A low-temperature starting system for hydrogen fuel cells of unmanned aerial vehicles

Abstract

The present application relates to the technical field of UAV power systems, and in particular to a low-temperature starting system for a hydrogen fuel cell for a UAV. It comprises: a hydrogen supply subsystem, a purge actuator, a stack sensor module and a control unit. The control unit is electrically connected to the main hydrogen supply pressure reducing valve, the piezoelectric ceramic solenoid valve, the membrane electrode interface temperature sensor and the voltage detection circuit. The control unit is configured to execute the control logic: when it is detected that the membrane electrode interface temperature is lower than the safety threshold or the voltage drops suddenly, the main hydrogen supply pressure reducing valve is opened and a pulse current is applied; before the membrane electrode interface temperature rises to the threshold value allowing purge, the piezoelectric ceramic solenoid valve is prohibited from starting; after reaching the threshold value allowing purge, the main hydrogen supply pressure reducing valve is closed and the piezoelectric ceramic solenoid valve is opened for purge. It overcomes the defect that the UAV hydrogen fuel cell relies on bulky external auxiliary equipment to start in harsh low-temperature environments, realizes unassisted starting in extreme low-temperature environments, and greatly improves the endurance and operational stability of the UAV.

Description

Technical Field

[0001] The present application relates to the technical field of UAV power systems, and in particular to a low-temperature starting system for a hydrogen fuel cell for a UAV. Background Art

[0002] As a clean and efficient energy conversion device, hydrogen fuel cells, with their high energy density and zero emissions, show great potential for application in drones. The core component of a drone hydrogen fuel cell is the membrane electrode assembly (MEA), which consists of a proton exchange membrane, a catalytic layer, and a gas diffusion layer. This is where the electrochemical reaction between hydrogen and oxygen generates water, electricity, and heat. However, these fuel cell systems face severe startup challenges in low-temperature environments, particularly extreme conditions below -20°C.

[0003] At low temperatures, the water generated by the internal reactions of hydrogen fuel cells quickly freezes. The formation of ice crystals not only blocks the transport pathways for the reactants, leading to a sharp drop in reaction efficiency and output power, but more seriously, the expansion of the ice crystals can directly puncture the brittle proton exchange membrane or damage the delicate catalyst layer, causing irreversible damage to the membrane electrode and significantly shortening the battery life. To overcome the challenge of low-temperature startup, existing technologies generally rely on external auxiliary methods. One common approach is to preheat the fuel cell stack using additional heating equipment, such as heating wires or hot air devices, or to add independent high-pressure gas cylinders and complex purge circuits to forcibly remove ice blockages using high-pressure gas, typically hydrogen or inert gas. While these methods can achieve low-temperature startup to a certain extent, they inevitably introduce significant additional weight and system complexity. For weight-sensitive drone applications, adding hundreds of grams or even kilograms of auxiliary equipment is an unacceptable burden, significantly offsetting the inherent energy density advantages of hydrogen fuel cells and even rendering the system impractical. In addition, some methods fail to strictly constrain the operation timing, and apply high-voltage purge force or large current when the membrane electrode material is still in a low-temperature brittle state, which increases the risk of membrane electrode damage.

[0004] Therefore, there is an urgent need for a low-temperature start-up solution for hydrogen fuel cells suitable for drones, which can start reliably and quickly at extremely low temperatures, such as -40°C, while completely avoiding reliance on bulky external heating or independent gas source systems, ensuring minimal system weight gain, and effectively protecting the membrane electrode from low-temperature embrittlement and ice crystal damage. Summary of the Invention

[0005] In order to solve the technical problems existing in the prior art, the present application provides a low-temperature starting system for a hydrogen fuel cell for a drone, comprising:

[0006] Hydrogen supply subsystem, purge actuator, stack sensor module and control unit;

[0007] The hydrogen supply subsystem includes a hydrogen storage bottle, a main hydrogen supply pressure reducing valve and a three-way joint. The output end of the main hydrogen supply pressure reducing valve is divided into a main path connected to the membrane electrode anode inlet and a bypass connected to the purge actuator through the three-way joint;

