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분체 이송관내 압력 조절을 위한 오리피스 주위에서의 입자 유동 및 마모 해석
조형희,이재근,박호동,서태원,Cho, Hyung-Hee,Lee, Jae-Keun,Park, Ho-Dong,Seo, Tae-Won 대한기계학회 1998 大韓機械學會論文集B Vol.22 No.11
A numerical study is performed to investigate pressure drops, particle trajectories and erosion around orifice plates in pulverized coal pipe lines. Particle impaction rates change significantly with orifice shapes and Stokes numbers. At Reynolds number of $5{\times}10^5$, the pulverized coal flows well with streamlines and do not collide at the orifice plates at small sizes (${\sim}20{\mu}m$). However, the large particles (over $70{\mu}m$) impact on the front face of the orifice and erode the orifice surface. The pressure loss coefficients around the erode orifice are largely different from the designed original orifice.
가스터빈 블레이드 내부 냉각유로에서 단락요철 설치에 따른 열/물질전달 특성 연구
조형희(Hyung Hee Cho),김경민(Kyung Min Kim),김상인(Sang In Kim),이동호(Dong Ho Rhee) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11
The present study has been conducted to investigate the effect of discrete ribs and rotation on heat/mass transfer characteristics in a two-pass square duct with 90°-rib turbulators. The rib turbulator has a square cross section of 1.5 ㎜. The rib height-to-hydraulic diameter ratio (e/D<SUB>h</SUB>) is 0.056, and the rib pitch-to-rib height ratio (p/e) is 10. The gap width is the same as the rib height. The rotation number ranges from 0.0 to 0.2 while Reynolds number is fixed to 10,000. In a stationary duct, the heat/mass transfer on the surfaces with discrete ribs is enhanced because the gap flow promotes local turbulence and flow mixing near the ribbed surface. In a rotating duct, the gap flow affects differently the heat/mass transfer on leading and trailing surfaces with discrete ribs. On the leading surface of the first pass, heat/mass transfer is increased due to the gap flow. On the trailing surface of the first pass, however, heat/mass transfer is decreased because the gap flow disturbs reattachment of main flow. The phenomenon is distinctly presented by rotation.
조형희(Hyung-Hee Cho),최항철(Hang-Cheol Choi),김광호(Kwang-Ho Kim),정진택(Jin Taek Chung) 한국유체기계학회 2004 유체기계 연구개발 발표회 논문집 Vol.- No.-
2-dimensional impeller's distinctive feature is expected to have an influence on performance and flow characteristics of centrifugal compressor. And new design method is required for 2-dimensional impeller, because the unique geometry cannot be designed using conventional theories. The objective of this study is to advance new design technology for 2-dimensional impeller and to investigate the performance characteristics of designed 2-dimensional centrifugal compressor. The performance test for 2-dimensional impeller is conducted at 35000, 4000 and 45000rpm. Also numerical calculation is applied by using commercial CFD code, FLUENT, and the results are compared with experimental results.
조형희(Hyung Hee Cho) 한국추진공학회 2008 한국추진공학회 학술대회논문집 Vol.2008 No.11
가스터빈 및 램제트의 효율 향상 및 허용수명과 안정성 확보를 위해서는 고온부품에 대한 효과적인 냉각기술개발이 필수적이다. 냉각시스템을 설계하기 위해서는 다양한 냉각방식에 대한 기초적인 연구뿐만 아니라, 이에 대한 이해를 기반으로 실제 조건에 대한 치밀한 해석이 필요하다. 실험 및 해석 결과를 토대로 열적 응력 및 예상 수명을 예측 할 수 있다. 이와 같은 일련의 설계 작업을 열설계 기술이라 하며, 열설계 기술은 가스터빈 및 램제트의 성능 향상은 물론 독자적인 설계 및 개발을 위해 필요한 핵심 요소설계기술 중 하나이다. To improve efficiency and allowable life of gas turbine and ram jet, the proper cooling techniques are needed. It is required not only the basic research of variable cooling techniques but also analysis of real operating conditions when we design the cooling system. From the present experimental and analytical results, we can predict the thermal stress and allowable life. This design process is for a thermal design technique that is the most foundational design technique to improve the efficiency of gas turbines and ram jets