Method and control device for operating a fuel gas tank system

Abstract

The present invention relates to a method for operating a fuel gas tank system (1) including at least one fuel gas tank (2) for storing fuel gas under high pressure and a valve module (3) inserted in the fuel gas tank (2) for extracting fuel gas from the fuel gas tank (2), wherein a shut-off valve (4) integrated into an extracting line (6) of the valve module (3) communicating with a gas pipe (7) downstream of a flow restriction valve (5) in the extracting direction is controlled and opened to extract the fuel gas. According to the present invention, before controlling the shut-off valve (4), a check is made in step (a) as to whether activation of the flow restriction valve (5) is expected. If activation of the flow restriction valve (5) is expected, the shut-off valve (4) is controlled multiple times in succession at specific time intervals in step (b). The present invention also relates to a control device for executing each step of the method.

Description

[Technical Field]

[0001] The present invention relates to a method of operating a fuel gas tank system that includes at least one fuel gas tank for storing fuel gas under high pressure and a valve module inserted into the fuel gas tank for withdrawing fuel gas from the fuel gas tank. Additionally, the present invention relates to a control device for the fuel gas tank system.

[0002] A preferred field of application is mobile fuel gas tank systems, in particular fuel cell vehicles and / or gas vehicles, powered by fuel gas, which may in particular be hydrogen or natural gas stored under high pressure in a fuel gas tank. [Background technology]

[0003] Mobile fuel gas tank systems are known that have at least one fuel gas tank for storing a fuel gas, such as hydrogen or natural gas. The fuel gas tank is typically designed as a high-pressure tank. A shut-off valve is always required to hermetically shut off the tank when the vehicle is not in operation. For safety reasons, the shut-off valve is typically constructed as a normally closed valve. For additional safety reasons, the shut-off valve may be preceded by a flow-limiting valve that significantly throttles the flow rate in the event of a fault, thus allowing for a controlled release of fuel gas from the fuel gas tank.

[0004] The shut-off valve and the flow limiting valve are usually integrated into a valve module, which can be inserted as a compact unit into the fuel gas tank, in particular in the region of the neck of the fuel gas tank. The valve module is integrated into an outlet line that communicates with the gas pipe. In addition to the shut-off valve and the flow limiting valve, other components, in particular other valves, are usually also integrated into the outlet line.

[0005] The pressure loss when drawing fuel gas from the fuel gas tank increases with the number of components in the drawing path. Accordingly, the pressure threshold for activating the flow restriction valve, hereinafter referred to as the activation threshold, must be selected to be lower than the pressure difference across the entire valve module. This increases the risk of the flow restriction valve being inadvertently activated and restricting the flow through an open shut-off valve when controlling the shut-off valve. This risk arises particularly when a pressure increase occurs in the fuel gas tank and / or a pressure decrease occurs in the gas line, resulting in a particularly large difference between the pressure in the fuel gas tank and the pressure in the gas line. Activation of the flow restriction valve restricts the flow, making it impossible to draw the required amount of fuel gas from the fuel gas tank. In a fuel gas tank system with multiple fuel gas tanks, this can result in an insufficient amount being drawn from a fuel gas tank where activation of the flow restriction valve is least expected. This can result in uneven emptying of multiple fuel gas tanks. Summary of the Invention [Problem to be solved by the invention]

[0006] The problem addressed by the present invention is to prevent flow restriction due to an activated flow restriction valve when fuel gas is drawn off from a fuel gas tank, or at least to mitigate the undesirable consequences of such flow restriction. To solve this problem, a method is proposed having the features of claim 1. Preferred developments of the invention can be read from the dependent claims. Furthermore, a control device for carrying out the steps of the method according to the invention is described. [Means for solving the problem]

[0007] A method for operating a fuel gas tank system including at least one fuel gas tank for storing fuel gas under high pressure and a valve module inserted into the fuel gas tank for extracting fuel gas from the fuel gas tank is proposed. In this method, a shut-off valve integrated into an extracting path of the valve module communicating with a gas pipe downstream of a flow restriction valve as seen in the extracting direction is controlled and opened to extract the fuel gas. According to the invention, before controlling the shut-off valve, in step (a), it is checked whether activation of the flow restriction valve is expected. If activation of the flow restriction valve is expected, in step (b), the shut-off valve is controlled multiple times in succession at specific time intervals.

