• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.12
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• pp.1917-1923
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• 2010

This study focuses on model identification and a 2-DOF PID control algorithm for cooling processes; a pneumatic butterfly-type control valve is used for this purpose. The mathematical model is a transfer function composed of a time delay and a second-order delay system. The control valve is identified as a first-order delay system with a time delay and included in the controlled plant. From the experimental data sets for a demo plant, the model parameters are identified, and the 2-DOF PID control gains are analytically derived by Kitamori's method. We show via a computer simulation and an experimental test that the performance of the proposed 2-DOF PID control system is better than that of a conventional 1-DOF PID control system.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.381-386
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• 2007

Jet-A spray, evaporation and combustion were numerically analyzed in annular type model combustor using KIVA-3V. Liquid fuel's atomizing was affected by flow field near droplet. When cooling flow was not optimized, SMD was increased, and equivalence ratio was horizontally distributed in combustor's downstream. Flame spread out horizontally and separated in combustors downstream. Flame center was separated by cooling flow. Flame separation made local high temperature in downstream that caused NO increase.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.4
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• pp.164-172
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• 2020

The fuel oil/heat exchanger installed in military aircraft is a device that cools the lubricant oil supplied to other devices, such as an AMAD, and a hydraulic pump using the low temperature of the fuel is cracked at the AMAD lubricant inlet port. If a crack in the heat exchanger occurs, the lubricant oil supplied to other equipment is not cooled. Therefore, the flight can no longer be performed. In this study, non-destructive inspection and microscopic examination of the fracture surface of the oil port were performed to analyze the crack tendency. The oil pipe connected to the oil port is a titanium pipe, which is fastened with over torque and has been identified as the leading cause of heat exchanger oil port cracks. In addition, it was verified as the main reason for cracking by finite element analysis. The material and diameter of the pipe were changed to improve this defect, and the applied torque was adjusted. In addition, the bending value of the pipe was adjusted to minimize the fatigue accumulation due to pulsating pressure. As a result, no cracks occurred on the heat exchanger via the ground test after the installation of an improved pipe under the same conditions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.5
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• pp.373-382
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• 2013

In this paper, in order to analyze the performance of a decoy system for ship defense against an anti-ship missile(ASM) with an infrared image(IIR) seeker, the modeling and engagement simulation program is introduced. The IIR seeker on the ASM detects the infrared signal of ship from a distance and approaches the ship based on proportional navigation guidance(PNG) or impact angle control guidance(IACG). Hence the guidance performance of the ASM is basically depend on the target tracking algorithm of the seeker as well as the infrared signal of the ship. Using the developed program, we can investigate the effect of the ship decoy system such as flares and surface cooling system of the ship with respect to various kinds of tracking algorithms of the IIR seeker of the ASM.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.119-119
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• 2013

5년 동안 진행된 고진공 펌프 개발 사업의 일환으로 맥동관형 냉동기에 활성탄 어레이를 장착한 흡기구 직경 14인치 국산 크라이오펌프 완제품이 만들어졌다. 이미 지난해에 완성한 시제품을 가지고 모든 배기성능시험을 완료하고 목표를 뛰어 넘는 성능을 가지고 있음을 입증하였지만 완제품의 경우는 현장에서 스퍼터링 공정에 대한 신뢰성과 열적 내구성 시험이 중요한 항목으로 대두되었다. 개발된 펌프를 생산 공정에 직접 투입하는 모험을 하지 않으면서도 신뢰성을 확보하는 방편으로 카이스트 나노종합팹 센터에서 가동중인 스퍼터링 장비에 완제품을 달고 기존 공정과 같은 방식으로 장치를 운영하면서 외제 상용품을 사용했을 때와 진공성능 및 공정수율을 비교하는 시험을 수행하였다. 또 내구성 시험 항목으로 열부하 시험과 열 사이클 시험을 수행하였다. 열부하 시험은 300도까지 온도를 올릴 수 있는 열판을 펌프 흡기구 배플 앞에 설치하여, 냉동기 2차 냉각단 온도가 20 K 이하로 유지될 수 있는 최대 허용 복사열을 측정하는 방식으로 진행되었으며 열 사이클 시험은 크라이오 펌프의 활성화 기능을 활용하여 완전 활성화(full regen., 10K-300K-10K) 과정을 10회 연속 시행하여 펌프의 배기성능과 기계적 이상 유무를 관찰하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.10
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• pp.1001-1009
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• 2012

