• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.4
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• pp.54-60
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• 2007

A new method that optimizes a control of hydrocarbon (HC) addition to diesel exhaust gas for HC type DeNOx catalyst system has been developed. These catalysts are called as the HC-DeNOx catalyst in this paper. The system using HC-DeNOx catalyst requires a resonable quantity of hydrocarbons addition in the inlet gas of the catalyst, because the HC concentration in a diesel engine is so low that the HC is not sufficient for NOx conversion. Generally ambient temperature in the exhaust manifold is $250{\sim}350^{\circ}C$, so spray behavior in this case is different from that of any other condions. This research shows spray behavior of injected hydrocarbons in the transparent exhaust manifold.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.10
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• pp.697-703
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• 2010

In recent semiconductor manufacturing clean rooms, air washers are used to remove airborne gaseous contaminants from the outdoor air introduced into a clean room. Meanwhile, there is a large amount of exhaust air from a clean room. From an energy conservation point of view, heat recovery is useful for reducing the outdoor air conditioning load required to maintain a clean room. Therefore it is desirable to recover heat from the exhaust air and use it to cool or heat the outdoor air. In the present study, numerical analysis was conducted to evaluate the recovered heat of an exhaust air heat recovery type air washer system, which is the key part of an energy saving outdoor air conditioning system for semiconductor clean rooms. The present numerical results showed relatively good agreement with the available experimental data.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.12
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• pp.628-637
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• 2017

This study was conducted to present an effective control method for the common duct system to uniformly discharge volume flow rate exhausted from the kitchen and bathroom of each household in an apartment regardless of the position of household. Since the common duct system is installed vertically and the ventilator is installed in the terminal, the static pressure of each household decreases when vertical height increases. Therefore, the volume flow rate exhausted from each household is different. In order to improve such a phenomenon, a constant air volume damper shall be installed in a branch duct coupled with a common vertical duct system. The selected ventilator should also be able to handle the maximum volume flow rate considering diversity factor. Therefore, a uniform volume flow rate must be exhausted from all households where the hood is operated. This paper mainly focuses on suggestion of an optimum exhaust control method by comparing exhaust performance of each household according to the presence or absence of a constant air volume damper.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.2
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• pp.139-146
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• 2011

The ventilation performance of a vertical exhaust duct system in the high riser public house has been evaluated by a commercial software, Fluid Flow, which solves pressure losses through the duct system including bathroom fans and a hybrid roof fan. During the numerical simulations, outdoor wind condition and stack effects in summer and winter were considered as well as the operating conditions of a basement damper and the roof fan. The results show that the bathroom ventilation in summer is the most unsatisfactory. The opening of the basement damper has a problem that the polluted air in the lower floors is exhausted to the underground parking lot, not to the rooftop. If the basement damper is closed, the exhaust flow rate in the lower floors is not sufficient due to the strong flow resistance in the long vertical duct even though the roof fan is under operating.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.641-646
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• 2004

Noise and vibration was encountered in exhaust duct system which is connected with a gas turbine and a heat recovery steam generator(HRSG) of a cogeneration power plants. Especially, these problems occurred when water was added to the fuel injection to reduce NOx contents of the exhaust gas. Through the cavity mode analysis and measurements, It was concluded that these problems occurred due to the acoustic resonance between the duct cavity mode and the excitation force induced by turbulent gas flow during water injection. To reduce the noise and vibration, optimal baffle plate to change the cavity mode was installed inside of duct and noise levels of about 8 dB(A) are reduced in duct system. The effects of baffle plate and guide vane to the HRSG or inlet duct vibration were also evaluated and it was verified that there is no relation to the resonance phenomena. So, vibration of inlet duct was easily reduced by the reinforcement of structures.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.9
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• pp.743-749
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• 2015

The purpose of this study is to predict the performance of an indirect evaporative cooling system, and to evaluate its energy saving effect when applied to the exhaust heat recovery system of an air-handling unit. We derive the performance correlation of the indirect evaporative cooling system using a plastic heat exchanger based on experimental data obtained in various conditions. We predict the variations in the performance of the system for various return and outdoor air conditioning systems using the obtained correlation. We also analyze the energy saving of the system realized by the exhaust heat recovery using the typical meteorological data for several cities in Korea. The average utilization rate of the sensible cooling system for the exhaust heat recovery is 44.3% during summer, while that of the evaporative cooling system is 96.7%. The energy saving of the evaporative cooling system is much higher compared to the sensible cooling system, and was about 3.89 times the value obtained in Seoul.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.802-806
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• 2004

