• Journal of ILASS-Korea
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• v.23 no.1
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• pp.9-15
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• 2018

Breakup lengths of circular and elliptical liquid jets in a subsonic crossflow were experimentally studied. Two circular-shaped and four elliptical-shaped plain-orifice injectors, which had different aspect ratios and orifice length to diameter ratios, were used to provide various liquid jet conditions such as steady, cavitation, and hydraulic flip. By varying the injection pressure drop from 1 bar to 6 bar, spray images were taken using a shadowgraph technique. Breakup lengths were measured and analyzed. As the aspect ratio in orifices increased, liquid column breakup lengths normalized by the equivalent diameter were reduced irrespectively of the switching of the major or minor axis to the crossflow. It was also found that when hydraulic flip developed inside the orifice, x-directional breakup lengths more decreased for both circular and elliptical liquid jets.

• 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.26 no.1
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• pp.33-39
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• 2021

Y-jet nozzle has a wide fuel flow rate range and turn-down ratio, thus, it is used in industrial boilers, furnace and agricultural atomizer. However, it has asymmetrical spray characteristics due to the nozzle design factors. Therefore, in this study, asymmetric spraying characteristics of the elliptical Y-jet nozzle was studied by using the lab-scale spray apparatus. As a result, the elliptical Y-jet nozzle had lower gas mass flow rate than circular Y-jet nozzle at same gas pressure, because of bigger shear stress due to the wider inner surface at the elliptical Y-jet nozzle. Larger SMD was measured on the elliptical Y-jet nozzle than the circular Y-jet nozzle. When SMD was measured in the X_Axis direction at the same gas mass flow rate, the elliptical Y-jet nozzle with an aspect ratio of 2:1 showed greater asymmetry than the others.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.3
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• pp.325-333
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• 2012

An experimental study was carried out to determine the correlation between the internal flow in a circular nozzle and elliptical nozzles with the external flow. The flow rate, spray angle and drop size were measured under various conditions of the injection pressure. Numerical simulations were attempted to investigate the internal flow structure in the elliptical nozzles, because the experimental study was limited in its measurements of flow velocity and pressure distributions in the relatively small orifice. In the case of the elliptical nozzles, the disintegration characteristics of the liquid jet were significantly different from those of the circular nozzle. Surface breakup was observed at the jet issued from the elliptical nozzles with injection pressure. This is due to the internal flow structure, which is reattached to the orifice wall at the minor axis plane of the elliptical nozzle, unlike that observed with the circular nozzle.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.5
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• pp.19-28
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• 2017

Effects of cavitation and hydraulic flip in circular and elliptical nozzles on the flow characteristics have been studied. Spray tests were conducted using injectors with different ratios of an orifice length(L) to a diameter(d) and of a major axis diameter(a) to a minor axis diameter(b). With the increment of an injection pressure drop, discharge coefficients slightly decreased in cavitation flows, and those suddenly dropped and were almost constant in hydraulic flip flows. For elliptical nozzles with L/b > 8 and L/a < 8, discharge coefficients and flow patterns showed different results from those in previous circular nozzles. When a flow in the elliptical nozzle was under steady condition, as the liquid column went downstream from the nozzle, its spray angle a little decreased in the plane of a major axis and increased in the plane of a minor axis.

• 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.

• Journal of ILASS-Korea
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• v.22 no.3
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• pp.146-152
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• 2017

An experimental study was carried out to investigate the spray characteristics of non-circular effervescent twin-fluid nozzles. For this purpose, two types of non-circular nozzles (E1, E2) and circular nozzle (C) were used. Three types of aerorators with hole diameters of 1.2, 1.7 and 2.1 mm were used. Each aerorator has a total of 12 holes. It is defined by area ratio which is ratio of exit orifice area and aerator hole area. Experiments were carried out by controlling the amount of air flowing after fixing the flow rate of the liquid, and the nozzle internal pressure and SMD were measured, and the jet image was taken from the nozzles. The discharge coefficients of the three kinds of nozzles were compared with the used in plain orifice's equation and the Jedelsky's equation, and the Jedelsky's equation was found to be about 3 times larger. In addition, empirical formula based on ALR, which is the largest variable in Jedelsky's equation, was derived. The droplet sizes(SMD) were found to be smaller in the non-circular shape than in the circular shape, which is concluded to be caused by the difference of the discharge coefficients.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.5
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• pp.535-540
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• 2011

It is well known that abrasive waterjet (AWJ) was developed as a kind of high-density energy processing technologies. AWJ is used to obtain cutting quality of various materials such as metal, ceramics, glass and composite materials within a short manufacturing time because of the characteristics of heatless and noncontact processing. However, surface roughness and dimension error like round, burr, taper vary severely according to the processing conditions such as pressure, cutting speed, orifice diameter, stand off distance and abrasive flow rate. In this paper, the effect of the shape of mixing chamber on surface quality is studied. Three types of mixing chamber - round, parabolic, elliptical - are suggested and each performance is compared to that of cylindrical mixing chamber experimentally. From the result, is proved to be the optimal mixing chamber in the aspect of surface quality the parabolic one.

• Journal of Chest Surgery
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• v.31 no.8
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• pp.763-769
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• 1998

Background: Supravalvular aortic stenosis is a rare form of congenital cardiac anomaly involving ascending aorta distal to coronary orifice. Materials and methods: We operated 12 cases of supravalvular aortic stenosis between July 1986 and March 1997. Age ranged from 4 to 17(mean 10.2) years and 11 of them were male. Nine patients had clinical features of Williams syndrome. We experienced two types of supravalvular aortic stenosis, including 10 hour glass type and 2 diffuse type. Results: Preoperative transaortic pressure gradient ranged from 40 to 180(mean 92) mmHg by cardiac catheterization. Pulmonary stenosis was associated in 5 and 2 of them required angioplasty. Operative techniques included 6 standard aortoplasty with elliptical patch, 4 extended aortoplasty with inverted Y shaped patch, and 2 modified Brom's repair. There were no operative deaths. Postoperative echocardiographic evaluation was done at a mean interval of 12 months. Grade I or II aortic regurgitation was found in 3 cases. Postoperative cardiac catheterization revealed a mean transaortic pressure gradient of 26 (range 0 to 75) mmHg. A mean pressure drop was 78(range 30 to 114) mmHg. All patients were followed up for a mean of 40(range 1 to 67) months with uneventful clinical course. Conclusions: Our data proved the low mortality and excellent hemodynamic improvement after surgical relief of supravalvular aortic stenosis in children.