Hydrogen circulation system and method based on cooperative control of ejector and ejector

Abstract

The invention discloses a hydrogen circulation system and method based on cooperative control of an ejector and an ejector, hydrogen enters a fuel cell after respectively leading to the ejector and the hydrogen ejector through a hydrogen manifold, and the method comprises the following steps: calculating a hydrogen circulation demand target value based on a real-time state of an electric pile, a critical icing temperature and a weight coefficient; the working modes of the ejector and the ejector are dynamically distributed according to a hydrogen circulation demand target value, and the working modes include a high-load steady-state mode 1, when Qtarget is larger than or equal to 80% Qmax, only the ejector works, and a controller adjusts the throat area of the ejector to enable the actual flow Qact to track the target value; in the medium-low load mode 2, when Qtarget is larger than or equal to 30% Qmax and smaller than 80% Qmax, the ejector performs master control, and the ejector performs intermittent air supply according to the duty ratio D = Kp. (Qtarget-Qact); in the extremely low load / cold start mode 3, when 30% Qmax is smaller than Qtarget or Tenv is smaller than-15 DEG C, the ejector is closed, the flow is fully controlled by the ejector, and meanwhile, a stack waste heat circulation preheating pipeline is started; and online optimizing and dynamically updating through fuzzy PID. By means of the hydrodynamic design without rotating parts, efficient hydrogen circulation and dynamic flow adjustment are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cells, and particularly relates to a hydrogen circulation system and method based on the collaborative control of an ejector and an injector. Background Art

[0002] As an efficient and clean energy conversion device, the core of a fuel cell is to directly generate electrical energy through hydrogen-oxygen electrochemical reactions. In a fuel cell system, the hydrogen circulation subsystem is a key component for maintaining reaction efficiency. In traditional technologies, hydrogen circulation pumps (such as centrifugal pumps or roots pumps) are widely used to drive unreacted hydrogen to flow back from the anode outlet to the inlet to achieve the recycling of hydrogen and avoid a decrease in battery performance caused by local concentration unevenness.

[0003] However, the existing technologies have the following significant defects: Power consumption problem: The hydrogen circulation pump needs to be driven by an external motor, and its energy consumption accounts for 5%-10% of the total power consumption of the fuel cell system. Especially under low-load conditions, the efficiency of the pump decreases significantly, resulting in energy waste. Noise and vibration: The high-speed rotation of the impeller inside the circulation pump (usually with a rotational speed exceeding 10,000 rpm) generates high-frequency mechanical noise (about 70-85 dB), and the vibration may affect the reliability of other components in the system. Poor low-temperature adaptability: In a low-temperature environment (such as -30°C), the impeller and sealing structure of the circulation pump are prone to jamming due to the freezing of condensed water, resulting in system startup failure or performance degradation. High maintenance cost: The mechanical wear of rotating components (such as bearings and sealing rings) needs to be replaced regularly, increasing the life-cycle cost.

[0004] In the existing technologies, a scheme of using an ejector to replace the circulation pump has been tried. Although it can reduce power consumption, the ejector efficiency drops sharply under low-flow conditions, resulting in insufficient hydrogen reflux and an increased risk of anode flooding. Summary of the Invention

[0005] To solve the above problems, the present invention proposes a hydrogen circulation system and method based on the collaborative control of an ejector and an injector, which realizes efficient hydrogen circulation and dynamic flow regulation through a hydrodynamic design without rotating components.

[0006] To achieve the above object, the technical solution adopted by the present invention is: A hydrogen circulation method based on the collaborative control of an ejector and an injector, the hydrogen circulation system on which is composed of an ejector and a hydrogen injector, and the two are in a parallel relationship. Hydrogen enters the fuel cell after passing through the hydrogen manifold to the ejector and the hydrogen injector respectively. Based on a fuzzy PID multi-variable collaborative controller, by real-time monitoring the real-time state of the stack, the duty ratio of the injector and the throat opening of the ejector are dynamically optimized, including the steps of:

[0007] Calculating the hydrogen circulation demand target value Q based on the real-time state of the stack, the critical freezing temperature, and the weight coefficient target ;

[0008] According to the target value Q of hydrogen circulation demand target Dynamically allocate the working modes of the ejector and the injector, including:

