METHOD FOR FILLING A FUEL GAS TANK WITH FUEL GAS, FUEL GAS TANK AND FUEL GAS TANK SYSTEM

Description

[0001] The invention relates to a method for filling a fuel gas tank with fuel gas. The fuel gas can be, for example, hydrogen or natural gas. Such fuel gases are required, for example, by fuel cell vehicles or vehicles with gas engines.

[0002] Furthermore, the invention relates to a fuel gas tank for a fuel gas tank system and a fuel gas tank system with at least one fuel gas tank according to the invention. State of the art

[0003] In vehicles powered by a fuel gas, such as hydrogen, the fuel gas is typically stored under pressure in a fuel gas tank. For hydrogen, the pressure can reach up to 70 MPa. The temperature in the fuel gas tank can rise to 85°C. This temperature limit is generally determined by the material of the fuel gas tank, with carbon fiber reinforced plastic (CFRP) being a common choice. When using CFRP, the plastics used to fix the carbon fibers, particularly the resins, become too soft above 85°C, compromising the required strength of the fuel gas tank.

[0004] Since hydrogen exhibits a negative Joule-Thomson effect in the relevant temperature range, it heats up when refueling a fuel gas or hydrogen tank. To prevent damage to the fuel gas tank, hydrogen is therefore cooled to approximately -40°C before refueling. Furthermore, an upward-angled refueling lance can be used to fill the fuel gas tank, which promotes the mixing of fresh hydrogen with the existing tank contents and thus reduces heating. As a further measure, the tank temperature can be measured and monitored so that the refueling process can be stopped if the temperature limit is exceeded. To ensure that the temperature limit is reliably maintained, the process must be stopped early. High measurement tolerances therefore have a negative impact.Since the determination of the mass stored in the fuel gas tank is usually also based on the tank temperature, high measurement tolerances can further lead to an incorrectly calculated tank level or remaining range.

[0005] For both purposes, it is therefore desirable to obtain the most accurate possible information about the temperature inside a fuel gas tank. However, the locally occurring maximum temperature is crucial for adhering to the temperature limit, while the average temperature is more suitable for calculating the stored mass. Reconciling these two requirements proves difficult. This is especially true since thermocouples, thermistors, or temperature resistors are typically used for temperature measurement, which can only detect the temperature in their immediate vicinity. Furthermore, the limited accessibility of the tank's interior severely restricts the choice of sensor position.

[0006] US Patent 2010 / 0032934 A1 describes, as an example, a fuel gas tank with a tank line and a tank valve for filling the tank with fuel gas, as well as a sensor attached to the tank line for measuring a state variable of the fuel gas. The sensor is positioned so that it lies outside the pressure jet that forms when the fuel gas tank is filled. This is intended to increase the sensor's measurement accuracy.

[0007] DE 10 2015 212979 A1 discloses a method for filling a storage volume of a fuel gas tank with fuel gas, in which the fuel gas is introduced into the storage volume via a refueling path with an integrated tank valve and the temperature of the fuel gas in the area of ​​a stagnation point is recorded with the help of a sensor.

[0008] From US 10 948 087 B2, a tank valve for a pressurized gas container is known, comprising: a base body, wherein the base body comprises a first base body section which, in the installed state, projects into the pressurized gas container and is tightly connected to the pressurized gas container.

[0009] EP 2 757 305 A1 discloses a fuel tank valve comprising: a valve main body with an inlet opening through which a fuel gas is filled into a tank and an outlet opening through which the fuel gas is expelled from the tank.

[0010] In DE 10 2018 121267 A1 a method for operating a motor vehicle with a pressure vessel system is disclosed.

[0011] US Patent 2010 / 206887 A1 discloses a fuel storage system, wherein the fuel storage system comprises a storage vessel with a dielectric lining, and a voltage sensor consisting of a pair of plates arranged on opposite surfaces of the lining.

[0012] WO 2021 / 214701 A1 discloses a multi-function flange valve for a fuel cell automotive system, comprising: a valve body comprising a main section and a mounting section extending from the main section along a mounting axis and terminating with a head surface

[0013] From EP 3 021 031 A1 a high-pressure vessel with a high span of class is known, comprising a tank body including a nozzle, a valve attached to the nozzle and a pipe.

[0014] The present invention is concerned with the objective of ensuring compliance with a predetermined temperature limit when filling a storage volume of a fuel gas tank with fuel gas, in order to avoid overloading the fuel gas tank.

