• Journal of ILASS-Korea
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• v.26 no.4
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• pp.189-196
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• 2021

Spray drift of agricultural nozzles has become a big issue because it causes low precision targeting and environmental pollution. In order to reduce the spray drift, study spray characteristics of agricultural nozzles is virtually important. In this study, shadowgraph and Mie-scattering visualization techniques were used to study the macroscopic spray and atomization characteristics of an agricultural nozzle. PDPA was used to measure the atomization characteristics of spray. The injection pressure is set to 1 bar, 3 bar and 5 bar, which covers the working range of the nozzle. For the PDPA experiment, 75 points were measured in an area of 160 mm × 120 mm at 10 mm intervals directly below the nozzle to grasp the overall atomization characteristics of the spray. It was found that the spray width and sheet width showed a linear correlation. As the injection pressure increased, the sheet expansion in the 0-degree direction and the sheet swing in the 90-degree direction jointly promoted the breakup of the sheet. In addition, the area close to the central axis had a large droplet velocity, and since a large droplet velocity promoted atomization of spray, the area close to the central axis had a smaller spray droplet diameter than the left and right regions.

• Journal of the Korean Society of Combustion
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• v.11 no.2
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• pp.1-6
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• 2006

This report presents a study of the development of an advanced coal nozzle used in burners to reduce unburned carbon (UBC) in a tangential coal-fired boiler. To understand the mechanism of UBC reduction, experiments using conventional burners were carried out to evaluate the effects of air injection velocity, coal fineness and over fired air (OFA) on combustion efficiency. It was confirmed that ignition of pulverized coal particles close to the burner is helpful toward the complete burn of residual carbon in fly ash. These efforts indicated the additional results that UBC was strongly dependent on the primary air velocity and coal fineness; especially that UBC dramatically decreased when the weight fraction of pulverized coal under $75{\mu}m$ was over 85 %. New coal nozzles, modified from conventional nozzles, were prepared and tested to improve the combustion efficiency. Some of these nozzles offered relatively lower unburned carbon than those of conventional burners and are referred to as HPFS (High Performance Flame Stability) coal nozzles.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.2
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• pp.11-18
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• 2001

To clarify the influence of SAC shape of hole-type diesel nozzle on injection characteristics and spray patterns, the injection rate of three nozzle types(standard SAC nozzle, Needle-cut VCO nozzle and VCO nozzle) were measured by Zeuch's method and pictures of the sprays were taken by CCD camera. As the pump speed became higher, the injection characteristics of the three nozzles were different. Injection rate and perssure curves at the high pressure pipe in Needle-cut VCO nozzle were much more similar to the VCO nozzle than those of the SAC nozzle. When the needle was at pre-lift period for all speeds, the spray of the Needle-cut VCO nozzle showed almost the same shape as the SAC type nozzle. There was no differense in spray pattern at the needle full-lift periods.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.4
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• pp.160-170
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• 1997

The objective of this study is to investigate the atomization characteristics and the performance characteristics of a C. I. engine by using the changes of the injection nozzle type and the ultrasonic-energy-added system. In order to evaluate the effect of ultrasonic energy and of change of injection nozzle type in the performance characte- ristics of a diesel engine, measurements of droplet size of diesel fuel were carried out by using Malvern system. In all types of injection nozzles, SMD of the ultrasonic- energy -added diesel fuel was smaller than that of the conventional diesel fuel and the more injection pressure increased, the more SMD decreased. There was a small increase in SMD with the distance from injection nozzle under all conditions of the injection nozzle types. The minimum SMD was found in the injection nozzle of B type. In the diesel engine test, there were three results about the engine performance. Compared with the injection nozzle of A type, B type had excellent effects in the engine performance. The most excellent effects about the engine performance were obtained in the case of ultrasonic-energy-added diesel fuel. In addition, the torque diagram in the case of ultrasonic-energy-added diesel fuel was more stable and periodical than others.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.1
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• pp.266-274
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• 1996

