Critical mode ejector for fuel cell hydrogen recycle system and design method

Abstract

The application discloses a design method and system of a critical mode ejector suitable for a hydrogen circulation system of a fuel cell, and comprises the following steps: obtaining a primary flow mass flow rate of a nozzle throat based on a fuel cell anode channel mass conservation equation; calculating a nozzle throat diameter; determining a nozzle outlet diameter and a nozzle outlet position; judging whether a critical back pressure of the ejector is higher than a corresponding anode inlet pressure; if yes, judging whether a hydrogen recirculation ratio meets a requirement; otherwise, changing the highest and lowest working pressures of the primary flow of the ejector, and recalculating the nozzle throat diameter, the nozzle outlet diameter and the nozzle outlet position; if the hydrogen recirculation ratio meets the requirement, the design of the ejector is completed; otherwise, changing the diameter, length and length of a diffusion chamber of an equal-area mixing chamber until the hydrogen recirculation ratio meets the requirement, and the design of the ejector is completed. The application is helpful to the critical mode ejector design of a fuel cell system under variable working conditions.

Description

Technical Field

[0001] This invention relates to the field of ejector technology, and more particularly to a critical mode ejector and design method suitable for fuel cell hydrogen cycle systems. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] A proton exchange membrane fuel cell (PEMFC) is an energy conversion device that converts the chemical energy of fuel into electrical energy. Due to its advantages such as high efficiency, fast start-up, high power density, and low operating noise, it has become a green alternative to internal combustion engines as the power source for automobiles. PEMFCs generally use an excess hydrogen supply, inevitably leading to the waste of unreacted hydrogen. Therefore, it is necessary to recover and reuse unreacted hydrogen. The hydrogen supply cycle system, as an important component of PEMFCs, mainly functions to improve hydrogen utilization and improve the internal wettability of the fuel cell stack. Two common methods for recovering unreacted hydrogen are mechanical pumps and ejectors. Ejectors, due to their simple structure, low noise, lack of moving parts, and no additional energy consumption, have become a current research hotspot.

[0004] Previous research and exploration have yielded significant progress in the theoretical study, structural design, and expansion of the operating range of hydrogen recirculation ejectors. However, a review of these studies reveals that most have focused on improving recirculation capacity and expanding the operating range, without adequately considering whether the ejector operates in critical mode. Simply pursuing improved recirculation capacity may lead the ejector to operate in subcritical mode, thereby reducing robustness, i.e., stability under fluctuating conditions. If the hydrogen recirculation ejector is designed for critical or subcritical operation, any deviation from the design conditions, such as power output variations or anode inlet and outlet pressure fluctuations caused by purging, will significantly alter the ejector's recirculation capacity. This could negatively impact the stability, efficiency, and lifespan of the fuel cell. Summary of the Invention

[0005] To address the aforementioned issues, this invention proposes a critical mode ejector and its design method suitable for fuel cell hydrogen cycle systems. Based on the ejector gas thermodynamic equation, critical mode ejectors suitable for different power levels can be designed by adjusting the set hydrogen supply pressure according to the applicable fuel cell operating parameters, thus exhibiting general applicability.

[0006] In some implementations, the following technical solutions are adopted:

[0007] A design method for a critical mode ejector suitable for a fuel cell hydrogen cycle system includes:

[0008] Determine the operating parameters of the fuel cell;

[0009] Based on the mass conservation equation of the fuel cell anode channel, the mass flow rate of hydrogen consumed by the anode is calculated, and then the primary flow mass flow rate of the nozzle throat is obtained.

[0010] Calculate the relative pressure and critical gas velocity at the nozzle throat, and combine this with the primary flow mass flow rate to calculate the nozzle throat diameter; use the Sokolov one-dimensional ejector model to determine the nozzle outlet diameter and nozzle outlet position.

[0011] The diameter, length, and diffusion chamber length of the equal-area mixing chamber are determined based on experience.

[0012] Determine whether the critical back pressure of the ejector is higher than the corresponding anode inlet pressure. If so, continue to determine whether the hydrogen recirculation ratio meets the requirements. Otherwise, change the highest and lowest operating pressures of the ejector primary flow and recalculate the nozzle throat diameter, nozzle outlet diameter, and nozzle outlet position.

