Fuel cell exhaust gas cooling structure and hydrogen discharge method

Abstract

The present application relates to heat exchange technical field, provide a kind of fuel cell exhaust gas cooling structure and its hydrogen discharge method, including the fuel cell of arrangement in roof, still include roof tail exhaust pipe, roof fairing and end wall tail exhaust pipe;The through type cavity is provided in the inside of the roof fairing;The roof tail exhaust pipe connects the type cavity of fuel cell and roof fairing, and tail exhaust gas is transported to the inside of the type cavity of fairing;The end wall tail exhaust pipe is communicated with the type cavity of fairing and under vehicle space, and cooled tail exhaust gas is discharged to under vehicle rail surface by end wall tail exhaust pipe;Relative to the current fuel cell exhaust gas high temperature and high humidity situation and lead to exhaust influence locomotive appearance or influence other equipment, so as to design new structure and improve tail exhaust system function, by increasing electromagnetic valve, increase the way of type cavity in the inside of fairing, avoid a series of problems caused by fuel cell exhaust gas high temperature and high humidity, to meet the functional requirements of fuel cell tail exhaust.

Description

Technical Field

[0001] This invention relates to the field of heat exchange technology, and in particular to a fuel cell exhaust gas cooling structure and hydrogen removal method thereof. Background Technology

[0002] In current hydrogen fuel cell rail train applications, most have short ranges or low speeds, and mostly use small to medium-power fuel cells. During operation, the exhaust gases are directly released into the air above the train. However, due to the high heat dissipation requirements of the fuel cell system in high-speed trains, it can only be placed on the roof. If the exhaust gases are discharged to the sides of the train, the large volume of gas on the platform can affect pedestrians; if discharged onto the train, it will condense into a large amount of fog in low-temperature winter conditions, affecting the appearance. Therefore, it can only be discharged under the train. However, critical components under the train, such as bogie sensors and coupler lubricants, have a high failure rate and are easily damaged in high-temperature and high-humidity environments. Therefore, a new fuel cell exhaust structure is needed to condense the fuel cell exhaust gases before discharging them under the train. Summary of the Invention

[0003] The purpose of this invention is to introduce the exhaust gas from the fuel cell into the interior of the roof diffuser for heat dissipation, and then discharge the exhaust gas to the ground through the end wall pipe after cooling. At the same time, the hydrogen gas in the exhaust gas can be discharged from the roof into the atmosphere.

[0004] To achieve the above objectives, the present invention provides a fuel cell exhaust gas cooling structure, including a fuel cell disposed on the roof of a vehicle, and also including a roof exhaust pipe, a roof shroud, and an end wall exhaust pipe. The roof fairing has a through-type cavity inside; The exhaust pipe on the roof connects the fuel cell to the cavity of the roof fairing, and delivers the exhaust gas into the cavity of the fairing. The end wall tailpipe connects the cavity of the guide shroud with the space under the vehicle, and the cooled exhaust gas is discharged to the under-vehicle rail surface through the end wall tailpipe.

[0005] Furthermore, the roof exhaust pipe is divided into two sections: a system-side exhaust pipe and a fairing-side exhaust pipe. One end of the system-side tailpipe is connected to the fuel cell, and the other end branches out to the first and second positions of the vehicle body; one end of the fairing-side tailpipe is connected to the system-side tailpipe, and the other end extends into the cavity of the corresponding side roof fairing; the system-side tailpipe and the fairing-side tailpipe are connected by a rubber tube.

[0006] Furthermore, the system-side tailpipe is fixed to a pre-set mounting base on the roof, and the fairing-side tailpipe is connected via fasteners through a pre-reserved flange on the fairing.

[0007] Furthermore, it also includes an overflow pipe, which is welded to the tailpipe on the side of the fairing near the flange interface of the fairing, with the other end of the overflow pipe suspended above the roof surface.

[0008] Furthermore, the roof fairing has a segmented structure, with the cavities of two adjacent fairing segments sealed together by flanges and fasteners, and a sealing gasket added between the flanges.

[0009] Furthermore, the cavity is detachably fixed inside the flow guide by fasteners; the inner wall of the cavity is provided with an anti-rust treatment layer.

[0010] Furthermore, a U-shaped water collection trough is formed at the bottom of the cavity of the flow guide; along the length of the train, a 0.5° inclined slope is provided on the bottom surface of the water collection trough, with the higher part of the slope facing the fuel cell and the lower part of the slope facing the tail pipe of the end wall.

[0011] Furthermore, the top of the cavity of the roof diffuser has at least two circular hydrogen vents, each equipped with a solenoid valve; the solenoid valve is used to control the opening and closing of the hydrogen vent.

