Methanol energy supply device for unmanned aerial vehicle

Abstract

The invention discloses a methanol energy supply device for an unmanned aerial vehicle and a working method of the methanol energy supply device, and belongs to the technical field of unmanned aerial vehicle energy supply. The device mainly comprises a miniature methanol reformer and a high-temperature proton exchange membrane fuel cell (HT-PEMFC). The micro methanol reformer comprises a methanol storage tank, a vaporizing chamber, a reforming reaction chamber and a heat exchange assembly, the methanol storage tank is made of a high-strength lightweight material, the vaporizing chamber is provided with an efficient heating structure, the reforming reaction chamber is filled with a special catalyst, and the heat exchange assembly adopts an efficient heat transfer technology. A proton exchange membrane, an electrode and a gas diffusion layer of the high-temperature fuel cell are all made of special materials. During working, liquid methanol is vaporized and reformed to generate reformed gas, and hydrogen enters the fuel cell for power generation. Through the compact modular design, the device has the advantages of high energy conversion efficiency, compact and light structure, quick starting performance, strong hydrogen impurity tolerance and the like, can effectively improve the cruising ability and working performance of the unmanned aerial vehicle, and has a good application prospect in the field of unmanned aerial vehicles.

Description

Technical Field

[0001] The present invention relates to the technical field of energy supply for unmanned aerial vehicles (UAVs), and particularly to a device and method for supplying energy to UAVs by using a micro methanol reformer combined with a high-temperature fuel cell. Background Art

[0002] In today's era, the application scenarios of UAVs are becoming increasingly rich and diverse. From precise mapping of complex terrains, to plant protection operations in large areas of farmland, to precise delivery of emergency rescue supplies, UAVs play a crucial and irreplaceable role. However, the endurance ability has become a bottleneck restricting the further development of UAVs. Traditional lithium batteries have a low energy density and cannot meet the requirements of long-time and long-distance flights of UAVs. Although hydrogen fuel cells have significant advantages such as high energy density, cleanliness and environmental friendliness, the storage and transportation of hydrogen face many difficulties and pose many obstacles in practical applications. Methanol reforming for hydrogen production to supply energy to hydrogen fuel cells provides a feasible path to solve the endurance problem of UAVs. However, the existing related systems still have a series of problems such as complex structure, low energy conversion efficiency, slow startup speed, etc., and there is an urgent need for improvement and optimization to promote UAVs to play a greater role in more fields. Summary of the Invention

[0003] The present invention focuses on developing an efficient energy supply device with a micro methanol reformer and a high-temperature fuel cell as the core components and its supporting method. Its core objective is to simplify the system structure through innovative design, thereby significantly improving the energy conversion efficiency, reducing the complexity of the system, providing a solid guarantee for the long-term and stable operation of UAVs, and significantly enhancing the endurance ability of UAVs.

[0004] Micro Methanol Reformer With its compact modular design, the micro methanol reformer efficiently integrates key components in a limited space, significantly enhancing the portability and practicality of the system. Its methanol storage tank is made of high-strength and lightweight materials such as carbon fiber reinforced composite materials. Such materials not only have excellent mechanical strength to withstand a certain pressure to ensure the safety of methanol storage, but also due to their low density characteristics, they greatly reduce the overall weight while ensuring the storage capacity, meeting the strict requirements for equipment lightweight.

[0005] The high-efficiency heating element equipped in the vaporization chamber mostly adopts a thin-film heating structure based on MEMS (Micro-Electro-Mechanical System) technology, which can heat liquid methanol to above its boiling point in an extremely short time to achieve rapid vaporization. This thin-film heating structure has an extremely high thermal response speed and thermal conversion efficiency, ensuring the high efficiency and stability of the methanol vaporization process. The gaseous methanol then enters the reforming reaction chamber, and the special catalyst filled in this reaction chamber is developed based on in-depth research on the synergistic effect of catalytic active sites, carrier structure and metal elements. Active metal elements such as copper and zinc are loaded on a porous alumina or zirconia carrier with a high specific surface area. In the temperature range of 250 - 350 °C, with the strong interaction between the active metal and the carrier and the abundant reaction sites provided by the porous carrier, the activation energy of the methanol reforming reaction is effectively reduced, thus efficiently catalyzing the methanol reforming reaction to generate reformed gas rich in hydrogen and carbon dioxide.

[0006] The heat exchange component adopts microchannel heat exchange technology. By precisely designing the geometric shape and size of the microchannels, efficient heat transfer between the large amount of waste heat generated by the reforming reaction and the methanol to be vaporized is achieved. This microchannel heat exchange structure greatly increases the heat exchange area, significantly improves the energy utilization rate, reduces the energy consumption of the system, and improves the overall performance.

