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구자예(J. Y. Koo),정홍철(H. C. Chung) 한국자동차공학회 1994 한국 자동차공학회논문집 Vol.2 No.4
Observations on the near-nozzle behavior of an unsteady fuel spray through single cylindrical hole nozzle were made by phase Doopler anemometer and microphotographs. At the edge of the spray, droplet velocities have shown wave-like behavior. The average droplet velocity peaked during needle opening and closing. Droplet sizes tended to be small on the edge of spray. The near-nozzle spray angle taken from the micropho-tographs was time-dependent, even though it increased with gas-to-liquid density ratio as expected. The near-nozzle spray angle was the greatest on the initial stage arid decreased to a relatively constant value after about one third of the total injection duration regardless of the ambient gas conditions. even in the near-vaccum condition. The wider near-nozzle spray angle in the early stage is due to the flow characteri-stics inside the nozzle rather than aerodynamic interactions. However, once the spray was established, aerodynamic interactions are essential in the near-nozzle atomization.<br/>
자동차 헤드램프 세척용 재순환 챔버 노즐의 내부유동이 분무장에 미치는 영향
신정환 ( J. H. Shin ),이인철 ( I. C. Lee ),강영수 ( Y. S. Kang ),김종현 ( J. H. Kim ),구자삼 ( J. S. Koo ),구자예 ( J. Y. Koo ) 한국분무공학회 2011 한국액체미립화학회지 Vol.16 No.2
Atomized liquid jets from the washing nozzle which configured with recirculation chamber for cleaning hot-zone area are accelerated and impinged on the head lamp surface. Cleaning efficiency of head lamp can be increased with injecting washing fluids into the hot-zone area. Experimental and numerical studies with various design parameters were executed to reveal the relations between internal geometry and internal flow in the washing nozzle. Spray structures were fitted with each of the head lamp surfaces and spray nozzles were optimized to the spray pattern. The recirculation chamber induces a recirculation flow and can be decreased the pressures perturbation inside the chamber. Orifice determines the mass flow rate. When the diameter of orifice is excessively large, it showed an unstable spray pattern. As a nozzle exit angle increases, density distributions are separated with two section. Also, as a protrusion length of nozzle exit increases, spray patterns are spread into a large area and density distributions showed unstable trend.
고정빈 ( J. B. Ko ),이관형 ( K. H. Lee ),구자예 ( J. Y. Koo ),전창수 ( C. S. Jeon ),문희장 ( H. J. Moon ) 한국분무공학회 2004 한국액체미립화학회지 Vol.9 No.3
N/A Characteristics of droplet vaporization at high ambient pressures and temperatures which are supercritical conditions is studied numerically by formulating one dimensional vaporization model in liquid dodecane and air. Modified Soave-Redlich-Kwong state equation is used to condider real gas effect. Non-ideal behavior of properties at near critical and supercritical conditions is considered in the high pressure condition. Characteristic spatial distribution of properties with various conditions of pressure and temperature is evaluated in order to understand vaporizing evolution.
박장혁(J. H. Park),홍성태(S. T. Hong),구자예(J. Y. Koo) 한국자동차공학회 1996 한국 자동차공학회논문집 Vol.4 No.3
The measurements of velocities of internal flow in a scaled-up nozzle were made by laser Doppler velocimetry in order to clarify the effect of internal flow on the characteristics of fuel spray. The investigated length to diameter ratio(L/d) of the orifice were 1, 3, 4, 5 and 8, and inlet radius to diameter ratio(ro/d) were 0 and 0.5. Mean and fluctuating velocities and discharge coefficients were obtained at various Reynolds number ranging between 15,000 and 28,000, and L/d ranging between 1 and 8 in sharp and round inlet nozzle. The turbulent intensity and turbulent kinetic en-ergy at exit in a sharp inlet nozzle were higher than that in a round inlet nozzle. For sharp inlet nozzle, fluctuating velocities near exit were decreased with increasing L/d.<br/>
박장혁(J.H.Park),홍성태(S.T.Hong),구자예(J.Y.Koo) 한국자동차공학회 1995 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1995 No.11_2
