• Title/Summary/Keyword: 충돌분무

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Numerical Analysis of Geometric Effects on Spray Characteristics in Small Direct-injection Diesel Engines (소형디젤기관 내 충돌부의 기구학적 조건에 대한 분무특성의 수치적 해석)

  • 류성목;차건종;김덕줄;박권하
    • Transactions of the Korean Society of Automotive Engineers
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    • v.7 no.5
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    • pp.55-65
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    • 1999
  • Many researches have been investigating small direct-injection diesel engines using the spray impacting on walls. Those systems have one or more raised pips to break-up the fuel and spread it widely toward a desired direction in a combustion chamber. In this study, the sizes and heights of the pips are determined by using a computational fluid dynamics code employing non-orthogonal grid systems. In order to find out the suitable pip-shape to a small chamber, the spray behaviors, occupied spary volumes and averaged droplets sizes are calculated with the variation of shape of the pip, such as, size and heights and inclined degree. The desired shape of the impinging land is proposed for the design of combustion system in small diesel engines.

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Spray Patterns and Atomization Characteristics of Viscoelastic Fluid with Impinging Jet (점탄성 유체에 따른 충돌분무의 분무패턴 및 미립화 특성)

  • Lee, Mun Hee;Hong, Jung Goo
    • Journal of ILASS-Korea
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    • v.24 no.3
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    • pp.145-151
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    • 2019
  • Viscoelastic fluid is used in various industrial sites because its cost reduction and environmental benefits by preventing formation of fine droplets that scattered around. However, viscoelastic fluids, unlike newtonian fluids, contain a shear thinning characteristic that decrease in viscosity as shear rate increases and elastic characteristic, making it difficult to predict spray breakup process. In this study we made three test fluids. Boger fluid with viscoelastic characteristics, and two newtonian fluids, were prepared to exclude shear thinning characteristics and study the effects of elastic characteristic only. Flow visualization, spray angle, and SMD were measured for three test fluids using laboratory scale impinging jet test apparatus. As a result, it was confirmed that Boger fluid, unlike the newtonian fluid, was not formed fine droplets that scattered around and the breakup process appeared differently. In addition, SMD was found to be large in Boger fluid, and the SMD according to pressure was confirmed that there is no significant difference.

액체 로켓용 충돌형 인젝터의 분무분포 특성에 관한 실험적 연구

  • 정기훈;윤영빈;황상순
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 1999.10a
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    • pp.3-3
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    • 1999
  • 액체 연료 로켓엔진의 인젝터에 대한 연구는 연소 효율과 안정성 향상에 초점을 두어왔다. 그 중 충돌분사형 인젝터는 구조가 매우 간단하면서 많은 유량의 연료를 분사시킬 수 있기 때문에 개발 초기부터 많은 연구가 이루어졌으며 실제 여러 엔진에 응용된 바 있다. 그동안의 충돌분무에 대한 연구는 주로 제트의 충돌시 생기는 액막의 분열 과정을 이해하는 데에 관심이 있어 왔으며, 아직까지는 실험적 기법에 기초하여 근사적인 분열 모델을 제시하는 데에 그치고 있다.

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Behavior of a Diesel Spray Impinged on a Wall (벽면에 충돌하는 디젤분무의 거동)

  • Cho, I.Y.;Oh, J.H.
    • Journal of ILASS-Korea
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    • v.2 no.4
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    • pp.1-6
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    • 1997
  • In the case of analyzing the combustion phenomena in a small high speed DI diesel engine, one demands the experimental results of the impinging spray on the wall as a basic characteristics. In the experiments presented here, diesel fuel oil was injected into a high pressure chamber in which compressed air at room temperature was charged. The single spray was impinged on a flat wall. The growth of the spray was photographed with transmitted light or scattered light. The effect of the spray axis angle to the wall on the impinging spray was revealed. Finally, the experimental results was presented, that is, the radius and height of the impinging spray was influenced by above mentioned variable.

