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세라믹 볼 축열체를 이용한 순산소 축열연소시스템에 대한 실험적 연구
홍성국,노동순,이은경,Hong, Sung Kook,Noh, Dong Soon,Lee, Eun Kyung 한국에너지학회 2013 에너지공학 Vol.22 No.2
An experimental study has been conducted for the design of the regenerative oxy-fuel combustion system with ceramic ball. Various design parameters are considered such as ball size, regenerator weight, and combustion load. Regenerative system with a pair of oxygen burners and regenerators is set up and the temperature of oxygen and exhaust gas passing through ball regenerator is measured. It is shown that the temperature distributions with time are affected by ball diameter and regenerator weight, and the significant temperature change is observed by combustion load. As the ball size decreases and the regenerator weight increases, the regenerating temperature efficiency increases. It is found that the heat recovery ratio is low despites of high regeneration temperature efficiency. 순산소 축열연소시스템에서 세라믹 볼 축열체 적용에 따른 축열/재생 특성에 관한 실험적 연구를 수행하였다. 설계인자인 볼 직경, 축열체 무게, 연소부하 변동에 따른 축열/재생 특성을 살펴보았다. 양방향 순산소 축열연소시스템 장치를 구성하여 축열체를 통과하는 배가스 및 산소의 온도를 측정하였다. 실험결과, 볼 직경과 축열체 무게 변동에 따라 배가스 및 산소 온도분포의 변화가 나타났으며, 연소부하 변동시 상대적으로 큰 온도분포의 변화가 측정되었다. 볼 직경이 작아지고 축열체 무게가 증가될수록 측정된 재생온도효율은 증가되었다. 한편, 높은 재생온도효율에 비해 열 회수율은 낮게 예측되어 열 회수율을 향상시키기 위해 축열구조 설계 최적화가 필요함을 확인하였다.
가스터빈 연소실 냉각을 위한 충돌제트 / 유출냉각기법에서 사각핀 설치에 따른 열/물질전달 특성
홍성국(Sung Kook Hong),이동호(Dong-Ho Rhee),조형희(Hyung Hee Cho) 한국유체기계학회 2004 유체기계 연구개발 발표회 논문집 Vol.- No.-
The present study has been performed to investigate the influences of rectangular fins on heat transfer in an impingement/effusion cooling system with crossflow. To simulate the impingement / effusion cooling system with initial crossflow, two perforated plates are placed in parallel and staggered arrangements with a gap distance of 2 times of the hole diameter. The crossflow passes between the plates, and various rectangular fins are installed on the plates. Reynolds number based on the hole diameter is fixed to 10,000 and the flow rate of crossflow is changed from 0.5 to 1.5 times of that of the impinging jet. A naphthalene sublimation method is used to obtain the heat/mass transfer coefficients on the effusion plate. Also to analyze the flow characteristics, a numerical calculation is performed. When rectangular fins are installed, the flow and heat transfer pattern is changed greatly from case without fins. In the injection hole region, the jet impinges on effusion plate without deflection and wall jet spreads symmetrically. In the effusion region, the crossflow accelerates due to the decrease of cross-sectional area in the channel. Local heat/mass transfer coefficients are enhanced significantly compared to case without fins. As the blowing ratio increases, the effect of fins against the crossflow becomes more significant and then the higher average heat/mass transfer coefficients are obtained than the case without fins.
분사홀에 설치된 turbulator에 따른 충돌/유출면에서의 열/물질전달 특성
홍성국(Sung Kook Hong),이동현(Dong Hyun Lee),김영도(Young Do Kim),조형희(Hyung Hee Cho) 한국유체기계학회 2007 유체기계 연구개발 발표회 논문집 Vol.- No.-
In order to enhance the heat/mass transfer, a turbulator has been installed at the exit of injection hole for the impingement/effusion cooling system The local heat/mass transfer coefficients have been obtained by a naphthalene sublimation method. Experiments have been carried out at the fixed jet Reynolds number of 10,000. Two turbulators with different diameter have been used in the present study. The result presents that the turbulator leads to the increase in flow mixing and jet velocity, consequently enhancing the heat/mass transfer at a stagnation region. Further, the stagnation region is divided into four small areas with peak value. In the existence of initial crossflow, the stagnation regions move downstream and low heat/mass transfer regions are formed regardless of the installation of turbulator. However, the increased jet velocity by turbulator reduces the crossflow effect against the jet, resulting in decrease of low heat/mass transfer regions. With respect to averaged Sh value, the installation of turbulator yields 5~10% augmentation compared to the case without turbulator.
