WO2015135626A1

WO2015135626A1 - Fuel cell system

Info

Publication number: WO2015135626A1
Application number: PCT/EP2015/000385
Authority: WO
Inventors: Michael Bader; Ralf NÜSSLE; Christine Sonntag
Original assignee: Daimler Ag
Priority date: 2014-03-13
Filing date: 2015-02-20
Publication date: 2015-09-17
Also published as: DE102014003624A1

Abstract

The invention relates to a fuel cell system (1) having at least one fuel cell (3), comprising an air discharge line (18) for the discharge air (A) from a cathode chamber (4) of the fuel cell (3) and a blow-off line (14) for blowing off exhaust gas (P) from an anode chamber (5) of the fuel cell (3), at least one sound absorber (19, 19'), a discharge air inlet (22), and a discharge air outlet (23) in the air discharge line (18), which is comprised of an externally closed outer sleeve (20) and an exhaust air duct (21) extending from the discharge air inlet (22) to the discharge air outlet (23) through the entire length of the sleeve (20), having connecting openings (24) to the space (25) inside the outer sleeve (20). The fuel cell system according to the invention is characterized in that the blow-off line (14) terminates in the sleeve (20).

Description

The fuel cell system

The invention relates to a fuel cell system according to the closer defined in the preamble of claim 1. Art Furthermore, the invention relates to the use of such a fuel cell system.

Fuel cell systems are known from the general state of the art. They can be used in particular for the provision of electrical drive power in electrically driven vehicles. Especially with this

Application of a fuel cell system play noise emissions to the

Environment of the fuel cell system or the vehicle a crucial role. For this reason, it is known that mufflers can be used to attenuate these noise emissions in the exhaust system of the fuel cell system, similar to an exhaust system of an internal combustion engine vehicle.

From JP 2009-289581 A is such a silencer for a

Fuel cell system known. The muffler is constructed so that water, which collects in the region of the muffler, can be sucked in accordance with the outgoing exhaust air and discharged with the exhaust air into the environment.

In addition to the sound damping and the dosed as possible and even discharge of water into the environment of the fuel cell system, the discharge of hydrogen-containing exhaust gases plays a crucial role. In particular, when used in vehicles, it is highly undesirable that punctually, spatially or temporally high

Hydrogen concentrations occur. Since hydrogen emissions via the exhaust gases of a fuel cell system are basically unavoidable, therefore, JP 2009-238762 A proposes a system in which a silencer with a plurality of chambers is constructed. Between Schalldämpfungskammern is also a

Provided dilution chamber for hydrogen, which communicates via connecting bores with a connecting the Schalldämpfkammern line element in communication. The advantage here is that also caused by the hydrogen gas

Noise emissions are reduced accordingly.

The structure of a silencer described in the last-mentioned prior art is not necessarily effective for the sound attenuation in the exhaust air of a fuel cell system. By the two comparatively large chambers, which over a

Conduit element are connected to a very small line cross-section, there are relatively large pressure losses, which in the exhaust stream or exhaust air flow of

Fuel cell system are only partially desirable. Furthermore, the over the

discharged hydrogen-containing exhaust gas from the anode compartment caused

Noise emissions are minimal, so that the effort required for their damping, which makes the silencer correspondingly large, is largely unnecessary.

The object of the present invention is now to provide an improved

Specify fuel cell system with a silencer, which avoids the above-mentioned disadvantages in particular.

This object is achieved by a fuel cell system with the

Characteristics solved in claim 1. A particularly preferred use of such a fuel cell system is specified in claim 13.

In the fuel cell system according to the invention, it is provided that the at least one silencer is formed, similar to the first-mentioned prior art, with an outer shell which is closed to the outside. Through this outer shell runs continuously from the exhaust air inlet to the exhaust outlet - especially straight - exhaust pipe, which provided with connecting openings to the outer shell, in particular perforated, is. This structure corresponds as far as the structure which is used in conventional combustion engines in the exhaust system. Such a silencer is also referred to as a resonator. In the resonant space of this resonator lying between the casing and the exhaust pipe, ie ultimately into the casing itself, in the embodiment of the fuel cell system according to the invention, the discharge line opens, via which exhaust gas from an anode space the fuel cell is blown off directly or indirectly. This blow-off, the so-called purge, of the exhaust gas may in particular be continuous or discontinuous, for example time-controlled, concentration-controlled or in-line

Dependence of an accumulated amount of water in the exhaust gas, done.

