Zero-power output method for fuel-electricity system of fuel cell engine system

Abstract

The invention discloses a zero-power output method for a fuel-electricity system of a fuel cell engine system. The bypass branch is arranged between the air inlet pipeline and the air tail exhaust pipeline, the bypass valve is arranged on the bypass branch, and therefore when the lithium battery is sufficient and does not need to be charged, the fuel-electricity system is subjected to load reduction to be in the idling working condition and is switched to be in the zero output state, the bypass valve is opened, and the fuel-electricity system can be charged. The generating capacity of the gas-electricity system is consumed by increasing the rotating speed of the air compressor, and the excessive air entering the gas-electricity system is discharged through the bypass branch when the rotating speed of the air compressor is increased, so that the gas-electricity system is not shut down, the start-stop frequency of the gas-electricity system is greatly reduced, and the performance attenuation of the gas-electricity system is slowed down.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cells, and in particular relates to a zero-power output method for a fuel cell engine system. Background Art

[0002] Fuel cell vehicles use fuel cell engines as their power source, in which the fuel cell stack (fuel electricity) is used to generate electricity. The electricity generated by the fuel cell stack is stored in lithium batteries (lithium batteries), which drive the vehicle and directly supply power to other power systems.

[0003] For example, an invention application with publication number CN111114532A discloses a control method for a fuel cell vehicle and a vehicle controller, the method comprising: receiving a trigger instruction of a hybrid mode switch; obtaining the allowable continuous charging power of the power battery; if the allowable continuous charging power is greater than or equal to the idle power generation power of the fuel cell engine, starting the fuel cell engine; if the allowable continuous charging power is less than the idle power generation power and the power battery is in a heating state, obtaining the heating power; if the sum of the heating power and the allowable continuous charging power is greater than or equal to the idle power generation power, starting the fuel cell engine; determining whether the fuel cell engine meets the preset shutdown conditions; and if the fuel cell engine meets the preset shutdown conditions, stopping the fuel cell engine.

[0004] During the operation of the vehicle, the lithium battery drives the motor. Usually, when the lithium battery SOC is less than 80%, the fuel-electric engine starts to charge the lithium battery. When the lithium battery SOC is greater than or equal to 80%, the fuel-electric engine shuts down. Repeated start and stop operations will cause irreversible performance degradation to the fuel-electric engine.

[0005] Start-stop is a special operating condition that triggers abnormal reactions in fuel cells. The main reason for the accelerated attenuation of fuel cells is the high cathode interface potential difference (up to 1.5V) caused by the anode hydrogen / air interface. Under start-stop conditions, the carbon carrier that constitutes the main framework of the catalytic layer will be severely corroded, which will in turn affect the Pt catalyst and ionomer. In addition, the structure of the cathode catalytic layer will change or even collapse, reducing the electrochemical active area and increasing the charge transfer resistance and mass transfer resistance. In addition, as an integral part of the start-stop condition, low-temperature start-up and its freezing / thawing cycle also have a significant impact on key battery materials and durability.

[0006] Therefore, reducing the number of starts and stops of fuel-fired power plants is of great significance to the protection of fuel-fired power plants.

[0007] The invention application with publication number CN115959012A discloses a start-stop control method, device, vehicle and storage medium for a fuel cell engine, the method comprising: when the vehicle does not need fuel cell power supply, obtaining the current operating condition type of the vehicle and the current SOC value of the power battery; matching the minimum operating time of the fuel cell according to the current operating condition and the current SOC value; after the fuel cell is turned on, when the vehicle no longer needs fuel cell power supply and the continuous operating time of the fuel cell reaches the minimum operating time, stop the fuel cell power supply, otherwise control the fuel cell to continue to supply power until the continuous operating time reaches the minimum operating time. However, the prior art only appropriately reduces the number of fuel cell starts and stops under different operating conditions by optimizing control, and there is still room for further improvement. Summary of the invention

[0008] The present invention aims at the above technical problems existing in the prior art and provides a method for zero power output of the fuel-electric system of a fuel cell engine system. The method reduces the number of starts and stops, and consumes excess electric energy through an air compressor to achieve zero power output of the fuel-electric system.

