apparatus according to the first aspect and a hydrogen tank.

According to a third aspect, a vehicle is provided that includes a fuel tank and the Device according to the first aspect. The fuel tank may be a hydrogen tank, and optionally, the vehicle may include the hydrogen fuel cell system according to the second aspect. Alternatively, the fuel tank may be a CNG tank.

According to a fourth aspect, there is provided a method of calibrating the apparatus (particularly active) according to the first aspect, the method comprising the steps of adjusting (in particular increasing) a pressure to calibrate the conduit and opening and closing the first valve while the second valve closed is. Thereby, the pressure in the line can be adjusted by a prevailing system pressure can also be present in the line after opening the first valve. The suitable control of the first valve can be carried out actively in the case of the first valve designed as a shut-off valve.

In an embodiment, the method further comprises the step of (actively) adjusting a temperature of the medium. As a result, the medium can be brought to the appropriate temperature, in particular if the calibration temperature of the medium is incorrect, so that the calibration can nevertheless be carried out. The temperature setting may be, for example, a temperature increase and / or it may be performed prior to pressure adjustment.

list of figures

• 1 schematisch ein Fahrzeug mit einem Brennstoffzellensystem und einer Vorrichtung zur Temperaturdruckentlastung eines Wasserstofftanks;
• 2 bis 9 schematisch Ausführungsbeispiele der Vorrichtung in 1;
• 10 schematisch einen Druckverlauf während eines Betankungsvorgang und einen Brands im Betrieb der Vorrichtung in 4 bis 9;
• 11 bis 16 schematisch weitere Ausführungsbeispiel der Vorrichtung in 1; und
• 17 schematisch ein Ablauf eines Verfahrens zum Kalibrieren der Vorrichtung in 13 bis 15 und insbesondere zur Anpassung einer Temperatur des Mediums in der Vorrichtung in 13 bis 15.

Preferred embodiments of the present invention will be explained in more detail with reference to the accompanying drawings. Show it:

• 1 schematically a vehicle with a fuel cell system and a device for temperature pressure relief of a hydrogen tank;
• 2 to 9 schematically embodiments of the device in 1 ;
• 10 schematically a pressure curve during a refueling operation and a fire in the operation of the device in 4 to 9 ;
• 11 to 16 schematically another embodiment of the device in 1 ; and
• 17 schematically a flow of a method for calibrating the device in 13 to 15 and in particular for adjusting a temperature of the medium in the device in 13 to 15 ,

Embodiments of the invention

The same or similar components or elements are provided with the same reference numerals.

In 1 is a vehicle 2 represented by means of a fuel cell system 4 is operable. One or more fuel cells 6 is hydrogen from a fuel tank designed as a hydrogen tank 8th of the fuel cell system 4 fed. The fuel cells 6 generate energy by means of a line electronics 10 for driving an engine 12 is usable. The fuel tank 8th has a high-pressure supply line 14 and a blow-off line 16 on, in which a pressure-controlled blow-off valve 18 is arranged. To a bursting of the fuel tank 8th For example, in the case of a fire near the fuel tank 8th to prevent is a schematically illustrated as a block device 20 for temperature pressure relief of the hydrogen tank 8th intended.

In an in 2 in side view (upper figure) and in plan view from below (lower figure) shown, the first embodiment of the device 20a - 20d this has a heat-conducting line 22a - 22d which can be filled with a gaseous or liquid medium. This medium can be, for example, hydrogen, air or a liquid. A first end 24a - 24d the line 22a - 22d is over the blow-off valve 18a - 18d with the discharge line 16a - 16d connected. A second end 25a - 25d the line 22a - 22d is hermetically sealed. The administration 22a - 22d extends along the entire length of the fuel tank 8a - 8d adjacent to a roadway floor at an underside of a truck-mounted vehicle 2 , Unless the vehicle 2 as shown, several fuel tanks 8a - 8d Each of these fuel tanks is 8a - 8d with a same device 20a - 20d fitted.

