DE102017215495A1 - Water separator for a fuel cell system, fuel cell system and method for operating a fuel cell system - Google Patents

Abstract

The invention relates to a water separator (41) for a fuel cell system (100) having a housing (43) which has a feed line (48) from an anode exhaust gas path (22) and a discharge line (49) to the anode exhaust gas path (22). The water separator (41) further has a riser pipe (44) formed for discharging water from the housing (43), which has a U-shaped end piece (45) arranged inside the housing. By means of a first opening (46) and a second opening (47) arranged downstream and below the first opening, both of which are arranged in the U-shaped end piece (45), the water separator (41) can be emptied reliably. The water separator (41), which further comprises a drain valve (42) in the riser pipe (44), can thus be reliably operated even under frost conditions.

Description

The invention relates to a water separator for a fuel cell system, a fuel cell system with a water separator according to the invention and a method for operating a fuel cell system according to the invention.

Fuel cells use the chemical transformation of a fuel with oxygen to water to generate electrical energy. For this purpose, fuel cells contain as a core component the so-called membrane electrode assembly (MEA for membrane electrode assembly), which is a microstructure of an ion-conducting (usually proton-conducting) membrane and in each case on both sides of the membrane arranged catalytic electrode (anode and cathode). The latter mostly comprise supported noble metals, in particular platinum. In addition, gas diffusion layers (GDL) can be arranged on both sides of the membrane-electrode arrangement on the sides of the electrodes facing away from the membrane.

As a rule, the fuel cell is formed by a multiplicity of stacked MEAs whose electrical powers add up. As a rule, bipolar plates (also called flow field plates or separator plates) are arranged between the individual membrane electrode assemblies, which ensure that the individual cells are supplied with the operating media, ie the reactants, and are usually also used for cooling. In addition, the bipolar plates provide an electrically conductive contact to the membrane-electrode assemblies.

During operation of the fuel cell, the fuel (anode operating medium), in particular hydrogen, is supplied to the anode via a flux field of the bipolar plate and electrochemically oxidized to protons with release of electrons (H ₂ → 2 H ⁺ + 2 e ^- ). About the electrolyte or the membrane, which gas-tight and electrically isolated from each other, the reaction chambers, a transport of protons from the anode compartment into the cathode compartment. The electrons provided at the anode are supplied to the cathode via an electrical line.

The cathode is supplied during operation of the fuel cell, oxygen or an oxygen-containing gas mixture (for example air) as a cathode operating medium, so that a reduction of O ₂ to O ^2- with absorption of the electrons takes place (½ O ₂ + 2 e ^- → O ^2-). At the same time, the oxygen anions in the cathode compartment react with the protons transported via the membrane to form water (O ^2- + 2 H ⁺ → H ₂ O).

In order to supply a fuel cell stack with the operating media, this has an anode supply and a cathode supply. The anode supply includes an anode supply path for supplying the anode operating medium into the anode chambers of the fuel cell and an anode exhaust gas path for discharging an anode exhaust gas out of the anode chambers. In addition, a recirculation line is arranged in the anode supply in order to feed unused and discharged from the fuel cell stack hydrogen in the stack again. The cathode supply includes a cathode supply path for supplying the cathode operating medium into the cathode chambers of the fuel cell and a cathode exhaust path for discharging a cathode exhaust gas out of the cathode compartments.

During operation of the fuel cell system, water reaches the anode sides of the fuel cells and eventually accumulates in the anode supply, particularly in the anode exhaust path. The product water may cause damage to a conveyor arranged in the recirculation line and block flow paths. Therefore, a water separator is usually disposed downstream of the stack and upstream of the recirculation conveyor in the anode exhaust path. The separated in the water from the gaseous anode exhaust gas liquid water is discharged through an exhaust system.

1 shows a schematic representation of a fuel cell system according to the prior art with a water separator 28 and a separator valve for draining the liquid water from the anode supply. According to the prior art, the water separator forms 28 often the lowest point of the anode loop to ensure that liquid water from the anode exhaust path runs into the water trap. To prevent the liquid water from having to be conveyed against gravity, a water outlet is also located at the lowest point of the separator, from where the water is discharged by means of a valve.

