• Title/Summary/Keyword: 충돌분사

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Simulation of Spray Behaviors by Injection Rate Shapes in Diesel Injection System (분사율 형상에 따른 디젤분사계의 분무거동에 관한 시뮬레이션)

  • Wang, W.K.;Jang, S.H.;Koh, D.K.;Ahn, S.K.
    • Journal of Power System Engineering
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    • v.3 no.3
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    • pp.36-43
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    • 1999
  • Many of thermodynamic-based diesel combustion simulations incorporated a model of fuel spray which attempts to describe how the spray develops according to time. Because the spray geometry is an essential aspect of the fuel-air mixing process, it is necessary to be calculated quantitatively for the purpose of heat release and emission analysis. In this paper, we proposed the calculating method of non-evaporation spray behaviors by injection rate shapes under actual operating conditions of diesel engine. We confirmed the utility of this calculating model as the calculated results were compared with the measured results. This calculating program can be applied usefully to study on the diesel spray behavior.

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분사액체와 운용조건이 공기충돌형 인젝터에 의해 형성되는 액적의 분무특성에 미치는 영향

  • Park, Seung-Gyu;Han, Jae-Seob;Kim, Yoo;Kim, Sun-Jin;Park, Jung-Bae
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 1999.04a
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    • pp.8-8
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    • 1999
  • 2-유체 인젝터의 분무연소에 대한 통찰 및 구조에 대한 이해와 연료-공기 혼합과 연소반응의 물리적 이해에 필요한 수치적 모델의 개발 및 검증을 위해서는 2유체 시스템에서 액체 및 기체 각각의 기본적 특성인 액적크기, 액적속도, 액적의 질량플럭스(flux), 가스상의 속도측정 등이 필요하다. 특히, 액체분무에서는 액적의 크기를 예측하는 것이 매우 중요한 과제이며, 액적의 크기에 영향을 주는 인자들로는 노즐의 형태, 분사액체의 물성치(점도, 표면장력, 밀도), 주위기체의 조건(온도, 압력, 응축과 증발현상), 분사압력 등이 있다. 그러나, 실제 분무액적의 크기는 분포를 가지므로 같은 SMD를 가지더라도 그 분포의 정도는 크게 다를 수 있어 결과적으로 분무액적의 크기를 평균값만으로 표현하는 것은 불충분할 뿐만 아니라 그 적용에도 한계를 가지게 된다. 따라서 분무액적의 평균크기와 함께 그 분포의 정도 등을 함께 나타내려는 시도가 많은 과학자들에 의하여 연구되었다.

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An experimental study on cooling characteristics of mist impinging jet on a flat plate (평판에 분사된 분무충돌제트의 냉각특성에 대한 실험적 연구)

  • Jun, Sang-Uk;Chung, Won-Seok;Lee, Joon-Sik
    • Proceedings of the KSME Conference
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    • 2001.06d
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    • pp.528-533
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    • 2001
  • An experimental study is carried out to investigate the effects of air and water mass flow rates on cooling characteristics of mist impinging jet on a flat plate. Experiments are conducted with air mass flow rates from 0.0 to 3.0 g/s, and water mass flow rates from 5.0 to 20.0 g/s. An air-atomizing nozzle is used for the purpose of controlling air and water mass flow rates. In this study, a new test section is designed to obtain local heat transfer coefficient distributions. Heat transfer characteristics of the mist impinging jet are explained with the aid of flow visualization. Surface temperature and heat transfer coefficient distributions become more uniform as air mass flow rate increases, and that the increases in water flow rate mainly enhance cooling performance. Air mass flow rate weakly influences averaged heat transfer coefficient when water mass flow rate is low, but averaged heat transfer coefficient increases remarkably as air mass flow rate in case of high water mass flow rate.

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Numerical Study on Impingement Process and Fuel Film Formation of GDI Spray according to Wall Geometry under High Ambient Temperature (고온에서 벽면 형상에 따른 GDI 분무의 충돌 과정 및 연료 액막 형성에 대한 수치적 연구)

  • Shim, Young-Sam;Choi, Gyung-Min;Kim, Duck-Jool
    • Transactions of the Korean Society of Automotive Engineers
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    • v.16 no.2
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    • pp.166-174
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    • 2008
  • Numerical study on the impingement process and the fuel film formation of the hollow-cone fuel spray was conducted under vaporization condition, and the effect of the wall cavity angle on spray-wall impingement structure was investigated. A detailed understanding of this phenomena will help in designing injection systems and controlling the strategies to improve engine performance and exhaust emissions of the Gasoline Direct Injection (GDI) engine. The improved Abramzon model was used to model the spray vaporization process and the Gosman model was adopted for modeling of spray-wall impingement process. The calculated results of the spray-wall impingement process were compared with experimental results. The velocity field of the ambient gas, the Sauter Mean Diameter (SMD) and the generated fuel film on the wall, which are difficult to obtain by the experimental method, were also calculated and discussed. It was found that the radial distance after the wall impingement and the SMD decreased with increasing the cavity angle and the temperature.

