JP2021061213A - Fuel cell system - Google Patents

Abstract

To provide a fuel cell system requiring no flow meter for a fuel cell intake system in order to determine whether or not surging occurs in a compressor that supplies oxidant gas to the fuel cell.SOLUTION: A fuel cell system 1 includes: a fuel cell 3 generating electricity by reacting oxidant gas and fuel gas; a compressor 21 supplying air, as the oxidant gas, to the fuel cell 3; an input sensor 41 measuring power supplied to the compressor 21; a rotation speed sensor 42 measuring the rotation speed of the compressor 21; and a controller 11 controlling the operation of the compressor 21 such that the occurrence of surging in the compressor 21 is avoided, in the case where the occurrence of surging in the compressor 21 is estimated from the measurement results of the input sensor 41 and the measurement results of the rotation speed sensor 42.SELECTED DRAWING: Figure 1

Description

The present invention relates to a fuel cell system.

Assuming that the operating point of the turbo compressor is within the surging region, which is determined by the air flow rate and air pressure required for the fuel cell to generate the target power, the operating point of the turbo compressor should not be within the surging region. , A fuel cell system that controls the valve opening of the flow control valve so that the turbo compressor rotation speed is gradually reduced and excess air generated by the turbo compressor rotation speed is discharged through the bypass flow path. Are known.

A conventional fuel cell system includes a pressure gauge that measures the pressure on the discharge side of the turbo compressor and a flow meter that measures the flow rate of air supplied to the fuel cell. In the conventional fuel cell system, the operating point of the turbo compressor is determined based on the measurement result of the pressure gauge and the measurement result of the flow meter. The conventional fuel cell system then estimates whether the operating point of the turbo compressor falls within the surging region, which is determined by the air flow rate and air pressure required of the fuel cell to generate the target power (eg,). , Patent Document 1).

Japanese Unexamined Patent Publication No. 2018-181771

Conventional fuel cell systems require a flow meter to determine if the operating point of the turbo compressor is in the surging region.

However, when a flow meter is provided in the intake system of the fuel cell to determine whether the operating point of the turbo compressor is in the surging region, the fuel cell system requires a linear flow path before and after the flow meter. Needs. Further, the flow path provided with the flow meter requires an appropriate flow path cross-sectional area for installing the flow meter. The need for these linear flow paths and the increase in the cross-sectional area of the flow paths hinder the miniaturization of fuel cell systems.

Therefore, the present invention proposes a fuel cell system that does not require a flow meter in the intake system of the fuel cell in order to determine whether surging occurs in the compressor that supplies the oxidant gas to the fuel cell. The purpose.

In order to solve the above problems, the fuel cell system according to the present invention includes a fuel cell that generates power by reacting an oxidizing agent gas with a fuel gas, a compressor that supplies air as an oxidizing agent gas to the fuel cell, and a compressor. An input sensor that measures the power supplied to the compressor, a rotation speed sensor that measures the rotation speed of the compressor, a measurement result of the input sensor, and a surging to the compressor from the measurement result of the rotation speed sensor. When the occurrence of the compressor is presumed, the compressor is provided with a control unit that controls the operation of the compressor so as to avoid the occurrence of surging.

According to the present invention, it is possible to provide a fuel cell system that does not require a flow meter in the intake system of the fuel cell in order to determine whether or not surging occurs in the compressor that supplies the oxidant gas to the fuel cell.

The block diagram of the fuel cell system which concerns on embodiment of this invention. It is an example of the compressor map of the compressor in the fuel cell system which concerns on embodiment of this invention, and is the figure which shows the relationship between the electric power supplied to a compressor, and the discharge flow rate of a compressor. It is an example of the compressor map of the compressor in the fuel cell system which concerns on embodiment of this invention, and is the figure which shows the relationship between the pressure ratio of the suction side pressure and the discharge side pressure of a compressor, and the discharge flow rate of a compressor.

An embodiment of the fuel cell system according to the present invention will be described with reference to FIGS. 1 to 3. In the plurality of drawings, the same or corresponding configurations are designated by the same reference numerals.

