Refueling procedure and tank system

Abstract

The invention relates to a refueling method (100) for refueling a hydrogen tank (201). The refueling method (100) comprises: - supplying (101) hydrogen into the hydrogen tank (201) via a refueling path (207) of a tank valve (203) of the hydrogen tank (201), - Opening (103) a pilot valve (217) of a shut-off valve (213) arranged in the withdrawal path (209) of the tank valve (203) while a pressure in the hydrogen tank (201) increases. The invention further relates to a tank system for storing hydrogen.

Description

The present invention relates to a refueling method for refueling a hydrogen tank and a refueling system for storing hydrogen according to the appended claims.Prior ArtTank valves for hydrogen tanks generally comprise a tankling path via which hydrogen is conducted into a gas store or a hydrogen tank during the tankling, and a removal path via which hydrogen is supplied from the hydrogen tank to one or more consuming systems during normal operation.In the filling path, a main check valve can be located, which permits a gas flow only in the direction of the hydrogen tank and closes it in the opposite direction.In the extraction path, an electrically actuated shut-off valve (SOV) can be located, which is electrically activated in normal operation and is accordingly open. Since a large opening cross section is usually to be released in this case, a very powerful actuator would be required for opening the shut-off valve, the installation space requirement of which actuator normally clearly exceeds the installation space available. Therefore, shut-off valves of this type are usually designed in two stages. This means that a pilot valve is provided which has a small seat diameter and stroke. The pilot valve is loaded by a spring with a prestressing force acting in the closing direction.In the idle state, the pilot valve is supported with a valve element on a main valve, i.e. a second valve stage, so that the prestressing force acts equally on the valve elements of the pilot and main valves in their closing direction.In addition to this spring force, three further pneumatic forces act on the valve element of the main valve. A control chamber pressure prevails at an upstream end face of the main valve element. This pressure causes a closing force on the main valve element.The control chamber is connected to an inflow side of the shut-off valve via a very narrow first throttle.When the pilot valve is closed, the same pressure prevails in the control chamber as on the inflow side of the shut-off valve. The downstream surface is divided into two sub-surfaces by the sealing seat of the main valve. The pressure prevailing upstream of the shut-off valve is present on the partial surface lying outside the sealing seat and, via this partial surface, causes an opening force on the valve element. On the other hand, the partial surface lying within the sealing seat is acted upon by the pressure prevailing downstream of the shut-off valve and brings about a further opening force on the valve element.If the pressure upstream of the shut-off valve is greater than downstream and the pilot valve is not actuated, the closing force predominates over the opening force and the main valve is pressed into its sealing seat and remains closed.If the pressure on both sides of the shut-off valve is the same and the pilot valve is not actuated, the pneumatic forces cancel one another out in the closing and opening direction, but the prestressing force of the spring still acts on both valve elements in the closing direction and keeps the valves closed.If the pilot valve is controlled and opened, the control chamber is connected to the outflow side of the shut-off valve via the opened valve and a second throttle. The flow cross section of the second throttle is usually significantly higher than that of the first throttle.If a lower pressure now prevails on the outflow side of the shut-off valve than on the inflow side, the pressure in the control chamber falls considerably below the pressure on the inflow side of the shut-off valve, so that with this pressure the pneumatic closing force on the main valve element also falls. The main valve opens and gas can now flow from the hydrogen tank to the consuming systems via the opened main valve seat.If the pilot valve is closed again, the control chamber pressure rises again to the pressure at the inflow side of the shut-off valve and the spring force consequently also brings about the closing of the main valve.In the case of filling, the shut-off valve is not activated and a pressure is applied from the outside on the outflow side of the shut-off valve. If this pressure exceeds the pressure in the hydrogen tank, the main check valve opens in the filling path. Since a considerable mass flow of hydrogen is conducted over the main check valve during refueling, a significant pressure drop occurs at this valve. The pressure downstream of the shut-off valve is thereby greater than that upstream of the shut-off valve and in the control chamber. This produces a resultant pneumatic force in the opening direction on the main valve element. If this exceeds the closing spring force, the main valve opens slightly without the shut-off valve being actuated. As a result, a portion of the hydrogen mass flow supplied during refueling can flow backwards via the shut-off valve.Since the medium supplied during refueling can also contain portions of liquid water and, in addition, the hydrogen cools down locally to a great extent in the narrow flow cross sections of the slightly open shut-off valve, water can freeze to ice in the shut-off valve and consequently block the shut-off valve.In order to prevent this, a further or an additional check valve can be arranged in series with the shut-off valve downstream thereof. This additional check valve prevents a flow through the removal path in the filling direction, but permits a flow through in the removal direction without a great pressure loss.The idle state is now present before a refueling operation and a starting pressure prevails everywhere. In order to initiate the filling process, a pressure is now applied from the outside on the outflow side of the additional check valve and on the inflow side of the main check valve, which pressure is greater than the starting pressure and causes the main check valve to open in the filling path. A hydrogen mass flow predefined by the filling station is now conducted via the open main check valve to the hydrogen tank, so that the pressure in the hydrogen tank