An experimental work was conducted to investigate the characteristics of the onset of flooding in vertical annuli with a direct injection mode using air and water. The onset of flooding was determined by means of pressure drop measurement while the air velocity was increased gradually under fixed liquid flow rates. Data of the onset of flooding were collected for various combinations of the tube size and the nozzle number. A theoretical analysis of the onset of flooding was also performed based on an envelope theory. The result shows that the onset of flooding in small-scale annuli can be predicted relatively well by the theory. A modified Wallis parameter was used to investigate the scaling effect of flooding phenomena in the annuli, indicating a relatively reasonable result. The number of nozzle has no effect on the flooding velocity when liquid was injected through 2, 3, 4 and 6 nozzles but the initiation of flooding was significantly expedited when 12 nozzles were employed for liquid injection.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.10
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• pp.933-939
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• 2010

The purpose of this study is to investigate the generation and development of cavitation in circular and elliptical nozzles. In order to investigate the influence of cavitation, the experiment was conducted with a set of elliptical nozzles that had the same cross-sectional area, different orifice aspect ratios (a/b). Each nozzle was made of acrylic so that visualization was possible. With the injection pressure, the internal flow of the nozzle was classified into the no-cavitation, cavitation, and hydraulic-flip regions. Regardless of the nozzle geometry, with the injection pressure, the flow rate in the no-cavitation and cavitation regions increased and the discharge coefficient decreased. However, the flow rate was constant in the hydraulic-flip region. In the elliptical nozzles, the generation and development of cavitation occurred at higher cavitation number than that in the case of a circular nozzle.

• 한국연소학회:학술대회논문집
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• 2002.06a
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• pp.16-23
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• 2002

Electrostatic pressure-swirl nozzle for practical oil burner application has been designed. The charge injection method has been used in this design, where the nozzle consists of a sharp pointed tungsten wire as a charge injector and the nozzle body grounded. The spray characteristics of the nozzles have been investigated by using an insulating liquid, i.e. kerosene without active surface agent. Breakup length of liquid decreased with an increase in applied voltage and injection pressure, while the spray angle increased with an increased in both applied voltage and injection pressure. An empirical equations have been suggested to predict the breakup length for electrostatic pressure-swirl atomizer. The experimental result was within the range of the predicted equations. The SMD decreased between the ranges of 2.8 ${\sim}$ 33% when the conventional nozzle was compared to the electrostatic with -10 kV applied to the electrode at a radial distance from 5 to 20 mm.

• Korean Journal of Optics and Photonics
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• v.12 no.3
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• pp.153-157
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• 2001

Operation conditions for the generation of an HF laser driven by fluorine-hydrogen combustion were discussed by mc:asuring the intensities of excited HF* molecules. Optimum injection quantities of fluorine gas for the generation of fluorine atoms was two times the injection mole number of hydrogen fuel. Slit nozzles with two dimensional configuration were used for the production of excited HF* molecules. When the injection mole number of secondary hydrogen gas is 1.3 times the injection mole number of fluorine gas, the fluorescence intensities of excited HF* molecules show maximum values. alues.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.320-324
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• 2017

Effect of elliptical orifice on the spray characteristics of liquid jet ejecting into subsonic crossflows were experimentally studied. Circular/elliptical plain-orifice injectors, which had different ratios of the orifice length to diameter and major axis to minor axis, were used for transverse injection. Compared with the previous research, breakup lengths of elliptical nozzles are shorter than circular nozzles at all experimental condition. Cavitation/hydraulic flip are considered as a reduction in the breakup length at all circular/elliptical nozzle. In the case of liquid column trajectories, major axis which was placed to the crossflows, increases the frontal area of the liquid column exposed to the crossflows. Hence, the aerodynamic force exerted on the jet is increased and the penetration depth is reduced.

• Journal of ILASS-Korea
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• v.12 no.4
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• pp.211-219
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• 2007

The liquid film thickness inside a pressure-swirl nozzle was measured, and then the measured liquid film thickness was compared with the results from previous empirical equations. The liquid film inside the nozzle was visualized using extended transparent nozzles and a microscopic imaging system, and then the measurement error was evaluated using optical geometry analysis. The high injection pressures up to 7MPa were adopted to simulate the injection conditions of the direct-injection spark-ignition engines. The totally different two injectors with different fuels, nozzle lengths, nozzle diameters and swirlers were utilized to obtain the comprehensive equations. The results showed that the liquid film thickness very slightly decreased at high injection pressures and the empirical equations overestimated the effect of injection pressure. Most of empirical equations did not include the effect of nozzle length and swirler angle, although it caused significant change in liquid film thickness. A new empirical equation was suggested based on the experimental results with the effects of fuel properties, injection pressure, nozzle diameter, nozzle length and swirler angle.