[0012] Furthermore, the tailpipes on the sides of the duct within the two cavities converge at the end wall of the vehicle body and then connect to the end wall tailpipe, with the outlet of the end wall tailpipe facing the ground.

[0013] The present invention also provides a method for hydrogen removal from a fuel cell exhaust gas cooling structure, comprising the following steps: S1, fuel cell electric start; S2. Calculate the hydrogen concentration in the cavity of the roof fairing; S3. Based on the current hydrogen concentration in the cavity of the roof fairing, if the hydrogen concentration in the cavity is ≥2%, the solenoid valve will open. The opening time of the solenoid valve is determined according to the cavity volume and the size of the hydrogen vent. If the hydrogen concentration in the cavity is <2%, the hydrogen concentration in the cavity will continue to accumulate. S4. After the solenoid valve is opened, the hydrogen concentration in the cavity is continuously monitored. When the hydrogen concentration inside the cavity drops to ≤0.2%, the solenoid valve is closed, the timer is reset, and the process returns to step S2 to continue. S5. When the fuel cell shuts down, the solenoid valve remains open; after shutdown, the solenoid valve closes, ending the process.

[0014] Furthermore, step S2 specifically includes: The parameters affecting the hydrogen concentration in the cavity of the roof fairing are obtained, including fuel cell operating conditions, fuel cell hydrogen utilization rate, operating temperature and pressure. For a fixed-model fuel cell, the hydrogen emissions under different operating conditions are calibrated to generate a MAP diagram; When the fuel cell is running, it retrieves a pre-stored MAP map and queries the hydrogen emissions based on the current operating conditions. The hydrogen concentration in the cavity of the roof fairing is calculated by combining the size of the cavity and the amount of hydrogen emitted.

[0015] This invention introduces the high-temperature, high-humidity exhaust gas from the fuel cell into the cavity of the roof diffuser. Heat exchange occurs between the diffuser wall and the high-speed external airflow during train operation, allowing the exhaust gas to cool and condense as it flows within the cavity. The gas is then discharged to the underside of the vehicle through the end-wall exhaust pipe. Simultaneously, a small amount of hydrogen in the exhaust gas is safely discharged through the roof hydrogen vent. Its specific technical effects include: 1. Improve the appearance of emissions and avoid impacting the surrounding environment: avoid exhaust gases being directly discharged onto the roof of the vehicle to form a large amount of fog that affects the appearance, avoid exhaust gases being discharged to the sides of the vehicle body to affect pedestrians on the platform, and avoid high temperature and high humidity gases being directly discharged under the vehicle to cause high temperature and high humidity damage to key components such as bogie sensors and coupler lubricating oil. 2. Achieve efficient cooling and condensation of exhaust gases: The internal cavity of the roof deflector serves as the exhaust gas flow channel and heat exchange structure. The outer side of the deflector exchanges heat with the high-speed airflow during train operation. The deflector is made of materials with good thermal conductivity, such as aluminum alloy, which can effectively cool and condense the high-temperature and high-humidity exhaust gases, thereby reducing the emission temperature and humidity. 3. Reliable collection and drainage of condensate: The bottom of the cavity is designed as a U-shaped water collection trough with an approximately 0.5° slope along the length of the vehicle, with the lower side facing the end wall. This collects the condensate generated by the exhaust gas cooling and directs it to the rail surface via the exhaust pipe on the end wall, preventing water accumulation and ice formation in winter and condensate buildup when the train is parked on a slope. The overflow pipe prevents condensate from flowing back into the fuel cell stack. 4. Safe and controllable hydrogen emission: A circular hydrogen vent is set at the top of the cavity of the flow guide, and its opening and closing are controlled by a solenoid valve; when the hydrogen volume concentration in the cavity reaches the set threshold, the hydrogen vent is opened, and it is closed after the concentration drops to a safe low level to prevent hydrogen from accumulating at the top of the cavity; at least two hydrogen vents are set to form redundancy and avoid failure of a single vent to vent. In summary, this invention, while ensuring the aesthetic appearance of the train set and the safety of surrounding equipment, achieves cooling and dehumidification of fuel cell exhaust gas, orderly discharge of condensate, and safe discharge of hydrogen, thereby improving the safety, reliability, and environmental adaptability of the fuel cell exhaust system. Attached Figure Description

[0016] Figure 1 This is a plan view of the vehicle roof layout; Figure 2 A schematic diagram of the fairings on both sides of the vehicle roof; Figure 3 Logic diagram of fuel cell exhaust gas emission path; Figure 4 Logic diagram for calculating hydrogen concentration in the cavity; Figure 5This is the control logic diagram of the fuel cell controller for the solenoid valve. Figure 6 This is the hardware control logic diagram for the solenoid valve. Figure 7 Logic diagram for calculating the opening time of the solenoid valve.

