• Journal of Mechanical Science and Technology
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• v.18 no.11
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• pp.2032-2041
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• 2004

Results from an experimental study of flow distribution in a close-coupled catalytic converter(CCC) are presented. The experiments were carried out with a flow measurement system specially designed for this study under steady and transient flow conditions. A pitot tube was a tool for measuring flow distribution at the exit of the first monolith. The flow distribution of the CCC was also measured by LDV system and flow visualization. Results from numerical analysis are also presented. Experimental results showed that the flow uniformity index decreases as flow Reynolds number increases. In steady flow conditions, the flow through each exhaust pipe made some flow concentrations on a specific region of the CCC inlet. The transient test results showed that the flow through each exhaust pipe in the engine firing order, interacted with each other to ensure that the flow distribution was uniform. The results of numerical analysis were qualitatively accepted with experimental results. They supported and helped explain the flow in the entry region of CCC.

• Journal of Power System Engineering
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• v.11 no.4
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• pp.5-11
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• 2007

본 연구는 SI기관 실린더 내의 유동장 변이 과정을 3차원 LDV 측정 기술을 사용하여 흡입과 압축과정 동안 정량적으로 분석하였다. 실험은 헤드에 각각 2개의 흡입밸브와 배기밸브를 갖는 기관이 모터링되는 공회전 상태에서 실시하였다. 지난 30년 동안 텀블과 스월은 실린더 내의 평균 유동 정량화에, 난류운동에너지는 난류 측정에 많이 사용되어 왔다. 그러나 텀블은 solid body 회전 유동을 비교하는데 적절하며, 서로 다른 유동 패턴 비교에는 부적절 하다는 것이 보고되고 있는 실정이다. 3차원 LDV시스템의 우수한 공간 분석 능력은 순간적인 유동장구조와 더불어 상대적으로 미세한 유동장의 구조 까지도 측정이 가능 하도록 하였다. 따라서 측정한 결과로부터 유동장의 난류운동에너지 등가면을 계산할 수 있었다. 본 실험 결과는 실린더 내의 난류 유동장 특성을 난류운동 에너지 등가면 정보를 이용하여 세심하게 관찰할 수 있음을 제시하고 있다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.6
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• pp.1358-1371
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• 1988

The combustion process is the most important process in the S.I. engine since it determines performance and emissions. As the flame propagates slowly due to EGR or lean mixture, the fast burn system is widely used in the modern engines in order to improve engine performance. As the basic research for the fast burn system of the S.I engine, this study is aimed to identify the effects of the intake port design on the air motion inside a cylinder. In this study various intake ports were designed and tested. Swirl levels for the different intake ports were measured by a swirl meter and LDv.Also transient air motion inside a cylinder is further investigated following the motion of the boston. Out of the various intake ports tested in this study the masked shroud head (MSH) generates the highest swirl while keeping satisfactory volumetric efficiency. The MSH port also produces high level of turbulence by shearing action between cylinder wall and swirl.

• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.5
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• pp.522-528
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• 2011

Artificial basilar membranes made of PVDF(polyvinylidene fluoride) are manufactured using microfabrication processes. The mechanical behavior of PVDF artificial basilar membrane was measured to evaluate its performance as a mechanical frequency analyzer using scanning LDV(laser Doppler vibrometer). The experimental setup consists of the microfabricated artificial basilar membrane, a loud speaker connected to an amplifier for generating acoustic pressure of specific spectral pattern, and a scanning LDV with controlling unit for measuring the displacement of the membrane on the incoming acoustic stimulation. The microfabricated artificial basilar membrane was attached tightly upon a package containing a chamber which can be filled with silicone oil before placed on the experimental setup stage. The experiment results showed that the microfabricated artificial basilar membrane has a property as a mechanical frequency analyzer.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.9
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• pp.5854-5860
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• 2014

The on-site performance of a vision-based displacement measurement system (VDMS) was evaluated through a field test on a bridge. The VDMS used in this study is composed of a camera, a marker, a frame grabber, and a laptop. The system measures the displacement by attaching a marker at the location to be measured on the structure, by capturing images of that marker with a fixed rate, and by processing a series of images using a planar homography technique. The developed system was first validated from a laboratory test using a small-scale building structure. The VDMS was then employed in a field test on a railroad bridge with a KTX train running under various conditions. The on-site performance was evaluated by comparing the obtained displacement using the VDMS with the displacement measured from a laser Doppler vibrometer (LDV), which is an expensive and accurate displacement measurement device.