The construction has the decisive advantage that on the one hand it allows a very good sound attenuation of the sound present in the exhaust air, which in particular also effectively muffles sound emissions, such as those that can be generated by an exhaust air turbine arranged in front of the muffler in the flow direction. The structure is extremely simple. Through the mouth of the blow-off in the shell of the inevitably existing in the exhaust gas hydrogen evenly distributed in the so-called resonance space between the exhaust pipe and the shell and then flows slowly and evenly through the connection openings in the exhaust air. Thus, on the one hand a time delay and on the other hand a uniform distribution over the entire exhaust air occurs. Sometimes very high hydrogen concentrations can be avoided. Rather, very uniform, low hydrogen concentrations will occur at the outlet of the exhaust air system. Also, water, which optionally passes together with the exhaust gas from the anode compartment into the resonator, can be introduced via the resonance chamber. Similar to hydrogen, the proportion of liquid water in the exhaust air of the fuel cell system also applies here

correspondingly uniformed, so that suddenly occurring leakage of

Liquid water, especially in the form of a surge from the exhaust duct, is efficiently prevented.

According to an advantageous embodiment of the invention

Fuel cell system is the space inside the shell thereby formed divided into several sections. Such a subdivision of the space within the envelope, which surrounds the exhaust pipe with the connection openings, in several sections or

Chambers, improves soundproofing. The discharge line can open into one or more of the chambers.

In a very advantageous development of this idea, it is provided that the discharge line opens into one of the sections which is not the last section in the flow direction of the exhaust air. Such a confluence of the discharge line in one of in

Flow direction of the exhaust front, but at least the penultimate section is Particularly advantageous, since this a uniform distribution of the exhaust gas in the exhaust air can be achieved as possible.

Preferably, the exhaust pipe is arranged concentrically in the shell. This results on all sides around the exhaust pipe around a sufficient resonance space and

On the other hand, the hydrogen contained in the exhaust gas may be in this

Evenly distribute the resonance chamber around the entire exhaust pipe and then flow into the exhaust air through the connection openings, which are ideally distributed evenly over the surface. Concentric in the sense of the invention is to be understood as any structure in which the exhaust pipe is arranged in the center of the cross section of the shell. This applies in particular to round and oval casings, but may also be the case for other types of casings, for example polygonal casings or the like. Typically, the center of the exhaust pipe is then in the so-called

Centroid of the cross section through the shape of the shell. Again, this should be considered concentric in the context of the invention.

In an advantageous development of the fuel cell system according to the invention, it can now also be provided that the discharge line opens into the shell so that the gas flowing through the blow-off gas tangentially and / or with a

Direction component against the flow of exhaust air in the exhaust pipe, flows into the shell. As a result, a particularly uniform distribution and a particularly uniform timing of the exhaust gas to the exhaust air is achieved, even if the exhaust gas via the blow-off discontinuously, for example, from time to time, blown off.

According to a very advantageous embodiment of the invention

Fuel cell system, it may now also be provided that the

Silencer is arranged so that the flow of exhaust air in the direction of

Gravity is made obliquely downwards. Such downward flow of the exhaust air in the direction of gravity can be extremely useful, especially if the discharge line opens in the direction of gravity down into the shell. Of the

Hydrogen, which has a very low density, is then distributed not only by the direction of flow, with which it has been introduced into the resonance space between the shell and the exhaust pipe, in this, but also supporting it by gravity. The uniform distribution of hydrogen in the resonance chamber is thereby further favored. In a very advantageous development of this idea, it can now further be provided that the area of the exhaust air tube lying below is free from connection openings and only at least one arranged at the top in the direction of gravity

