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An effective shape of floor splitter for reducing sub-surface vortices in pump sump
강원태,신병록,도덕희 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.1
An experimental investigation on the effective shape of a floor splitter to reduce sub-surface vortices and cavitation which arise in thevicinity of the pump bells in pump sump is performed. A test model sump was designed based on the Froude number similitude for therecommended structure layout by HI-9.8 standard for pump intake design. To obtain an effective shape of the splitter as an anti-vortexdevice (AVD), three types of quadrilateral submerged bar with different shape and dimension in sectional area are considered. From theexperimental results with and without the splitter attached on the floor under the bell mouth, it was confirmed that the installation of theAVD is very effective to reduce abnormal vortices including sub-surface vortices, pre-swirls and other undesirable hydraulic phenomena. Because of the splitter, sub-surface vortices under the bell mouth did not appear anymore and the swirl was dramatically weakened. Theevaluation of AVD was made by the measurement of swirl angles indicating the strength of the vortices and pre-swirls. Splitters withsquare sections showed partly large swirl angles beyond the acceptable criteria of HI standard though a large square was more effectivethan a small one. Meanwhile, the splitter with trapezoidal section was showed swirl angle values of less than 5 degrees in all cases ofpump operation. Among the three types of AVD, the trapezoidal splitter is the most effective one to suppress the vortices. It is very usefulto reduce the occurrence of submerged vortices and to obtain stable inflow condition for designing a high performance pump sump.
Anti-Phase IMD 선형화 기술을 이용한 W-CDMA 30 W 대전력 증폭기
강원태,도지훈,장정석,홍의석,Kang, Won-Tae,Do, Ji-Hoon,Chang, Jeong-Seok,Hong, Ui-Seok 한국전자파학회 2007 한국전자파학회논문지 Vol.18 No.7
본 논문에서는 구동단의 IMD 특성을 종단의 IMD 특성과 반대의 값을 갖도록 하는 anti-phase IMD 정합 기법을 이용하여 대전력 증폭기의 선형성을 개선하였으며, 이의 설계 과정을 나타내었다. W-CDMA 4FA 입력 신호시 평균 출력 전력 30 W에서 ACLR -55 dBc@5 MHz offset을 얻었으며, 최대 전력 이득을 얻기 위한 최적 정합시와 측정 결과를 비교시, 약 12 dBc 이상 개선되었다. 또한, 평균 출력 전력 50 W에서도 상용 제품 규격을 만족함을 보였다. This paper shows how the ACLR of power amplifier can be reduced by using Anti-phase IMD linearization technique which generate anti-phase IMD in the driver stage compare to output stage's IMD. And design process proposed. From the experimental result of W-CDMA 4FA input signal, this amplifier has ACLR -55 dBc@5 MHz offset at 30 watts average power. Compare to optimum matching technique to get maximum power gain, this technique has been improved ACLR by 12 dBc. Also this amplifier meets 50 watts average output power amplifier specification in domestic market.
Correction증폭기 제어용 Delay Line을 이용한 새로운 형의 Feedforward 선형화기 설계에 관한 연구
강원태,장익주,남상대,Gang, Won-Tae,Jang, Ik-Ju,Nam, Sang-Dae 대한전자공학회 2000 電子工學會論文誌-TC (Telecommunications) Vol.37 No.2
본 논문에서는 correction 증폭기의 위상특성을 제어하는 delay line을 사용한 새로운 형의 feedforward 선형화기를 제시하였다. 사용된 delay line은 상용제품에서 사용하는 pilot-tone 회로 없이 IM 성분을 제거하는 기능을 수행한다 선형화기의 오차신호구간(error signal loop)은 위상변환기, 감쇄기 및 빼기회로 등의 주요 소자들로 구성되며, pilot-tone 신호 발생 회로 없이 보다 우수한 선형화 특성을 얻기 위하여 이들 주요 소자들을 새로운 형으로 개발하였으며, 이는 상용 선형화기 설계에서 필수적인 기술이다. 선형화기는 KMW사에서 국내 PCS기지국 용으로 개발된 35W 대전력 증폭기를 사용하였으며, 측정을 위하여 중심주파수 1855 MHz에서 0.6 MHz 신호 간격을 갖는 two-tone신호를 입력하였다. 측정 결과, 약I5dB(30∼45 dBm)의 입력신호 변화 범위에서 58.5dBc∼63.2 dBc IMD 특성을 보였으며, 약 16.9 dB∼24.6 dB의 C/I 개선을 구현하였다. In this Paper, a new type of feedforward linearizer using a delay line which controls the phase characteristics of the correction amplifier block is proposed. The extra delay line provides the control-ability of IM signals so that the IM rejection is accomplished without the conventional pilot tone. The error signal loop consists of several key components such as phase shifter and attenuator, subtractor. These key components are replaced by new designs in order to obtain better linearization characteristics without the pilot tone generator which is indispensable in the conventional linearizer designs. The proposed linearizer was designed at Korean PCS band and combined with 35W HPA manufactured by KMW inc., and tested with two-tone signals separated 0.6MHz apart at the center frequency of 1855MHz. The experimental results show C/l improvement by 16.9 ~ 24.6 dB over 15 dB dynamic range(30 ~45 dBm) which gave IMD of 58.5~63.2 dBc for the designed LPA.
강원태(W. T. Kang),신병록(B. R. Shin) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
A vertical axis wind turbine is designed and manufactured to investigate performance characteristics and efficiency of the turbine. Runner diameter and height are 140mm. Upper and lower panel is fabricated using an acrylic with the blade which is made of PVC pipe. From the results of wind tunnel test and CFD analysis, it is investigated that at any turbine load wind turbine has a typical performance characteristics indicating maximum wind power of each wind speed. Both result of experiments and CFD analysis were almost the same with each other.