[0013] If the hydrogen recirculation ratio meets the requirements, the ejector design is complete. Otherwise, change the diameter, length, and diffusion chamber length of the equal-area mixing chamber until the hydrogen recirculation ratio meets the requirements, and the ejector design is complete.

[0014] In other embodiments, the following technical solutions are adopted:

[0015] A design system for a critical mode ejector suitable for a fuel cell hydrogen cycle system includes:

[0016] The parameter acquisition module is used to determine the operating parameters of the fuel cell; the parameter calculation module is used to calculate the mass flow rate of hydrogen consumed by the anode based on the mass conservation equation of the fuel cell anode channel, and then obtain the primary flow mass flow rate of the nozzle throat.

[0017] Calculate the relative pressure and critical gas velocity at the nozzle throat, and combine this with the primary flow mass flow rate to calculate the nozzle throat diameter; use the Sokolov one-dimensional ejector model to determine the nozzle outlet diameter and nozzle outlet position.

[0018] The diameter, length, and diffusion chamber length of the equal-area mixing chamber are determined based on experience.

[0019] The judgment and optimization module is used to determine whether the critical back pressure of the ejector is higher than the corresponding anode inlet pressure. If so, it continues to determine whether the hydrogen recirculation ratio meets the requirements; otherwise, it changes the highest and lowest operating pressures of the ejector primary flow and recalculates the nozzle throat diameter, nozzle outlet diameter, and nozzle outlet position.

[0020] If the hydrogen recirculation ratio meets the requirements, the ejector design is complete. Otherwise, change the diameter, length, and diffusion chamber length of the equal-area mixing chamber until the hydrogen recirculation ratio meets the requirements, and the ejector design is complete.

[0021] In other embodiments, the following technical solutions are adopted:

[0022] A critical mode ejector suitable for a fuel cell hydrogen cycle system is designed using the above-mentioned design method. The critical mode ejector structure includes: a primary flow inlet pipe, a suction chamber, an isobaric mixing chamber, an isoarea mixing chamber, a diffusion chamber, and an ejector outlet pipe connected sequentially along the axis; a nozzle is connected to the outlet of the primary flow pipe, passes through the suction chamber, and enters the isobaric mixing chamber; a secondary flow pipe is located at the lower part of the isobaric mixing chamber and communicates with the isobaric mixing chamber.

[0023] In other embodiments, the following technical solutions are adopted:

[0024] A fuel cell hydrogen supply cycle system based on a critical mode ejector includes: a high-pressure hydrogen tank, a critical mode ejector, and a fuel cell; the high-pressure hydrogen tank is connected to the critical mode ejector in sequence through a pressure reducing valve and a proportional valve, the critical mode ejector is connected to the anode of the fuel cell stack, and the anode of the fuel cell stack is connected to the critical mode ejector in sequence through an anode outlet pipe, a gas-water separator, and a circulating gas pipe.

[0025] The proportional valve is used to control the inlet pressure of the primary flow inlet pipe. By adjusting the hydrogen supply flow rate of the ejector through the proportional valve, the hydrogen supply and circulation requirements within different power output ranges can be met.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] (1) The critical mode ejector of the present invention can meet the hydrogen supply and circulation requirements in different power output ranges by adjusting the hydrogen supply flow rate of the ejector through a proportional valve. Since the ejector works in critical mode, it can still maintain a stable and efficient hydrogen supply and circulation when the stack power is switched or the pressure of the stack inlet and outlet fluctuates due to the purging of product water. This helps to promote the widespread application of the ejector in fuel cells.

[0028] (2) The critical mode ejector optimization design method of the present invention includes a nozzle structure design method and an overall ejector structure optimization method. Based on the ejector gas thermodynamic equation, critical mode ejectors suitable for different power levels can be designed by adjusting the set hydrogen supply pressure according to the applicable fuel cell power, which has general applicability. In addition, based on the importance of the ejector geometry to its performance and combined with ejector evaluation indicators, a structural optimization method for the ejector is proposed, which is helpful for the design of critical mode ejectors for fuel cell systems operating under varying conditions.

