• Journal of Energy Engineering
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• v.4 no.1
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• pp.23-30
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• 1995

분류층 가스화기 설계를 위한 일차연구로서 가스화기 종횡비, 주입方法, 선회강도 및 주입속도 등에 따른 비반응 난류장 특성을 수치해석적 방법에 의해 파악하였다. 수치해석은 검사체적에 기초한 Patankar의 유한차분방법을 이용하였으며 압력과 속도의 연계문제는 SIMPLEC 알고리즘을, 레이놀즈 전단력은 K- 난류모델을 사용하였다. 입자궤적 계산은 공기역학적 향력만을 고려하였으며 비선형적인 공기저항력에 의한 난류변동상관모델은 고려치 않았다. 이차공기 주입방법(parallell injection과 nonparallel 3$0^{\circ}C$ imjection)에 따른 수치해석을 수행하여 Ar tracer의 질량분율 및 기타 속도에 대한 實驗資料와 비교하여 만족할 만한 結果를 얻었다. 나아가서 假想的인 가스화기 모델을 대상으로 가스화기의 종횡비, 선회강도, 주입속도 및 주입각 등에 따른 와류 形成 위치 등을 포함한 유동장 특성 및 입도에 따른 궤적분석을 시도하였다.

• Journal of the korean Society of Automotive Engineers
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• v.9 no.3
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• pp.16-22
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• 1987

직접분사식 디젤기관의 성능과 배기가스 문제에 여향을 주는 실린더 내에서의 연소형태는 크게 연료분사계와 흡입공기 유동계 두 가지에 의해 결정된다. 즉 분사율, 부사시기, 분무형태와 같은 분사계의 특성과 공기선회, 스퀴시(squish), 난류와 같은 공기 유동 특성에 의하여 연소형태가 결 정된다. 이러한 복잡한 연소형테를 기관 특성에 맞게 조정한다는 것은 대단히 어려운 문제인데 이것은 연료화 공기의 혼합이 연소실형상과 흡기계의 형상에 큰 영향을 받으며 연료가 액체 상 태로 연소실내로 들어와 분무과정을 통하여 증발이 되어야만 연소가 가능하기 때문이다. 특히 흡입공기 유동계에 있어서 현재의 직접 분사식 대젤기관의 흡입구 형상은 흡입공기의 운동에너 지에 모멘트를 가하여 연소실내에서 공기의 선희(swirl)를 발생시켜 줌으로써 연료와 공기의 혼 합기를 형성시키는 Helical type이 많이 이용되고 있다. 그러나 기관 성능과 배기가스 특히 NOx는 상반관계를 이루기 때문에 연소실내로 들어오는 흡입공기의 선희강도(swirl ratio)를 너무 강하게만 한다고 하여 좋은 결과를 얻을 수는 없다. 따라서 설계하고자 하는 각 기관에 있어서 요구되는 성능과 배기가스 문제를 만족하는 흡입공기의 선희강도가 얻어질 수 있도록 흡입구 형상을 설계한다는 것은 많은 연구와 경험이 요구되고 있다. 본 자료에서는 직접분사식 디젤기 관에 있어서 흡입공기의 최적 선희강도에 대한 설정방법과 흡입구 형상 설계를 위한 설계 이론 및 정상류 Rig test상에서의 흡입공기 선희강도의 평가방법을 소개하고자 한다.

• Solar Energy
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• v.13 no.1
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• pp.22-30
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• 1993

This Paper deals with the experimental study of the axisymmetric air jet impinging vertically on the flat heating surface with and without swirl. The purpose of this study is to investigate the characteristics of flow, augmentation of heat transfer rate, turbulent intensity, and the comparison of heat transfer rate, the optimal swirling condition about the swirl and nonswirl axisymmetric air jet. In order to augment the heat transfer on the flat heating surface without introducing any additional power, the technique used in the present work was placement of twisted tape inserted pipe in front of the nozzle exit in order to make a swirl. The effect of swirl degree is investigated in case of S=0., 0.056, 0.111, 0.222 and the velocity of the jet was 14, 20, 26, 32, 38, 44m/s. The distance between the nozle exit and the stagnation point on the impinging plate was the H/D=$1{\sim}14$. In order to analyze of the flow structure which increase heat transfer, the velocity and the turbulent intensity of the axisymmetric jet was measured by a hot wire anemometer according to the swirl number and H/D.

