• Journal of Mechanical Science and Technology
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• 제15권3호
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• pp.374-383
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• 2001

The spray/wall interaction is considered as an important phenomenon influencing air-fuel mixing in the internal combustion engines. In order to adequately represent the spray/wall interaction process, impingement regimes and post-impingement behavior have been modeled using experimental data and conservation constraints. The modeled regimes were stick, rebound, spread and splash. The tangential velocities of splashing droplets were obtained using a theoretical relationship. The continuous phase was modeled using the Eulerian conservation equations, and the dispersed phase was calculated using a discrete droplet model. The numerical simulations were compared to experimental results for spray impingement normal to the wall. The predictions for the secondary droplet velocities and droplet sizes were in good agreement with the experimental data.

• 한국추진공학회지
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• 제3권3호
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• pp.9-15
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• 1999

대형로켓엔진을 개발하기 위한 Injector 설계에서 연합된 분무군에 대한 해석은 필수적이다. 본 연구에 서는 운동량이 같은 두 개의 분류가 충돌함으로서 생기는 두 스프레이의 간섭이 질량분포와 액적의 크기/속도분포에 미치는 영향을 조사하였다. 질량채집장치와 PDPA가 실험장치로 사용되었고 물을 실험유체로 사용하였다. 두 스프레이 휀의 운동량비가 1인 경우 두 스프레이 휀의 충돌로 인한 간섭의 영향은 아주 작았다. 마찬가지로 액적의 속도/크기분포도 두 스프레이 휀의 충돌로 인한 간섭영향은 아주 작았으나, 액적의 크기는 2차 충돌로 인하여 충돌점 부근에서 약간 작아졌다. 즉, 추후에 운동량비가 동일한 두 스프레이 휀을 가진 인젝터에 대한 연구시에는 간섭효과를 무시할 수 있음을 알 수 있었다.

• 한국자동차공학회논문집
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• 제6권4호
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• pp.86-100
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• 1998

The impingement of the fuel spray on the wall within the combustion chamber in compact high-pressure injection engines and on the intake port wall in port-fuel-inje- ction type engines is unavoidable. It is important to understand the characteristics of impinging spray because it influences on the rate of fuel evaporation and droplet distrib- ution etc. In this study, the numerical study for the characteristics of spray/wall interaction is performed to test the applicability and reliability of spray/wall impingement models. The impingement models used are stick model, reflect model, jet model and Watkins and Park's model. The head of wall-jet eminating radilly outward from the spray impingement site contains a vortex. Small droplets are deflected away from the wall by the stagnation flow field and the gas wall-jet flow. While the larger droplets with correspondingly higher momentum are impinged on the wall surface and them are moved along the wall and are rolled up by wall-jet vortex. Using the Watkins and Park's model the predicted results show the most reasonable trend. The rate of increase of spread and the height of the developing wall-spray is predicted to decrease with increased ambient pressure(gas density).

• 한국분무공학회지
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• 제14권1호
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• pp.20-27
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• 2009

In the present work, effects of spray characteristics (droplet size and velocity) on the temperature variation of a heated porous plate (Melamine foam) have been investigated through a series of experiments. Based on the measured data, time required to cool down the hot porous material turned out to be shorten by doing with the smaller droplet size and/or smaller impinging velocity. In particular, the droplet size effect is more prominent than the impinging velocity. The cooling performance in the porous material is directly proportional to the penetration velocity.

• 대한기계학회논문집B
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• 제25권5호
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• pp.627-633
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• 2001

Characteristics of a diesel spray impingement with the variation of ambient temperature, wall temperature and ambient pressure were investigated through shadowgraphy method by using high speed camera. The radial penetration of spray was increased with ambient temperature and wall temperature. It is resulted from the decrease of ambient gas density caused by the increase of temperature. The height of spray was also increased with ambient temperature and wall temperature, because the height of stagnate region is noticeably increased, although height of wall jet vortex is decreased. At the same ambient pressure, the area ratio of impinging spray of room temperature environment to high temperature environment was increased, as the temperature difference between room temperature and high temperature increases. And the increment of area ratio was higher at low ambient pressure than high ambient pressure.