[0029] Other features and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the critical mode ejector structure in an embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram of the hydrogen supply cycle system for a fuel cell based on a critical mode ejector in an embodiment of the present invention;

[0032] Figure 3 This is a schematic diagram of the ejector's working mode in an embodiment of the present invention;

[0033] Figure 4 This is a schematic diagram showing the change of ejector characteristic curves with primary flow pressure in an embodiment of the present invention;

[0034] Figure 5 This is a flowchart illustrating the structural design of the critical mode ejector in an embodiment of the present invention.

[0035] Among them, 1. Primary flow pipe, 2. Intake chamber, 3. Nozzle, 4. Secondary flow pipe, 5. Isobaric mixing chamber, 6. Isoare mixing chamber, 7. Diffusion chamber, 8. Ejector outlet pipe, 9. Pressure reducing valve, 10. Proportional valve, 11. Critical mode ejector, 12. Fuel cell stack anode, 13. Proton exchange membrane, 14. Fuel cell stack cathode, 15. Anode inlet pipe, 16. Anode outlet pipe, 17. Circulating gas pipe, 18. Cathode inlet pipe, 19. Cathode outlet pipe, 20. Gas-water separator, 21. Exhaust valve, 22. High-pressure hydrogen tank. Detailed Implementation

[0036] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0037] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0038] Example 1

[0039] In one or more embodiments, a design method for a critical mode ejector suitable for a fuel cell hydrogen cycle system is disclosed, combined with Figure 5 Specifically, it includes the following processes:

[0040] (1) Determine the operating parameters of the fuel cell; the operating parameters include at least the output power P of the PEMFC stack. stack The number of cells N in a PEMFC stack cell Battery operating current I and single-cell voltage V c wait.

[0041] (2) Based on the mass conservation equation of the fuel cell anode channel, calculate the mass flow rate of hydrogen consumed by the anode, and then obtain the primary flow mass flow rate of the nozzle throat.

[0042] (3) Calculate the relative pressure and critical gas velocity at the nozzle throat, and calculate the nozzle throat diameter in combination with the primary flow mass flow rate; use the Sokolov one-dimensional ejector model to determine the nozzle outlet diameter and nozzle outlet position.

[0043] (4) Determine the diameter D of the equal-area mixing chamber based on experience. m、 Equal area mixing chamber length L m and diffusion chamber length L d .

[0044] (5) Determine whether the critical back pressure of the ejector is higher than the corresponding anode inlet pressure. If so, continue to determine whether the hydrogen recirculation ratio meets the requirements; otherwise, change the maximum operating pressure p of the ejector primary flow. p,max and the minimum operating pressure p of the ejector primary flow p,min Recalculate the nozzle throat diameter, nozzle outlet diameter, and nozzle outlet position; where p p,max according to Figure 2 The maximum output pressure of the intermediate pressure reducing valve 9 and the proportional valve 10 is used to determine the pressure; p p,min Determined based on the minimum pressure at which the ejector can function properly.

[0045] (6) If the hydrogen recirculation ratio meets the requirements, the ejector design is complete; otherwise, modify D. m Lm and L d The ejector design is completed when the hydrogen recirculation ratio meets the requirements.

[0046] The design process of this embodiment will be described in detail below.

[0047] like Figure 3 As shown, at the primary flow pressure p p and secondary flow pressure p s Under fixed conditions, the injector's operating mode depends on the back pressure p. c It can be divided into critical, subcritical, and recirculation modes. The recirculation ratio ω, also known as the ejection ratio, is defined as the ratio of the secondary flow mass flow rate to the primary flow mass flow rate. As p... c As ω increases, it initially remains constant, then decreases to 0. The corresponding operating mode changes from critical mode to subcritical mode, and the back pressure corresponding to the critical operating point is called the critical back pressure p. c* With p c If the pressure continues to increase, the operating mode changes to recirculation mode, and the ejector stops working. This is especially true if the hydrogen recirculation ejector is designed for critical or subcritical operation. Any deviation between the actual operating conditions and design conditions, such as changes in anode inlet and outlet pressures (p) caused by power output or purging variations, will affect the ejector's performance. c and p b Fluctuations in hydrogen recirculation capacity can significantly alter the recirculation capability of the injector. This can negatively impact the stability, efficiency, and lifespan of the fuel cell. Therefore, designing a hydrogen recirculation injector that can operate in critical mode under any PEMFC power load to maintain a stable hydrogen supply and circulation, as well as high efficiency, is crucial.