[0007] Liquid methanol flows from the storage tank into the vaporization chamber under the drive of gravity or a micropump. In the vaporization chamber, through the heat provided by the above-mentioned high-efficiency heating element, methanol molecules obtain sufficient energy to overcome the intermolecular forces and change from liquid to gas. The gaseous methanol enters the reforming reaction chamber under the action of a pressure difference. On the surface of the catalyst, methanol molecules are first adsorbed on the active sites, and then a series of complex chemical reactions occur. Taking the steam reforming reaction (the main reaction equation is CH3OH + H2O ⇌ CO2 + 3H2) as an example, the carbon-hydrogen bond, carbon-oxygen bond in methanol molecules and the hydrogen-oxygen bond in water molecules are broken in turn and recombined under the catalysis of the active metal to generate hydrogen and carbon dioxide. During the whole reaction process, the heat generated is transferred to the methanol to be vaporized through the microchannel heat exchange component, realizing the closed-loop recycling of energy and greatly improving the energy utilization efficiency.

[0008] High-temperature fuel cell High-temperature fuel cells use high-temperature proton exchange membrane fuel cells (HT-PEMFCs), whose operating temperature is in the specific range of 120 - 200 °C, endowing the cells with unique performance advantages. The fuel cell stack is composed of multiple single cells connected in series in an orderly manner to form a stable power generation unit. The core component of each single cell - the proton exchange membrane - mostly uses special polymer materials based on phosphorus-doped polybenzimidazole (PBI) and other materials with high temperature resistance and high proton conductivity. In a high-temperature environment, the proton conduction channels in the molecular structure of such materials can remain stable and unobstructed, ensuring the efficient migration of protons. At the same time, they have good chemical stability and can resist chemical corrosion during the reaction process.

[0009] Both the anode and the cathode use catalytically active materials such as nanoscale platinum-based alloys. Through nanoscale structural regulation and alloying design, the number of catalytically active sites is greatly increased, and the catalytic reaction rate is significantly improved. The gas diffusion layer uses materials with a three-dimensional porous structure such as carbon paper or carbon cloth. Such materials not only have good air permeability to ensure that the reaction gases can quickly and evenly diffuse to the catalytic reaction area, but also have excellent electrical conductivity, can effectively conduct electrons, and ensure the smoothness of the internal electron transport path of the battery.

[0010] In terms of the working mechanism, hydrogen in the reformed gas from the micro methanol reformer enters the anode of the fuel cell. On the surface of the nanoscale catalytically active material at the anode, hydrogen molecules dissociate and adsorb under catalysis. Hydrogen atoms lose electrons to become protons, and the electrons move directionally through the external circuit to form an electric current to supply power to external loads such as drones. Protons migrate through the membrane layer to the cathode by virtue of the proton conduction characteristics of the proton exchange membrane. At the cathode, oxygen molecules adsorb at the catalytically active sites and react with the migrated protons and electrons flowing in from the external circuit to generate water. The reaction equation is O 2 +4H + + 4e - ⇌ 2H 2 O. In a high-temperature environment of 120 - 200 °C, the reaction kinetics of the fuel cell is significantly accelerated because high temperature can increase the activity of reaction particles and reduce the reaction activation energy. At the same time, the high-temperature environment makes the fuel cell more tolerant to impurities in hydrogen (such as carbon monoxide, etc.). Carbon monoxide is not easily adsorbed on the catalytically active sites at high temperature, so that the reformed gas can be directly used as fuel without complex deep purification treatment, simplifying the system process and reducing the operating cost and equipment complexity.

[0011] Beneficial effects High energy conversion efficiency: The heat exchange component of the micro methanol reformer recovers waste heat to preheat methanol, reducing external energy input. Combined with the efficient electrochemical reaction of high-temperature fuel cells, the overall energy conversion efficiency of the system is significantly improved, which can be increased by 15 - 20% compared with traditional energy supply systems.

[0012] Compact and lightweight structure: The micro methanol reformer with a compact modular design and the integrated high-temperature fuel cell stack reduce unnecessary connection components and complex pipelines, making the entire energy supply device have a compact structure, small volume, and significantly reduced weight. It is convenient to be installed on drones without affecting their flight performance.

[0013] Fast startup performance: The efficient vaporization and reforming reactions of the micro methanol reformer, as well as the fast reaction characteristics of high-temperature fuel cells at higher temperatures, greatly improve the startup speed of the device, which is shortened from 5 - 10 minutes of traditional systems to 2 - 3 minutes, meeting the rapid response requirements of drones.

