• Advances in aircraft and spacecraft science
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• 제3권4호
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• pp.367-378
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• 2016

Thrust Vectoring is a dynamic feature that offers many benefits in terms of maneuverability and control effectiveness. Thrust vectoring capabilities make the satisfaction of take-off and landing requirements easier. Moreover, it can be a valuable control effector at low dynamic pressures, where traditional aerodynamic controls are less effective. A numerical investigation of Fluidic Thrust Vectoring (FTV) is completed to evaluate the use of fluidic injection to manipulate flow separation and cause thrust vectoring of the primary jet thrust. The methodology presented is general and can be used to study different techniques of fluidic thrust vectoring like shock-vector control, sonic-plane skewing and counterflow methods. For validation purposes the method will focus on the dual-throat nozzle concept. Internal nozzle performances and thrust vector angles were computed for several range of nozzle pressure ratios and fluidic injection flow rate. The numerical results obtained are compared with the analogues experimental data reported in the scientific literature. The model is integrated using a finite volume discretization of the compressible URANS equations coupled with a Spalart-Allmaras turbulence model. Second order accuracy in space and time is achieved using an ENO scheme.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.630-631
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• 2009

Recent developments such as concern over global warming, depletion of fossil fuels and increase in energy demands by the increasing world population has eventually lead to mass production of electricity using renewable sources. Apart from wind and solar, ocean holds tremendous amount of untapped energy in forms such as geothermal vents, tides and waves. The current study looks at generating power using waves and the focus is on the primary energy conversion (first stage conversion) of incoming waves for two different models. Observation of flow characteristics, pressure and the velocity in the augmentation channel as well as the front guide nozzle are presented in the paper. A numerical wave tank was utilized to generate waves of desired properties and later the turbine section was integrated. The augmentation channel consisted of a front nozzle, rear nozzle and an internal fluid region representing the turbine housing. The analysis was performed using the commercial CFD code.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 춘계학술대회 논문집
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• pp.311-314
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• 2009

고체추진기관의 연소 환경에서 복잡한 형상을 갖는 내열 복합재료의 온도 및 밀도분포를 예측할 수 있는 방법을 개발하였다. 복합재료의 내부 열반응은 Arrhenius 모델을 이용하였으며, 표면 삭마반응은 Zvyagin 이론을 사용하였다. 표면 삭마에 의한 경계조건 및 격자 이동은 Rezoning 기법을 사용하였으며 열분해에 의한 흡열반응 효과는 열분해 가스의 조성비에 기준한 유효 비열 값을 이용하여 계산되었다. 형상이 복잡한 부품으로 이루어진 2차원 축대칭 노즐 조립체에 적용된 방법은 향후 3차원 FEM 열구조 해석에 활용을 목표로 발전될 것이다.

• 한국기계가공학회지
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• 제20권2호
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• pp.38-44
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• 2021

To cater to the transition from single-color to multicolor/multi-material printing, this paper proposes a cartridge-replacing type multi-nozzle Fused Depositon Modeling(FDM) three-dimensional (3D) printer. In the test printing run, tool change failure/wobble/layer shift occurred. It was confirmed that improper support was the cause of this tool change failure. As a solution, spline and electromagnetic cartridges were designed. Wobble was caused by machine vibration and the motor stepping out. To minimize wobble, an additional Z-axis was installed, and the four-point bed leveling method was used instead of the three-point bed leveling method. The occurrence of layer shift was ascribed to the eccentricity of the Z-axis lead screw. Therefore, slit coupler was replaced with an Oldham type. In addition to the mechanical supplementation, the control environment was integrated to prevent accidents and signal errors due to wire connections. Before the final test printing run, a rectifier circuit was added to the motor to secure precise control stability. The final test printing run confirmed that the wobble/layer shift phenomenon was minimized, and the maximum error between layers was reduced to 0.05.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제29회 추계학술대회논문집
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• pp.225-228
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• 2007

마이크로 고체 추진제 추력기는 현재의 MEMS 기술로 가장 실현 가능성이 높은 마이크로 추력기이다. 마이크로 고체 추진제 추력기의 기본 요소로는 마이크로 노즐, 마이크로 점화기, 연소 챔버 그리고 고체 추진제이다. 마이크로 노즐과 연소 챔버는 감광유리의 이방성 식각을 통해 제작이 되었다. 마이크로 점화기는 마이크로 유리 박막 백금 히터를 사용하였다. 요소들의 제작 공정을 확립 후, 요소들을 통합하여 추력기를 개발하였다. 추력기의 연소 실험을 수행하여 성공적으로 연소가 일어남을 확인하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제34회 춘계학술대회논문집
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• pp.113-122
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• 2010