After switching off the fuel cell system, the water separator should be emptied as completely as possible in order to ensure a restart even in the event of frost. In particular, the freezing of valves should be avoided. This can not always be guaranteed with known water separators.

Due to the small available space for fuel cell systems, such as in electric or hybrid vehicles, as well as the requirement to position the separator at the lowest point of the anode circuit, the separator below a feed for the deposited Water can be arranged in an exhaust system. In this case, it is necessary to actively promote the liquid water.

The DE 10 2011 116 856 A1 discloses a fuel cell system having a compressor disposed in the anode circuit. A reservoir of the water separator is connected by means of a riser to the suction side of an ejector in the anode supply of the fuel cell stack. Thus, during operation of the ejector, water is drawn from the reservoir to humidify the anode resource.

The invention has for its object to overcome the disadvantages of the prior art and to provide a fuel cell system in which the safe discharge of separated liquid water is ensured by simple means to prevent the freezing of components of the system even in the event of frost.

This object is achieved by a water separator for a fuel cell system, a fuel cell system and a method for operating a fuel cell system according to the respective independent patent claims.

A first aspect of the invention relates to a water separator for a fuel cell system, comprising a housing having a lead from an anode exhaust gas line and a lead to an anode exhaust gas line and a riser pipe formed for discharging water from the housing. According to the invention, the riser pipe has a U-shaped end piece arranged inside the housing, with a first opening and a second opening arranged downstream and below the first opening. Downstream in this context refers to a flowing out through the riser from the water separator fluid. Below this means that the second opening in the vertical direction has a distance from the first opening. Merely clarifying it should be noted that perpendicular to the direction of the local gravitational acceleration designates. According to the invention, a separator valve is also arranged in the riser.

The water separator according to the present invention advantageously enables the discharge of the separated water from the separator into a cathode exhaust path of the fuel cell system or into an exhaust system of a fuel cell vehicle against gravity due to a pressure difference across the separator valve. The U-shaped end piece with the inventive arrangement of the first and second opening thereby improves the frost start behavior of the water separator, as will be explained in detail with respect to the inventive method. The water separator is preferably designed so that the first and second openings are under water during normal operation of the fuel cell stack. If the fuel cell stack is turned off, the water separator is emptied. In this case, water is discharged by means of the riser until the level drops to the height of the first opening. From this point, gas is sucked through the first opening, whereby, however, creates a negative pressure in the U-shaped end piece and water is sucked through the second opening. As a result, the level drops below the height of the first opening.

The riser may, apart from the U-shaped end piece, be arranged inside and / or outside of the housing. The riser provides a flow path from the separator through which a fluid must at least initially be conveyed against gravity. Preferably, the U-shaped end piece is monolithically formed with the remaining riser or alternatively fluid-tightly connected to the remaining riser. The U-shaped end piece has a connected to the riser or in this transition end and a free end. Particularly preferably, the first opening is arranged on or at least near the free end. Between the free end and the adjoining the riser end of the U-shaped end piece is at least approximately U-shaped with an upwardly open, preferably U, curved or V-shaped course formed. In the context of this invention, U-shaped thus also denotes a V-shaped, parabolic-shaped, and / or trough-shaped tail. The U-shaped end piece may be formed with continuous curvature or have kinks.

In a particularly preferred embodiment of the water separator according to the invention, the second opening of the U-shaped end piece is arranged at a lowest point of the U-shaped end piece. Here, too, the lowest point refers to the direction of the local gravitational acceleration. Also preferably, the second opening is arranged at least near the lowest point of the U-shaped end piece. This arrangement has the advantage that when emptying the water separator, the water level falls with high security under the first opening, which thus can not freeze and is immediately available even with a frost start.

In a further preferred embodiment of the water separator according to the invention, a downwardly pointing pipe piece is attached to the U-shaped end piece, in particular fluid-tightly and fluidly mounted, and the second opening is arranged in the downwardly pointing pipe piece. Particularly preferably, the downwardly facing pipe section is at or at least near the lowest point of the U-shaped tail attached. Also particularly preferably, the second opening is arranged at a free end or at the lowest point of the downwardly pointing pipe section. The free end refers to the not connected to the U-shaped end of the end of the downwardly facing pipe section. This embodiment advantageously allows a particularly deep lowering of the water level in the water below the first opening and even completely below the U-shaped tail. Consequently, the first opening and the U-shaped tail are free even in the case of a frost start.

