• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.3
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• pp.325-333
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• 2012

An experimental study was carried out to determine the correlation between the internal flow in a circular nozzle and elliptical nozzles with the external flow. The flow rate, spray angle and drop size were measured under various conditions of the injection pressure. Numerical simulations were attempted to investigate the internal flow structure in the elliptical nozzles, because the experimental study was limited in its measurements of flow velocity and pressure distributions in the relatively small orifice. In the case of the elliptical nozzles, the disintegration characteristics of the liquid jet were significantly different from those of the circular nozzle. Surface breakup was observed at the jet issued from the elliptical nozzles with injection pressure. This is due to the internal flow structure, which is reattached to the orifice wall at the minor axis plane of the elliptical nozzle, unlike that observed with the circular nozzle.

• The Journal of the Acoustical Society of Korea
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• v.41 no.6
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• pp.698-704
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• 2022

In this paper, the radiated aerodynamic noise generated from sound sources of a nozzle inflow is quantitatively investigated and compared with experimental results of externally radiated noise. A high-resolution unsteady compressible Large Eddy Simulation (LES) technique is used to accurately predict the internal and external flow of three types of nozzle shape. Through using the vortex sound source for sound sources, the geometry of nozzle neck is identified as most significant aerodynamic noise sources. For validation of quantitative analysis, the vortex sound source intensity of internal nozzle flow is compared with results of external radiated noise of calculation and experiment.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.269-272
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• 2008

Internal flow field of supersonic nozzle with pintle, which control thrust of solid rocket motor, is very complicated by pintle tip shape and contour of nozzle. For studying of pintle nozzle performance by effects of internal flow field variation with pintle position, cold flow test and numerical analysis about needle type pintle shape were performed and results were presented in this paper. As the results of this study, three types of internal shocks exists in the pintle nozzle and oblique shock is oscillated by pintle position

• Journal of the Korean Society of Propulsion Engineers
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• v.7 no.3
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• pp.45-52
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• 2003

Detailed flowfield resulting from the secondary sonic gas injection into a divergent section of supersonic conical nozzle has been numerically investigated. The three-dimensional flowfield associated with the bow-shock/boundary-layer interaction inside the nozzle has been solved by Reynolds-averaged Navier-Stokes equations with an algebraic and $\kappa$-$\varepsilon$ turbulence model. The numerical results have been compared with the experimental results for the identical flow conditions, and it is shown that the comparison is satisfactory Effects of different injection pressures of the secondary jet on the shock/boundary-layer interactions and the overall flow structure inside the nozzle have been investigated. The vortex structures behind the shock interaction and wall pressure variations have also been studied.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2002.04a
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• pp.14-15
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• 2002

기체역학 이론에 의하면, 노즐의 공급압력과 노즐의 상세형상이 주어지는 경우에 추진 노즐로부터 방출되는 제트유동의 추력을 예측할 수 있으며, 최대추력은 노즐 출구에서 유동이 적정팽창 상태로 될 때 얻어진다. 실제의 추진 로켓에서나 다른 비상체에서는 추력의 예측뿐만 아니라, 얻어지는 추력의 방향을 적절하게 조절하여 제어하는 것이 요구된다. 종래 추력벡터 제어를 위해서 많은 연구들이 수행되었다. 일례로 추진노즐 내부에 베인(vane) 등을 삽입하여, 추력벡터를 조절하거나, 추진 노즐을 가변(movable nozzle)으로 하는 방법, 그리고 노즐내부에 2차 유동을 분사(secondary flow injection)하여 평균 추력벡터를 제어하는 방법 등이 제안되어 응용되어 왔다.

• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.2
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• pp.35-41
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• 2009

Both the nozzle expansion ratio and the chamber pressure are simultaneously and continuously changed according to pintle movement, resulting in a different internal flow structure and flow separation characteristics. In this paper, the pintle position effect on nozzle flow structure and separation phenomena is analyzed by experimental-aided Computational Fluid Dynamic(CFD). Among the turbulent models for RANS(Reynold Averaged Navier Stokes) in Fluent, Spalart-Allmaras model is better agreement with the nozzle wall pressure distribution attained by cold-flow test than other models. And even if a conical nozzle is used, there is a shock structure similar to cap-shock pattern mainly occurred in contoured or shaped optimized nozzle because of internal shock generated from pintle tip flow separation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2002.04a
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• pp.44-45
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• 2002

일반적으로 노즐이나 오리피스로부터 방출되는 초음속 단일 자유제트 유동의 경우, 제트내부에서 발생하는 충격파 시스템이나, 제트경계의 형상 그리고 제트코어의 길이 및 초음속 영역의 길이 등은 종래의 연구로부터 비교적 잘 알려져 있다. 이들 연구에 의하면, 제트의 압력비가 어느 정도 증가하게 되면, 노즐 하류에서 제트내부에는 마하 디스크가 발생하게 되며, 제트유동은 압축과 팽창을 반복하는 구조로 된다. 또 노즐 출구로부터 마하 디스크까지의 거리와 마하 디스크의 직경 등은 노즐의 압력비의 함수로 주어진다고 알려져 있다.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.3
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• pp.1-13
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• 2021

Effects of the nozzle wall angles on the supersonic flow field in a thrust optimized nozzle were numerically investigated. The combustor and operating condition of 30-tonf rocket engine was selected to study the optimum nozzle shape. The nozzle flow of combustion products was realized by the shifting equilibrium calculation for the propellant of kerosene-LOx. The change of nozzle wall angles induced different developing patterns of the internal and secondary shock wave. The optimum nozzle was obtained when the internal shock was in a specific position at the nozzle outlet. The nozzle wall angles of the optimum nozzle were very similar to those of the optimum nozzle which does not consider the shock wave.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2000.11a
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• pp.32-32
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• 2000

3단형 과학로켓의 고체모타의 내부 유동을 추진제의 연소에 따라 내부형상이 변화하는 과정에 대해 수치해석 하였다. 추진제는 표면에서 균일하게 연소된다고 가정하였으며 연소거리가 0.1mm, 30mm, 60mm, 90mm인 경우의 고체모타 내부 물리량 변화를 관찰하였다. 연소가 진행되며 잠입형 노즐의 위 부분에 큰 재순환 영역이 생기는 것이 관찰되었으며 노즐에 작용하는 압력 힘을 구하여 본 결과 노즐부의 모멘트 힘은 크지 않은 것으로 판명되었다.(중략)

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.662-665
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• 2011

Pintle technology, which is one of the thrust control method for solid rocket motor, can control the thrust by the control of nozzle throat area through the pintle moving. For studying the unsteady flow characteristics of pintle nozzle by needle type pintle moving, cold flow test and numerical analysis were performed. The pressure distribution on the pintle tip was varied for pintle moving and stopping and thrust was varied by this effects.