• International Journal of Highway Engineering
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• v.9 no.4
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• pp.227-236
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• 2007

The design number of gyration is required in the process of asphalt mix design using gyratory compactor. The purpose of this study is to select the design number of gyration for asphalt mix design in the laboratory. Three types of methods were used to select the design number of gyration. The first method is to select the gyration number which gives the same density with the mixtures compacted with 75 blows of Marshall Compaction. The second method is to select the gyration number which gives the same deformation strength with the mixtures compacted with 75 blows of Marshall Compactor. The third method is to select the gyration number which meet the 4% air voids. Ten mixtures, one type of aggregate(granite), one type of asphalt binder(pen. 60-80), and 10 types of gradation, were prepared for the laboratory tests. As a result, 100 number of gyration was selected for the design number of gyration of the asphalt mix design. This result shows a similar trend with the design number of gyration used in the foreign countries. Thus, the design number of gyration selected in this study can be used for the asphalt mix design using the gyratory compactors.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.1
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• pp.485-492
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• 2013

The effect on collection efficiency with 2-stage vortex finder diameter and back mixing of solid flow due to swirling intensity, turbulence eddies, wall bouncing using the residence time distribution of particle flow in a common and modified cyclone. Higher collection efficiencies of fly ash in a modified cyclone(S = 13, 15cm) are showed than common cyclone. Collection efficiency in modified cyclone was highest at 2-stage vortex finder diameter, S = 13 cm. Variances of residence time distribution and average residence times of glass bead were increased with a diameter(S) of 2-stage vortex finder due to swirling intensity and turbulence eddies. Back mixing of solid flow in a modified cyclone were increased with a gas inlet velocity and showed higher than a common cyclone.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.53-56
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• 2005

Hybrid rocket had many advantage with compared to solid and liquid rockets. In this study, swirl flow hybrid motor was designed and manufactured. And the methods of regression rate improvement wire considered. Thrust was calculated with pressure of the combustion chamber and the regression rate was measured in low flow rate of oxidizer. Several problems and solutions of operating hybrid rocket was presented.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.311-317
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• 2005

Hybrid rocket had many advantage with compared to solid and liquid rockets. In this study, swirl flow hybrid motor was designed and manufactured. And the methods of regression rate improvement were considered. Thrust was calculated with pressure of the combustion chamber and the regression rate was measured in low flow rate of oxidizer. Several problems and solutions of operating hybrid rocket was presented.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.2 no.4
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• pp.82-87
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• 2003

Flow angle with Swirl in a horizontal circular tube and a cylindrical annuli were experimentally studied for its visualization. This present investigation deals with flow angle, flow visualization studies and vortex core by using oil smoke and a hot wire anemometer for Re = 40,000 and 50000 at X/D = 41, 59 and 71 in a horizontal circular tube. In the swirl air flow, a vortex core was formed at high swirl intensity along the test tube. The flow angle and the vortex core depended on the swirl intensity along the test tube. The results of flow angles with swirl measured by flow visualization and hot wire reasonably agree with those of Sparrow One of the primary objectives of this research was to measure the flow angle with swirl in a cylindrical annuli along the test tube for different Reynolds numbers. The Reynolds number for these measurements ranged from 60,000 to 100,000 with L/D = a to 4.

• Journal of the KSME
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• v.23 no.6
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• pp.427-433
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• 1983

내연기관의 성능은 실린더에서 연료의 화학에너지가 열에너지로 얼마만큼 빠르고 완전하게 변화하느냐에 좌우된다. 이를 위해서는 실린더 내에서 뜨거운 압축공기와 연료의 혼합 및 증기화가 요구된다. 엔진의 출력은 매 사이클당 흡입.압축할 수 있는 공기량에 좌우되므로 연소의 해석을 위해서는 실린더 내의 공기유동, 연료의 분무 및 연소과정을 이해 해야한다. 배기와 엔진효율의 요구성때문에 희박 혼합기 또는 EGR (exhaust gas recirculation)이 필요하게 된다. 그러나 희석이 크면 낮은 연소온도, 낮은 층류흐름속도와 화염전면의 낮은 난류강도 때문에 연소기간이 증대하게 된다. 실제로 희박의 증가는 실화 또는 긴 연소 지연기간, 사이클 마다의 연소맥동현상, HC배기의 증가등을 초래하게 된다. 이러한 저온연소의 단점들은 연소상태를 안정시키고 연소량을 증대시키는 공기의 유동을 이용해서 해결 될 수 있다. 최근에는 선회류와 난류의 강도를 증가시켜서 빠른연소(fast burning)를 이루고 있다. 선회류와 난류의 강도를 증대시키는 가장 중요한 2가지 방법은 흡입포트(port), 매니홀드(manifold)설계이다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.10
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• pp.1450-1456
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• 2003

Three-dimensional pipe flows with elbows, tees and headers in three different pipe systems are calculated to estimate the effect of asymmetry of axial velocity profile and swirl on measuring accuracy of an orifice flowmeter. It is evaluated how the pressure difference across the orifice is dependent on the upstream straight pipe length and how swirl intensity, swirl angle, and axial velocity distribution affect the measuring error of the orifice flowmeter. From the results, it is found that variation of the pressure difference across the orifice is negligible in case that maximum swirl angle is less than 2$^{\circ}$, and also that the pressure difference across the orifice is more sensitive to the asymmetry of axial velocity profile rather than the swirl intensity.