• Journal of the korean Society of Automotive Engineers
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• v.9 no.3
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• pp.16-22
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• 1987

직접분사식 디젤기관의 성능과 배기가스 문제에 여향을 주는 실린더 내에서의 연소형태는 크게 연료분사계와 흡입공기 유동계 두 가지에 의해 결정된다. 즉 분사율, 부사시기, 분무형태와 같은 분사계의 특성과 공기선회, 스퀴시(squish), 난류와 같은 공기 유동 특성에 의하여 연소형태가 결 정된다. 이러한 복잡한 연소형테를 기관 특성에 맞게 조정한다는 것은 대단히 어려운 문제인데 이것은 연료화 공기의 혼합이 연소실형상과 흡기계의 형상에 큰 영향을 받으며 연료가 액체 상 태로 연소실내로 들어와 분무과정을 통하여 증발이 되어야만 연소가 가능하기 때문이다. 특히 흡입공기 유동계에 있어서 현재의 직접 분사식 대젤기관의 흡입구 형상은 흡입공기의 운동에너 지에 모멘트를 가하여 연소실내에서 공기의 선희(swirl)를 발생시켜 줌으로써 연료와 공기의 혼 합기를 형성시키는 Helical type이 많이 이용되고 있다. 그러나 기관 성능과 배기가스 특히 NOx는 상반관계를 이루기 때문에 연소실내로 들어오는 흡입공기의 선희강도(swirl ratio)를 너무 강하게만 한다고 하여 좋은 결과를 얻을 수는 없다. 따라서 설계하고자 하는 각 기관에 있어서 요구되는 성능과 배기가스 문제를 만족하는 흡입공기의 선희강도가 얻어질 수 있도록 흡입구 형상을 설계한다는 것은 많은 연구와 경험이 요구되고 있다. 본 자료에서는 직접분사식 디젤기 관에 있어서 흡입공기의 최적 선희강도에 대한 설정방법과 흡입구 형상 설계를 위한 설계 이론 및 정상류 Rig test상에서의 흡입공기 선희강도의 평가방법을 소개하고자 한다.

• Nuclear Engineering and Technology
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• v.48 no.2
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• pp.376-385
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• 2016

A hexagonally arrayed 37-pin wire-wrapped rod bundle has been chosen to provide the experimental data of the pressure loss and flow rate in subchannels for validating subchannel analysis codes for the sodium-cooled fast reactor core thermal/hydraulic design. The iso-kinetic sampling method has been adopted to measure the flow rate at subchannels, and newly designed sampling probes which preserve the flow area of subchannels have been devised. Experimental tests have been performed at 20-115% of the nominal flow rate and $60^{\circ}C$ (equivalent to Re ~ 37,100) at the inlet of the test rig. The pressure loss data in three measured subchannels were almost identical regardless of the subchannel locations. The flow rate at each type of subchannel was identified and the flow split factors were evaluated from the measured data. The predicted correlations and the computational fluid dynamics results agreed reasonably with the experimental data.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.242-247
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• 2004

In this study was proposed a transient response analysis technique of a rotor system, applying the generalized FE modeling method of a rotor-bearing system considering a base-transferred shock force and together the state-space Newmark method of direct time integration scheme based on the average velocity concept. Experiments were performed to a test rig of a mock-up rotor-bearing system with series of half-sine shock waves imposed by an electromagnetic shaker, and quantitative error analyses between analytical and experimental results were carried out. The transient reponses of the rotor were sensitive to duration times and shape-qualities of the shock waves, and overally the analytical results agreed quite well with the experimental ones. Particularly, in cases that the frequencies, $1/(2{\times}duration\;time)$, of the shock waves were close to the critical speed of the rotor-bearing system, resonances occurred and the transient responses of the rotor were amplified.

• Journal of the Korean Society for Heat Treatment
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• v.22 no.4
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• pp.203-209
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• 2009

Dual mass flywheel is the newly developed flywheel system which reduces the noise and vibration and make a better and comfortable ride of cars by adding inertia mass and damping device. However, verification of performance for this system should be carried out since this system is under developing status in our country. Especially, the durability for each part of this system should be guaranteed. Durable properties of driver plate which is the key component of dual mass flywheel were first investigated both in the raw (SCM435 in JIS) and heat-treated material. In addition, fatigue life analysis of driver plate was preformed in the real condition and the results were verified by comparison with the results of rig test.

• Journal of Drive and Control
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• v.12 no.3
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• pp.25-35
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• 2015

The hydraulic power-take-off mechanism (HPTO) is one of the most popular methods in wave energy converters (WECs). However, the conventional HPTO with only one direction motion has a number of drawbacks that limit its power capture capability. This paper proposes an adjustable moving angle wave energy converter (AMAWEC) and investigates the effect of the moving angle on the performance of the wave energy converter to find the optimal moving angle in order to increase the power capture capability as well as energy efficiency. A mathematical model of components from a floating buoy to a hydraulic motor was modeled. A small scale WEC test rig was fabricated to verify the power capture capability and efficiency of the proposed system through experiments.

