• 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.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2004년도 Proceedings of 2004 Korea-Japan Joint Seminar on Particle Image Velocimetry
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• pp.75-80
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• 2004

Aerospike nozzles have been expected to be used for an engine of a reusable space shuttle to respond to growing demand for rocket-launching and its cost reduction. In this study, the flow field structures in any cross sections around clustered linear aerospike nozzles are visualized and analyzed, using laser induced fluorescence (LIF) of nitrogen monoxide seeded in the carrier gas of nitrogen. Since flow field structures are affected mainly by pressure ratio, the clustered linear aerospike nozzle is set inside a vacuum chamber to carry out the experiments in the wide range of pressure ratios from 75 to 200. Flow fields are visualized in several cross-sections, demonstrating the complicated three-dimensional flow field structures. Pressure sensitive paint (PSP) of PtTFPP bound by poly- IBM -co-TFEM is also applied to measurement of the complicated pressure distribution on the spike surface, and to verification of contribution of a truncation plane to the thrust. Finally, to examine the effect of the sidewalls attached to the aerospike nozzle, the flow fields around the nozzle with the sidewalls are compared with those without sidewalls.

• Advances in aircraft and spacecraft science
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• 제6권3호
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• pp.225-238
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• 2019

A spike attached to a blunt nosed body significantly alters its flow field and influences the aerodynamic coefficients at hypersonic speed. The basic body is an axisymmetric, with a hemisphere nose followed by a cylindrical portion. Five different types of spikes, namely, conical aerospike, hemisphere aerospike, flat-face aerospike, hemisphere aerodisk and flat-face aerodisk are attached to the basic body in order to assess the aerodynamic characteristic. The spiked blunt body without the aerospike or aerodisk has been set to be a basic model. The coefficients of drag, lift and pitching moment were measured with and without blunt spike body for the length-to-diameter ratio (L/D) of 0.5, 1.0, 1.5 and 2.0, at Mach 6 and angle of attack up to 8 degrees using a strain gauge balance. The measured forces and moment data are employed to determine the relative performance of the aerodynamic with respect to the basic model. A maximum of 77 percent drag reduction was achieved with hemisphere aerospike of L/D = 2.0. The comparison of aerodynamic coefficients between the basic model and the spiked blunt body reveals that the aerodynamic drag and pitching moment coefficients decrease with increasing the L/D ratio and angle of attack but the lift coefficient has increasing characteristics.

• Advances in aircraft and spacecraft science
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• 제7권4호
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• pp.371-385
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• 2020

A forward-facing aerospike attached to a payload fairing of a satellite launch vehicle significantly alters its flowfield and decreases the aerodynamic drag in transonic and low supersonic speeds. The present payload fairing is an axisymmetric configuration and consists of a blunt-nosed body along with a conical section, payload shroud, boat tail and followed by a booster. The main purpose of the present numerical simulations is to evaluate flowfield and assess the performance of aerodynamic drag coefficient with and without aerospike attached to a payload fairing of a typical satellite launch vehicle in freestream Mach number range 0.8 ≤ M_∞ ≤ 3.0 and freestream Reynolds number range 33.35 × 10⁶/m ≤ Re_∞ ≤ 46.75 × 10⁶/m whichincludes the maximum aerodynamic drag and maximum dynamic conditions during ascent flight trajectory of the satellite launch vehicle. A numerical simulation has been carried out to solve time-dependent compressible turbulent axisymmetric Reynolds-averaged Navier-Stokes equations. The closure of the system of equations is achieved using the Baldwin-Lomax turbulence model. The aerodynamic drag reduction mechanism is analysed employing numerical results such as velocity vector plots, density and Mach contours in conjunction with the experimental flow visualization pictures. The variations of wall pressure coefficient over the payload fairing with and without aerospike are exhibiting different kind of flowfield characteristics in the transonic and low supersonic speeds. The numerically computed results are compared with schlieren pictures, oil flow patterns and measured wall pressure distributions and exhibit good agreement between them.

• 항공우주시스템공학회지
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• 제16권4호
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• pp.1-9
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• 2022

에어로 스파이크 핀틀 노즐의 구동으로 인한 탈설계 조건에서의 추력 감소를 저감하고자 설계인자 분석 연구를 수행하였다. Close (NPR 100), open (NPR 11) 스트로크 모두 부족팽창 조건으로 고정되었다. 설계인자로 핀틀 형상, 핀틀 헤드 반경 (R), 덮개 각도 (θ), 덮개 출구 길이 (L)를 선정하였다. 검증된 수치해석 기법으로 설계인자로 인한 추력 변화를 분석하였다. 먼저 핀틀 헤드 반경과 덮개 출구 길이는 추력에 미치는 영향이 적었다. 덮개 각도는 유효 노즐목 면적에 영향을 주어 질량 유량을 변화시키고, 덮개 출구에서의 역압력 구배를 생성하였다. 이중 에어로 스파이크 형상을 적용한 결과, 탈설계 조건에서의 추력이 기준 case 대비 약 1.2%, 가장 악조건인 case 대비 약 3.4% 증가하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.616-617
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• 2010

추력조절이 용이한 SNECMA의 추력기에 대해서 수치해석 기법으로 분석하였다. 특허에 제시된 Aerospike 노즐의 형상은 고도에 따라 최적의 추력이 가능하도록 설계되었다.