[0008] The purge actuator comprises a piezoelectric ceramic solenoid valve connected in series and a swirl nozzle integrated at the inlet of the membrane electrode anode flow channel;

[0009] The stack sensing module includes a membrane electrode interface temperature sensor and a voltage detection circuit;

[0010] The control unit is electrically connected to the main hydrogen supply pressure reducing valve, the piezoelectric ceramic solenoid valve, the membrane electrode interface temperature sensor and the voltage detection circuit;

[0011] The control unit is configured to execute control logic:

[0012] When the membrane electrode interface temperature sensor detects that the membrane electrode interface temperature is lower than the safety threshold or the voltage detection circuit detects a voltage drop, the main hydrogen supply pressure reducing valve is opened and a pulse current is applied;

[0013] Before the membrane electrode interface temperature rises to the purge threshold, the piezoelectric ceramic solenoid valve is prohibited from being started. After the purge threshold is reached, the main hydrogen supply pressure reducing valve is closed and the piezoelectric ceramic solenoid valve is opened to purge through the swirl nozzle.

[0014] Specifically, when executing the control logic, the control unit sets the safety threshold to -25°C and sets the purge threshold to -5°C.

[0015] Specifically, when executing the control logic, the control unit takes a voltage drop greater than 10% as a criterion for detecting the voltage sudden drop.

[0016] Specifically, the outlet end of the swirl nozzle is provided with a 30° inclined surface, and the inner wall of the swirl nozzle is provided with a spiral guide groove.

[0017] Specifically, the piezoelectric ceramic solenoid valve includes a piezoelectric ceramic driving element, which generates a micro-displacement when a control voltage is applied to directly push the valve core to open and close.

[0018] Specifically, when the control unit opens the piezoelectric ceramic solenoid valve, it dynamically calculates the purge time t according to the real-time voltage recovery rate η, where η=measured voltage after purge / theoretical voltage value, and t=0.02+0.08×(1-η) seconds.

[0019] Specifically, the control unit applies a maintenance current of 0.1 A / cm² to the membrane electrode immediately after the purge is completed, and the current lasts for 60 seconds.

[0020] Specifically, a stainless steel filter with a pore size of 50 microns is built into the outlet of the swirl nozzle.

[0021] Specifically, the control unit is equipped with a plateau air pressure compensation module. When the altitude is higher than 3,000 meters, the purge hydrogen pressure is increased according to the formula P=0.3+0.001×(H-3000)MPa, where H is the altitude value.

[0022] Specifically, the membrane electrode interface temperature sensor is an embedded thermocouple, and the temperature sensing end thereof is in physical contact with the membrane electrode catalyst layer.

[0023] This application has the following technical effects:

[0024] It overcomes the fundamental defect of existing drone hydrogen fuel cells that rely on bulky external auxiliary equipment to start in harsh low-temperature environments. By ingeniously reusing the system's original hydrogen supply pipeline and applying a precisely timed pulse current heating and hydrogen direct blowing synergy mechanism, it completely eliminates the need for additional heaters or independent purge gas sources. It achieves high-reliability unassisted startup in extreme low-temperature environments, strictly limits the system weight gain to an extremely low level, and significantly reduces the risk of damage to the membrane electrode due to low-temperature embrittlement and ice crystal impact, greatly improving the drone's endurance and operational stability in extremely cold conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] By reading the detailed description below with reference to the accompanying drawings, the above and other objects, features and advantages of the exemplary embodiments of the present application will become readily understood. In the accompanying drawings, several embodiments of the present application are shown in an exemplary and non-limiting manner, and the same or corresponding numbers represent the same or corresponding parts.

[0026] Figure 1 This is a schematic structural diagram of a low-temperature starting system for a hydrogen fuel cell for a drone according to an embodiment of the present application;

[0027] Figure 2 It is a control logic diagram of the control unit in the embodiment of the present application. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application.

