JP7298430B2 - fuel cell system - Google Patents

Description

The present invention relates to fuel cell systems.

Assuming that the operating point of the turbo compressor falls within the surging region, which is determined by the air flow rate and air pressure required for the fuel cell to generate the target electric power, the operating point of the turbo compressor does not fall within the surging region. The fuel cell system gradually reduces the rotation speed of the turbo compressor and controls the valve opening of the flow control valve so that surplus air generated by the gradual reduction of the rotation speed of the turbo compressor is discharged through the bypass passage. Are known.

A conventional fuel cell system includes a pressure gauge for measuring the pressure on the discharge side of the turbo compressor and a flow meter for measuring the flow rate of air supplied to the fuel cell. Conventional fuel cell systems determine the operating point of a turbocompressor based on pressure gauge measurements and flow meter measurements. Then, the conventional fuel cell system 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 for the fuel cell to generate the target power (for example, , see Patent Document 1).

Japanese Patent Application Laid-Open No. 2018-181771

A conventional fuel cell system requires a flow meter to determine whether the operating point of the turbocompressor enters the surging region.

However, if a flow meter is provided in the intake system of the fuel cell to determine whether the operating point of the turbo compressor falls within the surging region, the fuel cell system must have a required linear flow path before and after the flow meter. need. In addition, the channel in which the flowmeter is installed requires an appropriate channel cross-sectional area for installing the flowmeter. The need for these straight flow paths and the increase in cross-sectional area of the flow paths impede miniaturization of the fuel cell system.

Accordingly, 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 or not surging occurs in the compressor that supplies the oxidant gas to the fuel cell. aim.

In order to solve the above-described problems, a fuel cell system according to the present invention comprises: a fuel cell that generates electricity by reacting an oxidant gas and a fuel gas; a compressor that supplies air as the 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, and surging to the compressor from the measurement result of the input sensor and the measurement result of the rotation speed sensor. and a control unit for controlling the operation of the compressor so as to avoid the occurrence of surging in the compressor when occurrence of is estimated.

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.

1 is a configuration diagram of a fuel cell system according to an embodiment of the present invention; FIG. FIG. 4 is an example of a compressor map of a compressor in the fuel cell system according to the embodiment of the present invention, showing the relationship between the power supplied to the compressor and the discharge flow rate of the compressor; FIG. 4 is an example of a compressor map of the compressor in the fuel cell system according to the embodiment of the present invention, showing the relationship between the pressure ratio between the suction side pressure and the discharge side pressure of the compressor and the discharge flow rate of the compressor.

An embodiment of a fuel cell system according to the present invention will be described with reference to FIGS. 1 to 3. FIG. In addition, the same code|symbol is attached|subjected to the same or corresponding structure in several drawings.

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

A fuel cell system 1 according to the present embodiment includes a fuel cell 3 that generates power by reacting an oxidant gas and a fuel gas, an air supply passage 5 that supplies air as the oxidant gas to the fuel cell 3, a fuel cell 3, a storage tank 7 for storing hydrogen as fuel gas, a hydrogen supply passage 8 for supplying hydrogen from the storage tank 7 to the fuel cell 3, and a coolant for circulation. 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 are provided.

The fuel cell system 1 supplies 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 drive wheels. Motor 102 is connected to fuel cell 3 via inverter 103 .

The fuel cell 3 includes a large number of stacked fuel cells. Therefore, the fuel cell 3 is also called a fuel cell stack. The fuel cell 3 is used as a fuel cell stack in which tens to hundreds of fuel cells are stacked as a minimum unit.

The fuel cell 3 includes a plurality of stacked fuel cells, a pair of end plates that sandwich the stacked fuel cells from the outside, and fastening members that fix the pair of end plates to the stack of fuel cells. , is equipped with

Each fuel cell consists of a membrane electrode assembly (MEA) that integrates a fuel electrode (negative electrode), a solid polymer membrane (electrolyte), and an air electrode (positive electrode). and a pair of separators sandwiched between the separators, the separators having supply channels for reactant gases.

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

The air supply passage 5 is provided upstream 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 that has been compressed by the compressor 21 and heated to a high temperature.