고체추진기관의 연소 환경에서 복잡한 형상을 갖는 내열 복합재료의 온도, 밀도분포 및 삭마두께를 예측할 수 있는 방법을 개발하였다. 복합재료의 내부 열반응은 Arrhenius 모델을 이용하였으며, 표면 삭마반응은 Zvyagin 이론을 사용하였다. 표면 삭마에 의한 경계조건 및 격자 이동은 상용해석 코드에서 활용되는 Rezoning-remeshing 기법을 사용하였다. 형상이 복잡한 부품으로 이루어진 2차원 축대칭 노즐 조립체에 적용된 방법은 향후 3차원 FEM 열구조 해석에 활용을 목표로 발전될 것이다.

• Nuclear Engineering and Technology
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• 제48권1호
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• pp.175-181
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• 2016

This study investigates the dispersibility of carbon in carbon contained ammonium diuranate (C-ADU) gel particles and the characteristics of C-ADU gel liquid droplets produced by the vibrating nozzle and integrated aging-washing-drying equipment. It was noted that the excellent stability of carbon dispersion was only observed in the C-ADU gel particle that contained carbon black named CB 10. ADU gel liquid droplets containing carbon particles with the excellent sphericity of approximately 1,950 mm were then obtained using an 80-100-Hz vibrating nozzle system. Dried C-ADU gel particles obtained by the aging-washing-drying equipment were thermal decomposed until $500^{\circ}C$ at a rate of $1^{\circ}C/min$ in an air or in 4% $H_2$ gas atmosphere. The thermally decomposed C-ADU gel particles showed 24% weight loss and a more complicated profile than that of ADU gel particles.

• Journal of Advanced Marine Engineering and Technology
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• 제32권6호
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• pp.869-876
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• 2008

A thermocompressor is the equipment which compresses a vapor to a desired discharge pressure. Since it was first used as the evacuation pump for a surface condenser, it has been widely adopted for energy saving systems due to its high working confidence. In the present study, the geometrical analysis of the shape between the jet nozzle and the diffuser inlet, the drag force was calculated by means of the integrated equation of motion and the computational fluid dynamic (CFD) package called FLUENT. The computer simulations were performed to investigate the effects by the various suction flow rates, the distance from jet nozzle outlet to the diffuser inlet and the dimensions of the diffuser inlet section through the iterative calculation. In addition, the results from the CFD analysis on the thermocompressor and the experiments were compared for the verification of the CFD results. In the case of a jet nozzle, the results from the CFD analysis showed a good agreement with the experimental results. Furthermore, in this study, a special attention was paid on the performance of the thermocompressor by varying the diffuser convergence angle of $0.0^{\circ}$, $0.5^{\circ}$, $1.0^{\circ}$, $2.0^{\circ}$, $3.5^{\circ}$ and $4.5^{\circ}$. With the increase of the diffuser convergence angle. the suction capacity was improved up to the degree of $1.0^{\circ}$ while it was decreased over the degree of $1.0^{\circ}$.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2003년도 제20회 춘계학술대회 논문집
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• pp.127-130
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• 2003

This paper presents the numerical thermal analysis for regeneratively cooled rocket thrust chambers. An integrated numerical model incorporates computational fluid dynamics for the hot-gas thermal environment, and thermal analysis for the liner and coolant channels. The flow and temperature fields in rocket thrust chambers is assumed to be axisymmetric steady state which is presumed to the combustion liner. The heat flux computed from nozzle flow is used to predict the temperature distribution of the combustion liner. As a result, we present the wall temperature of combustion liner and the temperature change of coolant.

• 한국추진공학회지
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• 제4권1호
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• pp.74-92
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• 2000

A numerical analysis has been conducted to study the transient flowfield during the transition from the booster to sustainer phase in an integrated rocket ramjet (IRR) propulsion system. Emphasis is placed on the unsteady inlet aerodynamics, fuel/air mixing in an entire ramjet engine during the flow transient phase. The computational geometry consists of the entire IRR engine, including the inlet, the combustion chamber, and the exhaust nozzle. Turbulence closure is achieved using a low-Reynolds-number two-equation model. The governing equations are solved numerically by means of a finite-volume, preconditioned flux-differencing scheme over a wide range of Mach umber. Various important physical processes are investigated systemically, including terminal shock train.