[0029] The demand for drones in polar scientific research and high-altitude logistics applications is increasingly urgent. A key bottleneck facing their energy systems lies in the low-temperature startup performance of hydrogen fuel cells. Existing solutions exhibit critical flaws in environments below -20°C: The generated water instantly freezes, blocking micron-sized gas flow channels. The expansion stress of the ice crystals causes cracking in the membrane electrode catalyst layer and embrittlement and perforation of the proton exchange membrane, resulting in a drastic drop in battery performance. Furthermore, conventional strategies face a dilemma: using an external electric heater to preheat the stack requires an additional thermal management module weighing at least 300g; relying on high-pressure purge de-icing requires independent gas cylinders and redundant piping, adding over 500g to the system weight. This completely contradicts the stringent demands for gram-by-gram weight reduction in drone energy systems. Critically, existing approaches generally neglect the protection of the material's critical phase transition point. When the membrane electrode interface temperature drops below -5°C, directly applying high-pressure gas purges triggers the "ice blade effect," where the high-speed hydrogen flow, carrying sharp ice crystals, impacts the catalyst layer, causing permanent mechanical damage. The core motivation of this invention is to break the technical vicious circle of "weight gain means failure, weight loss means paralysis" and reconstruct the low-temperature startup logic within the zero-weight gain framework.

[0030] Based on the above pain points, this embodiment creatively reuses the existing hydrogen supply subsystem of the drone as a de-icing energy source and provides a drone hydrogen fuel cell low-temperature starting system, such as Figure 1 Shown, including:

[0031] Hydrogen supply subsystem, purge actuator, stack sensor module and control unit;

[0032] The hydrogen supply subsystem includes a hydrogen storage bottle, a main hydrogen supply pressure reducing valve and a three-way joint. The output end of the main hydrogen supply pressure reducing valve is divided into a main line connected to the membrane electrode anode inlet and a bypass connected to the purge actuator through the three-way joint;

[0033] The purge actuator includes a piezoelectric ceramic solenoid valve connected in series and a swirl nozzle integrated at the inlet of the membrane electrode anode flow channel;

[0034] The stack sensing module includes a membrane electrode interface temperature sensor and a voltage detection circuit;

[0035] The control unit is electrically connected to the main hydrogen supply pressure reducing valve, the piezoelectric ceramic solenoid valve, the membrane electrode interface temperature sensor and the voltage detection circuit;

[0036] The control unit is configured to execute the control logic:

[0037] When the membrane electrode interface temperature sensor detects that the membrane electrode interface temperature is lower than the safety threshold or the voltage detection circuit detects a sudden voltage drop, the main hydrogen supply pressure reducing valve is opened and a pulse current is applied;

[0038] Before the membrane electrode interface temperature rises to the purge threshold, it is prohibited to start the piezoelectric ceramic solenoid valve. After reaching the purge threshold, the main hydrogen supply pressure reducing valve is closed and the piezoelectric ceramic solenoid valve is opened to purge through the swirl nozzle.

[0039] Specifically, in this embodiment, the 35 MPa high-pressure hydrogen in the hydrogen storage bottle is output to 0.3 MPa at a constant pressure through the titanium alloy main hydrogen supply pressure reducing valve, and is divided into a main path and a bypass through a three-way joint. The main path is directly connected to the membrane electrode anode inlet to maintain the basic reaction gas source, and the bypass is connected to the purge actuator. The mechanism includes a piezoelectric ceramic solenoid valve with millisecond response and an integrated swirl nozzle. Its innovation lies in that the nozzle is directly processed on the inlet wall of the membrane electrode anode flow channel with an embedded structure, and a spiral guide groove is opened on the inner wall and a 30-degree inclination outlet is set. This one-piece flow channel design completely eliminates the risk of sealing failure of traditional external pipes, and the weight increase is only 1.5 grams. A 50-micron stainless steel filter is pre-installed at the outlet of the swirl nozzle. Its microporous structure has been optimized by fluid simulation to intercept impurities while ensuring that the loss of hydrogen flow cross-sectional area is less than 3%.

