Fuel cell engine exhaust system and control method thereof

Abstract

The invention belongs to the technical field of fuel cells, and discloses a fuel cell engine exhaust system and a control method thereof.The fuel cell engine exhaust system comprises a fuel cell stack, a gas compressor, an air compressor, a water separator, an in-stack air pressure sensor, an exhaust control valve and an exhaust pipeline, the gas compressor is in driving connection with the air compressor, and the gas compressor is connected with a cathode inlet of a fuel cell; the in-pile air pressure sensor is arranged at a cathode inlet of the electric pile, a cathode outlet of the electric pile is connected with the water separator, the exhaust control valve is arranged on an exhaust pipeline of the cathode outlet of the electric pile, and the air compressor is connected with the water separator. According to the fuel cell engine exhaust system with the exhaust back pressure valve and the exhaust bypass branch, the air inlet pressure of the cathode of the electric pile is adjusted, so that the requirement of the cathode of the electric pile on the pressure under all working conditions is met under the condition that the capacity of a turbine for establishing the pressure of an air supply system is limited; the problems of performance attenuation and service life shortening of the electric pile are avoided, and the potential safety hazard possibly causing serious problems such as vehicle power interruption is eliminated.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell technology, and specifically relates to a fuel cell engine exhaust system and its control method. Background Technology

[0002] As a highly efficient and clean power device, the core principle of a fuel cell engine is to directly convert chemical energy into electrical energy through the electrochemical reaction of fuel and oxidant, thereby providing power output for various devices. Among many fuel types, hydrogen is the optimal choice due to its cleanliness. When a fuel cell engine uses hydrogen as fuel, the only end product of the energy conversion process is water, achieving true zero emissions and effectively meeting the core needs of global energy conservation, emission reduction, and environmental protection. In addition, fuel cell engines possess significant comprehensive advantages, including high power generation efficiency, high specific energy density, and low operating noise, demonstrating broad application prospects in transportation, distributed power generation, and other fields.

[0003] In the variable operating conditions of fuel cell engines, the ability to quickly adjust the cathode pressure to achieve timely power response is a key performance indicator that determines whether the engine can meet the needs of actual applications, and is directly related to the practicality, reliability and energy efficiency limit of the system.

[0004] From the perspective of core operating condition response requirements, fuel cell engines often face dynamic scenarios such as start-up, acceleration, and sudden load changes—for example, the power demand when a new energy vehicle starts up. In these situations, the electrochemical reaction rate needs to match the load changes in real time, and the oxygen supply rate at the cathode is the core bottleneck restricting the reaction rate. The essence of rapidly adjusting the cathode pressure is to instantaneously change the partial pressure of oxygen on the cathode side and the mass transfer driving force: when the load increases, the cathode pressure needs to be rapidly increased. On the one hand, this accelerates the diffusion rate of oxygen from the flow channel to the catalyst layer, compensating for the surge in oxygen consumption under high power and preventing the catalyst layer from stagnating due to "oxygen starvation." On the other hand, the rapid increase in pressure can simultaneously enhance the adsorption capacity of oxygen on the proton exchange membrane surface, improving the kinetic rate of the electrochemical reaction and ensuring that the output power increases synchronously with the load demand, avoiding problems such as power response lag and insufficient power. Conversely, when the load drops sharply, if the cathode pressure cannot drop quickly, the excessively high oxygen partial pressure will lead to over-oxygenation in the reaction, not only increasing the ineffective energy consumption of the air compressor but also potentially causing oxidation and corrosion of the catalyst layer. At the same time, the risk of mixing excess oxygen with unreacted hydrogen will also increase significantly.

[0005] From the perspective of system stability and lifespan assurance, rapid and precise cathode pressure regulation can effectively suppress voltage fluctuations and stress shocks under dynamic operating conditions. If cathode pressure regulation is delayed, a mismatch between "reaction demand and oxygen supply" will occur during sudden load changes: the voltage will drop sharply under high load and rise sharply under low load. This drastic voltage fluctuation will accelerate the chemical degradation of the proton exchange membrane and cause stress concentration at the electrode interface, leading to catalyst layer peeling and gas diffusion layer pore blockage, severely shortening the stack's lifespan. Rapidly responding pressure control can smooth the voltage change curve, maintain the dynamic balance of the electrochemical reaction, reduce instantaneous imbalances in hydrothermal distribution, and avoid exacerbating localized "drying" or "flooding" caused by sudden pressure changes, thus providing a stable operating environment for the stack.

[0006] From a practical application perspective, the requirements for power response speed are becoming increasingly stringent for vehicles, portable power supplies, and emergency power generation equipment. For example, fuel cell vehicles need to have acceleration performance comparable to gasoline vehicles, requiring the engine to switch from idle speed to rated power within 1-2 seconds. If there is a delay in cathode pressure regulation during this process, it will cause power output "lag," seriously affecting the user experience. Rapid cathode pressure regulation capability allows fuel cell engines to accurately follow load commands, achieving "on-demand" power delivery, breaking through the energy supply bottleneck under dynamic operating conditions. At the same time, by optimizing oxygen utilization, it balances rapid response with energy efficiency, avoiding energy waste caused by over-supply or under-supply, laying a core foundation for the large-scale application of fuel cell engines in high-dynamic demand scenarios.