[0017] In the diagram: 1-Solenoid valve, 2-Roof diffuser, 3-Cavity, 4-Water collection tank, 5-Cavity side plate, 6-Diffuser fixing point, 7-Hydrogen outlet, 8-System side tailpipe, 9-Diffuser side tailpipe, 10-Rubber hose, 11-Overflow pipe; 12-End wall tailpipe, 13-Fuel cell. Detailed Implementation

[0018] The following describes a complete embodiment of the present invention, in conjunction with the accompanying drawings, of the exhaust gas cooling structure, assembly and installation, online testing, and hydrogen emission control process of the fuel cell for high-speed trains. This embodiment is mounted on a high-power fuel cell system on the roof of a high-speed train.

[0019] Reference Figure 1 and Figure 2 It includes: fuel cell 13, solenoid valve 1, roof diffuser 2, cavity 3, water collection tank 4, cavity side plate 5, diffuser fixing point 6, hydrogen discharge port 7, roof exhaust pipe, overflow pipe 11, rubber hose 10 and end wall exhaust pipe 12.

[0020] This embodiment provides a specific installation and layout implementation process, including: the high-power fuel cell 13 is hoisted and fixed to the middle of the roof of the EMU. The high-power fuel cell 13 converts air and hydrogen into electrical energy through an electrochemical reaction to supply the entire vehicle. During operation, it exhausts high-temperature and high-humidity exhaust gas mixed with hydrogen. Since the fuel cell 13 side is the high-pressure side and the atmospheric environment at the outlet of the end wall lower pipe is the low-pressure side, the pressure is converted into power, causing the exhaust gas to flow out of the fuel cell 13 system and flow to the outlet of the end wall lower pipe. The outer side of the roof is covered with aluminum alloy roof deflectors 2 in sections. The roof deflectors 2 take into account the aerodynamic appearance of the entire vehicle and have a through-type internal structure. The cavity 3 serves as a heat exchange channel for exhaust gas. The exhaust port of the fuel cell 13 is connected to the roof exhaust pipe, which is made of seamless stainless steel pipe and can be divided into two sections: the system-side exhaust pipe 8 and the fairing-side exhaust pipe 9. One end of the system-side exhaust pipe 8 is connected to the fuel cell 13, and the other end branches from the fuel cell 13 system to the first and second positions of the vehicle body. One end of the fairing-side exhaust pipe 9 is connected to the system-side exhaust pipe 8, and the other end is connected to the corresponding side of the roof fairing 2 and extends into the cavity 3 of the roof fairing 2. The exhaust gas flows along the branch pipe of the roof exhaust pipe to the cavities 3 of the roof fairing 2 on both sides (first and second positions).

[0021] The system-side exhaust pipe 8 is fixed to the pre-reserved mounting bracket on the roof. The roof fairing 2 near the fairing-side exhaust pipe 9 has a pre-reserved flange and interface. The fairing-side exhaust pipe 9 is fixed to the flange and secured with fasteners for easy maintenance and installation. The system-side exhaust pipe 8 and the fairing-side exhaust pipe 9 are connected by a rubber hose 10.

[0022] This invention provides a further embodiment. Since the height of the system-side exhaust pipe 8 is usually lower than the connection point between the roof spoiler 2 and the spoiler-side exhaust pipe 9, an overflow pipe 11 needs to be designed near the interface between the spoiler-side exhaust pipe 9 and the roof spoiler 2. This prevents condensate in the system-side exhaust pipe 8 from flowing back into the fuel cell stack 13, and prevents water from accumulating in the pipe and freezing and blocking the pipe when the fuel cell 13 is shut down under low-temperature conditions, which could lead to abnormal startup of the fuel cell 13 the next time. One end of the overflow pipe 11 is welded to the spoiler-side exhaust pipe 9, near the interface of the roof spoiler 2, while the other end is suspended and facing the roof surface. It is configured to drain the condensate in the pipe by gravity to prevent condensate from flowing back into the fuel cell system 13 and to prevent condensate from freezing in low-temperature environments, which could prevent the fuel cell 13 from restarting after shutdown.

[0023] The present invention provides a further embodiment in which, since the fuel cell 13 is far from the end wall, the roof deflector 2 needs to be arranged in sections. The cavities 3 between each section of the roof deflector 2 are connected by flanges, fixed with fasteners, and sealed with gaskets to achieve sealing and anti-resonance function.

