DE102018201327A1 - Method for removing fuel from a pressure vessel system with several pressure vessels and pressure vessel system - Google Patents

Abstract

The technology disclosed herein relates to a method of removing fuel from a pressure vessel system of a motor vehicle. The pressure vessel system comprises at least a first pressure vessel 1 and a second pressure vessel 2, wherein the first pressure vessel 1 and the second pressure vessel 2 at least partially parallel fuel flow paths 211, 212 form. The method comprises the step of extracting fuel from the first pressure vessel 1, and then supplying the extracted fuel in part to at least one energy converter 300 and the second pressure vessel 2.

Description

The technology disclosed herein relates to a method of extracting fuel from a pressure vessel system having a plurality of pressure vessels.

Pressure tank systems as such are known. They serve for example for the storage of hydrogen in motor vehicles. In the pressure vessels, the hydrogen is stored under high pressure. By removing hydrogen, the pressure vessel cools down. When operating the pressure vessel system, make sure that the temperature of the pressure vessel is always above a minimum temperature for which the pressure vessels have been designed. Depending on the design of the pressure vessel system, it may happen, especially at low ambient temperatures, that the maximum possible discharge mass flow must be restricted in order to avoid excessive cooling of the pressure vessel

It is a preferred object of the technology disclosed herein to reduce or eliminate at least one disadvantage of a previously known solution or to suggest an alternative solution. In particular, it is a preferred object of the technology disclosed herein to propose a method for removing fuel as well as a pressure vessel system which allows an increased exhaust mass flow of fuel without thermally damaging the pressure vessel system during removal. Other preferred objects may result from the beneficial effects of the technology disclosed herein. The object (s) is / are solved by the subject matter of the independent claims. The dependent claims are preferred embodiments.

The technology disclosed herein relates to a pressure vessel system for a motor vehicle (e.g., automobiles, motorcycles, utility vehicles). The pressure vessel system is used to store under ambient conditions gaseous fuel. The pressure vessel system can be used, for example, in a motor vehicle that is operated with compressed natural gas (CNG) or liquefied (LNG) natural gas or with hydrogen.

Such a pressure vessel system comprises at least one pressure vessel, in particular a composite overwrapped pressure vessel (= COPV). The pressure vessel may be, for example, a cryogenic pressure vessel (= CcH2 or COP) or a high-pressure gas vessel (= CGH2).

High-pressure gas containers are designed to store fuel at ambient temperatures permanently at a nominal operating pressure (also called nominal working pressure or NWP) of about 350 bar (= overpressure relative to the atmospheric pressure), furthermore preferably of about 700 bar or more. A cryogenic pressure vessel is suitable to store the fuel at the aforementioned operating pressures even at temperatures well below the operating temperature of the motor vehicle.

The pressure vessel system comprises at least a first pressure vessel and a second pressure vessel. Suitably, the first pressure vessel and the second pressure vessel form parallel fuel flow paths. In particular, the flow paths of two connecting lines can be formed. The two connecting lines can each be connected at one end to a pressure vessel opening of the respective pressure vessel and open in a common flow path. The aforementioned flow paths or connecting lines can at least form a fluid connection between the first pressure vessel and the second pressure vessel. Appropriately, no pressure reducer is provided in the fluid connection. Thus prevails in the fluid connection with open valves of the pressure vessel and in quasi-stationary state, the same pressure as in the pressure vessels. In other words, therefore, the at least two pressure vessels are preferably provided in the high-pressure region of the anode subsystem. Suitably, the pressure vessel system is designed such that during refueling at least the first pressure vessel and the second pressure vessel can be filled with fuel.

The system disclosed herein further includes at least one controller. The control unit is u.a. set up to perform the process steps disclosed herein. For this purpose, based on signals provided, the control unit can regulate the actuators of the system at least partially and preferably completely (closed loop control) or control (open loop control). The controller may affect at least the pressure vessel system. Alternatively or additionally, the control unit may also be integrated in another control unit, e.g. in a higher-level control unit. The control unit can interact with further control devices of the motor vehicle.

The controller may be configured to control the pressure vessel system such that fuel is withdrawn from the first pressure vessel, and that the extracted fuel is partially supplied to an energy converter and the second pressure vessel.