[0007] With the continuous development of fuel cell technology, the design and optimization of related supporting systems have gradually become key to improving the overall performance of the fuel cell engine. Among them, the exhaust system, as an important component to ensure the stable operation of the fuel cell engine, directly affects the stack's efficiency and service life due to its structural rationality and control effectiveness. Currently, some patent literature has explored the structural design of fuel cell exhaust systems, but functional limitations still exist.

[0008] Patent document 1 (CN202111397791.2) discloses a hydrogen fuel cell exhaust system and a vehicle. This technical solution proposes an exhaust system configuration including a muffler and a water separation structure. This exhaust system has gas-water separation and drainage functions, which can prevent water accumulation in the muffler from interfering with noise reduction, minimizing the impact of water in the exhaust on the muffler and improving the performance and efficiency of the exhaust system. However, it does not provide a control method for the exhaust system, and lacks valves or other components for adjusting and controlling the exhaust system.

[0009] Patent document 2 (CN202221519242.8) discloses an underwater exhaust device and a fuel cell engine exhaust system, including: multiple one-way valves, a buffer container, an electronically controlled valve, and a booster pump. The one-way valves include a first one-way valve and a second one-way valve, which are connected sequentially. The three valves—the first one-way valve, the electronically controlled valve, and the second one-way valve—form a protective measure to prevent water backflow into the engine, avoiding damage caused by water backflow. Furthermore, the booster pump and the buffer container ensure that the exhaust is within a relatively stable pressure range, providing a better air environment for the engine during underwater exhaust. However, it does not provide a control method for the exhaust bypass path, making it impossible to regulate the cathode intake pressure of the fuel cell stack.

[0010] From the perspective of existing technologies, the development of current fuel cell engine exhaust systems still faces significant technical bottlenecks. There is a lack of ability to regulate the intake pressure of the fuel cell stack cathode. With the limited ability of the turbine to establish air supply system pressure, it is impossible to meet the pressure requirements of the fuel cell stack cathode under all operating conditions, leading to fuel cell stack performance degradation, shortened lifespan, and potential safety hazards such as vehicle power interruption. Summary of the Invention

[0011] The purpose of this invention is to provide a fuel cell engine exhaust system and its control method. This invention designs a fuel cell engine exhaust system with an exhaust back pressure valve and an exhaust bypass branch. Combined with the control method of this invention, it realizes the regulation of the cathode intake pressure of the fuel cell stack. This allows the system to meet the pressure requirements of the fuel cell stack cathode under all operating conditions, even when the turbine's ability to build up the air supply system pressure is limited. This avoids problems such as fuel cell stack performance degradation and shortened lifespan, and eliminates safety hazards that may cause serious problems such as vehicle power interruption.

[0012] The specific details of the plan are as follows:

[0013] A fuel cell engine exhaust system includes a fuel cell stack, a compressor, an air compressor, a water separator, an infeed air pressure sensor, an exhaust control valve, and an exhaust pipeline. The fuel cell stack, compressor, air compressor, infeed air pressure sensor, water separator, and exhaust control valve are all located on the exhaust pipeline. The compressor and air compressor are driven and connected. The compressor outlet is connected to the cathode inlet of the fuel cell. The infeed air pressure sensor is located on the exhaust pipeline at the cathode inlet of the fuel cell stack. The cathode outlet of the fuel cell stack is connected to the inlet of the water separator. The exhaust control valve is located on the exhaust pipeline at the cathode outlet of the fuel cell stack. The air compressor inlet is connected to the outlet of the water separator.

[0014] The fuel cell engine exhaust system of the present invention includes a fuel cell stack, a compressor, an air compressor, a water separator, an inlet air pressure sensor, an exhaust control valve, and an exhaust pipeline. The compressor and the air compressor are driven and connected. The outlet of the compressor and the cathode inlet of the fuel cell are connected through the exhaust pipeline. The inlet air pressure sensor is installed on the exhaust pipeline at the cathode inlet of the fuel cell stack. The cathode outlet of the fuel cell stack is connected to the inlet of the water separator. The exhaust control valve is installed on the exhaust pipeline at the cathode outlet of the fuel cell stack. The inlet of the air compressor is connected to the outlet of the water separator through the exhaust main line.

[0015] Furthermore, the air compressor is a turbine without VNT, and the exhaust pipeline includes an exhaust main line and an exhaust bypass line. One end of the exhaust bypass line is connected to the exhaust main line located before the inlet of the turbine without VNT; the other end of the exhaust bypass line is connected to the exhaust main line after the exhaust port of the turbine without VNT. The exhaust control valve includes an exhaust back pressure valve and an exhaust bypass valve. The exhaust back pressure valve is located on the exhaust main line at the cathode outlet of the fuel cell stack, and the exhaust bypass valve is located on the exhaust bypass line.

