• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.6
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• pp.19-26
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• 2002

The objective of this study is to examine a DI(Direct Injection) gasoline spray development process under different ambient pressures using PIV(Particle Image Velocimetry). fuel spray experiments were performed within a constant volume chamber. The spray structure, velocity maps, velocity and vorticity contours were obtained to investigate its spray characteristics. It was found that higher ambient pressure has a significant effect on radial growth of the spray. The position which has a maximum velocity moved from the spray edge to the spray center as ambient pressure was increased. Higher ambient pressure moved a maximum vorticity position upward of the spray.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.7
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• pp.417-427
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• 2016

This paper is the first investigation of the steady flow characteristics of an SI engine with a semi-wedge combustion chamber as a function of the port shape. For this purpose, the planar velocity profiles were measured at the 1.75B position by particle image velocimetry. The flow patterns were examined with both a straight and a helical port. Two swirls were observed up to 4 mm valve lift with the straight port and up to 2 mm with the helical one; however, only one swirl was present after these lifts. The flow characteristics changed suddenly between 4 and 5 mm lift in the straight port; on the other hand, the change with lift was gradual with the helical port - the transition points between flow regimes were different with the port shapes. In addition, the centers of the swirls were relatively far from the cylinder center so that the effect of eccentricity may not be negligible at 1.75B, regardless the shape. The eccentricity values with the straight port were especially high - over 0.5 for all lifts. Finally, real velocities were found to be much lower than those predicted by the assumption of ISM evaluation, with the profiles differing qualitatively as well.

• Journal of ILASS-Korea
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• v.7 no.3
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• pp.38-44
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• 2002

The purpose of this study is to investigate the effect of the volume fraction of water and injection pressure on the spray characteristics of water/oil emulsified fuel injected from the pressure swirl atomizer. The mixture of light oil and water by using impeller mixer was performed. The spray characteristics such as SMD and velocity were measured using PDPA. The injection pressures were 7.5, 100, 200 and $300kgt/cm^2$ and volume fractions of water in emulsified fuel were 0, 10, 20 and 30%, respectively. The measurement sections were at 30, 60 and 90mm from injection nozzle tip. SMD and velocity of emulsified fuel were larger gradually by increasing the volume fraction of water in emulsified fuel. The spray angle was decreased and axial velocity was increased with increase in water content. It was found that the relative SMD ratio was increased more greatly than the relative axial velocity ratio in super critical pressure. The relative SMD ratio was increased and the relative axial velocity ratio was decreased with increase injection pressure at spray downstream.

• Journal of Ocean Engineering and Technology
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• v.10 no.3
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• pp.138-152
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• 1996

Many studies of heat transfer on the swirling flow or unswirled flow in a abrupt pipe expansion are widely carried out. The mechanism is not fully found evidently due to the instabilities of flow in a sudden change of the shape and appearance of turbulent shear layers in a recirculation region and secondary vortex near the corner. The purpose of this study is to obtain data through an experimental study of the swirling flow and heat transfer downstream of an abrupt expansion in a circular pipe with uniform heat flux. Experiments were carried out for the turbulent flow nd heat transfer downstream of an abrupt circular pipe expansion. The uniform heat flux condition was imposed to the downstream of the abrupt expansion by using an electrically heated pipe. Experimental data are presented for local heat transfer rates and local axial velocities in the tube downstream of an abrupt 3:1 & 2:1 expansion. Air was used as the working fluid in the upstream tube, the Reynolds number was varied from 60, 00 to 120, 000 and the swirl number range (based on the swirl chamber geometry, i.e. L/d ratio) in which the experiments were conducted were L/d=0, 8 and 16. Axial velocity increased rapidly at r/R=0.35 in the abrupt concentric expansion turbulent flow through the test tube in unswirled flow. It showed that with increasing axial distance the highest axial velocities move toward the tube wall in the case of the swirling flow abrupt expansion. A uniform wall heat flux boundary condition was employed, which resulted in wall-to-bulk temperatures ranging from 24.deg. C to 71.deg. C. In swirling flow, the wall temperature showed a greater increase at L/d=16 than any other L/d. The bulk temperature showed a minimum value at the pipe inlet, it also exhibited a linear increase with axial distance along the pipe. As swirl intensity increased, the location of peak Nu numbers was observed to shift from 4 to 1 step heights downstream of the expansion. This upstream movement of the maximum Nusselt number was accompanied by an increase in its magnitude from 2.2 to 8.8 times larger than fully developed tube flow values.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.8
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• pp.1552-1565
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• 1992

