Method for operating a gas tank system, controller

Abstract

The invention relates to a method for operating a gas tank system (1), comprising at least one gas tank (2) for storing gas at high pressure and a valve assembly (3) which is introduced into the gas tank (2) for extracting gas from the gas tank (2), in which a shut-off valve (4) is actuated and opened for extracting gas, the shut-off valve is integrated downstream of the flow-limiting valve (5) in the extraction direction into an extraction path (6) of the valve assembly (3), said extraction path leading into a gas line (7). According to the invention, before actuating the shut-off valve (4), it is checked in step (a) whether an activation of the flow-limiting valve (5) is expected to occur, and in step (b), in the event that an activation of the flow-limiting valve (5) is expected to occur, the shut-off valve (4) is actuated multiple times in succession at a defined time interval. The invention further relates to a control device for carrying out the steps of the method.

Description

Field of the Invention

[0001] The present invention relates to a method for operating a gas tank system, which includes at least one gas tank for storing gas under high pressure and a valve structure group placed in the gas tank for extracting gas from the gas tank. In addition, the present invention relates to a controller for a gas tank system.

[0002] Preferred application areas are mobile gas tank systems, in particular fuel cell vehicles and / or gas vehicles driven by gas. The gas can in particular be hydrogen or natural gas, which is stored in the gas tank under high pressure. Background Art

[0003] Mobile gas tank systems with at least one gas tank for storing gas, such as hydrogen or natural gas, are known. Here, the gas tank is usually designed as a high-pressure tank. High-pressure tanks always require shut-off valves to seal and lock the tank when the vehicle is not in operation. For safety reasons, the shut-off valve is in principle implemented as a normally closed valve. To provide further protection, a flow-limiting valve can be connected upstream of the shut-off valve, which strongly restricts the flow rate in the event of a disturbance and can thus discharge gas from the gas tank in a controlled manner.

[0004] The shut-off valve and the flow-limiting valve are usually integrated into a valve structure group, which can be placed as a compact unit into the gas tank, especially in the area of the bottleneck of the gas tank. This integration takes place in the extraction path of the valve structure group, which merges into a gas line. In addition to the shut-off valve and the flow-limiting valve, usually other components, especially other valves, are integrated into the extraction path.

[0005] When extracting gas from the gas tank, the pressure loss increases with the number of components in the extraction path. Therefore, the pressure threshold for activating the flow-limiting valve (hereinafter referred to as the activation threshold) needs to be lower than the differential pressure across the entire valve structure group. Therefore, when operating the shut-off valve, the risk increases that the flow-limiting valve is inadvertently activated and the flow rate through the opened shut-off valve is restricted. This danger exists especially when the pressure in the gas tank increases and / or the pressure in the gas line decreases, such that the difference between the pressure in the gas tank and the pressure in the gas line is particularly large. If the flow-limiting valve is activated, the flow rate is restricted, such that the required amount of gas cannot be extracted from the gas tank. In a gas tank system with multiple gas tanks, this results in extracting the missing amount from the gas tank in which the activation of the flow-limiting valve is least expected. Subsequently, an uneven emptying of multiple gas tanks will occur. Summary of the Invention

[0006] The object of the present invention relates to the task of preventing, when extracting gas from a gas cylinder, a flow restriction caused by an activated flow-limiting valve or at least attenuating the negative consequences of such a flow restriction. To solve this task, a method with the features of claim 1 is proposed. Advantageous refinements of the present invention can be derived from the dependent claims. Additionally, a controller for carrying out the steps of the method according to the present invention is proposed.

[0007] A method for operating a gas cylinder system is proposed, the gas cylinder system comprising at least one gas cylinder for storing gas under high pressure and a valve structure group inserted into the gas cylinder, the valve structure group being used to extract gas from the gas cylinder. In this method, in order to extract gas, a shut-off valve is actuated and opened, the shut-off valve being integrated into the extraction path of the valve structure group downstream of the flow-limiting valve in the extraction direction, and the extraction path flowing into a gas line. According to the present invention, before actuating the shut-off valve, it is checked in step (a) whether activation of the flow-limiting valve is expected. In the case where activation of the flow-limiting valve is expected, in step (b) the shut-off valve is actuated successively a plurality of times at a determined time interval.

[0008] By actuating the shut-off valve a plurality of times, the shut-off valve is opened successively a plurality of times. Between two opening phases, the shut-off valve is closed so that no gas is extracted from the gas cylinder. That is to say, between two opening phases, the high flow through the flow-limiting valve is stopped and thus the activation of the flow-limiting valve is stopped. Subsequently, the flow-limiting valve opens again so that the shut-off valve can be actuated or opened again in order to extract gas. If repeated activation of the flow-limiting valve occurs, the actuation of the shut-off valve is interrupted again until the activation of the flow-limiting valve ends and gas extraction from the gas cylinder can continue.