[0016] Because the turbine's ability to establish air supply system pressure is limited, it cannot meet the pressure requirements of the fuel cell stack cathode under all operating conditions. Therefore, this invention preferably designs a fuel cell exhaust system with an exhaust back pressure valve and an exhaust bypass branch. The heavy air compressor in this system uses a turbine without a VNT (Vehicle Nozzle Threat). The exhaust pipeline includes an exhaust main line and an exhaust bypass line. One end of the exhaust bypass line is connected to the exhaust main line before the inlet of the turbine without a VNT; the other end of the exhaust bypass line is connected to the exhaust main line after the exhaust outlet of the turbine without a VNT. The exhaust control valve includes an exhaust back pressure valve and an exhaust bypass valve. The exhaust back pressure valve is located on the exhaust main line at the fuel cell stack cathode outlet, and the exhaust bypass valve is located on the exhaust bypass line. This scheme is the optimal solution of this invention. Combined with the control method of this invention, it achieves regulation of the fuel cell stack cathode inlet pressure, meeting the fuel cell stack cathode's pressure requirements under all operating conditions.

[0017] Furthermore, the air compressor is a turbine with VNT, the exhaust pipeline includes an exhaust main line, and the exhaust control valve includes an exhaust back pressure valve, which is located on the exhaust main line at the cathode outlet of the fuel cell stack.

[0018] The alternative exhaust system for the fuel cell engine of this invention uses a turbine with a VNT (Vehicle Nozzle Turbine) as the air compressor. The exhaust pipeline includes a main exhaust path, and the exhaust control valve includes an exhaust back pressure valve, which is located on the main exhaust path at the cathode outlet of the fuel cell stack. This solution, by adjusting the opening of the VNT, replaces the exhaust bypass path and exhaust bypass valve in the optimal solution. Together with the exhaust back pressure valve, it regulates the intake pressure of the fuel cell stack cathode, meeting the pressure requirements of the fuel cell stack cathode under all operating conditions.

[0019] A method for exhausting a fuel cell engine exhaust system, applied to the fuel cell engine exhaust system, includes the following steps:

[0020] S1. During the calibration phase, the intake pressure is scanned, and the intake pressure with the highest system output power is used as the target air pressure value. A mapping table between the target current and the target air pressure value at the inlet is established. The target air pressure value at the cathode inlet of the fuel cell stack is determined by querying this mapping table using the target current. The air pressure value collected by the inlet air pressure sensor is compared with the preset target air pressure value at the cathode inlet of the fuel cell stack. If the air pressure value collected by the inlet air pressure sensor meets the target pressure value requirement, step S2 is executed. If the air pressure value collected by the inlet air pressure sensor is lower than the target air pressure value, step S3 is skipped. If the air pressure value collected by the inlet air pressure sensor is higher than the target air pressure value, step S4 is skipped.

[0021] S2. Keep the exhaust control valve open until the engine finishes running;

[0022] S3. Reduce the opening of the exhaust control valve so that the air pressure value collected by the inlet air pressure sensor meets the target air pressure value requirement, and then maintain the opening of the exhaust control valve at this time until the engine finishes working.

[0023] S4. Increase the opening of the exhaust control valve until the air pressure value collected by the inlet air pressure sensor meets the target air pressure value requirement. Then, maintain the opening of the exhaust control valve until the engine finishes running.

[0024] The fuel cell engine exhaust system of this control method uses a turbine without a VNT (Vehicle Nozzle Transmission Unit) and is equipped with an exhaust main path, an exhaust bypass path, and an exhaust bypass valve. One end of the exhaust bypass path is connected to the exhaust main path before the inlet of the turbine without a VNT; the other end of the exhaust bypass path is connected to the exhaust main path after the exhaust port of the turbine without a VNT. First, it is determined whether the inlet air pressure entering the cathode meets the requirements. If the inlet air pressure entering the cathode meets the requirements, the exhaust back pressure valve is kept open, and the exhaust bypass valve remains closed. If the inlet air pressure entering the cathode is lower than the requirements, the opening of the exhaust back pressure valve is reduced to ensure that the pressure on the cathode side of the fuel cell stack meets the requirements, allowing the fuel cell engine to operate normally. The target air pressure value entering the fuel cell stack is obtained by querying the target current MAP (Magnetic Mapping). The deviation between the cathode inlet pressure sensor value and the target air pressure value of the fuel cell stack is used to control the opening of the exhaust back pressure valve using a closed-loop PID controller. If the inlet air pressure entering the cathode is higher than the requirements, the required pressure drop is identified. If the required pressure drop exceeds the limit, the exhaust back pressure valve is fully opened to rapidly reduce the pressure. If the required pressure drop is less than the limit, the opening of the exhaust back pressure valve is increased. When the exhaust back pressure valve is fully open and the cathode pressure of the fuel cell stack is still greater than the target air pressure, the opening of the exhaust bypass valve is increased, and some gas flows out through the exhaust bypass branch to reduce the cathode pressure of the fuel cell stack. If the inlet air pressure entering the cathode of the fuel cell stack meets the requirements, the opening of the exhaust back pressure valve and the exhaust bypass valve is maintained.