An Experimental Study on Cooling Characteristics of Mist Impinging Jet on a Flat Plate (평판에 분사된 분무충돌제트의 냉각특성에 대한 실험적 연구)

  • Jun, Snag-Uk;Jung, Won-Seok;Lee, Joon-Sik
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.27 no.4
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    • pp.511-517
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    • 2003
  • An experiment is conducted to investigate the effect of air and water mass flow rates on cooling characteristics of mist impinging jet on a flat plate. The air mass flow rate ranges from 0.0 to 3.0 g/s, and water mass flow rates from 5.0 to 20.0 g/s. An air-atomizing nozzle is used fur the purpose of controlling air and water mass flow rates. The test section is designed distinctively from previous works to obtain local heat transfer coefficient distributions. Heat transfer characteristics of the mist impinging jet are explained with the aid of flow visualization. Surface temperature and heat transfer coefficient distributions become more uniform as air mass flow rate increases. The water flow rate provides substantial contribution to enhancement of cooling performance. On the other hand, The air mass flow rate weakly influences the averaged heat transfer rate when the water mass flow rate is low, but the averaged heat transfer rate Increases remarkably with the air mass flow rate in case of the high water mass flow rate.

Three-Dimensional Flow Characteristics of a Circular Impinging Jet Normally Oriented to Crossflow (주유동에 수직으로 분사되는 원형 충돌제트의 3차원 유동특성)

  • Lee, Sang Woo;Jeong, Chul Hee
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.22 no.12
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    • pp.1735-1745
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    • 1998
  • Oil-film surface flow visualizations and three-dimensional flow measurements using a straight five-hole probe have been conducted for a circular impinging jet which is normally oriented to the crossflow in a channel. Throughout the experiments, the ratio of channel height to injection hole diameter, H/D, is fixed to be 1.0, and blowing ratio is varied to be 1.0, 2.0, 3.0 and 4.0. From the surface flow visualizations for both top wall(target plate) and bottom wall, impinging jet region on the target plate can be clearly identified, and for the small value of H/D = 1.0, presence of the bottom wall changes the near-hole flow structure, significantly. The three-dimensional flow measurements show that in the dawnstream region of the injection hole, there exist a pair of counter-rotating vortices, called "scarf vortices", and the strength of the vortices strongly depends on the blowing ratio. In addition, a new flow model in the flow symmetry plane has been proposed for H/D = 1.0.

Study of Spray Droplet/Wall Interaction (분무액적과 벽의 상호작용에 대한 연구)

  • 양희천;유홍선;정연태
    • Transactions of the Korean Society of Automotive Engineers
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    • v.6 no.4
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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).

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Experimental study of combustion stability assessment of injector (분사기의 연소 안정성 평가를 위한 실험적 방법 연구)

  • Seo, Seong-Hyeon;Lee, Kwang-Jin
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.32 no.4
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    • pp.61-66
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    • 2004
  • The objective of the present study is to develop methodology for the assessment of combustion stability of liquid rocket injectors. To simulate actual combustion occurring inside of a thrust chamber, a fullscale injector has been employed in the study, which bums gaseous oxygen and mixture of methane and propane. The main idea of the experiment is that the mixing mechanism is considered as a dominant factor significantly affecting combustion instability in a fullscale thrust chamber. A single split triplet injector has been used with an open-end cylindrical combustion chamber. The characteristics revealed by excited dynamic pressures in gaseous combustion show degrees of relative acoustic damping depending on operating conditions. Upon test results, the direct comparison between various types of injectors can be realized for the selection of the best design among prospective injectors.

The Size Analysis of Raised Lands Prepared for Spray Impaction in OSKA Typed D.I. Diesel Engine Combustion Chamber (OSKA형 디젤기관 연소실의 충돌면 크기 분석)

  • 김재휘;홍영표;박권하
    • Journal of Advanced Marine Engineering and Technology
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    • v.20 no.3
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    • pp.82-90
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    • 1996
  • In a diesel engine the phenomenon of spray impaction on a chamber wall has been taken as an undesirable matter because of the deposition of fuel on the surfaces, and the subsequent slow evaporation and mixing with air resulting in unburned hydrocarbons. Therefore many researches have concentrated on avoiding fuel impingement on surfaces. On the contrary done a number of studies using spray wall impactions in a positive way, which makes the droplets smaller, changes the direction into free spaces far from the wall and also improves mixing with air. In this paper the size of the impaction site prepared for the injection spray which is raised from the bottom in the piston bowl center is analysed as both simulative and experimental manner.

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