[0009] The present invention first provides a hydrogen fuel cell system, comprising a fuel cell stack, an air intake pipeline for supplying air to the fuel cell stack, and an air tail exhaust pipeline for exhausting cathode tail exhaust from the fuel cell stack, wherein an air compressor is provided on the air intake pipeline, a first air flow meter is provided upstream of the air compressor, a back pressure valve is provided on the air tail exhaust pipeline, a bypass branch is provided between the air intake pipeline and the air tail exhaust pipeline, a bypass valve is provided on the bypass branch, and a second air flow meter is provided downstream of the bypass valve; A tail exhaust pipe is provided on the air tail exhaust pipeline downstream of the back pressure valve, the upstream end of the bypass branch is connected to the air intake pipeline downstream of the air compressor, and the downstream end of the bypass branch is connected to the tail exhaust pipe on the air tail exhaust pipeline.

[0010] Preferably, the air intake pipeline is further provided with an intercooler and a shut-off valve, the intercooler is located downstream of the air compressor, and the shut-off valve is located downstream of the intercooler; The upstream end of the bypass branch is connected to the air intake pipeline and is located between the intercooler and the shut-off valve.

[0011] Further preferably, a purge branch connected to the outer frame of the fuel cell stack is provided on the air intake pipeline between the intercooler and the shut-off valve.

[0012] Further preferably, the air intake pipeline is further provided with a first pressure sensor and a first temperature sensor downstream of the stop valve; The air tail exhaust pipeline is provided with a second pressure sensor and a second temperature sensor upstream of the back pressure valve.

[0013] Preferably, the air intake pipeline is provided with an air filter upstream of the first air flow meter, and the air intake pipeline is also provided with an ambient temperature sensor between the air filter and the first air flow meter.

[0014] Preferably, the bypass branch is further provided with a muffler downstream of the tail exhaust pipe.

[0015] The present invention further provides a zero-power output method of a fuel cell engine system, wherein the fuel cell engine system comprises a fuel cell system and a lithium battery, wherein the fuel cell system is the hydrogen fuel cell system. When the lithium battery SOC is ≥80%, the fuel-electric system is deloaded to the idle condition, the fuel-electric system is switched to zero output state, and the lithium battery is not charged; the air compressor speed is increased to increase the power consumption of the air compressor, the bypass valve is opened, and the excess air flow is discharged through the bypass branch by adjusting the opening of the back pressure valve and the bypass valve, ensuring that the flow rate and pressure of the stack are consistent with the idle condition. That is, under the idle condition, the air compressor is used to consume the power generated at idle, so that the fuel-electric system is not shut down and the lithium battery is not charged.

[0016] Preferably, the speed of the air compressor is increased to a level where the net output power of the fuel-electric system is ≤ 0.5 kW.

[0017] The present invention provides a bypass branch between the air intake pipeline and the air tail exhaust pipeline, and the bypass branch is provided with a bypass valve, so that when the lithium battery has sufficient power and does not need to be charged, the fuel-electric system can be unloaded to an idle condition and switched to a zero output state, and the bypass valve can be opened to consume the power generated by the fuel-electric system by increasing the speed of the air compressor, and the excess air that enters due to the increase in the speed of the air compressor is discharged through the bypass branch, so that the fuel-electric system is not shut down, the number of starts and stops of the fuel-electric system is greatly reduced, and the degradation of the performance of the fuel-electric system is slowed down. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the hydrogen fuel cell system of the present invention.

[0019] Figure numerals: fuel cell stack 1, air filter 2, ambient temperature sensor 3, first air flow meter 4, air compressor 5, intercooler 6, stop valve 7, first pressure sensor 8, first temperature sensor 9, bypass valve 10, second air flow meter 11, back pressure valve 12, tail exhaust pipe 13, muffler 14, second pressure sensor 15, second temperature sensor 16, purge branch 17. DETAILED DESCRIPTION

[0020] like Figure 1As shown, a hydrogen fuel cell system includes a fuel cell stack 1, an air intake pipeline for introducing air into the fuel cell stack 1, and an air tail exhaust pipeline for exhausting cathode tail exhaust from the fuel cell stack 1.