[0014] Strong tolerance to hydrogen impurities: The working temperature advantage of high-temperature proton exchange membrane fuel cells enables them to have strong tolerance to impurities in reformed gas. Without a complex gas purification unit, the system structure is simplified, the cost is reduced, and at the same time, the reliability and stability of the system are improved. Brief Description of the Drawings

[0015] Figure 1 It is a schematic flow diagram of the device for supplying energy to drones by the combined micro methanol reformer and high-temperature fuel cell of the present invention; Detailed Embodiments

[0016] Embodiment 1 Device construction: Micro methanol reformer: The methanol storage tank is made of high-strength aluminum alloy with a volume of 3L, and its surface is treated with special anti-corrosion to ensure the safe and durable storage of methanol. The vaporization chamber is heated by electric heating wires wound around it, with a heating power of 500W. The outer layer of the electric heating wires is wrapped with high-efficiency heat insulation materials to reduce heat loss. A spoiler is arranged inside the vaporization chamber to make the methanol vapor enter the reforming reaction chamber more evenly. The reforming reaction chamber is a cylindrical structure, and a self-made copper-zinc-based catalyst is filled inside. The catalyst uses nano-porous alumina as the carrier, and copper and zinc active components are loaded on the surface of the carrier by the impregnation method, with loadings of 15% and 10% respectively. During filling, the method of layered compaction is adopted to ensure uniform distribution and firm fixation of the catalyst. The heat exchange component selects a compact plate heat exchanger, and its heat exchange plates are made of copper alloy with high thermal conductivity. Special corrugated structures are designed on the surface of the plates to increase the heat exchange area and fluid disturbance, and improve the heat exchange efficiency.

[0017] High-temperature fuel cell: A commercial high-temperature proton exchange membrane fuel cell stack with a rated power of 800 W is selected. The single cell size of this fuel cell stack is 5 cm × 5 cm. The proton exchange membrane uses a polybenzimidazole (PBI)-based membrane, which has good proton conduction performance at a working temperature of 160 °C. The catalytic layers of both the anode and cathode use nano-platinum particles as the active material, with a loading of 0.5 mg / cm², and are uniformly coated on the surface of the gas diffusion layer. The gas diffusion layer selects carbon paper material, which is hydrophobic-treated, and the porosity is controlled at 40% - 50% to ensure that gas can diffuse smoothly to the catalytic reaction area while preventing liquid penetration.

[0018] Performance test: Startup test: Connect the assembled device to the control system of the simulated drone platform. When starting the device, use the timer in the control system to record the time from turning on the power to the fuel cell stably outputting voltage. After multiple tests, take the average value, and record the startup time as 3 minutes.

[0019] Power and endurance test: The simulated drone flies at a constant speed of 40 km / h. By adjusting the simulated load resistance, make the output power of the device stable at 600 W. At the same time, use a high-precision power monitor to monitor the output power of the device in real time, and record the time from the full methanol state to the output power of the device dropping to 80% of the rated power as the endurance time. After testing, the endurance time reaches 4 hours.

[0020] Energy conversion efficiency test: When the device is running stably with an output power of 600 W, use a calorimeter to measure the methanol energy consumed during the methanol reforming process, and at the same time monitor the electrical energy output by the device. Calculate the energy conversion efficiency through the formula (output electrical energy / consumed methanol energy) × 100%. After multiple tests, take the average value, and the result shows 40%.

[0021] Example 2 Device improvement: Micro methanol reformer: Optimize the structure of the heat exchange component, increase the number of heat exchange plates, and increase the heat exchange area by 30%. At the same time, adjust the catalyst formula in the reforming reaction chamber, increase the copper loading to 18%, reduce the zinc loading to 8%, and optimize the impregnation process to make the distribution of active components on the carrier surface more uniform. In addition, improve the catalyst loading method, adopt a combination of layer-by-layer loading and particle mixing loading to improve the activity and stability of the catalyst.

[0022] High-temperature fuel cell: Optimize the gas distribution system of the fuel cell stack, adopt a new type of porous shunt plate, so that the reformed gas and air can be more evenly distributed to each single cell, reducing the performance difference inside the fuel cell stack.

[0023] Performance comparison: Startup test: According to the same test method as in Example 1, the recorded startup time was shortened to 2 minutes.

[0024] Power and endurance test: Under the same conditions of the simulated drone flying at a constant speed of 40 km / h, by adjusting the load resistance, the stable output power of the device was increased to 700 W. The endurance test method was the same as in Example 1, and after testing, the endurance time was extended to 5 hours.