[0008] By controlling the shut-off valve multiple times, the shut-off valve is opened multiple times in succession. Between the two opening stages, the shut-off valve is closed, so that no fuel gas is drawn off from the fuel gas tank. This means that between the two opening stages, a large flow rate is blocked by the flow restriction valve and, therefore, by its activation. The flow restriction valve then opens again, so that the shut-off valve can be controlled or opened again to draw off the fuel gas. If the flow restriction valve is activated again, the control of the shut-off valve is again interrupted until the activation of the flow restriction valve is over and the drawing off of fuel gas from the fuel gas tank can continue.

[0009] The proposed control strategy prevents flow restriction due to unintentional activation of the flow restriction valve. If the flow restriction valve has already been activated, the proposed control strategy can quickly eliminate the flow restriction again, so that fuel gas can be drawn from the fuel gas tank even under unfavorable pressure conditions. In this way, in mobile fuel gas tank systems, system availability and therefore the full driving range of the vehicle are restored. In fuel gas tank systems with multiple fuel gas tanks, the proposed control strategy can prevent the fuel gas tanks from emptying unevenly.

[0010] The proposed control strategy reduces the requirements on the valve module inserted into the fuel gas tank, thus simplifying the design of the valve module accordingly.

[0011] For the check in step (a), the latest pressure of the fuel gas tank and / or the latest pressure of the gas line are preferably detected by a sensor. By referring to the latest pressure of the fuel gas tank or the latest pressure of the gas line, it is possible to already estimate whether or not the flow limiting valve is to be activated in a particular case.

[0012] This may occur, for example, if the fuel tank is exposed to sunlight for a relatively long period of time while the vehicle is stationary, resulting in a significant increase in pressure in the fuel tank due to heating. This pressure increase can be detected by a sensor and, if necessary, compared with the maximum pressure reached in normal cases. A significantly higher value indicates that activation of the flow limiter under the control of the shut-off valve is to be expected, even without knowledge of the current pressure in the gas line.

[0013] Furthermore, such a case may occur if the gas line has a leak, which causes a significant pressure drop in the gas line. Such a pressure drop can also be detected by a sensor and, if necessary, compared with the minimum pressure value reached in normal cases. A significantly lower value likewise indicates that activation of the flow limiting valve under the control of the shut-off valve is to be expected. Knowledge of the current pressure in the fuel gas tank is not required for this.

[0014] The pressure in the fuel gas tank and gas lines is measured by a sensor, but the presence of a suitable sensor device is a prerequisite. However, fuel gas tanks are not always equipped with a suitable sensor device, in particular a tank pressure sensor. Therefore, as an alternative or supplement, it is proposed to determine the pressure in the fuel gas tank with reference to further parameters, in particular temperature. The pressure in the fuel gas tank can then be estimated with reference to the temperature profile.

[0015] For example, if there is no tank pressure sensor, the temperature of the fuel gas tank and the pressure in the gas line can be detected and stored by sensors before the vehicle is stopped and before the shut-off valve is closed. Then, before the vehicle is started again, the temperature of the fuel gas tank is detected by sensors again, so that the expected pressure of the fuel gas tank can be calculated taking into account the temperature changes during the stopping phase and the pressure in the gas line according to the following formula: p2=p1×T2 / T1 During the ceremony, p1 = pressure in the gas pipe before shutdown p2 = Latest fuel gas tank pressure T1 = fuel gas tank temperature before shutdown T2 = Latest temperature of fuel gas tank

[0016] In a further development of the invention, it is proposed that for the check in step (a) the pressure difference across the valve module, i.e. the difference between the pressure in the fuel gas tank and the pressure in the gas line, is determined, for which purpose the following formula can be applied: dp=p2-p3 During the ceremony, p2 = Latest fuel gas tank pressure p3 = Latest pressure of gas pipe

[0017] The pressure difference determined before controlling the shut-off valve can be used to check very closely whether activation of the flow limiting valve is expected when the shut-off valve is controlled open, since the greater the pressure difference, the greater the flow rate through the flow limiting valve and, accordingly, the greater the risk of unintentional activation or flow restriction of the flow limiting valve.

[0018] Furthermore, it is proposed that after controlling the shut-off valve in step (b), the control of the shut-off valve is interrupted until activation of the flow restriction valve is completed. That is, the shut-off valve is only opened again when the flow restriction is no longer occurring. This ensures that fuel gas can be drawn from the fuel gas tank again at least until the flow restriction valve is activated again, since activation of the flow restriction valve is performed with a certain delay. Due to this delay, a certain degree of pressure equilibrium has already been achieved between the pressure in the fuel gas tank and the pressure in the gas line, thereby possibly avoiding further activation of the flow restriction valve.

[0019] Therefore, the time interval between two control steps for opening the shut-off valve is preferably selected depending on the reaction time of the flow restriction valve.

