• Title/Summary/Keyword: Low-Pressure Operating

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Effects of Key Operating Parameters on the Efficiency of Two Types of PEM Fuel Cell Systems (High-Pressure and Low-Pressure Operating) for Automotive Applications

  • Kim Han-Sang;Lee Dong-Hun;Min Kyoungdoug;Kim Minsoo
    • Journal of Mechanical Science and Technology
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    • v.19 no.4
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    • pp.1018-1026
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    • 2005
  • The proton exchange membrane (PEM) fuel cell system consisting of stack and balance of plant (BOP) was modeled in a MATLAB/Simulink environment. High-pressure operating (compressor type) and low-pressure operating (air blower type) fuel cell systems were con­sidered. The effects of two main operating parameters (humidity and the pressure of the supplied gas) on the power distribution characteristics of BOP and the net system efficiency of the two systems mentioned above were compared and discussed. The simulation determines an optimum condition regarding parameters such as the cathode air pressure and the relative humidity for maximum net system efficiency for the operating fuel cell systems. This study contributes to get a basic insight into the fuel cell stack and BOP component sizing. Further research using muli­object variable optimization packages and the approach developed by this study can effectively contribute to an operating strategy for the practical use of fuel cell systems for vehicles.

A Study on the Analysis of the Performance and Efficiency of a Low-pressure Operating PEMFC System for Vehicle Applications Using MATLAB/Simulink (MATLAB/Simulink를 이용한 자동차용 상압형 PEM 연료전지 시스템의 성능 및 효율 분석 연구)

  • Park, Raehyeok;Kim, Han-Sang
    • Transactions of the Korean hydrogen and new energy society
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    • v.24 no.5
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    • pp.393-400
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    • 2013
  • The air supply system has a significant effect on the efficiency of polymer electrolyte membrane fuel cell (PEMFC) systems. The performance and efficiency of automotive PEMFC systems are greatly influenced by their air supply system configurations. This study deals with the system simulation of automotive PEMFC systems using MATLAB/Simulink framework. In this study, a low-pressure operating PEMFC system adopting blower sub-module (turbo-blower) is modeled to investigate the effects of stack operating temperature and air stoichiometry on the parasitic power and efficiency of automotive PEMFC systems. In addition, the PEMFC net system efficiency and parasitic power of air supply system are mainly compared for the two types (low-pressure operating and high-pressure operating) of automotive PEMFC systems under the same net power conditions. It is suggested that the obtained results from this system approach can be applied for establishing the novel operating strategies for FC vehicles.

Performance Analysis on the Variable Speed Scroll Compressor with Operating Conditions (가변속 스크롤 압축기의 운전조건의 변화에 따른 성능 해석)

  • 박홍희;박윤철;김용찬
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.12 no.7
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    • pp.649-658
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    • 2000
  • Thermodynamic modeling of low-pressure scroll compressor was developed by combining continuity and energy conservation equation. Suction gas heating was considered using energy balance inside the low pressure shell. Pressure, temperature and mass of refrigerant-22 as a function of orbiting angle were calculated by solving the governing equations using fourth order Rung-Kutta scheme. Motor efficiency was taken by experiments with a variation of frequency. The developed model was applied to the analysis of an inverter driven scroll compressor with a variation of frequency, pressure ratio and operating conditions. The model was verified with the experimental results at the same operating conditions. The developed model was adequate to predict performance of the inverter driven scroll compressor as a function of operating conditions. Calculated parameters from the model were discharge temperature, mass flow rate, power input, COP, and thermodynamic properties with respect to orbiting angle. To enhance the performance of a scroll compressor, it is essential to diminish leakage at low frequency level and improve the mechanical efficiency at high frequency level.

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Expansion of Operating Range and Reduction of Engine out Emission in Low Temperature Diesel Combustion with Boosting (과급을 이용한 저온 디젤 연소의 운전영역 확장 및 배기 배출물 저감)

  • Shim, Eui-Joon;Han, Sang-Wook;Jang, Jin-Young;Park, Jung-Seo;Bae, Choong-Sik
    • Transactions of the Korean Society of Automotive Engineers
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    • v.17 no.5
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    • pp.31-38
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    • 2009
  • Supercharging system was adopted to investigate the influence of boost pressure on operating range and exhaust emissions by using a supercharger at low temperature diesel combustion (LTC) condition in a 5-cylinder 2.7 L direct injection diesel engine. The experimental parameters such as injection quantity, injection timing, injection pressure and exhaust gas recirculation (EGR) rate were varied to find maximum operating range in LTC condition. As a result of adopting increased boost pressure in LTC, wider operating range was achieved compared with naturally aspirated condition due to increased mixing intensity. Increased boost pressure resulted in lower hydrocarbon (HC) and carbon monoxide (CO) emissions due to increased swirl rate and mixing intensity, which induced complete combustion. Moreover, increased boost pressure in LTC resulted in much lower soot emissions compared with high speed direct injection (HSDI) condition.

Aging Characteristics of Low Pressure LPG Regulators for Domestic Use (가정용 LPG 저압조정기의 경년특성에 관한 연구)

  • Kim Young-Gyu;Kwon Jeong-Rock
    • Journal of the Korean Institute of Gas
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    • v.3 no.1
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    • pp.58-63
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    • 1999
  • Experimental works were carried out to evaluate how the lapse of time affects the performance characteristics and the service life of low pressure LPG regulators for domestic use. Experimental results showed that the operating pressure of safety devices deviated from the opening pressure value and the closing pressure value from just 1 year after service, and the operating pressure of regulators used for 7${\~}$8 years notably deviated from the reference value of the adjusting pressure and the closing pressure. And the material properties of springs and diaphragms deteriorated after 5${\~}$6 years of service. Thus, it is estimated that low pressure LPG regulators have approximately 6 years of service life. However, it is highly recommended that regulators exceeding 5 years of service should be replaced for the safety of consumer and accident prevention even if they are operating normally.