[0040] In this embodiment, the control unit acts as the brain of the system. Figure 2 The control logic shown here implements real-time acquisition of the membrane electrode catalyst layer interface temperature via an embedded thermocouple. Physical contact between the thermocouple's sensing tip and the catalyst layer ensures measurement accuracy of ±0.5°C. A synchronous voltage monitoring circuit captures output voltage fluctuations with 0.1 millivolt resolution. When the system enters a -25°C environment or detects a voltage drop exceeding 10%, the control unit immediately triggers a four-step closed-loop control. First, the main hydrogen supply pressure reducing valve opens to continuously supply hydrogen to the stack while simultaneously applying a pulsed current of 0.4 amperes per square centimeter. The pulse frequency is set to 20 Hz (5 seconds on, 3 seconds off). Heat generated by ion migration resistance causes the interface temperature to rise at a rate of 2°C / s. At this point, the piezoelectric ceramic solenoid valve is forcibly locked until the thermocouple temperature exceeds the -5°C threshold, which is determined by the membrane electrode's brittle-ductile transition point and is derived from freeze-thaw experiments. Once the temperature reaches the threshold, the control unit closes the main valve for 0.1 seconds to establish a pressure differential and then opens the piezoelectric valve for precise purge control.

[0041] Specifically, in this embodiment, the purge duration is not a fixed value, but is dynamically calculated based on the voltage recovery rate η. That is, when the control unit opens the piezoelectric ceramic solenoid valve, it dynamically calculates the purge duration based on the real-time voltage recovery rate η, where η = measured voltage after purge / theoretical voltage value, and t = 0.02 + 0.08 × (1-η) seconds. For example, when the voltage recovers to 90% of the theoretical value, the purge duration is automatically adjusted to 22 milliseconds. 0.3 MPa hydrogen is accelerated through the spiral guide groove to form a vortex of 20 meters per second. The 30-degree inclination design allows the airflow to cover more than 90% of the flow channel cross-section, efficiently discharging semi-molten ice crystals along the inclined surface.

[0042] In addition, in this embodiment, in order to completely solve the problem of secondary freezing of the residual water film after purging, the control unit applies a 0.1A / cm² maintenance current for 60s immediately after the purge is completed to stabilize the interface temperature at above -3°C.

[0043] To address the thin air environment at high altitudes, the system has a built-in air pressure compensation module. When the altitude exceeds 3,000 meters, the purge pressure is increased according to the formula P = 0.3 + 0.001 × (H - 3,000) MPa. For example, at an altitude of 5,000 meters, the purge pressure is automatically increased to 0.32 MPa to compensate for the reduced scouring force caused by the decrease in air density.

[0044] In this embodiment, a piezoelectric ceramic solenoid valve includes a piezoelectric ceramic driver element. When a control voltage is applied, the driver element generates a micro-displacement that directly drives the valve core to open and close. Specifically, when a 40V step voltage is applied by the control unit, the piezoelectric ceramic stack generates a 15-micron axial micro-displacement within 0.3ms. This displacement is transmitted seamlessly to the valve core via a carbide push rod, enabling millisecond-level switching from closed to fully open. This direct-drive energy transfer mechanism completely eliminates the inertial delays inherent in the mechanical transmission chain of coil excitation, core engagement, and spring return in traditional solenoid valves. It also eliminates the risk of sticking caused by grease solidification in low-temperature environments. Crucially, the piezoelectric ceramic maintains a displacement efficiency exceeding 95% at -40°C, while the response time of traditional solenoid valves can be extended by more than three times due to low-temperature magnetic attenuation. It is precisely this stability in extreme environments that enables the system to precisely initiate the purge process within 45ms after detecting ice blockage, four times faster than traditional solutions, ensuring that semi-molten ice crystals are removed before they recrystallize. This speed advantage is deeply coupled with the embedded thermocouple: the platinum-rhodium alloy temperature-sensing tip of the thermocouple is physically embedded in direct contact with the membrane electrode catalyst layer. Its 0.05 mm diameter probe penetrates the gas diffusion layer to reach the reaction interface, compressing the 3-second thermal conduction delay of traditional surface temperature measurement to 0.05 seconds. When the catalyst layer temperature approaches the brittle-ductile transition point of -5°C, the thermocouple can capture subtle fluctuations of 0.3°C within 300ms, providing a precise trigger signal for the instantaneous operation of the piezoelectric valve.