Having drainage hole in the area before the exit of the exhaust pipe from the shell. Such a construction takes into account the fact that in the exhaust gas from the anode compartment, especially when it collects in a so-called anode circuit and is blown off from time to time, typically liquid water is included or can be. In the according to the advantageous development

As described, it is now so that the lower portion of the exhaust pipe has no connection openings. Water can therefore collect accordingly in the resonance chamber below and can then reach the exhaust gas via the at least one drainage bore. If the drainage hole is designed to be correspondingly small, then a still further improved time delay of the discharge of the water into the exhaust air can be achieved. If, for example, discontinuously from time to time gas and water are blown into the resonance chamber, then comparatively high concentrations of water would occur in the exhaust air, always shortly after the exhaust gas was blown off. By the described construction, this can be prevented. The water collects in the resonance chamber and will be here for a certain time

cached and discharged via the drainage hole, the size of which can be adjusted accordingly, slowly and continuously. Ideally, the collected water is completely or almost completely discharged, if, for example, the time-controlled next blow-off cycle of the exhaust gas from an anode circuit occurs, so that water continuously enters the waste air stream in a small amount.

In a further advantageous embodiment of the invention

Fuel cell system, it may also be provided that the muffler, in which the discharge line opens, is arranged in the flow direction of the exhaust air before another muffler. The structure can therefore according to this advantageous

Further training also be realized so that two or more silencers

are arranged one after the other in the fuel cell system. In this case, the exhaust gas would turn into the at least penultimate of the fuel cell system

arranged muffler, in particular in the first in the embodiment with two mufflers introduced. The same applies as above for injecting into the at least penultimate chamber in the design of the silencer with individual Chambers has been mentioned. Basically, it is of course possible, the

to realize at least two mufflers in the system according to this development both with and without the individual sections or chambers.

As mentioned, the fuel cell system according to the invention can be constructed particularly simply and efficiently. It can be realized very small and compact and can still achieve a very good sound attenuation. In addition, the emission of exhaust gases, in particular the release of hydrogen in the exhaust gas, is continuously and uniformly distributed over the entire available amount of exhaust air. Time and place selectively high hydrogen concentrations can be avoided.

The same applies to the delivery of water, especially in the last

described embodiment of the fuel cell system.

The fuel cell system is therefore particularly suitable for applications in which attention must be paid to emissions of noise, hydrogen and water, and in which at least short-term high concentrations of water and hydrogen must be avoided when discharging into the environment. This is especially true for

Vehicles moving in public space. The particularly preferred application of the fuel cell system according to the invention is therefore its use in an electrically driven vehicle in which the fuel cell system provides the electrical drive power. About the fuel cell of the

Fuel cell system, the drive power can be provided directly to the vehicle or it can be a typical parallel to

Fuel cell system always existing battery, a so-called traction battery, which thus provides electrical power for the drive, are interposed. In particular, in cases in which more power is available on the fuel cell system than is required by the traction drive, for example because the driving performance has just reduced dynamically, any excess power of the fuel cell system in the traction battery will be supplied. All this is covered by the term "provide electrical drive power", in the context of the invention.

Further advantageous embodiments of the fuel cell system according to the invention and its use will become apparent from the embodiment, which is described below with reference to the figures. Showing:

Fig. 1 is a principle indicated fuel cell system in an embodiment according to the invention in a vehicle;

2 shows a silencer according to the invention in a three-dimensional sectional view; 3 shows a silencer according to the invention in an alternative embodiment in a three-dimensional sectional view;

Fig. 4 is a principle indicated fuel cell system in an alternative

Embodiment according to the invention;

Fig. 5 shows the concentration of water and hydrogen in the exhaust gas at a direct

Purge and a purge in the muffler; and

Fig. 6 shows an alternative embodiment of the muffler in the invention

Fuel cell system.

