• Title/Summary/Keyword: Secondary Atomization

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A Study on the Secondary Atomization Characteristics of Liquid Fuel in the Perforated Throttle Valve (다공 스로틀 밸브에서의 액체 연료의 2차 미립화 특성에 관한 연구)

  • Lee, C.S.;Lee, K.H.;Cho, B.O.;Oh, K.S.
    • Journal of ILASS-Korea
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    • v.1 no.1
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    • pp.55-62
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    • 1996
  • In a fuel injection engine, atomization of liquid fuel and mixture formation process has influenced(or affected) directly on the engine performance and pollutant emission. In this study, the characteristics of fuel spray and the behaviors of secondary atomization developed at the downstream of the valves were investigated using an image processing method. Solid and perforated valves are chosen in order to evaluate the valve performance in terns of air flow rate, valve opening angle and valve shape. Experimental results clearly indicate that the spray atomization quality can be improved by increasing the perforated rat io and the blockage rat io in the perforated valve, the characteristics of spray atomization is improved by using the perforated valve with high perforated rat io and blockage ratio.

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A Study on the Characteristics of Gasoline Engine Performance Equipped with Perforated Throttle Valve (다공 스로틀밸브 장착 가솔린기관의 성능 특성에 관한 연구)

  • Cho, B.O.;Lee, C.S.
    • Journal of ILASS-Korea
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    • v.1 no.2
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    • pp.50-56
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    • 1996
  • In an fuel injection type gasoline engine, atomization of fuel droplet and mixture formation process are very important to understand engine combustion efficiency, and also has influence directly on the decision of engine performance and pollutant emission. In this study, perforated throttle valve instead of solid type throttle valve was developed and equipped to an SPI engine to promote secondary atomization and good droplet-air mixture formation. From the engine performance lest. it was verified that the case of perforated valve kas more advantages in each experimental parameters such as in cylinder gas pressure, mass burnt ratio, fuel consumption rate, and pollutant emission characteristics than that of solid one equipped. No matter what the same perforated valve, there are some distinct results in engine performance characteristics according to the perforate ratio.

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Numerical and Experimental Analysis of Spray Atomization Characteristics of a GDI Injector

  • Park, Sung-Wook;Kim, Hyung-Jun;Lee, Chang-Sik
    • Journal of Mechanical Science and Technology
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    • v.17 no.3
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    • pp.449-456
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    • 2003
  • In this study, numerical and experimental analysis on the spray atomization characteristics of a GDI injector is performed. For numerical approach, four hybrid models that are composed of primary and secondary breakup model are considered. Concerning the primary breakup, a conical sheet disintegration model and LISA model are used. The secondary breakup models are made based on the DDB model and RT model. The global spray behavior is also visualized by the shadowgraph technique and local Sauter mean diameter and axial mean velocity are measured by using phase Doppler particle analyzer Based on the comparison of numerical and experimental results, it is shown that good agreement is obtained in terms of spray developing process and spray tip penetration at the all hybrid models. However, the hybrid breakup models show different prediction of accuracy in the cases of local SMD and the spatial distribution of breakup.

Effects of Perforated Throttle Valve on the Mixture Flow and Secondary Atomization of Fuel Spray (다공스로틀밸브가 혼합기 유동과 연료 분무의 2차 미립화에 미치는 영향)

  • Cho, B.O.;Cho, H.M.;Lee, C.S.
    • Journal of ILASS-Korea
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    • v.1 no.3
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    • pp.60-66
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    • 1996
  • Finely atomized fuel droplet and good mixed mixture plays very important in improving combustion efficiency in an spark ignition engine. And combustion efficiency has influence directly on the engine power, fuel consumption rate and pollutant emission. In this study, perforated throttle valve which has relatively low value of PR has been developed and studied for the purpose of improving those aims. As a result of this study, it has been verified that the perforated throttle valve makes droplet more finely, and also proved that has a function of contributing to form good mixed mixture, especially in mixture preparation system of carburetor or SPI type spark ignition engine.

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The Study on Two-color PIV Algorithm for a Measurement of Droplet Velocity (액적의 속도 측정을 위한 이색 PIV 알고리즘 연구)

  • Lee, K.H.;Lee, C.S.;Oh, S.I.
    • Journal of ILASS-Korea
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    • v.4 no.1
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    • pp.13-18
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    • 1999
  • It has been known that spray characteristics have an important effect on the mixture formation and directly influence the engine performances and the emissions. Up to now, the measurement of droplet size is well developed such as PDPA and PMAS though the behavior of small droplets during secondary atomization is not clear. Particle image velocimetry(PIV), a planar measuring technique, is a very efficient tool for studying complicated behavior and a fast and reliable method to track numerous droplets during injection. In this study, two-color scanning PIV is designed to obtain quasi-instantaneous two dimensional velocity data by using he-ion laser, rotating mirror and beam splitter. This PIV method which has high temporal and spatial resolution provides the information about the small complex droplet behavior.

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Modeling of Atomization Under Flash Boiling Conditions

  • Zeng, Yangbing;Lee, Chia-Fon
    • Journal of the Korean Society of Combustion
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    • v.7 no.1
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    • pp.44-51
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    • 2002
  • This paper presents an atomization model for sprays under flash boiling conditions. The atomization is represented by the secondary breakup of a bubble/droplet system, and the breakup is considered as the results of two competing mechanisms, aerodynamic force and bubble growth. The model was applied to predict the atomization of a hollow-cone spray from pintle injector under flash boiling conditions. In the regimes this study considered, sprays are atomized by bubble growth, which produces smaller SMD#s than aerodynamic forces alone. With decreasing ambient pressures, the spray thickness, fuel vaporization rate and vapor radial penetration increases, and the drop size decreases. With increasing the fuel and ambient temperatures to some extent, the effect of flash boiling and air entrainment completely change the spray pattern.