[0009] High-load steady-state mode 1: When Q target ≥80%Q max At this time, only the ejector works, and the controller adjusts the throat area of the ejector to make the actual flow rate Q act Track the target value;

[0010] Medium and low-load mode 2: When 30%Q max ≤Q target <80%Q max , the ejector is the main controller, and the injector intermittently supplements gas according to the duty cycle D = K p ·(Q target -Q act );

[0011] Very low-load / cold start mode 3: When 30%Q max <Q target Or T env <-15°C, turn off the ejector, and the injector fully controls the flow rate. At the same time, start the waste heat circulation preheating pipeline of the stack;

[0012] Among them, Q max Is the maximum hydrogen supply of the ejector, T env Is the ambient temperature, Q act Is the actual flow rate, K p Is the proportionality coefficient;

[0013] Dynamically update through fuzzy PID online optimization.

[0014] Furthermore, the real-time state of the stack includes current, temperature and pressure difference.

[0015] Furthermore, the target value Q of hydrogen circulation demand target , the calculation formula is:

[0016] Q target =k1·I stack +k2·(T anode -T crit )+k3·ΔP membrane ;

[0017] Among them: I stack Is the stack output current; T anode Is the anode inlet temperature; T crit Is the critical freezing temperature; ΔP membrane Is the pressure difference across the proton exchange membrane; k1, k2, k3 are weighting coefficients.

[0018] Furthermore, the dynamic update rule of the fuzzy PID algorithm is as follows:

[0019] Obtain the flow deviation e(t) and the deviation change rate Δe(t) according to the system state:

[0020] e(t) = Q target -Q act ;

[0021] Δe(t) = e(t) - e(t - 1);

[0022] where Q target is the target value of the hydrogen circulation demand, and Q act is the actual flow rate;

[0023] Divide e(t) and Δe(t) into 7 fuzzy sets (NB, NM, NS, ZO, PS, PM, PB), and trigger different membership functions according to different e(t) and Δe(t) values to obtain:

[0024] (1) The correction amount of the ejector throat opening is:

[0025] ΔA = K P1 ·e(t) + K I1 ·∫e(t)dt + K D1 ·Δe(t)

[0026] (3) The correction amount of the ejector frequency is:

[0027] Δf = K P2 ·e(t) + K I2 ·∫e(t)dt + K D2 ·Δe(t)

[0028] where K P1 , K I1 , K D1 , K P2 , K I2 , K D2 are correction coefficients.

[0029] Furthermore, it also includes that when a sensor anomaly is detected, switch to the estimation algorithm for inferring the hydrogen concentration based on the stack voltage to continue ensuring the system operation.

[0030] Furthermore, the estimation algorithm for inferring the hydrogen concentration based on the stack voltage is:

[0031]

[0032] where V ocv is the open-circuit voltage, F is the Faraday constant, V cell is the single-cell voltage, and T stackT is the stack temperature, and R is the universal gas constant.

[0033] On the other hand, the present invention also provides a hydrogen circulation system based on the coordinated control of an ejector and an injector, including a hydrogen manifold, an ejector, and a hydrogen injector. The ejector and the hydrogen injector are in a parallel relationship. Hydrogen enters the fuel cell after passing through the hydrogen manifold to the ejector and the hydrogen injector respectively; a multivariable coordinated controller based on fuzzy PID dynamically optimizes the duty ratio of the injector and the throat opening of the ejector by real-time monitoring of the real-time state of the stack.

[0034] Furthermore, the ejector adopts a Laval nozzle with a throat diameter of 0.5 - 2 mm and a diffuser cone angle of 8° - 12°, and the material is hydrogen embrittlement-resistant 316L stainless steel; the hydrogen injector integrates a high-frequency solenoid valve and a microporous nozzle, and the injection frequency is adjustable from 50 to 200 Hz.

[0035] Furthermore, the working process of the ejector includes:

[0036] High-pressure hydrogen is accelerated to supersonic speed through the nozzle, a negative pressure area is formed in the mixing chamber, the anode exhaust gas is sucked in and mixed, and then it is pressurized through the diffuser section and transported to the stack inlet; by adjusting the throat cross-sectional area of the ejector module, different flow rate requirements are matched.

