• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1996.11a
• /
• pp.1053-1057
• /
• 1996

The purpose of this study is to bring out the optimal design factors which effect on dynamic characteristics in the design of proportional flow control valve with fast response characteristics, and to verify the validity of the design factors In this study, force feedback type flow control valve with nozzle-flapper is studied. And, the influences which fixed orifice, nozzle diameter, and maximum displacement between nozzle and flapper effect on dynamic characteristics are analyzed. We have done simulations using the optimal design factors and simulink(Matlab) as a simulation tool, and verified the validity of our simulations by means of comparison our simulation results with an experimental results of another similar valve.

• Nuclear Engineering and Technology
• /
• v.29 no.6
• /
• pp.1-7
• /
• 1997

원자력 발전소의 주급수 유량은 원자로 열출력 산출에 사용되는 중요한 변수로서, 노심관리 뿐만 아니라 원자로 안전운전에도 중요하며, 발전소 출력에 직접적인 영향을 미친다. 그러므로 현재 사용되고 있는 주급수 유량 측정설비의 정확도 검증 및 보정을 위하여 정확한 유량측정법의 개발이 필요한 실정이다. 본 연구는 화학 추적자 방법에 의한 고정밀 유량측정 기술을 개발하여, 원자력 발전소 주급수 계통의 유량측정에 사용되고 있는 벤츄리(Venturi), 노즐(Nozzle), 오리피스(Orifice) 등의 유량계에 관한 검증용으로 활용함으로서 발전소의 안전성을 유지하는 범위에서 출력을 극대화시킨다는 목적으로 예비 실험장치를 설계 설치하여, 본 방법의 유효성에 대해서 검토하였다. 그 결과, 본 연구에 사용한 추적자 방법은 유량변동에도 좋은 응답성을 보이고 있으며, 유량측정에 있어서도 매우 신뢰성 있는 측정이 가능하다.

• The Journal of the Acoustical Society of Korea
• /
• v.36 no.6
• /
• pp.371-377
• /
• 2017

The performance of an air conditioner is closely related to the cooling performance of a split-type outdoor unit so that, in most of the relevant preceding studies, the independent performance of an axial fan in an outdoor unit has been studied. However, there is a lack of research on the effects of other components in an outdoor units was rarely investigated. Therefore, in this paper, the effects of the fan orifice among other parts on the flow performance of the outdoor unit was numerically investigated. A virtual fan tester consisting of 18 million grids was developed for highly resolved flow simulation. The unsteady RANS (Reynolds-averaged Navier-Stokes) equations are numerically solved by using finite-volume CFD (Computational Fluid Dynamics) techniques. In order to verify the validity of the numerical methods, the predicted P-Q curve of the cooling fan in a full outdoor unit is compared with the measured one. Optimization of orifice shape was carried out for maximum flow performance of the outdoor unit using the validated numerical method.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.40 no.6
• /
• pp.397-402
• /
• 2016

To produce adequate electricity in nuclear and thermal power plants, an optimal amount of steam should be supplied to a generator connected to high- and low-pressure steam turbines. A turbine output control device, which is a special steam valve employed to supply or interrupt the steam to the turbine, is operated using a hydraulic servo actuator. In power plants, the performance of servo actuators is degraded by the air generated from the hydraulic system, or causes frequent failures owing to an increase in the wear of the seal. This is due to the seal being burnt as generated heat using the produced compressed air. Some power plants have exhausted air using a fixed orifice, and thus they encounter power loss due to mass flow exhaust. Failures are generated in hydraulic pumps, electric motors, and valves, which are frequently operated. In this study, we perform modeling and analysis of the load-sensing air-exhaust valves, which can be passed through very fine flow under normal use conditions, and exhaust mass flow air at the beginning stage as with existing fixed orifices. Then, we propose a method to prevent failures due to the compressed air, and to ensure the control accuracy of hydraulic servo actuators.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.36 no.8
• /
• pp.790-796
• /
• 2008