• 한국가시화정보학회지
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• 제10권1호
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• pp.47-54
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• 2012

Single Stage To Orbit (SSTO) missions which require its engines to be operated at varying back pressure conditions, use engines operate at high combustion chamber pressures (more than 100bar) with moderate area ratios (AR 70~80). This ensures that the exhaust jet flows full during most part of the operational regimes by optimal expansion at each altitude. Aero-spike nozzle is a kind of altitude adaptation nozzle where requirement of high combustion chamber pressures can be avoided as the flow is adapted to the outside conditions by the virtue of the nozzle configuration. However, the thrust prediction using the conventional thrust equations remains to be a challenge as the nozzle plume shapes vary with the back pressure conditions. In the present work, the performance evaluation of a new aero-spike nozzle is being carried out. Computational studies are carried out to predict the thrust generated by the aero-spike nozzle in varying back pressure conditions which requires the unsteady pressure boundary conditions in the computational domain. Schlieren pictures are taken to validate the computational results. It is found that the flow in the aero-spike nozzle is mainly affected by the base wall pressure variation. The aerospike nozzle exhibits maximum performance in the properly expanded flow regime due to the open wake formation.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제23회 추계학술대회 논문집
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• pp.43-46
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• 2004

에너지원으로써 압축공기만을 사용하는 공기역학 점화기의 주요 구성요소 중 노즐부에 관한 실험 연구로써 노즐로 초음속 노즐과 스파이크 노즐을 사용하여 각각의 구조적인 특성을 소개하고 최대 가열온도를 주요 성능 특성으로 하여 고찰한 실험결과를 나타내고 있다. 초음속 노즐은 기존의 음속노즐의 사용에 비해 동일한 유량으로 보다 높은 온도에 더 마르고 도달하며, 스파이크 노즐의 사용을 통해 작동유량의 넓은 변화범위에서도 근 성능저하 없이 사용할 수 있는 특성을 확인할 수 있다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.408-413
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• 2004

Numerical and experimental investigation were car-ried out to clarify the flow structure of underexpanded jet from a square nozzle. The square nozzle rep-resents one of the clustered combustors of a linear aerospike engine. From the numerical results, the three-dimensional shock wave of the underexpanded square jet was found to be composed of two shocks. One is the intercepting shock which corresponds to the shock observed in two-dimensional planar jet. The other is the recompression shock divided into two types. The expansion fans coming from the nozzle edges interact with each other at the comers of the nozzle exit, and overexpanded regions are generated. Therefore one of the two recompression shocks is formed at the comers of the nozzle exit behind the overexpanded regions. As the jet goes downstream, the overexpanded regions grow larger to coalesce at the symmetry planes. Then, the other type of the recompression shock is generated. The three-dimensional shock structure formed by the intercepting shock and the recompression shocks dominates the expansion of the jet boundary. The shock detection algorithm us-ing CFD results was developed to reveal the relation between the shock waves and the jet boundary, and it was found that the cross-sectional jet shape becomes cross-shape. The key features observed in the numerical investigation were verified by the experimental results. The shock structure at the diagonal plane was in good agreement with the experimental schlieren images. Moreover, the cross-sections visualized by the Mie scattering method confirmed that the cross-section of the jet becomes cross-shape.

• 한국추진공학회지
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• 제23권3호
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• pp.28-34
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• 2019

공압시험용 플러그 노즐 구동에 따른 추력제어, 핀틀 형상 및 작동압력에 따른 유동특성 분석을 수행하였다. 이를 위해 시험에서의 유동구조와 추력계수를 비교함으로써 수치해석의 타당성을 확인하였다. 이후 각 노즐형상이 설계의도지점에 노즐목이 형성됨과 원뿔형 노즐에 대하여 핀틀 구동만으로 1:8의 추력제어가 가능함을 확인하였다. 마지막으로 고도보정 효과가 뛰어난 에어로 스파이크 노즐일지라도, 너무 낮은 NPR에 맞춰 설계된 경우, 부족팽창 조건에서 불리할 가능성을 확인하였다.