In the illustration of Figure 1, a fuel cell system 1 can be seen, which may be provided for example in a schematically indicated vehicle 2 for providing electrical drive power. The fuel cell system 1 in this case comprises a fuel cell 3, which is to be designed as a stack of individual PEM cells, as a so-called fuel cell stack. In this pile of

Single cells are in this case the anode regions of the individual cells and the cathode regions of the individual cells each connected to one another. By way of example, this is illustrated in FIG. 1 by way of an indicated cathode space 4 and an indicated one

Anode space 5 and an indicated therebetween proton-conducting membrane. 6

symbolizes. The anode chamber 5 of the fuel cell system 1 hydrogen is supplied from a compressed gas reservoir 7 via a pressure regulating and metering valve 8.

Unconsumed hydrogen returns from the anode compartment 5 via a so-called recirculation circuit or anode circuit 9 with a recirculation line 10 and is supplied to the input of the anode compartment 5 again. In order to compensate for pressure losses while a recirculation conveyor 1 1 is indicated in principle. This can be designed for example as a fan and / or as a gas jet pump.

In the anode circuit 9, water and inert gas accumulate over time, which must be vented to maintain the hydrogen concentration in the anode circuit. In the embodiment shown here is this one

Water separator 12 with a blow-off valve 13 and a discharge line 14 in principle indicated. The discharge of water and the blowing off of gas - the so-called purge - could just as easily take place via separate lines.

The cathode compartment 4 of the fuel cell 3 is provided with air as an oxygen supplier via an air conveyor 15. In the illustrated here

Embodiment, the air conveyor 15 should be designed as a flow compressor. This flow compressor sits together with a turbine 16 and an electric machine 17 on a common shaft. This structure is also referred to as an electric turbocharger or ETC (Electric Turbo Charger). About the air conveyor 15, the air is made available accordingly. It can then via optional not shown intercooler, humidifier or

be prepared for the fuel cell 3. The exhaust air from the

Fuel cell 3 passes in the embodiment shown here via a

Exhaust duct 18 directly, but it can also flow in practice over other components such as humidifiers or the like, to the turbine 16. In the area of the turbine 16, the air is expanded, so that the pressure energy and thermal energy contained in it can be at least partially recovered , This is done via the turbine 16, which provides the recovered energy directly via the shaft of the air conveyor 15 available. Additional power required is supplied via the electric machine 17. Does it come in certain situations to one

Power surplus in the area of the turbine 16, then it is also conceivable that

to operate electric machine 17 as a generator and recover electrical power through it.

After the turbine 16, the exhaust air flows via the exhaust duct 18 on to a

Silencer 19, which as a conclusion of the exhaust air line in the

Fuel cell system 1 is formed. His job is primarily to

Sound emissions, which are caused in particular by the turbine 16, to damp, so as to ensure the quietest possible operation of the fuel cell system 1 and the equipped with him vehicle 2.

The muffler 19 in a first possible embodiment is, as already indicated in the illustration of Figure 1 and can be seen in detail in the illustration of Figure 2, formed from a shell 20 through which an exhaust pipe 21 from an exhaust air inlet 22 to a Exhaust outlet 23 extends. The exhaust air flows as in the in 2 by the arrows marked A through the muffler 19. The exhaust pipe 21 has a plurality of connection openings 24, of which in the illustration of Figure 2 only a few are provided with a reference numeral. These connection openings 24 are formed in the exhaust pipe 21, that this example perforated or made of a perforated plate. They provide a connection between the interior of the exhaust pipe 21 and the surrounding space or space 25 of the shell 20, which is also referred to as a resonance chamber 25, since the muffler 19 may also be referred to as a resonator. By this construction, a significant sound insulation is achieved. The structure is so far known and customary, for example, from the field of mufflers in exhaust systems of internal combustion engines.

In the structure of the invention described here, it is now so that the discharge line 14 opens in the region of at least one mouth opening 26 in this resonance chamber 25, ie in the interior of the shell 20. Preferably, the injection of the with P

designated exhaust gas from the fuel cell 3 and the anode circuit 9 so that the gases perform both a swirling motion within the resonance chamber 25, as well as with a direction component counter to the flow direction of the exhaust gas A in the exhaust pipe 21 into the resonance chamber 25. This will be a

best possible distribution of the water and the exhaust gas P achieved in the resonance chamber 25. The gases and the water are then stretched over a longer period of time, even if the valve device 3 intermittently blows off a larger amount of exhaust gas and water from time to time into the exhaust air stream A.