Also preferably, the U-shaped end piece in the region of the branch of the downwardly facing pipe section on a constriction. As a result of the constriction, the flow velocity of a fluid drawn in through the first opening is increased in the region of the branch and thus the pressure is reduced locally. Through this jet pump effect, water is increasingly sucked in through the second opening, thus improving the overall water discharge from the water separator.

In a further preferred embodiment of the water separator according to the invention, this has a heating element, which is arranged in thermal contact with the riser pipe or the U-shaped end piece. By means of this heating element, the riser can be heated and thus its frost start properties can be further improved. In the case of a thermally conductive riser, a heating element disposed outside the housing may also be in good thermal contact with the U-shaped end piece. Also preferably, the separator valve itself is designed as a heatable valve. Due to the preferably thermally conductive riser, such as a metallic riser, the heat from the heated valve via the riser to the U-shaped tail, which can thus be deextended. A heatable valve is preferably arranged close to the U-shaped end piece, since icing is to be expected there most likely.

Also preferably, the supply line from the anode exhaust gas line and the discharge line to the anode exhaust gas line are arranged in an upper region of the housing of the water separator. Also preferably, means for separating liquid water are arranged between the supply lines and the bottom area. Also preferably, the water separator on a level sensor for detecting or detecting a water level in the water separator.

Another aspect of the present invention relates to a fuel cell system comprising a fuel cell stack having a plurality of fuel cells, a cathode supply having a cathode supply path and a cathode exhaust path, an anode supply having an anode supply path, an anode exhaust path, and a recirculation line connecting the anode exhaust path to the anode supply path. Upstream of the recirculation line, preferably downstream of the fuel cell stack, a water separator according to the invention, as described above, is disposed in the anode exhaust path. According to the invention, the riser of the water separator is connected via a drain to the cathode exhaust line or an exhaust system of an electric or hybrid vehicle. Alternatively, the riser itself opens into the cathode exhaust path or the exhaust system.

In the fuel cell system according to the invention, the water separator according to the invention advantageously permits the discharge of water from the anode supply of the fuel cell system solely on the basis of a pressure difference across the separator valve. This pressure difference exists between the interior of the housing of the water separator and the free end of the riser or the subsequent derivation. Preferably, the pressure difference between the interior of the water separator and the cathode exhaust path of a fuel cell system for discharging liquid water from the water separator is used.

The pressure differential across the separator valve results during normal operation of the fuel cell stack, that is, during generation of electrical energy with the stack, preferably from the amount of anode operating medium fed to the anode supply, the amount of anode operating medium recirculated in the anode supply, and / or the amount of the anode in the anode supply Anodenversorgung recirculated anode exhaust gas (in particular nitrogen) in relation to the pressure in the cathode exhaust path or the exhaust system. Also preferably, the degree of opening of the separator valve arranged in the riser influences this pressure difference. Even when the fuel cell stack is switched off, the pressure difference across the separator valve is largely determined by the amount of anode operating medium fed into the anode supply path. In particular, the pressure difference is always set via an anode operating medium supplied to the anode supply path from a fuel storage. Alternatively or additionally, the pressure difference across the separator valve is determined by the delivery rate of the recirculation conveyor arranged in the recirculation line. Thus, the supply of anode operating medium into the anode supply path, and optionally continued operation, allows the recirculation conveyor, with the stack off the emptying of the water separator.

Advantageously, with the water separator according to the invention during operation of the fuel cell system, a discharge of water from the housing of the separator against gravity is possible. During normal operation of the fuel cell stack, liquid water is continuously discharged therefrom and separated in the water separator. Preferably, the water separator is arranged, for example by the dimensioning of the housing and the arrangement of the riser and the U-shaped end piece, that the first and second openings are under water during normal operation of the stack. Thus, in the operation of the fuel cell stack, a discharge of any flammable gas from the water is avoided.

