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정사각 막냉각홀 내부에서의 열/물질전달 및 유동 특성 (II) - 비대칭 입구조건 효과 -
이동호,강승구,조형희,Rhee, Dong-Ho,Kang, Seung-Goo,Cho, Hyung-Hee 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.7
An experimental study has been conducted to investigate the heat/mass transfer characteristics within a square film cooling hole with asymmetric inlet now condition. The asymmetric inlet now condition is achieved by making distances between side walls of the secondary now duct and the film cooling hole different; one side wall is $2D_h$ apart from the center of the film cooling hole, while the other side wall is $1.5D_h$ apart from the center of the film cooling hole. The heat/mass transfer experiments for this study have been performed using a naphthalene sublimation method and the now field has been analyzed by numerical calculation using a commercial code. Swirl now is generated at the inlet region and the heat/mass transfer pattem with the asymmetric inlet now condition is changed significantly from that with the symmetric condition. In the exit region, the effect of mainstream on the inside hole now is reduced with the asymmetric condition. The average heat/mass transfer coefficient is higher than that with the symmetric condition due to the swirl now generated by the asymmetric inlet condition.
연소실 냉각을 위한 충돌제트/유출냉각기법에서 유출판에서의 열전달특성
이동호,조형희,Rhee, Dong-Ho,Cho, Hyung-Hee 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.3
The present study is conducted to investigate the local heat/mass transfer characteristics for flow through perforated plates. A naphthalene sublimation method is employed to determine the local heat/mass transfer coefficients on the effusion plate. Two parallel perforated plates are arranged for the two different ways: staggered and shifted in one direction. The experiments are conducted for hole pitch-to-diameter ratios of 6.0, for gap distance between the perforated plates of 0.33 to 10 hole diameters, and for Reynolds numbers of 5,000 to 12,000. The result shows that the high transfer region is formed at stagnation region and at the mid-line of the adjacent impinging jets due to secondary vortices and flow acceleration to the effusion hole. For flows through the perforated plates, the mass transfer rates on the surface of the effusion plate are about six to ten times higher than for effusion cooling alone (single perforated plate). More uniform and higher heat/mass transfer characteristic is obtained in overall region with small gap between two perforated plates.
변형된 단일 막냉각홀 주위에서의 열/물질전달 및 막냉각효율 특성
이동호,김병기,조형희,Rhee, Dong Ho,Kim, Byunggi,Cho, Hyung-Hee 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.5
Two problems with jet injection through the cylindrical film cooling hole are 1) penetration of jet into mainstream rather than covering the surface at high blowing rates and 2) nonuniformity of the film cooling effectiveness in the lateral direction. Compound angle injection is employed to reduce those two problems. Compound angle injection increases the film cooling effectiveness and spreads more widely. However, there is still lift off at high blowing rates. Shaped film cooling hole is a possible means to reduce those two problems. Film cooling with the shaped hole is investigated in this study experimentally. Film cooling hole used in present study is a shaped hole with conically enlarged exit and Inlet-to-exit area ratio is 2.55. Naphthalene sublimation method has been employed to study the local heat/mass transfer coefficient and film cooling effectiveness for compound injection angles and various blowing rates around the shaped film cooling hole. Enlarged hole exit area reduces the momentum of the jet at the hole exit and prevents the penetration of injected jet into the mainstream effectively. Hence, higher and more uniform film cooling effectiveness values are obtained even at relatively high blowing rates and the film cooling jet spreads more widely with the shaped film cooling hole. And the injected jet protects the surface effectively at low blowing rates and spreads more widely with the compound angle injections than the axial injection.
