Fuel Cells
M. Rostami; A. H. Farajollahi; F. Bagherpor; V. Sfandiyar
Abstract
Polymer electrolyte membrane fuel cells (PEMFCs) produce high power density efficiently and in a pollution-free way. Therefore, it is employed in UAVs. Flow fields play key role in the performance of PEMFC-powered UAVs. In this study, a novel flow field named modified combined was introduced and investigated ...
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Polymer electrolyte membrane fuel cells (PEMFCs) produce high power density efficiently and in a pollution-free way. Therefore, it is employed in UAVs. Flow fields play key role in the performance of PEMFC-powered UAVs. In this study, a novel flow field named modified combined was introduced and investigated by a three-dimensional and two-phase PEMFC model. In the flow field main channels are tapered aiming to reinforce the performance. The study consists of two steps. In the first stage, modified combined was compared with parallel, serpentine, interdigitated, and combined. The results showed that in the modified combined compared with simple combined, pressure drop decreased 22.6%. Modified combined demonstrated suitable oxygen distribution and appropriate management and the specific power of modified combined is the highest value among all flow fields. Finally, the effect of atmospheric conditions on the performance of the PEMFC with modified combined flow field was studied and two equations were presented to predict the performance at 0.4V and 0.7V at the different altitudes of flight. The findings unveiled the point that in the cruise phase of the flight, low voltage is more suitable for PEMFC-driven UAV with modified combined flow field. All in all, modified combined flow field and low voltage are recommended to be utilized in PEMFCs as propulsion system of UAVs.
Fuel Cells
M. Rostami; A.H. Farajollahi; M. Marefati; R. Fili; F. Bagherpor
Abstract
The propulsion system of an Unmanned Aerial Vehicle (UAV) plays an essential role in its performance, stability and flight endurance. In this study, two types of propulsion systems for UAV (differentiated based on fuel type) are studied to determine their characteristics and advantages. These proposed ...
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The propulsion system of an Unmanned Aerial Vehicle (UAV) plays an essential role in its performance, stability and flight endurance. In this study, two types of propulsion systems for UAV (differentiated based on fuel type) are studied to determine their characteristics and advantages. These proposed propulsion systems are using a solid oxide fuel cell (SOFC) to generate the heat required for the operation of the turbine and generating thrust. To achieve the best operating condition, a multi-objective Non-Dominated Sorting Genetic Algorithm (NSGA-II) in MATLAB is used to decide key design parameters. For reaching the best conditions where the acceptable thrust is accompanied by reasonable flight duration, the TOPSIS decision-making method was considered. Results indicated that the efficiency and generated power of the propulsion system will increase by higher flight altitude or compressor pressure ratio. Also, due to the recirculation of fuel in the SOFC’s anode, the higher efficiency is observed in comparison when hydrogen is used; since anode-recirculation causes higher fuel utilization. The optimization result shows that the efficiency and fuel consumption for the hydrogen-fueled system is 48.7% and 0.0024g/s, respectively, and 67.9% and 0.0066kg/s for methane-fueled engine. It was also found that, maximum efficiency for both hydrogen- and methane-fueled systems are available with the stack temperature of 1025 K; however maximum thrust for these systems is at the stack temperature of 1075 K. In addition, increasing fuel rate of the SOFC power unit helps the process of generating extra power and thrust for UAVs.