Fuel cell system for a mobile work machine

Abstract

The invention relates to a fuel cell system (1) for a mobile work machine, in particular an industrial truck, comprising a hydrogen-powered fuel cell device (4), a cooling system (11) which comprises a fan device (9), wherein the fan device (9) is designed to generate a cooling air flow for the fuel cell device (4), and a flushing system (13) which is designed to flush the fuel cell device (4). The fuel cell device (4) and the fan device (9) are secured to an assembly mount (3) which forms, between the fuel cell device (4) and the fan device (9), an exhaust air channel (10) of the cooling system (11) and a buffering storage chamber (12) of the flushing system (13), wherein the buffering storage chamber (12) is connected to the exhaust air channel (10) of the cooling system (11) by means of a throttle connection (35).

Description

[0001] Description

[0002] Fuel cell system for a mobile work machine

[0003] The invention relates to a fuel cell system for a mobile work machine, in particular an industrial truck, having a hydrogen-operated fuel cell device, having a cooling system comprising a fan device, wherein the fan device is configured to generate a cooling air flow of the fuel cell device, and having a purging system configured to purge the fuel cell device.

[0004] In mobile work machines, in particular industrial trucks, with an electric drive system, it is known to use a fuel cell system to supply energy to the electric drive system.

[0005] Known fuel cell systems comprise a hydrogen-powered fuel cell device, to which oxygen or ambient air is supplied at a cathode region and hydrogen is supplied at an anode region. In the fuel cell device, the oxygen from the ambient air is reacted with the hydrogen, generating electrical energy and waste heat. To dissipate this waste heat from the fuel cell device, a cooling system with a fan device is provided, which generates a cooling air flow through the fuel cell device.

[0006] A fuel cell system with a hydrogen-powered fuel cell device also requires a purging system that regularly purges the anode area of ​​the fuel cell device to remove unwanted foreign gas components and / or water that negatively impact the performance and service life of the fuel cell device. When purging the fuel cell device, the purging system generates purge gas containing hydrogen. During operation of the fuel cell system, hydrogen is thus released with the purge gas. To reduce the hydrogen concentration to permissible levels, it is necessary to mix the purge gas with another air stream, thereby diluting the hydrogen concentration.The present invention is based on the object of providing a fuel cell system for a mobile work machine, in particular an industrial truck, of the type mentioned at the outset, in which the hydrogen concentration can be diluted and reduced with little installation space required and low construction effort.

[0007] This object is achieved according to the invention in that the fuel cell device and the fan device are fastened to an aggregate holder which forms an exhaust air duct of the cooling system and a buffer storage chamber of the purging system between the fuel cell device and the fan device, wherein the buffer storage chamber is connected to the exhaust air duct of the cooling system by means of a throttle connection.

[0008] By attaching the fuel cell device and the fan device to an aggregate holder, a compact unit can be formed which forms an exhaust air duct of the cooling system and a buffer storage chamber of the purging system between the fuel cell device and the fan device.By connecting the buffer storage chamber by means of a throttle connection to the exhaust air duct of the cooling system, through which the cooling air flow generated by the fan device flows, it can be achieved with little construction effort that during a purging process of the fuel cell device, the hydrogen-containing purge gas can be introduced into the buffer storage chamber in a short period of time and stored in the buffer storage chamber and can be introduced and mixed into the exhaust air duct of the cooling system and thus into the cooling air flow generated by the fan by means of the throttle connection over a longer period of time, whereby the required dilution of the hydrogen concentration can be ensured in a simple manner.

[0009] According to an advantageous embodiment of the invention, the exhaust air duct of the cooling system and the buffer storage chamber of the flushing system are formed by a housing interior of the unit holder, and a partition plate is provided in the housing interior, which is attached to the unit holder and separates the exhaust air duct of the cooling system from the buffer storage chamber of the flushing system. With such a partition plate attached to the unit holder, the housing interior of the unit holder can be easily divided into the exhaust air duct of the cooling system and the buffer storage chamber of the flushing system, which is separated from the exhaust air duct.

[0010] According to an advantageous embodiment of the invention, the partition plate is provided with a throttle connection. This allows the throttle connection between the buffer storage chamber and the exhaust air duct to be easily established in the partition plate.

