• 제목/요약/키워드: Spray impingement

검색결과 112건 처리시간 0.026초

비등방성 난류특성을 고려한 분무의 벽면충돌 현상에 대한 수치해석 연구 (Numerical Study of Impinging Sprays Considering Anisotropic Characteristics of Turbulence)

  • 고권현;유홍선;이성혁
    • 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.

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

  • 왕우경;장세호;고대권;안수길
    • 동력기계공학회지
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    • 제3권3호
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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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유동가속부식으로 인한 급수가열기 동체 감육현상 규명과 완화 방안 및 충격판 설계개선에 관한 연구 (A Study on the Shell Wall Thinning by Flow Acceleration Corrosion and Mitigation Plan and Design Modification of a Feedwater Heater Impingement Baffle)

  • 김경훈;황경모;김인태
    • 한국분무공학회지
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    • 제15권2호
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    • pp.83-93
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    • 2010
  • Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damage, which will increase as operating time progresses. Several nuclear power plants in Korea have experienced wall thinning damage in the area around the impingement baffle inside feedwater heater installed downstream of the turbine extraction stream line. At that point, the extract steam from the turbine is two phase fluid at high temperature, high pressure, and high speed. Since it flows to reverse direction after impinging the impingement baffle, the shell wall of feedwater heaters may be affected by flow-accelerated corrosion. In this paper, to compare degree of shell wall thinning mitigation rate to squared type with mitigation rate of other type baffle plate, four different types of impingement baffle plate-squared, curved, mitigating type and multi-hole type-applied inside the shell. With these comparison data, this paper describes operation of experiments and numerical analysis which is composed similar condition with real feed water heater. And flow visualization is operated for verification of experiments and numerical analysis. In conclusion, this study shows that mitigating type and multi-hole type baffle plate are more effective than other baffle plate about prevention of pressure concentration and pressure value decrease.

충돌제트로 생성되는 분무의 특성에 관한 연구 (A Study on the Characteristics of the Spray Produced by Two Impinging Jets)

  • 강보선
    • 한국분무공학회지
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    • 제2권4호
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    • pp.22-28
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    • 1997
  • In this paper an experimental study of a spray created by two impinging jets is presented utilizing a novel two-reference-beam double-pulse holographic technique. Visualization of the overall spray pattern as well as measurements on the size and velocity of the droplets were performed with the special emphasis on the effect of physical properties of liquids. The overall spray pattern clearly revealed the inherent wave nature In the disintegration process of this type of atomization. The structure of liquid elements near the impingement point is indicative of the mechanisms of the disintegration process. Surface tension plays an important role in the droplet size without any noticeable effect on the spray pattern, whereas viscosity affects the structure without any significant effect on the droplet sire. The droplet velocities were not affected by liquid properties.

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경사노즐 선회분사기의 가솔린 분무 특성 (The Gasoline Spray Characteristics of Tapered Nozzle for a Swirl Injector)

  • 문석수;최재준;배충식
    • 한국분무공학회지
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    • 제12권1호
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    • pp.11-17
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    • 2007
  • The swirl spray for direct-injection spark-ignition (DISI) engines was investigated using a nozzle whose exit surface shape was cut with a certain tapered angle. The reason for the change in spray's characteristics at various tapered angles was explained by the data correlating the taper and flow angles. The spray tended to shift its characteristics from the symmetric to asymmetric when the tapered angle was increased; furthermore, the spray penetration and spray cone angle were also increased. When the tapered angle was greater than the $90^{\circ}$ minus flow angle, an opened hollow cone spray was formed because of the fuel impingement against the tapered surface area of the nozzle exit. This behavior indicates that the reduction in the air pressure difference between the inner and outer spray of the spray can be achieved. This behavior also promises the potential use of the tapered nozzle for the case where the independence of the spray performance from atmospheric pressure and fuel temperature is desired.

