• 설비공학논문집
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• 제22권2호
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• pp.70-77
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• 2010

In order to improve the efficiency of a main transformer in a train, the optimal operation of a cooling system is necessary. For the development of optimal control algorithms of a cooling system, mathematical models of a main transformer cooling system were developed. These include static and dynamic models of a main transformer, an oil pump, an oil cooler, and a blower. Static models were used to find optimal oil temperatures of the inlet and the outlet of a transformer. Dynamic models were used to predict transient performances of control algorithms of a blower and an oil pump. Simulation results showed good predictions of the static and the dynamic behavior of a main transformer cooling system. Therefore, mathematical models developed in this study may be effectively used for the development of control algorithms of a main transformer cooling system.

• Journal of Advanced Marine Engineering and Technology
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• 제24권1호
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• pp.134-141
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• 2000

In this study, a scaled model chamber was built to investigate ventilation characteristics of the Under floor Air-conditioning System. Experimental study was performed in model for cargo-oil pump room with inlet and outlet by visualization equipment with laser apparatus. Instant simultaneous velocity vectors at whole field were measured by 2-D PIV system(CACTUS'2000) which adopted two-frame grey-level cross correlation algorithm. The flow pattern reveals the large scale counterclockwise forced-vortex rotation from upside louver to lower scupper toward diagonal corner and also found small eddies at bottom layer

• 한국기계가공학회지
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• 제11권2호
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• pp.40-46
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• 2012

In this study, numerical analysis was conducted to understand the flow characteristics of lubrication system in a manual transmission installed in a commercial vehicle. Also, the analysis was conducted with the purpose of improving the heat and lubricative condition of the transmission. Discharging flow rates on each oil hole outlet according to various engine rotating speed and the length of oil hole branch was calculated. In conclusion, as engine rotating speed is high and the length of oil hole branch is long, the discharging flow rate is high by virtue of the centrifugal force. In addition, this study proposed data for optimal design of lubrication system in manual transmission for a commercial vehicle.

• Journal of Mechanical Science and Technology
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• 제20권10호
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• pp.1716-1721
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• 2006

The Lubrication Mode of line contacts between the vane and the camring in an oil hydraulic vane pump has been investigated. First, the variations of the radial force of a vane were calculated from previous measurements of dynamic internal pressure in four chambers surrounding a vane. Next, the lubrication modes were distinguished with Hooke's chart, which is an improvement over Johnson's chart. Finally, the influence of the boundary conditions in the lubrication region on the fluid film lubrication was examined by calculating the film pressure distributions. The results showed that the lubrication mode of the vane tip exists in the rigid-variable-viscosity region, and that discharge pressure higher than 7 MPa greatly affects the oil film pressure in the small and the large arc section because of the Piezo-viscous effect.

• Tribology and Lubricants
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• 제25권6호
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• pp.387-398
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• 2009

The operation condition of recently designed pistons for high power and high speed diesel engine become more severe due to the increment of combustion pressure and temperature. So, in order to overcome high temperature, the application of the mono-metal cast aluminum alloy piston featuring an enclosed cast-in open cooling gallery has increased. In this research, it is developed a PCJ (piston cooling jet) rig tester, described the test procedure and validated the performance of sample piston cooling gallery design. Then the test rig will be used for developing the design technology of piston cooling gallery. The test rig is composed with oil reservoir and pumping system, oil jet system, piston fixing and moving system, collecting oil measuring system, and data measuring and recording system. It will be measured collecting efficiencies under conditions of a few piston positions, oil jet pressures and oil viscosities for a piston cooling gallery. Furthermore, the PCJ rig tester will be used for the optimum design of the oil cooling gallery which being applied to increase the cooling efficiency of pistons in diesel engines satisfying the EURO V emission regulation and the more.

• Journal of Advanced Marine Engineering and Technology
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• 제36권5호
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• pp.609-617
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• 2012

The flow characteristics of polluted air are analysed by comparing the results obtained from PIV(Particle Image Velocimetry) experiment and CFD(Computational Fluid Dynamics) commercial code. In order to simulate the polluted air flow, the olive oil has been used as tracer particles with the kinematic viscosity of air, $1.51{\times}10^{-5}m^2/s$. The investigation has done in the range of Reynolds numbers of 870, 1730 and 2890 due to the inlet flow velocities of 0.3, 0.6, and 1.0 m/s, respectively. The average velocity and the pressure distributions are comparatively discussed with respect to the three different Reynolds numbers. The results show that the outlet flow rates at three different Reynolds numbers are equivalent of 165 to 167 percent of the inlet ones. The pressure drop occurs in the model closed at both end sides and the highest pressures at each Reynolds number are positioned at the top of the tunnel between the inlet and outlet.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.961-966
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• 2009

This paper presents precise temperature control of oil outlet in an oil cooler with hot-gas bypass control as an industrial refrigerator. The control system was designed for obtaining precise temperature control performance even though abrupt disturbances based on flow rate control of hot-gas bypass. PID controller was adopted in feedback control system. We showed that the gain of PID could be easily determined by using gain-tuning methods without any numerical model. Through some experiments, excellent control performances such as overshoot within 1.7%, steady state temperature error within ${\pm}0.1^{\circ}C$ were established by a simple PI controller. We expect that the system can control the target temperature within error of $0.33^{\circ}C$ under abrupt disturbances.

