• Journal of Ship and Ocean Technology
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• 제6권1호
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• pp.27-33
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• 2002

Recently, the application of the electric propulsion system becomes popular because of its advantage over conventional propulsion. However, the complicated flow mechanism and interaction around the azimuth thruster are not fully understood yet, and the studies on the powering performance characteristics with azimuth/pod thrusters are now in progress. The experimental method developed in KRISO(Korea Research Institute of Ships & Ocean Engineering) is introduced and the results of the powering performance tests, consisting of resistance, self-propulsion and propeller open water tests for a cable layer with two azimuth thrusters are presented. For the analysis of powering performance with azimuth thrusters, it is necessary to evaluate the thrust/drag for components of a thruster unit, Extrapolation results could differ according to the various definitions of the propulsion unit; that is the pod, thruster leg and/or nozzle can be treated as hull appendages or as part of propulsion unit, The powering performances based on several definitions are investigated for this vessel. The results of the measurements for the 3-dimensional velocity distribution on the propeller plane are presented to understand the basis of the difference in propulsion characteristics due to the propeller rotational directions.

• 한국위성정보통신학회논문지
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• 제11권1호
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• pp.58-62
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• 2016

인공위성 추진시스템은 위성이 발사체와 분리되어 최종 임무궤도에 진입하기까지 궤도조정에 필요한 추력을 제공하고, 임무궤도에 진입한 이후에는 궤도경사각 제어 및 항력에 의한 궤도 저하를 보상하기 위한 추력을 제공한다. 위성 발사 후 초기운용 기간 동안 획득된 궤도운용결과를 바탕으로 위성의 운용모드에 따른 저궤도관측위성 추진시스템의 궤도성능 검증을 수행하였다. 또한 추진시스템을 구성하는 부품 및 배관에서의 온도변화 추이를 살펴 추진계가 정상적인 범위 내에서 운용되고 있음을 확인하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.456-459
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• 2008

The purpose of this paper is to examine the aerodynamic characteristics of three hypersonic configurations including pure liftbody configuration, pure waverider configuration and liftbody integrated with waverider configuration. Hypersonic forbodies were designed based on these configurations. For the purpose to integrate with ramjet or scramjet, all the forebodies were designed integrated with hypersonic inlet. To better understand the forebody performance, three dimensional flow field calculation of these hypersonic forebodies integrated with hypersonic inlet were conducted in the design and off design conditions. The computational results show that waverider offer an aerodynamic performance advantage in the terms of higher lift-drag ratios over the other two configurations. Liftbody offer good aerodynamic performance in subsonic region. The aerodynamic performance of the liftbody integrated with waverider configuration is not comparable to that of pure waverider in the terms of lift-drag ratios and is not comparable to that of pure liftbody in subsonic. But the liftbody integrated with waverider configuration exhibit good lateral-directional and longitudinal-directional stability characteristics. Both pure waverider and liftbody integrated with waverider configuration can provide relatively uniform flow for the inlet and offer good aerodynamic characteristics in the terms of recovery coefficient of total pressure and uniformity coefficient.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 1999년도 제13회 학술강연논문집
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• pp.33-33
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• 1999

The Coanda effect is the tendency for a fluid jet to atach itself to an adjacent surface and follow its contour without causing an appreciable flow separation. The jet is pulled onto the surface by the low pressure region which develops as entrainment pumps fluid from the region between the jet and the surface. Then the jet is held to the wall surface by the resulting radial pressure gradient which balance the inertial resistance of the jet to turning. The jet may attach to the surface and may be deflected through more than 180 dog, when the radius of the Coanda surface is sufficiently large compared to the height of the exhaust nozzle. However, if the radius of curvature is small, the jet turns through a smaller angle, or may not attach to the surface at all. In general, the limitations in size and weight of a device will limit the radius of the deflection surface. Thus much effort has been paid to improve the jet deflection in a variety of engineering fields. The Coanda effect has long been applied to improve aerodynamic characteristics, such as the drag/lift ratio of flight body, the engine exhaust plume thrust vectoring, and the aerofoil/wing circulation control. During the energy crisis of the seventies, the Coanda jet was applied to reduce vehicle drag and led to drag reductions of as much as about 30% for a trailer configuration. Recently a variety of industrial applications are exploiting another characteristics of the Coanda jets, mainly the enhanced turbulence levels and entrainment compared with conventional jet flows. Various industrial burners and combustors are based upon this principle. If the curvature of the Coanda surface is too great or the operating pressure too high, the jet flow will break away completely from the surface. This could have catastrophic consequences for a burner or combustor. Detailed understanding of the Coanda jet flow is essential to refine the design to maximize the enhanced entrainment in these applications.

• 한국추진공학회지
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• 제21권3호
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• pp.18-24
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• 2017

가스터빈엔진의 시동점화 조건 달성 및 시동가속을 위해서는 엔진에 적합한 시동기를 선정하여야 한다. 이를 위해서는 시동 크랭킹 과정의 공력저항을 예측하여 시동성능을 파악하여야한다. 본 논문에서는 기 개발엔진의 Coast down 시험을 통하여 획득된 엔진속도 프로파일 데이터를 바탕으로 엔진 주축에 인간되는 공력저항을 도출하고, 압축기 부하를 기준으로 한 스케일링을 통해 대상엔진의 공력저항을 모델링하였다. 이후, 공력저항 모델과 공기시동기(ATS)의 토크 성능선도를 엔진 시동모델에 적용함으로써, 엔진시동에 적합한 시동기를 선정하는 방법을 제시한다.