[0021] The air intake pipeline is provided with an air filter 2, a first air flow meter 4, an air compressor 5, an intercooler 6, and a stop valve 7 in sequence from the upstream end (the end away from the fuel cell stack 1) to the downstream end. Among them, an ambient temperature sensor 3 is also provided on the air intake pipeline in a section between the air filter 2 and the first air flow meter 4. The air intake pipeline is also provided with a first pressure sensor 8 and a first temperature sensor 9 downstream of the stop valve 7.

[0022] The air filter 2 is used to filter the air entering the air compressor 5 to remove dust and other impurities. The ambient temperature sensor 3 is used to detect the temperature of the air entering the air intake pipe after being filtered by the air filter 2. The first air flow meter 4 is used to detect the flow rate of air entering the air compressor 5. The air compressor 5 is used as a power source for introducing air into the fuel cell stack 1. The temperature of the air increases after passing through the air compressor 5, and the intercooler 6 is used to cool the air after passing through the air compressor 5. The stop valve 7 is used to adjust the amount of air entering the fuel cell stack 1. The first pressure sensor 8 is used to detect the air pressure of the air entering the fuel cell stack 1. The first temperature sensor 9 is used to detect the temperature of the air entering the fuel cell stack 1.

[0023] The air tail exhaust pipeline is provided with a back pressure valve 12, a tail exhaust pipe 13, and a muffler 14 in sequence from the upstream end (the end close to the stack 1) to the downstream end. The air tail exhaust pipeline is also provided with a second pressure sensor 15 and a second temperature sensor 16 upstream of the back pressure valve 12.

[0024] The second pressure sensor 15 is used to detect the pressure of the cathode tail exhaust (tail exhaust air) discharged from the stack 1. The second temperature sensor 16 is used to detect the temperature of the cathode tail exhaust discharged from the stack 1. The back pressure valve 12 is used to control the back pressure of the air in the stack 1. The tail exhaust pipe 13 is used to discharge the tail exhaust air. The muffler 14 is used to mute the tail exhaust air discharged from the tail exhaust pipe 13, and the air after mute treatment is discharged into the atmosphere.

[0025] A bypass branch is provided between the air intake pipeline and the air tail exhaust pipeline, the upstream end of the bypass branch is connected to the air intake pipeline between the intercooler 6 and the stop valve 7, and the downstream end of the bypass branch is connected to the tail exhaust pipe 13 on the air tail exhaust pipeline. A bypass valve 10 is provided on the bypass branch, and a second air flow meter 11 is provided downstream of the bypass valve 10 (close to one end of the air tail exhaust pipeline).

[0026] The bypass valve 10 is used to control the opening and closing of the bypass branch, and can also cooperate with the stop valve 7 and the back pressure valve 12 to control the distribution ratio of air between entering the fuel cell stack 1 through the air intake pipeline and being discharged through the bypass branch through the tail exhaust pipe 13.

[0027] A purge branch 17 connected to the outer frame of the stack is also provided on the air intake pipeline between the intercooler 6 and the stop valve 7. The stop valve 7 can control the air to enter the purge branch 17 during the purge.

[0028] A zero-power output method for a fuel cell engine system, wherein the fuel cell engine system comprises a fuel cell system and a lithium battery, wherein the fuel cell system is Figure 1 A hydrogen fuel cell system with the structure shown in FIG.

[0029] When the lithium battery SOC is ≥80%, the fuel-electric system is deloaded to the idle condition, and the fuel-electric system is switched to a zero output state, and the lithium battery is not charged; the speed of the air compressor 5 is increased to increase the power consumption of the air compressor 5, and the bypass valve 10 is opened. By adjusting the opening of the back pressure valve 12 and the bypass valve 10, the excess air flow is discharged through the bypass branch to ensure that the inlet flow and inlet pressure are consistent with the idle condition. That is, under the idle condition, the air compressor 5 is used to consume the power generated at idle speed, so that the fuel-electric system is not shut down and the lithium battery is not charged. Under the preferred embodiment, the speed of the air compressor 5 is increased to a net output power of the fuel-electric system ≤ 0.5kW.