In a second embodiment of the device 20 , in the 3 is shown in plan view from below, the device 20 for several fuel tanks 8a - 8d provided and points per fuel tank 8a - 8d a line 22a - 22d on, each in a common container 28 open, via the blow-off valve 18 with the discharge line 16 connected is. Each of the lines 22a - 22d extends along the entire length of the associated fuel tank 8a - 8d ,

In a company of in 2 . 3 shown device 20 the medium expands in the pipe 22 when a heat input, for example in the form of a fire, the line 22 heated. This increases the pressure in the pipe 22 to above a pressure threshold, which is about 870 bar, and the blow-off valve 18 This pressure of 870 bar is applied. In case of 3 increases the pressure in the container 28 also above the pressure threshold until the blow-off valve 18 opens. This opens the blow-off valve 18 and in the fuel tank 8th stored hydrogen escapes via the blow-off line 16 ,

At the in 4 shown third embodiment of the device 20 is a first end 24 a thermally conductive and filled with hydrogen line 22 with a blow-off valve 18 in a discharge line 16 connected and a second end 25 the line 22 is upstream of the blow-off valve 18 with the discharge line 16 connected, coming from a tanker end 30 of the fuel tank 8th exit. A magnetic shut-off valve 32 seals a high pressure line 34 that are part of the feed line 14 is, from another tanker end 36 that the tanker end 30 opposite, from. The administration 22 is U-shaped, but may also have a different shape. The administration 22 has a first check valve 38 on that in an end area 40 the line 22 is arranged, in the discharge line 16 upstream of the blow-off valve 18 empties. A second check valve 44 is in a second end area 46 the line 22 arranged with the blow-off valve 18 connected is.

At an in 5 shown fourth embodiment of the device 20 enters a heat-conducting line 22 from a tanker end 30 out, that of the high pressure line 34 opposite, and extends along the entire length of the fuel tank 8th back to a tanker end 36 , This can cause a fire along the tank 8th be detected. An L-shaped branch of the pipe 22 flows through a shut-off valve 18 in a discharge line 16 , The blow-off line 16 is between a magnetic shut-off valve 32 in the high pressure line 34 and the tanker end 36 arranged. A first check valve 38 is at one end 25 the line 22 and sits right at the end of the tank 30 on. A second check valve 44 is in an end area 46 the line 22 adjacent to the shut-off valve 18 arranged. The administration 22 each has bends of 90 degrees, so that the device 20 is designed to be particularly compact. The administration 22 can also be bent at other angles. The administration 22 for example, below the tank 8th be arranged in the direction of the roadway. The magnetic shut-off valve 32 , the second check valve 44 and the blow-off valve 18 can be integrated in a common valve housing.

An in 6 shown fifth embodiment of the device 20 is similar to the device 20 in 5 educated. However, a line flows 22 in the discharge line 16 upstream of the blow-off valve 18 and is not with a tanker end 30 connected. The first check valve 38 is adjacent to the mouth of the pipe 22 in the discharge line 16 intended. The first check valve 38 can also be related to that 5 be integrated valve housing described.

In 7 are a plurality of fuel tanks 8th shown, each with a device 20 that like the device 20 in 6 are formed, are provided. The summary is just a device 20 and only one tank 8th provided with reference numerals. Each of the fuel tanks 8a - 8c is emptied separately in case of fire. The valves 38 . 44 and the wires 22 are each formed the same, so that the devices 20 thus produced inexpensively.

At the in 8th shown sixth embodiment of the device 20 is for every fuel tank 8a - 8c a blow-off line 16a - 16c provided between a magnetic shut-off valve 32a - 32c and a tanker end 36a - 36c from the high pressure line 34a - 34c branches. A single line 22 is formed lattice-shaped and extends along the entire length of all fuel tanks 8a - 8c , The administration 22 is with an end 25 with the discharge line 16a a first fuel tank 8th connected. More ends 24a - 24c the line 22 are each with a blow-off valve 18a - 18c in the associated discharge line 16a -16c connected. A first check valve 38 is in an end area 40 the line 22 adjacent a mouth of the conduit 22 in the discharge line 16a intended. Per fuel tank 8a - 8c is in each case a second check valve 44a - 44c provided in end areas 46a - 46c the line 22 adjacent to the respective associated bleed valve 18a - 18c seconded.