[0020] Furthermore, it is preferred that the pressure difference across the valve module is determined before each control of the shut-off valve in step (b). This has the advantage that the control strategy can be adapted to the latest determined pressure difference in each case, particularly in terms of the control time and / or the control interruption time ("dynamic control strategy"). In this way, pressure equilibration between the pressure in the fuel gas tank and the pressure in the gas line can be accelerated.

[0021] Preferably, the frequency of control and / or interruption of the shut-off valve is determined depending on the pressure difference across the valve module before the first control.

[0022] In a preferred embodiment of the present invention, an activation threshold of the flow restriction valve is determined, and the shutoff valve is controlled to withdraw fuel gas only when the activation threshold is exceeded, preferably with a safety margin taken into account. This ensures that no flow restriction occurs.

[0023] The appropriate consideration of the activation threshold of the flow limiting valve is particularly advantageous in fuel gas tank systems with multiple fuel gas tanks, since in this case, the required amount of fuel gas can be extracted from the other fuel gas tanks as long as it is ensured that the shut-off valves are not activated. Therefore, it is preferable to extract fuel gas from the fuel gas tank with the lowest pressure. The extraction of fuel gas leads to a pressure increase in the gas line, which achieves a certain degree of pressure equilibrium between the pressure in the gas line and the tank pressure of the other fuel gas tanks. As this pressure equilibrium progresses, the shut-off valves of the other fuel gas tanks can also be controlled to open, thereby emptying them evenly.

[0024] Furthermore, it is proposed that a deactivation threshold of the flow restriction valve is determined, and that the shut-off valve is only controlled again after the control is interrupted when the deactivation threshold is lowered below the threshold, thereby ensuring that the flow restriction is eliminated before the shut-off valve is controlled or opened again.

[0025] In addition, to achieve the above-mentioned object, a control device for a fuel gas tank system is proposed, which is set up to carry out the steps of the method according to the present invention. The control device can determine the time and frequency of the shut-off valve control. For this purpose, the control device can store activation and / or deactivation thresholds for the flow restriction valve. In a fuel gas tank system with several fuel gas tanks, the order of the shut-off valve control can be determined depending on the pressure difference determined specifically for each tank.

[0026] The method according to the invention and its advantages will now be explained in more detail with reference to the accompanying drawings. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a schematic diagram illustrating a fuel gas tank system operable in accordance with a method in accordance with the present invention; [Figure 2] 2 is a schematic vertical cross-sectional view showing a valve module of a fuel gas tank in the fuel gas tank system of FIG. 1. FIG. [Figure 3] 3 is a graph illustrating the control of the shut-off valve integrated in the valve module of FIG. 2 depending on the pressure difference (dp) between the fuel gas tank and the gas line. DETAILED DESCRIPTION OF THE INVENTION

[0028] 1 there can be seen a simplified diagram of a fuel gas tank system 1 having a number of fuel gas tanks 2. The illustrated fuel gas tank system 1 serves to supply a fuel gas, preferably hydrogen, to a fuel cell stack 8.

[0029] A valve module 3 is inserted into each fuel gas tank 2, and via this, each fuel gas tank 2 is connected to a gas pipe 7. These gas pipes 7 join together, so that substantially equal pressures are generated in each gas pipe 7. This pressure is measured by a pressure sensor 9. Another pressure sensor 9 is integrated into each fuel gas tank 2. Instead of the pressure sensor 9, each fuel gas tank 2 may be provided with only a temperature sensor 10.

[0030] 2 shows an enlarged view of the valve module 3 of the fuel gas tank 2. A take-off line 6 passes through the valve module 3 and is connected to a gas pipe 7. A shut-off valve 4 and—upstream of the shut-off valve 4 in the take-off direction—a flow restriction valve 5 are integrated into the take-off line 6. Between the flow restriction valve 5 and the shut-off valve 4, another flow restriction valve 11 for restricting the flow in the opposite flow direction and a filter 12 are arranged. Furthermore, a manually operable valve 13 and another filter 14 are integrated downstream of the shut-off valve 4.

[0031] Downstream of the shut-off valve 4 in the withdrawal direction, a tank filling line 15 branches off from the withdrawal line 6. The flow direction in the tank filling line 15 is set by an integrated check valve 16. In this way, the check valve 16 prevents fuel gas from escaping from the fuel gas tank 2 via the tank filling line 15.

[0032] In addition, the valve module 3 shown in Figure 2 has a release channel 17 in which further valves 18, 19 are arranged. On the one hand, there is another manually operable valve 18, also called a "bleed valve", which runs along all the valves. Valve 19 is a safety valve to relieve overpressure in the event of an overpressure occurring.