rises. This mass flow produces a pressure drop at the opened main check valve, so that the pressure on the inflow side of the main check valve and thus on the outflow side of the additional check valve is again higher than the pressure in the hydrogen tank.The refueling operation is continued until the pressure on the inflow side of the main check valve reaches a target value. Since both the auxiliary check valve and the shut-off valve are closed during the filling process, the initial low starting pressure is maintained on the outflow side of the shut-off valve and thus also on the inflow side of the auxiliary check valve. Both the main valve element of the shut-off valve and the valve element of the additional nonreturn valve are consequently pressed into their respective sealing seat during the filling process with very high and ever-increasing forces. This represents a very high load for these sealing seats, for which they are generally designed, but which can nevertheless negatively affect the permissible operating duration of the tank valve in the event of more frequent occurrence.A known solution to avoid this high seat load in turn is to replace the auxiliary check valve with a throttle check valve. This is therefore no longer a check valve, but rather a throttle valve. Such a valve no longer seals in the rearward direction, but rather represents a throttle, while it allows the gas flow to pass through in the forward direction in a largely unimpeded manner. Such a bypass throttle can be integrated into the valve element of the throttle check valve in a particularly advantageous manner, so that no additional components are required for this purpose.During refueling, the same pressure prevails downstream of the shut-off valve as upstream of the main nonreturn valve. If the pressure drop across the main check valve is so great that the main valve of the shut-off valve opens, it opens only so far that a very small gas flow flows via the series connection of the throttle check valve and the shut-off valve.As a result of the pressure drop at the throttle of the throttle check valve, the gas pressure at the outlet of the shut-off valve decreases more and more with increasing volume flow, so that in the case of a low gas flow determined substantially by the throttle of the throttle check valve, a balance is set backwards via the shut-off valve.Accordingly, although a gas flow via the shut-off valve in the reverse direction is not prevented by the throttle check valve, it is nevertheless significantly reduced. This significantly reduces the risk of liquid water entering the shut-off valve and, as a result, icing of the shut-off valve. However, a residual risk remains with this prior art solution.Disclosure of the InventionWithin the scope of the present invention, a filling method and a filling system are provided. Further features and details of the invention are evident from the respective dependent claims, the description and the drawings. Features and details which are described in connection with the filling method according to the invention naturally also apply in connection with the filling system according to the invention and vice versa, so that with regard to the disclosure reference is or can always be made reciprocally to the individual aspects of the invention.The present invention serves in particular to completely prevent a flow through a shut-off valve of a tank system during refueling in the rearward direction, without a high seat load occurring in the main valve of the shut-off valve and in the additional nonreturn valve as a result. In particular, the present invention serves to conserve respective seals or sealing seats of a tank system and, as a result, to provide a particularly robust tank system.According to a first aspect of the present invention, a refueling method for refueling a hydrogen tank is thus provided.The fuelling method includes supplying hydrogen into the hydrogen tank via a fuelling path of a tank valve of the hydrogen tank, and opening a pilot valve of a shut-off valve disposed in the extraction path of the tank valve while a pressure in the hydrogen tank increases.The filling method presented is based on the opening of a pilot valve of a shut-off valve arranged in the removal path of the tank valve. By opening the pilot valve, gas flows from the control chamber of the shut-off valve via its outflow throttle into the gas volume between the shut-off valve and the additional nonreturn valve. As a result, the pressure in this gas volume is equal to the pressure in the hydrogen tank. Since this is somewhat lower than the pressure at the outflow side of the auxiliary check valve because of a pressure drop at a main check valve, the auxiliary check valve, however, always remains closed and no gas can enter the pilot valve of the shut-off valve via the outflow side and thus the shut-off valve per se.It may be provided that the pilot valve is opened such that fluid flows from a first space between the hydrogen tank and the pilot valve into a second space downstream of the pilot valve and upstream of an auxiliary check valve arranged in the extraction path, such that the fluid minimizes a pressure difference between the second space and a third space, wherein the third space is located between the auxiliary check valve and a main check valve arranged in the extraction path.It can furthermore be provided that the pilot valve is opened for a period of time between 50 milliseconds and 5 seconds, in particular between 100 milliseconds and 500 milliseconds.By opening and closing the pilot valve repeatedly for a short time during the entire filling of the hydrogen tank with hydrogen, in particular for a duration of 200 ms each, the main valve of the shut-off valve does not open. Even if the main valve of the shut-off valve should open, because a control pulse of the pilot valve was selected to be somewhat longer and / or because the volume between the shut-off valve and the auxiliary check valve is somewhat larger than usual, which would cause a longer pressure dip in the control chamber of the shut-off valve, the auxiliary check valve would remain closed.Even when the main valve of the shut-off valve is open, the pressure between the shut-off valve and the auxiliary check valve can never become greater than that in the hydrogen tank, while a somewhat higher filling pressure is present at an outflow side of the auxiliary check valve.It can furthermore be provided that the pilot valve is repeatedly opened and closed.Repeating the short control pulses for the pilot valve of the