• 태양에너지
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• 제15권3호
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• pp.127-140
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• 1995

본 연구는 2차원 충돌공기분류계에서 공기의 흐름 방향과 수직이 되게 설치한 평판 전열면 앞에 전열증진을 목적으로 난류촉진체인 정4각 로드군을 설치할때의 유동특성과 전열특성을 실험을 통해서 구명하고, 본 실험범위내에서 로드의 최적 설치조건을 제시하기 위한 실험적 연구이다. 실험은 먼저 로드를 설치하지 않은 평판에서의 전열특성을 밝힌후, 로드를 설치할 경우 로드의 피치가 40mm일때 로드와 전열면사이의 간극 및 로드폭 변화시의 유동특성과 전열 특성을 구명하여 로드를 설치하지 않은 평판과의 전열성능을 비교하였다. 본 실험범위내에서 전열면에 간극을 두고 로드를 설치하면 로드 바로 밑에서의 가속 및 로드에 의한 난류생성과 재부착에 의해 전열성능은 향상되며 로드폭을 변화시킨 경우에는 로드폭이 클수록 로드 바로 밑에서의 가속효과와 로드 직전에 와류의 영향이 크게 작용하여 전열성능이 향상된다.

• International Journal of Industrial Entomology and Biomaterials
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• 제37권2호
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• pp.105-108
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• 2018

Recently matured silkworm powder was developed by RDA. In this study, the effect of pulverizing method on the particle size of matured silkworm powder was examined. FESEM was performed to observe the morphology and to measure the particle size of silkworm powder. Particle morphology of air-jet mill pulverized powder was round and smooth, however, those of roller-mill and hammer-mill pulverized mature silkworm was more harsh and square. Particle size was varied with pulverizing technique as follows; $1.1{\mu}m$ (air-jet mill), $10{\mu}m$ (roller mill), and $120{\mu}m$ (hammer mill), respectively. A proximate analysis results of air-jet mill powder showed that crude protein, crude lipid, crude fiber, and ash was 73%, 12%, 1.95%, and 3.4%, respectively. According to our results, air-jet mell technique might be used to make a tiny matured silkworm powder.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.525-528
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• 2002

The objective of this study is to investigate characteristics of flow by the Rod shape and the choice of the turbulent intensity enhancement section. The Rod was setup vertically to the way of a nozzle exit flow and nozzle diameter is 17mm. Rod height is 5mm and its shapes are square, triangle, and circle. Characteristics of fluid such as velocity vector distribution, kinetic energy, turbulent intensity, and etc. were visualized, observed, and considered at 3 kinds of Re No. such as 2000, 3000, and 4000. The characteristics of flow field were investigated in each case of the distance rate from the nozzle exit to impinging plate(H/B=8, 10). The temperature of water is $20^{\circ}E$ and the measurement region divided by 3 sections(I, II, III). The nozzle diameter is 17mm. As the experimental result by PIV measurement, scale of the vector profile showed a tendency to an unbalance parabola distribution as increasing of the Re No. When the impinging plates such as square, triangle, and circle shape are installed respectively in front of the flow accelerated, rod shape of the highest velocity vector is circle shape and rod shape of the highest turbulent Intensity is square shape.

• 태양에너지
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• 제15권1호
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• pp.85-94
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• 1995

본 연구는 2차원 충돌분류계의 포텐셜코어영역(H/B=2)내에서 전열증진을 목적으로 전열면 앞에 폭 6mm인 정 4각 rod군을 설치하고 rod와 전열면간의 간극(C=1, 2, 4, 6mm)과 rod와 rod사이의 피치(P=30, 40, 50mm)를 변화시킬때의 유동특성과 전열특성을 실험적으로 규명하고 rod를 설치하지 않았을 경우와 비교 검토한 것으로 간극변화시에는 C=1mm인 경우가 전열성능이 가장 우수하였으며, rod의 피치(P)를 변화시킨 경우에는 rod가 없는 평판에 비해 각각 약 1.6배의 평균전열증진율이 나타났다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3529-3533
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• 2007

The advantages of the SITVC(secondary injection thrust vector control) technique over mechanical thrust vector systems include a reduction in both the nozzle weight and complexity due to the elimination of the mechanical actuators that are used in conventional vectoring. Computational study is performed to understand the fluidic thrust vectoring control of an axisymmetric nozzle, in which secondary gas injection is made in the divergent section of the nozzle. The nozzle has a design mach number 3. The effect of injection hole number and shape of secondary jet on the mach number distribution of SITVC were investigated. The standard ${\kappa}$ - ${\epsilon}$ turbulence model solved the complex three-dimensional nozzle flows perturbed by the secondary gas jet. The numerical code was validated by experiment. The results showed that the mach number distribution of circular and square nozzle are similar each other. As number of second injection hole increasing, a effect of deflection was decreased.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.37-42
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• 2001

