• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.110-115
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• 2014

The nuclear power plant was launched by Kori unit 1 in 1978 years. Currently, 23 nuclear power plants have been operating in Korea since 1978 years. The localization was completed for most of the reactor facility from Hanbit(Youngkwang) unit 3&4. However, RCP(Reactor Coolant Pump) and MMIS(Man Machine Interface System) is an important technology that has been excluded from the scope of the technical transfer has been dependent on a specific overseas vendor. Recent success in RCP development through co-operation with government and industries. Developed RCP will be applied to Shin-Hanul unit 1&2 nuclear power plants. The RCP operates in high speed and high pressure condition and only rotating component in the NSSS(Nuclear Steam Supply System). Therefore, the problem of vibration has arisen caused by the hydraulic forces of the working fluid. These forces can influence on the stability characteristics for entire RCS(Reactor Coolant System) loop, and can act as significant destabilizing forces. In this study, vibration evaluation of the pump shaft of development RCP estimated under normal operation and over speed conditions. In order to predict the vibration characteristics and dynamic behavior, modal analysis, critical speed analysis and unbalance response spectrum analysis were performed.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.6
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• pp.867-872
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• 2009

In centrifugal oil filters particles are forced to move toward the filter casing wall by centrifugal force in the rotating oil flow and the particles are trapped and removed on the filter paper installed at the wall. In the present study, flow field of oil and particle motion in a centrifugal oil filter has been numerically calculated in order to estimate the filtering efficiency for various operating conditions. Fluent code was used for the numerical calculations. Uncoupling the oil flow and the particle motion and the use of particle tracking trajectory enabled the estimation of filtering efficiency for various particle sizes, particle density and the filter rotational speed. Higher filtering efficiency was observed for heavier and larger particles as well as higher filter rotational speed. For the typical case of the particle density of $6000kg/m^3$ and the particle size of $10{\mu}m$ at 3500 RPM, the calculated filtering efficiency per passage was 0.31.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.6
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• pp.146-151
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• 2011

Wax spin coating is a part of several wafer handling processes in the silicon wafer polishing station. It is important to ensure the wax layer free of contamination to achieve the high degree of planarization on wafers after wafer polishing. Three-dimensional air flow characteristics in a wax spin coater are numerically investigated using computational fluid dynamics techniques. When the bottom of the wax spin coater is closed, there exists a significant recirculation zone over the rotating ceramic block. This recirculation zone can be the source of wax layer contamination at any rotational speed and should be avoided to maintain high wafer polishing quality. Thus, four air suction ducts are installed at the bottom of the wax spin coater in order to control the air flow pattern over the ceramic block. Present computational results show that the air suction from the bottom is quite an effective method to remove or minimize the recirculation zone over the ceramic block and the wax coating layer.

• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.3
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• pp.715-722
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• 2014

Three twisted rudders fit for large container ships have been developed; 1) the Z-twisted rudder that is an asymmetry type taking into consideration incoming flow angles of the propeller slipstream, 2) the ZB-twisted rudder with a rudder bulb added onto the Z-twisted rudder, and 3) the ZB-F twisted rudder with a rudder fin attached to the ZB-twisted rudder. The twisted rudders have been designed computationally with the hydrodynamic characteristics in a self-propulsion condition in mind. The governing equation is the Navier-Stokes equations in an unsteady turbulent flow. The turbulence model applied is the Reynolds stress. The calculation was carried out in towing and self-propulsion conditions. The sliding mesh technique was employed to simulate the flow around the propeller. The speed performances of the ship with the twisted rudders were verified through model tests in a towing tank. The twisted versions showed greater performance driven by increased hull efficiency from less thrust deduction fraction and more effective wake fraction and decreased propeller rotating speed.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.92-98
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• 2003

Turbine blades experience significant surface degradation with service. This paper presents experimental evidence of blade surface roughness reducing turbine efficiency. Performance tests were conducted in a low speed, single-stage axial flow turbine rig with roughened blade surfaces. Sheets of sandpaper with equivalent sandgrain roughnesses of 106 and $400{\mu}m$ were used to roughen the blades. In these tests, effects of roughened stator vanes and rotor blades were separately evaluated. In the fully rough regime ($k_{s}=400{\mu}m$), the experimental results show an 11 percent decrease in normalized efficiency with roughness only on stator vanes ; an 8 percent decrease with roughness only on rotor blades ; and a 19 percent decrease with roughness on both the stator and rotor blades. In the transitionally rough regime ($k_{s}=106{\mu}m$), the trends are similar approximately 4 percent decrease with either roughened stator or roughened rotor and an 8 percent decrease with roughness on both stator and rotor blades. Thus, roughened stator vanes incur more performance penalty than roughened rotor blades.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.5
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• pp.79-89
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• 2012