[0025] Furthermore, in the exhaust system of the fuel cell engine, in step S2, the exhaust back pressure valve is kept open and the exhaust bypass valve is kept closed until the engine finishes operating.

[0026] Furthermore, in step S3, based on the deviation between the air pressure value collected by the infeed air pressure sensor and the target air pressure value, the PID controller is used in closed loop to reduce the opening of the exhaust back pressure valve, while the exhaust bypass valve remains closed. After the air pressure value collected by the infeed air pressure sensor meets the target air pressure value requirement, the opening of the exhaust back pressure valve is maintained until the engine finishes operating.

[0027] Furthermore, in step S4, the opening of the exhaust back pressure valve is increased. When the exhaust back pressure valve is fully open and the cathode pressure of the fuel cell stack is still greater than the target air pressure value, the opening of the exhaust bypass valve is increased to reduce the cathode pressure of the fuel cell stack. After the air pressure value collected by the infeed air pressure sensor meets the target air pressure value requirement, the opening of the exhaust back pressure valve and the exhaust bypass valve is maintained until the engine finishes working.

[0028] Furthermore, in the exhaust system of the fuel cell engine, step S2 maintains the opening of the exhaust back pressure valve and the opening of the VNT of the turbine with VNT until the engine finishes operating.

[0029] This control method employs an alternative fuel cell engine exhaust system to the present invention. The air compressor uses a turbine with VNT (Vehicle Neck Turbine), without an exhaust bypass passage or exhaust bypass valve. The intake pressure of the fuel cell stack cathode is adjusted by regulating the opening of the VNT, thus meeting the pressure requirements of the fuel cell stack cathode under all operating conditions.

[0030] Furthermore, in step S3, the opening of the exhaust back pressure valve is reduced, while the VNT of the turbine with VNT is kept open. After the air pressure value collected by the inlet air pressure sensor meets the target air pressure value requirement, the opening of the exhaust back pressure valve is maintained until the engine finishes operating.

[0031] Furthermore, in step S4, the opening of the exhaust back pressure valve is increased. When the exhaust back pressure valve is fully open and the cathode pressure of the fuel cell stack is still greater than the target air pressure value, the opening of the VNT of the turbine with VNT is increased to reduce the cathode pressure of the fuel cell stack. After the air pressure value collected by the infeed air pressure sensor meets the target air pressure value requirement, the opening of the exhaust back pressure valve and the VNT of the turbine with VNT are maintained until the engine finishes working.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] Since the turbine's ability to establish air supply system pressure is limited and cannot meet the pressure requirements of the fuel cell stack cathode under all operating conditions, this invention designs a fuel cell engine exhaust system with an exhaust back pressure valve and an exhaust bypass branch. Combined with the control method of this invention, the intake pressure of the stack cathode is regulated, so that even with the turbine's limited ability to establish air supply system pressure, the pressure requirements of the fuel cell stack cathode under all operating conditions can be met. This avoids problems such as stack performance degradation and shortened lifespan, and eliminates safety hazards that may cause serious problems such as vehicle power interruption. Attached Figure Description

[0034] Figure 1 This is a flowchart illustrating the control method for the exhaust system of a fuel cell engine without VNT (Vehicle Turbine) according to the present invention.

[0035] Figure 2 This is a schematic diagram of the exhaust system of the fuel cell engine without VNT according to the present invention.

[0036] Figure 3 This is a schematic diagram of the exhaust system of the fuel cell engine with VNT turbine according to the present invention.

[0037] Figure 4 This is a comparison chart showing the response of the control method of this invention and the traditional PID control method to transient operating conditions and voltage drop demand.

[0038] In the picture:

[0039] 1. Fuel cell stack; 2. Compressor; 3. Air compressor; 3.1. Turbine without VNT; 3.2. Turbine with VNT; 4. Water separator; 5. Infeed air pressure sensor; 6. Exhaust control valve; 6.1. Exhaust back pressure valve; 6.2. Exhaust bypass valve. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0041] The terminology used in this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in this invention and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0042] It should be noted that the terms "front", "rear", "inner", "outer", "left", "right", etc., used in this invention refer to the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0043] The following examples illustrate this. Figure 1 , Figure 2 , Figure 3 and Figure 4 The present invention will be described in detail below.