As a result, emission peaks of the hydrogen inevitably located in the exhaust gas P are prevented when flowing into the environment and at the same time the delivery of liquid water, unless this evaporates anyway in the warmer exhaust air A, delayed in time so that a relatively uniform release of

Water is done in the area. As a result, the risk that the environment is wetted by a surge of sewage, significantly reduced.

An alternative embodiment of the muffler 19 can be seen in the illustration of FIG. The structure corresponds essentially to the structure described in the context of Figure 2. The only difference is that the room or

Resonant space 25 is divided by intermediate walls 30 into individual sections 25.1, 25.2, 25.3 and 25.4. To a possible ideal mixture of the exhaust gas P with in the To achieve exhaust air pipe 21 flowing exhaust air, the discharge line opens in the first in the flow direction of the exhaust air stream A arranged portion 25.4

Resonance space 25. He could in principle just as well in one of the other sections

25.1, 25.2, 25.3. However, to achieve the best possible mixing, the structure shown here is ideal. At least it should in the penultimate in the flow direction of the exhaust air flow A section, so in the illustration of Figure 3 the section

25.2, open.

An alternative embodiment of the fuel cell system can be seen in the illustration of FIG. The structure again corresponds, with the exception of the missing vehicle 2, to the construction shown in FIG. The muffler 19, in which the discharge line 14 opens, is one of two mufflers 19, 19 ', which are arranged in the fuel cell system 1. Here, similar to the statements just made with regard to the sections 25.1 - 25.4, the muffler 19, in which the discharge line 14 opens, the first in the flow direction, or, if more than two mufflers 19, 9 'are present, at least that in the flow direction penultimate of this muffler 19, 19 '. In the illustrated embodiment, the muffler 9 is formed very short with only one resonance space 25, the

Subsequent muffler 19 'with a slightly longer design and several sections 25.1, 25.2, 25.3 of the resonance chamber 25. Equally well, it would be possible in both mufflers 19, 19' to divide the resonance chamber 25 into individual sections, or in either of the two.

In the two diagrams of Figure 5, the concentration of the example

Hydrogen in the exhaust gas at the exit from the fuel cell system 1 shown. In the figure 3a above the direct discharge is shown in the exhaust duct 18, in the figure 3b, the discharge in the manner described in Figure 2 in the resonance chamber 25 of the muffler 19. It can be clearly seen that at a delivery at time t1 a concentration c1 occurs when the exhaust gas P is blown off directly into the exhaust duct 18. The

Concentration is relatively high and occurs only for a correspondingly small period of time. On the other hand, in the illustration of FIG. 3b the maximum concentration of c2 is recorded, which is clearly smaller than the concentration c1. It occurs somewhat later in time, and is stretched over a longer period of time, so that a large part of the hydrogen only enters the environment at time t2. When discharging into the muffler 9, this lasts until a time t3. The concentration will be in her Maximum value is reduced and the emission of hydrogen is distributed more evenly over a longer period of time. This applies analogously to the delivery of water.

Another possible embodiment of the muffler 19 can be seen in the illustration of FIG. The construction in FIG. 4 is inclined in the direction of gravity g, so that the exhaust gas A flows in the direction of gravity g obliquely downward through the muffler 9. The exhaust pipe 21 has no at the bottom

Connection openings 24, but is formed in this area largely without openings. The exhaust gas P passes again via the discharge line 14 in the

Resonance chamber 25 of the muffler 19. Again, the resonance chamber 25 of the muffler 19 could in turn be divided into individual sections, as previously, in particular in the context of Figure 3, has been executed. Liquid water can now accumulate in the area lying in the direction of gravity and will only partially pass through the connection openings 24 in the exhaust duct. Most of the water accumulates, as indicated by the denoted by 27

Water surface is shown in the lower part of the resonance chamber 25 at. The resonance chamber 25 can be realized for example in the region in which the water accumulates, only in the direction of gravity g above the exhaust pipe 21 or partially separated via a partition wall 29 as a water collection area. About at least a small located in the region of the exhaust outlet 23

Drainage hole 28 at the top of the exhaust pipe 21, the water, which has accumulated in the resonance chamber 25, now in the exhaust air flow A. By a suitable choice of the diameter and the number of drainage hole (s) 28, the delivery of the water in the exhaust air A targeted be influenced so that only so much water is delivered at the time, as can be taken without swelling of the exhaust air A to the environment. The remaining water is temporarily stored in the resonance chamber 25 and continuously discharged via the correspondingly small drainage hole 28. The homogenization of the exiting water is thereby improved again compared to the embodiment described above.