Three dimensional numerical calculations were carried out for two different combustion chambers with the offset valve in order to investigate the swirl and the squish effects on the flow fields. The modified K-.epsilon. turbulence model considering the change of the density under the condition of the rapid compression and expansion of the pistion was used. During the compression process, it was found that the squish flow which controls the subsequent combustion process was produced due to the piston bowl in the bowl piston type combustion chambers but not for the flat piston type. The swirl velocity close to the solid body rotation was maintained in the flat piston type combustion chambers, but for the bowl piston type a resulting from the change of the solid body rotation was generated in the radial-circumferential plane. For the swirl ratio effect, as the swirl ratio increases, it was found that a large and strong vortex was generated in the radial-circumferential plane of bowl piston type combustion chambers because of the strong inward flows from the combustion chamber wall. These computational results were compared with the results of LDA measurement.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.720-726
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• 2001

Two-dimensional, angle-resolved LDV(Laser Doppler Velocimetry) measurements of the turbulent rotating flow field in a confined cylinder have been performed. The configurations of interest are flows between a rotating upper disk with a rod attached by a disk or impeller(${\theta}= 90^{\circ},\;45^{\circ}$) and a stationary lower disk in a confined cylinder. The mean flow velocity as well as the turbulent intensity of the flow field have been measured. The results show that the flow is strongly dependent on the position of the impellers or the disk, negligibly affected by the Reynolds number in turbulent flow. It is observed that the mixing effect of the axial flow impeller(${\theta}= 45^{\circ}$) is better than that of the radial flow impeller(${\theta}= 90^{\circ}$) or a disk.

• Journal of the Korean Society of Visualization
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• v.7 no.1
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• pp.14-20
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• 2009

In comparison with previous researches fur swirling flow, the spiral flow self-generated in the spiral flow nozzle has some different characteristics. It is not needed a compulsive tangential momentum to get its velocity component and has long potential core, relatively low swirl ratio, and high focusing ability. In this study, the self-generated mechanism of the spiral flow was clarified and the effect on the width of annular slit on spiral flow characteristics was investigated experimentally and numerically. As a result, the existence of tangential velocity component regardless of a compulsive angular momentum is clarified and the results obtained by experiment have a satisfactory agreement with those by numerical method, quantitatively and qualitatively.

• 한국가시화정보학회:학술대회논문집
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• 2007.11a
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• pp.143-148
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• 2007

In comparison with previous researches for swirling flow, the spiral flow self-generated in the spiral flow nozzle has some different characteristics. It is not needed a compulsive tangential momentum to get its velocity component and has long potential core, relatively low swirl ratio, and high focusing ability. In this study, the self-generated mechanism of the spiral flow was clarified and the effect on the width of annular slit on spiral flow characteristics was investigated experimentally and numerically. As a result, the existence of tangential velocity component regardless of a compulsive angular momentum is clarified and the results obtained by experiment have a satisfactory agreement with those by numerical method, quantitatively and qualitatively.

• 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.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.822-827
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• 2003

Experiments were done for the three dimensional unsteady flow in a counter rotating axial flow fan under stable operating condition. Flow fields in a counter rotating axial flow fan were measured at cross-sectional planes of the upstream and downstream of each rotor. Cross sectional flow patterns were investigated through the acquired data by the $45^{\circ}$ inclined hot-wire. Flow characteristics such as tip vortex, secondary flow and tip leakage flow were confirmed through axial, radial and tangential velocity vector plot. Swirl velocity, which was generated by the front rotor, was recovered in the form of static pressure rise by the rear rotor except for hub and tip regions.