[0015] To solve the problem, the method with the features of claim 1 and the fuel gas tank with the features of claim 5 are proposed. Advantageous embodiments of the invention can be found in the respective dependent claims. Furthermore, a fuel gas tank system with at least one fuel gas tank according to the invention is specified. Disclosure of the invention

[0016] In the proposed method for filling the storage volume of a fuel gas tank with fuel gas, the fuel gas is introduced into the storage volume via a refueling path with an integrated tank valve. The temperature of the fuel gas is measured at a stagnation point, which is formed by the sensor and / or a mounting body that accommodates the sensor, using a sensor integrated into the refueling path.

[0017] Typically, the flow of fuel gas introduced into the storage volume is slowed or dammed by a wall surrounding the volume, resulting in a significant local heating of the fuel gas in the area of ​​the wall. This can lead to local temperature maxima exceeding permissible limits, thus creating a risk of overloading the fuel gas tank. The proposed method, with its artificial stagnation point created within the refueling path, shifts the formation of a local temperature maximum—away from the wall—into the refueling path itself, where it is detected by a sensor. This allows for simpler and more reliable monitoring of compliance with a predefined temperature limit to prevent overloading the fuel gas tank.

[0018] In a further development of the invention, it is proposed that the sensor readings be compared with a predefined temperature limit, and that the refueling process be aborted or interrupted if the temperature limit is exceeded. These additional steps serve to reliably prevent overloading of the fuel gas tank. The predefined temperature limit is preferably even lower than the limit determined by the fuel gas tank material.

[0019] Preferably, the temperature of the fuel gas outside the stagnation point, for example in the storage volume, is measured using an additional sensor, and the mean and / or difference value(s) are determined from the measured values ​​of both sensors. While the sensor located in the stagnation point area records a local temperature maximum or the "total temperature," the additional sensor can be used to measure the "static temperature." This additional sensor is located outside the stagnation point area. By averaging the measured values ​​of both sensors, the mean temperature in the fuel gas tank can be determined, which is needed to calculate the stored mass. Furthermore, by calculating the difference value, the flow velocity of the fuel gas during the filling of the storage volume can be determined. From the flow velocity of the fuel gas, the mass flow rate can then be calculated.The mass of the fuel gas introduced into the storage volume can be calculated.

[0020] As a further training measure, it is therefore proposed that the flow velocity of the fuel gas during a refueling process be derived from the difference value.

[0021] During refueling, the total temperature and the static temperature differ significantly. This means that the difference between the readings of the two sensors is large. During emptying, the opposite is true, provided that the refueling path is not also used for emptying. If the difference is small, or if the readings of both sensors are close, this information can be used to confirm the plausibility of an emptying process.

[0022] If a significantly elevated temperature is detected at the first sensor after refueling, it can be assumed that an uncontrolled "refueling" process is occurring within a multi-tank fuel gas system. This means that fuel gas from another tank is flowing into the tank in question. In this case, the tank valve can be controlled or closed to prevent the predefined temperature limit from being exceeded.

[0023] The first sensor for measuring the total temperature is preferably integrated into the refueling path in such a way that, if the flow direction of the fuel gas in the refueling path reverses, it only measures the static component of the temperature. This means that the first sensor is only directly exposed to the flow in one direction, namely the filling direction. Direct exposure of the sensor in the opposite direction to the filling direction can be prevented, in particular, by the mounting element, which shields the sensor when the flow direction in the refueling path is reversed.

[0024] The ratio of the total temperature to the static temperature depends on the specific geometry and / or the connection of the two sensors. Calibration can reduce any errors in the measurement signals from the two sensors, thus further increasing the measurement accuracy.

[0025] Furthermore, a fuel gas tank for a fuel gas tank system is proposed. The fuel gas tank has a storage volume that can be filled with fuel gas via a refueling path with an integrated tank valve. The fuel gas tank also has a sensor integrated into the refueling path for measuring the temperature of the fuel gas. The sensor and / or a mounting bracket for the sensor form a stagnation point within the refueling path, in the region of which a measuring area of ​​the sensor is located. This means that the temperature of the fuel gas is measured in the region of the stagnation point, so that the total temperature can be determined using the sensor.

[0026] The proposed fuel gas tank can therefore be used to carry out the previously described method according to the invention. The same advantages can thus be achieved with the aid of the fuel gas tank as with the previously described method according to the invention.

[0027] Preferably, the sensor and / or the mounting body have a front surface that is oriented essentially perpendicular to the flow direction of the fuel gas in the refueling path during filling of the storage volume with fuel gas. During filling, the fuel gas is thus stagnated at the front surface, so that the front surface of the sensor and / or the mounting body forms the stagnation point. To measure the temperature of the fuel gas in the region of the stagnation point, the front surface of the sensor preferably also forms the measuring area of ​​the sensor.

