• 한국추진공학회지
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• 제14권6호
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• pp.9-16
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• 2010

고체연료 램제트 추진의 경우 간단한 구조에 비해 높은 성능과 추진력을 얻을 수 있는 매력적인 추진기관이다. 본 연구의 목적은 두가지 유형의(스파이크 & 피토) 흡입구에 대한 공기역학적 특성을 파악함에 있다. 마하수 3.0의 실험조건에서 연소실의 압력과 $0^{\circ}$와 $4^{\circ}$의 받음각의 변화에 따라 흡입구 벽면의 압력값을 측정하였다. 본 연구는 초음속 유동장치와 쉴리렌 시스템을 이용하여 수행되었으며 동일 실험조건에서 스파이크 형이 피토 형보다 약 2배 높은 전압력 회복율을 나타내었다. 전산유체 해석을 통하여 흡입구 내부흐름을 실험결과 값과 비교 분석하였다.

• 한국해양공학회지
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• 제19권6호통권67호
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• pp.72-77
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• 2005

The materials used in a ship screw propeller are commonly made with brass. The seawater corrosion and seawater cavitation of the screw propeller reduces the propulsive performance of the ship. In screw manufacturing, the corrosion rust of the screw propeller is removed through a hand grinding method. The grinding process produces dust of the heavy metals from the brass. The dust creates a poor working environment that is harmful to the health of the workers. An automatic corrosionrust removing apparatus, using a blasting method, was developed for the improvement of screw polishing conditions and its working environment. The performance of this apparatus was investigated by surface roughness, weight loss rate, hardness, electrochemical corrosion resistance, and cavitation erosion, after removing of the corrosion rust under various blasting conditions. Two medias of alumina and emery were used in this experiment. The surface roughness and hardness of the screw were improved by this apparatus. The electrochemical corrosion potential (Ecorr) and current density (Icorr) were measured by the dynamic polarization method, using a potentiostat,under the conditions of surface polishing with grinding, blasting, wire brushing, and fine sand papering. The test results prove that the new corrosion rust-removing apparatus improves the surface performance of a screw propeller.

• 대한조선학회논문집
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• 제32권2호
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• pp.68-74
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• 1995

선박의 초기설계 단계에서 저항 추진 성능을 손쉽고도 정확히 추정하기 위해 통계해석 기법을 유용하게 사용하고 있다. 본 연구에서는 저항추진 성능 추정 프로그램에 필요한 기능들과 데이터뱅크의 구조를 제안하였다. 개발된 프로그램에는 저항 추진 계수를 추정하기 위한 여러 가지 도표와 회귀식이 포함되어 있으며, 데이터 뱅크를 이용한 일관회귀분석도 포함되어 있다. 또한 프로펠러 주요치수와 단독효율을 추정하기 위한 프로펠러의 간략한 설계 과정도 포함되어 있다. 프로그램의 기능과 데이터 뱅크의 정도를 검증하기 위해 임의의 선형 14 척에 대한 추정을 수행하였으며, 5% 이내의 좋은 추정 정도를 보여주고 있음을 확인하였다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제6권4호
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• pp.965-980
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• 2014

This paper presents a new estimation method of full scale propulsive performance for the pulling type podded propeller. In order to estimate the drag of pod housing, a drag velocity ratio, which includes the effects of podded propeller loading and Reynolds number, is presented and evaluated through the comparison of model test and numerical analysis. By separating the thrust of propeller blade and the drag of pod housing, extrapolation method of pod housing drag to full scale is deduced, and correction method of propeller blade thrust and torque to full scale is presented. This study utilized the drag coefficient ratio of the pod housing as a measure for expanding it to full scale, but in order to increase the accuracy of performance evaluation, additional study is necessary on the method for the full scale expansion via separating the drag of pod body, strut and fin which consist the pod housing.

