• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.282-287
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• 2001

The CSCM Upwind method and Material Transport Analysis (MTA) have been used to predict the thermal response and ablation rate for non-charring material to be used as thermal protection material (TPM) in KSR-III test rocket nozzle. The thermal boundary conditions such as cold wall heat-transfer rate and recovery enthalpy for MTA code are obtained from the upwind Navier-Stokes solution procedure. The heat transfer rate and temperature variations at rocket nozzle wall were studied with shape change of the nozzle surface as time goes by. The surface recession was severely occurred at nozzle throat and this affected nozzle performance such as thrust coefficient substantially.

• International Journal of Fluid Machinery and Systems
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• 제1권1호
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• pp.47-56
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• 2008

The flow behind the variable area nozzle which corresponds to the flow at the leading edge of the impeller was measured with a 3-hole yaw probe and calculated with CFD. Two nozzle throat-areas were investigated. One is the smallest and the other is the largest opening for the variable nozzle. Test results agreed with the calculated results qualitatively. The leakage flow through the tip clearance of the nozzle vane significantly affected the flow field downstream of the nozzle vane with the smallest opening. However, the effect on leakage flow on the flow field downstream of the nozzle vane with the largest opening was very weak and the effect of wake is dominant.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.2127-2132
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• 2003

A computational study is performed to better understand the choke phenomenon of unsteady gas flow through a critical nozzle. The axisymmetric, unsteady, compressible, Navier-Stokes equations are solved using a finite volume method. In order to simulate the effects of back pressure fluctuations on the critical nozzle flow, a forced sinusoidal pressure wave is assumed downstream the exit of the critical nozzle. It's frequency is 20kHz and amplitude is varied below 15% of time-mean back pressure. The results obtained show that for low Reynolds numbers, the unsteady effects of the pressure fluctuations can propagate upstream of the throat of critical nozzle, and thereby giving rise to applicable fluctuations of mass flow through the critical nozzle. The effect of the amplitude of the excited pressure fluctuations on the choke phenomenon is discussed in details.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 A
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• pp.349-350
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• 1999

Two of the factors to be considered at the design stage of the extinction chamber have been examined numerically. one is the sectional area of puffer cylinder, another is that of nozzle throat. the variation of the sectional area of puffer cylinder allowed us to find the size optimal at the interrupting performance. it is shown that the sizes of nozzle throat influenced the pressure rise of puffer cylinder strongly.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제36회 춘계학술대회논문집
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• pp.153-156
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• 2011

노즐목 가변 추력기에 적용할 목적으로 4가지 핀틀 형상을 사용하여 정상상태의 공압시험을 수행하였다. 실험결과 핀틀의 전진에 따라 추력 조절이 가능함을 확인하였다. 그러나, 추력기 성능에 대한 핀틀 형상 효과에 대한 결론을 내리기에는 아직 시기상조이다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2000년도 추계 학술대회논문집
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• pp.54-59
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• 2000

A numerical study of axisymmetric rocket main nozzle flow has been accomplished. The CSCM upwind flux difference splitting method with an iterative time marching scheme having second order accuracy in time and space has been used to simulate unsteady flow characteristics in an axisymmetric rocket main nozzle. Though the pressure vary at nozzle inlet with the lapse of time, Mach No. and the density were not changed significontly compared with the temperature. Specific heat ratio $\gamma$=1.134 predicted higher temperature at nozzle throat and exit and nondimensional thrust coefficients at exit than specific heat ratio $\gamma$=1.4 did.

• 항공우주시스템공학회지
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• 제14권4호
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• pp.1-9
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• 2020

The characteristics of an aerospike pintle nozzle system with excellent altitude compensation were analyzed using cold air testing. It was confirmed that reducing the stroke of the aerospike nozzle is effective in increasing the thrust. However, the results of additional numerical analysis indicated that the discharge coefficient factor was significantly lower at the maximum stroke. The Vena contracta due to the cowl reduction angle decreased the effective nozzle throat area at the maximum stroke and hindered expansion. Complementing the cowl design may thus increase the efficiency of a solid-propellant rocket engine that uses the aerospike pintle nozzle system.

• 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.

• Journal of Mechanical Science and Technology
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• 제15권12호
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• pp.1816-1821
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• 2001

Two-dimensional blow-down type supersonic wind tunnel was designed and built to investigate the transient behavior of the startup of a supersonic flow from rest. The contour of the divergent part of the nozzle was determined by the MOC calculation. The converging part of the nozzle, upstream of fille throat was contoured to make the flow uniform at the throat. The flow characteristics of the steady supersonic condition were visualized using the high-speed schlieren photography. The Mach number was evaluated from the oblique shock wave angle on a sharp wedge with halt angle of 5 degree. The measured Mach number was 2.4 and was slightly less than the value predicted by the design calculation. The initial transient behavior of the nozzle was recorded by a high-speed digital video camera with schlieren technique. The measured transition time from standstill to a steady supersonic flow was estimated by analyzing the serial images. Typical transition time was approximately 0.1sec.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제31회 추계학술대회논문집
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• pp.89-93
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• 2008

핀틀 형상과 위치가 고체 추진기관의 추력 성능에 미치는 영향을 공압 시험과 수치해석 기법으로 평가하였다. Fluent 해석 결과, Spalart-Allmaras 모델이 공압 시험에 얻은 노즐벽면 압력을 잘 모사하는 것으로 나타났다. 핀틀로 노즐목 크기를 감소시키면 추력은 증가하였으며, 핀틀 직경이 커질수록 핀틀 팁에 나타나는 재순환 영역의 압력에 의한 추력은 증가하지만 노즐 및 연소실 압력에 의한 추력은 감소하여 총 추력은 핀틀 직경이 작은 것 보다 감소하였다.