[0048] like Figure 4 As shown, different primary flow pressures p p ω and p c The relationship. It can be seen that the critical back pressure p c* And critical recycle ratio ω * For p p They are all very sensitive, p c* With p p It increases with the increase of ω, while ω * Then decrease, p c* Increasing the p value is beneficial for the injector to operate in critical mode. Therefore, when designing a hydrogen recirculation injector, its p value should be increased. p The value should be as high as possible, while also satisfying the ω value, to ensure that it works in critical mode.

[0049] For critical mode ejectors, nozzle design is particularly critical. The nozzle structure mainly includes the nozzle throat diameter (area), nozzle exit diameter, and nozzle exit position (NXP). Therefore, this embodiment focuses on the nozzle design process; other parameters can be determined by relevant empirical models.

[0050] Before introducing the ejector structure design, it is necessary to give the evaluation indicators of the hydrogen recirculation ejector. As the core component of the ejector-driven hydrogen supply cycle system, the performance of the hydrogen recirculation ejector directly affects the overall efficiency of the PEMFC system. To comprehensively evaluate its performance, four evaluation indicators are proposed: total recirculation ratio (ω), hydrogen recirculation ratio (ω... H2 Critical back pressure (p) at different power levels c* Applicable power range (minimum applicable power P) min ~Maximum applicable power P max The definitions and calculation methods for these indicators are as follows:

[0051] ω is often used to reflect the overall recirculation efficiency of a hydrogen recirculation ejector, and it is defined as follows.

[0052]

[0053] Where, m p It is the primary flow mass flow rate, m s It is the secondary mass flow rate. This represents the excess hydrogen ratio.

[0054] Because the anode outlet gas of the ejector-driven hydrogen supply cycle system contains hydrogen and water vapor, the hydrogen recirculation ratio is higher. To evaluate hydrogen recirculation capability, the calculation formula is as follows:

[0055]

[0056]

[0057]

[0058] In the equation, This represents the mass fraction of hydrogen in the secondary stream. These represent the mole fraction and molar mass of hydrogen and water vapor, respectively; RH is the relative humidity of the secondary flow; p Sat It is the saturated vapor pressure.

[0059] Generally, ejector-driven hydrogen supply cycles require excess hydrogen to improve hydrogen utilization, enhance electrochemical reactions, and remove product water. Therefore, the minimum λ... H2 It is usually set to 1.5, corresponding to ω. H2 Greater than 0.5.

[0060] Furthermore, as mentioned earlier, if a hydrogen recirculation ejector is designed for critical or subcritical operation, deviations from the design conditions in actual operation will significantly impact the ejector's recirculation capability. To ensure a stable hydrogen supply and efficient recirculation performance, the critical back pressure p of the ejector is crucial under different power output conditions. c* It should be higher than the corresponding anode inlet pressure p in,anode .

[0061] Based on the above analysis, the applicable power range (P) min ~P max ) can be defined as and p c* When all requirements are met, the corresponding range of fuel cell output power.

[0062] The structural design process of the ejector will be detailed below. The anode operating parameters of the fuel cell, including hydrogen mass flow rate, temperature, and other parameters, are crucial for designing the critical mode ejector. First, the relevant model of the fuel cell anode channel is introduced as follows:

[0063] Anode channel mass conservation equation:

[0064]

[0065] in and These are the hydrogen mass flow rate at the anode inlet, the hydrogen mass flow rate at the anode outlet, and the hydrogen Faraday consumption, respectively.

[0066] In equation (5), The mass flow rate of hydrogen consumed at the anode can be expressed as:

[0067]

[0068] Where, N cell I represents the number of cells in the PEMFC stack, and I represents the operating current. P is the molar mass of hydrogen, F is the Faraday constant, and P is the molar mass of hydrogen. stack This is the output power of the PEMFC stack, V c It is the voltage of a single cell.