The pressure vessel system is configured to perform one or more of the methods disclosed herein.

• - einen Energiewandler-Massenstrom, der dem Energiewandler zugeführt wird; und
• - einen Druckbehälter-Massenstrom, der dem zweiten Druckbehälter zugeführt wird.

Likewise, the technology disclosed herein includes a method of removing fuel from a pressure vessel system, particularly the pressure vessel system for a motor vehicle disclosed herein. The method includes the step of removing fuel from the first pressure vessel, and then partially delivering the extracted fuel to the energy converter and the second pressure vessel. Thus, therefore, according to the technology disclosed here, the extraction mass flow of fuel taken from the first pressure vessel is divided into:

• an energy converter mass flow supplied to the energy converter; and
• - A pressure vessel mass flow, which is supplied to the second pressure vessel.

In other words, according to the technology disclosed here, the fuel taken from the first pressure vessel is simultaneously supplied to the at least one energy converter and the second pressure vessel. Advantageously, according to the technology disclosed herein, the extracted fuel may heat the second pressure vessel.

The at least one energy converter is set up to convert the chemical energy of the fuel into other forms of energy, for example electrical energy and / or kinetic energy. The energy converter can be, for example, an internal combustion engine or a fuel cell system / fuel cell stack with at least one fuel cell.

The technology disclosed herein may include the step of supplying the extracted fuel from the first pressure vessel to the second pressure vessel only at times when the fuel temperature in the second pressure vessel is less than the fuel temperature in the first pressure vessel. In other words, according to the method disclosed here, it is thus ensured that the extracted fuel is only supplied to the other pressure vessel when the supplied fuel also always heats the pressure vessel.

The method disclosed herein may include the step of removing the fuel from the first pressure vessel and supplying it to the second pressure vessel only until the fuel temperature in the first pressure vessel reaches a fuel limit temperature. The fuel limit temperature is, in particular, a lower limit temperature. The fuel limit temperature is suitably chosen so that thermal damage from the pressure vessel system, in particular from the pressure vessel, can be ruled out with certainty. For example, the fuel limit temperature may be -30 ° C, -35 ° C, -40 ° C, -50 ° C or -60 ° C.

For example, the fuel temperature may be determined by detecting a value indicative of the fuel temperature. This detected value can be compared in one embodiment with a value that is indicative of the fuel limit temperature. For example, the fuel temperature at the pressure vessel outlet, in particular at the on-tank valve, can be detected. In a further embodiment, the temperature of the pressure vessel inner wall or by the on-tank valve itself can be detected and compared with a corresponding reference value for the fuel limit temperature.

The method disclosed herein may include the step of extracting fuel from the second pressure vessel and delivering it to the energy converter after the fuel temperature in the first pressure vessel has reached the fuel limit temperature. Thus, it is thus advantageously ensured that the pressure vessel system can continue to provide fuel for the at least one energy converter of the motor vehicle even if it is no longer possible to remove it from the first pressure vessel. In other words, the method may thus comprise the step, after which removal from the first pressure vessel is stopped and removal from the second pressure vessel is started, if the temperature of the fuel in the first pressure vessel reaches or exceeds the fuel limit temperature. For this purpose, for example, the first Tankabsperrventil the first pressure vessel closed and at the same time or shortly thereafter, the second Tankabsperrventil the second pressure vessel are opened.

It is particularly preferred, at the same time for supplying fuel to the at least one energy converter and after the fuel temperature in the first pressure vessel has reached the fuel limit temperature, the fuel taken from the second pressure vessel partially fed back to the first pressure vessel. This is particularly advantageous if, at this time, the temperature of the fuel in the first pressure vessel is lower than the temperature of the fuel in the second pressure vessel. Consequently, the second pressure vessel now heats the first pressure vessel.

According to the technology disclosed herein, fuel may be provided to the at least one energy converter depending on the respective fuel temperature in the first and second pressure vessels from either the first pressure vessel or the second pressure vessel, wherein at the same time from the fuel-providing pressure vessel removed further fuel and the non-fuel-providing pressure vessel can be supplied.