[0037] Furthermore, the hydrogen injector includes two working modes;

[0038] One is the start-up stage mode: when the stack temperature is lower than 60 °C, the injector directly injects hydrogen into the stack inlet in a pulse mode to avoid insufficient ejector efficiency at low temperatures;

[0039] The other is the transient compensation mode: when the load suddenly changes and causes fluctuations in the ejector flow rate, the injector instantaneously supplements hydrogen to maintain the stability of the anode pressure.

[0040] Beneficial effects of adopting this technical solution:

[0041] The present invention uses the dynamic coupling of an ejector and an injector to supply hydrogen to the fuel cell stack, combines the high-efficiency steady-state working characteristics of the ejector with the fast response ability of the injector, and solves the "stall" problem of a single ejector at low flow rates through a working condition adaptive switching strategy. In the traditional solution, the ejector only works efficiently at a specific pressure ratio, while the present invention expands the effective working range of the ejector to the full working condition (load rate 10% - 100%) through injector compensation.

[0042] The present invention has developed a multivariable collaborative controller based on fuzzy PID. By real-time monitoring the stack current, temperature, and ejector pressure difference, it dynamically optimizes the duty ratio of the injector and the opening of the ejector throat. For example, when it is detected that the ejector efficiency decreases (pressure difference ratio < 1.2), the controller starts the injector air supplement within 50 ms, and at the same time adjusts the ejector throat area to the optimal value to ensure the stability of the circulation flow rate.

[0043] The present invention eliminates the impeller and motor of the traditional hydrogen supply device. The hydrogen circuit adopts a fully straight-through flow channel design. Combined with periodic hydrogen pulse flushing, it can effectively prevent the condensation and freezing of low-temperature water vapor. Comparative tests show that after continuous operation at -25°C for 8 hours, the pressure drop of this solution only increases by 2.7%, while the pressure drop of the traditional pump solution reaches 18%. The present invention realizes energy efficiency improvement: after canceling the hydrogen circulation pump, the system power consumption is reduced by 8% - 12%. Taking an 80kW fuel cell system as an example, the annual operating cost is reduced by about 1200 yuan (calculated at an electricity price of 0.6 yuan / kWh). The present invention effectively controls the noise: the absence of rotating parts reduces the operating noise to below 55 dB, which is about 30% lower than that of the traditional pump, meeting the vehicle-mounted noise reduction standard (GB / T 18655-2018).

[0044] The present invention enhances the reliability: the mean time between failures of the system is increased from 5000 hours to 15000 hours, and the maintenance cycle is extended by 3 times.

[0045] The present invention improves the low-temperature adaptability: in the -30°C cold start test, the ejector-assisted mode can make the anode humidity reach the working threshold within 120 seconds, which is 40% shorter than the traditional pump solution. Description of the Drawings

[0046] Figure 1 is a schematic flow chart of a hydrogen circulation method based on the collaborative control of an ejector and an injector according to the present invention;

[0047] Figure 2 is a schematic structural diagram of a hydrogen circulation system based on the collaborative control of an ejector and an injector in an embodiment of the present invention. Detailed Embodiments

[0048] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described below with reference to the accompanying drawings.

[0049] In this embodiment, refer to Figure 1As shown in the figure, the present invention proposes a hydrogen circulation method based on the coordinated control of an ejector and an injector. The hydrogen circulation system on which it is based includes an ejector and a hydrogen injector, and the two are in a parallel relationship. Hydrogen enters the fuel cell after passing through the hydrogen manifold to the ejector and the hydrogen injector respectively. A multivariable coordinated controller based on fuzzy PID dynamically optimizes the duty ratio of the injector and the throat opening of the ejector by real-time monitoring of the real-time state of the fuel cell stack, including the steps:

[0050] Calculate the target value Q of hydrogen circulation demand based on the real-time state of the fuel cell stack, the critical icing temperature, and the weight coefficient target ;

[0051] According to the target value Q of hydrogen circulation demand target Dynamically allocate the working modes of the ejector and the injector, including:

[0052] High-load steady-state mode 1: When Q target ≥80%Q max , only the ejector works, and the controller adjusts the throat area of the ejector to make the actual flow rate Q act track the target value;

[0053] Medium and low-load mode 2: When 30%Q max ≤Q target <80%Q max , the ejector is the main controller, and the injector intermittently supplements air according to the duty ratio D = K p ·(Q target -Q act );

[0054] Very low-load / cold start mode 3: When 30%Q max <Q target or T env <-15°C, turn off the ejector, and the injector fully controls the flow rate. At the same time, start the waste heat circulation preheating pipeline of the fuel cell stack;

[0055] Among them, Q max is the maximum hydrogen supply of the ejector, T env is the ambient temperature, Q act is the actual flow rate, and K p is the proportionality coefficient (typical value K p ＝0.1 );

[0056] Dynamically update through fuzzy PID online optimization.

[0057] Among them, the real-time state of the fuel cell stack includes current, temperature, and pressure difference.

[0058] As an optimized solution of the above embodiment, the target value Q of hydrogen circulation demand target , the calculation formula is:

[0059] Qtarget = k1·I stack + k2·(T anode - T crit ) + k3·ΔP membrane ;

[0060] Where: I stack is the stack output current; T anode is the anode inlet temperature; T crit is the critical icing temperature (can be set to -20 °C); ΔP membrane is the pressure difference across the proton exchange membrane; k1, k2, k3 are weighting coefficients (calibrated through experiments, typical values are k1 = 0.12, k2 = 0.05, k3 = 0.8).

[0061] As an optimized solution of the above embodiment, the dynamic update rule of the fuzzy PID algorithm is:

[0062] Obtain the flow deviation e(t) and the deviation change rate Δe(t) according to the system state:

[0063] e(t) = Q target - Q act ;

[0064] Δe(t) = e(t) - e(t - 1);

[0065] Where, Q target is the target value of the hydrogen circulation demand, Q act is the actual flow rate;

[0066] Divide e(t) and △e(t) into 7 fuzzy sets (NB, NM, NS, ZO, PS, PM, PB), and trigger different membership functions according to different e(t) and △e(t) values to obtain:

[0067] (1) The correction amount of the ejector throat opening is:

[0068] ΔA = K P1 ·e(t) + K I1 ·∫e(t)dt + K D1 ·Δe(t)

[0069] (3) The correction amount of the ejector frequency is:

[0070] Δf = K P2 ·e(t) + K I2 ·∫e(t)dt + K D2 ·Δe(t)

[0071] Where, K P1 、K I1 、K D1 、K P2, K I2 , K D2 is the correction coefficient.

[0072] K P1 , K I1 , K D1 , K P2 , K I2 , K D2 Typical values that can be taken are 0.8, 0.05, 0.3, 102, 0.02, 0.1.

[0073] As an optimized solution of the above embodiment, it further includes that when a sensor anomaly is detected, switch to an estimation algorithm for back-calculating the hydrogen concentration based on the stack voltage to continue to ensure the operation of the system.

[0074] The estimation algorithm for back-calculating the hydrogen concentration based on the stack voltage is:

[0075]

[0076] where V ocv is the open-circuit voltage, F is the Faraday constant, V cell is the single-cell voltage, T stack is the stack temperature, and R is the universal gas constant.

[0077] To cooperate with the implementation of the method of the present invention, based on the same inventive concept, as Figure 2 shown, the present invention also provides a hydrogen circulation system based on the coordinated control of an ejector and an injector, including a hydrogen manifold, an ejector, and a hydrogen injector. The ejector and the hydrogen injector are in a parallel relationship. Hydrogen enters the fuel cell after passing through the hydrogen manifold to the ejector and the hydrogen injector respectively; a multi-variable coordinated controller based on fuzzy PID dynamically optimizes the duty cycle of the injector and the throat opening of the ejector by real-time monitoring of the real-time state of the stack.

[0078] Preferably, the ejector adopts a Laval nozzle with a throat diameter of 0.5 - 2 mm, a diffuser cone angle of 8° - 12°, and the material is hydrogen embrittlement-resistant 316L stainless steel; the hydrogen injector is integrated with a high-frequency solenoid valve (response time < 5 ms) and a micro-hole nozzle (aperture 0.1 - 0.3 mm), and the injection frequency is adjustable from 50 - 200 Hz.