[0069] In PEMFC systems, an excess of stoichiometric hydrogen is required to enhance the electrochemical reaction and remove water produced by the reaction from the battery stack. Hydrogen excess ratio Defined by the following equation:

[0070]

[0071] The throat area A of the nozzle ntThe following formula can be used for calculation:

[0072]

[0073]

[0074]

[0075] Among them, A nt p is the throat area of ​​the nozzle. p and T p yes Figure 2 The pressure and temperature of the gas in the connecting pipe between the proportional valve 10 and the ejector 11; p p It is the pressure of the primary gas flow; T p κ is the temperature of the primary gas stream; v is the specific heat ratio of the primary gas stream; cr It is the critical velocity of the primary gas stream; p cr It is the relative pressure at the nozzle throat; p * It is the critical pressure of the primary gas stream; R p It is the primary flow gas constant.

[0076] Since the primary flow mass flow rate of the ejector is equal to the hydrogen consumption during the electrochemical reaction process in the PEMFC stack, therefore m p The following formula can be used to calculate it.

[0077]

[0078] Then, the nozzle exit diameter (D) can be determined using the Sokolov one-dimensional ejector model. nd ) and nozzle exit position (NXP):

[0079]

[0080]

[0081] In the formula, q nd ω' is the converted value of the primary flow mass velocity at the nozzle outlet interface, ω' is the assumed value of the recirculation ratio, which can be set to 0.60, and α is an experimental constant between 0.07 and 0.09.

[0082] The total area of ​​the nozzles is designed based on the maximum hydrogen supply flow rate required for the PEMFC system at rated power output (i.e., the hydrogen consumption required at rated power). Therefore, D nt D nd And NXP can be determined according to formulas (5) to (13), initial maximum hydrogen supply pressure (p p,maxThe parameters and applicable PEMFC stack operating conditions were calculated. Furthermore, as mentioned earlier, when designing the nozzle size, the primary flow hydrogen supply pressure should be set as high as possible while meeting the cycle ratio to ensure the ejector operates in critical mode. Other key parameters (such as D...) m、 L m and L d D can be derived from the conclusions and empirical formulas in the literature: m =(2-3)D nt L m =(4-8)D m L d =(6-10)D m Secondly, evaluate whether the ejector performance meets the requirements. If p c* Any power output greater than the corresponding p in,anode Continue with the following process. Otherwise, the maximum operating pressure p of the ejector primary flow needs to be changed. p,max and the minimum operating pressure p of the ejector primary flow p,min and structural parameters (D m L m and L d Then, determine. Does it meet the requirements? If not, change the structural parameters (D) m L m and L d ),until The requirements are met. If p c* and If all requirements are met, the design process of the ejector is complete.

[0083] If the operating conditions of the critical mode ejector change, i.e., when the fuel cell operating conditions change, the hydrogen supply pressure range can be adjusted according to the changes in the stack parameters, and the initial ejector dimensions can be redesigned according to the above process. This allows for the design of critical mode ejectors suitable for different power outputs, and this design method has general applicability. Specifically, the maximum hydrogen supply pressure determines the maximum fuel cell output power for which the ejector is applicable, while the minimum hydrogen supply pressure determines the minimum output power.

[0084] The cyclic performance of the ejector in this embodiment is related not only to the operating pressure but also to its geometric parameters. For a critical mode ejector, the nozzle throat diameter determines the ejector's operating range, while the ratio of the equal-area mixing chamber diameter to the nozzle throat diameter is a crucial parameter determining the ejector's cyclic performance. Therefore, the nozzle's structural dimensions and the equal-area mixing chamber diameter are the first-tier optimization parameters for the critical mode ejector. Secondly, since the primary and secondary flows require sufficient time and space to achieve adequate mixing before entering the diffusion chamber, the equal-area mixing chamber length and nozzle outlet position also play a significant role in the cyclic performance of the critical mode ejector, making them the second-tier optimization targets. Finally, other geometric parameters, such as the isobaric mixing chamber, diffusion chamber, suction chamber, and secondary flow inlet pipe structure, have the least impact on its ejection performance, making them the third-tier optimization parameters. Furthermore, during the optimization of each parameter, the ejector evaluation indices proposed above—namely, the ejection ratio, critical back pressure, and applicable power range (minimum and maximum applicable power)—can be used to evaluate whether each geometric parameter is optimal.