• 1 eine schematische Darstellung eines Druckbehältersystems;
• 2 eine schematische Darstellung der Druck- und Temperaturverläufe; und
• 3 eine schematisches Ablaufdiagramm.

The technology disclosed herein will now be explained with reference to the figures. Show it:

• 1 a schematic representation of a pressure vessel system;
• 2 a schematic representation of the pressure and temperature curves; and
• 3 a schematic flow diagram.

The 1 schematically shows the pressure vessel system disclosed here. In the pressure vessels 1 . 2 Fuel is stored, eg hydrogen at 700 bar. The pressure vessels 1 . 2 provide hydrogen for the energy converter, here a fuel cell stack 300 with a variety of fuel cells operating at a lower pressure level. At the pressure vessel openings of the pressure vessel 1 . 2 here are each a Tankabsperrventil 251 . 252 intended. In the system shown here is also a pressure reducer 240 intended. The pressure reducer 240 reduces the pressure from 700 bar to a lower pressure level. The first pressure vessel 1 is with the second pressure vessel 2 connected via a fluid connection. The fluid connection is here through the fluid lines 211 . 212 educated. The fluid lines 211 . 212 are formed parallel to each other, wherein the term "parallel" does not refer to geometric parallelism here. The fluid lines 211 . 212 connect the pressure vessels here 1 . 2 or the Tankabsperrventile 251 . 252 with the pressure reducer 240 , The fluid system upstream of the pressure reducer 240 is also referred to as the high pressure area of the anode subsystem. Downstream of the pressure reducer 240 is here in the anode inflow path 215 a jet pump 234 intended. The anode inflow path 215 flows into the anode A from the fuel cell stack 300 , After the electrochemical reaction in the fuel cell stack 300 the anode exhaust gas leaves the fuel cell stack 300 , In the water separator 232 the product water is separated. Via the anode flush valve 238 The purge gas leaves the fuel cell system through the anode purge line 239 , The cathode side is over the compressor 410 Air sucked and compressed in the intercooler 420 is cooled. Also shown are the cathode-side stack shut-off valves 430 . 440 as well as the bypass line 460 ,

The 2 shows schematically the pressure and temperature curves, which result in the implementation of the technology disclosed herein. In the upper section of the figure, in each case the pressure profiles of the fuel pressure in the first pressure vessel 1 and second pressure vessel 2 presented over time. The dashed line shows the pressure curve in the second pressure vessel 2 and the solid line shows the pressure gradient in the first pressure vessel 1 , Analogously, the temperature profiles of the fuel in the first pressure vessel are in the lower portion of the figure 1 (shown as a dotted line) and in the second pressure vessel 2 (shown as a dotted line) over time.

Here, for the sake of simplification, it is assumed that at time t0 both pressure vessels 1 . 2 have the same pressure and temperature. At this time t0 is with the fuel extraction from the second pressure vessel 2 began. During fuel extraction from the pressure vessel 2 should first the Tankabsperrventil 251 from the first pressure vessel 1 be closed by the time t1. Due to the fuel extraction from the second pressure vessel 2 Temperature T _2X and pressure p _2X decrease in fuel in the second pressure vessel 2 whereas the temperature T _1X and the pressure p _1X from the fuel in the first pressure vessel 1 are substantially constant here until time t1. At time t1, the pressure p ₁₁ in the first pressure vessel 1 higher than the pressure p21 in the second pressure vessel.