[0044] Example 1:

[0045] A fuel cell engine exhaust system includes a fuel cell stack 1, a compressor 2, an air compressor 3, a water separator 4, an inlet air pressure sensor 5, an exhaust control valve 6, and an exhaust pipeline. The fuel cell stack 1, compressor 2, air compressor 3, inlet air pressure sensor 4, water separator 5, and exhaust control valve 6 are all located on the exhaust pipeline. The compressor 2 and air compressor 3 are driven and connected. The outlet of the compressor 2 is connected to the cathode inlet of the fuel cell 1. The inlet air pressure sensor 5 is located on the exhaust pipeline at the cathode inlet of the fuel cell stack 1. The cathode outlet of the fuel cell stack 1 is connected to the inlet of the water separator 4. The exhaust control valve 6 is located on the exhaust pipeline at the cathode outlet of the fuel cell stack 1. The inlet of the air compressor 3 is connected to the outlet of the water separator 4.

[0046] See Figure 2 As shown, the air compressor 3 is a turbine 3.1 without a VNT (Vehicle Necklace). The exhaust pipeline includes a main exhaust line and an exhaust bypass line. One end of the exhaust bypass line is connected to the main exhaust line before the inlet of the turbine 3.1 without a VNT; the other end of the exhaust bypass line is connected to the main exhaust line after the outlet of the turbine 3.1 without a VNT. The exhaust control valve 6 includes an exhaust back pressure valve 6.1 and an exhaust bypass valve 6.2. The exhaust back pressure valve 6.1 is located on the main exhaust line at the cathode outlet of the fuel cell stack 1, and the exhaust bypass valve 6.2 is located on the exhaust bypass line. The exhaust bypass valve 6.2 is normally in the closed state.

[0047] Figure 2 The exhaust system of the fuel cell engine includes a fuel cell stack 1, a compressor 2, a turbine 3.1 without a VNT, a water separator 4, an inlet air pressure sensor 5, an exhaust back pressure valve 6.1, and an exhaust bypass valve. The arrows indicate the direction of air flow. After passing through a filter, the air is connected to the inlet of the compressor 2. The outlet of the compressor 2 is connected to the cathode inlet of the fuel cell stack 1. The exhaust air from the stack passes through the exhaust back pressure valve 6.1 and enters the water separator 4, where liquid water in the cathode exhaust is separated and discharged. The remaining gas enters the turbine 3.1 without a VNT to perform work on it. The main exhaust path has an exhaust bypass path. One end of the exhaust bypass path is connected to the main exhaust path and is located before the inlet of the turbine 3.1 without a VNT; the other end of the exhaust bypass path is connected to the main exhaust path and is located after the exhaust port of the turbine 3.1 without a VNT. An exhaust bypass valve 6.1 is provided on the exhaust bypass passage to control the flow rate of the exhaust bypass passage. The opening degree of the exhaust bypass valve 6.1 is adjustable.

[0048] The exhaust bypass valve 6 is normally closed. When the exhaust back pressure valve 4 is fully open and the cathode pressure of the fuel cell stack 3 is still greater than the target air pressure, the exhaust bypass valve 6 opens wider, and some gas flows out through the exhaust bypass branch to reduce the cathode pressure of the fuel cell stack 3.

[0049] Example 2:

[0050] A fuel cell engine exhaust system includes a fuel cell stack 1, a compressor 2, an air compressor 3, a water separator 4, an inlet air pressure sensor 5, an exhaust control valve 6, and an exhaust pipeline. The fuel cell stack 1, compressor 2, air compressor 3, inlet air pressure sensor 4, water separator 5, and exhaust control valve 6 are all located on the exhaust pipeline. The compressor 2 and air compressor 3 are driven and connected. The outlet of the compressor 2 is connected to the cathode inlet of the fuel cell 1. The inlet air pressure sensor 5 is located on the exhaust pipeline at the cathode inlet of the fuel cell stack 1. The cathode outlet of the fuel cell stack 1 is connected to the inlet of the water separator 4. The exhaust control valve 6 is located on the exhaust pipeline at the cathode outlet of the fuel cell stack 1. The inlet of the air compressor 3 is connected to the outlet of the water separator 4.

[0051] See Figure 3 As shown, the air compressor is a turbine 3.2 with VNT, the exhaust pipeline includes an exhaust main pipeline, and the exhaust control valve includes an exhaust back pressure valve 6.1. The exhaust back pressure valve 6.1 is located on the exhaust main pipeline at the cathode outlet of the fuel cell stack 1.

[0052] This solution is an alternative to the present invention. The air compressor of the fuel cell engine exhaust system is a turbine 3.2 with VNT (Vehicle Navier-Temperature), the exhaust pipeline only includes the main exhaust path, and the exhaust control valve includes an exhaust back pressure valve 6.1. By adjusting the opening of the exhaust back pressure valve 6.1 and the VNT of the turbine 3.2 with VNT, the intake pressure of the fuel cell stack cathode in this fuel cell engine exhaust system is adjusted to meet the pressure requirements of the fuel cell stack cathode under all operating conditions.