If the fuel cell stack is switched off, the water entry into the separator dries up. However, the pressure difference across the separator valve can be maintained even with the stack off by continued supply of anode resources, particularly hydrogen, into an anode supply path. Preferably, the supply of anode operating medium is carried out by feeding fresh anode operating medium from a fuel storage into the anode supply path. Particularly preferably, the continued supply of the anode operating means is carried out as a subsequent metering by means of a downstream of the fuel reservoir arranged adjusting means, such as a metering valve. Preferably, a recirculation line is flowed through or a recirculation conveyor flows around it, for example via a bypass line, or overflowed. Alternatively or additionally, the pressure difference across the separator valve may be maintained or at least enhanced by continued operation of a recirculation conveyor. Consequently, the separator is emptied after switching off the stack due to the pressure difference, in particular because the water discharged from the separator is not replaced by newly separated water. Thus, the fuel cell system of the present invention allows for easy emptying of the water separator by continued supply of anode resources, particularly hydrogen, into an anode supply path as described above.

Another aspect of the invention relates to a method of operating a fuel cell system according to the invention as described above. The inventive method has in a first embodiment, the normal operation of the fuel cell stack, that is, the operation of the fuel cell stack for generating electricity in the allowable range of the map, as well as the separation of liquid water in the water. Further, during normal operation of the fuel cell stack by sequential or continuous opening of the separator valve, liquid water is drained from the water separator. In a next step of the method according to the invention, the normal operation of the fuel cell stack is first terminated, for example initiated by a corresponding control signal of a controller in response to a decreasing load request or the shutdown of an electric or hybrid vehicle, and the drying of the water separator. The drying takes place in particular by supplying anode operating means, in particular hydrogen, into an anode supply path when the separator valve is open. Preferably, the supply of anode operating medium is carried out by feeding fresh anode operating medium from a fuel storage into the anode supply path. Particularly preferably, the continued supply of the anode operating means is carried out as a subsequent metering by means of a downstream of the fuel reservoir arranged adjusting means, such as a metering valve. Particularly preferably, the replenishment of the anode operating medium simultaneously serves to produce a protective gas atmosphere on the anode side of the fuel cell system and is also preferably part of a shutdown procedure of the fuel cell system. According to the invention, the discharge of water from the separator thus takes place, as described above, without entry of new product water.

In a preferred embodiment of the method according to the invention, this further comprises the step of detecting a water level in the housing of the water separator. This advantageously makes it possible to stop the drying operation as soon as the level has fallen sufficiently. This is done in particular by adjusting the supply of anode resources in the anode supply path and closing the Abscheiderventils when falling below a predetermined level of water in the housing of the water separator.

Further preferred embodiments of the invention will become apparent from the remaining, mentioned in the dependent claims characteristics. The various embodiments of the invention mentioned in this application are, unless otherwise stated in the individual case, advantageously combinable with each other.

• 1 eine schematische Darstellung eines Brennstoffzellensystems gemäß dem Stand der Technik;
• 2 eine schematische Darstellung eines Wasserabscheiders gemäß einem ersten Ausführungsbeispiel;
• 3 eine schematische Darstellung eines Wasserabscheiders gemäß einem zweiten Ausführungsbeispiel;
• 4 eine schematische Darstellung eines Wasserabscheiders gemäß einem dritten Ausführungsbeispiel;
• 5 eine schematische Darstellung eines Wasserabscheiders gemäß einem vierten Ausführungsbeispiel;
• 6 eine schematische Darstellung eines Wasserabscheiders gemäß einem fünften Ausführungsbeispiel; und
• 7 eine schematische Darstellung eines Brennstoffzellensystems gemäß einem Ausführungsbeispiel mit einem darin angeordneten Wasserabscheider gemäß dem ersten Ausführungsbeispiel.

The invention will be explained below in embodiments with reference to the accompanying drawings. Showing:

• 1 a schematic representation of a fuel cell system according to the prior art;
• 2 a schematic representation of a water separator according to a first embodiment;
• 3 a schematic representation of a water separator according to a second embodiment;
• 4 a schematic representation of a water separator according to a third embodiment;
• 5 a schematic representation of a water separator according to a fourth embodiment;
• 6 a schematic representation of a water separator according to a fifth embodiment; and
• 7 a schematic representation of a fuel cell system according to an embodiment with a water separator arranged therein according to the first embodiment.

