Numerical research and optimization of titanium metal bipolar plate air-cooled fuel cell
Introduction
The bipolar plate is a crucial core component in the proton exchange membrane fuel stack. It plays a key role in gas distribution, conducting current and supporging MEA. It accounts for 60-80% of the stack mass and 20-30% of the cost. Its performance directly affects the efficiency and life of the fuel cell^[1]. Traditional graphite bipolar plates are gradually replaced by metal bipolar plates due to graphite ‘s low mechanical strength and low volume power density. Titanium metal bipolar plate has become a key path to promote the development of PEMFC lightweight and high power density due to its advantages of long service life, low coating cost and good seismic performance.
In recent years, the Unmanned Aerial Vehicle (UAV) market has developed rapidly, and it is expected  that the global UAV market will reach more than 30 billion dollars in 2024. The hydrogen fuel cell has a significant advantage in energy density. Compared with the traditional lithium electric drone, its energy density can reach 2-5 times that of the latter. Under the same take-off weight, the hydrogen-powered drone can extend the flight time to several hours, which means that under the same sub-amount of energy carrier, the hydrogen fuel cell can provide more lasting power for the drone^[1,2].
Under the same take-off weight, the hydrogen powered UAV can extend the flight time to several hours, which greatly expands the operation range and application scenarios of the UAV. The oil pipeline inspection, photovoltaic inspection, lifting, glass curtain wall cleaning, agricultural spraying, lifting equipment, cross-island distribution, material emergency transportation and other scenarios all have high requirements for long endurance and heavy load^[3,4].
 Therefore, the research and development of titanium bipolar plate air-cooled proton exchange membrane fuel cell is expected to realize the organic combination of UAV lightweight and long endurance, and promote the actual landing of hydrogen fuel cell UAV technology in a wide range of application scenarios.

Method
In this study, a three-dimensional two-phase non-isothermal model for the air-cooled fuel cells was established, and the detailed governing equations and source terms and boundary conditions wll be presented in the full paper. The flow channel structure of  the titanium bipolar plate is optimized, and a typical fuel cell unit is simulated (Fig. 1). By the constructed comprehensive and accurate multi-field coupling performance prediction model of fuel cell, the multiphsics processes related to gas-water-heat-electricity at different operation conditions were succcesfully simulated, with the error between the predicted and measured polarization curves being less than 6%. At the same time, an air-cooled fuel cell stack is developed, in order to provide test data for further study related to UAV.

air-cooled fuel cell,titanium metal