[0024] This invention provides a further embodiment in which a special cavity 3 is designed within the diffuser to ensure that the exhaust gas at the outlet of the fuel cell 13 can flow from the cavity 3 to the end-wall exhaust pipe 12 through the roof exhaust pipe. The cavity 3 penetrates the roof diffuser 2 to allow gas flow. The exhaust gas in the two roof diffusers 2 converges at the end wall into the end-wall exhaust pipe 12. The outlet of the end-wall exhaust pipe 12 faces the ground and discharges the cooled exhaust gas into the atmosphere. The cross-sections of the roof diffuser 2 and the cavity 3 are designed according to different vehicle models to meet functional requirements. The cavity side plate 5 is sealed to prevent gas leakage. The cavity 3 is fixed to the roof diffuser 2 with fasteners for easy maintenance.

[0025] The cavity 3 of the roof fairing 2, the diameter of the roof exhaust pipe, and the diameter of the end wall exhaust pipe 12 need to be simulated to confirm that the pressure required for exhaust gas flow will not affect the normal operation of the fuel cell 13 system.

[0026] During train operation, the high-temperature exhaust gas generated by fuel cell 13 exchanges heat with the side wall of roof deflector 2, and the high-speed gas outside roof deflector 2 exchanges heat with roof deflector 2, which can cool the exhaust gas. The roof deflector 2 profile needs to be made of materials with good thermal conductivity such as aluminum alloy, and the inner wall of cavity 3 needs to be rust-proofed to prevent the high temperature and high humidity environment from causing rust inside cavity 3 and reducing the system life.

[0027] In a further embodiment of the present invention, the cavity 3 of the roof fairing 2 is designed in a U-shape to serve as a water collection tank 4, which collects water condensed due to the cooling effect of the high-temperature and high-humidity gas from the exhaust of the fuel cell 13. Along the length of the vehicle, the bottom surface of the water collection tank 4 is designed as a slope with an angle of approximately 0.5°, with the fuel cell 13 system on the higher side and the end wall side on the lower side, to prevent condensate from accumulating and freezing in the water collection tank 4 during winter, and to prevent condensate from accumulating when the train is parked on a slope.

[0028] The present invention provides a further embodiment in which, since hydrogen in the exhaust gas may accumulate at the top of the cavity 3 of the roof diffuser 2, a circular hydrogen vent 7 is designed at the top of the cavity 3 of the roof diffuser 2, and the opening and closing are controlled by a solenoid valve 1. The number of openings is at least two to prevent the failure of hydrogen vent 7 from failing to vent hydrogen.

[0029] This invention provides a method for hydrogen removal from a fuel cell exhaust gas cooling structure, the specific steps of which are as follows: S1, fuel cell 13 electric start; S2. Calculate the hydrogen concentration in the cavity 3 of the roof fairing 2; S3. Based on the current hydrogen concentration in the cavity 3 of the roof diffuser 2, if the hydrogen concentration in the cavity 3 is ≥2%, the solenoid valve 1 will open. The opening time of the solenoid valve 1 will be determined according to the volume of the cavity 3 and the size of the hydrogen outlet 7. If the hydrogen concentration in the cavity 3 is <2%, the hydrogen concentration in the cavity 3 will continue to accumulate. S4. After solenoid valve 1 is opened, the hydrogen concentration in cavity 3 is continuously monitored. When the hydrogen concentration inside cavity 3 drops to ≤0.2%, solenoid valve 1 is closed, the timer is reset, and the process returns to step S2 to continue execution. S5. When fuel cell 13 shuts down, solenoid valve 1 remains open; after shutdown, solenoid valve 1 closes, ending the process.

[0030] Furthermore, step S2 specifically includes: The parameters affecting the hydrogen concentration in the cavity 3 of the roof fairing 2 are obtained, including the operating conditions of the fuel cell 13, the hydrogen utilization rate of the fuel cell 13, the operating temperature and pressure. For the fixed-model fuel cell 13, the hydrogen emissions under different operating conditions are calibrated and a MAP diagram is generated; When fuel cell 13 is running, it retrieves the pre-stored MAP map and queries the hydrogen emissions based on the current operating conditions. The hydrogen concentration in the cavity 3 of the roof diffuser 2 is calculated by combining the size of the cavity 3 of the roof diffuser 2 with the amount of hydrogen emitted.

[0031] The MAP diagram mentioned in the text is a working condition mapping diagram / pulse spectrum diagram.