[0085] Example 2

[0086] In one or more embodiments, a design system for a critical mode ejector suitable for a fuel cell hydrogen cycle system is disclosed, comprising:

[0087] The parameter acquisition module is used to determine the operating parameters of the fuel cell; the parameter calculation module is used to calculate the mass flow rate of hydrogen consumed by the anode based on the mass conservation equation of the fuel cell anode channel, and then obtain the primary flow mass flow rate of the nozzle throat.

[0088] Calculate the relative pressure and critical gas velocity at the nozzle throat, and combine this with the primary flow mass flow rate to calculate the nozzle throat diameter; use the Sokolov one-dimensional ejector model to determine the nozzle outlet diameter and nozzle outlet position.

[0089] The diameter, length, and diffusion chamber length of the equal-area mixing chamber are determined based on experience.

[0090] The judgment and optimization module is used to determine whether the critical back pressure of the ejector is higher than the corresponding anode inlet pressure. If so, it continues to determine whether the hydrogen recirculation ratio meets the requirements; otherwise, it changes the highest and lowest operating pressures of the ejector primary flow and recalculates the nozzle throat diameter, nozzle outlet diameter, and nozzle outlet position.

[0091] If the hydrogen recirculation ratio meets the requirements, the ejector design is complete. Otherwise, change the diameter, length, and diffusion chamber length of the equal-area mixing chamber until the hydrogen recirculation ratio meets the requirements, and the ejector design is complete.

[0092] The specific implementation methods of the above modules are the same as those in Example 1, and will not be described in detail again.

[0093] Example 3

[0094] In one or more embodiments, a critical mode ejector suitable for a fuel cell hydrogen cycle system is disclosed, with parameter design performed using the design method described in Embodiment 1; combined with Figure 1 The critical mode ejector structure includes: a primary flow inlet pipe 1, a suction chamber 2, an isobaric mixing chamber 5, an isoarea mixing chamber 6, a diffusion chamber 7, and an ejector outlet pipe 8 connected sequentially along the axis; a nozzle 3 is connected to the outlet of the primary flow pipe, passes through the suction chamber and enters the isobaric mixing chamber 5; a secondary flow pipe 4 is located at the lower part of the isobaric mixing chamber 5 and communicates with the isobaric mixing chamber 5.

[0095] The main function of the ejector is to use a high-pressure primary flow to eject a low-pressure secondary flow and increase the pressure of the secondary flow. The specific working process is as follows: First, the high-pressure, high-speed gas (the primary flow of the ejector) gradually increases in velocity and decreases in pressure as it passes through the nozzle, reaching the speed of sound at the nozzle throat. Then, the fluid velocity continues to increase, reaching its maximum at the nozzle outlet. Next, the primary fluid flows out of the nozzle, generating a shock wave in the mixing chamber and forming a low-pressure zone at the nozzle outlet, drawing the low-pressure secondary flow into the suction chamber. Subsequently, the two fluids continuously mix in the mixing chamber, generating a shock wave in the diffusion chamber. As the velocity decreases and the pressure increases, the flow stabilizes at the outlet, achieving the suction and pressurization of the secondary flow.

[0096] Example 4

[0097] In one or more embodiments, a fuel cell hydrogen supply cycle system based on the critical mode ejector described in Embodiment 3 is disclosed, combined with Figure 2 Specifically, it includes: a high-pressure hydrogen tank 22, a critical mode ejector 11, and a fuel cell; the high-pressure hydrogen tank is connected to the critical mode ejector 11 in sequence through a pressure reducing valve 9 and a proportional valve 10; the critical mode ejector 11 is connected to the fuel cell stack anode 12 through an anode inlet pipe 15; the fuel cell stack anode 12 is connected to the critical mode ejector 11 in sequence through an anode outlet pipe 16, a gas-water separator 20, and a recirculating gas pipe 17; and the recirculating gas pipe 17 is connected to an exhaust valve 21.

[0098] The fuel cell includes a fuel cell stack anode 12, a proton exchange membrane 13, and a fuel cell stack cathode 14. The cathode inlet pipe 18 is connected to the inlet end of the fuel cell stack cathode 14, and the outlet end of the fuel cell stack cathode 14 is connected to the cathode outlet pipe 19.