[0033] The main components for carrying out the method according to the invention are the shut-off valve 4 and the flow restriction valve 5 placed in front of it, as shown in Figure 2. Furthermore, each of the components shown is optional and not necessarily required for carrying out the method according to the invention.

[0034] In the following, the method according to the invention will be described with reference to FIG.

[0035] Initially, with the shut-off valve 4 still closed (see curve A), the fuel gas tank 2 is at pressure p Tank In the gas pipe 7, the pressure p Tank The pressure p is significantly lower than LeitungWhen the shutoff valve 4 is controlled to open (see curve A), the fuel gas flows from the fuel gas tank 2 to the gas pipe 7, causing a pressure difference p Leitung rises sharply. This means that the flow rate through the shutoff valve 4 and the flow rate limiting valve 5 becomes very large. This leads to the activation of the flow rate limiting valve 5 (see curve B) after a slight delay (see arrow 20), thereby limiting the flow rate. Therefore, the pressure p Leitung In order to quickly eliminate the flow restriction, the control of the shut-off valve 4 is interrupted (see curve A), which completely shuts off the flow and the pressure p Leitung This ultimately leads to the deactivation of the flow limiting valve 5, so that in the subsequent process the pressure p Tank and pressure p Leitung The shut-off valve 4 can again be controlled to open until a pressure equilibrium between

[0036] If the flow limiting valve 5 is reactivated during the process of reaching pressure equilibrium, the control of the shut-off valve 4 can be interrupted again. [Explanation of symbols]

[0037] 1 Fuel Gas Tank System 2 fuel gas tanks 3 Valve Module 4. Shut-off valve 5. Flow restriction valve 6 Extraction route 7 Gas piping p Tank Fuel gas tank pressure p Leitung Gas pipe pressure dp pressure difference dp Aktiv Activation Threshold dp Deaktiv Deactivation Threshold

Claims

1. A method for operating a fuel gas tank system (1) comprising at least one fuel gas tank (2) for storing fuel gas under high pressure and a valve module (3) inserted in the fuel gas tank (2) for extracting fuel gas from the fuel gas tank (2), wherein for extracting fuel gas, a shut-off valve (4) integrated in an extraction line (6) of the valve module (3) communicating with a gas pipe (7) downstream of a flow restriction valve (5) in the extraction direction is controlled to be opened, 1. A method according to claim 1, wherein, before controlling the shutoff valve (4), in step (a), it is checked whether activation of the flow restriction valve (5) is expected, and if activation of the flow restriction valve (5) is expected, in step (b), the shutoff valve (4) is controlled multiple times at specific time intervals.

2. The latest pressure (p Ｔａｎｋ ) and / or the latest pressure (p Ｌｅｉｔｕｎｇ 2. The method of claim 1, wherein the temperature is detected by a sensor.

3. The latest pressure (p) of the fuel gas tank (2) can be calculated with reference to further parameters, in particular temperature. Ｔａｎｋ 3. The method of claim 2, wherein:

4. The latest pressure difference (dp) through the valve module (3) for checking in step (a) is the pressure (p Ｔａｎｋ ) and the pressure (p Ｌｅｉｔｕｎｇ 4. The method according to claim 2 or 3, characterized in that the difference between

5. 5. The method according to claim 1, wherein after the control of the shut-off valve (4) in step (b), the control of the shut-off valve (4) is interrupted until the activation of the flow restriction valve (5) is completed.

6. 6. The method according to any one of claims 1 to 5, characterized in that before controlling each of the shut-off valves (4) in step (b), the pressure difference (dp) across the valve module (3) is determined.

7. 7. The method according to claim 6, characterized in that the frequency of control and / or interruption of the shut-off valve (4) is determined depending on the pressure difference (dp) through the valve module (3) before the first control.

8. The activation threshold (dp Ａｋｔｉｖ ) is determined, and the shutoff valve (4) is operated at the activation threshold (dp Ａｋｔｉｖ 8. The method according to claim 1, wherein the control is performed only when the temperature of the heating element is below 1000° C.), preferably taking into account a safety margin.

9. The deactivation threshold (dp Ｄｅａｋｔｉｖ ) is determined and the shut-off valve (4) is operated after the interruption of the control by the deactivation threshold (dp Ｄｅａｋｔｉｖ 9. The method according to claim 1, wherein the control is resumed only when the temperature of the liquid crystal display falls below a certain value.

10. A control device for a fuel gas tank system (1), set up to carry out the steps of the method according to any one of claims 1 to 9.

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