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Effect of ambient conditions on the spray development and atomization characteristics of a gasoline spray injected through a direct injection system (분위기 조건이 직접 분사식 가솔린 분무의 발달 과정 및 미립화 특성에 미치는 영향)

  • Ha, S.Y.
    • Journal of ILASS-Korea
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    • v.10 no.4
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    • pp.47-53
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    • 2005
  • This paper presents the effects of ambient pressure on atomization characteristics of high-Pressure injector in a direct injection gasoline engine both experimentally and numerically. The atomization characteristics such as mean droplet size, mean velocity, and velocity distribution were measured by phase Doppler particle analyzer. The spray development, spray penetration, and global spray structure were visualized using a shadowgraph technique. In order to investigate the atomization process numerically, the LISA-DDB hybrid model was utilized. This breakup model assumes that the primary breakup occurs when the amplitude of the unstable waves is equal to the radius of the ligament of liquid sheet near the nozzle and the droplet deformation induces the secondary breakup. The results provide the effect of ambient pressure on the macroscopic and microscopic behaviors such as spray development, spray penetration, mean droplet size, and mean velocity distribution. It is also revealed that the accuracy of prediction of LISA-DDB hybrid model is pretty good in terms of spray developing process, spray tip penetration, and SMD distribution.

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Hydrogneation and Electrochemical Characteristics of Gas-atomized Zr-based $AB_2$ Hydride for Ni-MH Secondary Battery (기체분무형 공정으로 제조된 Zr계 금속수소화물의 수소화반응 및 Ni-MH 2차전지 전극 특성에 관한 연구)

  • Kim, Jin-Ho;Hwang, Kwang-Taek;Kim, Byung-Kwan;Han, Jeong-Seb
    • Transactions of the Korean hydrogen and new energy society
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    • v.20 no.6
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    • pp.505-511
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    • 2009
  • The hydriding and electrochemical characteristics of Zr-based $AB_2$ alloy produced by gas atomization have been extensively examined. For the particle morphology of the as-cast and gas-atomized powders, it can be seen that the mechanically crushed powders are irregular, while the atomized powder particles are spherical. The increase of jet pressure of gas atomization process results in the decrease of hydrogen storage capacity and the slope of plateau pressure significantly increases. TEM and EDS studies showed the increase of jet pressure in the atomization process accelerated the phase separation within grain of the gas-atomized alloy, which brought about a poor hydrogenation property. However, the gas-atomized $AB_2$ alloy powders produced by jet pressure of 50 bar kept up the reversible $H_2$ storage capacity and discharge capacity similar to the mechanically crushed particles. In addition, the electrode of gas-atomized Zr-based $AB_2$ alloy of 50 bar showed improved cyclic stability over that of the cast and crushed particulate, which is attributed to the restriction of crack propagation by grain boundary and dislocation with ch/discharging cycling.

Development of Hybrid Model for Simulating of Diesel Spary Dynamics (디젤분무의 모사를 위한 혼합 모델의 개발)

  • 김정일;노수영
    • Transactions of the Korean Society of Automotive Engineers
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    • v.9 no.1
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    • pp.8-19
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    • 2001
  • A number of atomization and droplet breakup models have been developed and used to predict the diesel spray characteristic. Most of these models could not provide reasonable computational result of the diesel spray characteristic because they have only considered the primary breakup. A hybrid model is, therefore, required to develop by considering the primary and secondary breakup of liquid jet. according to this approach, wave breakup(WB) model was used compute the primary breakup of the liquid jet and droplet deformation and breakup(DDB) model was used for the secondary breakup of droplet. Development of hybrid model by using KIVA-II code was performed by comparing with the experimental data of spray tip penetration and SMD from the literature. A hybrid model developed in this study could provide the good agreement with the experimental data of spray tip penetration. The prediction results of SMD were in good agreement between 0.5 and 1.0 ms after the start of injection. Numerical results obtained by the present hybrid model have the good agreement with the experimental data with the breakup time constant in WB model of 30, and DDB model constant Ck of 1.0 when the droplet becomes less than 95% of maximum droplet diameter injected.

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Experimental Analysis and Numerical Modeling Using LISA-DDB Hybrid Breakup Model of Direct Injected Gasoline Spray

  • Park, Sung-Wook;Kim, Hyung-Jun;Lee, Chang-Sik
    • Journal of Mechanical Science and Technology
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    • v.17 no.11
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    • pp.1812-1819
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    • 2003
  • This paper presents the effect of injection pressure on the atomization characteristics of high-pressure injector in a direct injection gasoline engine both experimentally and numerically. The atomization characteristics such as mean droplet size, mean velocity, and velocity distribution were measured by phase Doppler particle analyzer. The spray development, spray penetration, and global spray structure were visualized using a laser sheet method. In order to investigate the atomization process in more detail, the calculations with the LISA-DDB hybrid model were performed. The results provide the effect of injection pressure on the macroscopic and microscopic behaviors such as spray development, spray penetration, mean droplet size, and mean velocity distribution. It is revealed that the accuracy of prediction is promoted by using the LISA-DDB hybrid breakup model, comparing to the original LISA model or TAB model alone. And the characteristics of the primary and secondary breakups have been investigated by numerical approach.