Jaeyoung Han

A Dynamic Model of PEMFC System for the Simulation of Residential Power Generation

A proton exchange membrane fuel cell (PEMFC) system of residential power generator (RPG) has a different operating strategy from the PEMFC system of transportation application because of its environmental difference. In this study, a dynamic simulation model of the PEMFC system is introduced, which has a model for a turbo blower, a membrane humidifier, two cooling circuits, and a PEMFC stack. The thermal efficiency of the PEMFC system for the RPG is very high because it supplies the electricity and hot water to the house. This study is designed to study the dynamic response of individual components during the dynamic change of current density. In particular, since the operation of the turbo blower is very sensitive at low current density the parasitic power consumption of the blower is significant. Additionally, the system performance and the operating strategy are also presented.

Flow Uniformity of Catalytic Burner for Off-Gas Combustion of Molten Carbonate Fuel Cell

A catalytic combustor is a device to burn out the fuel by surface combustion that is used for the combustion of anode off-gas of molten carbonate fuel cell. By employing the catalytic combustor, the purified exhaust gas is able to be recirculated into the cathode channel for CO2 supply to improve thermal efficiency. The design of catalytic combustor depends on many parameters but the flow uniformity is particularly important during the emergency shut-down of fuel cell stack. Right before the temperature control of catalytic combustor is not yet activated, the catalytic combustor should burn out more than two times of rated amount of fuel flow rate. At the over-loaded condition, assurance of flow uniformity at the inlet of catalytic combustor can reduce the damage of catalytic burner caused by local hot zone. In this study, the flow uniformity of the catalytic combustor is investigated in two steps such as preliminary step with model combustor and main analysis step with practical 250 kW catalytic combustor. The 0.5 kW and 5 kW class combustors are applied for preliminary step. In preliminary step, the model combustor is used to determine supporting matters for the flow uniformity. Inlet direction of mixing chamber below the catalytic combustor is also examined in the preliminary step. In the main analysis step, flow uniformity of scale-up combustor has been examined with selected supporting matter and inlet direction into mixing chamber. Geometric and operating parameters are investigated. In particular, the flow rate at off-design operating condition has been examined.Copyright

Dynamic Model of Centrifugal Compressor for Prediction of Surge Evolution and Performance Variations

Abstract : When a control algorithm is developed to protect automotive compressor surges, the simulation model typically selects an empirically determined look-up table. However, it is difficult for a control oriented empirical model to show surge characteristics of the super charger. In this study, a dynamic supercharger model is developed to predict the performance of a centrifugal compressor under dynamic load follow-up. The model is developed using Simulink® environment, and is composed of a compressor, throttle body, valves, and chamber. Greitzers compressor model is used, and the geometric parameters are achieved by the actual supercharger. The simulation model is validated with experimental data. It is shown that compressor surge is effectively predicted by this dynamic compressor model under various operating conditions. †Corresponding Author, sangseok@cnu.ac.krⒸ 2016 The Korean Society of Mechanical Engineers - 기호설명 -  : 면적  : 음속  : 압력  : 부피  : 로터 스피드  : 질량 유량  : 덕트 길이

Development of a Battery Model for Electric Vehicle Virtual Platform

In this paper, a battery model for electric vehicle virtual platform was developed. A battery model consisted of a battery cell model and battery thermal management system. A battery cell model was developed based on Randles equivalent circuit model. Circuit parameters in the form of 3D map data was obtained by charge-discharge experiment of Li-Polymer battery in various temperature condition. The developed battery cell model was experimentally verified by comparing voltages. Thermal management system model was also developed using heat generator, heat transfer and convection model, and cooling fan. For verification of the developed battery model in vehicle level, the integrated battery model was applied in to EV(electric vehicle) virtual platform, and virtual driving simulation using UDDS velocity profile was conducted. The accuracy of the developed battery model has been verified by comparing the simulation results from EV platform with the experimental data.

One-Dimension Thermal Modeling of NiMH Battery for Thermal Management of Electric Vehicles

Fuel consumption rates of electric vehicles strongly depend on their battery performance. Because the battery performance is sensitive to the operating temperature, temperature management of the battery ensures its performance and durability. In particular, the temperature distribution among modules in the battery pack affects the cooling characteristics. This study focuses on the thermal modeling of a battery pack to observe the temperature distribution among the modules. The battery model is a prismatic model of 10 NiMH battery modules. The thermal model of the battery consists of heat generation, convective heat transfer through the channel and conduction heat transfer among modules. The heat generation is calculated by the electric resistance heat during the charge/discharge state. The model is used to determine a strategy for proper thermal management in Electric vehicles.

Model Based Hardware In the Loop Simulation of Thermal Management System for Performance Analysis of Proton Exchange Membrane Fuel Cell

2 School of Mechanical Engineering, Chungnam National Univ. 79, Daehangno, Yuseong-gu, Daejeon, 30-764, Korea Abstract >> A thermal management system of a proton exchange membrane fuel cell is taken charge of controlling the temperature of fuel cell stack by rejection of electrochemically reacted heat. Two major components of thermal management system are heat exchanger and pump which determines required amount of heat. Since the performance and durability of PEMFC system is sensitive to the operating temperature and temperature distribution inside the stack, it is necessary to control the thermal management system properly under guidance of operating strategy. The control study of the thermal management system is able to be boosted up with hardware in the loop simulation which directly connects the plant simulation with real hardware components. In this study, the plant simulation of fuel cell stack has been developed and the simulation model is connected with virtual data acquisition system. And HIL simulator has been developed to control the coolant supply system for the study of PEMFC thermal management system. The virtual data acquisition system and the HIL simulator are developed under LabVIEW TM