• International Journal of Naval Architecture and Ocean Engineering
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• 제5권2호
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• pp.287-301
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• 2013

The present paper deals with the problems of yaw angle effects on podded propulsor performance. The study aims at providing insights on characteristics of podded propulsors in azimuthing condition. In this regard, a wide numerical simulation that concerned yaw angle effect measurement on podded propeller performance was performed. The Reynolds-Averaged Navier Stokes (RANS) based solver is used in order to study the variations of hydrodynamic characteristics of podded propulsor at various angles. At first, the propeller is analyzed in open water condition in absence of pod and strut. Next flow around pod and strut are simulated without effect of propellers. Finally, the whole unit is studied in zero yaw angle and azimuthing condition. Structured and unstructured mesh techniques are used for single propeller and podded propulsor. The performance curves of the propeller obtained by numerical method are compared and verified by the experimental results. The characteristic parameters including the torque and thrust of the propeller, the axial force and side force of unit are presented as function of velocity advance ratio and yaw angle. The results shows that the propeller thrust, torque and podded unit forces in azimuthing condition depend on velocity advance ratio and yaw angle.

• 한국추진공학회지
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• 제9권1호
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• pp.1-8
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• 2005

설계단계에서 수행되는 액체로켓엔진의 추력실 형상설계와 성능예측을 위하여 화학평형을 고려한 축대칭 압축성 해석코드를 개발하였다. 사용자의 편리함과 효율성에 중점을 두었으며, 형상파라미터의 입력값에 따라 자동으로 격자를 생성하고 연소실 조건은 추진제 조합, 연소압 그리고 혼합비를 지정함으로서 내부에서 계산하게 된다. 따라서 설계자는 추력실 형상 및 작동조건을 변화시켜 각각의 설계변수가 추력성능에 미치는 영향을 빠르고 손쉽게 파악할 수 있도록 하였다. CEA의 결과, JPL 노즐의 실험결과, 두 종류의 LRE 실제 엔진 자료, 그리고 KSR-III의 설계점 및 탈설계점 연소시험결과와 비교함으로서, 다양한 측면에서 해석코드의 정확도와 적용성을 평가하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제31회 추계학술대회논문집
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• pp.310-313
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• 2008

스크램젯 비행체에서 극초음속 순항미사일의 추진 특성을 향상시키고 항력을 적게 발생하면서 전력을 생산하는 장치로써 MHD 장치가 최근 들어 큰 관심을 받아왔다. 이전에 보였던 것보다 보다 완전한 물리적 모델을 바탕으로 하면, 경계층 박리 억제나 파워 바이패스를 통해 극초음속 추진 시스템의 성능 향상을 하는 MHD의 쓰임새를 논의하는 것은 불필요한 일이 된다. MHD 유동 제어를 하게 되면 엔진 성능에 상당한 역효과를 미치는 불가피한 Joule 가열이 크게 발생한다. 하지만, 예비 조사에 따르면 MHD는 약간의 항력만을 더 발생하면서 스크램젯 엔진을 장착한 무기에 메가와트 단위의 큰 전력을 생산해 낼 수 있을 것으로 여겨진다.

• 한국해양공학회지
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• 제26권3호
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• pp.1-5
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• 2012

A complex energy saving device has been developed for middle class vessels. The propulsive performance of the developed device is described through a model test. The pre-swirl stator, which recovers the rotational energy of the propeller slipstream, is a well-known energy saving device for large vessels. The pre-swirl stator for a large vessel is usually cast as a part of the stern frame and has a high cost. The manufacture of a cast stator for an existing vessel is almost impossible. The complex device that was developed can be fitted on astern frame by welding. The model tests show a 4-6% efficiency gain for middle class vessels with the developed appendages compared to those with bare hulls.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 춘계학술대회논문집
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• pp.27-30
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• 2009

The aerodynamic performance of aircraft in icing condition can deteriorate considerably by contamination of aerodynamic and propulsive systems due to icing accretions on aircraft surfaces. A computational analysis based on the Eulerian description was performed on an airfoil to investigate effects of ice accretions on airfoil aerodynamics. A water droplet with liquid water concentration ($0.00075kg/m^3$) and mean volume diameter ($20{\mu}m$) was considered and applied to various angles of attack to investigate the stall angle decrease and the drag increment.

• 대한조선학회지
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• 제20권4호
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• pp.25-32
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• 1983

A series of model testes on a container ship in regular were executed. This paper presents the results of resistance, self-propulsion, and ship motion tests. The experimental results of ship motion measured on a towed model and a self-propelled model were compared with those of Japanese's model test showing fairly good agreements. The results of added resistance tests were compared with those of Japanese' model test and also compared with the calculation results by Gerritsma's method showing somewhat large discrepancies at higher speeds. Also the results of added resistance tests measured on a fixed model were compared with the calculation results by Gerritsma's method. Finally the results of self-propulsion tests were presented.