• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.141-144
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• 2008

Atomization characteristics and spatial distribution of the spray emanating from an injector of liquid-propellant thruster are investigated by using dual-mode phase Doppler anemometry (DPDA). Spray characteristic parameters such as the mean velocity, Sauter mean diameter (SMD), and velocity fluctuation are measured at various locations along the spray axis as well as on the radial direction. Those data are quantified in radial profile and also used to scrutinize the correlation between diameter and turbulence intensity of spray droplets. For the better visual grasp, dynamic behavior of spray droplets along the spray stream is presented through the velocity vectors projected on the plane of geometric axis of nozzle orifice and radial coordinate.

• Journal of Mechanical Science and Technology
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• v.19 no.11
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• pp.2040-2052
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• 2005

The present paper centers on the establishment of a quantified relationship between the macroscopic visual parameters of a Diesel spray and its most influential factors. The factors considered are the ambient gas density, as an external condition relative to the injection system, and nozzle hole diameter and injection pressure as internal ones. The main purpose of this work is to validate and extend the different correlations available in the literature to the present state of the Diesel engine, i.e. high injection pressure, small nozzle holes, severe cavitating conditions, etc. Five mono-orifice, axi-symmetrical nozzles with different diameters have been studied in two different test rigs from which one can reproduce solely the real engine in-cylinder air density, and the other, both the density and the pressure. A parametric study was carried out and it enabled the spray tip penetration to be expressed as a function of nozzle hole diameter, injection pressure and environment gas density. The temporal synchronization of the penetration and injection rate data revealed a possible explanation for the discontinuity observed as well by other authors in the spray's penetration law. The experimental results obtained from both test rigs have shown good agreement with the theoretical analysis. There have been observed small but consistent differences between the two test rigs regarding the spray penetration and cone angle, and thus an analysis of the possible causes for these differences has also been included.

• Journal of ILASS-Korea
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• v.14 no.1
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• pp.8-14
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• 2009

This paper present the diesel fuel spray evolution and atomization performance in a multi-hole nozzle in terms of injection rate, spray evolutions, and mean diameter and velocity of droplets in a compression ignition engine. In order to study the effect of split injection on the diesel fuel spray and atomization characteristic in a multi-hole nozzle, the test nozzle that has two-row small orifice with 0.2 mm interval was used. The time based fuel injection rate characteristics was analyzed from the pressure variation generated in a measuring tube. The spray characteristics of a multi-hole nozzle were visualized and measured by spray visualization system and phase Doppler particle analyzer (PDPA) system. It was revealed that the total injected fuel quantities of split injection are smaller than those of single injection condition. In case of injection rate characteristics, the split injection is a little lower than single injection and the peak value of second injection rate is lower than single injection. The spray velocity of split injection is also lower because of short energizing duration and small injection mass. It can not observe the improvement of droplet atomization due to the split injection, however, it enhances the droplet distributions at the early stage of fuel injection.

• Journal of Korean Society for Atmospheric Environment
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• v.15 no.6
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• pp.799-804
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• 1999

Particle collection characteristics of the MOUDI cascade impactor has been studied for coarse particles in the range of 2 to 20$mu extrm{m}$ in aerodynamic diameter. A vibrating orifice aerosol generator was empolyed to generate monodisperse test aerosols. The oleic acid and sodium chloride(NaCl) particles were used as test aerosols. Aluminum foil and Teflon filter were selected as impaction media. The sampling flow rate was changed from 25 to 35L/min. Particle collection efficiency for single stage was examined for liquid particles. The stage response was obtained experimentally for the cascade impactor composed of three stages and a backup filter. The results showed that most of particle collection efficiencies measured in this work are similar to the efficiency curves obtained by Marple et al.(1991). For particles less than cut-off size of the stage, the collection efficiencies of solid particles are similar to those of loquid particles. However, the collection efficiency of solid particles decreases with mereasing particle diameter for the particles greater than the actual cut-off size of the impactor. The particle collection efficiency increases with increasing sampling flow rate at the same particel size. However, the collection efficiency curves seem not to be greatly shifted with the flow rate. The stage responses obtained by direct measurements in this work are in good agreement with those derived from the collection efficiency curves for single stage.