For the protection of the local air quality and the global atmosphere, the emissions of trace species including nitric oxides (NO and NO$_2$) from gas turbines are regulated by local governments and by the International Civil Aviation Organization. In-situ measurements of such species are needed not only for the development of advanced low-emission combustion concepts but also for providing emissions data required for the sound assessment of the effects of the emissions on environment. We have been developing a laser absorption system that has a capability of simultaneous determination of NO and NO$_2$concentrations in the exhaust jets from aero gas turbines. A diode laser operating near 1.8 micrometer is used for the detection of NO while a separated visible tunable diode laser operating near 676 nanometers is used for NO$_2$. The sensitivities at elevated temperature conditions were determined for simulated gas mixtures heated up to 500K in a heated cell of a straight 0.5 m optical path. Sensitivity limits estimated as were 30 ppmv-m and 3.7 ppmv-m for NO and NO$_2$, respectively, at a typical exhaust gas temperature of 800K. Experiments using the simulated exhaust flows have proven that $CO_2$ and $H_2O$ vapor - both major combustion products - do not show any interference in the NO or NO$_2$ measurements. The measurement system has been applied to the NO/NO$_2$ measurements in NO and NO$_2$ doped real combustion gas jets issuing from a rectangular nozzle having 0.4 m optical path. The lower detection limits of the system were considerably decreased by using a multipass optical cell. A pair of off-axis parabola mirrors successfully suppressed the beam steering in the combustion gas jets by centralizing the fluctuating beam in sensor area of the detectors.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.2
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• pp.527-539
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• 2018

The subway used by many passengers is required to maintain a safe and comfortable environment and PSD (Platform Screen Door) must be installed in the platform after reinforcing the standard in 2003. In the previous research, in case of subway fire to control it, it is necessary to design the optimal ventilation and smoke exhaust system according to equipment capacity of the smoke exhaust system. Therefore, in this study, based on the results of previous research, three-dimensional numerical analysis was performed for the CO gas and smoke flow by the subway ventilation system in case of platform fire. As a result of this study, it was found that in case of emergency, if only the upper-level smoke exhaust system is activated, the risk of evacuation is high due to CO gas (653.8 ppm) and smoke concentration ($768.4mg/m^3$). And when all the smoke exhaust systems are activated and only the fire side PSD is opened, CO gas (36.0 ppm) and smoke concentration ($26.2mg/m^3$) are detected and the propagation range of smoke flow was reduced. When all the smoke exhaust systems are activated and only the fire side PSD is closed, it was analyzed as the most effective ventilation mode in the evacuation environment due to the absence of smoke-recirculation.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.5
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• pp.82-88
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• 2001

The EGR is needed fur one of various strategies to reduce NOx emission. But to get the proper EGR rate, the intake and exhaust system become complicated. That is a reason why we consider using the internal EGR system. The internal EGR is a system which reduces NOx by controling the residual gas fraction in cylinder by changing valve timing and valve lift of intake and exhaust. In this paper, characteristics of volumetric efficiency and residual gas fraction in cylinder were investigated for various engine speeds by changing valve timing and valve lift of intake and exhaust in the 4 stroke-cycle diesel engine. Volumetric efficiency and residual gas fraction were calculated by the method of characteristics. As the results, residual gas fraction and volumetric efficiency in cylinder by variable valve timing were visualized.

• Journal of the korean Society of Automotive Engineers
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• v.14 no.3
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• pp.57-70
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• 1992

As automobile industry develope, design techniques to satisfy light weight and high efficiency in automobile parts is demanded. In this study modal analysis is performed using transfer matrix method to identify dynamic characteristics of exhaust system. It is estimated the theoretical transfer function by Pestel-Leckey method and the mode shapes in 3-D graphic. the validity of developed program is verified by comparing with the experimental results of exhaust system. Estimated modal parameters(natural frequency, vibrational mode, transfer function) are in accord with the experimental results. From the developed program, we can predict a location of the hanger which is determined by the lowest RMS value point, when displacement is given as an input at the engine side. We can find that attachment of spring modelled hanger at the hanger location bring vibration level down.