FIG. 1 is a block diagram of a fuel cell system according to an embodiment of the present invention.

The fuel cell system 1 according to the present embodiment includes a fuel cell 3 that generates power by reacting an oxidizing agent gas with a fuel gas, an air supply passage 5 that supplies air as an oxidizing agent gas to the fuel cell 3, and a fuel cell. An air discharge passage 6 for discharging the air used for the power generation reaction from 3 and a storage tank 7 for storing hydrogen as a fuel gas, a hydrogen supply passage 8 for supplying hydrogen from the storage tank 7 to the fuel cell 3, and a refrigerant are circulated. It includes a fuel cell cooling passage 9 for cooling the fuel cell 3 and a control unit 11 for controlling the operation of the fuel cell system 1.

The fuel cell system 1 supplies the electric power generated by the fuel cell 3 to the load 101. For example, when the fuel cell system 1 is mounted on a vehicle, the load 101 includes a motor 102 that drives the drive wheels. The motor 102 is connected to the fuel cell 3 via the inverter 103.

The fuel cell 3 includes a large number of stacked fuel cell cells. Therefore, the fuel cell 3 is also called a fuel cell stack. The fuel cell 3 has a fuel cell as the smallest unit, and is used as a fuel cell stack in which dozens to hundreds of these fuel cell cells are stacked.

The fuel cell 3 includes a plurality of stacked fuel cell cells, a pair of end plates that sandwich the stacked fuel cell cells from the outside, and a fastening member that fixes the pair of end plates to the laminated body of the fuel cell cells. , Is equipped.

Each fuel cell has a membrane electrode assembly ((Membrane Electrode Assembly, MEA)) that integrates a fuel electrode (negative electrode), a solid polymer film (electrolyte), and an air electrode (positive electrode), and a membrane electrode assembly on the front and back. It includes a pair of separators sandwiched from the assembly. The separator has a reaction gas supply path.

Oxidizing agent gas and fuel gas are supplied to each fuel cell as reaction gases. These oxidant gas and fuel gas react with each other across the membrane electrode assembly to generate a voltage in each fuel cell. The sum of the voltages generated in each fuel cell is the output voltage of the fuel cell 3.

The air supply passage 5 is provided on the upstream side of the fuel cell 3 in the flow of the oxidant gas. The air supply passage 5 is provided with a compressor 21 that supplies air as an oxidant gas to the fuel cell 3 and an intercooler 22 that cools the air compressed by the compressor 21 and becomes hot.

The compressor 21 and the intercooler 22 are arranged in order from the upstream side to the downstream side of the air supply passage 5. The compressor 21 compresses the sucked air and sends it into the air supply passage 5. The compressor 21 is a turbo type. The intercooler 22 cools the air compressed by the compressor 21 when the temperature of the air compressed by the compressor 21 is too high to supply to the fuel cell 3.

The air discharge passage 6 is provided on the downstream side of the fuel cell 3 in the flow of the oxidant gas. The air discharge passage 6 is provided with a pressure regulating valve 23 as a back pressure valve. The pressure regulating valve 23 can change the pressure loss on the exhaust side of the fuel cell 3 to change the flow rate of the air flowing through the fuel cell 3.

In the hydrogen supply passage 8, a pressure reducing valve 25 that lowers the pressure of the hydrogen gas stored in the storage tank 7 to a pressure suitable as the fuel gas of the fuel cell 3 and a hydrogen gas supplied from the storage tank 7 are sent to the fuel cell 3. An injector 26 for supplying and a purge valve 27 are provided. The hydrogen gas stored in the storage tank 7 is stepped down by the pressure reducing valve 25 and supplied to the fuel cell 3. The purge valve 27 exhausts the fuel gas from the hydrogen supply passage 8. The exhaust of the fuel gas prevents a decrease in the concentration of the fuel gas due to nitrogen that inevitably permeates the fuel cell from the supply path of the oxidant with the continuation of the power generation reaction, and the power generation is stably continued. In addition, the exhaust of fuel gas discharges the water generated by the reaction.

