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보조 동력 장치 연료 공급용 서보밸브의 유동 특성 해석
김성수(S. S. Kim),장세명(S. M. Chang),정헌술(H. S. Jeong),류혁(H. Ryu),이상효(S. H. Lee) 유공압건설기계학회 2008 드라이브·컨트롤 Vol.5 No.4
In this paper, the authors benchmark a servo valve model for the fuel supply system of Auxiliary Power Unit (APU) in the KHP helicopter. This valve is directly driven with a torque motor, and the size of small gap controlled by a flapper can make change of flow rate under given pressure drop between inlet and outlet. CFD analyses using a commercial code, ANSYS-CFX 10 are performed for the series of three-dimensional models at various openness conditions. The computational results on simplified models show that CFD can play a fine roll in the design of flow path as well as in the estimation of flow force due to its precision and good repeatability. Consequently, the CFD analysis helps valve designers to understand its flow characteristics from the basis of physical fundamentals.
TiO₂ 첨가가 Mn - Zn Ferrites의 자기적 특성에 미치는 영향
박종원(J. W. Park),한영호(Y. H. Han),이상효(S. H. Lee) 한국자기학회 1999 韓國磁氣學會誌 Vol.9 No.6
Mn-Zn ferrites에 TiO₂가 첨가될 때 전력손실, 밀도, 초기투자율, 저항, 그리고 미세구조의 변화를 고찰하였다. 첨가량이 증가함에 따라 밀도는 증가했지만, 초기투자율은 감소하였다. TiO₂의 첨가에 따라 electron hopping을 일으키는 활성화에너지와 전기저항이 증가하였다. 1150 ℃에서 소결한 TiO₂를 1.5 wt% 첨가한 시편은 1 ㎒, 25 mT, 80 ℃에서 83 ㎽/㎤의 전력손실을 나타내었다. 그러나 1200 ℃에서 소결할 때는 과대입성장이 발생하여 같은 측정 조건에서 1168 ㎽/㎤의 전력손실을 얻었다. The effect of TiO₂ addition has been studied on the power loss, density. initial permeability, resistivity, and microstructure of Mn-Zn ferrites. TiO₂ addition increased the density of sintered body and decreased of the initial permeability. Activation energy for electron hopping as well as electrical resistivity increased with TiO₂ addition. The toroidal core sintered at 1150℃ with 1.5 wt% of TiO₂ demonstrated the power loss of 83 ㎽/㎤ at 1 ㎒, 25 mT, 80℃. However, the same specimen sintered at 1200℃ lead to the power loss, 1168 ㎽/㎤ at 1 ㎒, 25 mT, 80℃ and developed an exaggerated grain growth.