• Tribology and Lubricants
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• v.32 no.5
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• pp.166-171
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• 2016

Electric vehicle ownership is expanding for two reasons: its technology features have enhanced fuel economy, and the number of vehicle emissions regulations is increasing. Battery performance has a large influence on the capability of electric vehicles, and even though battery thermal management has been actively researched, specific technological improvements to battery performance are not being presented. For instance, many industrial applications utilize vortex tubes as components for refrigeration machines because of their numerous intrinsic benefits. If electric vehicles incorporate vortex tubes for battery cooling, performance and efficiency advancements are possible. This study uses a counter-flow vortex tube to investigate its temperature separation characteristics, based on the back pressure of the cold air exit and the difference between the inlet and back pressures. The experiment uses a vortex tube with the following parameters: six nozzle holes, a 20 mm inner vortex diameter (D), a 14D tube length, a 0.7D cold exit orifice diameter, and a nozzle area ratio of 0.142. The measurements prove that the temperature difference between the hot air and cold air decreased because of the flow resistance of the hot air and the backflow phenomenon at the cold air exit. The flow resistance causes the temperature difference to decrease, and the back pressure of the cold air exit influences the flow resistance. The results show that the back pressure significantly influences the efficiency of temperature separation.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.2
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• pp.105-113
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• 2013

A numerical model of the igniter for the interior ballistics has been developed by combining lumped parameter model with the theoretical equation of orifice. With the developed model of the igniter, the numerical study on characteristics of the interior ballistics has been conducted according to the igniter configuration in terms of igniter length, side hole diameter, and distribution of side holes. As results of the calculation of the pressure difference between the breech and shot base, the low-cycle oscillations have been influenced by the igniter length, while the high-cycle oscillations have been affected by the side hole diameter and the distribution of side holes.

• Journal of the Korean Society of Industry Convergence
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• v.5 no.1
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• pp.21-26
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• 2002

Response time of actuator in a hydraulic system may be important and necessary to avoid failures and to improve the efficiency of operation. Flow restricting devices can result in a decrease in the peak pressure, but may change the response time. The response time has an important effect on both operator and operator perceived smoothness. The response time should correspond to how fast a system responds to a given disturbance at the system boundary, Occasionally the appropriate response time is not easily determined. This study is on the characteristics of response time in the hydraulic system.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.1
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• pp.84-93
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• 2001

The aim of this study is to provide fundamental informations that make it possible to use a cool stream and a hot stream simultaneously. We changed the pressure of compressed air that flows into a tube, the inner diameter of orifice that a cold stream exits, and the mass flow rate ratio. And in each case, we measured the temperature of a cold stream and a hot stream in each exit of a tube. Also we measured the axial temperature distribution and the radial temperature distribution in internal space of a tube. From the study, following conclusive remarks can be made. Average flow rate that flows into a tube is in proportion to square root of inlet pressure. As inlet pressure increases axial and radial temperature distribution in the inner space of vortex-tube increase. As mass flow rate ratio change, separation point moves.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.5
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• pp.72-78
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• 2005

We conducted the performance test of micronozzle having nozzle throat diameter of 1.0, 0.5, 0.25 mm in an ambient pressure. We used N2 gas as a cold gas propellant. We varied chamber pressure from 2 to 20 bar and measured the thrust and mass flow rate. Through the test, we concluded that viscous losses were increased with decreasing chamber pressure. We found that micronozzle performance was higher than orifice performance through thrust comparison.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.1
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• pp.133-142
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• 2002

To improve the hydraulic control performance of ABS, it is necessary to establish an efficient control algorithm. And also it is necessary to ova]Hate a hydraulic modulator with solenoid valve quantitatively. In this paper, FEM and permeance method are used to analyze dynamic characteristics of outlet valve. In return, mathmatical modeling of a hydraulic modulator and operating pressure is presented, and the model parameters of an outlet valve are moving plunger, spring constant and orifice diameter. This study shows the way to improve the dynamic characteristic of an ABS outlet valve heavily depending on operating pressure. It is recommended that operating pressure should be justified at the first step toward the design to get the optimal design of an outlet valve.