shut-off valve during the entire filling of the hydrogen tank with hydrogen has the effect that a maximum pressure difference can build up via the shut-off valve and the additional nonreturn valve, which pressure difference is as great as the pressure rise in the hydrogen tank during a time interval between two control pulses. The seat load for a sealing seat of the main valve of the shut-off valve and a sealing seat of the auxiliary check valve during the filling of the hydrogen tank with hydrogen is reduced by a multiple compared to an operation of filling the hydrogen tank with hydrogen without opening the pilot valve. Accordingly, a service life of the sealing seats is significantly extended.It can furthermore be provided that the pilot valve is opened in such a way that a main valve of the shut-off valve does not open.In order to prevent the main valve of the shut-off valve from opening, a duration of a pilot pulse for the pilot valve may be selected such that the pilot valve opens, but no movement of the main valve of the shut-off valve occurs. A duration of in particular 200 ms has proven to be suitable for this purpose.It can furthermore be provided that the pilot valve is permanently opened during the filling of the hydrogen tank with hydrogen.By opening the pilot valve permanently during the filling of the hydrogen tank with hydrogen, a pressure in the volume between the shut-off valve and the additional nonreturn valve continuously follows a slowly increasing pressure in the hydrogen tank. In this case, although opening of the main valve of the shut-off valve can no longer be ruled out, the additional nonreturn valve remains closed in any case, such that 100% of a filling gas flow is conducted via the filling path with a main nonreturn valve. Accordingly, only a gas flow flows in the forward direction via the pilot valve and, if appropriate, partially also via a main valve of the shut-off valve, which is required for the slow pressure build-up between the shut-off valve and the additional nonreturn valve. This gas flow is not branched off from the filling gas flow, but rather is taken off from the hydrogen tank. It is in the same ratio to the gas flow in the hydrogen tank as the gas volume between the shut-off valve and the additional nonreturn valve. There is no risk of icing here.It can furthermore be provided that the pilot valve is opened at a predetermined point in time after the beginning of the supply of hydrogen into the hydrogen tank.A predetermined period of time, such as. 200 ms, which passes after starting supplying hydrogen into the hydrogen tank until the pilot valve is opened, enables a pressure to be built up in the refueling path of the tank valve so that the pilot valve closes again after a drive pulse.According to a second aspect, the present invention relates to a tank system for storing hydrogen.The presented tank system comprises a hydrogen tank, a tank valve and a computing unit, wherein the tank valve comprises a tankling path and a removal path, wherein a main check valve is arranged in the tankling path, wherein a shut-off valve and an additional check valve are arranged in the removal path, wherein the shut-off valve comprises a pilot valve and a main valve, and wherein the computing unit is configured to open the pilot valve while a pressure in the hydrogen tank rises during a tankling process for filling the hydrogen tank with hydrogen.The proposed tank system serves in particular for carrying out the proposed tank filling method.Accordingly, it can be provided that the computing unit is configured to open the pilot valve according to a possible embodiment of the proposed refueling method.It can furthermore be provided that the computing unit is configured to release a closing movement of the pilot valve as soon as the filling of the hydrogen tank with hydrogen is ended.In order to enable a closing movement of the pilot valve, for example, a control pulse for controlling the pilot valve can be interrupted.Advantages that will be described in detail with respect to the filling method for filling a hydrogen tank according to the first aspect of the invention apply equally to the filling system for storing hydrogen according to the second aspect of the invention.Further advantages, features and details of the invention will become apparent from the following description, in which exemplary embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description can be essential to the invention individually or in any combination.DRAWINGSThe following are shown: FIG. 1 shows a possible embodiment of the filling method presented, FIG. 2 shows a possible embodiment of the presented tank system.DESCRIPTION OF THE EMBODIMENTSIn FIG. 1, a refueling method 100 for refueling a hydrogen tank is shown.The refueling method 100 comprises a refueling step 101 in which hydrogen is introduced into the hydrogen tank via a refueling path of a tank valve of the hydrogen tank.Further, the refueling method 100 includes an opening step 103 of opening a pilot valve of a shut-off valve disposed in the extraction path of the tank valve while a pressure in the hydrogen tank increases.Referring now to FIG. 2, a tank system 200 for storing hydrogen is shown.The tank system 200 includes a hydrogen tank 201, a tank valve 203, and an arithmetic unit 205.The tank valve 203 in turn comprises a tank filling path 207 and a removal path 209, wherein a main check valve 211 is arranged in the tank filling path 207 and a shut-off valve 213 and an additional check valve 215 are arranged in the removal path 209.The shut-off valve 213 includes a pilot valve 217 and a main valve 219.The arithmetic unit 205 is configured to open the pilot valve 217 while a pressure in the hydrogen tank 201 rises, in a refueling operation for filling the hydrogen tank 201 with hydrogen. As a result, gas flows from a control chamber of the shut-off valve 213 via its outflow throttle into a gas volume between the shut-off valve 213 and the additional nonreturn valve 215. As a result, the pressure in this gas volume becomes equal to the pressure in the hydrogen tank 201. Since this pressure is somewhat lower than a pressure at the outflow side of the auxiliary check valve 215 because of a pressure drop at the main check valve 211, the auxiliary check valve 215 however always remains closed and no gas can enter the pilot valve 217 of the shut-off valve 213 and thus the shut-off valve 213 per se via the outflow side. Accordingly, icing of the shut-off valve 213 is prevented when the hydrogen tank 201 is filled with hydrogen.