[0011] According to an advantageous embodiment of the invention, the throttle connection is formed by at least one throttle bore in the separating plate. One or more throttle bores can be produced in the separating plate in a simple manner and with minimal construction effort.

[0012] According to an advantageous embodiment of the invention, the partition plate provides several throttle holes spaced apart from one another in the flow direction of the exhaust air duct. With several throttle holes in the partition plate spaced apart from one another in the flow direction of the exhaust air duct, the hydrogen-containing purge gas can be fed into the cooling air stream at several spatially separated locations in the exhaust air duct, thus ensuring good mixing and high dilution of the hydrogen concentration even with a short exhaust air duct.

[0013] According to an advantageous embodiment of the invention, the buffer storage chamber is connected to the outlet side of a purge valve of the purge system via an inflow opening. The purge gas generated by the purge valve during a purge process of the fuel cell device can be easily introduced into the buffer storage chamber via the inflow opening, which is formed in particular in the unit holder.

[0014] According to an advantageous embodiment of the invention, the ratio of a cross-sectional area of ​​the inflow opening to a cross-sectional area of ​​the throttle connection is in the range from 2.0 to 4.0, in particular in the range from 2.5 to 3.5. The cross-sectional area of ​​the throttle connection is thus smaller than the cross-sectional area of ​​the inflow opening. With this ratio, it is easily achieved that during a purging process of the fuel cell device, the hydrogen-containing purge gas can be introduced into the buffer storage chamber in a short period of time and temporarily stored in the buffer storage chamber. Subsequently, by means of the throttle connection, it can be introduced over a longer period of time into the exhaust air duct of the cooling system and thus into the cooling air flow generated by the fan and mixed therein.

[0015] According to an advantageous embodiment of the invention, the inlet opening is arranged in the vertically lower region of the buffer storage chamber. This allows advantages to be achieved in the uniform filling of the buffer storage chamber with the purge gas.

[0016] According to an advantageous embodiment of the invention, the fuel cell system has a control device that controls the purging system and the fan device, wherein the control device is designed to operate the fan device at a purging speed during a purging process of the fuel cell device by the purging system that is increased compared to a normal operating speed during normal operation of the fuel cell system. With the increased purging speed, which can be set on the fan device before the start of the purging process and can be maintained for a predetermined period of time after the purging process, in particular until the buffer storage chamber is emptied, it is achieved in a simple manner that an increased cooling air flow is generated during the introduction of the purging gas into the cooling air flow flowing in the exhaust air duct, so that an effective dilution of the hydrogen concentration in the cooling air flow is achieved.

[0017] According to an advantageous embodiment of the invention, the control device is further configured to maintain a predetermined purging duration of the purging process and thus not to exceed the purging duration of the purging process and / or to maintain a predetermined waiting period between two purging processes. The amount of hydrogen introduced into the buffer storage chamber can thus be limited in order to ensure effective dilution of the hydrogen concentration to non-critical values. The invention further relates to a mobile work machine, in particular an industrial truck, having an electric drive system and a fuel cell system according to the invention, wherein the fuel cell system is configured to supply the electric drive system of the work machine with electrical energy, and wherein the fuel cell system has a housing configured to be inserted into a battery receiving space of the work machine.

[0018] In such work machines, the fuel cell system can be installed in the battery compartment of the work machine instead of a traction battery, for example, a bi-acid battery. Due to the limited space and size of the battery compartment, the available installation space for the fuel cell system intended as a replacement for a traction battery is also limited. Due to the limited installation space required for such a fuel cell system intended as a replacement for a traction battery, a long mixing section formed by the exhaust air duct for the hydrogen released during operation of the fuel cell system into the cooling air stream is not feasible.With the unit holder according to the invention, which forms the buffer storage chamber and the exhaust duct forming the mixing section, in conjunction with the throttle connection, sufficient dilution of the hydrogen concentration can be achieved even with a short exhaust duct. A costly catalyst for catalytically reacting the hydrogen released during operation of the fuel cell system can thus be dispensed with.

[0019] The invention has a number of advantages.

[0020] By temporarily storing the hydrogen-containing purge gas in the buffer storage chamber and continuously releasing the hydrogen via the throttle connection into the cooling air flow generated in the exhaust duct by the fan device, the required hydrogen concentration limits can be met and reduced to a safe level by spreading the hydrogen release over a very small space and thus a short exhaust duct length. This makes it possible to use standard components in non-explosion-proof versions in the fuel cell system, resulting in cost savings.

