• Journal of Environmental Science International
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• v.27 no.6
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• pp.437-445
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• 2018

Laser induced-exciplex-fluorescence (EXCIPLEX) proposed by Melton is used to visualize fuel vapor in spray combustion. However, in the EXCIPLEX method based on TMPD/naphthalene system, the TMPD : naphthalene ratio is strictly restricted to 1 : 9. In addition, fluorescence intensity due to the vapor phase is extremely weak. To overcome these drawbacks, we propose a new laser-induced-excimer fluorescence (EXCIMER) method to visualize the liquid and vapor phases simultaneously. The spatial distributions of liquid and vapor in fuel spray suspended by ultrasonic waves are compared using the EXCIPLEX and EXCIMER methods. The correlation between fuel vapor concentration and fluorescence intensity is experimentally investigated by measuring the fluorescence intensity of saturated vapor formed over liquid fuel at a controlled temperature. These experimental results indicate that the EXCIMER method is effective for evaluating fuel vapor visualization in spray combustion. Furthermore, the quantitative distribution of fuel vapor concentration can be correctly estimated by the EXCIMER method.

• 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.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.2
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• pp.206-212
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• 2009

The pressurized spray system with nitrogen gas was designed to fabricate the spherical AN(ammonium nitrate) particles. When AN melt was sprayed from a nozzle with equivalent diameter of 0.28mm into an ambient dry air, the ligament breakup mechanism of the molten AN was found to be responsible for the droplet formation(or disintegration) of AN melt. In the experimental range of spray temperature with $170{\sim}200^{\circ}C$ and atomization pressure with $0.1{\sim}0.4MPa$, the spherical AN particles with mean diameter of $130{\sim}250{\mu}m$ were obtained.

• The Korean Journal of Ceramics
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• v.6 no.1
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• pp.58-63
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• 2000

The preparation of Y-doped $SrZrO_3$powder by ultrasonic spray pyrolysis was investigated as a representative system, in order to produce fine, single phase multicomponent oxide powders. A precursor solution containing metal nitrates, citric acid and ethylene glycol was atomized glycol was atomized with an ultrasonic spray nozzle. Gel particles formed by organic functional groups were pyrolyzed and subsequently calcined at $800^{\circ}C$ to obtain well-crystallized, single perovskite phase. Most of large particles exhibited macroscopic pores and weak agglomeration between primary particles. However, strong agglomeration was observed in the surfaces of large particles. The effect of the microstructures of these particles on size reduction to submicron particles was described.

• Journal of computational fluids engineering
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• v.2 no.2
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• pp.89-96
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• 1997

High injection pressure system has been developed as a measure to reduce harmful exhaust gases. In order to understand the effect of pressure on diesel spray injection process, wide range of high injection pressure was tested. 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. The droplet distributions, vapor fractions and gas flows are analyzed in various injection pressure cases. The distributions of spray and vapor increase and the Sauter mean diameter decreases with increasing injection pressure quickly in a low pressure area but slowly in a high pressure area.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.246-247
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• 2003

Large Eddy Simulation(LES) of turbulent spray combustion flow was conducted. An experimental database for the laboratory spray combustor is chosen to validate the present numerical simulation. The governing equations for the gas phases are discretized in three-dimensional curvilinear boundary-fitted coordinate system, and the fuel droplet motion equations are described in Lagrangian representation. The numerical results are compared with the experiment for the gas-phase mean velocities and its fluctuation in cold flow condition. Three dimensional vortical structures are well visualized and droplet motion is well predicted.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.353-358
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• 2000

To achieve the requirement for high fuel economy and low emissions, the research for GDI engines is recently very brisk in the whole world. This study was performed to measure distribution of average particle size in non-evaporating spray. The 2-D fluorescence/scattering images of fuel spray were captured simultaneously by visualization system composed of a laser sheet, a doubling prism, optical filters, and an ICCD camera. Using the ratio of the two light intensities, particle size distribution was obtained. The SMD measured by fluorescence/scattering technique was compared with it obtained by PDA. The experimental results show that the spray structure of GDI injector and temporal SMD distribution.

• Journal of Mechanical Science and Technology
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• v.16 no.3
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• pp.344-353
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• 2002

A reliable computational heat transfer model has been investigated to define the heat transfer characteristics of a spray column direct contact heat exchanger, which is often utilized in the process involving counterflows for heat and mass transfer operations. Most of the previous studies investigated are one-dimensional unsteady solutions based on rather fragmentary experimental data. Development of a multidimensional numerical model and a computational algorithm are essential to analyze the inherent multidimensional characteristics of a direct contact heat exchanger. The present study has been carried out numerically and establishes a solid simulation algorithm for the operation of a direct contact heat exchanger. Operational and system parameters such as the speed and direction of working fluid droplets at the injection point, and the effects of aspect ratio and void fraction of continuous fluid are examined thoroughly as well to assess their influence on the performance of a spray column.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.691-694
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• 2008

Spray characteristics of the APU simplex fuel nozzle are investigated. Four flight conditions such as sea level idle, sea level max power, 20,000 feet idle, 20,000 feet max power are used as spray experimental conditions. Spray visualization was performed by using ND-YAG laser. Droplet size and velocity were measured by using PDPA(Phase Doppler Particle Analyzer) system. From the test result, SMD is 100 ${\mu}$m�� and velocity is 10 m/s at 20,000 ft idle condition. In this condition, flame unstability could be occurred due to the higher drop diameter. Therefore it is necessary to decrease the droplet diameter in the high altitude condition.

• Journal of Mechanical Science and Technology
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• v.14 no.12
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• pp.1376-1385
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• 2000

This study investigates spray characteristics before and after wall impingingment of gasoline spray in suction air flow. For this study, a rectangular model intake port was made of acrylic glass, and suction air was generated by using the forced air blower contrariwise. The injector for this study was a pintle-type port gasoline injector in which an air-assist adaptor is installed to supply assisted air. A PDPA system was employed to simultaneously measure the size and velocity of droplets near the wall. Measured droplets are divided into "pre-impinging droplets"with positive normal velocity and "post-impinging droplets"were negative normal velocity for the suction flow. The velocities, size distributions and Sauter mean diameter(SMD) of pre-and post-impinging droplets for varions injection angles and air-assists are comparatively analyzed.