• 융합신호처리학회논문지
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• 제14권2호
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• pp.130-135
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• 2013

최근 공작기계 분야에서 가공속도와 가공정밀도 같은 시스템 성능이 한층 요구되고 있다. 특히 가공속도가 증가함에 따라 공작기계와 수가공 분야의 공작물 가공 부위에 유해한 열 발생을 초래하게 된다. 이 열은 가공 정밀도를 저하시키는 주된 원인으로 작용한다. 따라서 온도를 제어하는 오일쿨러는 공작기계에서 필수적이다. 일반적으로 두 가지 대표적인 제어기법인 핫가스 바이패스 방식과 압축기 가변속 제어 방식이 오일쿨러에 채택 되었다. 본 논문에서는 오일 출구 온도를 설정값으로 유지하기 위해 압축기의 속도를 제어하였다. 공작기계의 정밀 가공이 요구되는 추세에 맞추어 ${\pm}0.1^{\circ}C$의 고정도 온도 제어가 가능한 오일쿨러가 요구된다. 그러나 정밀 온도제어가 가능한 오일쿨러는 가격이 고가이다. 그러므로 본 논문에서는 on/off(릴레이) 제어방식 대신에 PID 제어기와 위상각 전력제어 방식을 사용하여 정밀 온도제어가 가능한 오일쿨러용 제어기를 제안한다. 제안한 제어기를 제작하고, $23^{\circ}C$, $24^{\circ}C$ 그리고 $25^{\circ}C$에서 실험하였다.

• 해양환경안전학회지
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• 제23권5호
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• pp.541-548
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• 2017

본 연구에서는 해양플랜트설비 건조 현장에서 사용되고 있는 기존 고온 오일 플러싱 장비에 대한 성능개선을 위해 기존의 플러싱 장치에 사용되던 오일에 질소가스를 혼합한 고온 오일 플러싱 시스템에 대하여 국제표준화기구 코드(ISO code)를 기준으로 이론적 연구를 수행하였다. 연구를 위해 오일-질소가스 혼합유체 플러싱 시스템 공정을 설계 후 청정성능에 영향을 주는 혼합유체의 혼합비율, 온도, 레이놀즈수 및 액상분율 등에 대한 공정모사 결과도 분석하였다. 그 결과 관 직경과 가스상의 체적분률이 일정한 상태에서 혼합유체의 체적유량이 증가될수록 수평 유압배관 입출구의 액상분율 차이 ${\Delta}{\alpha}_L$ 값은 증가하게 되고 배관길이 방향의 위치에 따라 오일과 질소가스 기포 사이의 상분포가 달라짐을 확인했다. 이러한 상분포의 변화는 오일-질소가스 혼합유체 플러싱 시스템의 청정성능에도 커다란 영향을 줄 것으로 예상된다.

• Korean Chemical Engineering Research
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• 제55권2호
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• pp.201-213
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• 2017

물이 포함된 원유는 oil separator 를 거쳐 물이 제거된다. 본 연구의 목적은 공기-물-기름 3상 혼합물에 대한 3차원 oil separator 의 분리성능을 예측하기 위하여 Eulerian 전산유체역학(CFD: computational fluid dynamics) 모델을 개발하는 것이다. 비압축성, 등온, 비정상상태 CFD 모델식은 공기상을 연속상으로, 물과 기름상을 분산상으로 정의하며, 운동량 보존식은 항력(drag force), 양력(lift force), 다공성매체 저항력을 포함한다. 또한, 난류현상으로 standard k-${\varepsilon}$ 모델이 이용된다. 물과 기름 출구압은 oil separator 의 액위를 결정하는 중요한 인자이며, 정상운전상태 액위 25 cm를 맞추기 위하여 측정압은 각각 6.3 kPa, 5.1 kPa으로 결정되었다. 시간에 따른 공기, 물, 기름의 부피분율의 변화를 조사하였고, 정상상태에 도달하였을 때, 물과 기름상의 침강속도를 oil separator의 종축 길이에 따라 분석하였다. 본 연구에서 제시된 CFD 모델로부터 얻은 oil separator의 기름분리성능은 99.85%이며, 실험값과 거의 일치하였다. 비교적 단순한이 CFD 모델은향후 oil separator의구조를 변경하거나, 최적운전조건을 찾기위하여 유용하게사용될수있을 것이다.