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Study on Spray Atomization Characteristics Depending on the Operating Parameters of Urea Injector (요소수 인젝터의 작동 변수에 따른 분무미립화 성능에 관한 연구)

  • Kim, Donghwan;Park, Junkyu;Park, Sungwook
    • Journal of ILASS-Korea
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    • v.24 no.1
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    • pp.1-7
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    • 2019
  • This study was carried out to analyze the spray characteristics as a function of the operating parameters of urea injector used in Urea-SCR system of passenger diesel vehicle. Spray visualization and PDPA experiment were performed to analyze the macroscopic spray development and atomization performance of urea-water-solution. For the urea injector, the deformation of the spray head does not appear to be significant because it operates at a low pressure conditions, and the liquid core and primary droplet are observed throughout the operating conditions. No increase in atomization is seen when the operating pressure is increased, and the spray develops linearly due to poor atomization characteristics. The macroscopic spray behavior of the low-pressure urea injector is predictable through the modification of the Hiroyasu equation.

Theoretical Prediction of AC Characteristics of Low Pressure Lamps (저압 방전등 교류 접등 특성의 이론적 예측)

  • 지철근;장우진;여인선;이진우
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.38 no.6
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    • pp.470-476
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    • 1989
  • In order to develop a mathematical model which can predict the operating voltage and current of a discharge lamp, the properties and the physical phenomena of a low pressure gas discharge are investigated. Fluorescent lamp which uses a low pressure mercury-argon gas discharge is used in the model development. In a low pressure mercur-argon gas discharge, the continuity equation for each excited atom and electron, and the electron energy balance equation can predict the physical quantities of discharge. By coupling these equations and the circuit equation, the electrical characteristics of the discharge lamp can be predicted. To verify the validity of the suggested model, we calculated the voltage and current of a fluorescent lamp operating with inductor ballast for source frequency of 5KHz, 8KHz, 10KHz, and 13KHz. The results show good agreements in wave forms between the measured voltage and current, and the difference between the measured and calculated one is less than 5%.

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Operating Characteristics of Internal Heat Exchanger for $CO_2$ Geothermal Heat Pump in the Heating Mode (난방모드 시 $CO_2$ 지열히트펌프의 내부열교환기에 대한 운전특성)

  • Kim, Jae-Duck;Lee, Sang-Jae;Kim, Seon-Chang;Kim, Young-Lyoul
    • Proceedings of the SAREK Conference
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    • 2009.06a
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    • pp.1226-1231
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    • 2009
  • This paper presents operating characteristics of internal heat exchanger(IHX) for $CO_2$ geothermal heat pump in the heating mode. Mass flow rate of $CO_2$, inlet temperatures of $CO_2$ at high and low pressure side were selected as main effect factors by using fractional factorial DOE(Design of Experiments). And RSM(Response Surface Method) was used in optimization phase. The results show that heat transfer rate of IHX increases when either inlet temperature of low pressure side decreases or inlet temperature of high pressure side increases. Effectiveness of IHX increases with increasing of inlet temperature of either high pressure side or low pressure side. Finally, performance contour map was provided over the operation ranges of the main design factors.

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An Investigation on Operating Characteristics of the Closed Cycle System Using High Pressure Diesel Engine (고압 디젤엔진을 이용한 폐회로 시스템의 운전특성에 관한 고찰)

  • 김인교;박신배
    • Transactions of the Korean Society of Automotive Engineers
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    • v.10 no.5
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    • pp.65-72
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    • 2002
  • The closed cycle diesel system is operated in closed circuit system where there is non air breathing with working fluid consists of combination of oxygen, argon and recycled exhaust gas far obtaining underwater or underground power sources. Experimental apparatus using the MTU8V183SE92 high pressurized engine adapted for closed cycle running, capable of operating at the system pressure of maximum 5 bar is constructed with ACAP as data acquisition system in order to operate equally in the open cycle in surface or the closed cycle in submerged conditions. The general features and the characteristics of combustion of HP(high pressure) diesel engine, specially designed and manufactured only for CCDE, are investigated. The test results of performance of HP diesel engine in closed cycle system are presented with respect to power and boost pressure and compared with those of low pressure diesel engine. The oxygen concentration and specific heat ratio are investigated with its deviation

Expansion of Operating Range and Reduction of BSFC in Low Temperature Diesel Combustion with Boosting (과급을 이용한 저온 디젤 연소의 운전영역 확장 및 연료소비율 저감)

  • Shim, Eui-Joon;Han, Sang-Wook;Jang, Jin-Young;Park, Jung-Seo;Bae, Choong-Sik
    • Proceedings of the KSME Conference
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    • 2008.11b
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    • pp.3013-3018
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    • 2008
  • Supercharging system was adopted to investigate the influence of boost pressure on operating range, brake specific fuel consumption (BSFC) and exhaust emissions by using a supercharger at low temperature diesel combustion (LTC) condition in a 5-cylinder 2.7 L direct injection diesel engine. The experimental parameters such as injection quantity, injection timing, injection pressure and exhaust gas recirculation (EGR) rate were varied to find maximum operating range. The result showed that operating range with boost was expanded up to 41.9% compared to naturally aspirated LTC condition due to increased mixing intensity. The boosted LTC engine showed low BSFC value and dramatically reduced soot emission under all operating range compared with high speed direct injection (HSDI) mode. Finally, this paper presents the boosted LTC map of emission and the strategy of improved engine operating range.

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