[0053] Example 3:

[0054] This invention also provides an exhaust method for a fuel cell engine exhaust system, applicable to the aforementioned fuel cell engine exhaust system, see [link to relevant documentation]. Figure 1 As shown, the steps include:

[0055] S1. During the calibration phase, the intake pressure is scanned, and the intake pressure with the highest system output power is used as the target air pressure value. A mapping relationship table between the target current and the target air pressure value at the inlet is established. The target air pressure value at the cathode inlet of fuel cell stack 1 is determined by querying the mapping relationship table using the target current. The air pressure value collected by the inlet air pressure sensor is compared with the preset target air pressure value at the cathode inlet of the fuel cell stack. If the air pressure value collected by the inlet air pressure sensor meets the target pressure value requirement, step S2 is executed. If the air pressure value collected by the inlet air pressure sensor is lower than the target air pressure value, step S3 is skipped. If the air pressure value collected by the inlet air pressure sensor is higher than the target air pressure value, step S4 is skipped.

[0056] S2. Keep the exhaust control valve open until the engine finishes running;

[0057] S3. Reduce the opening of the exhaust control valve so that the air pressure value collected by the inlet air pressure sensor meets the target air pressure value requirement, and then maintain the opening of the exhaust control valve at this time until the engine finishes working.

[0058] S4. Increase the opening of the exhaust control valve until the air pressure value collected by the inlet air pressure sensor meets the target air pressure value requirement. Then, maintain the opening of the exhaust control valve until the engine finishes running.

[0059] This control method is applied to the exhaust system of the fuel cell engine, where the air compressor is a turbine without VNT, the exhaust pipeline includes an exhaust main line and an exhaust bypass line, and the exhaust control valve includes an exhaust back pressure valve and an exhaust bypass valve. In step S1, during the calibration stage, the intake pressure is scanned, and the intake pressure with the highest system output power is used as the target value. A mapping relationship table between the target current and the target air pressure value at the inlet is established. The inlet air pressure sensor collects the air pressure value at the cathode inlet of the fuel cell stack, and then compares it with the preset target air pressure value at the cathode inlet of the fuel cell stack. The target air pressure value is obtained through the pre-established mapping relationship table between the target current and the target air pressure value at the inlet.

[0060] If the air pressure value collected by the infeed air pressure sensor meets the target pressure value requirement, then proceed to step S2; if the air pressure value collected by the infeed air pressure sensor is lower than the target air pressure value, then proceed to step S3; if the air pressure value collected by the infeed air pressure sensor is higher than the target air pressure value, then proceed to step S4.

[0061] In step S2, maintain the opening of the exhaust back pressure valve and keep the exhaust bypass valve closed until the engine finishes running.

[0062] In step S3, based on the deviation between the air pressure value collected by the infeed air pressure sensor and the target air pressure value, the PID controller is used in closed loop to reduce the opening of the exhaust back pressure valve, while the exhaust bypass valve remains closed. Once the air pressure value collected by the infeed air pressure sensor meets the target air pressure value requirement, the opening of the exhaust back pressure valve is maintained until the engine finishes operating.

[0063] In step S4, the opening of the exhaust back pressure valve is increased. When the exhaust back pressure valve is fully open and the cathode pressure of the fuel cell stack is still greater than the target air pressure value, the opening of the exhaust bypass valve is increased to reduce the cathode pressure of the fuel cell stack. After the air pressure value collected by the infeed air pressure sensor meets the target air pressure value requirement, the opening of the exhaust back pressure valve and the exhaust bypass valve is maintained until the engine finishes working.

[0064] When the exhaust back pressure valve is fully open, if the cathode pressure of the fuel cell stack is still greater than the target air pressure, the exhaust bypass valve is opened further to reduce the cathode pressure of the fuel cell stack. Once the air pressure value collected by the incoming air pressure sensor meets the target air pressure requirement, the opening of the exhaust back pressure valve and the exhaust bypass valve is maintained until the engine finishes running.

[0065] The control method of this invention is compared with the conventional method of using PID control to reduce load when the power demand changes abruptly during vehicle operation. See [link to comparison]. Figure 4 As shown, traditional PID control methods have a slow response; however, this method identifies transient pressure drop requirements and determines whether a fully open back pressure valve is needed for rapid pressure reduction to meet the rapid load reduction demand. The control method of this invention is significantly superior to the traditional PID control method.

[0066] Example 4:

[0067] The present invention also provides an exhaust method for a fuel cell engine exhaust system, applied to the aforementioned fuel cell engine exhaust system, comprising the following steps:

[0068] S1. During the calibration phase, the intake pressure is scanned, and the intake pressure with the highest system output power is used as the target air pressure value. A mapping relationship table between the target current and the target air pressure value at the inlet is established. The target air pressure value at the cathode inlet of fuel cell stack 1 is determined by querying this mapping relationship table through the target current. The air pressure value collected by the inlet air pressure sensor is compared with the preset target air pressure value at the cathode inlet of the fuel cell stack. If the air pressure value collected by the inlet air pressure sensor meets the target air pressure value requirement, then step S2 is executed. If the air pressure value collected by the inlet air pressure sensor is lower than the target air pressure value, then step S3 is skipped. If the air pressure value collected by the inlet air pressure sensor is higher than the target air pressure value, then step S4 is skipped.