[0032] Now combined Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 A detailed description is provided of a hydrogen removal method for a fuel cell exhaust gas cooling structure.

[0033] Figure 3 The diagram shows the exhaust gas emission path of fuel cell 13. Fuel cell 13 generates exhaust gas during operation. The internal pressure of fuel cell 13 is higher than the atmospheric pressure at the outlet of the end-wall exhaust pipe 12, and this pressure difference drives the flow of the exhaust gas. The exhaust gas is transported through the roof exhaust pipe into the through-type cavity 3 of the roof diffuser 2. The high-temperature and high-humidity exhaust gas exchanges heat with the cavity 3 wall inside the cavity 3, achieving gas cooling. Some water vapor condenses and precipitates as condensate, which collects in the water collection tank 4 at the bottom of the cavity 3. Hydrogen in the exhaust gas is less dense than air and floats upwards, accumulating in the top area of ​​the cavity 3. The remaining cooled main exhaust gas continues to flow along the cavity 3 and is discharged to the undercarriage rail surface through the end-wall exhaust pipe 12. When the hydrogen concentration accumulated inside the cavity 3 reaches the opening threshold, the solenoid valve 1 of the hydrogen vent 7 opens, releasing the hydrogen accumulated at the top of the cavity 3 outward through the hydrogen vent 7; when the hydrogen concentration inside the cavity 3 drops to the closing threshold, the solenoid valve 1 closes, completing one hydrogen venting process.

[0034] Figure 4 This is a logic diagram for calculating the hydrogen concentration in cavity 3 of the roof spoiler 2. This logic is used to iteratively estimate the real-time hydrogen concentration inside cavity 3 of the roof spoiler 2. Parameters affecting the hydrogen concentration in cavity 3 of the roof spoiler 2 include the operating conditions of fuel cell 13, the hydrogen utilization rate of fuel cell 13, the exhaust flow rate of fuel cell 13, operating temperature, and pressure. For a fixed model of fuel cell 13, without considering device degradation, the above basic parameters are fixed reference parameters. Tests are conducted in advance for this model of fuel cell 13 to measure the hydrogen emissions under different power and temperature conditions. The hydrogen emission values ​​under each operating condition are calibrated, a MAP diagram is generated, and the diagram is stored. During the actual operation of fuel cell 13, the current operating conditions, hydrogen utilization rate, exhaust flow rate, operating temperature and pressure of fuel cell 13 are collected, and the hydrogen emission under the corresponding operating conditions is retrieved from the pre-stored MAP map. Combined with the internal space volume of the cavity 3 of the roof shroud 2, the real-time hydrogen concentration inside the cavity 3 of the roof shroud 2 is calculated iteratively. The calculation result is used as the input basis for the subsequent opening and closing judgment of solenoid valve 1.

[0035] Figure 5 The control logic diagram for solenoid valve 1 by the fuel cell controller is as follows: Solenoid valve 1 is installed at the hydrogen exhaust port 7 of the roof spoiler 2. The power and control lines of solenoid valve 1 are connected to fuel cell 13, which controls and provides power. The FCU (fuel cell controller) of fuel cell 13 calculates that the hydrogen concentration in the cavity exceeds the limit. The FCU sends an opening command to solenoid valve 1 and starts timing. Solenoid valve 1 opens. Since the pressure in cavity 3 is higher than atmospheric pressure, hydrogen gas begins to be discharged. The FCU ends timing, calculates that the hydrogen concentration at this time is <0.2%, and sends a closing command to solenoid valve 1. Solenoid valve 1 closes, and hydrogen gas begins to accumulate in cavity 3 again.

[0036] Figure 6 The hardware control logic diagram for solenoid valve 1 is as follows: When fuel cell 13 is electrically started, it begins to calculate the hydrogen concentration inside cavity 3 of the roof diffuser 2; it continuously judges the hydrogen concentration inside cavity 3. When the hydrogen concentration in cavity 3 is ≥2%, solenoid valve 1 opens, and the hydrogen discharge is adjusted according to the volume of cavity 3 and the size of hydrogen discharge port 7; when the hydrogen concentration inside cavity 3 is ≤0.2%, solenoid valve 1 closes and the timer is reset; when the fuel cell 13 shutdown command is issued, solenoid valve 1 remains open, and solenoid valve 1 closes after the entire unit is shut down.

[0037] Figure 7 Logic diagram for calculating the opening time of solenoid valve 1: After the hydrogen concentration in the cavity 3 of the roof diffuser 2 reaches 2%, the factors affecting the opening time of solenoid valve 1 are: the size of the hydrogen exhaust port 7, the pressure in the cavity 3 of the roof diffuser 2, and the ambient pressure. The size of the hydrogen exhaust port 7 and the opening time of solenoid valve 1 are obtained by simulation and calibration calculation.