In an in 9 shown seventh embodiment of the device 20 is everyone from fuel tanks 8a - 8c with a common high pressure supply line 34 connected via a single solenoid shut-off valve 32 are fillable. A line 22 branches off the high pressure line 34 adjacent to a tanker end 36 one of the tanks 8a - 8c and flows into a discharge line 16 that also comes from the high pressure line 34 between the magnetic shut-off valve 18 and the tanker end 36 branches. The administration 22 is branched and extends along each fuel tank 8a - 8c and connects them together. A second end 24 the line 22 is with the blow off valve 18 connected in the discharge line 16 is provided, which from the Hochdruckzuführleitung 34 downstream of the solenoid shut-off valve 32 branches. A first check valve 38 is adjacent to the tanker end 36 in the pipe 22 arranged. A second check valve 44 sits adjacent to the blow-off valve 18 in one end area 46 the line 22 , The first check valve 38 may instead of adjacent to the tank end 36 adjacent to the diversion of the discharge line 16 from the feed 34 be provided so that then all the valves 18 . 32 . 38 . 44 can be integrated in a valve housing.

At the in 4 to 9 shown embodiments, the pressure threshold P_1, that is, the opening pressure, for the first check valve 38 850 bar and the pressure threshold P_2, ie the opening pressure, for the second check valve 44 about 970 bar.

10 represents the time course of the pressure P as a function of a time t during a refueling operation (upper diagram) and a fire (lower diagram) for the in 4 to 9 shown embodiments of the device 20 During refueling, the hydrogen heats up to 85 ° C due to its expansion, and in the refueling process becomes the shut-off valve 32 suppressed and regulated by the gas station so that the hydrogen pressure P in the fuel tank 8th rises to about 870 bar. Curve B shows schematically the refueling time. The pressure of 870 bar corresponds to a pressure of 700 bar at 20 ° C, which sets after cooling the tank contents. Will the pressure threshold P_1 of the first check valve 38 reached, which is at 850 bar, opens the first check valve 38 so the line 22 between the check valve 38 and the second check valve 44 is filled with hydrogen. A curve RS1 shows schematically the opening and closing behavior of the check valve 38 , Here is the second check valve 44 closed, its pressure wave value P_2 for opening is greater than 870 bar. This will increase the amount of hydrogen in the line 22 between the two check valves 38 . 44 compressed to the high pressure. During the cooling of the tank contents and the corresponding reduction of the pressure P_1 becomes the first check valve 38 closed. The temperature T in the pipe 22 when closing the first check valve 38 then equalizes the tank temperature at this closing pressure P_1 , which can be calculated from the ideal gas equation, since the pressure of the filled fuel tank at 20 ° C, as described above, is 70 MPa: $$293.15\text{K / 70 MPa}=\text{T / P\_1}=\text{V /}\left(\text{No}\right),$$

For a pressure threshold P_1 of 850 bar, the temperature T is thus 82.8 ° C according to the ideal gas equation. The first check valve 38 thus ensures that the pressure in the pipe 22 always calibrated to this value.

The administration 22 also encloses a known amount of gas. An external refill of the line 22 is not necessary because any leakages can be refilled during refueling. The amount of hydrogen in the pipe 22 can be calculated from the line volume, the pressure threshold P_1 of the first check valve 38 as well as calculate the above temperature T, and is a constant size.

The pressure threshold P_2 of the second check valve 44 can be calculated in a similar way. Should the second check valve 44 at z. B. at 105 ° C, which corresponds to the known release temperature for fuses for hydrogen tanks, the pressure threshold P_2 = 969 bar.

As in the lower diagram of 10 As shown, the pressure P in the pipe varies 22 between the first check valve 38 and the second check valve 44 in normal operation according to the ambient temperature, z. B. between 580 bar (for -30 ° C) and 830 bar (for 50 ° C). In a fire, the line heats up 22 and the hydrogen in it so on, that the pressure threshold P_2 of the second check valve 44 is exceeded and the second check valve 44 opens. A curve RS2 shows the opening and closing behavior of the check valve 44 , The blow-off valve 18 stays open until the pressure in the thin pipe 22 the pressure threshold P_2 again falls below, ie until the temperature of the line 22 decreases. This occurs only when the fire has been extinguished, and the fuel tank 8th has cooled.