In the example shown here it is now assumed that the temperature T _{2X of} the fuel in the second pressure vessel 2 has reached the fuel limit temperature T _G at time t1. If this is the case, then the first Tankabsperrventil 251 also open. There is thus a fluid connection between the two pressure vessels 1 . 2 made and it comes to pressure equalization. It flows from the first pressure vessel 1 removed fuel into the second pressure vessel 2 , After pressure equalization, the pressure corresponds to p11 'in the first pressure vessel 1 essentially the pressure p21 'in the second pressure vessel 2 , At the same time, the first pressure vessel is the fuel cell stack 300 over the anode inflow path 215 Fuel ready. But this does not have to be this way. Likewise, the fuel cell stack could 300 also be provided with some delay fuel. The pressure equalization heats the fuel in the second pressure vessel 2 abruptly from the temperature T21 = T _G to the temperature T _{21 '} . This is due to the fact that comparatively warm fuel in the second pressure vessel 2 flows and at the same time by the compression in the second pressure vessel 2 Compression heat arises. The removal from the first pressure vessel 1 At time t1 simultaneously causes a sudden drop in the fuel temperature in the first pressure vessel from the original value T ₁₁ to a temperature T _{11 '} , which is lower than the temperature T _21' in the second pressure vessel 2 , However, the temperature T _{11 is} higher than the fuel limit temperature T _G. Thus, so after the pressure equalization continues to fuel be provided from the first or second pressure vessel 1 . 2 , Appropriately, now the second tank shut-off valve 252 closed until time t2 and fuel is removed from the first pressure vessel 1 taken to the temperature T _1X from the fuel in the first pressure vessel 1 At time t2, the fuel limit temperature T _{G is} reached again. If this is the case, both tank shut-off valves will again be used 251 . 251 opened and it comes back to the pressure balance between the pressure vessel 1,2. Subsequently, in the period E _2C, the fuel is again from the second pressure vessel 2 taken at the same time, the first Tankabsperrventil 251 closed is.

In other words, the technology disclosed herein relates to a fuel supply system, in particular for supplying hydrogen, which comprises a plurality of pressure vessels or pressure tanks. The fuel extraction can take place simultaneously from both pressure tanks simultaneously. But it can also be done first from a pressure tank and then from the other pressure tank, for example, when limit parameters are reached in the first pressure tank.

The pressure tank 2 is the tank from which fuel is first removed and the first pressure tank 1 is the tank from which you want to extract fuel. In the period t0 - t1, first only from the pressure tank 2 taken. With this removal, the pressure tank will be 2 Cool until it reaches the lowest possible or allowed temperature T _G.

From this point in time t1 fuel will only come out of the pressure tank in the period t1 - t2 1 taken. This condition can also be referred to as E ₁ . The pressure tank 1 will cool progressively with this removal. At the same time, the pressure tank will be 2 but warm up because there is no fuel left from the pressure tank 1 is removed. When the pressure tank 1 its lowest possible / allowed temperature T _{G has} reached, in the period t2 - t3 fuel again from the pressure tank 2 removed (condition E2 ).

According to the technology disclosed herein, at time t1, the pressure tank is pressurized 2 cold and pressure tank 1 warm. As previously out of pressure tank 2 was taken and from pressure tank 1 not, is the pressure in the pressure tank 2 lower than in a pressure tank 1 , Preferably, according to the technology disclosed herein, the warm-up of a pressure tank is accelerated. This can be done by the cold pressure tank 2 with warm fuel from the pressure tank 1 is filled by brief Überströmvorgang. Part of the fuel from the pressure tank 1 is used to supply the drive unit of the motor vehicle. The second part of the removed fuel from the pressure tank 1 is used to the pressure tank 2 to fill. This "refueling" of pressure tank 2 is simply done with the pressure difference between the pressure tank 1 and 2 , Refueling from the pressure tank 2 with warm fuel from the pressure tank 1 will warm up the pressure tank 2 for two reasons: First, it will be warm fuel in the pressure tank 2 flowed in and mixed with the existing cold fuel. This increases the mixing temperature. Second, it will be the pressure in the pressure tank 2 increases and by the heat of compression of the fuel is further heated. With this concept, the pressure tank 2 warmed up faster and will become operational again sooner. When the pressure tank 1 too cold, can the same operating strategy for the pressure tank 1 be applied. This will prevent both tanks from reaching the lower temperature limit before they have become completely empty. Driving readiness problems with eg half full pressure tank are avoided. The tank system can be completely emptied without restriction even in very cold ambient temperatures