[0038] In one specific embodiment, preset parameters such as the opening size of the hydrogen discharge port, the duration of solenoid valve opening, and the hydrogen discharge flow rate are obtained through a method for determining the opening size of the hydrogen discharge port. This method includes two core steps: establishing a multi-physics field coupled simulation model and conducting calibration tests. Through iterative correction, the minimum effective emission area and emission time are finally determined under the premise of meeting the safety threshold.

[0039] This embodiment targets a certain type of 200 km / h rail transit train, where the exhaust gas from its roof-mounted fuel cell system is entirely introduced into the side skirts of the fairing. The fairing has a cross-sectional area of ​​approximately 6390 square millimeters and a length of approximately 10 meters along the train's length. The design objective is to create a circular hydrogen vent at the top of the fairing. Within an ambient temperature range of -40°C to 40°C, when any internal hydrogen concentration sensor detects a concentration of 2% by volume, the solenoid valve automatically opens; when both sensors confirm a concentration below 0.2% by volume, the solenoid valve closes. The initial proposed diameter of the hydrogen vent is 20 mm. This method aims to accurately simulate and experimentally calibrate whether this opening size is the optimal solution that meets safety requirements through the following steps.

[0040] Step 1: Construct a three-dimensional transient multiphysics coupling simulation model.

[0041] This step aims to establish a high-fidelity numerical model to simulate the accumulation and emission of hydrogen within the mold cavity.

[0042] Based on the actual design drawings of the flow deflector, a full-size three-dimensional geometric model was established, including the exhaust gas inlet pipe, the main cavity of the flow deflector, the top hydrogen exhaust port, and the internal flow channel of the solenoid valve. Special mesh refinement is required for areas such as the hydrogen exhaust port, the vicinity of the wall, and the gas inlet to ensure accurate capture of near-wall flow and gas diffusion gradient.

[0043] Define the components of the gas mixture, including at least nitrogen, oxygen, water vapor, and hydrogen. Enable the component transport model. Define a phase transition model between gaseous and liquid water to simulate the condensation process.

[0044] Boundary conditions and initial conditions settings: Inlet boundary: Set as the mass flow inlet. Based on the measured data from the fuel cell bench, input the mixed gas mass flow rate, temperature (85℃ in this embodiment), and mass fraction of each component under the corresponding operating condition. The hydrogen mass fraction needs to be calculated based on the maximum hydrogen volume concentration in the exhaust gas under this operating condition, which meets national standards, to ensure that the simulation covers the most severe operating conditions.

[0045] Outlet boundary (hydrogen discharge port): In the transient simulation when the solenoid valve is open, it is set as a pressure outlet with a relative pressure of 0 Pascals (atmosphere); in the accumulation process when the solenoid valve is closed, it is set as a wall.

[0046] Wall Boundary: The outer metal wall of the fairing is set as the coupled heat transfer boundary. The forced convection heat transfer coefficient corresponding to the ambient temperature (covering -40℃ to 40℃ in this embodiment), the train speed (200 km / h), and parameters such as solar radiation need to be input. The convection heat transfer coefficient can be calculated using empirical formulas or the built-in model of the CFD software.

[0047] Initial conditions: The entire computational domain is initialized as air, the temperature is the ambient temperature, and the hydrogen concentration is zero.

[0048] Solver settings: A transient solver is used. Since the density of hydrogen is much lower than that of air, a gravity model must be enabled, and the correct gravitational acceleration component must be set in the vertical direction to simulate the physical process of hydrogen rising and accumulating under buoyancy. The time step is initially set to 0.05 seconds, and the total simulation duration must cover the entire process from the start of accumulation to the concentration reaching the 2% threshold.

[0049] Step 2: Perform simulation and analyze the results to pre-calibrate the hydrogen discharge port size.

[0050] Using the above model, two sets of core simulations were performed to simulate the hydrogen accumulation process: With the solenoid valve closed, the fuel cell continuously discharges hydrogen-containing exhaust gas into the cavity. The hydrogen volume concentration at two virtual sensor points near the top hydrogen outlet is monitored over time. The time taken for the concentration to rise from 0% to 2% (T_accumulate) is recorded. Simultaneously, a hydrogen concentration distribution cloud map of the entire cavity is output, focusing on identifying any structural dead zones that might prevent hydrogen from effectively rising to the top hydrogen outlet. If any are found, this information needs to be fed back to the structural design for optimization.

