• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.3
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• pp.204-211
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• 2019

The analysis on two-phase flow in a Lean Direct Injection(LDI) combustor has been investigated. Linearized Instability Sheet Atomization(LISA) and Aerodynamically Progressed Taylor Analogy Breakup(APTAB) breakup models are applied to simulate the droplet breakup process in hollow-cone spray. Breakup model is validated by comparing penetration length and Sauter Mean Diameter(SMD) of the experiment and simulation. In the LDI combustor, Precessing Vortex Core(PVC) is developed by swirling flow and most droplets are atomized along the PVC. It has been confirmed that all droplets have Stokes number less than 1.0.

• Tribology and Lubricants
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• v.2 no.2
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• pp.12-19
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• 1986

Using emulsion lubricant whose cooling effect and incombustibility are good and which is economical, I investigated lubricative mechanism and the behavior of scattered particles in the elastic fluid lubrication region with the line contact between rollers and plates and the light interference system. The results of the study are as follows: (1) The flow in the squeeze oil film is considered as comparatively wide clearance and narrow one, and in the former case the effect of the distribution of particles and the velocity on the flow. In the latter case, emulsion particles stay in the clearance an the oil film changes with the decrease of the oil film thickness. (2) In the wide clearance the velocity difference of the flow O/W or W/O emulsion is inverse proportional to the particle size. In the narrow clearance the distribution of the remained drops is different from one another and the scattered particles change more easily in O/W type than in W/O type. (3) At the beginning of the EHL the stagnation region with slow flowing velocity exists and the behavior at the region is different depending on the particle size. (4) By observing the dischromatic light interference line, emulsion oil passing through EHL region and the crack behavior at the beginning of EHL were found.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.6
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• pp.1613-1620
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• 1990

For the purpose of the study on the spray characteristics of a coaxial nozzle, the measurement of the velocity and size of droplets, concentration, and the statistical correlation coefficient between the fluctuation of the velocity and that of the corresponding drop diameter have been carried out. Various method of simultaneous measurement of velocity and drop size have been developed from LDV techniques. The technique used here belongs to the method that supposed by Yule, Holve and Self. It has the advantages of making use of a standard LDV apparatus to which minor modifications have been brought, photomultiplier is equipped with a slit instead of a pinhole and observed the measuring volume at an angle of 90.deg.. The voltage supplied by the photomultiplier has undergone an appropriate analog and digital processing. The experimental results give a good idea of the two phase flow organization and can be helpful to find a drop diffusion model when suitable data are imput.

• Proceedings of the KAIS Fall Conference
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• 2012.05a
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• pp.356-359
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• 2012

SNCR 기술은 SCR에 비해 탈질 효율은 떨어지지만 촉매없이 고온 배출가스에 NH3 또는 요소수를 직접 분사하여 질소와 물로 환원시키는 방법이므로 초기 투자비 및 운영비가 적어 최근 국내 대다수의 소각장, 산업용 보일러 등에 널리 적용되고 있다. 단, SNCR 기술은 급격한 온도 강하나 접근의 불용이성, 불균일한 혼합, 액적의 증발시간 지연, 불균일한 운전 조건 등의 영향을 크게 받으며, 특히 반응 온도가 가장 중요한 변수로서 최적 반응 온도 영역대가 약 800~$1,000^{\circ}C$라는 점에서 이상적인 반응 온도 조건을 찾아서 환원제를 분무하는 것이 매우 중요하다. 이에 본 연구에서는 열유동 전산해석을 통해 스토커식 소각로의 폐기물 성상별 화염 온도 분포를 예측하고 적정 반응 온도 영역을 확인하여 요소수 주입 고도를 선정, 폐기물 성상별 분무 조건을 확립하고자 수치 해석적 연구를 수행하였다. 폐기물 성상(고질/중질/저질 폐기물)별로 화염 온도를 예측한 결과, 최적 반응 온도 영역대가 약 800~$1,000^{\circ}C$, 폐기물 성상의 심한 변화 때문에 소각로의 효율적인 연소 조건 제어에 어려움 등을 고려하여 약 700~$1,000^{\circ}C$ 온도 영역대를 환원제 분무 온도로 선정하였다. 폐기물별로 발열량에 따른 화염 온도가 모두 다르기 때문에 환원제 분무 위치를 3지점으로 선정하여 각 지점별로 분무 운전 조건을 확립하였다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.1
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• pp.18-25
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• 1984