Development of Segmented Dynamic Combustion Model to Investigate Instability of Gas Turbine

This paper presents a dynamic combustion model with 10 segmented well-stirred reactors which thermo-acoustic instability of gas turbine is able to be evolved. Because combustion instability in gas turbine results in serious damage to the combustor system, it is inevitable to understand the physics of instability. In this study, segmented dynamic combustion model and thermo-acoustic instability model has been developed in Matlab/Simulink® platform. The dynamic segmented model is developed to understand the consumption of fuel and oxidizer and the volume segmentation is discretized by finite difference method. The thermo-acoustic instability model is based on the wave equation to describe the pressure fluctuation. Model is validated with reference experiment which shows that frequency of pressure appears 430Hz, 630Hz under the low-speed and high-speed range respectively. Also fluctuations of speed and temperature corresponding to the two input condition in the chamber were presented. As a result, reliable combustor simulation model has been developed to analyze combustion characteristics under the operating condition.

Model Reference Adaptive Control of the Air Flow Rate of Centrifugal Compressor Using State Space Method

In this study, a model reference adaptive controller is developed to regulate the outlet air flow rate of centrifugal compressor for automotive supercharger. The centrifugal compressor is developed using the analytical based method to predict the transient behavior of operating and the designed model is validated with experimental data to confirm the system accuracy. The model reference adaptive control structure consists of a compressor model and a MRAC(model reference adaptive control) mechanism. The feedback control do not robust with variation of system parameter but the applied adaptive control is robust even if the system parameter is changed. As a result, the MRAC was regulated to reference air flow rate. Also MRAC was found to be more robust control compared with the feedback control even if the system parameter is changed. † Corresponding Author, sangseok@cnu.ac.kr C 2016 The Korean Society of Mechanical Engineers 한재영 · 정문청 · 유상석 · 이 선 536

Operating Characteristics of MCFC System on the Diversification of Fuel

Abstract >> The fuel cells have been investigated in the applications of marine as the high efficient and eco-friendlypower generating systems. In this study, modeling of IR Type molten carbonate fuel cell (Internal Reforming Typemolten carbonate fuel cell) has been developed to analyze the feasibility of thermal energy utilization. The modelis developed under Aspen plus and used for the study of system performances over regarding fuel types. The simulationresults show that the efficiency of MCFC system based on NG fuel is the highest. Also, it is also verified that the steam reforming is suitable as pre-reforming for diesel fuel. Key words : Molten carbonate fuel cell(용융탄산염연료전지), Steam reformer(수증기 개질), Autothermal reforming(자열 개질), Pre-reformer(예비 개질기) † Corresponding author : sangseok@cnu.ac.kr Received: 2015.03.23 in revised form: 2015.04.16 Accepted: 2015.04.30Copyright ⓒ 2015 KHNES 1. 서 론 최근 환경에 대한 문제가 전 세계적으로 대두되면서, 신재생 에너지 개발이 주목 받고 있다 . 그 중 연료전지는 신 에너지원으로, 특히 고온형 연료전지인 고체산화물 연료전지, 용융탄산염 연료전지는 높은 열효율, 높은 환경친화성 등의 장점을 가지고 있다 .

Experimental Study of Compressor Surge for 250-hp Class Vehicular Turbocharger

* Dept. of Mechanical Engineering, Chungnam Nat’l Univ., ** Seah Engineering.,*** Dept. of Automotive Engineering, Dongmyeong Univ., (Received July 29, 2014 ; Revised September 5, 2014 ; Accepted September 18, 2014)Key Words: Turbocharger(터보차저), Surge Phenomenon(서지현상), Turbo Compressor(터보 압축기), Inlet Guide Vane(입구 안내깃), Anti-Surge Valve(서지 방지 밸브) 초록: 터보압축기의 서지는 압축기의 불안정 운전영역으로 주로 소음과 맥동을 유발하며 수회 지속될 시 압축기 시스템 전반에 걸쳐 막대한 피해를 입힌다. 압축기의 안전한 운전을 위해서는 서지현상에 대한 특성파악과 제어전략 수립이 중요하다. 서지현상의 제어는 주로 압축가스의 통과유동량 증대, 필요한 헤드 저감, 압축기 회전수 감속, 가스의 바이패스를 통하여 이루어진다. 본 연구에서는 차량용 터보차저에 서지를 유발했을 때 각 운전 구간별 발생되는 압력변동 특성을 연구하고자 한다. 서지 특성 확인을 위한 파라미터는 압축기 입구 유량과 출구 유량, 관경, 회전수 등으로 선정하였다. 입구단과 출구단 유량을 조절하여 서지 압력 변동을 조사한 결과, 출구단 보다는 입구단 유량의 급격한 변화가 서지와 압축기 내구에 더 영향이 크다는 것을 확인하였다. Abstract: A surge phenomenon cause noise and pulsations in a turbo compressor, which is an unstable operating regime. Because surge protection ensures a safe compressor operation, it is important to understand the physics of the surge phenomenon. In this study, the surge characteristics of a 250-hp class turbo-compressor were evaluated experimentally. The experimental parameters were the rotational speed, opening angles of the inlet guide vane and exit valve, and inlet pipe diameter and flow rates of the inlet gases. The results showed that the compressor surge was very sensitive to the gas flow rates, exit pressure, rotational speed, and bypass flow rates.