[0021] In addition, the fuel cell system according to the invention has a lower air requirement for diluting the hydrogen concentration due to the partition plate provided with throttle holes. In order to comply with the required hydrogen concentration limits, the speed of the fan device can be reduced during operation. This not only reduces the acoustic emissions of the fuel cell system, but also provides greater freedom in the optimal parameterization of the cooling and temperature control of the fuel cell device, which is the primary task of the fan device.

[0022] Further advantages and details of the invention are explained in more detail with reference to the embodiment shown in the schematic figures.

[0023] Figure 1 is a perspective view of the fuel cell system according to the invention,

[0024] Figure 2 shows an aggregate holder of the fuel cell system according to the invention with the fuel cell device and fan device mounted thereon,

[0025] Figure 3 shows a section through Figure 1 in the area of ​​the aggregate holder,

[0026] Figure 4 shows a section of Figure 3 in an enlarged view,

[0027] Figure 5 shows the aggregate holder in a perspective view and

[0028] Figure 6 shows the aggregate holder of Figure 5 in a top view.

[0029] Figure 1 shows a fuel cell system 1 according to the invention for a mobile work machine, in particular an industrial truck, with an electric drive system that can be used as a replacement for a traction battery in a battery receiving space of the work machine.

[0030] The fuel cell system 1 has a rectangular housing 2 within which the components of the fuel cell system 1 are installed.

[0031] In the upper corner area of ​​the housing 1, which is located at the front in Figure 1, there is arranged an aggregate holder 3, which is shown in more detail in Figure 2.

[0032] A hydrogen-powered fuel cell device 4 is attached to the assembly holder 3. For this purpose, a mounting flange 5 is formed on the top of the assembly holder 3—as can be seen in conjunction with Figures 3 to 6—to which the fuel cell device 4 is attached. The fuel cell device 4 is preferably designed as a fuel cell stack. An air filter 6 can also be arranged on the top of the fuel cell device 4.

[0033] The unit holder 3 is further provided with a flange plate 8, to which a fan device 9 of a cooling system 11 of the fuel cell device 4 is attached. The fan device 9 is preferably designed as an electric fan.

[0034] The unit holder 3 forms an exhaust air duct 10 of the cooling system 11 of the fuel cell device 4 and a buffer storage chamber 12 of a purge system 13 of the fuel cell device 4 between the fuel cell device 4 and the fan device 9.

[0035] The cooling system 11 comprises the fan device 9, which generates a cooling air flow flowing through the fuel cell device 4. The fan device 9 draws cooling air through two cooling air inlets 12a, 12b, which are formed in the upper region on the opposite end faces 2a, 2b of the housing 2 of the fuel cell system 1, into an air supply duct 15 formed below an upper cover 2c of the housing 2. From the air supply duct 15, the drawn-in cooling air flows through the air filter 6 and then the fuel cell device 4. From the fuel cell device 4, the cooling air heated at the fuel cell device 4 reaches the exhaust air duct 10 formed in the unit holder 3 and is discharged to the environment at a cooling air outlet 16 of the unit holder 3 via ventilation openings 17 in the end face 2a of the housing 2.

[0036] The cooling air flow is illustrated in Figures 3 and 4 with the arrows KL.

[0037] The fan device 9 is arranged in the cooling air flow downstream of the fuel cell device 4.

[0038] On the exhaust air duct 10 formed in the unit holder 3 - viewed in the direction of the cooling air flow - the fuel cell device 4 is arranged on the inlet side and the fan device 9 is arranged on the outlet side.

[0039] The cooling air sucked in by the fan device 9, which flows to the fuel cell device 4, can further be used as process air of a cathode region of the fuel cell device 4.

[0040] The purge system 13 of the fuel cell device 4 is designed to purge the fuel cell device 4 at an anode region to which hydrogen is supplied. The purge system 13 comprises a purge valve 20 arranged on the assembly holder 3, which is connected to the fuel cell device 4 via a purge line 21.

