• International Journal of Naval Architecture and Ocean Engineering
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• 제5권3호
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• pp.414-430
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• 2013

This paper shows the study of preswirl duct as an effective energy saving devices that have been devised and reviewed to support the propeller performance, especially for the ship of VLCC with large block coefficients. From the bare hull wake measurements, typical upper/lower asymmetry of hull wake at the propeller disk was found. The 2 kinds of pre-swirl duct, Unconventional half circular duct and Conventional circular pre-swirl duct have been designed and reviewed to recover the loss of propeller running in that condition. The general function of the pre-swirl duct was set to work against this asymmetry of wake and generate pre-swirled flow into the propeller against the propeller rotating direction. The optimum self propulsion tests with various angle configurations were carried out and the best configuration was decided. Accordingly, cavitation test was carried out with best configuration of unconventional half circular duct. The blade surface and tip vortex cavitation behaved smoother when the duct was mounted. The hull pressure amplitudes reflected this difference, so the hull pressure amplitude with duct was smaller than that of without duct.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집B
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• pp.641-645
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• 2001

In this paper, it is discussed that active noise control in a circular duct using smart foam. Firstly, it is demonstrated that the potential of the conventional smart foam, proposed by Fuller, for active noise control in a duct. Conventional smart foam is not applicable to active noise control in a duct having flow. Thus, this paper presents a ring-type smart foam as an alternative. The ring-type smart foam consists of polyurethane acoustic foam of lining shape and PVDF film embedded in the foam. The embedded PVDF element acts as an actuator to reduce noise at lower frequencies and the foam absorbs noise at higher frequencies. A filtered-x LMS controller is used to minimize the signal from the error microphone. Experiments are executed to reduce broadband and tonal noise.

• 대한기계학회논문집B
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• 제22권4호
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• pp.551-561
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• 1998

This paper was studied to understand the characteristics of heat transfer coefficients and surface temperature distributions around a circular combustion chamber within the heat-intercept duct of kerosene fan heater. The experiment was carried out in the heat-intercept duct of kerosene fan heater attached to the blow-down-type subsonic wind tunnel with a test section of 240 mm * 240 mm * 1200 mm. The purpose of this paper was to obtain the basic data related with normal combustion for new design from conventional kerosene fan heater, and to investigate the effect of surface temperature, local and mean heat transfer coefficients versus flow-rate of convection axial fan according to the variations of heat release conditions from kerosene fan heater during normal combustion. Consequently it was found that (i) the revolution of convection axial fan during combustion had a smaller value than that of non-combustion because of the thermal resistance due to the high temperature in the heat-intercept duct, (ii) the pressure ratio P$_{2}$/P$_{1}$ had a comparatively constant value of 0.844 according to the revolution increase of turbo fan and the heating performance of kerosene fan heater had a range of 1,494 ~ 3,852 kcal/hr, (iii) the local heat transfer coefficient around a circular combustion chamber had a comparatively larger scale in the range of 315 deg. < .theta. < 45 deg. than that in the range of 90 deg. < .theta. < 270 deg. as a result of heat transfer difference between front and back of a circular combustion chamber, and (iv) the mean heat transfer coefficient around a circular combustion chamber increased linearly like a H$_{m}$=95.196Q+104.019 in condition of high heat release according to the increase of flow-rate of axial fan.n.

• 한국축산시설환경학회지
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• 제10권2호
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• pp.93-100
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• 2004

본 연구는 우리나라에 건축되어져 있는 개방식 육성$\cdot$비육돈사나 무창식 육성$\cdot$비육돈사에 대한 효율 비교분석 연구가 없는 실정으로 개방식 육성$\cdot$비육돈사와 무창식 육성$\cdot$비육돈사의 환경효율을 검증하고자 하였다. 겨울철과 여름철로 나누어 실시한 실험결과는 다음과 같다. 1. 무창식 육성 비육돈사는 외부의 기온 변화가 심하더라도 돈사내부의 온도는 외부기온의 영향을 받지 않고 여름철 $31.8\~33.8^{\circ}C$, 겨울철 $17.9\~19.5^{\circ}C$를 유지하였으나 개방식 육성$\cdot$비육돈사는 여름철 32.1$\~$32.9, 겨울철 $15.8\~16.7^{\circ}C$를 유지하여 온도효율이 낮았다. 2. G2, G4 육성$\cdot$비육돈사는 돼지생활 공간(하부) 지점에서의 공기유속은 겨울철 최소환기($5\%$) 수준으로 하였을 때 0.2$\~$0.3 m/s 였으며, 여름철 최대환기($95\%$) 수준에서는 0.5$\~$0.6 m/s로 분포되어 여름철 및 겨울철의 육성$\cdot$비육돈사내 공기유속이 G1, G3 육성$\cdot$비육돈사보다 양호하였다. 3. 암모니아 농도를 측정한 바 G2, G4 육성$\cdot$비육돈사는 여름철 13.3$\~$16.6 ppm, 겨울철14.0$\~$~14.6 ppm으로 측정되었으며, G1, G3 육성$\cdot$비육돈사는 여름철 14.6$\~$20.3 ppm, 겨울철 20.3$\~$25 ppm을 유지하여 G1, G3 육성$\cdot$비육 돈사보다는 낮게 나타났다.