DE102017007090A1 - Vehicle with a fuel cell system - Google Patents

Abstract

The invention relates to a vehicle (1) in a fuel cell system for providing electric drive power, comprising an air compressor (14) and an exhaust gas turbine (27) for recovering energy from the exhaust gas, which compressed air previously compressed by the air compressor (14) comprising an auxiliary compressor (23) for air and / or exhaust gas and having a pressure tank (25) for receiving air and / or exhaust gas from the auxiliary compressor (23). The invention is characterized in that the pressure tank (25) in or parallel to an exhaust pipe (13, 131, 132) is arranged in the flow direction in front of an auxiliary turbine, with a switchable connection between the pressure tank (25) and the auxiliary turbine.
The vehicle (1) may be used in a method in which the deceleration of the vehicle is performed by the use of an electric traction motor as a generator, wherein the recovered energy is stored in an electric energy storage device, and wherein at least a part of the recovered energy in the Pressure tank (25) is stored, characterized in that the auxiliary compressor is driven with at least a portion of the recovered energy.

Description

The invention relates to a vehicle with a fuel cell system for providing electrical drive power according to the closer defined in the preamble of claim 1. The invention also relates to a method for using such a vehicle, wherein the braking of the vehicle performed by the use of an electric traction motor as a generator becomes.

Vehicles having a fuel cell system for providing electric drive power, which are also referred to as fuel cell vehicles, are well known in the art. Typically, such a fuel cell vehicle is equipped with a fuel cell system that generates electric power, for example, from compressed hydrogen on the anode side and from air provided via an air compressor on the cathode side. A plurality of such fuel cell vehicles includes an exhaust gas turbine for recovering energy from the heat and the pressure in the exhaust gas, which among other things consists of the exhaust air which has been compressed by the said air compressor before it has passed the fuel cell. According to the US 4,759,997 A Such an exhaust gas turbine can also be supplied with power by an additional combustion device in the exhaust line of the fuel cell.

According to the DE 10 2015 004 718 A1 For example, a fuel cell can also be equipped with an air compressor in combination with an electric motor on the one hand and an exhaust gas turbine in combination with a generator on the other hand. The components may be in operative connection, for example via an electrical energy storage device such as a battery and / or a capacitor.

The generic state of the art, published in the DE 10 2007 007 934 A1 describes a fuel cell vehicle having an auxiliary compressor for compressing air and charging a pressure tank with this compressed air. The auxiliary compressor may be mechanically driven by placing the auxiliary compressor in a drive connection to the wheels of the vehicle. The auxiliary compressor can thus be driven while providing braking energy for the vehicle. The compressed air is stored in a pressure tank parallel to the air compressor of the fuel cell system. If necessary, the air of the fuel cell can be provided alternatively or in addition to the compressed air of the air compressor.

The problem with this application is that the auxiliary compressor must be of relatively high quality, since no contamination of the compressed air can be accepted if the air is later provided to the cathode of the fuel cell. Another problem is that the pressure level for the air provided to the fuel cell is relatively low, for example, at about 15 kPa maximum. Therefore, the amount of stored energy in the pressure tank is relatively small, which requires a large pressure tank if a sufficient amount of energy is to be stored. This causes problems with the weight and volume required for the pressure tank.

The object of the present invention is therefore to provide a vehicle according to the preamble of claim 1 and to provide a method for the use of such a vehicle, which avoids the above-mentioned disadvantages and improves such a vehicle or such a method.

This object is achieved by a vehicle having the features in claim 1, in particular in the characterizing part of claim 1. With regard to the method, the object is achieved by a method having the features in claim 6. Advantageous embodiments of both the vehicle and the method are specified in the dependent subclaims.

The vehicle according to the invention uses an air compressor and an exhaust gas turbine for recovering energy from the exhaust gas, as known from the prior art. In addition, the fuel cell system of this vehicle according to the invention has an auxiliary compressor for air and / or exhaust gas and a pressure tank for receiving the air and / or the exhaust gas from the auxiliary compressor. According to the invention, the vehicle is characterized in that the pressure tank is arranged in the exhaust pipe or parallel to the exhaust pipe in the flow direction in front of an auxiliary turbine, wherein the connection between the pressure tank and the auxiliary turbine is switchable. Unlike in the generic state of the art mentioned above, the vehicle according to the invention has the auxiliary compressor and the pressure tank installed in the exhaust area of the fuel cell system. The auxiliary compressor may be used to compress exhaust gas, which may include the exhaust air from the cathode region of the fuel cell as well as exhaust gas from the anode side of the fuel cell. Alternatively or particularly preferably, in addition to this exhaust gas, air from the environment of the auxiliary compressor can be compressed. The compressed gases, which may include exhaust gas as well as air or combinations thereof, are then stored under pressure in the pressure tank. Unlike in the prior art, the compressed gas is not used directly to the Fuel cell to be passed. Instead, it is used to power the auxiliary turbine, which may be connected to a generator as known in the art. Therefore, the energy stored in the pressure tank can be used to recover energy at a later time by the drive of the auxiliary turbine. Because the compressed gas from the pressure tank is only used to power the auxiliary turbine, the gas quality requirements may be very low compared to that for gas supplied to the fuel cell. Therefore, the auxiliary compressor and the relevant components can be constructed much more cheaply than is the case in the application in the generic state of the art mentioned above.

