Byungki Ahn

Analysis of Mass Transport in PEMFC GDL

The 3D structure of GDL for fuel cells was measured using high-resolution X-ray tomography in order to study material transport in the GDL. A computational algorithm has been developed to remove noise in the 3D image and construct 3D elements representing carbon fibers of GDL, which were used for both structural and fluid analyses. Changes in the pore structure of GDL under various compression levels were calculated, and the corresponding volume meshes were generated to evaluate the anisotropic permeability of gas within GDL as a function of compression. Furthermore, the transfer of liquid water and reactant gases was simulated by using the volume of fluid (VOF) and pore-network model (PNM) techniques. In addition, the simulation results of liquid water transport in GDL were validated by analogous experiments to visualize the diffusion of fluid in porous media. Through this research, a procedure for simulating the material transport in deformed GDL has been developed; this will help in optimizing the clamping force of fuel cell stacks as well as in determining the design parameters of GDL, such as thickness and porosity.

Development of the Integrated Fuel Cell Monitoring System

>> The interest of New Renewable Energy is increasing globally because of the increment of the uncertainty for the energy’s supply and demand, and the increment of the frequency in weather anomaly and its damages. One of the New Renewable Energies, Hydrogen receives attention as the future energy that can deal with global environment regulation. Fuel Cell Electric Vehicle (FCEV) is an environment-friendly vehicle that uses Hydrogen as fuel. The electric power for FCEV is generated by chemical reaction with Oxygen from the air and Hydrogen. Hyundai Motor Company (HMC) has developed a proprietary fuel cell system since 2005. In 2012, HMC is the first car maker that mass-produces the ix35 FCEV to the worldwide such as North America, Europe, etc. In order to develop and improve the FCEV technology, data acquisition and analysis of the driving vehicle information is essential. Therefore, the monitoring system is developed, which is consist of datalogger, Automatic Vehicle Location (AVL) server and main server. Especially, WCDMA technology is integrated into the system which enables the data analysis without any restriction of time and region. The main function of the system is the analysis of the driving pattern and the component durability, and the safety monitoring. As a result, ix35 FCEV has successfully developed by using the developed monitoring system. The system is going to take an advantage of development in the future FCEV technology.

Design and fabrication of low-pressure piezoresistive MEMS sensor for fuel cell electric vehicles

This research focuses on the design and fabrication of a MEMS-based pressure sensor to measure the internal pressure of a thermal management system for fuel cell electric vehicles. The principle of measurement of the pressure is converting the piezoresistor value on a diaphragm deformed by a pressure difference into an output voltage. The diaphragm should operate normally for pressure sensing even harsh environments such as those in automobiles. However, the pressure sensor outputs abnormal values with an offset voltage due to physical and chemical factors during driving. One of the reasons is the polymer reaction originating from the coolant of the thermal management system between the polymer and sensor diaphragm. In this paper, the reason for abnormal operation is analyzed by measurement with a microscope, computational fluid dynamics, finite element method, and reproducible tests. A solution is suggested and a revised pressure sensor is proposed.

Development of Thermal Management System Heater for Fuel Cell Vehicles

The TMS(Thermal Management System) heater in a fuel cell vehicle has been developed to prevent a decline of fuel cell durability and cold start durability. Main functions of the COD(Cathode Oxygen Depletion) heater are depletion of oxygen in a cathode as heat energy and consumption of electric power for rapid warming up of a fuel cell stack. This paper covers subjects including the design specification of a heater, heater controller for detection of overheat and reliability assessment including coolant pressure cycle test of a heater. To verify the design concept, burst pressure and deformation analysis of plastic housing were carried out. Also, temperature distribution analysis of heater surface and coolant inside of housing were carried out to verify the design concept. By designing the plastic housing instead of a steel housing, the 30% weight lightening and 50% cost reduction were attained. A module-based design of a TMS system including a heater or reducing the watt density of a heater is a problem to be solved in the near future work.

Development of Hyundai-Kia’s fuel cell stack

Hyundai-Kia has been developing Fuel Cell (FC) systems as a clean power source for next generation vehicles. Fuel cells are electrochemical devices that convert chemical energy of hydrogen directly into electrical energy that promises efficient power generation with no harmful emissions. During the past several years, Hyundai-Kia has introduced a number of fuel cell-powered Sport Utility Vehicles (SUVs) such as Santa Fe, Tucson, Sportage, Borrego as well as fuel cell buses.