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김양익(Yang-Ik Kim),정경남(Kyung-Nam Chung) 한국유체기계학회 2005 유체기계 연구개발 발표회 논문집 Vol.- No.-
In this study, redesign of a vaporizer sea-water pump has been carried out using computational fluid dynamics. The flow field of the specified pump model is simulated and analyzed. In the flow analysis full pump model has been used, and multi-block grids are employed to solve the governing equations. In order to improve pump efficiency, systematic redesign has been performed to remove the flow recirculation near the hub of the diffuser vanes. The modified model shows about 4 % improvement in pump efficiency compared to the given model.
B-Spline 기저 고차경계요소법에 의한 자유수면하의 2차원 물체주위 유동해석
유재문,김양익 대한조선학회 2002 大韓造船學會 論文集 Vol.39 No.1
A two-dimensional higher order panel method using B-splines has b e n developed to overcome the disadvantages of the low order panel method and to es are distributed o n b o t h t h e b o d y a n d t h e f r e s u r f a c e . I n s t e a d o f a p l y i n g t h e upwind finite difference schemes to satisfy the linearized fre surface and the radiation condition, the derivatives of the basis functions of the B-spli nes are directly B-spline을 이용하여 물체의 형상과 포텐셜을 표현함으로써, 저차경계요소법의 단점들을 극복하고 수치계산의 정도를 높이기 위한 고차 패널법을 개발하였다. 물체표면과 자유표면에 법선 다이폴과 쏘스를 분포시켰으며, 자유표면 및 방사조건을 만족시키기 위해 상류차분식을 사용하는 대적용함으로써 Dawson 방법에서 문제가 되었던 수치감쇠 문제를 피할 수 있었다.수치계산 프로그램을 검증하기 위해 2차원 원주주위의 유동계산과 날개면 주위의 유동해석을 수행하였으며, B-spline 기저 고차패널법에 의한 수치계산 결과가 저차패널법에 비해 빠른 수렴성과 정확성을 보였고 계산에 필요한 패널 수가 현저히 줄어드는 대단히 만족스러운 결과를 얻었다.
정경남(Kyung-Nam Chung),김양익(Yang-Ik Kim) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
In this study cavitation performance analysis has been carried out to predict the NPSH required value of the models of a vaporization sea-water pump. Rayleigh-Plesset equation is used to represent the generation and collapse of cavitation bubbles. Prior to study pump cavitation, cavitation phenomenon on a NACA 66 modified section has been reproduced, and the calculation result has been compared with experimental data. Impeller-only model and full pump model are employed to study the effects of inlet real geometry and diffuser vanes in pump cavitation analysis. It has been shown that a impeller-only model can be used to analyze vertical pump cavitation around the design point. The analysis shows that cavitation performance of the redesigned model of the vaporization sea-water pump is satisfactory.
정경남(Kyung-Nam Chung),김양익(Yang-Ik Kim),성주헌(Ju-Heon Sung),정인호(In-Ho Chung) 한국유체기계학회 2004 유체기계 연구개발 발표회 논문집 Vol.- No.-
In this study, a rotor blade of a Curtis turbine is investigated. Bezier curve is generally used to define the profile of turbine blades. However, this curve gives a feature of global control, which is not proper to a supersonic impulse turbine blade. Thus, a blade design method is developed by using B-spline curve so that local control is possible to obtain an optimized blade section. To design a Curtis turbine blade section systematically, the blade section has been changed by varying three design parameters using central composite design method. Flow analyses have been carried out for the blade sections, and the effects of design parameters are evaluated.
Yu Jin-Won,Kim Seong-geun,정우영,김양익,최정은,이인원 대한조선학회 2022 International Journal of Naval Architecture and Oc Vol.14 No.1
This paper predicts resistance and propulsion performances in regular and irregular head waves of a 1800 TEU container ship. ‘Calm-water tests’ and ‘resistance test in regular waves’ have been performed. Methods applied are the LVM-W and the revised ITTC-78. Added propeller revolution, thrust, and torque in waves linearly increase as added resistance does. The relative contributions of added propulsion performances in waves have been evaluated using the logarithmic derivative. The spectral method in operating sea states has been applied. The response spectra of added propeller revolution, thrust, and torque show similar characteristics to those of added resistance. The FSEM, LVM-IR, ITTC78-IR, DPM, RTIM, QNM, and TNM are useful to predict added delivered power and propeller revolution in irregular waves when SS < 5. These differences between the DPM/RTIM/QNM/TNM and the Spectral(LVM-W) are dependent on the linearity of fitting line for overload factor. The TNM underpredicts added delivered power due to the lower wake fraction in waves.
박종후(Jong-Hwoo Park),정경남(Kyung-Nam Chung),김양익(Yang-Ik Kim),조성희(Seoung-Hee Cho) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
A steam turbine is one of propulsion systems of a LNG carrier, which consists of high pressure (HP) and low pressure (LP) turbines. In order to obtain high power, each one has the form of a multi-stage turbine. Especially, the first stage of a HP turbine is Curtis stage and uses partial admission considering the turbine efficiency. The performance of a HP turbine can be predicted by a mean-line analysis method, because the relatively large value of hub-tip ratio makes the three-dimensional losses small. In this study, a performance analysis method is developed for a multi-stage HP turbine using Chen’s loss model developed for the transonic steam turbines. To consider the feature of partial admission, different partial admission models are reviewed. This analysis method can be used in partial load conditions as well as full load condition. The calculation results are also compared with the CFD results about some simple cases to check the accuracy of the program. Performance of two HP turbine models are calculated, and the calculation results are compared with the designed data. The comparison shows the qualitative performance analysis result.