According to the method of the invention, the deceleration of the vehicle is performed by using the electric traction motor as a generator. In the process, energy is recovered in the form of electrical energy and stored in an electrical energy storage device, such as e.g. a battery, a capacitor or a combination thereof stored. This is commonly referred to as regenerative braking. According to the method of the invention, at least part of the recovered energy is stored in the pressure tank by driving the auxiliary compressor with the recovered electric power. The electrical energy for driving the auxiliary compressor is a type of energy that is present in the vehicle anyway and which preferably can not be used otherwise. Therefore, the energy stored in the pressure tank is an additional recovered energy which is stored, for example, in the pressure tank when the electrical energy storage device is already fully charged. Since the compressed gas in the pressure tank is used to drive the auxiliary turbine, it can be compressed to a relatively high pressure, which allows the storage of a relatively large amount of energy in a relatively small vessel as a pressure tank. Preferably, the pressure tank and equipment may be the same as used in pneumatic brake systems in trucks. The pressure tank and the auxiliary compressor as well as the valves and the pipes which are needed can therefore be bought at a good price on the open market.

According to a very favorable embodiment of the vehicle according to the invention, the exhaust gas turbine is additionally used as an auxiliary turbine. First of all, this avoids a second turbine in the fuel cell system. Such an exhaust gas turbine is a relatively complex device, so that the use of a single turbine as an auxiliary turbine as well as exhaust gas saves costs, complexity, volume and weight. In addition, the exhaust gas turbine is typically in operative connection with the air compressor and at least one electric machine. For example, the air compressor and the exhaust turbine are arranged on the same shaft. In addition, an electric machine may be coupled to this shaft to operate as a motor or generator, depending on what functionality is needed. Such a construction is also referred to as an electric turbocharger or engine-assisted turbocharger. In such a construction, the use of the exhaust gas turbine in addition as an auxiliary turbine can enable the drive of the air compressor via the compressed gas in the pressure tank. This helps to reduce the amount of required electric power consumed by the electric machine when operating as a motor. The stored pressurized gas may thereby be utilized to increase the amount of air supplied to the fuel cell, for example, under freeze start conditions when a high load is requested from the fuel cell system, and / or when the low load fuel cell system is operated with a correspondingly very small volume flow of exhaust gas, which flows through the exhaust gas turbine.

Another alternative of the described structure of an electric turbocharger has the Wirkgebdingung only on the electrical side, for example, by a turbine and a generator on the one hand and an air compressor and a motor on the other hand is used. These can then be electrically connected, for example via power electronics and / or an electrical energy storage device.

In a further very advantageous embodiment of the vehicle, the pressure tank is arranged parallel to the exhaust pipe, wherein both parallel branches each have at least one valve device. With such valve devices, the flow of the exhaust gas through the exhaust pipe on the one hand or in the pressure tank on the other hand can be controlled. In this case, the use of the bypass to the pressure tank can be switched according to the requirements of the fuel cell system. The at least two valve devices can also be arranged as an integrated 3/2-way valve at one of the branching points.

Further advantageous embodiments of the vehicle according to the invention and the method for operating such a vehicle can be taken from the further dependent subclaims and the exemplary embodiment which is described in detail below with reference to the figure.

The sole attached figure shows a schematic diagram of a fuel cell system in an indicated vehicle according to the invention.