[0099] In this embodiment, the proportional valve 10 is used to control the inlet pressure of the primary flow inlet pipe. By adjusting the hydrogen supply flow rate of the ejector through the proportional valve, the hydrogen supply and circulation requirements within different power output ranges can be met.

[0100] The specific working process is as follows: High-pressure hydrogen from hydrogen tank 22 (supply hydrogen, i.e., primary flow) reaches an appropriate pressure after passing through pressure reducing valve 9 and proportional valve 10, and then becomes the primary flow of the ejector. The high-pressure hydrogen is accelerated in the nozzle, forming a low-pressure area at the nozzle outlet, where unconsumed hydrogen from the stack anode 12 (anode recirculation gas, i.e., secondary flow) is entrained into the intake chamber 2. The supply hydrogen and anode recirculation gas are mixed in mixing chambers 5 and 6 and then flow into the diffusion chamber 7. At the ejector outlet, the mixed fluid reaches a higher stable pressure (stack inlet demand pressure) before entering the fuel cell stack.

[0101] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A design method for a critical mode ejector suitable for a fuel cell hydrogen cycle system, characterized in that, include: Determine the operating parameters of the fuel cell; Based on the mass conservation equation of the fuel cell anode channel, the mass flow rate of hydrogen consumed by the anode is calculated, and then the primary flow mass flow rate of the nozzle throat is obtained. Calculate the relative pressure and critical gas velocity at the nozzle throat, and then calculate the nozzle throat diameter using the primary flow mass flow rate. The nozzle exit diameter and nozzle exit position were determined using a Sokolov one-dimensional ejector model. The diameter of the equal-area mixing chamber is determined using empirical formulas. D m Length of equal area mixing chamber L m and diffusion chamber length L d ; in, D m =(2-3) D nt , L m =(4-8) D m , L d =(6-10) D m ; Determine if the critical back pressure of the ejector is higher than the corresponding anode inlet pressure. If so, further determine if the hydrogen recirculation ratio meets the requirements; otherwise, change the maximum and minimum operating pressures of the ejector primary flow. ， Recalculate the nozzle throat diameter, nozzle outlet diameter, and nozzle outlet position; If the hydrogen recirculation ratio meets the requirements, the ejector design is complete; otherwise, change the diameter of the equal-area mixing chamber, the length of the equal-area mixing chamber, and the length of the diffusion chamber until the hydrogen recirculation ratio meets the requirements, and the ejector design is complete. Specifically, the calculation of the relative pressure at the nozzle throat and the critical velocity of the primary flow gas is as follows: ； ； in, It is the pressure of the primary gas flow; It is the specific heat ratio of the primary flow of gas; It is the critical velocity of the primary gas flow; It is the relative pressure at the nozzle throat; It is the critical pressure of the primary gas flow; It is the temperature of the primary gas stream; It is the primary flow gas constant; The nozzle throat diameter is calculated as follows: ； in, A nt This represents the throat area of ​​the nozzle. It is a single-pass quality flow rate. It is the diameter of the nozzle throat. It is the relative pressure in the throat.

2. The design method of a critical mode ejector suitable for a fuel cell hydrogen cycle system as described in claim 1, characterized in that, Based on the mass conservation equation of the fuel cell anode channel, the mass flow rate of hydrogen consumed at the anode is calculated as follows: Anode channel mass conservation equation: ； in , and These are the hydrogen mass flow rates at the anode inlet, the hydrogen mass flow rates at the anode outlet, and the hydrogen mass flow rates consumed at the anode. The mass flow rate of hydrogen consumed at the anode Represented as: ； in, This refers to the number of cells in the PEMFC stack. It is the operating current. It is the molar mass of hydrogen. This refers to the output power of the PEMFC stack. It is Faraday's constant. It is the voltage of a single cell.

3. The design method of a critical mode ejector suitable for a fuel cell hydrogen cycle system as described in claim 1, characterized in that, The nozzle exit diameter and nozzle exit position are determined using the Sokolov one-dimensional ejector model, specifically as follows: ； ； in, D nd Where is the nozzle outlet diameter. NXP This refers to the nozzle exit position. This represents the throat area of ​​the nozzle. The nozzle exit area; q nd is the converted value of the primary flow mass velocity at the nozzle outlet interface, ω' is the assumed value of the recirculation ratio, and α is an experimental constant between 0.07 and 0.