The measurements of velocities of internal flow in a scaled-up nozzle were made by laser Doppler velocimetry in order to clarify the effect of internal flow on the characteristics of fuel spray. The investigated length to diameter ratio(Ud) of the orifice were 1,3.4,5, and 8 and inlet radius to diameter ratio ( r_ο/d) were 0 and 0.5. Mean and fluctuating velocities and discharge coefficients were obtained at various Reynolds number raging between 15,000 and 28,000, and L/d raging between 1 and 8 in sharp and round inlet nozzle. The turbulent intensity and turbulent kinetic energy in a sharp inlet nozzle were higher than that in a round inlet nozzle. For sharp inlet nozzle, fluctuating velocities near exit were decreased with increasing L/d.<br/> <br/> <br/>
액상부탄 간헐분무의 액적 크기 및 속도 측정과 최적 확률분포 연구
김종현 ( J. H. Kim ),김재욱 ( J. W. Kim ),구자예 ( J. Y. Koo ) 한국액체미립화학회 2000 한국액체미립화학회지 Vol.5 No.1
The characteristics of liquefied butane spray are expected to be different from conventional diesel fuel spray, because a kind of flash boiling spray is expected when the back pressure is below the saturated vapor pressure of the butane(0.23MPa at 298K). The ambient pressure was held at a pressure above(0.37MPa) and below(0.15MPa) the fuel vapor pressure. The axial velocities, radial velocities, and size distributions in butane sprays were measured with PDPA(Phase Doppler Particle Analyzer) system. The PDPA measurement showed a smaller SMD at the 0.15MPa chamber pressure, compared to the 0.37MPa case. Log-hyperbolic density function for the droplets size distribution can be fitted to the experimental results of a liquefied butane spray.
[가솔린엔진] 레이저 회절법을 이용한 축대칭 분무 구조의 공간 분포 변환에 관한 실험적 연구
양승연(S.Y. Yang),이충훈(C.H. Lee),구자예(J.Y. Koo),정석호(S.H. Chung) 한국자동차공학회 1999 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Abel transformation Fourier transformation and onion peeling method tomographically reconstructed spatially resolved liquid volume fractions from a set of line-of-sight laser diffraction measurements for axisymmetric sprays generated from a pintle-type gasoline injector. Spatially resolved liquid volume fractions classified into 32 size groups were translated into number density distributions and equivalent diameters which showed well evaporating characteristics of Sl engine fuel sprays. These data were also obtained from the phase Doppler measurements for the same sprays. The comparison between laseㄱ diffraction measurements and phase Doppler measurements at some spatial measurement points shows that Fourier transformation reconstructs more reasonable spatially resolved characteristics for axisymmetric sprays as well as for asymmetric sprays
김흥열(H. Y. Kim),구자예(J. Y. Koo),나형규(H. K. Na),김창수(C. S. Kim) 한국자동차공학회 1998 한국 자동차공학회논문집 Vol.6 No.5
The high pressure common rail injection system offers a high potential for improving emmisions and performance characteristics in large direct diesel engines. High pressures in the common rail with electronic control allows the fuel Quantity and injection timing to be optimized and controlled throughout a wide range of engine rpm and load conditions. In this study, high pressure supply pump, common rail, pipes, solenoid and control chamber, and nozzle Were modeled in order to predict needle lift, rate of injection, and total injected fuel quantity. When the common rail pressure is raised up to 13.0. MFa and the target injection duration is 1.0 ms, the pressure drop in common rail is about 5.0 MPa. The angle of effec-tive pressurization is necessary to be optimized for the minimum pump drive torque and high pressure in common rail depending on the operating conditions. The characteristics of injec-tion were also greatly influenced by the pressures in common rail, the areas of the inlet and exit orifice of the control chamber.<br/>
횡단유동에서 분사하는 홀형노즐 액체제트의 분열 및 분무특성
조우진(W.J. Cho),이인철(I.C. Lee),황진석(J.S. Hwang),구자예(J.Y. Koo) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
The spray characteristics of liquid jet injected into subsonic cross-flow were investigated experimentally. Droplet sizes were measured using PDPA and Image Express. The nozzle diameter was 0.5 ㎜, and its length-to-diameter ratios (L/D) ranged from 1 to 3. Experimental results indicate that the break-up of liquid jet is distributed by many mechanism that are surface wave, shear vortex, counter rotating pair vortex etc. Spray Characteristics are symmetry according to flow direction, and SMD was increased, after some distance, it was decreased with flow direction. SMD of spray from liquid jet is increased in accordance to liquid jet direction.