In the only attached figure is a vehicle 1 through a box around a fuel cell system 2 indicated in exemplary embodiment. The main part of the fuel cell system 2 is a fuel cell stack 3 , which is constructed as a stack of single cells. The fuel cell stack 3 includes a cathode region 4 and an anode region 5 , The anode area 5 is using hydrogen from a pressurized gas container 6 in which it is stored at a nominal pressure of about 70 MPa. The hydrogen flows through a pressure regulating and metering valve 7 to a gas jet pump 8th and in the anode area 5 of the fuel cell stack 3 , Exhaust gas from the anode area 5 , which still contains hydrogen, is via a recirculation line 9 to the gas jet pump 8th recirculated. It is powered by the gas jet pump 8th and with fresh hydrogen from the pressurized gas container 6 mixed. The mixture flows into the anode area 5 of the fuel cell stack 3 , In the recirculation line 9 Typically, liquid is passed through a water separator 10 separated from the recirculated gas. In the recirculation line 9 accumulates over time water vapor and inert gas. Therefore, for example from time to time or depending on a concentration of hydrogen in the recirculation line 9 , the water is in the water separator 10 drained and blown off together with the inert gas. For connecting a drain line 11 with a drain valve 12 the water separator 10 with an exhaust pipe 13 of the fuel cell system 2 ,

The cathode area 4 of the fuel cell stack is supplied with air as an oxygen supplier. The air is in an air compressor 14 compressed and flows through an air supply line 15 to the cathode area 4 , The compressed air passes through an intercooler 16 and a gas / gas humidifier 17 both of which are well known in the art. The exhaust air, which is depleted of at least part of its oxygen, passes through the gas / gas humidifier 17 again and gives moisture from the exhaust side of the fuel cell system 2 to the air in the supply air line 15 from. The exhaust air then flows through the exhaust pipe 13 connected to the drainage line 11 is connected to a branch of a so-called system bypass 18 which is a system bypass valve 19 having. About this system bypass 18 can be a switchable connection between the supply air line 15 and the exhaust pipe 13 getting produced. This can be used, for example, to prevent the air compressor 14 , which is designed as a turbomachine, the so-called surge limit exceeds. This is well known to those skilled in the art of fuel cell systems and air compressors in the form of prior art fluid machines. Therefore, it is not explained in further detail, as well as the intercooler 16 and the gas / gas humidifier 17 ,

The exhaust pipe 13 has another branch point, which is denoted by the reference numeral 20 is designated. At this branching point is the exhaust air in the exhaust pipe 13 already with the exhaust gas from the drain line 11 when the blow-off valve 12 is open, and with compressed air from the supply air line 15 when the system bypass valve 19 open, mixed. This mixed exhaust gas can now over a first branch 131 to the exhaust gas turbine 27 or over a second branch 132 the exhaust pipe 13 depending on the state of a first valve device 21 or a second valve device 22 in the respective branches 131 . 132 , The first branch 131 with the first valve device 21 when open, it is used for normal operating condition. When excess energy in the vehicle 1 is available, for example, because the fuel cell system 2 works at a higher level of performance than the vehicle 1 requested, for a time, which is needed to the performance level of the fuel cell 2 because it can not act as dynamically as it is often in demand by the vehicle, or especially when the vehicle regeneratively brakes. Such an excess of electrical energy typically becomes in an electrical energy storage device in the vehicle 1 saved. When the electrical energy storage device is fully charged, the excess energy that is generated in particular during regenerative braking is typically converted to heat at a resistor. In this situation, the vehicle according to the invention 1 now an auxiliary compressor 23 in the second branch 132 drive with this excess energy to the pressure of the exhaust gas in the second branch 132 to increase. Typically, the first branch 131 over the first valve device 21 closed while the second valve means 22 is open in such a situation. In addition, if the amount of available excess energy is greater than the amount required to compress the exhaust gas, air may be added from the environment of the auxiliary compressor 23 be compacted. In the figure, this is indicated by an additional suction line 24 , which may be equipped with a filter and a check valve to prevent exhaust gas through the intake pipe 24 gets into the environment. The compressed gas is then placed in a pressure tank 25 in the second branch 132 saved. The pressures typically used for the pressure tank 25 may be on the order of about 2 to 3 MPa. Via an outlet valve 26 can the pressure tank 25 with the exhaust gas turbine 27 or an additional auxiliary turbine of fuel cell system 2 get connected. When the exhaust valve 26 is opened, the compressed gas comes out of the pressure tank 25 to the exhaust gas turbine 27 and generates there mechanical energy in the exhaust gas turbine 27 , In the illustrated preferred embodiment of the vehicle 1 is the exhaust gas turbine 27 over a wave 28 with the air compressor 14 connected, as well as with an electric machine 29 , This arrangement of the air compressor 14 , the electric machine 29 and the exhaust gas turbine 27 is often referred to as an electric turbocharger or ETC. With the energy flowing through the exhaust gas turbine 27 can be recovered, the air compressor 14 be driven or at least the amount of energy required for the electric machine 29 , which is then operated as an electric motor to the air compressor 14 to be reduced.