A further advantage of the structure described here is that the supply of the exhaust gas P takes place in particular in the direction of gravity g below, so that the low-density hydrogen in the direction of gravity g increases upward and in addition to the flow pulse through the oblique and tangential pour in is distributed as uniformly as possible in the resonance chamber 25 and accordingly flows uniformly through the connection openings 24 in the exhaust pipe 21.

Claims

claims

1. Fuel cell system (1) with at least one fuel cell (3), with a

Exhaust duct (18) for the exhaust air (A) from a cathode chamber (4) of the fuel cell (3) and a discharge line (14) for blowing off exhaust gas (P) from a

Anode space (5) of the fuel cell (3), with at least one muffler (9, 19 '), with an exhaust air inlet (22) and an exhaust outlet (23) in the exhaust duct (18), which from an outer shell (20 ) and one

• from the exhaust air inlet (22) to the exhaust outlet (23) through the entire length of the shell (20) extending exhaust pipe (21) having connection openings (24) to the space (25) within the outer shell (20) consists,

characterized in that

the discharge line (14) opens into the casing (20).

2. Fuel cell system (1) according to claim 1,

characterized in that

the exhaust pipe (21) is formed as part of the exhaust pipe (18).

3. Fuel cell system (1) according to claim 1 or 2,

characterized in that

the space (25) within the shell (20) is divided into several sections (25.1, 25.2, 25.3, 25.4).

4. Fuel cell system (1) according to claim 3,

characterized in that

the discharge line (14) opens into one of the sections (25.2, 25.3, 25.4) which is not the last section (25.1) in the flow direction of an exhaust air flow (A).

5. Fuel cell system (1) according to one of claims 1 to 4,

characterized in that

the exhaust pipe (21) is arranged concentrically in the shell (20).

6. Fuel cell system (1) according to one of claims 1 to 5,

characterized in that

the discharge line (14) opens into the casing (20) in such a way that gas (P) flowing through the discharge line (14) flows tangentially into the casing (20).

7. Fuel cell system (1) according to one of claims 1 to 6,

characterized in that

the discharge line (14) opens into the casing (20) in such a way that gas (P) flowing through the discharge line (14) flows into the casing (20) with a directional component against the flow of exhaust air (A).

8. Fuel cell system (1) according to one of claims 1 to 7,

characterized in that

the muffler (19, 19 ') is arranged so that the flow of the exhaust air (A) takes place in the direction of gravity (g) obliquely downwards.

9. Fuel cell system (1) according to claim 8,

characterized in that

the lower region of the exhaust pipe (21) is free from connecting openings (24) and only has at least one in the direction of gravity (g) top drainage hole (28) in the area in front of the exhaust outlet (23).

10. Fuel cell system (1) according to one of claims 1 to 9,

characterized in that

the discharge line (14) branches off from an anode circuit (9) of the fuel cell system (1) and, in particular via a valve device (13), leads to the casing (21).

11. Fuel cell system (1) according to one of claims 1 to 10,

characterized in that

the muffler (19), in which the exhaust duct (14) opens, in

Flow direction of an exhaust air stream (A) in front of a further muffler (19 ') is arranged.

12. Fuel cell system (1) according to one of claims 1 to 1 1,

characterized in that

in the exhaust duct (18) in the flow direction before the at least one

Silencer (19, 19 ') an exhaust turbine (16) is arranged.

13. Use of a fuel cell system (1) according to one of claims 1 to 12 in a vehicle (2) for providing at least part of the electrical drive power.