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Analysis of the False Diffusion Effects in Numerical Simulation of Diesel Spray Impinging on Inclined Walls (경사진 벽충돌 디젤 분무에 대한 수치해석에서 오류확산이 미치는 영향)

  • Gwon, H.R.;Lee, S.H.
    • Journal of ILASS-Korea
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    • v.13 no.1
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    • pp.22-27
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    • 2008
  • The false diffusion occurs generally when the flow is oblique to the grid lines and when there is a non-zero gradient of the dependent variable in the direction normal to the flow. This numerical problem can overestimate diffusion terms in the continuous phase, causing the numerical inaccuracy for the simulation of impinging sprays on inclined walls because most of spray calculation uses rectangular grid system. Therefore, the main objective of this article is to investigate numerically the influence of false diffusion on numerical simulation for spray-wall impingement on inclined walls. It is found that unlike the spray impingement normal to the wall, the numerical diffusion exists in the case when diesel sprays impinge on the inclined walls with different angles. The results show that the correction function should be considered for accurate prediction of spray penetration length and more elaborate numerical schemes should be utilized to reduce the false diffusion.

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A Study on Areas of Application of a Extended Collision Model in a Wall Impaction Spray Calculation (벽면충돌분무 계산에서 확장충돌모델의 적용범위에 관한 고찰)

  • Park, Gwon-Ha;Jeong, Chang-Hwa
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.25 no.8
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    • pp.1013-1020
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    • 2001
  • This paper addresses to the area where the extended collision model is applied. In order to find the optimum shape of wall sprays, the extended model is applied to the nearest cells of just over the impaction wall, spray core or over all. The droplet distribution, wall spray radii, heights and gas flows are shown in all the cases. Those results show that the best spray shape represents in the case applying the extended model just on the impinging wall.

Spray Characteristics Depending Upon Impaction Land Surface Angle Variations (충돌면 경사각도 변화에 따른 분무특성)

  • Kim, C.H.;Kim, J.H.;Park, K.H.
    • Transactions of the Korean Society of Automotive Engineers
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    • v.6 no.6
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    • pp.63-71
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    • 1998
  • In a diesel engine the phenomenon of spray impaction on a combustion 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 impaction 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 angle variations of the impaction land sufrace prepared for the injection spray is analysed as a simulative manner. The spray dispersions, vapor distributions and flow fields are compared with impacting angle variation. The results show more angle give more vapor distribution until $15^{\circ}$.

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A Pseudo 3-Dimensional Structure of the Liquid-propellant Spray Emerging from Nonimpinging-type Injector (비충돌형 인젝터로부터 발생하는 액체추진제 분무의 준3차원 구조)

  • Jung, Hun;Kim, Jeong-Soo;Park, Jeong
    • Journal of the Korean Society of Propulsion Engineers
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    • v.14 no.6
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    • pp.17-24
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    • 2010
  • This study was performed to make a close inquiry into a pseudo 3-dimensional structure of the liquid-propellant spray emerging from nonimpinging-type injector. Spray configuration near the injector exit was captured by a high-speed camera, and then its periodic phenomena (shedding) was observed. Detailed spatial structure of spray was investigated by spray characteristic parameters (velocity, diameter, volume flux, etc.) with the aid of a Dual-mode Phase Doppler Anemometry (DPDA). Experiment was carried out at various locations along the geometric axis of the nozzle orifice and on the plane normal to the spray stream with the injection pressures of 17.2 to 27.6 bar.

Spray Characteristics of Impinging Injectors in Crossflows (횡방향 유동에서 충돌형 분사기의 액체제트 분무 특성)

  • Song, Yoonho;Lee, Woongu;Ahn, Kyubok
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2017.05a
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    • pp.949-952
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    • 2017
  • Spray characteristics of the impinging injectors in subsonic crossflows were experimentally studied and compared with the plain-orifice injectors. By changing the impingement angle (60, 90, 120) which is the same orifice length to diameter ratio (L/d = 5), spray characteristics were investigated. In the view of the top view from the impinging injectors, as the impingement angle increases, the liquid column breakup length in the y-direction was decreased. On the other hand, when the impinging injector is viewed from the side view, the breakup length in the x direction is smaller than the previous plain-orifice injectors, which mean that the atomizing performance of the impingement-type injector is better than that of the single-hole orifice.

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