• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.2
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• pp.87-92
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• 2008

The breakup processes and spray plume characteristics of liquid jets injected in subsonic air cross-flows were experimentally studied. The behaviors of column, penetration, breakup of plain liquid jet and droplet sizes, velocities have been studied in non-swirling cross-flow of air. Nozzle has a 1.0 mm diameter and Lid ratio=5. Experimental results indicate that the breakup point is delayed by increasing air momentum, the penetration decreases by increasing Weber number and the split angle is increased by increasing air velocity or decreasing injection velocity. SMD increases according as increasing height or decreases in accordance with increasing air velocity. This phenomenon is related to the momentum exchange between column waves and cross-flow stream. Droplet vector velocities were varied from 11.5 to 33 m/s. A higher-velocity region can be identified in down edge region at Z/d=40, 70 and 100. Lower-velocity region were observed on bottom position of the spray plume.

• Journal of ILASS-Korea
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• v.12 no.2
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• pp.115-122
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• 2007

The spray characteristics and drop size measurements have been experimentally studied in liquid jets injected into subsonic crossflow. With water as fuel injection velocity, injection angle and atomize. internal flows were varied to provide of jet operation conditions. The injector internal flow was classified as three modes such as a non-cavitation flow, cavitation, and hydraulic flip flows. Pulsed Shadowgraph Photography measurement was used to determine the spatial distribution of the spray droplet diameter in a subsonic crossflow of air. And this study also obtains the SMD (Sauter Mean Diameters) distribution by using Planar Liquid Laser Induced Fluorescence technique. The objectives of this research are get a droplet distributions and drop size measurements of each condition and compare with the other flow effects. As the result, This research has been showned that droplet size were spatially dependent on air-stream velocity, fuel injection velocity, injection angle effects, and normalized distance from the injector exit length(x/d, y/d). There are also different droplet size characteristics between cavitation, hydraulic flip and the non-cavitation flows.

• Journal of the Korean Society of Visualization
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• v.3 no.1
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• pp.58-62
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• 2005

Flow characteristics at secondary recirculation zone in a liquid fuel ramjet combustor were investigated using CFD and Stereoscopic PIV method. The combustors have two rectangular inlets that form 90 degree each other. Three guide vanes were installed in each rectangular inlet to improve the flow stability. The tested angle of the air intakes was 60 degree. The experiments were performed in the water tunnel test with the same Reynolds number in the case of Mach 0.3 at inlet. The computational and experimental results showed that the secondary recirculation flow occurred at the front junction of inlet main stream and combustor chamber. The size of secondary recirculation regions are increased with approaching closer to the center of the combustor. Since the performance of combustor is closely dependent not only on the main recirculation in the dome region but also on the secondary recirculation flow in a junction region, the optimal angle of the air intakes should be considered the recirculation size as frame holder.

• Journal of Mechanical Science and Technology
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• v.14 no.2
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• pp.226-235
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• 2000

The performance prediction of an airfoil fan using a commerical code, STAR/CD, is verified by comparing the calculated results with measured performance data and velocity fields of an airfoil fan. The effects of inlet tip clearance on performance are investigated. The calculations overestimate the pressure rise performance by about 10-25 percent. However, the performance reduction due to tip clearance is well predicted by numerical simulations. Main source of performance decrease is not only the slip factor but also impeller efficiency. The reduction in performance is 12-16 percent for 1 percent gap of the diameter. The calculated reductions in impeller efficiency and slip factor are also linearly proportional to the gap size. The span-wise distributions of phase averaged velocity and pressure at the impeller exit are strongly influenced by the radial gap size. The radial component of velocity and the flow angle increase over the passsage as the gap increases. The slip factor decreases and the loss increases with the gap size. The high velocity of leakage jet affects the impeller inlet and passage flows. With a larger clearance, the main stream moves to the impeller hub side and high loss region extends from the shroud to the hub.

• Journal of Advanced Marine Engineering and Technology
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• v.11 no.3
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• pp.53-60
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• 1987

Steam ejector is a equipment which compresses the gases to desired discharge pressure. It is widely used for the evacuation systems because of its high working confidence. And recently it is used as the thermo-compressors in the various energy saving systems. Steam ejector is constructed of three basic parts; a suction chamber, a motive nozzle and a diffuser. The high velocity stream jet of steam emitted by the motive nozzle creats suction chamber, which draws the low pressure gases. The diffuser converts the kinetic energy of high velocity flow to pressure energy. It is not easy to determine the dimensions of a steam ejector met to the desired design condition, because that the expected suction rates must be obtained by reapeating the complicate calculation. And also such a calculation is concomitant with geometrical analysis for suction part and diffuser based on the stability of steam flow. Therefore, it is considered that the Computer-Aided Design (CAD) of steam ejector is a powerful design method. In this paper, computer program for steam ejector design is developed based on the theoretical research and the previous experimental results. And the determinating method of diffuser inlet angle and the velocity development profile of suction gas along to the diffuser are suggested. The validity of the development profile of suction gas along to the diffuser are suggested. The validity of the developed computer results with other's for the practical design calculation of a manufactured steam ejector.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.10
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• pp.2617-2629
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• 1995