The air supplied from the air supply passage 5 to the fuel cell 3 is distributed to the supply path on the cathode side of each of the plurality of stacked fuel cell cells. The distributed air flows through the plane on the cathode side of each membrane electrode assembly, and then is discharged to the air discharge passage 6.

The hydrogen supplied from the hydrogen supply passage 8 to the fuel cell 3 is distributed to the supply path on the anode side of each of the plurality of stacked fuel cell cells. The distributed hydrogen flows through the plane on the anode side of each membrane electrode assembly, and then is discharged to the outside of the fuel cell 3.

The fuel cell cooling passage 9 is provided with a radiator 31 that dissipates heat from the refrigerant that cools the fuel cell 3, a blower 32 that ventilates the cooling air through the radiator 31, and a pump 33 that circulates the refrigerant.

The control unit 11 is a so-called ECM (Engine Control Module). The control unit 11 is connected to the fuel cell 3, the compressor 21, and the pressure regulating valve 23 via the signal line 35. The control unit 11 controls the operation of the fuel cell 3, the compressor 21, and the pressure regulating valve 23, or issues an operation command. The control unit 11 may include operation control of the load 101.

The control unit 11 is, for example, an auxiliary storage device (for example, Read Only Memory, ROM) that stores a central processing unit (Central Processing Unit, CPU, not shown), various arithmetic programs executed (processed) by the central processing unit, parameters, and the like. , Not shown), and a main storage device (for example, Random Access Memory, RAM, not shown) that dynamically allocates a work area for a program.

The fuel cell system 1 has various sensors required for intake and exhaust of air as an oxidant gas, acceptance and supply of hydrogen as a fuel gas, and operation control of the fuel cell 3, the compressor 21, and the pressure regulating valve 23. It has. The control unit 11 controls the operation of the fuel cell system 1 based on the information acquired from these various sensors, and supplies electric power to the load 101.

These various sensors include, for example, an input sensor 41 for measuring the electric power supplied to the compressor 21, and a rotation speed sensor 42 for measuring the rotation speed of the compressor 21.

In addition, these various sensors include a current sensor 43 that measures the current supplied to the load 101.

The control unit 11 is expressed by the relationship between the power supplied to the compressor 21, the discharge flow rate of the compressor 21, the pressure ratio between the suction side pressure and the discharge side pressure of the compressor 21, and the rotation speed of the compressor 21. A storage unit 46 for storing a map, a so-called compressor map M, is provided.

Here, first, the compressor map M stored in the storage unit 46 of the control unit 11 will be described.

2 and 3 are examples of compressor maps of compressors in the fuel cell system according to the embodiment of the present invention.

The compressor map M is a first map M1 showing the relationship between the power supplied to the compressor 21 and the discharge flow rate of the compressor 21 as shown in FIG. 2, and a compressor as shown in FIG. Includes a second map M2 showing the relationship between the pressure ratio between the suction side pressure and the discharge side pressure of 21 and the discharge flow rate of the compressor 21.

As shown in FIG. 2, the first map M1 of the fuel cell system 1 according to the embodiment of the present invention includes electric power P supplied to the compressor 21 (hereinafter, simply referred to as “electric power P”) and compression. It is expressed in relation to the discharge flow rate Q of the machine 21 (hereinafter, simply referred to as “discharge flow rate Q”). The first map M1 can be visually represented by a graph having two orthogonal axes, with the horizontal axis representing the discharge flow rate Q and the vertical axis representing the electric power P.

The curves N1, N2, ..... described in the compressor map M correspond to the rotation speed N of the compressor 21. The curve N2 far from the origin represents a higher rotation speed than the curve N1 near the origin of the compressor map M. Curves N1, N2, ..... are shown only for convenience of representation in the drawing, but the actual first map M1 is more precise between each curve N according to the number of rotations N. Information (plurality of curves N) is included.