• 한국추진공학회지
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• 제18권4호
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• pp.50-60
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• 2014

초공동현상을 이용한 고속 수중 운동체와 함께 이를 가능하게 하는 기술로써 해수흡입 램젯 추진에 대한 연구가 여러 나라에서 진행되고 있다. 본 연구에서는 해수 흡입 램젯 엔진을 추진기관으로 하는 수중 운동체의 개념 설계를 진행하였다. 가동 환경을 확인하여 임무 작동 조건을 설정하였으며, 해당 조건 내에서 초공동현상 이론과 유체역학적 지식을 통해 운동체에 작용하는 항력을 예측하였다. 이로부터 필요 추력을 산출하여 추진기관의 대략적인 사이징과 부분별 성능해석을 수행하였으며, 설계한 추진기관의 추력 및 비추력 성능을 확인하였다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제10권6호
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• pp.730-740
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• 2018

Hydrofoil is the direct component to generate thrust for underwater glider. It is significant to improve propulsion efficiency of hydrofoil. This study optimizes the shape of a hydrofoil using Free-Form Deformation (FFD) parametric approach and Surrogate-based Optimization (SBO) algorithm. FFD approach performs a volume outside the hydrofoil and the position changes of control points in the volume parameterize hydrofoil's geometric shape. SBO with adaptive parallel sampling method is regarded as a promising approach for CFD-based optimization. Combination of existing sampling methods is being widely used recently. This paper chooses several well-known methods for combination. Investigations are implemented to figure out how many and which methods should be included and the best combination strategy is provided. As the hydrofoil can be stretched from airfoil, the optimizations are carried out on a 2D airfoil and a 3D hydrofoil, respectively. The lift-drag ratios are compared among optimized and original hydrofoils. Results show that both lift-drag-ratios of optimized hydrofoils improve more than 90%. Besides, this paper preliminarily explores the optimization of hydrofoil with root-tip-ratio. Results show that optimizing 3D hydrofoil directly achieves slightly better results than 2D airfoil.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제30회 춘계학술대회논문집
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• pp.71-76
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• 2008

본 연구에서는 아음속 영역에서 유도무기의 일반적 형상인 세장형 몸체를 갖는 서로 다른 선두부 형상의 두 모델을 이용하여 받음각에 다른 세장형 모델 윗면의 압력 분포를 측정하였다. 아음속 영역에서 서로 다른 선두부 형상을 갖는 두 모델의 받음각에 따른 공력실험 결과로 특정 받음각에서의 측력 및 요잉모멘트가 최대가 되는 것을 확인하였으며 비대칭 정상상태와 비대칭 비정상상태의 경계를 알 수 있었다. 또한 시간에 따른 측력, 항력 및 요잉모멘트의 결과로 같은 받음각이라도 선두부의 형상에 따라 안정성이 다른 결과를 보였다. 받음각에 따른 세장형 몸체 표면 압력 분포를 측정한 결과 받음각이 증가할수록 표면압력 분포는 비대칭적으로 형성됨을 알 수 있었다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.460-468
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• 2008

Recent activities on the scramjet and rocket-ramjet combined-cycle engine of Japan Aerospace Exploration Agency(JAXA) are herein presented. The scramjet engines and combined-cycle engines have been studied in the world and JAXA has also studied such the engines experimentally, numerically and conceptually. Based on the studies, 2 to 3 m long, hydrogen-fueled engine models were designed and tested at the Ramjet Engine Test Facility(RJTF) and the High Enthalpy Shock Tunnel(HIEST). A scramjet engine model was tested in Mach 10 to 14 flight condition at HIEST. A 3 m long scramjet engine model was designed to reduce a dissociation energy loss in a high temperature condition. Drag reduction by a tangential injection and two ways of a transverse fuel injection were examined. Combustor model tests at three operating modes of the combined-cycle engine were conducted, demonstrating the combustor operation and producing data for the engine design at each mode. Aerodynamic engine model tests were conducted in a transonic wind tunnel, demonstrating the engine operation in the ejector-jet mode. A 3 m long combined-cycle engine model has been tested in the ejector-jet mode and the ramjet mode since March 2007. Carbon composite material was examined for application to the engines. Production of the cooling channel on a nickel alloy plate succeeded by the electro-chemical etching.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.546-549
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• 2008

Institute of Space and Astronautical Science of Japan Aerospace Exploration Agency(ISAS/JAXA) successfully developed and operated the microwave discharge ion engines onboard Hayabusa asteroid explorer. The ${\mu}10$ ion engines feature the cathode-less plasma generation in both the ion generators and neutralizers with the results of long life and high reliability in space. Based on the space achievements of ${\mu}10$ ion engines with 8mN thrust, 3,000sec Isp and 350W consumption power, several programs are currently under developments: ${\mu}20$, ${\mu}10$HIsp and ${\mu}1$. The first is a 20-cm diameter microwave discharge ion engine, aiming to achieve 30mN/kW in the thrustto-power ratio for the asteroid sample return mission larger than Hayabusa. The second is a high Isp version of ${\mu}10$, and exhausts the plasma beam over 10,000sec Isp using 15kV acceleration voltage for deep space missions to such as Jupiter and Mercury. The third is ${\mu}1$ to be adapted to small satellites for drag-free.