1 shows a schematic representation of a generally designated 100a fuel cell system according to the prior art. This is part of an electric or hybrid vehicle, not shown, having an electric traction motor driven by the fuel cell system 100a is supplied with electrical energy.

The fuel cell system 100a comprises as a core component a fuel cell stack 10 containing a plurality of stacked single cells 11 having alternately stacked membrane-electrode assemblies (MEAs) 14 and bipolar plates 15 be formed (see detail). Every single cell 11 thus includes one MEA each 14 , which has an ion-conducting polymer electrolyte membrane, not shown here, as well as on both sides arranged thereon catalytic electrodes, namely an anode and a cathode, which catalyze the respective partial reaction of the fuel cell reaction and in particular can be formed as coatings on the membrane.

The anode and cathode electrodes comprise a catalytic material, such as platinum, supported on an electrically conductive high surface area support material, such as a carbon based material. Between a bipolar plate 15 and the anode thus becomes an anode compartment 12 formed and between the cathode and the next bipolar plate 15 the cathode compartment 13 , The bipolar plates 15 serve to supply the operating media in the anode and cathode rooms 12 . 13 and further provide the electrical connection between the individual fuel cells 11 ago. Optionally, gas diffusion layers are between the MEAs 14 and the bipolar plates 15 arranged.

To the fuel cell stack 10 to supply with the operating media, the fuel cell system 100a on the one hand, an anode supply 20 and on the other hand, a cathode supply 30 on.

The anode supply 20 of in 1 shown fuel cell system 100a includes an anode supply path 21 which feeds an anode operating medium (the fuel), for example hydrogen, into the anode spaces 12 of the fuel cell stack 10 serves. For this purpose, connect the anode supply paths 21 a fuel storage 23 with an anode inlet of the fuel cell stack 10 , The anode supply 20 further includes an anode exhaust path 22 containing the anode exhaust gas from the anode chambers 12 via an anode outlet of the fuel cell stack 10 dissipates.

The anode operating pressure on the anode sides 12 of the fuel cell stack 10 is about one with the fuel storage 23 connected actuating means 27 in the anode supply path 21 adjustable. Alternatively or additionally, a jet pump 24 in the anode supply path 21 arranged. In addition, the anode supply points 20 of in 1 shown fuel cell system 100a as shown, a recirculation line 25 on which the anode exhaust path 22 with the anode supply path 21 combines. The recirculation of fuel is common to the most over-stoichiometric fuel used in the stack 10 to be returned and used. In the recirculation line 25 is a recirculation conveyor 26 , preferably a recirculation blower, arranged. The recirculation line 25 is with the suction side of the jet pump 24 connected.

Further, in the anode exhaust path 22 downstream of the fuel cell stack 10 and upstream of the recirculation line 25 a water separator 28 installed to with the anode exhaust gas from the fuel cell stack 10 discharge discharged liquid water. The liquid water is removed from the water separator 28 about a derivative 40 an exhaust system as the most downstream portion of the cathode exhaust gas line 32 fed. The derivative 40 is with the water separator 28 via a controllable separator valve 42 connected. Here is the separator valve 42 at the lowest point of the water separator 28 arranged and thus always filled with water. Especially if the exhaust system is higher, it can be difficult to be discharged water accumulation on the separator valve 42 come, which can thus freeze under freezing conditions.

The cathode supply 30 of in 1 shown fuel cell system 100a includes a cathode supply path 31 which is the cathode spaces 13 of the fuel cell stack 10 supplying an oxygen-containing cathode operating medium, in particular air which is drawn in from the environment. The cathode supply 30 further includes a cathode exhaust path 32 , which the cathode exhaust gas (in particular the exhaust air) from the cathode compartments 13 of the fuel cell stack 10 dissipates and this the exhaust system supplies. For conveying and compressing the cathode operating medium is in the cathode supply path 31 a compressor 33 arranged.

In the illustrated embodiments, the compressor 33 as a mainly electric motor driven compressor 33 designed, the drive via a with a corresponding power electronics 35 equipped electric motor 34 he follows. The compressor 33 may also be through a in the cathode exhaust path 32 arranged turbine 36 (optionally with variable turbine geometry) are supported by a common shaft (not shown) driven.

