• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.475-479
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• 2011

Leak problem with large pressure drop occurrs non-periodic shock pulsation due to the deterioration of a isolation valve in feed-water recirculation piping system. This paper discusses on the shock vibration and noise occurred due to the effect of acoustical shock pulsations by degradation of the isolation valve in a power site.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.7
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• pp.967-975
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• 2000

Transient characteristics of a boiler and turbine system for a steam power plant are simulated. One-dimensional unsteady models are introduced for each component. An interaction between boiler and turbine and a control of the water level in the drum are taken into account. Transient responses of the system to the variations of main system variables such as fuel and air flow rate, cooling water injection rate at the attemperator, gas recirculation rate at the furnace and opening of the turbine control valve are examined. Effect of fluid inertia and tube wall thermal inertia on predicted dynamic behavior is investigated.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.8
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• pp.734-741
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• 2010

In this paper, an intake RCV system for low noise turbo engine was developed through optimization process of a geometric path of compressor housing and an open rate of recirculation valve. At first, the critical customer requirement from voice of customer was defined and quality function deployment of an intake RCV system was executed. And then, the renovative concept design using pugh matrix method was selected as final concept for satisfaction of requirement. Simultaneously, system analysis was carried by function diagram and fishbone diagram. Next, control factors and levels for the optimal design were performed. And, the optimal design of an intake RCV system was studied using design of experiment. Conclusively, we achieved not only cancellation tip-out noise at the driving condition but also improvement of NVH commodity through optimization process of an intake RCV system, which is optimal configuration of compressor housing and recirculation valve.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.2
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• pp.1-8
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• 2002

The flow and combustion patterns have been investigated inside the gasoline engine cylinder with the swirl or tumble flow, whereas the air flow characteristics, which are generated in the part of intake system before entering into the intake manifold, have not been known completely. It is necessary to analyze the flow field in the intake system consisting of air rater, throttle valve and intake manifold. The throttle valve, used to control the intake air flow rate, is important because it makes various mass flow rate and flow patterns. Three-dimen-sional How characteristics such as velocities, turbulent intensities and Reynolds shear stresses are measured by the hot wire anemometer at the exit of the throttle valve with the variation in the valve opening angle($15^{\circ}$, $45^{\circ}$, $75^{\circ}$ and $90^{\circ}$) and the Reynolds numbers (45000, 70000 and 140000). There are a lot of changes in flow characteristics at $75^{\circ}$ due to the large recirculation flow comparing with those of the other cases, and the streamwise velocity is especially enforced strongly below the valve shaft. The other component velocities are relatively large near the centerline parallel to the valve shaft. The effects of the Reynolds number on the flow field are not severe.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.4
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• pp.418-423
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• 2014

Small hydropower has been considered as a solution to resolve the problem of exhaustion of fossil fuel and industrial pollution. In this study, we developed and tested a Cross-Flow Turbine with two guide vanes to optimize the small hydropower for the site condition with large fluctuation of head and flow rate. Furthermore, in the condition of constant inlet head, CFD analysis was carried out to analyze the effect of air suction and valve position on the performance characteristics. The results showed that the air suction can minimize the hydraulic loss caused by the Recirculation flow in the runner passage and flow impact on main shaft so that it can increase the turbine efficiency and output power.

• Korean Chemical Engineering Research
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• v.58 no.4
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• pp.642-650
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• 2020