• Journal of ILASS-Korea
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• v.21 no.4
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• pp.207-213
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• 2016

To protect air pollution of urban area from motor vehicles, emission limits for diesel vehicles have been dramatically lowered in short period. But recent studies have shown that on-road NOx emissions of light-duty diesel vehicles are considerably higher than the values measured with laboratory test procedures used for emission certification. To tackle with this issue, Ministry of Environment have a plan to introduce EU RDE-LDV (Real-driving Emission-Light-duty Vehicle) regulation. In this study, 4 Euro 6 diesel vehicles have been tested with the new test procedures published by EU to estimate on-road NOx emissions using PEMS (Portable Emission Measurement System). The results have shown that the requirements of EU RDE-LDV could be met in driving condition of metropolitan area for constitution of test routes and validity of test results. In analysing with Moving Averaging Window method the completeness and normality of test data were validated with the requirement. On-road NOx emissions were quite deviated as test vehicles and higher than the new limit of on-road NOx emission enforced from Sept. 2017, which means that RDE-LDV can effectively reduce NOx emission of diesel vehicles in real driving conditions of Korea.

• Journal of ILASS-Korea
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• v.5 no.1
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• pp.49-57
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• 2000

This study presents the flow visualization results, velocity and turbulence intensity measurements made within an air filter cover and entry region of a mass air flow sensor (MAFS) which is used in an induction system of 3.8L engine. Flow structure in two air filter cover assemblies were examined. The first was a clear plastic replica of the production cover while the second was a modified clear plastic cover with a geometry configured to reduce fluctuations. High speed flow visualization and laser doppler velocimetry (LDV) systems were used to reveal and analyze the flow field characteristics encountered in the sensor design process under steady flow conditions. A 40-watt copper vapor laser was used as a light source. Its beam is focused down to a sheet of light approximately 1.5mm thick. The light scattered off the particles was recorded by a 16mm high speed rotating prism camera at 5000 frames per second. A comparison of the flow patterns and LDV measurements in the original and modified air filter covers is presented to illustrate the controlling effect of the cover design on the turbulence structure formation near the bypass and on the sensor output signal. In both axial and radial planes of the main passage it was found that the turbulence flow pattern is remarkably influenced by the air filter cover and main passage configuration.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.2
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• pp.146-158
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• 1991

The flow around a two-dimensional foil section Is measured by a LDV(Laser Doppler Velocimetry) system which is capable of measuring the datailed flow field without interfering the original flow field. A 2-color 3-beam LDV system, which is capable of mea,;tiring 2 velocity components simultaneously and uses 2W Ar-Ion laser source, is used to measure the flow field around an NACA0012 foil section. The measured flow velocities are analysed iii order to study the boundary layer characteristics, flow separation and the detail structure of the flow near the trailing edge of the foil. The boundary layer characteristics are compared with the results by the head's momentum integral method. For the case of small angle of attack at relatively higher Reynolds number, both results show good agreements. The measured data of the velocity field around an NACA0012 foil section would be valuable data to validate the CFD(Computational Fluid Dynamic) calculation results. The developed experimental technique to evaluate the characteristics of two-dimensional foil sections is essential tool to develope new blade sections which have good lift characteristics and better cavitation performances.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.5
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• pp.66-73
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• 1994

The configuration effects of a tumble adaptor which transforms tumble into swirl on the intake tumble characterization under steady flow condition have been investigated by LDV measurement The following parameters were involved to test their effects on tumble-swirl conversion characteristics ; the cylinder height and its bottom shape, measuring position in the swirl induction pipe, and the relative direction of the induction pipe. The short cylinder height and the flat bottom of the tumble adaptor were found effective for the generation of tumble in the cylinder, allowing higher tumble-swirl conversion efficiency.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.4
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• pp.494-501
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• 2000

A study on performance of a propeller fan according to the distance between the front plate and the fan was conducted experimentally. Different characteristics of performance were found on the performance curve. Flow measurements using the three dimensional LDV system show that the zone of recirculation exists around the fan. The differences of performance in changes of the distance occurs because the zone of recirculation is much wider at the distance of 24mm than at that of 30mm.