In one operation of the device 22 opens the first check valve 38 during a refueling operation of the fuel tank 8th due to the rising temperature, while the second check valve 44 closed is. That way, the line becomes 22 filled with a constant known amount of hydrogen. Thereafter, the first check valve 38 closed due to falling temperature during or after refueling. At a later time, the pressure in the thin pipe increases 22 by a local heat input, z. B. by a fire. The local heat input can z. B. be greater than 85 ° C above 850 bar addition. The second check valve 44 has a pressure threshold P_2 greater than 900 bar, here about 970 bar, on. Only when a temperature in the pipe 22 greater than 100 ° C (eg 105 ° C), the second check valve becomes 44 triggered by the pressure, the blow-off valve 18 opened and the fuel tank 8th is in the direction of blow-off 16 open. The hydrogen can pass through the blow-off line 16 from the fuel tank 8th escape.

11 shows an eighth embodiment of the device 20 that a fuel cell system 4 assigned. The device 20 is similar to the device 20 in 4 trained, however is a second end 25 a line 22 with a hydrogen medium pressure line 50 connected. This is in the fuel cell system 4 between a hydrogen injector 52 and a pressure reducer 54 arranged, in turn, by means of the high pressure line 34 with the magnetic shut-off valve 32 connected is. The administration 50 is also part of the supply line 14 , The pressure in the pipe 22 is in the range of 20 bar. The pressure threshold of the first check valve 38 and the second check valve 44 must be similar to in 4 to 9 are selected according to the refueling pressures and are 20 or 23 bar. An operation of the device 20 is similar to the operation of the devices 20 in 4 to 9 , However, the calibration process of the line takes place 22 unlike the embodiments in 4 to 9 not during refueling, but only after refueling instead, as the tank shut-off valve 32 only in normal operation is opened.

$$\mathrm{293,15}\text{/0}\text{,37 MPa}=\text{T\_Ablassen/P\_2}\text{, also }$$

$$\text{P\_}2=\mathrm{0,47}\text{ MPa}.$$

This in 12 shown ninth embodiment of the device 20 is similar to the device 20 in 11 educated, but there is an end 25 a line 20 in which a first check valve 38 is provided with a hydrogen low pressure line 56 connected between the fuel cells 6 and a hydrogen injector 52 is provided. The administration 56 is also part of the supply line 14 , The administration 20 and the valves 38 . 44 are exposed to a pressure much less than 5 bar. The first check valve 38 has a pressure threshold P_1 of 3.7 bar and serves the pipe 20 between the first check valve 38 and the second check valve 44 to fill with hydrogen, thereby the pipe 22 to calibrate. This contains the line 20 a known amount of gas. External refilling is not required, as any leaks will be replenished during operation. The pressure P_1 is selected above the maximum operating pressure of 3.5 bar, so that the valve 38 only for filling the line 22 opens. This pressure is achieved only during a calibration process. The second check valve 44 has a pressure threshold P_2 of 4.7 bar, using the ideal gas equation for a calibration temperature T = 20 ° C of the first check valve 38 upon triggering of the second check valve 44 at a temperature T_Blow greater than 105 ° C can be calculated at the opening of the blow-off valve 18 to be achieved: $$\text{T / P\_1}=\text{T\_Ablassen / P\_2}=\text{V /}\left(\text{NO}\right)$$

$$293.15\text{/ 0}\text{, 37 MPa}=\text{T\_Ablassen / P\_2}\text{, so}$$

$$\text{P\_}2=0.47\text{MPa},$$

This in 13 The tenth embodiment shown is similar to the embodiment in FIG 12 educated, but there is an end 25 a line 22 with a coolant line 58 connected. The pressure of the coolant and thus in the pipe 22 is 2.5 bar. At a calibration temperature of T = 50 ° C = 323.15K and a blow-off temperature T_Blow = 105 ° C = 378.15K, the pressure threshold values are P_1 = 2.5 bar and P_2 = 2.9 bar.