Then, the intercept on the vertical axis is determined based on the measurement result of the input sensor 41, and the curve N, that is, the rotation speed N is determined based on the measurement result of the rotation speed sensor 42. Then, the discharge flow rate Q of the compressor 21 in operation can be estimated based on the intercept on the horizontal axis with respect to those intersections.

By the way, at each rotation speed N, the electric power P supplied to the compressor 21 takes the maximum value at a flow rate slightly smaller than the maximum flow rate (the right end of the angle curve N). In the region exceeding this flow rate and up to the maximum flow rate, the efficiency of the electric power P supplied to the compressor 21 decreases. Therefore, the region from the flow rate at which the electric power P supplied to the compressor 21 takes the maximum value to the maximum flow rate is not suitable for the operation of the compressor 21. On the other hand, at each rotation speed N, the efficiency of the electric power P supplied to the compressor 21 is high in the region rising to the right, that is, in the region until the electric power P supplied to the compressor 21 reaches the maximum value. Therefore, the compressor 21 is operated in the region rising to the right. In this region, the relationship between the electric power P and the discharge flow rate Q has a one-to-one correspondence.

That is, the fuel cell system 1 can uniquely estimate the discharge flow rate Q of the compressor 21 during operation from the first map M1, the measurement result of the input sensor 41, and the measurement result of the rotation speed sensor 42. Therefore, the fuel cell system 1 does not require a flow rate sensor for measuring the discharge flow rate Q of the compressor 21.

However, after instructing the compressor 21 to the target rotation speed, it takes about 0.5 seconds, for example, for the actual rotation speed N of the compressor 21 to reach the target rotation speed (comment; it is described appropriately). Therefore, the electric power P and the rotation speed N are measured after a time has elapsed from the command of the target rotation speed that the actual rotation speed N of the compressor 21 is estimated to be stable.

Next, as shown in FIG. 3, the second map M2 of the fuel cell system 1 according to the embodiment of the present invention has a pressure ratio R (hereinafter, simply "pressure") between the suction side pressure and the discharge side pressure of the compressor 21. It is expressed by the relationship between the ratio R) and the discharge flow rate Q. The second map M2 can be visually represented by a graph having two orthogonal axes, with the horizontal axis representing the discharge flow rate Q and the vertical axis representing the pressure ratio R.

The second map M2 has a surge limit line α that separates the region A1 where surging occurs and the region A2 where surging does not occur in the compressor 21.

The discharge flow rate Q at which surging occurs changes according to the rotation speed N of the compressor 21. When the compressor 21 is operated at a certain rotation speed N, the point corresponding to the discharge flow rate at which surging occurs on the second map M2 is called a surge limit point. A curve connecting each surge limit point that changes according to the rotation speed N of the compressor 21 is represented by the surge limit line α. In the second map M2, the intersection of the respective curves N1, N2, ..... and the surge limit line α is the surge limit point at the rotation speed N represented by the respective curves N1, N2, ..... is there.

The region A1 on the small flow rate side (left side in FIG. 2) with respect to the surge limit line α is a surging region where surging occurs. The region A2 on the large flow rate side (right side in FIG. 2) with respect to the surge limit line α is a stable region where surging does not occur.

Note that surging of the compressor 21 may occur, for example, when the moisture in the air as the oxidant gas condenses more than expected in the supply path of the oxidant gas in the fuel cell 3. When the moisture in the air is condensed in the supply path of the oxidant gas in the fuel cell 3, the cross-sectional area of the flow path of the supply path is reduced. When the flow path cross-sectional area decreases, the discharge flow rate Q of the compressor 21 decreases, and the discharge pressure of the compressor 21 increases. Then, while the suction pressure of the compressor 21 does not change, the discharge pressure of the compressor 21 becomes high, the pressure ratio R increases, and surging may occur.