When compressed gas in the pressure tank 25 stored, the extra energy can be used by the drain valve 26 is opened to the compressed gas from the pressure tank 25 for example, with the exhaust gas from the fuel cell stack 3 in the first branch 131 to mix. If there is a high power demand from the vehicle, for example, to perform an acceleration, the slow power dynamics of the fuel cell stack 3 be balanced by the use of stored energy in the pressure tank 25 , Compressed gas is added via the exhaust gas turbine 27 For example, it increases and increases the amount of air flowing to the fuel cell stack 3 is supplied. In addition, the compressed gas can be used to power the electric machine 29 over the exhaust gas turbine 27 which is then used as a generator to directly generate electrical energy.

At lower loads, the recovered energy is through the exhaust gas turbine 27 in the normal operating state relatively small due to the relatively small volume flow of exhaust gas. In this case, the extra energy from the pressure tank 25 by opening the exhaust valve 26 used to the exhaust gas turbine 27 to drive what the power consumption of the electric machine 29 reduced. In addition, this allows the exhaust gas turbine 27 to use at an operating point, which has a much higher efficiency compared to an operation with the relatively small exhaust gas volume flow of the fuel cell stack itself.

Even with a freeze start of the fuel cell system 2 The required power for the electric turbocharger can be made available by injecting compressed gas from the pressure tank 25 which has been previously loaded is used.

LIST OF REFERENCE NUMBERS

1 vehicle 2 The fuel cell system 3 fuel cell stack 4 cathode region 5 anode region 6 Compressed gas containers 7 Pressure control and dosing valve 8th Gas jet pump 9 recirculation 10 water 11 drain line 12 drain valve 13 exhaust pipe 131 first branch 132 second branch 14 air compressor 15 air supply 16 Intercooler 17 Gas / gas humidifier 18 system bypass 19 System bypass valve 20 branching point 21 first valve device 22 second valve device 23 auxiliary compressor 24 suction 25 pressure tank 26 outlet valve 27 exhaust turbine 28 wave 29 electric machine

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

• US 4759997 A [0002]
• DE 102015004718 A1 [0003]
• DE 102007007934 A1 [0004]

Claims (9)

Vehicle (1) having a fuel cell system (2) for providing electrical drive power, which comprises an air compressor (14) and an exhaust gas turbine (27) for recovering energy from the exhaust gas, which previously contains compressed air from the air compressor (14), which has an auxiliary compressor (23) for air and / or exhaust gas, and which has a pressure tank (25) for receiving air and / or exhaust gas from the auxiliary compressor (23), characterized in that the pressure tank (25) in one or in parallel to an exhaust pipe (13, 131, 132) upstream of an auxiliary turbine, with a switchable connection between the pressure tank (25) and the auxiliary turbine. Vehicle (1) to Claim 1 , characterized in that the exhaust gas turbine (27) is additionally designed as an auxiliary turbine. Vehicle (1) to Claim 1 or 2 , characterized in that the pressure tank (25) is positioned parallel to the exhaust pipe (13), wherein each of the two parallel branches (131, 132) at least one valve means (21, 22, 26). Vehicle (1) according to Claim 3 , characterized in that the at least two valve devices (21, 22) are integrated to form a 3/2-way valve at one of the branch points (20). Vehicle (1) according to one of Claims 1 to 4 , characterized in that the exhaust gas turbine (27) and the air compressor (14) are in operative connection with at least one electric machine (29). Method for using a vehicle (1) according to one of the Claims 1 to 5 wherein braking of the vehicle is performed by using an electric drive motor as a generator, wherein the recovered energy is stored in an electrical energy storage device, and wherein at least a portion of the recovered energy is stored in the pressure tank (25) by the auxiliary compressor (23 ) is driven with at least a portion of the recovered energy. Method according to Claim 6 , characterized in that the distribution of the recovered energy between the electrical energy storage device and the auxiliary compressor based on the state of charge of the electrical energy storage device and / or the pressure in the pressure tank (25). Method according to Claim 7 characterized in that, at least when the electrical energy storage device is fully charged, the recovered energy is used to drive the auxiliary compressor (23) to fill the pressure tank (25). Method according to one of Claims 6 to 8th characterized in that the compressed gas in the pressure tank (25) is directed to the auxiliary turbine when additional energy is needed to drive the air compressor (14).

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