• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.14-17
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• 2011

Numerical simulation was carried out for the SNECMA modulatable thrust devices, with four different nozzle contraction angle $45^{\circ}$, $60^{\circ}$, $83^{\circ}$, and $90^{\circ}$, respectively. Results show that $83^{\circ}$ nozzle contraction is better in that it comes up with good thrust level with small aerodynamic load.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.1
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• pp.24-32
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• 2019

Numerical simulations were carried out in a supersonic nozzle to investigate the possibility of using dual-throat nozzle concept in fluidic thrust vector control. Validation of the methodology showed an excellent agreement between the computational fluid dynamics results and the experimental data available, which were based on the well-assessed SST $k-{\omega}$ turbulence mode. The deflection angle, system resultant thrust ratio, and thrust efficiency were investigated in a wide range of nozzle pressure ratios and injection pressure ratios. The performance variations of the dual-throat nozzle thrust vector control system were clearly illustrated with this two-dimensional computational domain. Some constructive conclusions were obtained that may be used as a reference for further studies in the fluidic thrust vector control field.

• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.5
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• pp.11-23
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• 2022

For the design of the shortened ED(Expansion Deflection) nozzle, a numerical study of ED nozzle was performed according to the length reduction methods. The first method is to reduce the extension length of the ED nozzle with 80% bell nozzle length by 10%, 20% and 30%. The second method is to shorten the extension length by increasing the nozzle throat angle. Due to the increase in the curvature of the contour as the length shortened, the decrease in the nozzle exit velocity between the ED nozzle with 80% bell nozzle length and the ED nozzle in the first method was reduced, and the thrust become similar. The ED nozzle of the second method increased the thrust by increasing the nozzle exit velocity compared to the ED nozzle with 80% bell nozzle length.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.4
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• pp.12-24
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• 2020

The dual-throat nozzle is an extremely effective method in the thrust vectoring control field, utilizing another convergent section to connect with the divergent part of the conventional convergent-divergent nozzle. In the present research, the numerical simulation is conducted to investigate the effects of the injection angle on thrust vectoring performance in a 3D supersonic nozzle. Five injection angles are discussed and core performance variations are analyzed, including the deflection angle, injected mass flow ratio, system resultant thrust ratio, efficiency, Mach number contour and streamline on the symmetry plane, and Mach number contours at different slices. Meaningful conclusions are offered for fighter jet designers.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2002.04a
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• pp.31-32
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• 2002

임계노즐(critical nozzle)은 유동을 유로 최소단면부에서 초크시켜, 질량유량을 계측하기 위한 일종의 유체기구로, 최근 다양한 분야에서 널리 활용되고 있다. 압축성 기체역학의 관계식에 의하면, 임계노즐을 통하는 기체유동의 이론적인 질량유량은 노즐 목의 직경, 노즐 상류의 온도와 압력 그리고 기체의 비열비 등의 함수로 주어진다 그러나 실제 유동에서는 점성과 열전달 등의 초과로 인하여, 이론적 질량 유량과 실제유량의 비 즉 유출계수(discharge coefficient)의 값은 1.0으로 되지 않는다.

• Journal of Aerospace System Engineering
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• v.11 no.5
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• pp.42-49
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• 2017

The solid rocket motor(SRM) consists of a motor case, igniter, propellants, nozzle, insulation, controller, and driving device. The liquid rocket propulsion systems(LRPSs) cools the nozzle by the fuel and oxidizer but SRM does not cool the nozzle. The nozzle of SRM is high temperature condition and high velocity condition so occurs the erosion by combustion gas. This erosion occurs the change of nozzle throat and reduces thrust performance of rocket. The material of Rocket nozzle is minimization of erosion and insulation effect and endure the shear force, high temperature and high pressure. The purpose of this study is to investigate the erosion characteristics of solid rocket nozzles by each combustion time. Through the structure inspection of Graphite and C-C composite, identify the characteristics of the microstructure before and after erosion.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.764-766
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• 2002

본 연구에서는 가스 차단기의 소전류 차단성능을 개선하기 위한 최적화 과정에 대해서 나타낸다. 목적함수는 절연내력과 극간 인가전압의 차이의 최소값으로 선정하였으며, 목적함수가 최대가 되도록 최적화를 수행한다. 설계 변수로는 개극 전의 전극 이동길이, 노즐목 길이 및 노즐목 발산각과 노즐 하류장 형상을 채택하였다. 최적화 알고리즘으로는 (1+1) 진화알고리즘을, 유동해석을 위해서는 FVFLIC법을 사용하였다. 최적화 결과로 얻어진 모델은 초기 모델에 비해 소전류 차단성능이 상당히 개선되었음을 확인할 수 있었다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.497-500
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• 2011

The experimental study of thermal stress in the solid rocket engine nozzle with two different materials, SCM-440 and STS-630, was evaluated. SCM-440 has lager temperature increasing rate and higher temperature at the nozzle expansion region than STS-630. Thermal barrier efficiency and endurance of Zirconia coating were evaluated after making two more nozzles coated by Zirconica. Both coated materials showed about 70 percent higher thermal barrier efficiency than uncoated nozzles. Therefore, Zirconia coating using plasma spray method was useful in thermal safety at supersonic nozzle.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.536-542
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• 2017

A great deal of difficulty is encountered in the thermo-mechanical analyses of nozzle assembly for solid propellant rocket motors. The main issue in this paper is the modeling of the boundary conditions and the connections between the various components-gaps, relative movements of the components, contacts, friction, etc. This paper evaluated the complex phenomena of nozzle assembly during burning time with co-simulation which include fluid, thermal surface reaction/ablation and structural analysis. The validity of this approach was verified by comparison of analysis results with measured strains.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.2
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• pp.46-52
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• 2006

Techniques used for thrust vector control in rocket motors are mainly classified nozzles installed mechanical interference on the expansive region of nozzle(such as jet tabs and jet vanes) and movable nozzles(such as ball&socket and flexible seal). Using the numerical analysis and cold-flow test, this paper evaluates the performance of supersonic nozzle with asymmetric entrance shape when the test nozzle, especially ball&socket, is tilted. Numerical result shows that the effect of the asymmetric entrance shape on the flow field is suddenly diminished at the nozzle throat and downstream is mostly free from the effect of asymmetric entrance shape. Although the calculated thrust and lateral force are less than those of cold-flow test, two results show a fairly good agreement. But the cold-flow test results indicate the effective angles calculated from measured forces are not agreement with the geometric angles.