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 feeds it into the air supply passage 5 . Compressor 21 is of turbo type. Intercooler 22 cools the air compressed by compressor 21 when the temperature of the air compressed by compressor 21 is too hot to supply fuel cell 3 .

The air discharge passage 6 is provided downstream 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 .

The hydrogen supply passage 8 is provided with a pressure reducing valve 25 for reducing the pressure of the hydrogen gas stored in the storage tank 7 to a pressure suitable as the fuel gas for the fuel cell 3 , and the hydrogen gas supplied from the storage tank 7 to the fuel cell 3 . A supply injector 26 and a purge valve 27 are provided. The hydrogen gas stored in the storage tank 7 is pressure-reduced by the pressure reducing valve 25 and supplied to the fuel cell 3 . The purge valve 27 exhausts fuel gas from the hydrogen supply passage 8 . This exhaust of the fuel gas prevents the concentration of the fuel gas from lowering due to the nitrogen that inevitably permeates the fuel cell from the oxidant supply channel as the power generation reaction continues, thereby stably continuing power generation. In addition, the exhaust of the fuel gas exhausts moisture generated by the reaction.

The air supplied to the fuel cell 3 from the air supply passage 5 is distributed to the cathode-side supply passages of the plurality of stacked fuel cells. The distributed air is discharged to the air discharge passage 6 after flowing along the cathode-side surface of each membrane electrode assembly.

The hydrogen supplied to the fuel cell 3 from the hydrogen supply passage 8 is distributed to the anode-side supply passages of the plurality of stacked fuel cells. The distributed hydrogen is discharged out of the fuel cell 3 after flowing along the anode-side surface of each membrane electrode assembly.

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

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 a 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 includes, for example, a central processing unit (CPU, not shown), various arithmetic programs executed (processed) by the central processing unit, an auxiliary storage device (for example, read only memory, ROM , not shown), and a main storage device (for example, random access memory, RAM, not shown) in which a program work area is dynamically secured.

The fuel cell system 1 includes various sensors required for intake and exhaust of air, which is an oxidant gas, reception and supply of hydrogen, which is 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 information acquired from these various sensors, and supplies power to the load 101 .

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

These various sensors also include a current sensor 43 that measures the current supplied to load 101 .

The control unit 11 is represented by 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.

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 the compressor in the fuel cell system according to the embodiment of the present invention.

The compressor map M includes a first map M1 representing the relationship between the power supplied to the compressor 21 and the discharge flow rate of the compressor 21 as shown in FIG. A second map M2 representing 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 is included.

As shown in FIG. 2, the first map M1 of the fuel cell system 1 according to the embodiment of the present invention shows power P supplied to the compressor 21 (hereinafter simply referred to as "power P") and compression and 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 discharge flow rate Q on the horizontal axis and the power P on the vertical axis.

Curves N1, N2, . A curve N2 far from the origin of the compressor map M represents a higher rotational speed than a curve N1 closer to the origin. Only 10 curves N1, N2, . information (multiple curves N).

Then, the intercept of 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 of the horizontal axis with respect to those intersections.

By the way, at each rotational 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 angular curve N). In a 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 area from the flow rate at which the 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, the efficiency of the electric power P supplied to the compressor 21 is high in the region where the electric power P supplied to the compressor 21 reaches the maximum value at each rotational speed N. Therefore, the compressor 21 is operated in an upward-sloping region. In this region, there is a one-to-one correspondence between the power P and the discharge flow rate Q.

That is, the fuel cell system 1 can uniquely estimate the discharge flow rate Q of the operating compressor 21 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 commanding the target rotation speed to the compressor 21, it takes, for example, about 0.5 seconds for the actual rotation speed N of the compressor 21 to reach the target rotation speed. , the electric power P and the rotation speed N are measured after a time has passed in which it is assumed that the actual rotation speed N of the compressor 21 is stabilized from the command of the target rotation speed.

Next, as shown in FIG. 3, the second map M2 of the fuel cell system 1 according to the embodiment of the present invention is a pressure ratio R between the suction side pressure and the discharge side pressure of the compressor 21 (hereinafter simply referred to as "pressure 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 discharge flow rate Q on the horizontal axis and the pressure ratio R on the vertical axis.