[0051] Simulation of hydrogen emission process: Using the previous step's accumulation simulation reaching a 2% concentration as the initial condition, the boundary condition of the hydrogen vent is switched from "wall" to "pressure outlet" to simulate the emission process after the solenoid valve opens. The time (T_exhaust) taken for the concentration at the monitoring sensor point to decrease from 2% to the 0.2% closing threshold is recorded. Simultaneously, the velocity vector diagram and flow rate of the hydrogen vent are output to evaluate the active venting capability of the 20 mm diameter opening.

[0052] By parametrically scanning different hydrogen vent diameters (e.g., 15 mm, 20 mm, 25 mm), the above accumulation and emission simulations were repeated to establish the response relationship of "orifice diameter - accumulation time / emission time". At the simulation level, an optimized orifice size range that can simultaneously satisfy "T_accumulate is long enough to facilitate condensation heat exchange" and "T_exhaust is short enough to ensure rapid and safe operation" was initially selected.

[0053] Step 3: Build a prototype system and conduct calibration tests.

[0054] The accuracy of the simulation depends on the calibration of the model. Therefore, it is necessary to manufacture a fairing sample that is completely consistent with the simulation geometry and build a test platform.

[0055] 1. Experimental platform setup: The prototype section is sealed at both ends and features a controllable hydrogen-containing gas inlet and a top hydrogen vent equipped with a solenoid valve and a flame arrester. Two sets of high-precision hydrogen concentration sensors are installed internally, corresponding to the simulated virtual sensors. Multiple adjustable-speed fans are deployed externally to simulate surface airflow during train operation at 200 km / h. Thermocouples are attached to key locations on the walls to monitor temperature.

[0056] 2. Key Experiment Matrix Design: Several typical operating conditions were selected for testing, including: A) Extreme cold calm wind (-40℃, 0m / s); B) High temperature calm wind (40℃, 0m / s); C) Extreme cold operation (-40℃, 55.5m / s wind speed); D) High temperature operation (40℃, 55.5m / s wind speed). A hydrogen-containing gas mixture with a flow rate of 16,000 liters / minute and a temperature of 85℃ was introduced into the inlet (the hydrogen concentration used was the same as the maximum permissible value as the simulated inlet).

[0057] 3. Experimental Operation and Data Acquisition: For each operating condition, first close the solenoid valve and record the accumulation time of hydrogen concentration from 0 to 2%, as well as the temperature distribution within the mold cavity throughout the process. Then, open the solenoid valve and record the emission time of concentration decreasing from 2% to 0.2%. Repeat this process multiple times and obtain a statistical average.

[0058] Step 4: Simulation model calibration and iteration based on experimental data.

[0059] This step is the core of the method of the present invention, and aims to calibrate the simulation model to a high degree of consistency with physical reality.

[0060] 1. Key parameter correction: Compare the simulation results with the experimental results under the same operating condition. There will inevitably be discrepancies between the two in terms of accumulation / emission time and temperature distribution. These discrepancies are attributed to two key uncertain parameters in the simulation model: the water vapor condensation coefficient and the wall equivalent convective heat transfer coefficient. Using optimization algorithms or manual iteration, continuously adjust the values ​​of these two parameters, rerun the simulation, until the error between the simulation results and the experimental data for a certain operating condition (e.g., operating condition C: extreme cold operation) is less than a preset value (e.g., ±10%), thus completing the model calibration for that operating condition.

[0061] 2. Model Validation: Using the condensation coefficient and heat transfer coefficient model calibrated under operating condition C, directly predict the experimental results for the other three operating conditions (A, B, and D) that were not calibrated. If the error between the predicted and experimental values ​​is also within an acceptable range, it proves that the simulation model has achieved high-fidelity prediction capability and the calibration is successful. If the error is large, the boundary conditions or physical model need to be re-examined, and the above process needs to be repeated.

[0062] 3. Final plan confirmed: Using the experimentally verified, high-fidelity simulation model described above, the optimized hydrogen vent diameter initially determined in step two was subjected to final verification simulations covering all design conditions (-40℃ to 40℃, full speed range). Only the scheme that meets the safety logic requirements under all conditions (i.e., reliably opens at a concentration of 2% and can reduce to below 0.2% within a specified time), and whose opening size is the minimum feasible value structurally, was finally confirmed as the calibrated optimal hydrogen vent design.

[0063] The minimum effective emission area of ​​the hydrogen exhaust port, the duration of solenoid valve opening, and the hydrogen exhaust flow rate, obtained through simulation-calibration iterative verification, are stored as preset parameters in the vehicle control system for use by the hydrogen exhaust control method.