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충돌 제트로 형성되는 분무의 속도 특성에 대한 연구 (A Study on the Velocity Characteristics of the Spray Formed by Two Impinging Jets)

  • 추연준;서귀현;강보선
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 춘계학술대회논문집E
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    • pp.87-93
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    • 2001
  • In this study, the velocity characteristics of liquid elements formed by two impinging jets is analysed using double pulse image capturing technique. For the droplets formed by low speed impinging jets, the droplet velocities are higher with smaller azimuthal and impingement angle. The maximum droplet velocities are about 25 % lower than jet velocity. With an increase of azimuthal angle, the shedding angles increases but remains lower than azimuthal angle. The velocities of ligaments formed by high speed impinging jets gradually decreases with an increase of azimuthal angle. The maximum ligament velocities are about 40 % lower than jet velocity. Higher impingement angles produce lower ligament velocities. The shedding angles of ligament almost increases with the same value of azimuthal angle, which implies that the moving direction of ligaments is radial from the origin as the impingement point.

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충돌분류에 의한 액적의 크기 및 속도특성에 관한 실험적 연구 (An Experimental study on the drop size and velocity characteristic of drop by impinging jets)

  • 한재섭;김선진
    • 한국분무공학회지
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    • 제4권4호
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    • pp.30-37
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    • 1999
  • The breakup characteristics of liquid sheet formed by the liquid rocket injector has a close relation with the combustion efficiency. In this paper, basic characteristics of droplet size and velocity distribution were measured with PDPA for the Like Doublet Impinging Injector. Test variables were the angle of impact, the diameter of orifice and jet velocity. Water was used as test fluid. As a result, for impingement angle less than 90 degree, following correlations were obtained between drop size and design parameters : $D_{32}({\mu}m)=295.0{\times}V^{-0.09}\times(2\theta)^{-0.1}{\times}d^{0.072}$. For impingement angle greater than 100 degree, drop sizes were increased but eventually converged to a certain limiting value.

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가압 분무실내 스프레이 충돌판에서 나타나는 비정상 열전달 측정에 관한 연구 (An Experimental Study on Unsteady Heat Transfer of Spray-Impinging Plate in a Pressurized Chamber)

  • 조창권;이열;구자예
    • 대한기계학회논문집B
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    • 제24권1호
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    • pp.60-67
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    • 2000
  • An experimental investigation on transient heat transfer phenomena of impinging diesel-spray on a flat plate in a pressurized chamber is carried out. A diesel spray is injected from a single-hole nozzle and impinges to a heated flat plate in the chamber. A fast-response thermocouple installed in the top surface of the plate measures the transient variation of surface temperature of the plate under various conditions of the chamber pressures. Utilizing the semi-infinite model, the temporal variation of the heat flux on the plate is determined. Effects of various parameters, such as vertical distances between the nozzle and the plate, radial distances from the injection-axis, and the chamber pressures, on the heat flux characteristics of impinging diesel-spray are studied.

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

  • 김재휘;홍영표;박권하
    • Journal of Advanced Marine Engineering and Technology
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    • 제20권3호
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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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에폭시 프라이머 도료의 에어리스 스프레이 분사 시간에 따른 팁 노즐 침식마모경향과 분사특성 연구 (A study on the erosive wear of spray tip nozzle by epoxy primer paint impingement and the spraying characteristics)

  • 김진억;조연호;천제일;한명수
    • Corrosion Science and Technology
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    • 제14권2호
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    • pp.59-63
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    • 2015
  • Airless spray which is widely used for painting to ship blocks and hull sides is the coating method for attaching atomized paint material to the substrate using spray tip nozzle with compressed air. When the paint material which has high solid contents such as epoxy primer paint is atomized by passing through spray tip nozzle with high pressure, the nozzle composed of tungsten carbide(WC) undergoes the erosive wear, leading to widening of nozzle hole. The deformation of nozzle hole induces improper spray pattern and coating failures such as finger pattern and sagging because the conditions of spray pump pressure and paint flow rate for developing full spray pattern are changed. In this study, an appropriate replacement cycle of spray tip was predicted by measuring the erosive wear tendency as increasing the spraying time of epoxy primer paint.