In general, the circulation path of the fluidized particles in a CFB (Circulating Fluidized Bed) boiler is such that the particles entrained from a combustor are collected by a cyclone and recirculated to the combustor via a sealpot which is one of non-mechanical valves. However, when a fluidized bed heat exchanger (FBHE) is installed to additionally absorb heat from the fluidized particles, some particles in the sealpot pass through the FBHE and then flow into the combustor. At this time, in the FBHE operated in the bubbling fluidization regime, if the heat flow is not evenly distributed by poor mixing of the hot particles (800~950 ℃) flowing in from the sealpot, the heat exchanger tubes would be locally heated and then damaged, and the agglomeration of particles could also occur by formation of hot spot. This may affect the stable operation of the circulating fluidized bed. In this study, the unevenness of heat flow arising from structural problems of the FBHE of the domestic D-CFB boiler was found through the operating data analysis and the CPFD (Computational Particle Fluid Dynamics) simulation using Barracuda VR. Actually, the temperature of the heat exchanger tubes in the FBHE showed the closest correlation with the change in particle temperature of the sealpot. It was also found that the non-uniformity of the heat flow was caused by channeling of hot particles flowing in from the sealpot. However, it was difficult to eliminate the non-uniformity even though the fluidizing velocity of the FBHE was increased enough to fluidize hot particles vigorously. When the premixing zone for hot particles flowing in from the sealpot is installed and when the structure is changed through the symmetrization of the FBHE discharge line for particles reflowing into the combustor, the particle mixing and the uniformity of heat flow were found to be increased considerably. Therefore, it could be suggested that the structural modification of the FBHE, related to premixing and symmetric flow of hot particles, is an alternative to reduce the non-uniformity of the heat flow and to minimize the poor particle mixing.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.39 no.1
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• pp.71-76
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• 2002

Because the driving time is increased under the low speed by rapidly increasing of vehicles, this paper is presented a new ignition control system for improvement the fuel economy, which only some of cylinders are using under the idle status or low speed and preserving the engine rpm. is applicable to effective in fuel economy. An actual hardware was made to prove this new control system. The developed variable cylinder engine concentrated the heat neat the cylinders in idle status or low speed, so there was a problem in re-ignition. It was the reason of a lot of exhaust gas, high fuel consumption and instability of engine revolution. In this paper, in order to solve above problem to show the improvement fuel economy using the new ignition control system and valve opening period at idle status of low speed.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.5
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• pp.528-534
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• 2011

This study analyzes thermal stress and durability fatigue on the modelling of EGR valve. In case of 10% opening at its inlet, the minimum temperature gets cool as 3 times as inlet temperature. The maximum equivalent stress becomes lowest as the value of $2.6274{\times}109$ Pa and fatigue life becomes highest as 23.657 Cycle. But the minimum temperature gets cool as 2.2 times as inlet temperature in case of 50% opening at its inlet. The equivalent stress becomes higher and fatigue life becomes lower than in case of 10% opening. In case of 100% opening at its inlet, the minimum temperature gets cool as 0.2 times as inlet temperature. The equivalent stress becomes lower and fatigue life becomes higher than in case of 50% opening. Maximum equivalent stress and total deformation are shown at the closing of EGR valve by the pressure of inflow gas. The structural analysis result of this study can be effectively utilized with the design of EGR valve by investigating prevention and durability against its damage.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.322-325
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• 2007

This paper shows the development procedure of the low pressure LOX feed system which is used in the liquid rocket with a turbopump. Korean Air has cooperated with KARI in developing the LOX feed system to turbopump. The LOX feed system is characterized with cryogenic temperature and the thin-thickness tube for weight saving. The system in this project is composed with a main feed line and a recirculation line for the LOX temperature conditioning. Each piping system has many components, namely, bellows, filter, orifice, valves, flange and support. In this paper, system design & manufacturing, structural & thermal analyses, and component tests are explained. Finally, the system was assembled to the KARI's PTF test facility and functioned well to meet its required performance.

• Nuclear Engineering and Technology
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• v.25 no.1
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• pp.37-50
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• 1993

To evaluate the sequence of event and the Thermohydraulic behavior during total loss of feedwater accident and recovery procedure, a RELAP5/MOD3 calculation is performed and compared with the LOFT L9-l/L3-3 experiment. Also, the predictability of the code for the major Thermohydraulic phenomena following the accident is assessed. As a result, it is found that a pressure control using the spray until the time the water level reaches the top of the pressurizer, an overpressure protection by pressurizer PORV, a recovery of the secondary heat removal capability by refilling steam generator, and an effective cooldown by the continued natural circulation can be performed without core uncovery. It is also found that the plant-specific evaluation is necessary to confirm the effectiveness of the current symptom-oriented emergency operating procedure, especially in an overpressure protection performance and steam generator recovery performance.