[0079] The working process of the ejector includes:

[0080] High-pressure hydrogen is accelerated to supersonic speed through the nozzle, a negative pressure area is formed in the mixing chamber, the anode exhaust gas is sucked in and mixed, and then it is pressurized through the diffuser section and delivered to the stack inlet; the throat cross-sectional area of the ejector module is adjusted to match different flow rate requirements.

[0081] The hydrogen injector includes two working modes;

[0082] The first is the startup phase mode: when the temperature of the fuel cell stack is lower than 60°C, the injector directly injects hydrogen into the fuel cell stack in pulse mode to avoid insufficient low-temperature injection efficiency;

[0083] The second is the transient compensation mode: when a sudden change in load causes the injection flow to fluctuate, the injector instantly replenishes hydrogen to maintain anode pressure stability.

[0084] Take an example to illustrate the implementation effect: an experiment was conducted with a 90kW vehicle-mounted fuel cell system, with a system rated power of 90kW, a working pressure of 0.45MPa, and a hydrogen flow range of 5-50g / s.

[0085] The parameters of the ejector, injector and sensor are as follows:

[0086] Ejector: throat diameter 1.2mm, material 316L, maximum ejection ratio 1.5;

[0087] Injector: nozzle aperture 0.2mm, maximum frequency 200Hz;

[0088] Sensor: Pressure sensor range 0-1MPa, temperature sensor range -40-120℃.

[0089] The test was conducted under three working conditions: normal temperature, low temperature, and transient response. The test results are as follows:

[0090] Normal temperature high load (80kW): The ejector works alone, the throat opening is 80%, the measured circulation flow is 48g / s, and the power consumption is only 32W (the traditional pump solution is 280W);

[0091] Low temperature start (-25℃): The injector runs at 70% duty cycle, and with the stack preheating, the anode humidity reaches 85% within 120 seconds without freezing;

[0092] Transient response test: When the load steps from 30% to 80%, the injector replenishes 8g / s of hydrogen within 100ms, and the anode pressure fluctuation is <3%.

[0093] The comparison of comprehensive data indicators is as follows:

[0094] Index This solution Traditional circulating pump solution Power consumption (under the condition of 80kW) 132W 780W Noise (at a distance of 1m) 53dB 78dB Starting success rate at -25°C 100％ 80％ Maintenance cycle 15000 hours 5000 hours

[0095] It can be seen that the hydrogen ejector and pseudo-injector collaborative control scheme adopted in this scheme is effective, which is beneficial to improving the overall performance of the fuel cell system and extending its service life.

[0096] The above has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A hydrogen circulation method based on the collaborative control of an ejector and an injector, characterized in that The hydrogen circulation system it is based on includes an ejector and a hydrogen injector, which are in a parallel relationship. Hydrogen passes through the hydrogen manifold to the ejector and the hydrogen injector respectively and then enters the fuel cell. The multivariable cooperative controller based on fuzzy PID dynamically optimizes the duty ratio of the injector and the throat opening of the ejector by real-time monitoring of the real-time state of the stack, including the steps: Calculate the target value Q of hydrogen circulation demand based on the real-time state of the stack, the critical freezing temperature, and the weight coefficient target ; According to the target value Q of the hydrogen circulation demand target Dynamically allocate the working modes of the ejector and the injector, including: High-load steady-state mode 1: When Q target ≥ 80% Q max , only the ejector works, and the controller adjusts the throat area of the ejector to make the actual flow rate Q act track the target value; Medium and low load mode 2: When 30%Q max ≤Q target <80%Q max , the ejector is the main controller, and the ejector intermittently supplies air according to the duty cycle D = K p ·(Q target -Q act ) Very low load / cold start mode 3: When 30% Q max <Q target or T env <-15 °C, the ejector is closed, and the flow rate is fully controlled by the ejector. At the same time, the waste heat circulation preheating pipeline of the stack is started; Among them, Q max is the maximum hydrogen supply of the ejector, T env is the ambient temperature, Q act is the actual flow rate, K p is the proportionality coefficient; Dynamically update through online optimization of fuzzy PID.