[0028] In a further development of the invention, an additional sensor is integrated into the refueling path or storage volume outside the area of ​​the stagnation point. Due to its positioning outside the area of ​​the stagnation point, this additional sensor measures the static temperature in the fuel gas tank. An average and / or differential value can be calculated from the total temperature measured by the first sensor and the static temperature measured by the additional sensor. The average value provides information about the mean temperature in the fuel gas tank, which is required to calculate the stored mass. The differential value allows conclusions to be drawn about the flow velocity of the fuel gas in the filling direction.

[0029] When integrating the additional sensor into the refueling path, it is preferably arranged or oriented such that the fuel gas does not flow directly onto it, but rather the fuel gas is routed past the sensor. This is because, unlike the first sensor, the formation of a stagnation point must be avoided in the area of ​​the additional sensor. For this purpose, the sensor can be arranged essentially parallel to the flow direction of the fuel gas. Alternatively, the additional sensor can be located not only outside the area of ​​the stagnation point, but also outside the refueling path, thus ensuring that the static temperature is given greater consideration.

[0030] Furthermore, it is proposed that the two sensors be connected via the mounting bracket. The mounting bracket thus facilitates the installation of the sensors.

[0031] Preferably, the refueling path is routed, at least in sections, through a pipe projecting into the storage volume. The pipe defines a filling direction. Furthermore, the pipe has a defined flow cross-section, which simplifies the formation of the stagnation point by the first sensor and / or the holding element. For this purpose, the first sensor and / or the holding element are integrated into the pipe, preferably such that a flow surface in the filling direction is oriented perpendicular to the flow direction of the fuel gas.

[0032] Advantageously, the refueling path, the tank valve, and the at least one sensor form a tank unit that is inserted, preferably screwed, into an opening in the end face of a wall enclosing the storage volume, preferably located centrally. All components can be pre-assembled as a tank unit and inserted into the fuel gas tank as a pre-assembled unit, thus simplifying installation and saving space. The tank unit can also accommodate additional components, such as another valve and / or another sensor. Furthermore, the tank unit can have a pipe projecting into the storage volume, through which the refueling path is routed, at least partially, and in particular at its end.

[0033] Furthermore, a fuel gas tank system is proposed, comprising at least one fuel gas tank according to the invention. For example, several identical fuel gas tanks can be connected in parallel arrangements via a common frame. The frame facilitates the installation of the fuel gas tank system in a vehicle, for example, in a fuel cell vehicle.

[0034] Preferred embodiments of the invention are explained in more detail below with reference to the accompanying drawings. These show: Fig. 1 a schematic longitudinal section through a fuel gas tank according to the invention in the area of ​​a tank unit, Fig. 2a)-d) each a schematic longitudinal section through a holding body with two sensors for a fuel gas tank according to the invention, Fig. 3 a schematic longitudinal section through a pipe with integrated holding body and two sensors as well as Fig. 4a schematic longitudinal section through a pipe with integrated holding body and two sensors. Detailed description of the drawings

[0035] The one in Figure 1 The depicted fuel gas tank 1 has a wall 12 enclosing a storage volume 2 and an opening 13 at the front, into which a tank unit 11 is inserted. A refueling path 3 with an integrated tank valve 4 leads via the tank unit 11 for filling the fuel gas tank 1 with fresh fuel gas. An end section of the refueling path 3 is defined by a pipe 10 projecting into the storage volume 2. Since fuel gas, such as hydrogen, heats up considerably when introduced into the storage volume 2, the temperature of the fuel gas is monitored by means of sensors 5 and 6. A first sensor 5 serves to measure the total temperature, and a second sensor 6 to measure the static temperature.

[0036] To measure the total temperature, i.e., a locally occurring maximum temperature, the first sensor 5 is integrated into the pipe 10 in such a way that it lies in the refueling path 3 and is directly exposed to the flow of fuel gas in the filling direction. The fuel gas backs up at a front surface 9 of the sensor 5, which is oriented perpendicular to the flow direction of the fuel gas, so that a stagnation point 7 is formed across this front surface 9. The second sensor 6, for measuring the static temperature, is also integrated into the pipe 10, but oriented in such a way that it is not directly exposed to the flow in the filling direction. This means that no stagnation point is formed by the second sensor 6, and the fuel gas can flow past it unimpeded.

