• 한국전산유체공학회:학술대회논문집
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• 2009.11a
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• pp.8-12
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• 2009

In this study the performance of the nozzle of a rocket system is evaluated using a CFD code. The main emphasis of the investigation is placed on the effects of the number (9 and 12) and the depth of fluted edge in the rocket nozzle. It is observed that as the depth increases the rolling moment of the nozzle increases while the thrust of the nozzle decreases.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.392-396
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• 2012

Experimental and computational study for steady-state pintle driven nozzle throat flow are carried out by changing four pintle shape. Results show that thruster performance is influenced by pintle shape greatly. This attributes to the distorted throat area and chamber pressure change as the pintle shape and its penetration.

• Fire Science and Engineering
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• v.30 no.4
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• pp.39-45
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• 2016

The optimal design of an air curtain nozzle installed at exits, such as fire doors, was determined in order to block the flow of smoke into safe zones. Smoke is the greatest cause of loss of life during the fire. To block the flow of smoke, the airflow must be expelled uniformly without eccentricity from the slits in the air curtain nozzle installed on the upper part of the opening. In order to accomplish this, factors such as air inflow volume, shape of the internal slits, and thickness of the external slits were considered as variables in this study, and a numerical analysis was performed under various conditions. This led to the selection of a final shape which led to the finalization of a design shape. The final shape was manufactured as a prototype and the results were compared and verified with the results of the numerical analysis. The relative error of the numerical analysis results was less than 1%, and the average speed of all the slits was tested, exhibiting a highly consistent tendency.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.3
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• pp.237-243
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• 2010

In this study, the effect of the shape of a pintle(obstacle) on thrust-modulation performance and drag in a pintle rocket was investigated by a cold flow test and by computational fluid dynamics. Pintle movement caused a monotonic increase in the chamber pressure. Thrust generated by the pressure distribution on the pintle body was linearly changed to the chamber pressure, and this thrust was greater than that generated by the nozzle-wall pressure distribution. Because the shock pattern in the nozzle changes with the shape of the pintle body and pressure ratio, the thrust generated by the nozzle-wall pressure is not directly affected by chamber pressure. The drag due to the pintle(obstacle) can be minimized for a fully linear pintle shape, regardless of chamber pressure.

• Journal of the Korean Ceramic Society
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• v.32 no.9
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• pp.995-1002
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• 1995

The alumina fiber was obtained by extruding the TEA complexed polymeric sol, synthesized by the alkoxide sol-gel method, through nozzle. The purpose of this study was to investigate the properties of fiber spun by TEA complexed sol. The analysis of sol indicated that TEA was bonded at alkoxide precursor and the optimum molar ratio for spinning was 0.5 mole of TEA, 3 mole of H2O. The cross section of the fiber from circular nozzle was not circular but oval, which indicated that the shape of nozzle did not affect the shape of fiber. The diameter of the fiber was about 100 ${\mu}{\textrm}{m}$ in the state of dried gel fiber, 60${\mu}{\textrm}{m}$ in calcined fiber, and the tensile strength of the fiber calcined at 90$0^{\circ}C$ was 2.1$\times$108 Pa.

• Journal of computational fluids engineering
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• v.20 no.3
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• pp.70-78
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• 2015

Turbulent flow and heat transfer characteristics of textile machine are numerically investigated. To examine the influence of flow structures on the drying performance of fabrics, the nozzle shape of high temperature chamber is changed. For several nozzles, flow and heat transfer characteristics are discussed. The results show that the drying performance is improved by controlling the angle and arrangement of nozzles corresponding to different drying conditions. This feature is strongly related to the enhancement of turbulent fluctuations and secondary flows.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2833-2838
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• 2007

Recently, small hydropower attracts attention because of its clean, renewable and abundant energy resources to develop. However, suitable turbine type is not determined yet in the range of small hydropower and it is necessary to study for the effective turbine type. Moreover, relatively high manufacturing cost by the complex structure of the turbine is the highest barrier for developing the small hydropower turbine. Therefore, a cross-flow turbine is adopted because of its simple structure and high possibility of applying to small hydropower. The purpose of this study is to examine the optimum configuration of nozzle shape to further optimize the cross-flow hydraulic turbine structure and to improve the performance. The results show that pressure on the runner blade in Stage 1 and velocity at nozzle outlet have close relation to the turbine performance.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.493-493
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• 2009

Recently, small vertical axis wind turbine attracts attention because of its clean, renewable and abundant energy resources to develop. Therefore, a cross-flow type wind turbine is proposed for small wind turbine development in this study because the turbine has relatively simple structure and high possibility of applying to small wind turbine. The purpose of this study is to investigate the effect of the turbine‘s structural configuration on the performance and internal flow characteristics of the cross-flow turbine model using CFD analysis. The results show that guide nozzle should be adopted to improve the performance of the turbine. Optimization of the nozzle shape will be key-importance for the high performance of the turbine.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.752-757
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• 2001

To reduce stress concentration around the intersection between a spherical pressure vessel and a cylindrical nozzle under various load conditions using less material, the optimization for the distribution of reinforcement has researched. The ranked bidirectional evolutionary structural optimization(R-BESO) method is developed recently, which adds elements based on a rank, and the performance indicator which can estimate a fully stressed model. The R-BESO method can obtain the optimum design using less iteration number than iteration number of the BESO. In this paper, the optimized intersection shape is sought using R-BESO method for a flush and a protruding nozzle. The considered load cases are a radial compression, torque and shear force.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.61-65
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• 2011

In this paper, the nozzle design with asymmetric configuration using the optimal method is used in order to improve the under- and over-expansion problem of the flow at the supersonic turbine nozzle. For the design of nozzle contour, 8 design variables are selected and the total-to-static efficiency from the nozzle inlet to the wake outlet is considered as the objective function to be maximized. The Fluent6.3 and the iSIGHT-FD program are used for calculation of nozzle flow and design optimization respectively. RBF(Radial Basis Function) method is chosen for approximate optimization algorithm. It is shown that the static efficiency of improved nozzle design increases 1.35% and loss coefficient decreases 19.85% as compared to baseline design.