경사제트에 따른 충돌제트 / 유출냉각에서 열 / 물질전달 특성
홍성국(Sung Kook Hong),이동호(Dong-Ho Rhee),조영희(Hyung Hee Cho) 대한기계학회 2008 大韓機械學會論文集B Vol.32 No.4
An experimental investigation was conducted to investigate the heat/mass transfer for impingement/effusion cooling system with inclined jet. Jets with inclined angle of 60 are applied to impingement/effusion cooling. At the jet Reynolds number of 10,000, the experiments were carried out for blowing ratios ranging from 0.0 to 1.5. The local heat/mass transfer coefficients on the effusion plate are measured using a naphthalene sublimation method. The result indicates that the inclined jet causes the non-uniform and low heat/mass transfer compared to the vertical jet. At stagnation region, the peak position is shifted from the geometrical center of injection hole due to Coanda effect and its level is higher than that of vertical jet due to increase in turbulence intensity by steep velocity gradient near the stagnation region. Further, the secondary peak region disappears because the interaction between adjacent wall jets weakens. When the initial crossflow occurs, the distorted heat/mass transfer pattern appears. As the blowing ratio (crossflow rate) increases, the heat/mass transfer distributions become similar to those of the vertical jet. This is because the effect of crossflow is dominant compared to that of inclined jet under high blowing ratio (M≥1.0). At low blowing ratio (M≤0.5), averaged Sh value is 10% lower than that of vertical jet, whereas its value at high blowing ratio (M≥1.0) is similar to that of vertical jet.
40mm 고속유탄의 품질보증 향상을 위한 K4 기관총의 Action Time 계측시스템 개발에 관한 연구
홍성국(Hong, Sung-Kook),신준구(Shin, Jun-Goo),전혜진(Jeon, Hye-Jin),김용화(Kim, Yong-Hwa),주진천(Ju, Jin-Chun),권인규(Kwon, In-Gyu) 한국산학기술학회 2015 한국산학기술학회논문지 Vol.16 No.7
Action Time이란 탄이 공이가 뇌관을 격발한 순간부터 총구를 이탈할 때까지의 걸리는 시간을 말한다. 40mm 고속유 탄은 장전되면서 격발되는 구조이므로 Action Time이 특정 시간 이내여야 탄피 고착과 같은 악작용을 방지 할 수 있다. 기존 40mm 고속유탄의 Action Time 계측은 신뢰성 있는 측정 장비의 부재로, 그동안 Action Time이 K4기관총 품질 보증에 적용 되는 것에 어려움이 있었다. 본 연구에서는 다양한 센서 간 비교와 별도의 발사 장치 고안을 통해 정확한 Action Time을 측정하고자 하였다. 이 장치에서는 공이 부분에 설치된 광센서의 신호와 총열 부분에 설치된 와전류 탐촉자 신호 간 간격이 계측되고, 실시간으로 컴퓨터로 데이터가 전송되게 된다. 계측된 Action Time 결과가 시스템 요구 성능에 충족하는지 여부를 즉시 확인함으로써 40mm 고속유탄의 품질 보증에 중요한 역할을 할 것으로 기대된다. From the moment that a firing pin triggers the detonator to the moment that a grenade leaves a barrel is called Action Time. Since a loading and percussion of 40mm grenade happens simultaneously, action time should be within a certain time in order to prevent a Jamming malfunction. Previously, unreliable action time device of 40mm grenade made it difficult to improve quality assurance of K4 Grenade Machine Gun. Here, various sensors were compared and a special device was designed to seek an accurate measurement on action time. In this device, the gap between a signal from an optical sensor in Firing Pin and that from Eddy current probe in the barrel was recorded and data were sent to a computer in real time. Confirming if action time is within the criteria, it is expected that action time plays an important role in quality assurance on 40mm grenade.
충돌제트/유출냉각기법에서 회전효과에 의한 열/물질전달 특성
홍성국(Sung Kook Hong),조형희(Hyung Hee Cho) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
The purpose of this study is to investigate the effect of rotation on heat/mass transfer in an impingement/effusion cooling system. To simulate the rotating impingement/effusion system, the test duct with 16 injection holes and 8 effusion holes is installed on the rotating system. Jet Reynolds number based on the hole diameter is fixed to 3,000 and Rotation number is set to 0.032. A naphthalene sublimation method is used to obtain the heat/mass transfer coefficients on the effusion plate. The local distributions of heat/mass transfer coefficient are significantly changed due to the rotation. In the impingement/effusion cases with ±90 stagger angle, low and non-uniform heat/mass transfer distributions occur because the impinging jet is deflected by Coriolis force. It is confirmed that the averaged heat/mass transfer value of impingement/effusion is higher than that of array jet in both the rotating and the stationary conditions.