[0030] When the lithium battery has sufficient power and does not need to be charged, the fuel-electric system is unloaded to the idle condition and switched to the zero output state, the bypass valve is opened, and the power generated by the fuel-electric system is consumed by increasing the speed of the air compressor. The excess air that enters due to the increased speed of the air compressor is discharged through the bypass branch, thereby achieving the fuel-electric system without shutting down, greatly reducing the number of starts and stops of the fuel-electric system, and slowing down the degradation of the performance of the fuel-electric system.

[0031] Example 1

[0032] Taking a certain system as an example, the idle current (stack output current) is 30A, and the net output power of the fuel-electric system is 10.6kW, as shown in Table 1.

[0033] Table 1

[0034] Table 2

[0035] It is necessary to increase the power consumption of the air compressor by 10.6kW to meet the requirement of zero output. According to the MAP diagram of the air compressor (the MAP diagram of the air compressor is the "pressure-flow characteristic curve diagram", provided by the purchasing manufacturer), as shown in Table 2, when the air compressor speed is 95000r / min, the power consumption of the air compressor is about 11kW, which can meet the requirement of zero power output. At this time, the air flow rate at the outlet of the air compressor is 80g / s, while the fuel cell stack only needs 15g / s. The excess air needs to be discharged from the bypass branch, and the bypass valve is opened to adjust the air flow and pressure entering the stack to be consistent with the idle speed.

Claims

1. A hydrogen fuel cell system, characterized in that: It comprises a fuel cell stack, an air intake pipeline for supplying air to the fuel cell stack, and an air tail exhaust pipeline for discharging cathode tail exhaust from the fuel cell stack, wherein an air compressor is arranged on the air intake pipeline, a first air flow meter is arranged upstream of the air compressor, and a back pressure valve is arranged on the air tail exhaust pipeline, and is characterized in that a bypass branch is arranged between the air intake pipeline and the air tail exhaust pipeline, a bypass valve is arranged on the bypass branch, and a second air flow meter is arranged downstream of the bypass valve; A tail exhaust pipe is provided on the air tail exhaust pipeline downstream of the back pressure valve, the upstream end of the bypass branch is connected to the air intake pipeline downstream of the air compressor, and the downstream end of the bypass branch is connected to the tail exhaust pipe on the air tail exhaust pipeline.

2. The hydrogen fuel cell system according to claim 1, characterized in that: The air intake pipeline is also provided with an intercooler and a shut-off valve, wherein the intercooler is located downstream of the air compressor, and the shut-off valve is located downstream of the intercooler; The upstream end of the bypass branch is connected to the air intake pipeline and is located between the intercooler and the shut-off valve.

3. The hydrogen fuel cell system according to claim 2, characterized in that: The air intake pipeline is also provided with a purge branch between the intercooler and the shut-off valve, which is connected to the outer frame of the fuel cell stack.

4. The hydrogen fuel cell system according to claim 2, characterized in that: The air intake pipeline is also provided with a first pressure sensor and a first temperature sensor downstream of the stop valve; The air tail exhaust pipeline is provided with a second pressure sensor and a second temperature sensor upstream of the back pressure valve.

5. The hydrogen fuel cell system according to claim 1, characterized in that: The air intake pipeline is provided with an air filter upstream of the first air flow meter, and the air intake pipeline is also provided with an ambient temperature sensor between the air filter and the first air flow meter.

6. The hydrogen fuel cell system according to claim 1, characterized in that: The bypass branch is further provided with a muffler downstream of the tail exhaust pipe.

7. A method for zero power output of a fuel cell engine system, wherein the fuel cell engine system comprises a fuel cell system and a lithium battery, wherein the fuel cell system is a hydrogen fuel cell system according to any one of claims 1 to 6, When the lithium battery SOC is ≥80%, the fuel-electric system is deloaded to the idle condition, and the fuel-electric system is switched to a zero output state, and the lithium battery is not charged; the speed of the air compressor is increased to increase the power consumption of the air compressor, and the bypass valve is opened. By adjusting the opening of the back pressure valve and the bypass valve, the excess air flow is discharged through the bypass branch to ensure that the stack flow and stack pressure are consistent with the idle condition.

8. The zero power output method of the fuel cell engine system according to claim 7, characterized in that: The air compressor speed is increased to a level where the net output power of the fuel-electric system is ≤ 0.5 kW.

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