Further, the operating point of the compressor 21 is described by the discharge flow rate Q of the compressor 21 during operation, the pressure ratio R, and the rotation speed N of the compressor 21. That is, the operating points are the discharge flow rate Q of the compressor 21, the pressure ratio R, and the rotation speed of the compressor 21 estimated from the measurement results of the first map M1, the input sensor 41, and the rotation speed sensor 42. It is described by N.

Here, the discharge flow rate Q of the compressor 21 can be estimated from the first map M1, the measurement result of the input sensor 41, and the measurement result of the rotation speed sensor 42. Further, the rotation speed N of the compressor 21 can be known from the measurement result of the rotation speed sensor 42. Since the relationship between the discharge flow rate Q and the rotation speed N is uniquely determined, the operating point of the compressor 21 is determined even if the pressure ratio R in the second map M2 is unknown. Then, it can be determined whether the operating point of the compressor 21 belongs to the region A1 or the region A2. That is, even if the pressure ratio R in the second map M2 is unknown, it is possible to estimate whether or not surging has occurred in the compressor 21.

As described above, the control unit 11 has the compressor map M stored in the storage unit 46, the measurement result of the input sensor 41, that is, the power P supplied to the compressor 21, and the measurement result of the rotation speed sensor 42, that is, compression. Based on the rotation speed N of the machine 21, it is estimated whether or not surging has occurred in the compressor 21.

Since the pressure ratio R does not have a substantial role in executing the control, the second map M2 may be described only by the relationship between the rotation speed N and the discharge flow rate Q.

Then, when the occurrence of surging in the compressor 21 is estimated from the measurement result of the input sensor 41 and the measurement result of the rotation speed sensor 42, the control unit 11 compresses the compressor 21 so as to avoid the occurrence of surging. Controls the operation of the machine 21. In other words, the control unit 11 surges to the compressor 21 when the operating point of the compressor 21 in the compressor map M belongs to the region A1 from the measurement result of the input sensor 41 and the measurement result of the rotation speed sensor 42. The operation of the compressor 21 is controlled so as to avoid the occurrence of the above.

Specifically, the control unit 11 increases the opening degree of the pressure regulating valve 23, reduces the pressure of the oxidant gas supplied to the fuel cell 3, and increases the flow rate of the oxidant gas sucked into the compressor 21. Then, the operating point of the compressor 21 moves toward the larger discharge flow rate Q (to the right of FIGS. 2 and 3, the larger flow rate side) in the compressor map M. Then, when the operating point of the compressor 21 reaches the region A2 on the large flow rate side of the surge limit line α, the compressor 21 becomes stable.

If surging is not resolved even if the opening degree of the pressure regulating valve 23 is increased, the control unit 11 increases the rotation speed N of the compressor 21 to increase the flow rate of the oxidant gas sucked into the compressor 21. Increasing the flow rate of the oxidant gas reduces the humidity in the flow path of the oxidant gas. As a result, the condensation of water in the flow path is reduced, the resistance is reduced, the pressure at the oxidant gas inlet of the fuel cell is lowered, and the flow rate of the oxidant gas is further increased. Then, when the operating point of the compressor 21 reaches the region A2 on the large flow rate side of the surge limit line α, the compressor 21 becomes stable.

If surging is not resolved even if the opening degree of the pressure regulating valve 23 is increased, the control unit 11 stops the blower 32 to raise the operating temperature of the fuel cell 3. When the blower 32 is stopped, the cooling of the refrigerant in the radiator 31 becomes insufficient, and the operating temperature of the fuel cell 3 rises. When the operating temperature of the fuel cell 3 rises, the relative humidity of air as an oxidant gas decreases, and the concentration rate of water in the reaction gas supply path in the fuel cell 3 decreases. Then, air satisfactorily circulates in the supply path of the oxidant gas in the fuel cell 3, and surging is eliminated.

As described above, the fuel cell system 1 according to the present embodiment determines whether or not surging has occurred in the compressor 21 from the measurement result of the input sensor 41 and the measurement result of the rotation speed sensor 42. Therefore, the fuel cell system 1 does not require a flow meter that directly measures the discharge flow rate Q of the compressor 21. That is, the fuel cell system 1 does not require the required linear flow path for installing the flow meter, and does not require an appropriate flow path cross-sectional area for installing the flow meter. That is, the fuel cell system 1 can be miniaturized as compared with the case where a flow meter is required.