[0009] The proposed actuation strategy prevents a flow restriction caused by an unintentional activation of the flow-limiting valve. If the flow-limiting valve has been activated, the flow restriction can be quickly cancelled again by means of the proposed actuation strategy so that gas can be extracted from the gas cylinder even under adverse pressure conditions. Thus, in a mobile gas cylinder system, the system availability is formed again and thus the full range of the vehicle is formed again. In a gas cylinder system having a plurality of gas cylinders, uneven emptying of the gas cylinders can be prevented by means of the proposed actuation strategy.

[0010] The proposed actuation strategy results in a reduced requirement for the valve structure group inserted into the gas cylinder. The design of the valve structure group is accordingly simplified.

[0011] Preferably, in order to carry out the check in step (a), the current pressure in the gas cylinder and / or the current pressure in the gas line is detected in a sensing manner. In certain cases, it is already possible to estimate whether activation of the flow-limiting valve is expected based on the current pressure in the gas cylinder and / or the current pressure in the gas line.

[0012] For example, this can occur if a gas cylinder is exposed to sunlight for a long time in the case of a parked vehicle, such that the temperature rise causes a significantly large pressure increase in the gas cylinder. This significantly large pressure increase can be detected in a sensing manner and, if necessary, compared with the maximum pressure value reached under normal conditions. Then, a significantly higher value can (more precisely, also without knowledge of the current pressure in the gas line) infer the activation of the flow-limiting valve expected when operating the shut-off valve.

[0013] Furthermore, this can occur if the gas line has a leak, such that a significantly large pressure drop in the gas line occurs. This significantly large pressure drop can also be detected in a sensing manner and, if necessary, compared with the minimum pressure value reached under normal conditions. Conversely, a significantly lower value can infer the activation of the flow-limiting valve expected when operating the shut-off valve. Knowledge of the current pressure in the gas cylinder is not required for this.

[0014] The detection of the pressure in the gas cylinder and in the gas line in a sensing manner presupposes corresponding sensing means. However, gas cylinders are not always equipped with corresponding sensing means, especially tank pressure sensors. Therefore, alternatively or additionally, it is proposed to determine the current pressure in the gas cylinder based on additional parameters, especially temperature. Then, the pressure in the gas cylinder can be estimated based on the temperature profile.

[0015] For example, in the absence of a tank pressure sensor, the temperature in the gas cylinder and the pressure in the gas line can be detected and stored in a sensing manner before parking the vehicle and before closing the shut-off valve. Then, before restarting the vehicle, the temperature in the gas cylinder is repeatedly detected in a sensing manner, such that, taking into account the temperature change during the parking phase and the pressure in the gas line, the expected pressure in the gas cylinder can be calculated according to the following formula:

[0016] p2 = p1 x T2 / T1

[0017] where,

[0018] p1 = the pressure in the gas line before parking

[0019] p2 = the current pressure in the gas cylinder

[0020] T1 = the temperature in the gas cylinder before parking

[0021] T2 = the current temperature in the gas cylinder

[0022] In an extended embodiment of the present invention, it is proposed that in order to perform the check in step (a), the current differential pressure on the valve structure group is determined, that is, the difference between the pressure in the gas tank and the pressure in the gas line is determined. For this purpose, the following formula can be used:

[0023] dp = p2 – p3

[0024] wherein,

[0025] p2 = the current pressure in the gas tank

[0026] p3 = the current pressure in the gas line

[0027] Based on the differential pressure determined before operating the shut-off valve, it can be very accurately checked whether the activation of the flow-limiting valve is expected when the shut-off valve is operated and opened. Because the higher the differential pressure, the greater the flow rate through the flow-limiting valve, and thus the greater the risk of inadvertently activating the flow-limiting valve or flow restriction.

[0028] It is further proposed that in step (b), after operating the shut-off valve once, the operation of the shut-off valve is interrupted until the activation of the flow-limiting valve ends. That is, the shut-off valve is opened again only when there is no longer a flow restriction. This ensures that gas can be extracted from the gas tank again, at least until the flow-limiting valve is reactivated. Because the activation of the flow-limiting valve occurs with a certain delay. Due to this delay, a certain pressure balance has occurred between the pressure in the gas tank and the pressure in the gas line, so that further activation of the flow-limiting valve can be avoided if necessary.

