• 한국추진공학회지
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• 제3권3호
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• pp.31-39
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• 1999

OFO, FOF 삼중 충돌형 및 FOOF 이중 분리 충돌형 분무연소장의 3차원 수치해석을 통한 연소성능 예측 및 성능설계 방법에 대하여 고찰하였다. 예조건화 압축성 유동 지배방정식과 저 레이놀즈수 $\kappa$-$\varepsilon$ 2 방정식 난류모델을 바탕으로 LU-SGS 기법을 사용하여 시간적분 하였으며 분무과정은 DSF 방법을 사용하여 모사하였다. n-heptane 액적과 공기를 연료와 산화제로 하는 액체 추진기관 내에서의 분무 연소장을 계산하였으며 연소에서의 난류의 영향은 eddy 소산모델을 사용하여 모사하였다. 분무연소장의 특성과 연소성능이 비교되었으며, 계산 결과 FOF 삼중 충돌형 분사기의 성능이 가장 우수한 반면, OFO 삼중 충돌형 분사기의 성능이 가장 저조한 것으로 나타났다. 연소효율에 중대한 영향을 미치는 파라미터로는 운동량비에 따른 초기 분무 액적의 평균직경과 혼합효율임을 확인하였다. 연소효율은 초기 분무 액적의 평균직경과 반비례, 혼합효율에 비례하여 증가되며, 산화제/연료 혼합비도 비례하여 상승하나, 일정 운동량비 이상에서는 감소되는 것으로 나타났다. 각 분사기 형태에서 운동량비에 따른 연소효율의 변화는 혼합효율의 변화와 동일한 경향을 보이며 그 크기는 분무 액적의 평균직경에 밀접한 관계가 있음을 알 수 있었다.

• 대한기계학회논문집A
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• 제40권7호
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• pp.629-635
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• 2016

이 논문은 꽃잎들, 나비나 민들레 씨앗들과 같은 생물체 시스템의 불규칙한 운동을 파티클 필터링 이론에 근거하여 예측하고 추적하는 유용한 방법을 제안한다. 생물체 모사 시스템 설계에 있어서, 생체 시스템의 운동에 대한 관측과 생체 시스템 운동학에 대한 새로운 설계원리가 어떻게 자연스럽게 운동하는가에 대한 인상을 얻는데 중요하다. 공기 중에서 비행하는 꽃잎에 대한 시스템 모델링이 베이지안 확률 규칙을 사용하여 수행되었다. 실험결과는 제안된 방법이 공기의 난류로부터 유도된 랜덤한 외란이 있는 경우에도 잘 예측함을 보여준다.

• 한국분무공학회지
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• 제20권2호
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• pp.76-81
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• 2015

Swirl flow has an impact on the stabilization of the flame by the recirculation flow, improvement of the combustion efficiency. The swirl flow in the gun type burner is created by the spinner which is inside the airtube that guide the combustion air. Burner has generally the combustion device composed electronic spark plug, injection nozzle, combustion device adaptor, and spinner. These inner components change the air flow behavior passing through airtube. So, this study analyzed exhaust flow characteristics of the gun type burner according to the ratio of airtube diameter. Turbulence characteristics by the spinner was mean velocity, turbulence intensity, kinetic energy, shear stress and flattness factor of the air flow of axial direction and tangential direction from the exit of the airtube.

• 한국분무공학회지
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• 제20권2호
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• pp.70-75
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• 2015

Swirl flow in the gun type burner has an impact on the stabilization of the flame, improvement of the combustion efficiency. The swirl flow is created by the spinner which is inside the airtube that guide the combustion air. Gun type burner has generally the inner devices composed electronic spark plug, injection nozzle, combustion device adaptor, and spinner. These inner components change the air flow behavior passing through airtube. So, this study conducted the measurement using by hot-wire anemometer and analyzed effect of the swirl number of spinner on the exhaust air of gun type burner. Turbulence characteristics come up in this study was mean velocity, turbulence intensity, kinetic energy, shear stress and flattness factor of the air flow with the change of the distance of axial direction and tangential direction from the exit of the airtube.

