• International Journal of Automotive Technology
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• v.6 no.2
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• pp.87-93
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• 2005

Spray patterns were visualized using the shadowgraph method, and the droplet size and velocity were measured using PDPA for high-pressure injections up to 2,600 bars. The spray pattern and spray characteristics, such as penetration, spray width, spray angle, droplet size, injection duration, and droplet velocity, were investigated to determine the suitable injection pressure. Spray penetration, width, angle, and velocity increased continuously up to 2,600 bars with the injection pressure in a high-pressure region. The rate of improvement of the above spray characteristics, however, declined rapidly, when the injection pressure reached 2,000 bars. The injection duration and droplet size generally decreased with the increase in the injection pressure, while the rate of improvement decreased abruptly after 2,000 bars. Consequently, the improvement rate of the spray characteristics became blunt at over 2,000 bars. This means that the suitable injection pressure is around 2,000 bars.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.2
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• pp.80-86
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• 1997

This experiment was undertaken to investigate spray characteristics of the conventional injection system and the ultrasonic energy added injection system. Sauter mean diameter was measured under the variation of injection pressure and the spray distance. To measure the droplet size, we used the Malvern system 2600C. The spray angle and mass distribution were analyzed to the CCD camera and the patternater. After experiment, it was found that the ultrasonic energy added injection system had smaller Sauter mean diameter of droplet, wider mass distribution and wider spray angle than the conventional injection system had.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.4
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• pp.18-26
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• 2001

OSKA engine was developed to remove the dense core of injection sprays. The engine uses impinging spray on a small pip, which spray after impinging is broken into smaller drops and disperses into fee space in chamber. In this paper the pip size is analyzed to give more dispersion of spray and fuel vapor. The gas phase is modelled by the Eulerian continuum conservation equations of mass, momentum, energy and fuel vapour fraction. The liquid phase is modelled following the discrete droplet model approach in Lagrangian form, and the droplet wall interaction is modelled as a function of the velocity normal to impaction lands. The droplet distributions, vapor fractions and gas flows are analyzed for various injection pressure cases. Numerical results indicate that the land diameter of 5.6mm has the best performance of spray dynamics and vaporization in the test sizes.

• Journal of ILASS-Korea
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• v.1 no.1
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• pp.85-91
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• 1996

This experiment was undertaken to investigate spray characteristics of the conventional inject ion system and the ultrasonic energy added inject ion system. Sauter mean diameter was mesured under the variation of inject ion pressure and the spray distance. To measure the droplet size we used the Malvern system 2600C. The spray angle and mass distribution was analyzed to the CCD camera and the patternater. After experiment, it was found that the ultrasonic energy added injection system had smaller sauter men diameter of droplet, wider mass distribution and wider spray angle than the conventional inject ion system had.

• International Journal of Automotive Technology
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• v.4 no.4
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• pp.157-164
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• 2003

An experimental and numerical study was performed to investigate the macroscopic and microscopic atomization characteristics of high-speed diesel spray issued from the common-rail injection system. For the experiments, spray visualization system and a phase Doppler particle analyzer system were utilized to obtain the spray atomization characteristics such as the process of spray development, spray tip penetration, and SMD distribution. In order to analyze the process of spray atomization with KIVA-3 code, the TAB breakup model is changed to the KH-DDB competition model, which assumes the competition between the wave instability and droplet deformation causes the droplet breakup above the breakup length. The calculated results were also compared with the experiments in terms of spray tip penetration and SMD distribution. The results provide the process of spray development, axial and radial distribution of SMD, and calculated overall SMD as a function of time after start of injection.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.5
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• pp.174-181
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• 1998

Experimental and analytical studies are presented to characterize the break-up mechanism and atomization processes of the intermittent- impinging-type nozzle. Gasoline jets passing through the circular nozzle with the outlet diameter of 0.4mm and the injection duration of 10ms are impinged on each other. The impingement of fuel jets forms a thin liquid sheet, and the break-up of the liquid sheet produces liquid ligaments and droplets subsequently. The shape of liquid sheets was visualized at various impinging velocities and angles using the planer laser induced fluorescence (PLIF) technique. Based on the Kelvin-Helmholtz wave instability theory, the break-up length of liquid sheets and the droplet diameter are obtained by the theoretical analysis of the sheet disintegration. The mean diameter of droplet is also estimated analytically using the liquid sheet thickness at the edge and the wavelength of the fastest growing wave. The present results indicate that the theoretical results are favorably agreed with the experimental results. The size of droplets decreases after the impingement as the impinging angle or the injection pressure increase. The increment of the injection pressure is more effective than the increment of the impinging angle to reduce the size of droplets.

• Journal of ILASS-Korea
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• v.7 no.2
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• pp.22-30
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• 2002

A number of droplet breakup models have been developed to predict the diesel spray. The capabilities of droplet deformation and breakup models such as TAB, ETAB, DDB and APTAB models are evaluated in modeling the non-evaporating diesel sprays injected into atmosphere. New methods are also suggested that take into account the non- spherical shape of droplets and the reduced drag force by the presence of neighbouring droplets. The KIVA calculations with standard ETAB, DDB, and APTAB models predict well the spray tip penetrations of the experiment, but overestimate the Sauter mean Diameter(SMD) of droplets. The calculation with non spherical droplets injected from the nozzle shows very similar results to the calculation with spherical droplets. The drag coefficient which is linearly increased with the time after start of injection during the breakup time gives the smaller SMD that agrees well with the experimental result.

• 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.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.4
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• pp.261-267
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• 2003

The present study investigates the fire suppression characteristics using a water mist fire suppression system. Numerical simulations of fire suppression with water mist are performed with considering the interaction of fire plume and water droplet, droplet evaporation, and combustion of pool fire. The predicted temperature fields of smoke layer are compared with that of measured data. Numerical results agree with the experimental results within 5$^{\circ}C$ in the case without water mist In the case of fire suppression with water mist, numerical results dose not predict well lot temperature field in the gradual cooling region after water mist injection. But the predicted results of initial fire suppression are in good agreement with that of measured data. The reason of the discrepancy between predicted and measured data is due to the variation of turning rate during the injection of water mist. The effect of burning rate on the fire suppression is left as future study.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.4
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• pp.100-111
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• 1994

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 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 microphotographs 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 and 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 characteristics inside the nozzle rather than aerodynamic interactions. However, once the spray was established, aerodynamic interactions are essential in the near-nozzle atomization.