Claims

A refueling method (100) for refueling a hydrogen tank (201), the refueling method (100) comprising: - supplying (101) hydrogen into the hydrogen tank (201) via a refueling path (207) of a tank valve (203) of the hydrogen tank (201), - opening (103) a pilot valve (217) of a shut-off valve (213) disposed in the extraction path (209) of the tank valve (203) while a pressure in the hydrogen tank (201) increases.The refueling method (100) of claim 1, characterized in that the pilot valve (217) is opened such that fluid flows from a first space between the hydrogen tank (201) and the pilot valve (217) into a second space after the pilot valve (217) and before an auxiliary check valve (215) disposed in the extraction path (209), such that the fluid minimizes a pressure difference between the second space and a third space, the third space being between the auxiliary check valve (215) and a main check valve (211) disposed in the extraction path (209).Filling method (100) according to Claim 1 or 2, characterized in that the pilot valve (217) is opened for a period of time between 50 milliseconds and 5 seconds, in particular between 100 milliseconds and 500 milliseconds.Filling method (100) according to one of the preceding claims, characterized in that the pilot valve (217) is repeatedly opened and closed.Filling method (100) according to one of the preceding claims, characterized in that the pilot valve (217) is opened in such a way that a main valve (219) of the shut-off valve (213) does not open.Filling method (100) according to Claim 1 or 2, characterized in that the pilot valve (217) is permanently opened during the filling of the hydrogen tank (201) with hydrogen.Filling method (100) according to one of the preceding claims, characterized in that the pilot valve (217) is opened at a predetermined point in time after the beginning of the feeding of hydrogen into the hydrogen tank (201).A tank system (200) for storing hydrogen, the tank system (201) comprising: - a hydrogen tank (201), - a tank valve (203), - a computing unit (205), wherein the tank valve (203) comprises a tank filling path (207) and a removal path (209), wherein a main check valve (211) is arranged in the tank filling path (207), wherein a shut-off valve (213) and an auxiliary check valve (215) are arranged in the removal path (209), wherein the shut-off valve (213) comprises a pilot valve (217) and a main valve (219), and wherein the computing unit (205) is configured to open the pilot valve (217) while a pressure in the hydrogen tank (201) increases during a tank filling operation for filling the hydrogen tank (201) with hydrogen.The tank system (200) according to claim 8, characterized in that the computing unit (205) is configured to open the pilot valve (217) according to any one of claims 2 to 7.Tank system (200) according to claim 8 or 9, characterised in that the computing unit (205) is configured to release a closing movement of the pilot valve (217) as soon as the filling of the hydrogen tank (201) with hydrogen is ended.

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