The flow through a centrifugal compressor rotor was calculated using the quasi-3-dimensional and fully 3-dimensional Navier-Stokes solution methods. The calculated results, obtained during the development of the computer codes for both methods are discussed. In the inviscid quasi 3-dimensional analysis, stream function formulation was used for the blade to blade (B-B) plane calculations, and the streamline curvature method was used for the meridional (H-S) plane calculations. In the viscous 3-dimensional flow analysis, a control volume method based on a general rotating curvilinear coordinate system was used to solve the time-averaged Navier-Stokes equations, and a standard k-.epsilon. model was used to obtain eddy viscosity. The quasi-3-dimensional analysis reasonably predicts the pressure distributions and requires much less computation time in the region where viscous effects are not strong; however, it fails to predict velocity field and loss mechanism through the impeller passage. The viscous 3-dimensional flow analysis shows reasonable pressure distributions and typical jet-wake flow field through the impeller passage. Secondary flow and total pressure distributions on cross-sectional planes explain the loss mechanisms through the impeller.

• Journal of Biosystems Engineering
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• v.29 no.3
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• pp.225-232
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• 2004

A new type of garlic peeling chamber has been developed which separates and peels garlic cloves using high-Pressure water Jets. The cylindrically-shaped chamber was fabricated with stainless steel plate and has a number of drilled holes, which function as solid-stream spray nozzles, on its interior wall. The chamber was divided into upper and lower section so that water can be applied at different pressures from each section. Three chambers of similar design were tested to evaluate their performances according to various pressure levels. The strongest correlation was observed between the pressure difference(lower-upper) and the proportion of unseparated and completely-peeled garlic cloves. Hanji-type garlic required higher or pressure difference to separate cloves from garlic bulbs than nanji-type garlic. On the other hand, protective leaves(skin) from the cloves were peeled more easily in case of hanji-type garlic. As a result of three consecutive peeling operations, the proportion of completely-peeled garlic cloves changed in the order of 80.1, 82.6, 84.1% in case of hanji-type, and 19.6, 29.1, 40.2% in case of nanji-type garlic.

• Journal of ILASS-Korea
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• v.12 no.3
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• pp.160-165
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• 2007

In this study, the breakup characteristics of mono disperse droplets were studied with various fuels, ethanol, diesel fuel, biodiesel fuel extracted from soybean oil, and pure water. In order to investigate the droplet behavior in air cross-flow conditions, the experimental equipment was composed of a droplet generator with an air nozzle, and a high-magnification photo detecting system. Droplets produced by the droplet generator were injected into the air stream flowing normal to a direction of liquid drop jet. Digital images of the droplet behavior in air flow field were recorded by controlling the air flow rate. From the inspections, droplet breakup mechanism is primarily classified into the two kinds of stage, first breakup stage and second breakup stage. At the first breakup stage, droplet deformation rate seems to be affected by the force induced by the surface tension and the viscosity. On the other hand, at the second breakup stage, droplet is broken up mainly induced by the surface tension, so the breakup transition can be divided by the regular Weber number.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.672-675
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• 2010

Spray characteristics for the modulation with a pulsed spray in low-frequency region were investigted by performing with additional internal pulsed injection. The 1st perturbative flow was generated by rotating-type pulsed device and the 2nd pulse source generated by the magnetic valve was used to modulate the 1st flow. A pattern of the modulated spray was observed through FFT result and visualization. In case of modulated spray with the 2nd pulse control, the width of up and down motion of the modulated spray is smaller than that of the spray without the 2nd pulse. Also, the depth of penetration of the down stream is higher than that of spray without the 2nd pulse.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.3
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• pp.1005-1014
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• 1996

An experimental investigation has been carried out to examine the influence of injector design variables and operating conditions on the resultant drop size for triplet impinging streams injectors. The variables studied in this investigation are pressure drop, impinging angle, orifice length to diameter ratio, and impinging point distance. Droplet-size data are obtained using water as the propellant simulant by Malvern Particle Analyzer System. Drop size decreases with increasing impinging angle and pressure drop while other injector parameters remain constant at the same point. But it is found that there is no noticeable droplet-size change which results from change in orifice length to diameter ratio or impinging point distance within the investigated range.