This paper computes the bluff-body stabilized jet and flame. This study numerically investigates the nonpremixed $C_{2}H_{4}-air$ jet for the nonreacting case and the nonpremixed $CH_{3}OH-air$ turbulent flames for the reacting case using the laminar flamelet model on modified KIVA2 code. And this study predicts $NO_{x}$ formation characteristics using Eulerian Particle Flamelet Model. In the present study, the turbulent combustion model is applied to analyze both nonreacting and reacting case. And both standard $k-{\varepsilon}$ model and modified $k-{\varepsilon}$ model are used in nonreacting case. Calculations are compared with experimental data in terms of velocity, mixture fraction, mixture fraction Root Mean Square and Temperature. The present model correctly predicts the essential features of flame structures and $NO_{x}$ formation characteristics in the bluff-body stabilized flames.

• 대한기계학회논문집
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• 제16권6호
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• pp.1150-1155
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• 1992

본 연구에서는 제철소 열연공정의 냉각효율 개선을 위한 기초연구로 수행되었 다. 전열면의 초기온도가 900.deg. C이상일 때 층류 냉각방식에 의한 고온강판의 냉각특 성에 영향을 주는 모든 인자를 엄밀히 고려하는 것은 매우 어려운 일이다.따라서 본 연구에서는 노즐과 고온면 사이 거리(L), 유량(Q), 냉각 초기온도 등을 실제 작업 조건에 가깝게 변화시켜 가면서 수냉반경의 변화를 중심으로 전열면의 냉각 특성을 해 석하였다.

• 설비공학논문집
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• 제10권6호
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• pp.743-752
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• 1998

Experiments were performed to characterize single-phase heat transfer behavior of submerged liquid jet with multiple nozzle normally impinging on the smooth and extended surfaces. Arrays of 9 and 36 nozzles were used, with diameters of 0.5 to 2.0mm providing nozzle area ratio (AR) from 0.05 to 0.2. The square pin fin arrays were chosen as extended surfaces and the effects of geometrical parameters such as fin height, the ratio of fin width to channel width on heat transfer enhancement were examined. Single nozzle characteristics were also evaluated for comparison. The results clearly showed that heat transfer enhancement could be realized by using multiple nozzles at the constant volume flow rate. The average Nusselt number of multiple nozzle impingement on the smooth surface was correlated by the following equation : Nu/$Pr\frac{1}{3}=0.94 Re^{0.56}N^{-0.12}AR^{0.50}$The average heat transfer coefficients of multiple nozzle impingement on the extended surfaces decreased with increasing fin height and the ratio of fin width to channel width. The effectiveness of ex-tended surfaces ranged from 1.5 to 3.5 depending on the fin height, the ratio of fin width to channel width of pin fin arrays, nozzle number and nozzle area ratio.

• 대한기계학회논문집B
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• 제36권1호
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• pp.75-81
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• 2012

고온의 동축류 공기와 수소가 함유된 메탄 연료제트에서 자발화된 층류 부상화염의 특성을 실험적으로 조사하였다. 그 결과로 순수 메탄 제트에서 자발화되는 경계 온도인 920 K 를 초과하는 초기 온도에서 메탄/수소 혼합기의 자발화된 부상화염은 연료 몰분율에 따라 삼지화염 또는 마일드 연소를 보였고, 제트속도에 따라 부상화염의 높이가 증가하는 전형적인 특성을 보였다. 소량의 수소가 첨가된 부상화염의 높이는 메탄의 경우와 유사하게 단열적 점화지연시간의 2 승에 대한 의존성이 유지되었다. 반면에, 초기 온도가 920 K 미만인 경우에서 화염은 수소의 점화 촉진에 의해서 자발화 되었다. 그리고 제트속도가 증가함에 따라 자발화된 부상화염의 높이는 비선형적으로 감소하는 독특한 특성을 보였으며, 수소의 선호확산이 그 현상에 대해서 중요한 역할을 할 것으로 예상된다.

• Journal of Communications and Networks
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• 제1권2호
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• pp.111-117
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• 1999

Using a method recently reported in the literature for analyzing the bit error probability (BEP) performance of noncoherent Mary orthogonal signals with square-law combining in the presence of independent and identically distributed Nakagami-m faded paths, we are able to reformulate this method so as to apply to a generalized fading channel in which the fading in each path need not be identically distributed nor even distributed ac-cording to the same family of distribution. The method leads to exact expressions for the BEP in the form of a finite-range integral whose integrand involves the moment generating function of the combined signal-to-noise ratio and which can therefore be readily evaluated numerically. The mathematical formalism is illustrated by applying the method to some selected numerical examples of interest showing the impact of the multipath intensity profile (MIP) as well as the fading correlation profile (FCP) on the BEP performance of M-ary orthogonal signal over Nakagami-m fading channels. Thses numerical results show that both MIP and FCP induce a non-negligible degradition in the BEP and have therefore to be taken into account for the accurate prediction of the performance of such systems.