This in 1 shown fuel cell system 100a also has a humidifier module 39 on. The humidifier module 39 on the one hand is in the cathode supply path 31 arranged so that it can be flowed through by the cathode operating gas. This is indicated by the humidifier module 39 a gas inlet and a gas outlet. On the other hand, it is so in the cathode exhaust path 32 arranged so that it can be flowed through by the cathode exhaust gas.

The cathode supply 30 also has a first shut-off means 37 and a second shut-off means 38 on, with the shut off the fuel cell stack 10 can be isolated from the environment. All adjusting means 24 . 37 . 38 . 42 . 61 of the fuel cell system 100a can be designed as controllable or controllable valves or flaps.

2 shows a separator 41 according to a first embodiment of the invention, wherein 2 (A) the separator 41 during normal operation of a fuel cell stack 10 and 2 B) during a drying operation.

The water separator 41 has a housing 43 , in particular a metal or plastic housing 43 , on. The housing 43 has a substantial circular cross section in a horizontal section through the separator 41 , A lower portion or a bottom portion of the housing 43 rejuvenates. The housing 43 also has a supply line 48 from an anode exhaust path 22 and a derivative 49 for an anode exhaust path 22 on.

During operation of the fuel cell stack 10 a fuel cell system 100 becomes moisture-laden anode exhaust via the anode exhaust path 22 and the supply line 48 in the water separator 41 initiated. There, liquid water is separated from the anode exhaust gas and collects as liquid water in the housing 43 , The dry anode exhaust gas is discharged via the drain 49 upstream of the recirculation line 25 back to the anode exhaust path 22 initiated.

The separator 41 also has a riser 44 on top of that through a cover of the separator 41 in the case 43 extends into it. In other words, the riser leaves 44 the separator 41 through its top. At the inside of the case 43 arranged end of the riser 44 is a U-shaped tail 45 arranged. The other, in 2 not shown, end of the riser 44 go to the in 7 shown derivative 40 over or flows directly into the cathode exhaust path 32 , In the riser 44 is outside the case 43 a separator valve 42 arranged. The riser 44 as well as the U-shaped tail 45 are designed as hollow pipes and have no openings on their lateral surfaces, except those specifically mentioned here.

A first end 45a of the U-shaped tail 45 go into the riser 44 above or is with the riser 44 connected. At the other, free end 45b of the U-shaped tail 45 is a first opening 46 arranged. The first opening 46 points upwards (relative to the orientation of the 2 as indicated by the reference numerals). At a lowest point 45c of the U-shaped tail 45 is a second opening 47 arranged in the U-shaped end piece. The second opening 47 points downwards (relative to the orientation of the 2 as indicated by the reference numerals).

As in 2 (A) shown, is the separator 41 designed so that during normal operation of the fuel cell stack 10 , while constantly more or less liquid water through the anode exhaust path 22 and the supply line 48 in the water separator 41 introduced and deposited there, both the first opening 46 as well as the second opening 47 below the water level 50 in the case 43 collected liquid water arranged. During normal operation of the fuel cell stack, depending on the degree of opening of the separator valve 42 sequential or continuous liquid water from the housing 43 about the riser 44 in the cathode exhaust path 32 of the fuel cell system 100 discharged.

As in 2 B) shown in a drying process, which after switching off the fuel cell stack 10 by supplying anode operating means, in particular hydrogen, from the fuel storage 23 by means of metering valve 27 in the anode supply path 21 the recirculation conveyor 26 with the separator valve open 42 can be performed, the water level 50 in the separator 41 be lowered significantly. During this drying process, the recirculation line is 25 or a bypass line disposed therein around the recirculation conveyor 26 flow through. First, liquid water over the first opening 46 , the U-shaped tail 45 , the riser 44 and the separator valve 42 discharged from the housing. The moment the level starts 50 to the height of the first opening 46 has fallen over the first opening 46 now sucked gas. The gas may be nitrogen, hydrogen, or another in the anode supply after the stack is turned off 10 This protective gas act. Through the below and downstream of the first opening 46 in the U-shaped tail 45 arranged second opening 47 is due to the through the first opening 46 sucked gas stream, water entrained. Thus, the water level in the separator 41 to the height of the second opening 47 be lowered. Because the second opening at the lowest point of the U-shaped tail 45 is arranged, then there is no more water in the U-shaped tail 45 , Thus, a frost start without the risk of icing of the separator valve 42 or the required for discharging water U-shaped end piece 45 respectively.