Further, in the fuel cell system 1 according to the present embodiment, when it is estimated that surging occurs in the compressor 21 from the measurement result of the input sensor 41 and the measurement result of the rotation speed sensor 42, the compressor 21 is subjected to surging. The operation of the compressor 21 is controlled so as to avoid the occurrence. Therefore, the fuel cell system 1 can continue to appropriately supply air as an oxidant to the fuel cell 3.

Further, the fuel cell system 1 according to the present embodiment has a compressor map M that sets a surging region A1 in which surging is estimated to occur in the compressor 21 based on the relationship between the electric power P and the rotation speed N. There is. Therefore, the fuel cell system 1 does not require a flow meter that directly measures the discharge flow rate Q of the compressor 21.

Further, in the fuel cell system 1 according to the present embodiment, when surging is estimated to occur in the compressor 21, the opening degree of the pressure regulating valve 23 is increased to increase the pressure of the oxidant gas supplied to the fuel cell 3. It is reduced to increase the flow rate of the oxidant gas sucked into the compressor 21. Therefore, the fuel cell system 1 according to the present embodiment can surely prevent surging of the compressor 21.

Further, in the fuel cell system 1 according to the present embodiment, when surging is estimated to occur in the compressor 21, the blower 32 is stopped to raise the operating temperature of the fuel cell 3. Therefore, the fuel cell system 1 according to the present embodiment can more reliably prevent surging of the compressor 21.

Therefore, according to the fuel cell system 1 according to the present invention, a flow meter is installed in the intake system of the fuel cell 3 in order to determine whether or not surging occurs in the compressor 21 that supplies the oxidant gas to the fuel cell 3. Does not need.

1 ... Fuel cell system, 3 ... Fuel cell, 5 ... Air supply passage, 6 ... Air discharge passage, 7 ... Storage tank, 8 ... Hydrogen supply passage, 9 ... Fuel cell cooling passage, 11 ... Control unit, 21 ... Compressor, 22 ... Intercooler, 23 ... Pressure regulating valve, 25 ... Pressure reducing valve, 26 ... Injector, 27 ... Purge valve, 31 ... Radiator, 32 ... Blower, 33 ... Pump, 35 ... Signal line, 41 ... Input sensor, 42 ... Rotation speed sensor , 43 ... Current sensor, 46 ... Storage unit, 101 ... Load, 102 ... Motor, 103 ... Injector.

Claims (4)

A fuel cell that generates electricity by reacting an oxidant gas with a fuel gas,
A compressor that supplies air as an oxidant gas to the fuel cell,
An input sensor that measures the power supplied to the compressor,
A rotation speed sensor that measures the rotation speed of the compressor,
When the occurrence of surging is estimated in the compressor from the measurement result of the input sensor and the measurement result of the rotation speed sensor, the operation of the compressor is controlled so as to avoid the occurrence of surging in the compressor. A fuel cell system with a control unit. The fuel cell system according to claim 1, wherein the control unit has a compressor map that sets a surging region in which the occurrence of surging is estimated in the compressor based on the relationship between the electric power and the rotation speed. A pressure regulating valve provided on the downstream side of the fuel cell in the flow of the oxidant gas is provided.
When surging is presumed to occur in the compressor, the control unit increases the opening degree of the pressure regulating valve and reduces the pressure of the oxidant gas supplied to the fuel cell to the compressor. The fuel cell system according to claim 1 or 2, wherein the flow rate of the oxidant gas sucked in is increased. A radiator that dissipates heat from the refrigerant that cools the fuel cell,
The radiator is provided with a blower that allows cooling air to pass through.
The fuel cell according to any one of claims 1 to 3, wherein the control unit stops the blower to raise the operating temperature of the fuel cell when surging is presumed to occur in the compressor. system.

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