[0045] Obviously, the embodiments described above are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this application.

[0046] It should be understood that when the terms "first," "second," etc. are used in the claims, specification, and drawings of this application, they are only used to distinguish different objects, rather than to describe a specific order. The terms "comprise" and "comprising" used in the specification and claims of this application indicate the presence of the described features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or combinations thereof.

Claims

1. A low-temperature starting system for a hydrogen fuel cell for an unmanned aerial vehicle, wherein the hydrogen fuel cell comprises a membrane electrode, characterized in that include: Hydrogen supply subsystem, purge actuator, stack sensor module and control unit; The hydrogen supply subsystem includes a hydrogen storage bottle, a main hydrogen supply pressure reducing valve and a three-way joint. The output end of the main hydrogen supply pressure reducing valve is divided into a main path connected to the membrane electrode anode inlet and a bypass connected to the purge actuator through the three-way joint; The purge actuator comprises a piezoelectric ceramic solenoid valve connected in series and a swirl nozzle integrated at the inlet of the membrane electrode anode flow channel; The stack sensing module includes a membrane electrode interface temperature sensor and a voltage detection circuit; The control unit is electrically connected to the main hydrogen supply pressure reducing valve, the piezoelectric ceramic solenoid valve, the membrane electrode interface temperature sensor and the voltage detection circuit; The control unit is configured to execute control logic: When the membrane electrode interface temperature sensor detects that the membrane electrode interface temperature is lower than the safety threshold or the voltage detection circuit detects a voltage drop, the main hydrogen supply pressure reducing valve is opened and a pulse current is applied; Before the membrane electrode interface temperature rises to the purge threshold, the piezoelectric ceramic solenoid valve is prohibited from being started. After the purge threshold is reached, the main hydrogen supply pressure reducing valve is closed and the piezoelectric ceramic solenoid valve is opened to purge through the swirl nozzle.

2. The system according to claim 1, wherein: When executing the control logic, the control unit sets the safety threshold to -25°C and the purge threshold to -5°C.

3. The system according to claim 1, wherein: When executing the control logic, the control unit uses a voltage drop greater than 10% as a criterion for detecting the voltage sag.

4. The system according to claim 1, wherein: The outlet end of the swirl nozzle is provided with a 30° inclined surface, and the inner wall of the swirl nozzle is provided with a spiral guide groove.

5. The system according to claim 1, wherein: The piezoelectric ceramic solenoid valve includes a piezoelectric ceramic driving element. When a control voltage is applied to the driving element, a micro displacement is generated to directly push the valve core to open and close.

6. The system according to claim 1, wherein: When the control unit opens the piezoelectric ceramic solenoid valve, it dynamically calculates the purge time t according to the real-time voltage recovery rate η, where η=measured voltage after purge / theoretical voltage value, and t=0.02+0.08×(1-η) seconds.

7. The system according to claim 1, wherein: After the purge is completed, the control unit immediately applies a maintenance current of 0.1A / cm² to the membrane electrode for 60 seconds.

8. The system according to claim 1, wherein: A stainless steel filter with a pore size of 50 microns is built in at the outlet of the swirl nozzle.

9. The system according to claim 1, wherein: The control unit is equipped with a plateau air pressure compensation module. When the altitude is higher than 3000 meters, the purge hydrogen pressure is increased according to the formula P=0.3+0.001×(H-3000)MPa, where H is the altitude value.

10. The system according to claim 1, wherein: The membrane electrode interface temperature sensor is an embedded thermocouple, and its temperature sensing end is in physical contact with the membrane electrode catalyst layer.

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