Browsing by Author "Aryal, Utsav Raj"
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Item 3D Computational Model for an Electrochemical Gas Separation and Inerting System(Journal of The Electrochemical Society, 2022-04-25) Aryal, Utsav Raj; Aziz, Majid; Prasad, Ajay K.Aircraft fuel tank inerting is employed to reduce the flammability of the fuel vapor in the ullage (air volume above the fuel) by restricting its oxygen concentration to a safe value—12% for commercial aircraft and 9% for military aircraft. Inerting is typically accomplished by displacing oxygen in the ullage with an inert gas like nitrogen. Electrochemical gas separation and inerting system (EGSIS) is an on-board method to generate and supply nitrogen-enriched air (NEA) to the fuel tank. EGSIS combines a polymer electrolyte membrane (PEM) electrolyzer anode which dissociates water to evolve oxygen, and a PEM fuel cell cathode which reduces oxygen from atmospheric air to produce NEA at its outlet. This paper represents the first attempt to model and simulate EGSIS using a three-dimensional, steady state, isothermal model. Various EGSIS performance indicators such as current density, reactant concentration distribution, and polarization curves are studied as a function of operating conditions and design parameters. The results from the computational model are validated against our previous experimental results for various operating conditions. The simulation results reveal the effects of temperature, reactant flowrates, and material property optimization on EGSIS performance. Different operating strategies are explored with the goal of improving system performance.Item Electrochemical gas separation and inerting system(Journal of Power Sources, 2021-05-15) Aryal, Utsav Raj; Chouhan, Ashish; Darling, Robert; Yang, Zhiwei; Perry, Mike L.; Prasad, Ajay K.Following the TWA 800 flight disaster in 1996 which was attributed to an explosion in the fuel tank, inerting of the ullage (air volume above the fuel in the tank) has gained prominence. Fuel tank inerting is the process of reducing the flammability of the ullage by supplying it with an inert gas like nitrogen. Current inerting techniques are expensive, consume large amounts of energy, and fail prematurely. Here, we propose a novel in-flight electrochemical gas separation and inerting system (EGSIS) to produce and supply nitrogen-enriched air (NEA). EGSIS combines a polymer electrolyte membrane (PEM) fuel cell cathode with a PEM electrolyzer anode to generate humidified NEA as the cathode output which can be dehumidified and supplied directly to the fuel tank. The required rate of NEA varies during a typical flight and a major advantage of EGSIS is that the rate of NEA generation can be conveniently controlled by varying the voltage applied to the system. Here, we report on the performance of a single-cell EGSIS apparatus and evaluate its suitability for aircraft fuel tank inerting.Item Electrochemical gas separation and inerting system: performance evaluation, optimization, simulation, and technoeconomic analysis for aircraft(University of Delaware, 2022) Aryal, Utsav RajFollowing the TWA 800 flight disaster in 1996 which was attributed to an explosion in the fuel tank, inerting of the ullage (air volume above the fuel in the tank) has gained prominence. Inerting in most cases is accomplished by displacing oxygen in the tank with an inert gas like nitrogen. Current inerting techniques include the liquid nitrogen system, explosion suppressant foam system, halon extinguishment system, and on-board inert gas generation system (OBIGGS). The commercial airline industry has settled on OBIGGS as a superior alternative to other techniques wherein nitrogen enriched air (NEA) is generated by passing atmospheric air through air separation modules (ASM) at high pressure. Generally, the working principles in ASMs are pressure swing absorption or selective permeation through hollow fiber membranes. The resulting NEA is passed to the fuel tank which drives the oxygen out of the ullage. However, these ASMs are expensive, consume large amounts of energy, and fail prematurely. Another difficulty with such systems is that they provide a fixed nitrogen generation rate, whereas the inerting requirement in aircraft varies with the phase of the flight. ☐ Here, we propose a novel in-flight electrochemical gas separation and inerting system (EGSIS) to produce and supply NEA. EGSIS is an externally powered electrochemical device that combines a polymer electrolyte membrane (PEM) fuel cell cathode with a PEM electrolyzer anode to generate NEA as the cathode output which can be supplied to the fuel tank. A major advantage of EGSIS is that the rate of NEA generation can be conveniently controlled by varying the voltage applied to the system. ☐ EGSIS is first demonstrated by conducting a detailed experimental study using a single-cell apparatus. Results include the effect of temperature and reactant flow rate on EGSIS performance, as well as an analysis of EGSIS efficiency. Next, we conduct an optimization study of EGSIS to improve its performance and enhance water management. Various stack configurations based on electrical connectivity and gas flow are also analyzed. We then present a 3D, steady-state, isothermal model of EGSIS implemented in COMSOL. EGSIS performance parameters such as current density, reactant concentration distribution, and polarization curves are investigated as a function of operating voltage and temperature. Finally, a technoeconomic analysis of this novel technology is presented to evaluate the commercial feasibility of EGSIS in aircraft.Item Optimization of an Electrochemical Gas Separation and Inerting System(Journal of The Electrochemical Society, 2022-06-17) Prasad, Ajay K.; Aryal, Utsav RajAircraft fuel tank inerting is typically accomplished by supplying nitrogen enriched air (NEA) into the ullage (volume of air above the fuel level in the tank). We have developed a novel on-board electrochemical gas separation and inerting system (EGSIS) to generate NEA for fuel tank inerting. EGSIS is an electrically powered system that functionally combines a proton exchange membrane (PEM) fuel cell cathode with an electrolyzer anode. Water management is important in such a PEM-based system because proton transfer requires proper hydration of the membrane. Extremes of both dryout and flooding conditions should be avoided for optimal EGSIS performance. Previous single-cell EGSIS experiments revealed that supplying liquid water at the anode will maintain sufficient membrane hydration even when the system is operated under dry cathode conditions. However, it was difficult to avoid flooding at low cathode air stoichiometries when parallel flow field channels were employed. Here, we implement various strategies to optimize EGSIS performance such as using serpentine and interdigitated flow field channels, as well as a double-layer gas diffusion layer with graded hydrophobicity to mitigate flooding and improve water management. We also present a theoretical analysis of various stack configurations for a practical EGSIS module.