Documents disponibles écrits par cet auteur

Dynamic simulator for a PEM fuel cell system with a PWM DC/DC converter / Song-Yul Choe in IEEE transactions on energy conversion, Vol. 23 n°2 (Juin 2008) 

Public ISBD [article]  in IEEE transactions on energy conversion > Vol. 23 n°2 (Juin 2008) . - pp. 669 - 680 Titre : Dynamic simulator for a PEM fuel cell system with a PWM DC/DC converter Type de document : texte imprimé Auteurs : Song-Yul Choe, Auteur ; Jong-Woo Ahn, Auteur ; Jung-Gi Lee, Auteur Année de publication : 2008 Article en page(s) : pp. 669 - 680 Note générale : Energy conversion Langues : Anglais (eng) Mots-clés : DC-DC  power  convertors;  PWM  power  convertors;  power  control;  proton  exchange  membrane  fuel  cells Résumé : Polymer electrolyte membrane (PEM) fuel cells typically have low voltage, high current, terminal characteristics that cannot accommodate common electric loads like electric motors or power utility grids. Thus, a dc/dc converter is required to boost the output voltage of these power systems. Furthermore, the terminal characteristics are dependent on loads and operating conditions of the fuel cell system. The continuously changing power demand of an electric load requires dynamically replenishing the air and fuel, by properly maintaining humidity in the cell and efficiently rejecting the heat produced. These factors present important challenges for the design of reliable and durable power systems. We present new dynamic models for a fuel cell system and a pulsewidth modulation dc/dc converter with associated controls and integration. The model for the system consists of three subsystems that include an PEM fuel cell stack, an air supply, and a thermal system. Four different controllers were designed to control the air, the coolant, and the output voltage of the converter, and to optimize the power flow between the fuel cell and the output capacitor. The integrated model with its controls was tested using a real-time simulator that reduced computational time and facilitated the analysis of the interactions between loads and the fuel cell components and also allowed the optimization of a power control strategy. The responses of a static and dynamic load show that the power controls proposed can coordinate two energy sources, resulting in improved dynamics and efficiency. En ligne : http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=4505385&sortType%3Das [...] [article] Dynamic simulator for a PEM fuel cell system with a PWM DC/DC converter [texte imprimé] / Song-Yul Choe, Auteur ; Jong-Woo Ahn, Auteur ; Jung-Gi Lee, Auteur . - 2008 . - pp. 669 - 680. Energy conversion Langues : Anglais (eng) in IEEE transactions on energy conversion > Vol. 23 n°2 (Juin 2008) . - pp. 669 - 680 Mots-clés : DC-DC  power  convertors;  PWM  power  convertors;  power  control;  proton  exchange  membrane  fuel  cells Résumé : Polymer electrolyte membrane (PEM) fuel cells typically have low voltage, high current, terminal characteristics that cannot accommodate common electric loads like electric motors or power utility grids. Thus, a dc/dc converter is required to boost the output voltage of these power systems. Furthermore, the terminal characteristics are dependent on loads and operating conditions of the fuel cell system. The continuously changing power demand of an electric load requires dynamically replenishing the air and fuel, by properly maintaining humidity in the cell and efficiently rejecting the heat produced. These factors present important challenges for the design of reliable and durable power systems. We present new dynamic models for a fuel cell system and a pulsewidth modulation dc/dc converter with associated controls and integration. The model for the system consists of three subsystems that include an PEM fuel cell stack, an air supply, and a thermal system. Four different controllers were designed to control the air, the coolant, and the output voltage of the converter, and to optimize the power flow between the fuel cell and the output capacitor. The integrated model with its controls was tested using a real-time simulator that reduced computational time and facilitated the analysis of the interactions between loads and the fuel cell components and also allowed the optimization of a power control strategy. The responses of a static and dynamic load show that the power controls proposed can coordinate two energy sources, resulting in improved dynamics and efficiency. En ligne : http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=4505385&sortType%3Das [...]

Measurements of high velocity gradient flow using bubble tracers in a cavitation tunnel / Bu-Geun Paik in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 9 (Septembre 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 9 (Septembre 2009) . - 10 p. Titre : Measurements of high velocity gradient flow using bubble tracers in a cavitation tunnel Type de document : texte imprimé Auteurs : Bu-Geun Paik, Auteur ; Kyung-Youl Kim, Auteur ; Jong-Woo Ahn, Auteur Année de publication : 2009 Article en page(s) : 10 p. Note générale : fluids enginering Langues : Anglais (eng) Mots-clés : propeller  wake;  bubble  tracers;  particle  image  velocimetry  technique;  cavitation  tunnel Résumé : The objective of the present study is to investigate propeller wake using particle image velocimetry (PIV) technique with bubble type of tracers, naturally generated by the decrease in the static pressure in a cavitation tunnel. The bubble can be grown from the nuclei melted in the water tunnel and the size of bubbles is changed by varying the tunnel pressure. A series of experiments are conducted in the conditions of the uniform and high velocity gradient flows to find out the characteristics of bubble tracers and compared the measurement results using bubbles with those using solid particles. Bubbles showed good trace ability in the region of 15 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Measurements of high velocity gradient flow using bubble tracers in a cavitation tunnel [texte imprimé] / Bu-Geun Paik, Auteur ; Kyung-Youl Kim, Auteur ; Jong-Woo Ahn, Auteur . - 2009 . - 10 p. fluids enginering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 9 (Septembre 2009) . - 10 p. Mots-clés : propeller  wake;  bubble  tracers;  particle  image  velocimetry  technique;  cavitation  tunnel Résumé : The objective of the present study is to investigate propeller wake using particle image velocimetry (PIV) technique with bubble type of tracers, naturally generated by the decrease in the static pressure in a cavitation tunnel. The bubble can be grown from the nuclei melted in the water tunnel and the size of bubbles is changed by varying the tunnel pressure. A series of experiments are conducted in the conditions of the uniform and high velocity gradient flows to find out the characteristics of bubble tracers and compared the measurement results using bubbles with those using solid particles. Bubbles showed good trace ability in the region of 15 En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]