• 한국분무공학회지
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• 제10권3호
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• pp.1-8
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• 2005

The purpose of this study is to investigate the internal structure of the impinged diesel spray at various experimental conditions. To examine the effect of various factors on the development of a diesel spray impinging on the wall, experiments were conducted at the various Injection pressures, wall distances from the nozzle tip and angles of wall inclination. The PIV system consists of a double pulsed Nd:YAG laser was utilized to analyze the internal flow structure of impinged diesel sprays. The velocity fields from the PIV system were compared with the results measured by the phase Doppler particle analyzer(PDPA)system. The results show that internal flow pattern of the impinged spray was similar with the results from the PDPA system. The radial velocity of the impinged spray was increased with the increase in the injection pressure and near the nozzle-wall distance. The generation of vortex was also promoted with the Increase in angles of wall inclination.

• 한국추진공학회지
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• 제25권4호
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• pp.53-58
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• 2021

대체모델을 사용한 탄화수소계열 혼합유체를 아임계 및 초임계 상태에서 이중 충돌 분무를 통해 분무 메커니즘을 가시화하여 분석하였다. 임계압력과 온도가 다른 데칸과 메틸사이클로헥산을 대체모델로 선정하였다. 챔버 내부에 이중 충돌 인젝터를 설치하여 아임계 및 초임계 상태에서 고속카메라를 통해 분무를 가시화하였다. 혼합유체의 분사 및 챔버 환산압력은 Pr(P/P_c)=1로 유사하게 유지하였으며 Tr(T/T_c)은 0.48에서 1.02까지 증가시켰다. Tr이 증가할수록 혼합유체의 물성치가 각각의 임계점에 도달하여 분무각은 증가하고 시트분열길이는 감소하였다. 또한 혼합 유체가 모두 근임계점에 도달하였을 때 이중 충돌 분열 메커니즘에서 벗어나 밀도 구배의 변화가 크게 관측됨을 보였다.

• 한국자동차공학회논문집
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• 제11권3호
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• pp.77-84
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• 2003

It is an aim of this study to perform extensive numerical study for analyzing the anisotropic turbulence effects on spatial and temporal behaviors of diesel sprays after wall impingement. The turbulence model of Durbin is used for comparisons with the $k-\varepsilon$ model. The turbulence-induced dispersions of droplets are considered to describe the anisotropy of turbulence effectively and the spray/wall interactions are simulated using the model of Lee and Ryou. The present study investigates the internal structures of impinging diesel sprays such as Sauter mean diameter (SMD), loca1 droplet velocities, and local gas velocities and also compares the results predicted by two turbulence models with the experimental data. The Durbin's model considering the anisotropy of turbulence predicts both gas and droplet tangential velocities better than the$k-\varepsilon$ model does. It is concluded that the anisotropy of turbulence should be considered in simulating impinging diesel sprays.

• 한국분무공학회지
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• 제9권1호
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• pp.37-42
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• 2004

In a port fuel injection system of engine, a large part of fuel injected into an intake port adheres on its wall and inlet valve. Consequently, the wall impinging spray interaction might occur the generation of several harmful phenomena. There are uncontrollable mixture formation, an accidental backfire and unburned hydrocarbons. Therefore, it is important to analyze the fuel behavior during the spray-wall interaction. In this study, splash characteristics of impingement and reflecting or scattering behavior of droplets of fuel injected from EFI nozzle were studied experimentally. A test fuel used is LAWS and its physical characteristics are similar to the conventional gasoline except for the ignition point. Since the liquid film formed immediately after impinging on an impingement plate is unstable, it is easy to cause secondary disintegration. In addition, when the intermittently impingement on the impingement plate with LAWS, the splash ratio is around 0.6. If an injection period becomes longer, liquid film will become thick and the splash ratio will fall bout 10 percent. On the other hand, when the injection period of an intermittent spray is long, the same time lapse as a continuous spray is shown.

• 한국추진공학회지
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• 제4권1호
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• pp.36-45
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• 2000

지금까지의 충돌분무에 대한 연구는 제트의 충돌시 형성되는 액막의 분열 과정을 이해하고 이를 모델링하는데 초점을 두어왔기 때문에 실질적으로 연소 효율에 가장 큰 영향을 미치는 연료의 공간분포 특성에 대한 연구가 부족하였다. 따라서 본 연구에서는 like-doublet 충돌분사 노즐을 사용하여 연료 유량 플럭스의 단면분포 특성을 연구하였다. PDPA(Phase Doppler Particle Analyzer)를 통해 액적의 크기를 측정한 기존의 방법은 연료의 평면적인 분포특성을 이해하는데 상당히 제한적이었기 때문에 평면 레이저 유도형광기법(PLE : Planar Laser Induced Fluorescence)을 이용하여 분무의 단면 분포를 측정하였고, 직접사진을 통하여 액적의 크기도 측정하여 PLIF의 결과와 비교하였다.