입사각 변화에 따른 터빈 블레이드에서의 열전달 특성 변화 (Ⅱ)
이동호(Dong-Ho Rhee),조형희(Hyung Hee Cho) 대한기계학회 2007 大韓機械學會論文集B Vol.31 No.4
The present study investigated local heat/mass transfer characteristics on the surface of the rotating turbine blade with various incidence angles. The experiments are conducted in a low speed annular cascade with a single stage turbine. The blade has a flat tip with the mean tip clearance of 2.5% of the blade chord. A naphthalene sublimation method is used to measure detailed mass transfer coefficient on the blade. At design condition, the inlet Reynolds number is ReC=1.5×10?, which results in the blade rotation speed of 255.8 rpm. Also, the effect of off-design condition is examined with various incidence angles between -15° and +7°. The results indicated that the incidence angle has significant effects on the blade surface heat transfer. In mid-span region, the laminar separation region on the pressure side is reduced and the laminar flow region on the suction side shrinks with increasing incidence angle. Near the tip, the effect of tip leakage flow increases in spanwise and axial directions as the incidence angle decreases because the tip leakage flow is formed near the suction side surface. However, the effect of tip leakage flow is reduced with positive incidence angle.
가스터빈 연소실 냉각을 위한 충돌제트/유출냉각기법에서 요철설치에 따른 냉각특성
이동호(Dong Ho Rhee),남용우(Yong Woo Nam),조형희(Hyung Hee Cho) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11
The present study is conducted to investigate the effect of rib arrangements on an impingement/effusion cooling system with crossflow. To simulate the impingement/effusion cooling system, two perforated plates are placed in parallel and staggered arrangements with a gap distance of 2 times of the hole diameter. Initial crossflow passes between the injection and effusion plates, and square ribs (3㎜) are installed on the effusion plate. Both the injection and effusion hole diameters are 10 ㎜, and the flow rate of crossflov is fixed to that of the impinging jet. The Reynolds number based on the hole diameter and hole-to-hole pitch are fixed to 10,000 and 6 times of the hole diameter, respectively. To investigate the effects of rib arrangements, various rib arrangements, such as 90°transverse and 45°angled rib arrangements, are used. Three 90°rib arrangements and two 45°rib arrangements, which are accomplished by changing the position and the pitch of rib or the attack angle relative to the effusion hole. With the initial crossflow, the flow and heat/mass transfer characteristics are changed significantly from the results without the crossflow. The locally low transfer regions are formed because the wall jets are swept away. When the ribs are installed on the effusion plate, the locally low transfer regions are reduced or disappear, and uniform heat transfer coefficient distributions are obtained because the ribs prevent the wall jets from being swept away by the crossflow and increase local turbulence of the flow near the surface. Average heat transfer coefficients with rib turbulators are approximately 10% higher than that without ribs, and the higher values are obtained with small pitch of ribs.
De-industrialization of Korean Economy and Foreign Trade
이동호(Rhee Dong-Ho) 한국문화산업학회 2001 문화산업연구 Vol.1 No.1
본 연구는 한국 경제의 탈공업화 또는 산업사양화의 원인을 캠브리지대학의 Rowthorn 교수의 이론에 따라 분석하고, 한국의 제조업 사양화가 1987/8년경에 시작되었음을 보였다. 한국경제의 탈공업화 원인인 영국이나 일본에 비해서 대외무역에서 제조업의 비교우위 상실과 수출의 대 GDP비율감소가 큰 원인이었음을 보였다. 아울러 탈공업화 이후의 산업 정책의 과제는 서비스 산업의 비교우위를 높여 수출 주도산업으로 발전시킴으로써 제조업 부문의 적자를 보전하기 위한 노력을 전개하는데 있음을 제시하였다. 본 연구는 한국 경제의 탈공업화 또는 산업사양화의 원인을 캠브리지대학의 Rowthorn 교수의 이론에 따라 분석하고, 한국의 제조업 사양화가 1987/8년경에 시작되었음을 보였다. 한국경제의 탈공업화 원인인 영국이나 일본에 비해서 대외무역에서 제조업의 비교우위 상실과 수출의 대 GDP비율감소가 큰 원인이었음을 보였다. 아울러 탈공업화 이후의 산업 정책의 과제는 서비스 산업의 비교우위를 높여 수출 주도산업으로 발전시킴으로써 제조업 부문의 적자를 보전하기 위한 노력을 전개하는데 있음을 제시하였다.