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Kim, Sangjo,Kim, Kuisoon,Son, Changmin Elsevier 2016 Applied Thermal Engineering Vol.103 No.-
<P><B>Abstract</B></P> <P>A numerical study for a tubular heat exchanger (HX) is performed to evaluate the effect of the optimum arrangements of guide vanes (GVs) in a combining header on the performance of the HX. A Pareto analysis used in multi-objective optimization is conducted to find the optimum arrangements of the GVs. For optimization, a total of five design variables are used to describe the arrangements of the four GVs. The design variables include a length of minor axis and vertical positions of each elliptic GV. The objective functions are the total pressure drop and the flow uniformity of the HX. An approximate optimization method is employed to reduce the computational expense. The Pareto analysis results indicate that the total pressure drop and the flow uniformity of the HX with GVs are inversely related. The flow velocity and the static pressure distributions are considerably changed in the combining header by applying the GVs. The HX with the arrangement of GVs for minimizing the total pressure drop shows that the percentage reductions compared with the HX without GVs were 58.64% for the flow non-uniformity and 2.80% for the total pressure drop. The HX with the arrangement of GVs for minimizing the flow non-uniformity presents that the percentage reductions in the flow non-uniformity and the total pressure drop were 86.22% and 0.33%, respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Guide vanes are installed in the combining header of a U-type tubular heat exchanger. </LI> <LI> Arrangements of the guide vanes are obtained by using optimization method. </LI> <LI> Total pressure drop and the flow uniformity of heat exchangers are inversely related. </LI> <LI> The flow uniformity is considerably improved by using optimized guide vanes. </LI> </UL> </P>
Kim, Donghyun,Kim, Kuisoon,Choi, Jeongyeol,Son, Changmin The Korean Society for Aeronautical and Space Scie 2015 International Journal of Aeronautical and Space Sc Vol.16 No.2
The present work performs three-dimensional flow calculations based on Reynolds Averaged Navier-Stokes (RANS) and Delayed Detached Eddy Simulation (DDES) to investigate the flow field of a transonic rotor (NASA Rotor 37) at near-stall condition. It is found that the DES approach is likely to predict well the complex flow characteristics such as secondary vortex or turbulent flow phenomenon than RANS approach, which is useful to describe the flow mechanism of a transonic compressor. Especially, the DES results show improvement of predicting the flow field in the wake region and the model captures reasonably well separated regions compared to the RANS model. Besides, it is discovered that the three-dimensional vortical flows after the vortex breakdown from the rotor tip region are widely distributed and its vortex structures are clearly present. Near the rotor leading edge, a part of the tip leakage flows in DES solution spill over into next passage of the blade owing to the separation vortex flow and the backflow is clearly seen around the trailing edge of rotor tip. Furthermore, the DES solution shows strong turbulent eddies especially in the rotor hub, rotor tip section and the downstream of rotor trailing edge compared to the RANS solution.
Adaptation Method for Overall and Local Performances of Gas Turbine Engine Model
Kim, Sangjo,Kim, Kuisoon,Son, Changmin The Korean Society for Aeronautical Space Sciences 2018 International Journal of Aeronautical and Space Sc Vol.19 No.1
An adaptation method was proposed to improve the modeling accuracy of overall and local performances of gas turbine engine. The adaptation method was divided into two steps. First, the overall performance parameters such as engine thrust, thermal efficiency, and pressure ratio were adapted by calibrating compressor maps, and second, the local performance parameters such as temperature of component intersection and shaft speed were adjusted by additional adaptation factors. An optimization technique was used to find the correlation equation of adaptation factors for compressor performance maps. The multi-island genetic algorithm (MIGA) was employed in the present optimization. The correlations of local adaptation factors were generated based on the difference between the first adapted engine model and performance test data. The proposed adaptation method applied to a low-bypass ratio turbofan engine of 12,000 lb thrust. The gas turbine engine model was generated and validated based on the performance test data in the sea-level static condition. In flight condition at 20,000 ft and 0.9 Mach number, the result of adapted engine model showed improved prediction in engine thrust (overall performance parameter) by reducing the difference from 14.5 to 3.3%. Moreover, there was further improvement in the comparison of low-pressure turbine exit temperature (local performance parameter) as the difference is reduced from 3.2 to 0.4%.