This in 14 shown eleventh embodiment of the device 20 is similar to the device in 13 educated, but the end is 25 the line 22 with an air-low pressure line 60 , in particular downstream of a heat exchanger 61 , connected, in an air circulation 62 is provided. The pressure level in the low pressure air line 60 and thus in the line 22 is about 3 bar. As in 15 can be shown in the too 14 similar embodiment in place of the first check valve 38 a shut-off valve 64 be provided. At a calibration temperature of T = 80 ° C = 353.15K and a blow-off temperature T_Blow = 105 ° C = 378.15K, the pressure threshold values are P_1 = 3 bar and P_2 = 3.2 bar.

The calculation of the pressure P_2 for the in 13 to 15 The embodiment shown is analogous to that in 12 shown embodiment.

In the 16 shown device 20 according to a twelfth embodiment is similar to the device 20 in 12 trained, however, the line extends 22 along the entire tank length and under the tank 8th , so that the line 22 is L-shaped. The check valve 44 and the blow-off valve 18 can be accommodated in a common valve housing.

An operation of the device 20 in 12 to 16 is similar to the operation of the devices in 4 to 9 , The calibration process, however, varies, and must be implemented regularly during operation, e.g. B. once per trip, and he is actively triggered. If the calibration process is started during normal operation, the temperature of the corresponding medium in the line 22 aligned with the calibration range, z. 20 ° C for hydrogen, 80 ° C for air, and 50 ° C for the coolant. If the temperature is within the allowable range, eg. B. plus / minus 1 Kelvin difference, the pressure is above the pressure threshold P_1 of the first check valve 38 elevated. For hydrogen, it is easy to control a control valve of the hydrogen injector 52 , In the case of air must air compressor 65 and optionally an air throttle are controlled accordingly, and in the case of the coolant, the coolant pump 66 be controlled accordingly. Will the pressure threshold P_1 of the first check valve 38 exceeded or is the shut-off valve 64 in 15 (where the pressure P_1 of eg 3 bar was set) opened, the line becomes 22 filled with the compressed medium, and the calibration process is completed. The first check valve 38 or the shut-off valve 64 will be closed again.

In case the temperature of the medium is not suitable for the calibration and it can be changed, it will be adjusted accordingly before the filling of the pipe 22 customized. 17 shows a corresponding method for calibrating the device 20 and in particular for adjusting the temperature of the medium in the conduit 22 , In a first step S1 will be the calibration of the pressure in the line 22 started. In a next step S2 it is determined if the temperature is within the desired temperature range. If not, will be in one step S3 determines if the temperature can be changed. If this is the case, it will be in one step S4 the medium temperature increases and the process branches back to the step S2 , Is a result of the decision in the step S3 negative, the process ends with the step S5 , Is a result of the decision in the step S2 positive, in one step S6 the pressure in the pipe 22 in the case of the first check valve 38 increased above the normal medium pressure or in the case of the shut-off valve 64 will be the desired pressure in the line 22 adjusted by the medium pressure. Is the pressure in the case of the first check valve P_1 is exceeded, in one step S7 the first check valve 38 in 11 to 14 and 16 opened and closed again when the pressure is below the pressure threshold P_1 decreases. In the case of the shut-off valve 64 in 15 is in the step S7 the shut-off valve 64 opened for a predetermined time (eg 0.5 s) and later closed again when the predetermined time has elapsed. Thereafter, the process ends with the step S5 ,

The positive result of the decision in the step S3 in that the temperature of the medium can be changed, is in particular the case for the coolant. The temperature of the air can also be adjusted by varying the compression within certain limits. The temperature of the hydrogen corresponds to the tank temperature and can not be influenced during normal operation. In other words, the decision is in step S3 negative. However, in order to run the calibration process at a temperature other than 20 ° C, the temperature of the hydrogen is selected to be about 50 ° C, which is reached after each refueling, since the hydrogen temperature in the fuel tank during refueling to about 85 ° C. increases, so the calibration process in the cooling phase of the fuel tank 8th takes place (see 10 , upper diagram). If the cooling without operation of the fuel cell system 4 takes place, the calibration phase takes place only after the next refueling during operation of the fuel cell system 2 instead of.

In the step S6 For example, the pressure may be increased by the pressure in the system reaching at least the first pressure threshold P_1 is actively increased. After switching the first valve 38 or the shut-off valve 64 If necessary, the pressure can again drop slightly, so that the pressure can then be actively readjusted to at least the first pressure threshold value. The pressure in the pipe 22 then can the first pressure threshold P_1 to reach. The step S6 So at least partially parallel to the step S7 be performed.