[0025] Energy conversion efficiency test: Using the same test and calculation methods as in Example 1, the energy conversion efficiency was increased to 45%.

[0026] It can be seen from the above embodiments that the device and method for supplying energy to a drone by combining a micro methanol reformer and a high-temperature fuel cell according to the present invention can effectively improve the endurance and working performance of the drone in practical applications and have good application prospects.

Claims

1. A methanol energy supply device for unmanned aerial vehicles, characterized in that: It includes a micro methanol reformer and a high temperature fuel cell; the micro methanol reformer includes a methanol storage tank, a vaporization chamber, a reforming reaction chamber and a heat exchange component; the high temperature fuel cell uses a high temperature proton exchange membrane fuel cell (HT-PEMFC).

2. The methanol energy supply device for UAV according to claim 1, characterized in that: The methanol storage tank is made of high-strength, lightweight materials, such as carbon fiber reinforced composite materials or high-strength aluminum alloys, to reduce the overall weight and ensure the safety of methanol storage.

3. The methanol energy supply device for UAV according to claim 1, characterized in that: The vaporization chamber is equipped with a thin film heating structure based on MEMS (micro-electromechanical system) technology or an electric heating wire surround heating method, which can heat liquid methanol to above the boiling point in a short time to achieve rapid vaporization. The outer layer of the electric heating wire is wrapped with high-efficiency thermal insulation material, and a spoiler is arranged in the vaporization chamber to evenly discharge methanol vapor.

4. The methanol energy supply device for UAV according to claim 1, characterized in that: The reforming reaction chamber is filled with a special catalyst loaded with active metal elements such as copper and zinc on a porous alumina or zirconia carrier with a high specific surface area, catalyzing the methanol reforming reaction in the temperature range of 250-350°C to generate reformed gas rich in hydrogen and carbon dioxide, and the catalyst is fixed by layered compaction loading or a combination of layer-by-layer loading and particle mixed loading.

5. The methanol energy supply device for UAV according to claim 1, characterized in that: The heat exchange component adopts microchannel heat exchange technology or compact plate heat exchanger. By precisely designing the microchannel geometry and size or using heat exchange plates with special corrugated structures on the surface, efficient heat transfer between the waste heat of the reforming reaction and the methanol to be vaporized is achieved, thereby improving energy utilization. The heat exchange plates are made of copper alloy with high thermal conductivity.

6. The methanol energy supply device for UAV according to claim 1, characterized in that: The proton exchange membrane of the high-temperature proton exchange membrane fuel cell adopts special polymer materials such as phosphorus-doped polybenzimidazole (PBI) that are resistant to high temperatures and have high proton conductivity; the anode and cathode adopt catalytically active materials such as nano-scale platinum-based alloys; and the gas diffusion layer adopts materials with a three-dimensional porous structure such as carbon paper or carbon cloth.

7. The methanol energy supply device for UAV according to claim 1, characterized in that: The high-temperature proton exchange membrane fuel cell operates at a temperature of 120-200°C, hydrogen is catalytically dissociated at the anode, and protons migrate through the proton exchange membrane to the cathode to react with oxygen to generate water. This temperature range accelerates the reaction kinetics and makes the fuel cell more tolerant to hydrogen impurities.

8. The methanol energy supply device for UAV according to claim 1, characterized in that: The device adopts a compact modular design, so that the micro methanol reformer and the high temperature fuel cell stack have a compact structure, small size, and reduced weight, which is convenient for installation on a drone.

9. A method for operating a methanol energy supply device for a UAV as claimed in any one of claims 1 to 8, characterized in that: The following steps are involved: Liquid Methanol flows from the methanol storage tank into the vaporization chamber under the force of gravity or driven by a micro pump, and is heated by a heating element in the vaporization chamber to vaporize into gaseous methanol; Gaseous methanol enters the reforming reaction chamber and undergoes a reforming reaction under the action of the catalyst to generate reformed gas; The waste heat generated by the reforming reaction is transferred to the methanol to be vaporized through the heat exchange component; The hydrogen in the reformed gas enters the anode of the high-temperature fuel cell, where it dissociates and adsorbs. The electrons pass through the external circuit to form an electric current to power the drone, and the protons migrate to the cathode through the proton exchange membrane to react with oxygen to produce water.

10. The working method according to claim 9, characterized in that: The reforming reaction is mainly steam reforming reaction, the reaction equation is CH3OH + H2O ⇌ CO2 + 3H2, and the cathode reaction equation is O2 + 4H + +4e - ⇌ 2H2O.

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