3 shows a separator 41 according to a second embodiment of the invention, wherein 3 (A) the separator 41 during normal operation of a fuel cell stack 10 and 3 (B) during a drying operation. In this respect, the water separator 41 according to the second embodiment of the water separator 41 according to the first embodiment, is based on a re-description of the corresponding features of the water separator 41 waived.

The water separator 41 according to the second embodiment has a downwardly facing pipe section 51 on, the at the U-shaped tail 45 and especially at its lowest point 45c is appropriate. The down-facing piece of pipe 51 is in particular fluid-carrying with the U-shaped end piece 45 connected. Because the second opening 47 in the down-facing piece of pipe 51 is arranged, the level drops 50 after performing the drying process of the separator 41 to the lower edge of the downwardly facing pipe section 51 , Advantageously, thus, the distance between the U-shaped tail 45 and the level 50 be further increased, causing the risk of an ice blockade in the U-shaped tail 45 reduced.

4 shows a separator 41 according to a third embodiment of the invention, wherein 4 (A) the separator 41 during normal operation of a fuel cell stack 10 and 4 (B) during a drying operation. In this respect, the water separator 41 according to the third embodiment of the water separator 41 According to the first or second embodiment, a further description of the corresponding features will be omitted.

The water separator 41 according to the third embodiment additionally has a constriction 52 on, which in the region of the branch of the downwardly facing pipe section 51 in the U-shaped tail 45 is arranged. The narrowing 52 leads locally to an increase in the flow velocity of the in the U-shaped tail 45 flowing fluid, in particular in the drying mode through the first opening 46 sucked gas. The negative pressure improves the suction of water through the second opening 47 , Thus, the drying or emptying of the housing takes place 43 after switching off the fuel cell stack 10 with increased reliability and possibly faster.

5 shows a separator 41 according to a fourth embodiment of the invention, wherein 5 (A) the separator 41 during normal operation of a fuel cell stack 10 and 5 (B) during a drying operation. In this respect, the water separator 41 according to the fourth embodiment of the water separators described above 41 corresponds to a re-description of the corresponding features of the water separator 41 waived.

The Indian 5 (A) shown separator 41 has a heating element 53 , in particular an electric heating element 53 , on, the jacket-shaped around one inside the housing 43 located portion of the riser 44 is arranged. With the water separator according to this embodiment, icing of the riser 44 be avoided. Is the riser 44 formed from a thermally conductive material, can also be the valve 42 and the U-shaped tail 45 by means of the heating element 53 be heated. In the in 5 (B) shown separator 51 is the heating element 53 in the upwardly open arcuate portion of the U-shaped end piece 45 arranged. The heating element is used 53 primarily the defrosting of the U-shaped tail 45 ,

6 shows a separator 41 according to a fifth embodiment of the invention, wherein 6 (A) the separator 41 during normal operation of a fuel cell stack 10 and 6 (B) during a drying operation. In this respect, the water separator 41 according to the fifth embodiment of the water separators described above 41 corresponds to a re-description of the corresponding features of the water separator 41 waived.

The in 6 shown water separator 41 has no additional heating element 53 on. Instead, the separator valve 42 even as a heated valve 54 educated. Thus, icing of the separator valve 54 be avoided with high reliability. By a riser 44 made of thermally highly conductive material is used, icing of the riser 44 and also the U-shaped tail 45 even with one, as in 6 (A) shown outside the case 43 arranged Abscheiderventils 54 be avoided. To further increase the safety of the deicing, the electrically heatable separator valve 54 , as in 6 (B) shown, but also in the housing 43 be arranged.

