• Nuclear Engineering and Technology
• /
• v.30 no.4
• /
• pp.328-341
• /
• 1998

This paper presents in detail the hydraulic characteristic measurements using LDV(Laser Doppler Velocimetry) in subchannels of a HANARO, KAERI research reactor, fuel bundle. The fuel bundle consists of 18 axially finned rods with 3 spacer grids and has a cylindrical configuration. Axial velocity and turbulent intensity were measured. The effects of the spacer grids on the turbulent flow were investigated using the experimental results. Pressure drops for each component of the fuel bundle were measured, and the friction factors of the fuel bundle and the loss coefficients for the spacer grids were estimated from the measured pressure drops. The turbulent thermal mixing phenomena were discussed.

• Journal of Welding and Joining
• /
• v.27 no.4
• /
• pp.60-66
• /
• 2009

The cylinder horn is designed to increase uniformity of the displacement on the output face through simulation and experiments for the simple cylinder, spool and step horns. The modal analysis is conducted numerically to calculate the vibration mode and stress distribution of the cylinder horn, and the design of experiment (DOE) technique is employed to determine the optimum configuration of the spool horn. Displacement of the cylinder horn was measured using the Laser Doppler Vibrometer (LDV), and experimental results show good agreements with the predicted results. It appears that uniformity higher than 95% can be achieved with the spool horn when the proper dimension of the groove is used.

• Journal of the korean Society of Automotive Engineers
• /
• v.15 no.3
• /
• pp.1-9
• /
• 1993

디젤 엔진의 연소 과정에서 흡입공기와 분사된 연료의 최적 혼합기 형성이 배기성분, 연료효율 등 엔진의 성능을 향상시키는데 있어 매우 중요한 과제중의 하나이다. 이를 위하여 연료분무 현상에 대한 연구와 더불어 연소실내 공기유동 현상에 대한 연구가 주요 관심대상이 되어왔다. LDV를 이용한 3-D 유속측정 및 각종 CFD Code를 이용한 유동해석등의 방법으로 엔진 실린더 내부의 유동현상을 이해하는데 많은 도움이 되고 있으나 아직도 엔진연소실설계 등 엔진 개발에 있어서는 종래의 방법에 의한 실린더내 와류 강도의 비교평가에 크게 의존하고 있으므로 여기서는 디젤 엔진의 와류를 측정 평가하는 방법으로 Paddle Wheel회전을 이용한 Paddle Wheel식 Swirl Meter방식과 실린더내 흡입공기의 각 운동량을 측정하는 Impulse식 Swirl Meter 방식에 대해 고찰하고자 한다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.05a
• /
• pp.414-419
• /
• 2003

There are some methods fur extracting mode shapes from a continuously scanned data such as a modulation, Chebyshev polynomial, and Hilbert approach. In this paper, Chebyshev and Hilbert approaches were investigated through the numerical experiment first. As some experimental parameters were altered with small quantities, data were checked and plotted. From those results, the effects of unexpected parameters will be configured. And then, it will be actually helpful to select the proper method for specific testing environments.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.12 no.11
• /
• pp.1004-1011
• /
• 2000

Experimental and computational studies were carried out to confirm the turbulent enhancement of the cooling system of nuclear reactor by large scale vortex generation in nuclear fuel bundle. The large scale vortex motions were generated by rearranging the inclination angles of mixing vanes to the coordinate directions. Axial development of mean and turbulent velocities in the subchannels were measured by the 2-color LDV system. Eddy diffusivity heat flux model and $k-varepsilon$ model were employed to analyze the turbulent heat and fluid flows in the subchannel. The turbulence generated by split mixing vanes has small length scales so that they maintain only about $10 D_H$ after the spacer grid. On the other hand, the turbulences generated by the large scale vortex continue more and remain up to $25 D_H$after the spacer gird.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.22 no.9
• /
• pp.1307-1316
• /
• 1998

Engine turbulences obtained by LDV measurement near the compression TDC was analyzed by the classic turbulence theory. Turbulences were quantified by a cycle resolved analysis and processed to reveal integral time scale and length scale. Three different definitions were applied to obtain the turbulence time scales and then compared each others. The classic turbulence theory with the several assumptions for engine application proven to be very efficient for understanding engine turbulence in this study. It was found that the integral length scale is strongly affected and increased by tumble flow.

• Proceedings of the KSME Conference
• /
• 2008.11b
• /
• pp.2001-2006
• /
• 2008

The most concerning issue of these days is the energy crisis by increasing threat of dependency on foreign oil and its volatility itself. In the situations, the PHEV is drawing attention for the next generation's car which could give a chance to decrease the dependency on foreign oil. As well as, the Korean electric power infrastructure is a strategic national asset that is under utilized most of the time. With the proper changes in the operational paradigm, it could generate and deliver necessary energy to charge the PHEVs which could penetrate the market within few years. In doing so, it would reduce greenhouse gas emissions, improve the economics of the electricity industry, and reduce the energy dependency. This paper investigate the technical potential and impacts of using the existing idle capacity of the electric infrastructure in conjunction with the emerging PHEVs technology to meet the majority of daily energy needs of the Korean LDV fleet.

• Journal of Applied Reliability
• /
• v.5 no.4
• /
• pp.439-450
• /
• 2005

Thermal deformation of Digital Television effect friction noise directly. However there was no methods to find and to solve the thermal friction noise which is huge problem in Digital Television In this study, to figure out occurrence cause of friction noise of the product, we measured thermal deformation of the product to organize a triggering device united with Laser Doppler Vibrometer(LDV) which turned occurrence moment of thermal friction noise into a possibility to measure. In conclusion, we could offer an effective information of design, and ensured ESPI(Electronic Speckle Pattern Interferometry) measure technique which is more detailed than the past way.

• Proceedings of the KIEE Conference
• /
• 2001.07d
• /
• pp.2519-2521
• /
• 2001

This paper presents an auxilary beam-assisted adaptive compensation technique applied to alleviate the problem of LDV's body vibration. The LMS algorithm is applied to adaptively compensate the body vibration utilizing the reference signal provided by the auxiliary beam. The usefulness of the proposed technique is verified computer simulations performed for diverse types of target signals and body vibration.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.53 no.2
• /
• pp.116-122
• /
• 2004

A micromachined self-exited piezoelectric cantilever has been fabricated using PZT(52/48) thin film. For the application to biosensor using antigen-antibody interaction, electromechanical properties such as resonant frequency and quality factor of micromachined piezoelectric cantilever were important factors. Electromechanical properties and resonant behaviors of microfabricated cantilever were simulated by FEA (Finite Element Analysis) using Coventorware$^{TM}$2003. And these characterization of microcantilever were measured by using LDV(Laser Doppler Vibrometer) to compare with FEA data. We present the resonant frequency shift of micromachined piezoelectric cantilevers due to combination of mass loading and change of spring constant by gold deposition. Experimental mass sensitivities of microcantilever were characterized by Au deposition on the backside of microcantilever. Mass sensitivities with $100{\times}300$ ${\mu}{\textrm}{m}$ dimension cantilever from simulation and experimental were 5.56 Hz/ng and 16.8 Hz/ng respectively.y.