2. The hydrogen circulation method based on the collaborative control of an ejector and an injector according to claim 1, wherein The real-time state of the stack includes current, temperature and pressure difference.

3. A hydrogen circulation method based on the collaborative control of an ejector and an injector according to claim 1, characterized in that Hydrogen cycle demand target value Q target , and the calculation formula is as follows: Q target = k1·I stack + k2·(T anode - T crit ) + k3·ΔP membrane ; Where: I stack is the output current of the stack; T anode is the anode inlet temperature; T crit is the critical icing temperature; ΔP membrane is the pressure difference across the proton exchange membrane; k1, k2, and k3 are weighting coefficients.

4. A hydrogen circulation method based on the collaborative control of an ejector and an injector according to claim 1, characterized in that The dynamic update rule of the fuzzy PID algorithm is: Obtain the flow deviation e(t) and the deviation change rate Δe(t) according to the system state: e(t) = Q target -Q act ; Δe(t) = e(t) - e(t - 1); Among them, Q target is the target value of the hydrogen circulation demand, and Q act is the actual flow rate; Divide e(t) and △e(t) into 7 fuzzy sets (NB, NM, NS, ZO, PS, PM, PB), and trigger different membership functions according to different e(t) and △e(t) values to obtain: (1) The correction amount of the throat opening of the ejector is: △A = K P1 ·e(t) + K I1 ·∫e(t)dt + K D1 ·Δe(t) (3) The correction amount of the injector frequency is: Δf = K P2 ·e(t) + K I2 ·∫e(t)dt + K D2 ·Δe(t) Among them, K P1 , K I1 , K D1 , K P2 , K I2 , K D2 are correction factors.

5. A hydrogen circulation method based on the collaborative control of an ejector and an injector according to claim 1, characterized in that It also includes that when a sensor abnormality is detected, switch to an estimation algorithm for inferring the hydrogen concentration based on the stack voltage to continue to ensure the operation of the system.

6. A hydrogen circulation method based on the collaborative control of an ejector and an injector according to claim 5, characterized in that, The estimation algorithm for inferring the hydrogen concentration based on the stack voltage is: Among them, V ocv is the open-circuit voltage, F is the Faraday constant, V cell is the single-cell voltage, T stack is the stack temperature, and R is the universal gas constant.

7. A hydrogen circulation system based on the coordinated control of an ejector and an injector, characterized in that, It includes a hydrogen manifold, an ejector and a hydrogen injector. The ejector and the hydrogen injector are in a parallel relationship. Hydrogen passes through the hydrogen manifold to the ejector and the hydrogen injector respectively and then enters the fuel cell; the multivariable cooperative controller based on fuzzy PID dynamically optimizes the duty ratio of the injector and the throat opening of the ejector by real-time monitoring of the real-time state of the stack.

8. A hydrogen circulation system based on the collaborative control of an ejector and an injector according to claim 7, characterized in that, The ejector uses a Laval nozzle with a throat diameter of 0.5 - 2 mm and a diffuser cone angle of 8° - 12°. The material is 316L stainless steel resistant to hydrogen embrittlement; the hydrogen injector is integrated with a high-frequency solenoid valve and a microporous nozzle, and the injection frequency is adjustable from 50 to 200 Hz.

9. A hydrogen circulation system based on the coordinated control of an ejector and an injector according to claim 7, wherein The working process of the ejector includes: High-pressure hydrogen is accelerated to supersonic speed through the nozzle, a negative pressure area is formed in the mixing chamber, the anode tail gas is inhaled and mixed, and then it is pressurized through the diffuser section and transported to the stack inlet; the cross-sectional area of the throat of the ejector module is adjusted to match different flow requirements.

10. A hydrogen circulation method based on the collaborative control of an ejector and an injector according to claim 7, characterized in that The hydrogen injector includes two working modes; One is the start-up stage mode: when the stack temperature is lower than 60 °C, the injector directly injects hydrogen into the stack inlet in a pulse mode to avoid insufficient ejection efficiency at low temperature; The other is the transient compensation mode: when the load suddenly changes and causes fluctuations in the ejection flow, the injector instantaneously supplements hydrogen to maintain the stability of the anode pressure.

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