• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.7
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• pp.736-745
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• 2009

Fuel cells convert a fuel together with oxygen in a highly efficient electrochemical reaction to electricity and water. Since the electrochemical reaction in the fuel cell stack dose not generate any noise, Fuel cell systems are expected to operated much quieter than combustion engines. However, the tonal noise and the broad band noise caused by a centrifugal compressor and an electric motor cause which is required to feed the ambient air to the cathode of the fuel cell stack with high pressure. In this study, the multi-camber perforated muffler is used to reduce noise. We propose optimized muffler model using an axiomatic design method that optimizes the parameters of perforated muffler while keeping the volume of muffler minimized.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.258-263
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• 2000

River water is higher in temperature than the surrounding environment during the winter. It is highly suitable a heat source for heat pump system. Despite its suitability, however, it is not widely used, due to its fouling and corrosive nature in heat exchanger tubes of evaporator. It is designed prior-treatment system which come into direct contact with the river water, such as auto-seamer, ozone generator for bactericidal test and auto-cleaning system. And it is analyzed treatment effects for its operation. It is designed two-stage compression heat pump system using R-134a with heating load 35.16kW, ad analyzed its performance. As a result it is obtained 3.08 COP when mid-point pressure is 1,200kPa, and bypass ratio of flowing refreigerant to high-stage compressor is 25.1%

• Journal of Power System Engineering
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• v.11 no.4
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• pp.50-55
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• 2007

Nowadays, demands on super low temperature condition for industrial and commercial uses are thriving. Considering of its wide application in the present and the future, study of the super-low temperature refrigeration system should be actively carried out. This study is aimed to investigate refrigeration capacity and coefficient of performance(COP) of the cascade refrigeration system, as well as to get the system which can reach evaporator temperature of $-70^{\circ}C$. For this purpose, R290 and R170 are charged in high stage and low stage respectively. Finally the characteristics of system using R290 and R170 will be proposed. Additionally, In this experiment, the flow rate of air flowing through the LS evaporator and the compressor inlet pressure were varied to investigate the refrigeration capacity and coefficient of performance characteristics.

• Tribology and Lubricants
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• v.18 no.1
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• pp.24-33
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• 2002

The basic equations are derived for the analysis of a staggered labyrinth gas seal which are generally used in high performance compressors and steam turbines. The Bulk-flow is assumed for a single cavity control volume and the flow is assumed to be completely turbulent in circumferential direction. Moody's wall-friction-factor formula is used for the calculation of wall shear stresses in the single cavity control volume. For the reaction force developed by the seal, linearized zeroth-order and first-order perturbation equations are developed for small motion about a centered position. Integration of the resultant first-order pressure distribution along and around the seal defines the rotordynamic coefficients of the staggered labyrinth gas seal. Theoretical results of leakage and rotordynamic characteristics for the staggered labyrinth gas seal are compared with those of the plain seal and see-through labyrinth seal.

• Special Issue of the Society of Naval Architects of Korea
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• 2008.09a
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• pp.76-83
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• 2008

New and more efficient propulsion systems are required for LNG carriers. One of the proposed systems is a combination of a gas turbine with a heat recovery steam generator. This system constitutes a novel approach, which needs to be analyzed by system analysis and risk assessment to compensate for the lack of field experience. Of specific concern is the high pressure fuel supply system. This paper describes the dispersion and fire analysis performed to identify for safety and design improvement of proposed system.

• Proceedings of the SAREK Conference
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• 2005.11a
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• pp.451-456
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• 2005

The mathematical model for the heat exchangers of absorber and desorber is made in the elementary control volume method and the thermodynamic properties of working fluid. water/ammonia mixture. are calculated by some fundamental subroutines in RefProp 7.0 and flash subroutines made by authors The simulation results show that two-stage cycle has higher COP than single stage if temperature lift is high: the performance of single stage compression cycle can be improved by increase of absorber pressure. but the performance of two-stage compression cycle can not be improved in this way : the compressor discharging temperature of two-stage compression is much lower than that of single stage cycle. which is very important to the safety operation of CA heat pump. Major parameter comparison between the cycles at their optimal configurations is also given.

• Transactions of the Korean hydrogen and new energy society
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• v.14 no.3
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• pp.236-246
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• 2003

This paper focuses on developing a model of a PEM fuel cell stack and to integrate it with realistic model of the air supply system for fuel cell vehicle application. The fuel cell system model is realistically and accurately simulated air supply operation and its effect on the system power and efficiency using simulation tool Matlab/Simulink. The Peak performance found at a pressure ratio of 3, and it give a 15mV increase per cell. The limit imposed is a minimum SR(Stoichiometric Ratio) of 2 at low fuel cell load and 2.5 at high fuel cell load.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.4 no.3
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• pp.183-190
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• 1992

The Collins cryocooler is numerically analysed with the optimization technique, and the optimum operating and design conditions are searched. This paper shows that liquefied helium quantity has an external maximum w.r.t. the total mass flow rate, the mass flow rates through expander and the capacities of heat exchangers. The liquefied helium quantity increases as the compressor exit pressure of the cryocooler does. The maximum quantity of liquefied helium and the maximum coefficient of performance have been found to exist in extremum, depending on the ratios of each heat exchanger capicities to the total one. At the optimum condition, the capacity of heat exchanger in high temperature region is larger than that in low temperature region.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.405-406
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• 2008

Combustor is one of the major component of gas turbine engine and its development is done mostly by performance test. Combustors for aviation gasturbine engines has been successfully tested at the test facility in KARI as well as for stationary gasturbine engines. Full scale combustor test requires large amount of high temperature and pressure air, so the test facility is equipped with big air compressor and heater.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.1
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• pp.70-79
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• 2013

In this work, a steady-state performance modeling and off-design performance analysis of the 2-spool separate-flow turbofan engine named (BR715-56) which is a power plant for the narrow body commercial aircraft is carried out for engine performance behaviors investigation and condition monitoring using a commercial code MATLAB/SIMULINK. Firstly, the engine component maps of fan, high pressure compressor, high pressure turbine and low pressure turbine are generated from similar component maps using the scaling method, and then the off-design performance simulation model is constructed by the mass flow matching and the work matching between components. The model is developed using SIMULINK, which has advantages of easy steady-stare and dynamic modelling and user friendly interface function. It is found that the off-design performance analysis results using the proposed model are well agreed with the performance analysis results by GASTURB at various operating conditions.