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

The discharge flow rate Q at which surging occurs varies according to the rotational speed N of the compressor 21 . A point corresponding to the discharge flow rate at which surging occurs on the second map M2 when the compressor 21 is operated at a certain rotation speed N is called a surge limit point. A curve connecting surge limit points that change according to the rotation speed N of the compressor 21 is represented by a surge limit line α. In the second map M2, the intersections of the respective curves N1, N2, . be.

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

Surging of the compressor 21 may occur, for example, when moisture in the air as the oxidant gas condenses in the oxidant gas supply path in the fuel cell 3 beyond assumption. When the moisture in the air condenses in the oxidant gas supply channel in the fuel cell 3, the channel cross-sectional area of the supply channel decreases. When the cross-sectional area of the flow path 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 increases, the pressure ratio R increases, and surging may occur.

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

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 . Also, 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 surging is occurring in the compressor 21 or not.

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

Since the pressure ratio R does not play a substantial role in the execution of 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 causes the compressor 21 to compress so as to avoid the occurrence of surging. control the operation of the machine 21; In other words, if 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 control unit 11 controls the surging of the compressor 21. The operation of the compressor 21 is controlled to avoid the occurrence of

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

If surging is not resolved even by increasing the opening of the pressure regulating valve 23 , 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 oxidizing gas reduces the humidity in the flow path of the oxidizing gas. This reduces the condensation of water in the flow path, thereby reducing the resistance and lowering the pressure at the oxidant gas inlet of the fuel cell, further increasing the flow rate of the oxidant gas. Then, when the operating point of the compressor 21 reaches a region A2 on the large flow rate side of the surge limit line α, the compressor 21 stabilizes.

Further, when the surging is not eliminated even by increasing the opening of the pressure regulating valve 23, the control unit 11 stops the blower 32 to raise the operating temperature of the fuel cell 3. FIG. When the blower 32 is stopped, 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 the air as the oxidant gas decreases, and the moisture condensation rate in the reaction gas supply passage within the fuel cell 3 decreases. As a result, air can be well circulated in the oxidant gas supply path in the fuel cell 3, and surging can be eliminated.

As described above, the fuel cell system 1 according to this embodiment determines whether or not surging is occurring in the compressor 21 based on 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 flowmeter that directly measures the discharge flow rate Q of the compressor 21 . In other words, the fuel cell system 1 does not require a required straight 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 made smaller than when a flow meter is required.

In addition, in the fuel cell system 1 according to the present embodiment, 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 surging occurs in the compressor 21. Control the operation of the compressor 21 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 flowmeter 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. to increase the flow rate of the oxidant gas sucked into the compressor 21. Therefore, the fuel cell system 1 according to this embodiment can reliably prevent surging of the compressor 21 .

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

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

REFERENCE SIGNS LIST 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 controller 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 Revolution sensor , 43...Current sensor, 46...Storage unit, 101...Load, 102...Motor, 103...Inverter.

Claims (4)

a fuel cell that generates electricity by reacting an oxidant gas and a fuel gas;
a compressor that supplies air as an oxidant gas to the fuel cell;
an input sensor that measures power supplied to the compressor;
a rotation speed sensor for measuring the rotation speed of the compressor;
When the occurrence of surging in the compressor is estimated 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 comprising a controller. 2. The fuel cell system according to claim 1, wherein the control unit has a compressor map for setting a surging region in which surging is estimated to occur in the compressor based on the relationship between the electric power and the rotational speed. A pressure regulating valve provided downstream of the fuel cell in the flow of the oxidant gas,
When surging is estimated to occur in the compressor, the control unit increases the degree of opening of the pressure regulating valve to reduce the pressure of the oxidant gas supplied to the fuel cell, thereby reducing the pressure of the oxidizing gas to the compressor. 3. The fuel cell system according to claim 1, wherein the flow rate of the sucked oxidant gas is increased. a radiator that dissipates heat from a coolant that cools the fuel cell;
and a blower for blowing cooling air to the radiator,
4. The fuel cell according to any one of claims 1 to 3, wherein when surging is estimated to occur in the compressor, the control unit stops the blower to raise the operating temperature of the fuel cell. system.

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