[0069] S2. Keep the exhaust control valve open until the engine finishes running;

[0070] S3. Reduce the opening of the exhaust control valve so that the air pressure value collected by the inlet air pressure sensor meets the target air pressure value requirement, and then maintain the opening of the exhaust control valve at this time until the engine finishes working.

[0071] S4. Increase the opening of the exhaust control valve until the air pressure value collected by the inlet air pressure sensor meets the target air pressure value requirement. Then, maintain the opening of the exhaust control valve until the engine finishes running.

[0072] This control method employs the aforementioned fuel cell engine exhaust system. The air compressor of the fuel cell engine exhaust system is a turbine with VNT (Vehicle Noise Level). The exhaust pipeline includes the main exhaust line, and the exhaust control valve includes the exhaust back pressure valve. In step S1, during the calibration phase, the intake pressure is scanned, and the intake pressure with the highest system output power is used as the target air pressure value. A mapping relationship table between the target current and the target air pressure value at the inlet is established. The inlet air pressure sensor collects the air pressure value at the cathode inlet of the fuel cell stack and compares it with the preset target air pressure value at the cathode inlet of the fuel cell stack. The target air pressure value is obtained through the pre-established mapping relationship table between the target current and the target air pressure value at the inlet. If the air pressure value collected by the inlet air pressure sensor meets the target pressure value requirement, step S2 is executed. If the air pressure value collected by the inlet air pressure sensor is lower than the target air pressure value, step S3 is skipped. If the air pressure value collected by the inlet air pressure sensor is higher than the target air pressure value, step S4 is skipped.

[0073] In step S2, maintain the opening of the exhaust back pressure valve and the opening of the VNT of the turbine with VNT until the engine finishes running.

[0074] In step S3, the opening of the exhaust back pressure valve is reduced, while the VNT of the turbine with VNT is kept open. After the air pressure value collected by the inlet air pressure sensor meets the target air pressure value requirement, the opening of the exhaust back pressure valve is maintained until the engine finishes operating.

[0075] At this point, simply adjusting the opening of the exhaust back pressure valve to maintain the opening of VNT is sufficient to regulate the intake pressure of the fuel cell stack cathode in the exhaust system of this fuel cell engine, thus meeting the pressure requirements of the fuel cell stack cathode under all operating conditions.

[0076] In step S4, the opening of the exhaust back pressure valve is increased. When the exhaust back pressure valve is fully open and the cathode pressure of the fuel cell stack is still greater than the target air pressure value, the opening of the VNT of the turbine with VNT is increased to reduce the cathode inlet pressure of the fuel cell stack 1. After the air pressure value collected by the inlet air pressure sensor meets the target air pressure value requirement, the opening of the exhaust back pressure valve and the VNT of the turbine with VNT are maintained until the engine finishes working.

[0077] In step S4, if increasing the opening of the exhaust back pressure valve and maintaining the opening of the VNT cannot regulate the cathode inlet pressure of the fuel cell stack in the exhaust system of this fuel cell engine, the opening of the VNT of the worm gear with VNT is increased to reduce the pressure at the cathode inlet of fuel cell stack 1. When the air pressure value collected by the inlet air pressure sensor meets the target air pressure value requirement, the opening of the exhaust back pressure valve and the VNT of the turbine with VNT is maintained until the engine finishes working.

[0078] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A fuel cell engine exhaust system characterized by, The fuel cell engine exhaust system comprises a fuel cell stack (1), a compressor (2), an air compressor (3), a water separator (4), an air inlet pressure sensor (5), an exhaust control valve (6) and an exhaust pipeline, wherein the fuel cell stack (1), the compressor (2), the air compressor (3), the water separator (4), the air inlet pressure sensor (5) and the exhaust control valve (6) are arranged on the exhaust pipeline, the compressor (2) and the air compressor (3) are drivingly connected, the outlet of the compressor (2) is connected with the cathode inlet of the fuel cell, the air inlet pressure sensor (5) is arranged on the exhaust pipeline at the cathode inlet of the fuel cell stack (1), the cathode outlet of the fuel cell stack (1) is connected with the inlet of the water separator (4), the exhaust control valve (6) is arranged on the exhaust pipeline at the cathode outlet of the fuel cell stack (1), and the inlet of the air compressor (3) is connected with the outlet of the water separator (4).