Typical solid rocket motors have a fixed propellant grain shape and nozzle throat size resulting in a fixed motor thrust. Pintle nozzle has been suggested as a means of providing variable thrust while maintaining the inherent advantage of solid rocket motors. In this study, the pintle shape effect on nozzle performance is investigated using experimental-aided Computational Fluid Dynamics(CFD). The pintle shape is modified by a principle of monotony. CFD analysis is performed using Fluent by applying the turbulent model. This analysis indicates that nozzle thrust and pintle load are influenced by change of nozzle shock pattern and flow separation due to pintle shape and there exists a high-performing pintle shape.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
• /
• 2010.04a
• /
• pp.166-170
• /
• 2010

Six different size of torch-ignition device were applied in a constant volume combustion chamber for evaluating the effects of torch-ignition on combustion. The torch-ignition device was designed six different volumes and same orifice size. The combustion pressures were measured to calculate the mass burn fraction and combustion enhancement rate. In addition, the flame propagations were visualized by shadowgraph method for the qualitative comparison. The result showed that the combustion pressure and mass burn fraction were increased when using the torch ignition device. And the combustion duration were decreased. The combustion enhancement rates of torch-ignition cases were improved in comparison with conventional spark ignition. Finally, the visualization results showed that the torch-ignition device the torch-ignition induced faster burn than conventional spark ignition due to the earlier transition to turbulent flame and larger flame surface, during the initial stage. And the initial flame propagation was effected torch-ignition volume.

• Fire Science and Engineering
• /
• v.30 no.3
• /
• pp.86-93
• /
• 2016

The effects of the shape of a drencher head on the flow characteristics and radiation attenuation of a water curtain, in order to prevent a fire spread, were experimentally studied. The distance (h) between the orifice exit and deflector and the diameter of deflector (D) were varied as the shape factors of the head, with the same orifice diameter (d). It was found that an increase in h leads to an increase in the water flow rate and spray angle. However, the change in the spray angle decreases with increasing D. Increasing D brings about a subtle increase in the water flow rate and a significant decrease in the spray angle. A larger value of D makes it possible to produce a flatter pattern of the water curtain, but reduces the uniformity of the droplets inside the spray angle. The mean droplet diameter decreases significantly as the operating pressure increases. However, the variation in the shape of the drencher head does not significantly affect the change in the mean diameter at the same operating pressure. Finally, it was found that the radiation attenuation afforded by the water curtain at the same operating pressure was affected by water flow rate and droplet uniformity, which were determined by h and D, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.12
• /
• pp.723-729
• /
• 2019

Turbochargers are an effective device to reduce the fuel consumption. In this study, the mass flow rate of pulsating flow in the twin-scroll turbocharger for the gasoline engine of passenger vehicles was measured. Pulsating flow was achieved using a pulse generator and the mass flow rate of the unsteady pulsating flow was analyzed by comparing it with those of the steady flow. The pulse generator consisted of a rotating upper plate and a fixed lower plate. To measure the mass flow rate of unsteady flow, the orifice flow meter equipped with the difference pressure transducer was used. To analyze the low speed performance of the turbocharger, the measurement was carried out in the speed of turbocharger from 60,000rpm to 100,000rpm. The mass flow parameters of the unsteady pulsating flow showed a large difference compared to those of the steady flow. Those of the unsteady flow showed the hysteresis loop surrounding the mass flow parameters of the steady flow and the maximum variation of the mass flow parameters were 5.0 times those of the steady flow. This phenomenon is the result of the filling and emptying the turbine volute space due to pulsating flow.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.17 no.3
• /
• pp.182-188
• /
• 2014

In an oscillating water column (OWC)-type wave energy conversion system, the performance of the OWC chamber depends on the chamber shape, as well as the incident wave direction and pressure drop produced by the turbine. Although the previous studies on OWC chambers have focused on wave absorbing performance in ideal operating conditions, incident waves do not always arrive normally to the OWC chamber in real sea conditions, especially in fixed devices. The present study deals with experiments and numerical calculations to investigate the effects of wave direction on the performance of the OWC chamber. The experiments were carried out in a three-dimensional wave basin for five different wave directions, including the effect of turbine using the corresponding orifice. The wave elevation inside the chamber was measured at the center point under various incident wave conditions. The numerical study was conducted by using a numerical wave tank-based volume-of-fluid model to compare the results with experimental data and to reveal the detailed flows around the chamber.