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익단간극이 원심압축기 성능에 미치는 영향에 관한 수치해석적 연구
음학진,강신형,Eum, Hark-Jin,Kang, Shin-Hyoung 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.3
Effect of tip leakage flow on through flow and performance of a centrifugal compressor impeller was numerically studied using CFX-TASC flow. Seven different tip clearances were used to consider the influence of tip clearance on performance. Secondary flow and loss factor were evaluated to understand the loss mechanism inside the impeller due to tip leakage flow. The calculated results were circumferentially averaged along the passage and at the impeller exit for quantitative discussion. Tip clearance effect on Performance could be decomposed into inviscid and viscous components using one dimensional equation. The inviscid component is related with the specific work reduction and the viscous component is related with the additional entropy generation. Two components affected Performance equally. while efficiency drop was mainly influenced by viscous loss. Performance and efficiency drop due to tip clearance were proportional to the ratio of tip clearance to exit blade height. A simple model suggested in the present study predict performance and efficiency drop quite successfully.
IEC61400-1 DLC1.1에 따른 풍력터빈의 극한하중
음학진(Hark-Jin Eum),남현우(Hyun-Woo Nam),김만응(Mann-Eung Kim) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
Design lifetime of wind turbines is generally required to be at least 20 years. This paper predicted extreme loads during the design lifetime of wind turbine using an aero-elastic (GH-Bladed) simulation results for a 3-MW class wind turbine. According to design load case 1.1 (DLC1.1) requires in IEC61400-1 3<SUP>rd</SUP> edition<SUP>(1)</SUP>, 50-years extreme loads were statistically predicted by extrapolating short-term load distributions of 10 minutes into long-term load of 50 years. For fitting function were employed two kinds of probability distribution functions, Gumbel and 3-parameter Weibull functions, where 4 different fitting methods were used for each fitting function. 50 year extreme loads were very dependent on the fitting function, the fitting method and the number of short term loads employed to predict the extreme load.
하류 정압교란에 의한 원심압축기의 비정상 성능특성에 관한 연구
음학진(Hark Jin Eum),강신형(Shin Hyoung Kang) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
Centrifugal compressors experience various kinds of downstream pressure disturbances which can lead to unstable operation even at the design condition. In this paper, 3-D numerical simulation was performed to understand the dynamic behaviors of a centrifugal compressor under the pulsation of downstream pressure disturbances and 1-D model using the method of characteristic was developed to predict the behaviors more effectively. Static pressure downstream of the impeller was disturbed as a sinusoidal function with frequencies ranging from 25 to 1,300 ㎐. The response of mass flow rate was attenuated or severely amplified according to the disturbance frequency. The 1-D model predicted well the unsteady behavior as compared with the results of the 3-D numerical simulation.
김범석(Bum-Suk Kim),음학진(Hark-Jin Eum),김만응(Mann-Eung Kim) 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.5
Design life-time of a wind turbine is required to be at least 20 years. In the meantime, the wind turbine will experience a lot of load cases such as extreme loads and fatigue loads which will include several typhoons per year and extreme gusts with 50 years recurrence period as well as endless turbulence flow. Therefore, IEC61400-1 specifies design load cases to be considered in the wind turbine design and requires the wind turbine to withstand the load cases in various operational situations. This paper investigates the ultimate loads which the wind turbine will experience for 20 years and their characteristics based on the IEC61400-1 using an aero-elastic software, GH-Bladed. And the performance characteristics of a wind turbine such as electrical power generation and annual energy yield are also investigated.
남현우(Hyun-Woo Nam),음학진(Hark-Jin Eum),김만응(Mann-Eung Kim) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
The design lifetime of wind turbines is required to be at least 20 years in IEC 61400-1. During the design lifetime, the combinations of environment & operating conditions are called design load cases (DLC) which were defined in IEC 61400-1. The IEC 61400-1 2<SUP>nd</SUP>ed.proposed the Von Karman and the Kaimal turbulence models for DLC calculations. But the turbulence models have been modified in the IEC61400-1 3<SUP>rd</SUP>ed. One is the Mann uniform shear model, the other is the well known Kaimal model with a modified coherence decay factor.<SUP>(1),(2)</SUP> This paper describes comparison of wind turbine extreme loads with each turbulence model where 30 simulations were performed for every wind speed and total 990 cases over the whole range of wind speed. The characteristics for extrapolation loads with each turbulence model will be discussed in this paper.