Donghyun Kim,Kuisoon Kim,Jeongyeol Choi,Changmin Son 한국항공우주학회 2015 International Journal of Aeronautical and Space Sc Vol.16 No.2
The present work performs three-dimensional flow calculations based on Reynolds Averaged Navier-Stokes (RANS) and Delayed Detached Eddy Simulation (DDES) to investigate the flow field of a transonic rotor (NASA Rotor 37) at near-stall condition. It is found that the DES approach is likely to predict well the complex flow characteristics such as secondary vortex or turbulent flow phenomenon than RANS approach, which is useful to describe the flow mechanism of a transonic compressor. Especially, the DES results show improvement of predicting the flow field in the wake region and the model captures reasonably well separated regions compared to the RANS model. Besides, it is discovered that the three-dimensional vortical flows after the vortex breakdown from the rotor tip region are widely distributed and its vortex structures are clearly present. Near the rotor leading edge, a part of the tip leakage flows in DES solution spill over into next passage of the blade owing to the separation vortex flow and the backflow is clearly seen around the trailing edge of rotor tip. Furthermore, the DES solution shows strong turbulent eddies especially in the rotor hub, rotor tip section and the downstream of rotor trailing edge compared to the RANS solution.
압축기 정익, 터빈 노즐 가변 메카니즘 및 제어기법 연구
김상조(Sangjo Kim),김동현(Donghyun Kim),배경욱(Kyoungwook Bae),김대일(Dae-il Kim),손창민(Changmin Son),김귀순(Kuisoon Kim),이대우(Daewoo Lee),고정상(Jeungsang Go),최동환(Dong-Whan Choi),김명호(Myungho Kim),민성기(Seongki Min) 한국추진공학회 2015 한국추진공학회지 Vol.19 No.5
In case of a gas turbine engine for supersonic operation, the engine have a wide range of operating inlet mass flow rate and required high performance such as thrust and fuel consumption. Therefore, variable system and its optimal control logic are essentially needed. In this work, a method for performance prediction of a gas turbine engine with variable system compressor and its control scheme were developed. Conceptual design of compact acuation system for the operation of the variable system was also conducted. The performance of a low-bypass ratio mixed flow turbofan engine was analyzed, and it was observed that the surge margin of the engine is improved at off-design condition by applying the control scheme.
김재민(Jaemin Kim),김귀순(Kuisoon Kim),최정열(Jeong-Yeol Choi),정용운(Yongwun Jung),황인희(In-Hee Hwang) 한국추진공학회 2008 한국추진공학회지 Vol.12 No.6
We have simulated the performance of a simple engine model with a gas turbine engine simulation program based on CFD. 2-dimensional Navier-Stokes code for the viscous flow was applied to simulate a compressor and a turbine, and the chemical equilibrium code with the lumped method was applied to simulate the combustor. Unsteady-flow phenomenon between rotor and stator of the compressor and the turbine was analyzed by steady mixing-plane method. In this way, the influence of the turbine blade pitch on the engine was investigated. It was shown that the compressor is operated at more higher pressure conditions as narrower the pitch distance of the turbine.
터빈 노즐의 Fillet 설치에 따른 가스터빈 엔진의 성능 특성에 관한 연구
김재민(Jaemin Kim),진상욱(Sangwook Jin),김귀순(Kuisoon Kim),최정열(Jeong-Yeol Choi),김춘택(Chun-Taek Kim) 한국추진공학회 2009 한국추진공학회 학술대회논문집 Vol.2009 No.11
터빈 형상에 따른 가스터빈 엔진의 성능을 전산유체역학을 기반으로 하여 개발된 프로그램을 통하여 예측하여 보았다. 압축기, 연소기, 터빈의 상호작용을 고려하여 엔진의 성능을 예측하였다. 압축기와 터빈의 해석은 각각 2차원과 3차원의 Navier-Stokes 방정식을 사용하였다. 연소기에서는 화학평형방정식을 적용하여 온도변화를 계산하였다. 계산은 터빈 노즐의 fillet 설치의 유무에 따라 두 가지 형상을 적용하여 비교하였다. In this study, the effect of turbine geometry on the overall performance of a gas turbine was investigated by computational fluid dynamics. Overall engine performance was predicted through a full engine simulation program which can predict the interactions of the compressor, the combustor and the turbine. The compressor and the turbine analysis code solves 2D and 3D Navier-Stokes equations respectively. The chemical equilibrium code was applied to simulate the combustor. The computations were performed for two different shapes of turbine nozzle. The nozzle shapes adopted a baseline blade and a blade with fillet.