• Journal of Advanced Marine Engineering and Technology
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• 제33권7호
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• pp.1003-1011
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• 2009

This study aims at precise control of oil outlet temperature in the oil cooler system of machine tools for enhancement of working speed and processing accuracy. PID control logic is adopted to obtain desired oil outlet temperature of the oil cooler system with hot-gas bypass method. We showed that the gains of PID controller could be easily determined by using gain tuning methods to get the gain of PID controller without any mathematical model. We also investigated various gain tuning methods to design the gains of PID and compared each control performance for selecting the optimal tuning method on the hot gas bypass method through experiments. Moreover, we confirmed excellent control performance with proposed PI controller gain even though disturbances were abruptly added to the experimental system.

• Journal of Chest Surgery
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• 제36권11호
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• pp.834-838
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• 2003

배경: 개심술 후 공기 제거는 매우 중요한 시술이다. 그러나, 심장 내의 공기 분포, 시술로 인한 합병증, 심폐바이패스의 시간 연장으로 여전히 제한적이다. 인위적으로 동정맥루를 만들어 공기를 제거하고 그 효과를 경식도초음파로 확인하였다. 대상 및 방법: 심폐바이패스 완료 직전에 압력표준변환선을 동맥과 정맥회로에 설치해둔 마개에 연결하면 동맥과 정맥사이에 작은 동정맥루가 형성된다. 심장 내의 공기정도와 공기제거시간은 경식도 초음파와 압력표준변환선으로 확인하였다. 결과: 간단한 방법으로 심폐바이패스의 시간단축, 수분 내에 공기가 제거되는 것을 경식도초음파로 확인하였다. 결론: 동맥과 정맥 사이에 작은 연결관으로 동정 맥루를 만드는 것은 매우 간단하며 개심술 후 공기 제거와 공기색전증 예방에 효과적인 방법이다.

• 설비공학논문집
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• 제24권1호
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• pp.1-8
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• 2012

Recently, the needs of system performances such as working speed and processing accuracy in machine tools have been increased. Especially, the speed increment generates harmful heat at both moving part of the machine tools and handicrafts. The heat is a main drawback to progress accuracy of the processing. Hence, a cooler system to control temperature is inevitable for the machine tools. In general, two representative control schemes, hot-gas bypass and variable speed control of a compressor, have been adopted in the water cooler system. In this paper, comparisons of system performances according to the control schemes in a cooler for machine tools were conducted in detail. Each proportional-integral feedback controller for the two different control systems is designed. The system performances, especially the temperature control accuracy and coefficient of performance which is a criterion of energy saving, were mainly analyzed through various experiments using 1RT water cooler system with different two types of control scheme. These evaluations will provide useful information to choose suitable water cooler system for the engineers who design controllers of the cooler system for machine tools.

• 한국추진공학회지
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• 제23권5호
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• pp.1-9
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• 2019

마이크로 터보제트 엔진을 사용하여 바이패스비에 따른 배기가스의 적외선 신호와 온도분포 측정 연구를 수행하였다. 본 연구에서는 마이크로 터보제트 엔진을 바이패스 공기를 공급하여 터보팬 엔진의 유동을 모사할 수 있도록 개조하였다. 마이크로 터보제트 엔진으로 코어 유동을 모사하고 고압의 압축 공기를 마이크로 터보제트 엔진의 외부덕트에 공급하여 바이패스 유동을 모사하였다. 바이패스비 0.5, 1.0, 1.4 의 3가지 조건에서 실험을 수행하였다. 그 결과 적외선 신호는 바이패스비가 증가할수록 점차 감소함을 보여주었다. 그리고 배기가스 온도는 바이패스비가 증가할수록 감소됨을 알 수 있었다. 또한 배기가스에 대한 쉴리렌 가시화 측정을 수행하였다. 배기가스의 온도분포와 쉴리렌 유동 가시화로부터 바이패스비에 따른 배기가스의 제트유동구조를 이해할 수 있다.

• Nuclear Engineering and Technology
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• 제45권6호
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• pp.745-752
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• 2013

For thermo-fluid and safety analyses of a High Temperature Gas-cooled Reactor (HTGR), intensive efforts are in progress in the developments of the GAMMA+ code of Korea Atomic Energy Research Institute (KAERI) and the AGREE code of the University of Michigan (U of M). One of the important requirements for GAMMA+ and AGREE is an accurate modeling capability of a bypass flow in a prismatic core. Recently, a series of air experiments were performed at Seoul National University (SNU) in order to understand bypass flow behavior and generate an experimental database for the validation of computer codes. The main objective of the present work is to validate the GAMMA+ and AGREE codes using the experimental data published by SNU. The numerical results of the two codes were compared with the measured data. A good agreement was found between the calculations and the measurement. It was concluded that GAMMA+ and AGREE can reliably simulate the bypass flow behavior in a prismatic core.