The transition boiling of a liquid droplet on a heated flat surface was studied utilizing Kotake's model with the effects of viscosity of a thin vapor layer between the droplet and the hot plate taken into account. This problem was analyzed considering the process of the droplet evaporation which resulted in hydrodynamic instability at the liquid-vapor interface. The results of the study are as follows; (1)The effect of the viscosity in the vapor layer at the interface appears as a dimensionless number N, namely .sigma. .delta.$_{0}$ /.rho.nu.$^{2}$ (2)The time required for evaporation at the transitional region increases with the temperature difference ratio .DELTA. T$_{r}$. The rate of increase of the total evaporation time becomes larger as increasing of N$_{m}$(N number at maximum heat flux) increases.s.

• Journal of ILASS-Korea
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• v.13 no.3
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• pp.143-148
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• 2008

In the present study, the correlation between the Nusselt number and Reynolds number was developed for forced convection and nucleate boiling region in spray cooling. Also the effect of droplet subcooling on spray cooling heat transfer was investigated. Full cone spray nozzles were employed for spray cooling experiment, and water and FC-77 were used for developing the correlation. From the experimental results, the correlation between the Nusselt number and Reynolds number based on droplet-flow-rate was developed. The correlation shows good predictions with ${\pm}30%$ error for water and FC-77.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.83-88
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• 2007

The spray characteristics and liquid column penetration of steady and pulsed injection measurements have been experimentally studied using high speed camera in liquid jets injected into subsonic crossflow. The objectives of this research are to comparison the spray characteristics of steady injection with pulsed injection. Moreover. the effects of frequency are also studied. As the result, This research has been showed that pulsed injection has different penetration compared with steady injection.

• Journal of ILASS-Korea
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• v.3 no.1
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• pp.34-42
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• 1998

The correlation between the droplets size and the velocity are investigated for an intermittent spray of the pintle type fuel injector employed in a port injection gasoline engine. The analysis such as the mean droplet size, SMD, and velocity under the fixed injection period and varied fuel pressures are conducted utilizing PDPA systems. As results, the experimental data obtained, show that the larger droplet sizes. the higher velocities during the spray tip arrival time, and that at Z=70mm, r=8mm, both droplet sizes and velocities are peak. At the upstream, flow of droplets are dominated by injection pressure, which are more effected inertia force of droplets at the downstream of Z=70mm.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1481-1486
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• 2004

This report presents experimental results on the heat transfer coefficients in the boiling region of spray cooling for actual metallurgical process. In this study, the heat flux distribution of a two dimensional dilute spray impinging on hot plate was experimentally investigated. Based on the experimental results, they classified the heat transfer area into the stagnation region and wall-flow region. In the stagnation region, the local heat transfer coefficient relates mainly to the droplet-flow-rate supplied from spray nozzle directly, so the local heat transfer coefficients is good agreement with the predicted values from correlation for spray cooling proposed by former report However, the local heat transfer coefficient in wall-flow region is larger than predicted values, and it is found that the rebounding droplets-flow-rate must be accurately evaluated to predict the local heat transfer coefficient in this region.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.7
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• pp.94-103
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• 1999

A model for the prediction of combustion and exhaust emissions of DI diesel engine has been formulated and developed . This model is a quasi-dimensional phenomenological one and is based on multi-zone combustion modelling concept. It takes into consideration, on a zonal basis ,detailed of fuel spray formation, droplet evaporation, air-fuel mixing, spray wall interaction, swirl , heat transfer, self ignition and burning rate . The emission model is considered with chemical equipment , as well as the kinetics of fuel. NO and soot reactions in order to calculate the pollutant concentrations within each zone and the whole of cylinder . The accuracy of prediction versus experimental data and the capability of the model in predicting engine heat release, cylinder pressure and all the major exhaust emissions on zonal and cumulative basis., is demonstrated. Detailed prediction results showing the sensitivity of the model bv various injection rates are presented and discussed.