7 shows a schematic representation of a total designated 100 fuel cell system according to an embodiment. This is part of an electric or hybrid vehicle, not shown, having an electric traction motor driven by the fuel cell system 100 is supplied with electrical energy. In this respect, the fuel cell system 100 according to the embodiment of the fuel cell system 100a according to 1 corresponds to a further description of the corresponding features is omitted.

The fuel cell system 100 according to one embodiment of the invention differs from the prior art by a water separator 41 according to the invention in the anode exhaust path 22 of the fuel cell system 100 is arranged. The water separator 41 is formed, as above with reference to the 2 to 6 explained. The riser 44 of the water separator 41 is led out of this and goes with the Abscheiderventil 42 into the derivative 40 above. The derivative 40 opens into an exhaust system as the most downstream part of the cathode exhaust path 32 , Preferably takes place after switching off the fuel cell stack 10 of the fuel cell system 100 drying or emptying the water separator 41 by feeding anode fluid to the anode supply path 21 , preferably from a fuel storage 23 by means of a metering valve 27 , Here is the recirculation line 25 open. In addition, the emptying of the water separator 41 by the operation or further operation of the recirculation conveyor 26 get supported. The drying process is preferably carried out until one in the separator 41 arranged level sensor falls below a predetermined level of liquid water in the separator 41 is detected. Also, the supply of anode operating medium preferably adjusts the pressure difference across the separator valve 42 simultaneously producing a protective gas atmosphere in the anode supply 20 of the fuel cell system 100 ,

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102011116856 A1 [0011]

Claims (10)

A water separator (41) for a fuel cell system (100), comprising: a housing (43) having a lead (48) from an anode exhaust path (22) and a lead (49) to the anode exhaust path (22); and a riser pipe (44) formed for discharging water from the housing (43), the riser pipe having a U-shaped end portion (45) disposed within the housing and having a first opening (46) and a second opening (47) disposed downstream and below the first opening, and wherein a drain valve (42) is disposed in the riser pipe (44). Water separator (41) after Claim 1 , wherein the second opening (47) in the vertical direction at a distance from the first opening (46). Water separator (41) after Claim 1 or 2 wherein the first opening (46) is disposed at a free end (45b) of the U-shaped end piece (45) and / or the second opening (46) is located at a lowest point (45c) of the U-shaped end piece (45) is. A water separator (41) according to any one of the preceding claims, wherein a downwardly facing tube (51) is attached to the U-shaped end (45) and the second aperture (47) is disposed in the downwardly facing tube (51). Water separator (41) according to one of the preceding claims, wherein the U-shaped end piece (45) in the region of the branch of the downwardly pointing pipe section (51) has a constriction (52). Water separator (41) according to one of the preceding claims, wherein a heating element (53) in thermal contact with the riser (44) and / or the U-shaped end piece (45) is arranged and / or wherein the separator valve (42) as a heatable valve (54) is formed. A fuel cell system (100) comprising a fuel cell stack (10) having a plurality of fuel cells (11); a cathode supply (30) having a cathode supply path (31) and a cathode exhaust path (32); an anode supply (20) having an anode supply path (21), an anode exhaust path (22), and a recirculation line (25) connecting the anode exhaust path (22) to the anode supply path (21); and a water separator (41) disposed in the anode exhaust gas path (22) upstream of the recirculation line (25) according to any one of Claims 1 to 6 wherein the riser (44) is connected to the cathode exhaust line (32). Fuel cell system (100) after Claim 7 wherein the first opening (46) and the second opening (47) of the water separator (41) during normal operation of the fuel cell stack (10) below a liquid water level in the housing (43) of the water separator (41) are arranged. A method for switching off a fuel cell system (100) according to Claim 7 , the method comprising the steps of: normal operation of the fuel cell stack (10) with separation of liquid water in the water separator (41); Sequentially or continuously opening the separator valve (40) to drain liquid water from the water separator (41); Terminating the normal operation of the fuel cell stack (10); and drying the water separator (41) by supplying anode operating medium into the anode supply path (21) with the separator valve (40) open. Method according to Claim 9 , further comprising the steps of: detecting a water level in the housing (43) of the water separator (41); Adjusting the supply of anode operating fluid into the anode supply path (21) and closing the separator valve (42) while falling below a predetermined water level in the housing (43) of the water separator (41).

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