Claims

1. A fuel cell exhaust gas cooling structure, comprising a fuel cell disposed on the roof of a vehicle, characterized in that, It also includes roof exhaust pipes, roof fairings, and endwall exhaust pipes; The roof fairing has a through-type cavity inside; The exhaust pipe on the roof connects the fuel cell to the cavity of the roof fairing, and delivers the exhaust gas into the cavity of the fairing. The end wall tailpipe connects the cavity of the guide shroud with the space under the vehicle, and the cooled exhaust gas is discharged to the under-vehicle rail surface through the end wall tailpipe.

2. The fuel cell exhaust gas cooling structure according to claim 1, characterized in that, The roof exhaust pipe is divided into two sections: the system-side exhaust pipe and the fairing-side exhaust pipe. One end of the system-side tailpipe is connected to the fuel cell, and the other end branches out to the first and second positions of the vehicle body; one end of the fairing-side tailpipe is connected to the system-side tailpipe, and the other end extends into the cavity of the corresponding side roof fairing; the system-side tailpipe and the fairing-side tailpipe are connected by a rubber tube.

3. The fuel cell exhaust gas cooling structure according to claim 2, characterized in that, The system side exhaust pipe is fixed to the pre-set mounting base on the roof, and the fairing side exhaust pipe is fixedly connected to the fairing using fasteners through the fairing's reserved flange.

4. The fuel cell exhaust gas cooling structure according to claim 2, characterized in that, It also includes an overflow pipe, which is welded to the tailpipe on the side of the fairing near the flange interface of the fairing, with the other end of the overflow pipe suspended above the roof surface.

5. The fuel cell exhaust gas cooling structure according to claim 1, characterized in that, The roof fairing has a segmented structure. The cavities of two adjacent roof fairing segments are sealed and connected by flanges and fasteners, and a sealing gasket is added between the flanges.

6. The fuel cell exhaust gas cooling structure according to claim 1, characterized in that, The cavity is detachably fixed inside the roof fairing by fasteners; the inner wall of the cavity is provided with an anti-rust treatment layer.

7. The fuel cell exhaust gas cooling structure according to claim 1, characterized in that, The bottom of the cavity of the roof deflector is formed with a U-shaped water collection trough; along the length of the train, the bottom surface of the water collection trough is provided with a 0.5° inclined slope, with the higher part of the slope facing the fuel cell and the lower part of the slope facing the tailpipe of the end wall.

8. The fuel cell exhaust gas cooling structure according to claim 1, characterized in that, The top of the cavity of the roof diffuser has at least two circular hydrogen vents, and each hydrogen vent is equipped with a solenoid valve; the solenoid valve is used to control the opening and closing of the hydrogen vent.

9. The fuel cell exhaust gas cooling structure according to claim 1, characterized in that, The tailpipes on the sides of the duct converge at the end wall of the vehicle body and then connect to the end wall tailpipe, with the outlet of the end wall tailpipe facing the ground.

10. A method for hydrogen removal from a fuel cell exhaust gas cooling structure, characterized in that, Includes the following steps: S1, fuel cell electric start; S2. Calculate the hydrogen concentration in the cavity of the roof fairing; S3. Based on the current hydrogen concentration in the cavity of the roof fairing, if the hydrogen concentration in the cavity is ≥2%, the solenoid valve will open. The opening time of the solenoid valve is determined according to the cavity volume and the size of the hydrogen vent. If the hydrogen concentration in the cavity is <2%, the hydrogen concentration in the cavity will continue to accumulate. S4. After the solenoid valve is opened, the hydrogen concentration in the cavity is continuously monitored. When the hydrogen concentration inside the cavity drops to ≤0.2%, the solenoid valve is closed, the timer is reset, and the process returns to step S2 to continue. S5. When the fuel cell shuts down, the solenoid valve remains open; after shutdown, the solenoid valve closes, ending the process.

11. The hydrogen removal method for a fuel cell exhaust gas cooling structure according to claim 10, characterized in that, Step S2 specifically involves: The parameters affecting the hydrogen concentration in the cavity of the roof fairing are obtained, including fuel cell operating conditions, fuel cell hydrogen utilization rate, operating temperature and pressure. For a fixed-model fuel cell, the hydrogen emissions under different operating conditions are calibrated to generate a MAP diagram; When the fuel cell is running, it retrieves a pre-stored MAP map and queries the hydrogen emissions based on the current operating conditions. The hydrogen concentration in the cavity of the roof fairing is calculated by combining the size of the cavity and the amount of hydrogen emitted.

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