The objectives of this paper were to evaluate the wind flow behind the livestock ventilation fan for small-scale wind power generation and to make flow profiles of imaginary ventilation fan for future simulation works. The field experiments using typical 50-inch fan indicated that the wind flow behind the ventilation fan had a good possibility of power generation with its high and steady wind speeds up to a distance of 2 m. The expected electricity yield was almost 101~369 W with a small (0.8 m radius) wind turbine. The decline of ventilation fan performance caused by the obstacle was also not significant with about 4 % from a distance of 2 m. The flow profiles for the computational fluid dynamics (CFD) simulation was created by combining the direction vectors analyzed from tuft visualization test and the flow predicted by the rotating fan modeling. The flow profiles are expected to provide an efficient saving of computational time and cost to design a better wind turbine system in future works.

• Journal of Power System Engineering
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• v.17 no.4
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• pp.51-57
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• 2013

The length and position of the inlet port on the double tube heat exchanger is analyzed by CFX ver.11 for studying the characteristic of its flow distribution. When the boundary conditions of the inlet temperature and mass flow rate were each $20^{\circ}C$ and 10 ~ 50 kg/min, 3 models that are based on the distance between the inlet port and the center of the heat exchanger(0, 5.025, 10.05 mm) were analyzed to find the uniformity of the flow rate. Based on the flow rate, 4 lengths (23.723, 33.890, 44.057, 57.274 mm) were used to study the flow distribution according to Reynolds Number. The results show that, when the distance from the inlet to the position of the center of the heat exchanger is 10.05 mm and the length is 57.274 mm, the flow distribution is the most unified.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.1067-1071
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• 2004

In this paper, the characteristic of the regenerative pump is reviewed by the measurement and the analysis. The dominant noise sources are harmonic components of the rotating impeller frequency. The acoustic characteristics and the noise source position at the dump are identified. In order to reduce the high-level peak noise, the interior flow of the pump chamber is analyzed by CFD (Computational Fluid Dynamics). Acoustic pressure is calculated with Ffowscs Williams and Hawkings equation. As the result of the analysis new design of the pump chamber is recommended. The recommended pump is compared with original pump by evaluating the RMS value of a interior static pressure and the sound pressure level. The new pump chamber recommended by analysis results is proved by a process of the measurement. The overall SPL of a recommended pump is reduced about 3 dBA.

• Advances in aircraft and spacecraft science
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• v.5 no.3
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• pp.349-362
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• 2018

A non-linear numerical simulation technique for predicting the unsteady performances of an airbreathing engine is developed. The study focuses on the simulation of integrated propulsion systems, where a closer coupling is needed between the airframe and the engine dynamics. In fact, the solution of the fully unsteady flow governing equations, rather than a lumped volume gas dynamics discretization, is essential for modeling the coupling between aero-servoelastic modes and engine dynamics in highly integrated propulsion systems. This consideration holds for any propulsion system when a full separation between the fluid dynamic time-scale and engine transient cannot be appreciated, as in the case of flow instabilities (e.g., rotating stall, surge, inlet unstart), or in case of sudden external perturbations (e.g., gas ingestion). Simulations of the coupling between external and internal flow are performed. The flow around the nacelle and inside the engine ducts (i.e., air intakes, nozzles) is solved by CFD computations, whereas the flow evolution through compressor and turbine bladings is simulated by actuator disks. Shaft work balance and rotor dynamics are deduced from the estimated torque on each turbine/compressor blade row.

• Journal of Drive and Control
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• v.19 no.4
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• pp.62-69
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• 2022

Construction machinery is exposed to accidents such as collisions, narrowness, and overturns during operation. In particular, mobile crane is operated only with the driver's vision and limited information of the assistant worker. Thus, there is a high risk of an accident. Recently, some collision avoidance device using sensors such as cameras and LiDAR have been applied. However, they are still insufficient to prevent collisions in the omnidirectional 3D space. In this study, a rotating LiDAR device was developed and applied to a 250-ton crane to obtain a full-space point cloud. An algorithm that could provide distance information and safety status to the driver was developed. Also, deep-learning segmentation algorithm was used to classify human-worker. The developed device could recognize obstacles within 100m of a 360-degree range. In the experiment, a safety distance was calculated with an error of 10.3cm at 30m to give the operator an accurate distance and collision alarm.