[0037] Of the two sensors 5, 6, at least one sensor 5, 6 can be indirectly attached to the pipe 10 via a mounting bracket 8. This applies in particular to the first sensor 5, since the mounting bracket 8 enables the sensor 5 to be positioned as centrally as possible with respect to the refueling path 3, thus ensuring good airflow to the sensor 5. Depending on the design of the mounting bracket 8, the second sensor 6 can also be integrated into it. Exemplary embodiments are shown in the Figures 2a) to 2d)These figures show that the second sensor 6 is arranged downstream of the first sensor 5 in the direction of fuel gas flow, and at an angle, in particular at right angles, so that the fuel gas can flow past it unimpeded. To optimize the flow in the refueling path 3, the retaining body 8 upstream of the second sensor 6 can have an outer contour that tapers in the filling direction, for example, a conical shape. If the flow direction of the fuel gas in the refueling path 3 reverses, the outer contour of the retaining body 8 also ensures that the fuel gas flows past the first sensor 5, so that it too only measures the static temperature.

[0038] The first sensor 5 is preferably integrated into the holding body 8 such that the flow surface 9 of the sensor 5 simultaneously forms the flow surface 9 of the holding body 8. This can be – as in the Figures 2a) and 2b)shown - just executed. The inflow area 9 can also be according to the Figure 2c) It may be convex or concave (as shown in Figure 3d). Flow optimization can also be achieved via the shape of the inflow surface 9.

[0039] The Figure 3 Another retaining body 8 with a sensor 5 for measuring the total temperature can be removed. The retaining body 8 is integrated into the tube 10 and extends perpendicular to the flow direction 15 of the fuel gas. As the Figure 3As shown, a connecting wire 14 can be guided via the mounting body 8 to the sensor 5 to establish the necessary electrical connection of the sensor 5. The second sensor 6 for measuring the static temperature is integrated inside the pipe 10, so that the flow cross-section is not restricted by the second sensor 6. The fuel gas flow thus bypasses the second sensor 6. The connecting wire 14 of the second sensor 6 is guided to the outside via the mounting body 8.

[0040] The exemplary embodiment of the Figure 4 differs from that of the Figure 3 This is achieved simply by integrating the second sensor 6 externally into the pipe 10, so that the static temperature of the fuel gas in the storage volume 2 is measured using the second sensor 6. The connecting wire 14 is also led outwards through the retaining body 8.

Claims

1. Method for filling a storage volume (2) of a fuel gas tank (1) with fuel gas, in which method the fuel gas is introduced into the storage volume (2) via a fuelling path (3) with an integrated tank valve (4) and the temperature of the fuel gas is detected by means of a sensor (5), characterized in that the sensor (5) is integrated into the fuelling path (3), so that the temperature in the region of a stagnation point (7), which is formed by the sensor (5) and / or a holding body (8) which receives the sensor (5), is detected.

2. Method according to Claim 1, characterized in that the measured values from the sensor (5) are compared with a predefined temperature limit value and, if the temperature limit value is exceeded, the fuelling process is aborted or interrupted.

3. Method according to Claim 1 or 2, characterized in that the temperature of the fuel gas outside the region of the stagnation point (7), for example in the storage volume (2), is detected by means of a further sensor (6) and the mean and / or difference value are / is determined from the measured values from both sensors (5, 6).

4. Method according to Claim 3, characterized in that the flow velocity of the fuel gas is derived from the difference value.

5. Fuel gas tank (1) for a fuel gas tank system, comprising a storage volume (2), which can be filled with fuel gas via a fuelling path (3) having an integrated tank valve (4), further comprising a sensor (5), which is integrated into the fuelling path (3), for detecting the temperature of the fuel gas, characterized in that the sensor (5) and / or a holding body (8) which receives the sensor (5) form / forms a stagnation point (7) in the fuelling path (3), a measurement region of the sensor (5) being arranged in the region of the stagnation point.

6. Fuel gas tank (1) according to Claim 5, characterized in that the sensor (5) and / or the holding body (8) have / has an inflow surface (9) which is oriented substantially perpendicular to the flow direction (15) of the fuel gas in the fuelling path (3) when filling the storage volume (2) with fuel gas.

7. Fuel gas tank (1) according to Claim 5 or 6, characterized in that a further sensor (6) is integrated into the fuelling path (3) or into the storage volume (2), outside the region of the stagnation point (7).

8. Fuel gas tank (1) according to any of Claims 5 to 7, characterized in that the fuelling path (3) is guided at least in sections via a tube (10) which projects into the storage volume (2).

9. Fuel gas tank (1) according to any of Claims 5 to 8, characterized in that the fuelling path (3), the tank valve (4) and the at least one sensor (5, 6) form a tank unit (11), which is inserted, in particular screwed, into a, preferably centrally arranged, end-side opening (13) in a wall (12) enclosing the storage volume (2).

10. Fuel gas tank system, comprising at least one fuel gas tank (1) according to any of Claims 5 to 9.