• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.6
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• pp.496-502
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• 2018

In this study, experimental and analytical studies were carried out to observe the phenomenon of aerodynamic throat formed according to the primary flow and secondary flow momentum of the ejector. The equilibrium interval of the aerodynamic throat, which is the main variable of the ejector performance, was observed through the experiment using the cold flow experiment and the analysis using FLUENT. Performance characteristics were investigated by the change of the primary flow rate and the throat diameter of the ejector cylinder. As a result, the performance of the standard ejector was confirmed to be within the range of 0.33~1.167(off-design/design) and cylinder throat diameter range of 1~1.17(off-design/design area ratio).

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.167-173
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• 2003

For the measurement of mass flow rate at a wide range of operation conditions, it is required that the critical nozzle gas different diameters, since the mass flow rate through the critical nozzle depends on the nozzle supply conditions and the nozzle throat diameter. In the present study, both computational and experimental investigations are performed to explore the variable critical nozzle. Computational work using the 2-dimensional, axisymmetric, compressible Navier-Stokes equations are carried out to simulate the gas flow through variable critical nozzle. In experimnet, a cylinder with several different diameters is inserted into the critical nozzle to vary the nozzle throat diameter. Computational results are compared with the experimented ones. The computed results are in close agreement with experiment. It is found that the displacement and momentum thickness of variable critical nozzle are given as a function of Reynolds numbers. The discharge coefficient of the variable critical nozzle is predicted using an empirical equation.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.484-489
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• 2003

The mass flow rate of gas flow through critical nozzle depends on the nozzle supply conditions and the cross-sectional area at the nozzle throat. In order that the critical nozzle can be operated at a wide range of supply conditions, the nozzle throat diameter should be controlled to change the flow passage area. This can be achieved by means of a variable critical nozzle. In the present study, both experimental and computational works are performed to develop variable critical nozzle. A cone-cylinder with a diameter of d is inserted into conventional critical nozzle. It can move both upstream and downstream, thereby changing the cross-sectional area of the nozzle throat. Computational work using the axisymmetric, compressible Navier-Stokes equations is carried out to simulate the variable critical nozzle flow. An experiment is performed to measure the mass flow rate through variable critical nozzle. The present computational results are in close agreement with measured ones. The boundary layer displacement and momentum thickness are given as a function of Reynolds number. An empirical equation is obtained to predict the discharge coefficient of variable critical nozzle.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.9
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• pp.32-37
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• 2003

The trend of miniaturization has been applied to the research on micro rockets resulting in prototype rockets fabricated by MEMS processes. In this paper, the development of three-dimensional micro rockets using micro milling as well as the results of combustion and flight tests are discussed. The body of rocket was made of 6061 aluminum cylinder. The three-dimensional micro nozzles were fabricated on brass by micro endmill with 127${\mu}m$ diameter. Two different micro nozzles were fabricated, one with 1.0mm of throat diameter and the other with 0.5mm. The total mass of rocket was 7.32g and that of propellant was 0.65g. The thrust-to-weight ratio was between 1.58 and 1.74, and the flight test with 45 degree launch angle form the ground resulted in 46m-53m of horizontal flight distance