In this study, the cooling characteristics of combustion gas were investigated by injecting liquid nitrogen ($LN_2$) into a liquid rocket combustion chamber, which uses liquid oxygen (Lox) and kerosene as propellants. $LN_2$ injectors and an extended chamber for mixing were installed at the end of the ordinary LRE combustion chamber, and a nozzle was installed after the chamber for mixing. First, an ignition test of the liquid rocket engine was conducted to verify the stable combustion process. Next, a hot firing test was performed step-by-step for safety. Finally, the test was performed for 20 s. The results showed that the combustion gas of the LRE could be successfully cooled by using $LN_2$.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.5
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• pp.467-474
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• 2004

This paper presents the results of an experimental investigation for the effect of radiant heat on the evaporation cooling of water droplet in the process of fire extinguishing. The experiments are mainly focused on the surface temperature, the surface roughness and the droplet diameter. The range of surface temperature is T$_{s}$ =80－14$0^{\circ}C$, surface roughness is R$_{a}$=0.08－0.64 ${\mu}{\textrm}{m}$ and the droplet diameter is $\Phi$=3.0 mm in the radiation. The results show that the evaporation time is shorter for the larger surface roughness and the volume of droplet increased when the surface roughness is 0.64 ${\mu}{\textrm}{m}$ at the surface temperature 127$^{\circ}C$. When the surface roughness is 0.64 ${\mu}{\textrm}{m}$, the heat flux is larger than the surface roughness is 0.08 ${\mu}{\textrm}{m}$ at the surface temperature 81$^{\circ}C$.>.>.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.64 no.4
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• pp.236-240
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• 2015

Natural ester has a higher biodegradability, flash and fire points, and a greater permittivity compared to conventional mineral oils. However, natural ester also has a higher pour point, viscosity, and water content. These characteristics hamper circulation and the electrical properties of oil-filled transformer. Thus, this paper applied electromagnetic-thermal-flow coupled analysis method to predict temperature distribution inside 154kV single phase power transformer using natural ester. It modeled in the actual appearance for the tank and winding of the power transformer to improve the accuracy of analysis and applied heat flow analysis that considered hydromechanics and heat transfer at the same time. It calculated the power loss, the main cause of temperature rise, from winding and core with electromagnetic analysis then used for the heat source for the heat flow analysis. It then compared the reasonability of result of measurement analysis based on the result acquired from temperature rise test using FBG sensor on the power transformer.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.5
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• pp.465-471
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• 2013

A steam generator in nuclear power plant is a heatexchager which is used to convert water into steam from heat produced in a nuclear reactor core, and the steam produced in steam generator is delivered to the turbine to generate electricity. Because of damage to steam generator tubing may impair its ability to adequately perform required safety functions in terms of both structural integrity and leakage integrity, eddy current testing is periodically performed to evaluate the integrity of tubes in steam generator. This assessment is normally performed during a reactor refueling outage. Currently, the eddy current testing for steam generator of nuclear power plant in Korea is performed in accordance with KEPIC & ASME Code requirements, the eddy current testing system is consists of remote data acquisition unit and data analysis program to evaluate the acquired data. The KEPIC & ASME Code require that the electrical properties of remote data acquisition unit, such as total harmonic distortion, input & output impedance, amplifier linearity & stability, phase linearity, bandwidth & demodulation filter response, analog-to-digital conversion, and channel crosstalk shall be measured in accordance with the KEPIC & ASME Code requirements. In this paper, the measurement requirements of electrical properties for eddy current testing instrument described in KEPIC & ASME Code are presented, and the measurement results of newly developed eddy current testing instrument by KHNP(Korea Hydro & Nuclear Power Co., LTD) are presented.

• Membrane Journal
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• v.20 no.2
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• pp.127-134
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• 2010

This study is conducted about the system that reduces organism after fermenting food waste from a food waste disposal equipment, divides gas made when food waste is fermented into gas and water, and then sends gas to a reactor again, condenses water, and apply it to the MBR system with submerged MF hollow fiber membranes. A submerged MF hollow fiber membrane module was installed to a food waste disposal equipment and a water treatment system made by Bio Hitech Co,. Ltd. to process food waste generated from a staff cafeteria in a H institute for 90 days. For initial seeding of a food waste disposal equipment, 305 kg of rice bran, chaff, and sawdust as well as 1,648 kg of food were input during the operation, and 1,600 L of condensed wastewater occurred. Fermented by-product after finishing running a food waste disposal equipment was 386 kg and its reduction was shown to be 80%. The organism was processed by applying submerged MF hollow fiber membrane module to the MBR system of condensed wastewater, and the result shows reduction rates were BOD 99.9%, COD 97.5%, SS 98.6%, T-N 54.6% and T-P 34.7% and the total colon bacillus was perfectly eliminated.