09.

4. The design method of a critical mode ejector suitable for a fuel cell hydrogen cycle system as described in claim 1, characterized in that, If the operating conditions of the critical mode ejector change, i.e., when the fuel cell operating conditions change, the operating pressure range of the primary flow of the ejector can be changed according to the changes in the stack parameters, and the initial ejector size can be redesigned.

5. A design system for a critical mode ejector suitable for a fuel cell hydrogen cycle system, characterized in that, include: The parameter acquisition module is used to determine the operating parameters of the fuel cell; The parameter calculation module is used to calculate the mass flow rate of hydrogen consumed by the anode based on the mass conservation equation of the fuel cell anode channel, and then obtain the primary flow mass flow rate of the nozzle throat. Calculate the relative pressure and critical gas velocity at the nozzle throat, and then calculate the nozzle throat diameter using the primary flow mass flow rate. The nozzle exit diameter and nozzle exit position were determined using a Sokolov one-dimensional ejector model. The diameter of the equal-area mixing chamber is determined using empirical formulas. D m Length of equal area mixing chamber L m and diffusion chamber length L d ; in, D m =(2-3) D nt , L m =(4-8) D m , L d =(6-10) D m ; The optimization module determines whether the critical back pressure of the ejector is higher than the corresponding anode inlet pressure. If so, it further determines whether the hydrogen recirculation ratio meets the requirements; otherwise, it adjusts the maximum and minimum operating pressures of the ejector primary flow. ， Recalculate the nozzle throat diameter, nozzle outlet diameter, and nozzle outlet position; If the hydrogen recirculation ratio meets the requirements, the ejector design is complete; otherwise, change the diameter of the equal-area mixing chamber, the length of the equal-area mixing chamber, and the length of the diffusion chamber until the hydrogen recirculation ratio meets the requirements, and the ejector design is complete. Specifically, the calculation of the relative pressure at the nozzle throat and the critical velocity of the primary flow gas is as follows: ； ； in, It is the pressure of the primary gas flow; It is the specific heat ratio of the primary flow of gas; It is the critical velocity of the primary gas flow; It is the relative pressure at the nozzle throat; It is the critical pressure of the primary gas flow; It is the temperature of the primary gas stream; It is the primary flow gas constant; The nozzle throat diameter is calculated as follows: ； in, A nt This represents the throat area of ​​the nozzle. It is a single-pass quality flow rate. It is the diameter of the nozzle throat. It is the relative pressure in the throat.

6. A critical mode ejector suitable for a fuel cell hydrogen cycle system, characterized in that, The parameter design is performed using the design method described in any one of claims 1-4; the critical mode ejector structure includes: a primary flow inlet pipe, a suction chamber, an isobaric mixing chamber, an isoarea mixing chamber, a diffusion chamber, and an ejector outlet pipe connected sequentially along the axis; a nozzle is connected to the outlet of the primary flow pipe, passes through the suction chamber, and enters the isobaric mixing chamber; a secondary flow pipe is disposed at the lower part of the isobaric mixing chamber and communicates with the isobaric mixing chamber.

7. A fuel cell hydrogen supply cycle system based on the critical mode ejector of claim 6, characterized in that, include: High-pressure hydrogen tanks, critical mode ejectors, and fuel cells; The high-pressure hydrogen tank is connected to the critical mode ejector in sequence through a pressure reducing valve and a proportional valve. The critical mode ejector is connected to the anode of the fuel cell stack. The anode of the fuel cell stack is connected to the critical mode ejector in sequence through an anode outlet pipe, a gas-water separator, and a circulating gas pipe.

8. The fuel cell hydrogen supply cycle system for the critical mode ejector as described in claim 7, characterized in that, The proportional valve is used to control the inlet pressure of the primary flow inlet pipe. By adjusting the hydrogen supply flow rate of the ejector through the proportional valve, the hydrogen supply and circulation requirements within different power output ranges can be met.

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