• Journal of the Korean Society for Railway
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• v.10 no.3 s.40
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• pp.257-263
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• 2007

The critical speed above which the vehicle become unstable is one of the items that should be verified in the development of a new train. In the case of a high speed tilting train, which requires both higher critical speed and higher curving speed, the critical speed should be more carefully treated because the both requirements are in conflict with each other in the conventional train design. The main purpose of the present work is to estimate the linear and non-linear critical speeds of 200km/h Korean Tilting Train 'Hanbit200' under development. The newly developed self-steering mechanism was attached to the tilting train to ensure that the critical speed falls under the lower yaw stiffness which is needed to secure higher curving performance. The simulation for predicting the critical speed was done by a commercially available vehicle dynamics software. A full scale roller rig test was carried out to validate the numerical results and to verify the effectiveness of the self-steering mechanism.

• Journal of Magnetics
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• v.18 no.3
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• pp.302-307
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• 2013

Hybrid-type magnetic bearings using both permanent magnets and electromagnets have been used for rotating machinery. In the case of conventional thrust hybrid magnetic bearings supporting axial loads, radially magnetized permanent ring magnets, which have several demerits such as difficult magnetization and assembly, have been used to generate bias flux. In this study, a novel thrust hybrid magnetic bearing using an axially magnetized permanent ring magnet is presented. Because it is easy to magnetize a ring magnet in the axial direction, the segmentation of the ring magnet for magnetization is not required and the assembly process can be simplified. For verifying the performance of the proposed method, a test rig that consists of a proposed thrust magnetic bearing and variable loads is constructed. This paper presents the detailed design procedures and the obtained experimental results. The results show that the developed thrust magnetic bearing has the potential to replace conventional thrust magnetic bearings.

• Nuclear Engineering and Technology
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• v.53 no.10
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• pp.3196-3206
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• 2021

For the Korean design of the PCCS (passive containment cooling system) in an innovative PWR, the overall thermal resistance around a condenser tube is dominated by the heat transfer coefficient of steam condensation on the exterior surface. It has been reported, however, that the calculated heat transfer coefficients by thermal-hydraulic system codes were much lower than measured data in separate effect tests. In this study, a new empirical model of steam condensation in the presence of a noncondensable gas was implemented into the MARS-KS 1.4 code to replace the conventional Colburn-Hougen model. The selected correlation had been developed from condensation test data obtained at the JERICHO (JNU Experimental Rig for Investigation of Condensation Heat transfer On tube) facility, and considered the effect of the Grashof number for naturally circulating gas mixture and the curvature of the condenser tube. The modified MARS-KS code was applied to simulate the transient response of the containment equipped with the PCCS to the large-break loss-of-coolant accident. The heat removal performances of the PCCS and corresponding evolution of the containment pressure were compared to those calculated via the original model. Various thermal-hydraulic parameters associated with the natural circulation operation through the heat transport circuit were also investigated.

• Journal of Drive and Control
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• v.15 no.4
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• pp.17-22
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• 2018

Mobile hydraulics require higher energy efficiency, and a simpler as well as robust design, than general industrial hydraulics. The 6/3-way directional control valve is widely used as a mobile hydraulic control valve. However, since the 6/3-way directional control valve is a spool type valve, it is difficult to maintain the load. A counterbalance valve is typically used, to maintain the load, and lift down. However, in an industrial field using a mobile hydraulics device, a pilot controlled check valve may be used to implement holding and lifting operation of the self-weight load, and a relief valve may be used simply to exert back pressure. But no comparative analysis of advantages and disadvantages of each method was revealed. In this study, various methods of holding and unloading load with self-weight in mobile hydraulics are investigated, and compared through simulation using AMESim software. This is experimentally verified by using Festo's mobile hydraulic test rig TP800.

• Structural Engineering and Mechanics
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• v.69 no.4
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• pp.467-477
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• 2019

Digital image correlation (DIC) is now a popular and extensively used full-field metrology technique. In general, DIC is performed by using a turnkey solution offered by various manufacturers of DIC. In this paper, a simple and economical set-up for DIC is proposed which uses easily accessible digital single-lens reflex (DSLR) camera rather than industrial couple-charged device (CCD) cameras. The paper gives a description of aspects of carrying a DIC experiment which includes experimental set-up, specimen preparation, image acquisition and analysis. The details provided here will be helpful to carry DIC experiments without specialized DIC testing rig. To validate the responses obtained from proposed DIC set-up, tension and fatigue tests on specimens made of IS 2062 Gr. E300 steel are determined. Tensile parameters for a flat specimen and stress intensity factor for an eccentrically-loaded single edge notch tension specimen are evaluated from results of DIC experiment. Results obtained from proposed DIC experiments are compared with those obtained from conventional methods and are found to be in close agreement. It is also noted that the high resolution of DSLR allows the use of proposed approach for fracture characterization which could not be carried out with a typical turnkey DIC solution employing a camera of 2MP resolution.