[0029] Therefore, preferably, the time interval between two operating phases for opening the shut-off valve is selected according to the response time of the flow-limiting valve.

[0030] Furthermore, preferably, before each operation of the shut-off valve in step (b), the differential pressure on the valve structure group is determined. This approach has the advantage that the operating strategy can be adapted to the currently determined differential pressure respectively ("dynamic operating strategy"), especially in terms of the operating duration and / or the interruption duration of the operation. In this way, the pressure balance between the pressure in the gas tank and the pressure in the gas line can be accelerated.

[0031] Preferably, before the first operation, the frequency of operation and / or the frequency of interruption of the shut-off valve are determined based on the differential pressure on the valve structure group.

[0032] According to a preferred embodiment of the present invention, the activation threshold of the flow-limiting valve is determined, and the shut-off valve is operated to extract gas only when it is lower than, preferably lower than this activation threshold considering a safety margin. This measure ensures that no flow restriction occurs.

[0033] Especially in the case of a gas cylinder system having a plurality of gas cylinders, it is suitable to correspondingly consider the activation threshold of the flow limiting valve. Because in this case, if it is ensured that the activation of the flow limiting valve does not occur unexpectedly with the manipulation of the shut-off valve, the required amount of gas can be extracted from other gas cylinders. Therefore, preferably, gas is extracted from the gas cylinder with the lowest pressure. The extraction of gas causes a pressure increase in the gas line, so that a certain pressure balance is achieved between the pressure in the gas line and the cylinder pressure of the corresponding other gas cylinders. Then, with the continued pressure balance, the shut-off valves of the other gas cylinders can also be manipulated and opened, so that these gas cylinders are emptied evenly.

[0034] It is also proposed to determine the deactivation threshold of the flow limiting valve, and after the interruption of the manipulation, the shut-off valve is only manipulated again when the deactivation threshold is undershot. By this measure, it is ensured that the flow restriction is cancelled before the shut-off valve is re-manipulated or opened.

[0035] In addition, to solve the task mentioned at the beginning, a controller for a gas cylinder system is proposed, which is set up to carry out the steps of the method according to the invention. With the aid of this controller, the time point and frequency of the manipulation of the shut-off valve can be determined. For this purpose, the activation threshold and / or the deactivation threshold of the flow limiting valve can be stored in the controller. In a gas cylinder system having a plurality of gas cylinders, the manipulation sequence of the shut-off valve can be determined based on the differential pressure determined for each cylinder. Description of the Drawings

[0036] Below, the method according to the invention and its advantages will be explained in more detail based on the accompanying drawings. These drawings show:

[0037] Figure 1 A schematic diagram of a gas cylinder system that can operate according to the method according to the invention,

[0038] Figure 2 Showing Figure 1 A schematic longitudinal sectional view of the valve structure group of the gas cylinders of the gas cylinder system, and

[0039] Figure 3 Showing a graph for showing the manipulation of the shut-off valve integrated into the Figure 2 valve structure group according to the differential pressure (dp) between the gas cylinder and the gas line. Detailed Description of the Embodiment

[0040] It can be seen from Figure 1 a simplified schematic diagram of the gas cylinder system 1, which has a plurality of gas cylinders 2. The shown gas cylinder system 1 is used to supply gas, preferably hydrogen, to the fuel cell stack 8.

[0041] The valve structure group 3 is placed into each gas cylinder 2, and the corresponding gas cylinder 2 is connected to the gas line 7 through this valve structure group. The gas lines 7 converge such that there is substantially the same pressure in the gas lines 7. This pressure is measured by means of a pressure sensor 9. Additional pressure sensors 9 are respectively integrated into each gas cylinder 2. Instead of the pressure sensor 9, temperature sensors 10 can also be provided only in each gas cylinder 2.

[0042] From Figure 2 an enlarged schematic view of the valve structure group 3 of the gas cylinder 2 can be seen. The extraction path 6 passes through the valve structure group 3, and this extraction path merges into the gas line 7. A shut-off valve 4 and a flow-limiting valve 5 (upstream of the shut-off valve 4 in the extraction direction) are integrated into the extraction path 6. Another flow-limiting valve 11 for limiting the flow rate in the opposite flow direction and a filter 12 are arranged between the flow-limiting valve 5 and the shut-off valve 4. In addition, a manually operable valve 13 and another filter 14 are integrated downstream of the shut-off valve 4.

[0043] Downstream of the shut-off valve 4 in the extraction direction, a filling path 15 branches off from the extraction path 6. The flow direction in the filling path 15 is pre-determined by an integrated check valve 16. In this way, the check valve 16 prevents gas from flowing out of the gas cylinder 2 via the filling path 15.