[0041] A connecting channel 22 is formed in the unit holder 3, to which the flushing valve 21 is connected and which opens into the buffer storage chamber 12. The buffer storage chamber 12 is connected to the outlet side of the flushing valve 21 of the flushing system 13 by means of an inflow opening formed by the cross-sectional area of ​​the connecting channel 22.

[0042] The exhaust air duct 10 of the cooling system 11 and the buffer storage chamber 12 of the purging system 13 are formed by a housing interior 3a of the unit holder 3. The housing interior 3a is bounded by a left wall 3b, a right wall 3c, and a bottom wall 3d of the unit holder 3.

[0043] In the housing interior 3a, a partition plate 30 is provided, which is fastened to the unit holder 3 and separates the housing interior 3a of the unit holder 3 into the exhaust air duct 10 of the cooling system 11 and the buffer storage chamber 12 of the flushing system 13.

[0044] As can be seen from Figures 4 to 6, the buffer storage chamber 12 is formed below the partition plate 30 and is formed by the left wall 3b, the right wall 3c, and the bottom wall 3d of the unit holder 3, which delimit the housing interior 3a, as well as the partition plate 30. The exhaust air duct 10 is formed by the housing interior 3a between the left wall 3b and the right wall 3c of the unit holder 3 above the partition plate 30.

[0045] As can further be seen from Figure 4, the partition plate 30 has a substantially horizontal section 30a, whereby the initial region of the exhaust air duct 10 facing the fuel cell unit 4 has a small height extension in the vertical direction, and a section 30b which is directed obliquely downwards, whereby the end region of the exhaust air duct 10 facing the fan device 9 has an increasing height extension in the vertical direction.

[0046] The buffer storage chamber 12 is connected to the exhaust air duct 10 of the cooling system 11 by means of a throttle connection 35.

[0047] In the illustrated embodiment, the partition plate 30 is provided with the throttle connection 35. The throttle connection 35 is formed by several throttle bores 36a, 36b, 36c, 36d in the partition plate 30, which are spaced apart from one another in the flow direction of the exhaust air duct 10. The throttle bores 36a, 36b are arranged in the initial region of the exhaust air duct 10 facing the fuel cell unit 4, and the throttle bores 36c, 36d are arranged in the end region of the exhaust air duct 10 facing the fan device 9.

[0048] The cross-sectional area of ​​the inflow opening of the connecting channel 22 is larger than the cross-sectional area of ​​the throttle connection 35. The ratio of the cross-sectional area of ​​the inflow opening of the connecting channel 22 to the cross-sectional area of ​​the throttle connection 35, i.e., the sum of the areas of the throttle bores 36a-36d, is preferably in the range from 2.0 to 4.0, in particular in the range from 2.5 to 3.5. The connecting channel 22 with the inflow opening is arranged - as can be seen from Figure 4 - in the vertically lower region of the buffer storage chamber 12.

[0049] The fuel cell system 1 further comprises a control device (not shown in detail) that controls the purging system 13 and the fan device 9. The control device is configured to operate the fan device 9 at a purging speed during a purging process of the fuel cell device 4 by the purging system 13, which is increased compared to a normal operating speed during normal operation of the fuel cell system 1. The purging speed can be set on the fan device 9 before the start of the purging process and can be maintained for a predetermined period of time after the purging process.

[0050] During a purging process, the anode side of the fuel cell device 4 is purged, whereby a hydrogen-containing purge gas is introduced via the connecting channel 22 into the buffer storage chamber 12 in the unit holder 3, created by the separating plate 30. Due to the cross-sectional area of ​​the inflow opening of the connecting channel 22, the purge gas can flow into the buffer storage chamber 12 and fill it within a short period of a few seconds.