2. The fuel cell engine exhaust system of claim 1, wherein, The air compressor (3) is a turbine (3.1) without VNT, the exhaust pipeline comprises an exhaust main pipeline and an exhaust bypass pipeline, one end of the exhaust bypass pipeline is connected with the exhaust main pipeline before the inlet of the turbine (3.1) without VNT, the other end of the exhaust bypass pipeline is connected with the exhaust main pipeline after the exhaust outlet of the turbine (3.1) without VNT, the exhaust control valve (6) comprises an exhaust back pressure valve (6.1) and an exhaust bypass valve (6.2), the exhaust back pressure valve (6.1) is arranged on the exhaust main pipeline at the cathode outlet of the fuel cell stack (1), and the exhaust bypass valve (6.2) is arranged on the exhaust bypass pipeline.

3. The fuel cell engine exhaust system of claim 1, wherein, The air compressor (3) is a turbine (3.2) with VNT, the exhaust pipeline comprises an exhaust main pipeline, and the exhaust control valve (6) comprises an exhaust back pressure valve (6.1), which is arranged on the exhaust main pipeline at the cathode outlet of the fuel cell stack (1).

4. An exhaust method of a fuel cell engine exhaust system, characterized by, The application is applied to the fuel cell engine exhaust system as claimed in any one of claims 1-3, and the steps comprise: S1, in the calibration stage, the air inlet pressure is swept to point, the air inlet pressure with the highest system output power is taken as the target air pressure value, a mapping relationship table of the target current and the target air pressure value is established, the target air pressure value of the cathode inlet of the fuel cell stack (1) is determined by querying the mapping relationship table through the target current, the air pressure value collected by the air inlet pressure sensor (5) is compared with the preset target air pressure value of the cathode inlet of the fuel cell stack (1), if the air pressure value collected by the air inlet pressure sensor (5) meets the target pressure value requirement, step S2 is executed, if the air pressure value collected by the air inlet pressure sensor (5) is lower than the target air pressure value, step S3 is jumped to, and if the air pressure value collected by the air inlet pressure sensor (5) is higher than the target air pressure value, step S4 is jumped to; S2, the opening of the exhaust control valve (6) is kept until the engine works end; S3, reduce the opening of the exhaust control valve (6), so that the air pressure value collected by the air inlet pressure sensor (5) meets the target air pressure value requirement, and then keep the opening of the exhaust control valve (6) at this time until the engine work is finished. S4, increase the opening of the exhaust control valve (6), so that the air pressure value collected by the air inlet pressure sensor (5) meets the target air pressure value requirement, and then keep the opening of the exhaust control valve (6) until the engine work is finished.

5. The control method of a fuel cell engine exhaust system according to claim 4, characterized by, S2, keep the opening of the exhaust back pressure valve (6.1) and the opening of the VNT of the turbo (3.2) until the engine work is finished.

6. The control method of a fuel cell engine exhaust system according to claim 5, characterized by, S3, reduce the opening of the exhaust back pressure valve (6.1), keep the opening of the VNT of the turbo (3.2), so that the air pressure value collected by the air inlet pressure sensor (5) meets the target air pressure value requirement, and then keep the opening of the exhaust back pressure valve (6.1) at this time until the engine work is finished.

7. The control method of a fuel cell engine exhaust system according to claim 6, characterized by, S4, increase the opening of the exhaust back pressure valve (6.1), when the exhaust back pressure valve (6.1) is fully open and the cathode pressure of the fuel cell stack (1) is still greater than the target air pressure value, increase the opening of the VNT of the turbo (3.2) to reduce the cathode pressure of the fuel cell stack (1), so that the air pressure value collected by the air inlet pressure sensor (5) meets the target air pressure value requirement, and then keep the opening of the exhaust back pressure valve (6.1) and the opening of the VNT of the turbo (3.2) until the engine work is finished.

8. The control method of a fuel cell engine exhaust system according to claim 4, characterized by, S2, keep the opening of the exhaust back pressure valve (6.1) and the opening of the VNT of the turbo (3.2) until the engine work is finished.

9. The control method of the fuel cell engine exhaust system according to claim 8, characterized by, S3, reduce the opening of the exhaust back pressure valve (6.1), keep the opening of the VNT of the turbo (3.2), so that the air pressure value collected by the air inlet pressure sensor (5) meets the target air pressure value requirement, and then keep the opening of the exhaust back pressure valve (6.1) at this time until the engine work is finished.

10. The control method of the fuel cell engine exhaust system according to claim 9, characterized by, S4, increase the opening of the exhaust back pressure valve (6.1), when the exhaust back pressure valve (6.1) is fully open and the cathode pressure of the fuel cell stack (1) is still greater than the target air pressure value, increase the opening of the VNT of the turbo (3.2) to reduce the cathode pressure of the fuel cell stack (1), so that the air pressure value collected by the air inlet pressure sensor (5) meets the target air pressure value requirement, and then keep the opening of the exhaust back pressure valve (6.1) and the opening of the VNT of the turbo (3.2) until the engine work is finished.

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