The 3 schematically shows a flow chart for carrying out the technology disclosed herein. The process starts with the step S100 , In step S200 it is determined if the temperature of the fuel in the pressure vessel 1 is higher than the fuel limit temperature T _G. If this is the case, then in step S300 the removal from the pressure vessel 1 authorized. If this is not the case, then in step S210 a pressure equalization between the first and second pressure vessel 1 . 2 achieved. It flows from the relatively warm pressure vessel 2 removed fuel into the pressure vessel 1 on. In step S400 it is checked whether the temperature of the fuel in the pressure vessel two is greater than the fuel limit temperature T _G. If so, it will be in step S500 Fuel taken from the pressure tank two and fed to the energy converter. If this is not the case, then in step S600 Checked whether the current temperature of fuel in the first pressure vessel 1 and in the second pressure vessel 2 are greater than the fuel limit temperature T _G. If this is not the case, then in step S700 the removal from both pressure vessels 1 . 2 prohibited and a corresponding note issued via a user interface. If, however, the temperature in the first pressure vessel is greater than the fuel limit temperature T _G , then in step S610 again achieved a pressure equalization between the two pressure vessels. It now flows from the first pressure vessel 1 Fuel in the second pressure vessel 2 on. The procedure then goes to the step S200 continued.

The foregoing description of the present invention is for illustrative purposes only, and not for the purpose of limiting the invention. Various changes and modifications are possible within the scope of the invention without departing from the scope of the invention and its equivalents.

Claims (10)

Method for removing fuel from a pressure vessel system of a motor vehicle, wherein the pressure vessel system has at least a first pressure vessel (1) and a second pressure vessel (2), wherein the first pressure vessel (1) and the second pressure vessel (2) at least partially parallel fuel flow paths (211 , 212), comprising the step of extracting fuel from the first pressure vessel (1), and then supplying the extracted fuel in part to at least one energy converter (300) and the second pressure vessel (2). Method according to Claim 1 wherein the extracted fuel from the first pressure vessel (1) is supplied to the second pressure vessel (2) only at times when the fuel temperature (T2X) in the second pressure vessel (2) is less than the fuel _temperature (T _1X ) in the first pressure vessel ( 1). Method according to Claim 1 or 2 , wherein from the first pressure vessel (1) only as long as the fuel is removed and the second pressure vessel (2) is supplied until the fuel _temperature (T _1X ) in the first pressure vessel (1) reaches a fuel limit temperature (T _Gu ). Method according to one of the preceding claims, further comprising in step, after which there is a pressure equalization between the first and second pressure vessel (1, 2) after the fuel _temperature (T _1X ) in the first pressure vessel (1) one or the fuel _{limit temperature} (T _GU ) has reached. Method according to Claim 3 or 4 wherein fuel is withdrawn from the second pressure vessel (2) and supplied to the energy converter (300) after the fuel temperature (Tix) in the first pressure vessel (1) has reached the fuel limit temperature (T _G ) and / or after it has been pressurized between the first and second pressure vessel (1, 2) came. Method according to Claim 4 or 5 , wherein after the pressure equalization of the energy converter (300) as long as from the second pressure vessel (2) is supplied with fuel until the fuel temperature (T2X) in the second pressure vessel (2) reaches the fuel limit temperature (T _G ). Method according to one of the preceding claims, wherein the energy converter (300) depending on the respective fuel temperature in the first and second pressure vessel (1,2) either from the first pressure vessel (1) or from the second pressure vessel (2) fuel is provided, and wherein at the same time taken from the fuel-providing pressure vessel further fuel and the non-fuel-providing pressure vessel is supplied. Method according to one of the preceding claims, wherein the first and second pressure vessel (1, 2) are fluidly connected to each other via a fluid connection, wherein in the fluid connection no pressure reducer is provided. A pressure vessel system for storing fuel, comprising at least a first pressure vessel (1) and a second pressure vessel (2), wherein the pressure vessel system is arranged, at least one method according to one of Claims 1 to 8th perform. A pressure vessel system for storing fuel, comprising: - At least a first pressure vessel (1) and a second pressure vessel (2), wherein the first pressure vessel (1) and the second pressure vessel (2) at least partially parallel fuel flow paths (211, 212) form; and - At least one control device, wherein the control device is adapted to control the pressure vessel system and / or to control that from the first pressure vessel (1) fuel is removed, and that the extracted fuel partially at least one energy converter (300) and the second pressure vessel (2) is supplied.

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