Claims (14)

Device (20) for the temperature pressure relief of a fuel tank (8, 8a-8d), wherein the device (20) has a heat-conducting conduit (22, 22a-22d) which can be filled with a gaseous or liquid medium, wherein a first end (24 ) of the conduit (22) is connectable to a pressure-controlled bleed valve (18) disposed in a bleed line (16) for bleeding fuel from the fuel tank (8, 8a-8d), the device (20) being so configured in that, when a pressure of the medium in the conduit (20) is greater than a pressure threshold (P_2), the device (20) pressurizes the blow-off valve (18) so that the blow-off valve (18) opens to expel the fuel the fuel tank (8, 8a-8d) in the discharge line (16) to empty. Device (20) according to Claim 1 , wherein a second end (25) of the conduit (22) is pressure-tight manner. Device (20) according to any preceding claim, wherein the device (20) comprises a plurality of heat-conducting lines (22a-22d), each of which can be filled with a gaseous or liquid medium and each separately connected to the blow-off valve (18), wherein the device ( 20) is designed so that the device (20), when a pressure of the medium in at least one of the lines (22a-22d) is greater than the pressure threshold (P_2), the blow-off valve (18) pressurized, so that the blow-off valve (18) opens to drain the fuel from the lines (22a-22d) associated fuel tanks (8a-8d) in the discharge line (16). Device (20) according to Claim 1 wherein the device (20) further comprises a first valve (38, 64) and second valve (44) disposed in end portions (40, 46) of the conduit (22), the conduit (22) being defined by the first valve (38, 64), if it is open, can be filled with the medium and wherein by means of the second valve (44), when it is open, the adjacent to the second valve (44) can be arranged pressureable blow-off valve (18), so that the blow-off valve (18) opens to empty the fuel from the fuel tank (8) into the exhaust line (16). Device (20) according to Claim 4 wherein the first end (24) of the conduit (22) to which adjacent or to which the second valve (44) is disposed is connected to the bleed line (16) connected to a feed line (34) for the fuel tank (8) a shut-off valve (32) of the fuel tank (8) and the fuel tank (8) is connected, is connectable. Device (20) according to Claim 4 wherein the first end (24) of the conduit (22) to which adjacent or to which the second valve (44) is disposed is connectable to the blow-off conduit (16) provided downstream of the fuel tank (8). Device (20) according to one of Claims 4 to 6 wherein the device (20) comprises a plurality of second valves (44a-44c) by means of which, when open, a corresponding adjacent to the respective second valve (44a-44c) can be arranged blow-off valve (18a-18c) is pressurized such that the respective blow-off valve (18a-18c) opens to empty the fuel from the respective associated fuel tank (8a-8c) into the respective blow-off line (16a-16c). Device (20) according to one of Claims 4 to 6 wherein the conduit (22) extends along a plurality of fuel tanks (8a-8c). Device (20) according to one of Claims 4 to 8th wherein a second end (25) of the conduit to which the first valve (38, 64) is arranged, - the blow-off conduit (16), - the fuel tank (8), - a fuel-medium pressure conduit (50), - with a fuel low pressure line (56) or - with a high-pressure fuel line (50) upstream of a shut-off valve (32) for the fuel tank (8) is connectable. Device (20) according to one of Claims 4 to 8th wherein a second end (25) of the conduit (22) to which the first valve (38, 64) is adjacent is connectable to a coolant conduit (58) or an air low pressure conduit (60). Device (20) according to one of Claims 4 to 10 wherein the first valve (38) and the second valve (44) are designed as a check valve. Device (20) according to Claim 4 to 8th and 10 , wherein the first valve (64) as a shut-off valve and the second valve (44) are designed as a check valve. Method for calibrating a device (20) according to one of Claims 9 to 12 , comprising the steps of: - setting (S6) a pressure to calibrate the line 22 and - opening (S7) and closing the first valve (38, 64) while the second valve (44) is closed. Method according to Claim 13 , further comprising the step of: - adjusting (S4) a temperature of the medium.

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