• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.3
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• pp.42-55
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• 2021

In this study, the effect of nozzle performance according to the selection of the center line equation. Three of S-type nozzles and three of double S-type nozzles were designed using the curve equation and design parameters, and the nozzle shielding performance was evaluated using the shielding ratio definition. In order to analyze the internal flow of the nozzle, the characteristics of the velocity distribution and pressure distribution were studied, and the nozzle performance was evaluated through the total thrust ratio(f) and the nozzle insulation efficiency coefficient(η). On the other hand, the centerline with a sharply change in curvature at the entrance has a low nozzle performance and a high shielding rate. The double S-type nozzle is excellent nozzle performance and shielding rate by using a smooth centerline at the first curvature.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.400-405
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• 2001

Nozzle of the double-plated grid plays the role of the spring to support a fuel rod as well as to provide the coolant path in grid. The nozzle was known to be necessary to reduce the spring stiffness for supporting performance. In this study the contact analysis between the fuel rod and the nozzle type spacer grid was performed by using ABAQUS standard to propose the preferable shape in tenn of spring performance. Two small cuts at the upper and lower part of the nozzle appeared to have a minor effect in decreasing the nozzle stiffness. A long slot at the center of the nozzle was turned out not only to decrease the spring constant as desired but also to increase the elastic displacement.

• 한국전산유체공학회:학술대회논문집
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• 1998.05a
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• pp.168-173
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• 1998

A numerical analysis of axisymetric backward facing step main nozzle flow in air jet loom has been accomplished. To obtain basic design data for an optimum main nozzle for an air-jet loom and to predict the transonic/supersonic flow, a characteristic based upwind flux difference splitting compressible Navier-Stokes method has been used. The wall static pressure of the main nozzle and the flow velocity changes in the nozzle tube were analyzed by changing air tank pressures and acceleration tube lengths. The flow inside the nozzle experiences double choking one at the needle tip and the other at the acceleration tube exit at tank pressures over $4kg_f/cm^2$. The tank pressure $P_t$ leading to the critical condition depends on the acceleration tube length; i.e, $P_t$ is higher for longer acceleration tubes. The $P_t$ value required to bring the acceleration tube exit to the critical condition is nearly constant regardless of acceleration tube length. The round needle tip shape might lead to less total pressure loss when compared with step shape.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.159-159
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• 2011

Among the semiconductor ternary compounds in the I-III-$VI_2$ series, $CulnS_2$ ($CulnSe_2$) are one of the promising materials for photovoltaic applications because of the suitability of their electrical and optical properties. The $CuInS_2$ thin film is one of I-III-$VI_2$ type semiconductors, which crystallizes in the chalcopyrite structure. Its direct band gap of 1.5 eV, high absorption coefficient and environmental viewpoint that $CuInS_2$ does not contain any toxic constituents make it suitable for terrestrial photovoltaic applications. A variety of techniques have been applied to deposit $CuInS_2$ thin films, such as single/double source evaporation, coevaporation, rf sputtering, chemical vapor deposition and chemical spray pyrolysis. This is the first report that $CuInS_2$ thin films have been prepared by Aerosol Jet Deposition (AJD) technique which is a novel and attractive method because thin films with high deposition rate can be grown at very low cost. In this study, $CuInS_2$ thin films have been prepared by Aerosol Jet Deposition (AJD) method which employs a nozzle expansion. The mixed fluid is expanded through the nozzle into the chamber evacuated in a lower pressure to deposit $CuInS_2$ films on Mo coated glass substrate. In this AJD system, the characteristics of $CuInS_2$ films are dependent on various deposition parameters, such as compositional ratio of precursor solution, flow rate of carrier gas, stagnation pressure, substrate temperature, nozzle shape, nozzle size and chamber pressure, etc. In this report, $CuInS_2$ thin films are deposited using the deposition parameters such as the compositional ratio of the precursor solution and the substrate temperature. The deposited $CuInS_2$ thin films will be analyzed in terms of deposition rate, crystal structure, and optical properties.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.155-158
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• 2002

In general, TVC(Thermal Vapor Compressor) is used to boost/compress a low pressure vapor to a higher pressure for further utilization. The one-dimensional method is simple and reasonably accurate, but cannot realize the detail as like the back flow and recirculation in the mixing chamber, viscous shear effect, and etc. In this study, the axisymmetric How simulations have been performed to reveal the detailed flow characteristics for the various ejector shapes. The Navier-Stokes and energy equations are solved together with the continuity equation In the compressible flow fields. The standard $k-{\epsilon}$ model is selected for the turbulence modeling. The commercial computational fluid dynamic code FLUENT software is used for the simulation. The results contain the entrainment ratio under the various motive, suction and discharge pressure conditions. The numerical results are compared with the experimental data, and the comparison shows the good agreement. The three different flow regimes (double chocking, single chocking and back flow) have been clearly distinguished according to each boundary pressure values. Also the effects of the various shape variables (nozzle position, nozzle outlet diameter, mixing tube diameter, mixing tube converging angle, and etc.) are quantitatively discussed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.6
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• pp.732-742
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• 1985

Measurements of mean velocity and turbulence characteristics are obtained with a linearized constant temperature hot-wire anemometer in a two-dimensional turbulent jet discharging parallel to a flate. Wall static pressure distribution is also measure. The Reynolds number based on the jet nozzle width (D) is about 42,000 and the step height is 2.5D. The reattachment length is found to be 7.5D by using both wool tuft and oil methods. Upstream of the reattachment point, there exist double coherent structures and mean velocity, Reynolds stresses and triple product profiles are asymmetric about jet center line due to the influence of streamline curvature and recirculating flow region. Near the reattachment point, wall static pressure and turbulence quantities change its shape rapidly because of the large eddies by the solid wall. Especially, turbulence intensity has a maximum value in the reattachment regin, then decreases slowly in the redeveloping wall jet ragion. Downstream of X/D=14, a single large scale eddy structure is formed. Far downstream affer the reattachment(X/D.geq.18) mean velocity profile, the decay of maximum velocity and the variation of jet half width are nearly similar to those of plane wall jet, but the Reynolds stresses are higher than those of the latter.