[0044] In addition, Figure 2 the valve structure group 3 shown in

[0045] has a pressure relief path 17, in which additional valves 18, 19 are arranged. On the one hand, an additional manually operable valve 18 is provided, which passes by all the valves and is also referred to as the "Bleed Valve". This valve 19 is a safety valve for reducing possible overpressure. Figure 2 Important components for carrying out the method according to the invention are the shut-off valve 4 shown in

[0046] and the upstream-connected flow-limiting valve 5. The components shown additionally are optional and not necessarily required for carrying out the method according to the invention. Figure 3

[0047] In the case of the initially still closed shut-off valve 4 (see curve A), there is a pressure p in the gas cylinder 2, and there is a pressure p 线路 in the gas line 7, and this pressure p 线路 is significantly lower than the pressure p 罐 such that a differential pressure dp is generated. Now, if the shut-off valve 4 is actuated to open it (see curve A), then gas flows from the gas cylinder 2 into the gas line 7 such that the pressure p​线路 rises steeply. That is to say, the flow rate through the shut-off valve 4 and the flow-limiting valve 5 is very large. This causes the activation of the flow-limiting valve 5 (see curve B) with a certain delay (see arrow 20), so that the flow rate is restricted. Therefore, the pressure p in the gas line 7 线路 only rises slightly further. In order to quickly cancel the flow restriction, the control of the shut-off valve 4 is interrupted (see curve A), so that the flow rate is completely cut off and the pressure p in the gas line 7 线路 does not rise further. This ultimately leads to the deactivation of the flow-limiting valve 5, so that in the further process, the shut-off valve 4 can be re-controlled and opened until the pressure p 罐 and the pressure p 线路 reach a pressure balance.

[0048] If the pressure-limiting valve 5 is reactivated during the process for pressure balance, the control of the shut-off valve 4 can be interrupted repeatedly.

Claims

1. A method for operating a gas tank system (1), the gas tank system comprising at least one gas tank (2) for storing gas under high pressure and a valve structure group (3) placed in the gas tank (2), the valve structure group being used to extract gas from the gas tank (2), wherein, In order to extract gas, control and open the shut-off valve (4), which is integrated into the extraction path (6) of the valve assembly (3) downstream of the flow-limiting valve (5) in the extraction direction, and the extraction path merges into the gas line (7), It is characterized in that, before controlling the shut-off valve (4), it is checked in step (a) whether the activation of the flow-limiting valve (5) is expected, and in the case where the activation of the flow-limiting valve (5) is expected, the shut-off valve (4) is controlled successively a plurality of times at a determined time interval in step (b).

2. The method according to claim 1, It is characterized in that For performing the check in step (a), the current pressure (p 罐 ) in the gas tank (2) and / or the current pressure (p 线路 ) in the gas line (7) is / are detected in a sensing manner.

3. The method according to claim 2, It is characterized in that Determine the current pressure (p 罐 ) in the gas tank (2) as a function of additional parameters, in particular the temperature 4. The method according to claim 2 or 3, It is characterized in that, For performing the said check in step (a), the current differential pressure (dp) on the valve structure group (3) is determined, i.e., the pressure (p 罐 ) in the gas tank (2) and the pressure (p 线路 ) in the gas line (7) are determined, and the difference therebetween is calculated.

5. The method according to any one of the above claims, It is characterized in that After controlling the shut-off valve (4) once in step (b), the control of the shut-off valve (4) is interrupted until the activation of the flow-limiting valve (5) ends.

6. The method according to any one of the above claims, It is characterized in that Before each control of the shut-off valve (4) in step (b), the differential pressure (dp) on the valve assembly (3) is determined.

7. The method according to claim 6, It is characterized in that Before the first control, the control frequency and / or the interruption frequency of the shut-off valve (4) are determined according to the differential pressure (dp) on the valve assembly (3).

8. The method according to any one of the above claims, It is characterized in that Determine the activation threshold (dp 激活 ) of the flow-limiting valve (5), and only when it is below, preferably below the activation threshold (dp 激活 ) taking into account a safety margin, the shut-off valve (4) is actuated to extract gas.

9. The method according to any one of the above claims, It is characterized in that Determine the deactivation threshold (dp 停用 ) of the flow limiting valve (5), and after interrupting the manipulation, only manipulate the shut-off valve (4) again when it is below the deactivation threshold (dp 停用 ).

10. A controller for a gas tank system (1), which is configured to perform the steps of the method according to any one of the above claims.

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