[0051] The hydrogen-containing purge gas is introduced into the buffer storage chamber 12 via the connecting channel 22 in the vertically lower region. Due to the cross-sectional area of ​​the throttle connection 35, which is reduced compared to the cross-sectional area of ​​the inflow opening of the connecting channel 22, the purge gas is buffered in the buffer storage chamber 12 and slowly introduced via the throttle connection 35 formed by the throttle bores 36a-36d into the cooling air flow generated by the fan device 9 in the exhaust air duct 10. The exhaust air duct 10 forms a mixing chamber and a dilution zone in which the hydrogen contained in the purge gas is mixed with the cooling air flow, and the hydrogen concentration is diluted such that a non-critical hydrogen concentration is present at the end region of the exhaust air duct 10, where the fan device 9 is arranged.The mixing and dilution effect can be further improved by increasing the purge speed of the fan device 9, which generates an increased cooling air flow in the exhaust air duct 10. The introduction of hydrogen into the exhaust air duct 10 at the throttle bores 36a-36d and the mixing and dilution of the hydrogen with the cooling air flow KL in the exhaust air duct 10 is illustrated in Figure 4 by the arrows WL. Due to the shape of the partition plate 30 and the arrangement of the throttle bores 36a-36d, even with a short exhaust air duct 10, good mixing of the hydrogen contained in the purge gas with the cooling air flow can be achieved, and good dilution of the hydrogen contained in the purge gas to a non-critical hydrogen concentration at the inlet of the fan device 9 can be achieved.

[0052] The invention thus enables a reduction of the released hydrogen concentration in the purge gas of the fuel cell system 1 via intermediate storage and a continuous release by means of the buffer volume formed in the unit holder 3 by the buffer storage chamber 12, which is connected to the exhaust air duct 10 of the cooling system 11 by means of the throttle connection 35, with little installation space required and low construction effort.

Claims

Patent claims 1. A fuel cell system (1) for a mobile work machine, in particular an industrial truck, comprising a hydrogen-powered fuel cell device (4), a cooling system (11) comprising a fan device (9), the fan device (9) being configured to generate a cooling air flow for the fuel cell device (4), and a purging system (13) configured to purge the fuel cell device (4), characterized in that the fuel cell device (4) and the fan device (9) are fastened to an assembly holder (3) which, between the fuel cell device (4) and the fan device (9), forms an exhaust air duct (10) of the cooling system (11) and a buffer storage chamber (12) of the purging system (13), the buffer storage chamber (12) being connected to the exhaust air duct (10) of the cooling system (11) by means of a throttle connection (35).

2. Fuel cell system according to claim 1, characterized in that the exhaust air duct (10) of the cooling system (11) and the buffer storage chamber (12) of the purging system (13) are formed by a housing interior (3a) of the unit holder (3) and in the housing interior (3a) a separating plate (30) is provided which is fastened to the unit holder (3) and separates the exhaust air duct (10) of the cooling system (11) from the buffer storage chamber (12) of the purging system (13).

3. Fuel cell system according to claim 2, characterized in that the partition plate (30) is provided with the throttle connection (35).

4. Fuel cell system according to claim 3, characterized in that the throttle connection (35) is formed by at least one throttle bore (36a; 36b; 36c, 36d) in the partition plate (30).

5. Fuel cell system according to claim 4, characterized in that in the partition plate (30) there are several throttle bores (36a; 36b; 36c, 36d) which are spaced apart from one another in the flow direction of the exhaust air duct (10).

6. Fuel cell system according to one of claims 1 to 5, characterized in that the buffer storage chamber (12) is connected by means of an inflow opening to the outlet side of a flushing valve (20) of the flushing system (13).

7. Fuel cell system according to claim 6, characterized in that the ratio of a cross-sectional area of ​​the inflow opening to a cross-sectional area of ​​the throttle connection (35) is in the range from 2.0 to 4.0, in particular in the range from 2.5 to 3.

5.

8. Fuel cell system according to claim 6 or 7, characterized in that the inflow opening is arranged in the vertically lower region of the buffer storage chamber (12).

9. Fuel cell system according to one of claims 1 to 8, characterized in that the fuel cell system (1) has a control device controlling the purging system (13) and the fan device (9), wherein the control device is designed to operate the fan device (9) at a purging speed during a purging process of the fuel cell device (4) by the purging system (13) which is increased compared to a normal operating speed during normal operation of the fuel cell system (4).

10. Fuel cell system according to claim 9, characterized in that the control device is designed to maintain a predetermined purging duration of the purging process and / or to maintain a predetermined waiting period between two purging processes.

11. Mobile work machine, in particular industrial truck, with an electric drive system and a fuel cell system (1) according to one of the preceding claims, wherein the fuel cell system (1) is designed to supply the electric drive system of the work machine with electrical energy, and wherein the fuel cell system (1) has a housing (2) which is designed to be inserted into a battery receiving space of the work machine.

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