• 한국전산유체공학회지
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• 제9권2호
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• pp.30-35
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• 2004

A numerical study of underexpanded jet and impingement on a wall mounted at various distances from the nozzle exit is presented. The 3-dimensional Wavier-Stokes equations and κ-ω turbulence equations are solved. The grids are constructed as overlapped grid systems to examine the distance effect. The DADI method is applied to obtain steady-state solutions. To avoid numerical instability such as the carbuncle phenomena that sometimes accompany approximate Riemann solver, the HLLE+ scheme is employed for the inviscid flux at the cell interfaces. A goal of this work is to apply a number of two-equation turbulence models based on the w equation to the impinging jet problem.

• 대한기계학회논문집B
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• 제29권10호
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• pp.1083-1091
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• 2005

Turbulent flow around a rotating circular cylinder is investigated by Direct Numerical Simulation. The calculation is performed at three cases of low Reynolds number, Re=161, 348 and 623, based on the cylinder radius and friction velocity. Statistically strong similarities with fully developed channel flow are observed. Instantaneous flow visualization reveals that the turbulence length scale typically decreases as Reynolds number increases. Some insight into the spacial characteristics in conjunction with wave number is provided by wavelet analysis. The budget of dissipation rate as well as turbulent kinetic energy is computed and particular attention is given to the comparison with plane channel flow.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2009년도 학술발표회 초록집
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• pp.400-404
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• 2009

본 연구에서는 곧은 식생과 유연한 식생 및 다양한 수심비를 갖는 개수로 흐름 조건에 대한 수리실험을 실시하였다. 레이저 도플러 유속계를 이용하여 수로 전체 단면의 유속을 측정함으로써, 이차흐름이 평균유속 및 난류량에 미치는 영향을 분석할 수 있도록 하였다. 평균유속의 경우, 수치모의결과와 동일하게 측벽근처에서 최대 유속이 발생하였다. 유속측정자료를 이용하여 침수식생 개수로 흐름의 벡터도를 살펴본 결과, 침수식생 개수로의 경우 일반 개수로 흐름과는 달리 바닥 와 (bottom vortex)가 측벽 근처에서 매우 활발한 것으로 나타났으며, 이로 인해 수로 중앙의 높은 운동량을 가진 유체가 측벽방향으로 이동하고 있음을 확인하였다. 또한 측벽에서 이차흐름으로 인해 발생하는 강한 하강류가 레이놀즈응력 및 난류 강도의 수직방향 분포 형태에 영향을 미치는 것을 확인하였다.

• 동력기계공학회지
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• 제15권3호
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• pp.38-45
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• 2011

The computational flow numerical analysis was introduced to predict thc turbulent characteristics in the mixing flow structure of $45^{\circ}$ impinging round jet. This analysis has been carried out through the commercial fluent software. Realizable(RLZ) k-${\varepsilon}$ was used as a turbulent model. It can be known that mean velocities analysed through RLZ k-${\varepsilon}$ turbulent model comparatively predict well the experiments and show well the elliptic shape of mixing flow structure in the Y-Z plane, but analysed turbulent kinetic energies show somewhat differently from the experiments in certain regions.

• 한국자동차공학회논문집
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• 제1권1호
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• pp.1-13
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• 1993

The three-dimensional numerical analysis for in-cylinder flow of four-valve engine without intake port has been successfully computed. These computations have been performed using technique of the general coordinate transformation based on the finite-volume method and body-fitted non-orthogenal grids using staggered control volume and covariant variable as dependent one. Computations are started at intake valve opening and are carried through top-dead-center of compression. A k-$\varepsilon$model is used to represent turbulent transport of momentum. The principal study is the evolution of interaction between mean flow and turbulence and of the role of swirl and tumble in generating near TDC turbulence. Results for three different inlet flow configuration are presented. From these results, complex flow pattern may be effective for promoting combustion in spark-ignition engines and kinetic energy of mean flow near TDC is well converted into turbulent kinetic energy.

• 한국자동차공학회논문집
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• 제2권2호
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• pp.12-23
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• 1994

In order to investigate the effect of turbulent intensity on combustion characteristics, new flame factor model was developed. The principal study is the evaluation of interaction of swirl, tumble and unstrutural component of flow characteristics and correlation between turbulent intensity and flame factor. Computational and experimental study has been, performed such as quasi-dimensional cycle simulation, three dimensional flow analysis, engine performance test and diagnostic simulation. From these studies, it was found that flame factor was a function of engine speed and turbulent intensity.