• International Journal of Aeronautical and Space Sciences
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• 제15권1호
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• pp.97-101
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• 2014

With the increase in global air travel, aircraft noise has become a major public issue. In modern aircraft engines, only a small proportion of the air that passes through the whole engine actually goes through the core of the engine, the rest passes around it down the bypass duct. A successful method of reducing noise further, even in ultra-high bypass ratio engines, is to absorb the sound created within the engine. Acoustically absorbent material or acoustic liners have desirable acoustic attenuation properties and thus are commonly used to reduce noise in jet engines. The liners typically are placed upstream and downstream of the rotors (fans) to absorb sound before it propagates out of the inlet and exhaust ducts. Noise attenuation can be dramatically improved by increasing the area over which a noise reducing material is applied and by placing the material closer to the noise source. In this paper we will briefly discuss acoustic liner applications in modern turbofan engines.

• Journal of Advanced Marine Engineering and Technology
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• 제38권9호
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• pp.1021-1026
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• 2014

본 논문에서는 hot-gas를 이용한 다양한 바이패스 제어 방식 중에서 증발기 흡입부 방식에 대해 각각의 성능에 영향을 미치는 외기온도, 출수온도, 과열 및 과냉도 등에 대해서 알아보았다. 그 주요 결과를 요약하면 다음과 같다. 우선, 증발기 흡입부로 hot-gas를 바이패스 하였을 경우에 냉동장치의 성능은 외기온도, 출수온도, 과열 및 과냉도 등에 영향을 받는 것을 알 수 있었다. 따라서 이러한 변수에 대한 최적화를 통해 본 냉동장치의 기초 설계 자료를 제공할 수 있다. 그리고 증발기 흡입부 hot-gas 바이패스 방식의 운전특성을 고찰하여 본 논문에서 제안하는 냉동장치에 대한 적용 가능성을 확인할 수 있었다.

• 동력기계공학회지
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• 제18권5호
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• pp.48-54
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• 2014

In this paper, three refrigeration systems bypassing hot-gas to compressor outlet, compressor and condenser outlet and evaporator inlet are theoretically compared to offer basic design data for performance depending on cooling load using a HYSYS program. The main results are summarized as follows : First, the COP of third system is the highest. Next, the COP of second system is higher than first one. And, the temperature of compressor inlet of third system is constant for all cooling load. Compared to first and second system, the compressor inlet temperature of the first system is higher than second one for all cooling loads. From the above results, third system, which is bypassing hot-gas to evaporator inlet, is more advantageous when considering the precise temperature control and excellent performance of oil and water cooler of industrial machine.

• 한국자동차공학회논문집
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• 제12권6호
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• pp.38-45
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• 2004

This paper studies the effects of intake port configuration on the swirl that is key parameter in the flow field of direct injection diesel engines. In-cylinder flow characteristics is known to have significant effects on fuel air mixing, combustion and emissions. To investigate the swirl flow generated by various intake ports, steady state flow tests were conducted to evaluate the swirl. Helical port geometry, SCV shape and bypass were selected as the design parameters to increase the swirl flow and parametric study was performed to choose the optimal port shape that would generate a high swirl ratio efficiently. The results revealed that a key factor in generating a high swirl ratio was to suitably control the direction of the intake air flow passing through the valve seat. For these purposes, we changed the distance of helical and tangential port as well as installed bypass near the valve seat and the effects of intake port geometry on in-cylinder flow field were visualized by a laser sheet visualization method. From the experimental results, we found that the swirl ratio and mass flow rate had a trade off relation. In addition, the result indicates that the bypass is a effective method to increase the swirl ratio without sacrificing mass flow rate.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2003년도 제21회 추계학술대회 논문집
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• pp.211-214
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• 2003

바이패스 덕트 손실을 고려한 비행 중의 복축 혼합형 터보팬 엔진의 윈드밀 성능을 예측하기 위해, 본 연구에서는 원심 및 축류 압축기, 축류 터빈의 윈드밀 작동 과정과 물리적 현상을 규명하고 바이패스 덕트를 통과한 공기와의 혼합 현상을 해석하였다. 윈드밀 성능 예측의 결과는 유차원 해석을 통해 비교 분석하였다.