• 대한조선학회논문집
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• 제42권5호
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• pp.427-434
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• 2005

The free surface influenced the wake behind a rotating propeller and its effects were investigated experimentally in a circulating water channel with the variation of water depth. Instantaneous velocity fields were measured using two-frame PIV technique and ensemble-averaged to study the phase-averaged flow structure in the wake region. For an isolated propeller, the flow behind the propeller is affected only by the propeller rotation speed, the leading on the blades and the proximity of the propeller to the free surface. The phase-averaged mean velocity fields show that the potential wake and the viscous wake developed on the blade surfaces. The interaction between the tip vortices and the slipstream causes the oscillating trajectory of tip vortices. The presence of the free surface greatly affected the wake structure, especially for propeller immersion depth of 0.6D. At small immersion depths, the free surface modified the tip and trailing vortices and the slipstream flow structure downstream of X/D = 0.3 in the propeller wake.

• 대한안전경영과학회지
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• 제19권4호
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• pp.301-307
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• 2017

The planing hull is characterized by a large change in the posture according to the speed, and the shape of the propeller varies, so that the hull resistance varies greatly depending on the propeller used. Especially, the Savitsky system, which is widely used for estimating the resistance of planing hull, does not consider the characteristics of these propeller and ship bottom spray rails. In this paper, in order to investigate the difference in resistance characteristics between the propeller and the bottom of the propeller of 6m and 12m class propeller using propeller such as outboard or stern drive, A comparative test was conducted on resistance and attitude posture changes in the Circulating Water Channel of Institute of Medium & Small Shipbuilding. As a result of comparison test, it was confirmed that there is a clear difference in the attitude change due to the presence of the bottom floor spray rail and the change in resistance characteristics due to the installation of the propeller. However, attitude change with the propeller was found to be insignificant.

• 대한조선학회논문집
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• 제46권6호
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• pp.569-577
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• 2009

As the scale factor of model propellers utilized in cavitation test is about 40, it is difficult to find out practical countermeasures against the small area erosions on the blade tip region throughout model erosion tests. In this study, a partial propeller blade model was used for the observation of cavitation pattern for the eroded propeller. A partial propeller blade model was manufactured from 0.7R to tip with expanded profile and with adjustable device of angle of attack. Reynold's number of a partial propeller blade model is 7 times larger than that of a model propeller. Also, anti-singing edge and application of countermeasures to partial propeller blade model which produced in large scale can be more practical than a model propeller. For the observation of cavitation at high Reynold's number, high speed cavitation tunnel was used. To find out the most severe erosive blade position during a revolution, cavitation observation tests were carried out at 5 blade angle positions.

• 한국유체기계학회 논문집
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• 제19권2호
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• pp.11-15
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• 2016

In this study, the generation of the propeller hub vortex was analyzed and a PBCF(Propeller Boss Cap Fins) was designed to control the propeller hub vortex. A RANS(Reynolds-averaged Navier-stokes) approach is employed to predict the hub vortex characteristics. The hub profile is an important factor but only a small increase (1.9%) of efficiency was obtained with the hub profile modification. The propeller hub vortex was eliminated by installing the PBCF and as a result, the propeller efficiency was increased by 5.6%.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
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• pp.578-585
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• 2012

왕복엔진은 효율, 가격 측면의 우수한 장점으로 소형 프로펠러 항공기에서 많이 사용되고 있다. 국내에서는 KC-100, LSA, PAV, UAV등의 개발에 왕복엔진이 주요하게 사용되고 있다. 본 연구에서는 소형항공기 개념설계에 사용할 수 있는 자연 흡기, 터보차저 엔진에 대한 성능 모델을 구축하였다. 왕복엔진 항공기 순항고도에서의 비행조건을 설계점으로 적용하여 프로펠러 성능해석을 통해 최적설계를 하였으며 적합한 프로펠러 성능모델을 구축하였다. 엔진 성능 모델과 프로펠러 성능 모델의 결합을 통하여 소형왕복엔진 항공기 성능해석을 위한 통합 추진 성능 모델을 구축하였다.

• 한국항해학회지
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• 제14권3호
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• pp.15-33
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• 1990

In recent years, propellers with various blade configurations such as highly skewed propellers are often fitted to ships from the viewpoint of reduction of vibration and noise. In the design of such propellers, design charts based on methodical series tests are to be complemented by theoretical calculations for accurate estimation of propeller open-water characteristics. The author intended to develop a method to estimate propeller open-water characteristics based on Quasi -Vortex - Lattice Method originally developed by Lan for solving planar thin wings, The Quasi - Vortex - Lattice Method has the simplicity and flexibility of Vortex - Lattice Method. Its accuracy is comparable to that of the Vortex - Lattice Method. Converged solution can be obtained with a small number of control points and further, leading edge suction force can be calculated directly. In the present paper, a numerical method to estimate propeller open-water characteristics based on the Quasi - Vortex - Lattice Method is reviewed and its application to marine propellers is described in detail. Comparison of propeller open-water characteristics obtained by the present method with experimental data showed good agreement for a wide variety of propellers including highly skewed propellers.

• 한국유체기계학회 논문집
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• 제9권6호
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• pp.29-34
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• 2006

Propeller type pump has been widely used for pumping water in agricultural and manufacturing industry. Since a propeller type pump contains a screw impeller inside a circular casing, the numerical analysis becomes complex. However, the accurate prediction of viscous flow is essential for computing hydrodynamic performances. To analysis the flow and the performance of the propeller type pump, the present work has solved 3D incompressible RANS equations on the multiblocked grid. From the present calculation, small amount of flow separation was shown near hub and the flow was recovered to nearly uniform inflow after one diameter downstream. Torque and thrust coefficient were computed and compared with experiments.

• 신재생에너지
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• 제8권2호
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• pp.44-51
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• 2012

The aim of this paper is to examine the hydraulically optimized camber of a blade. Prior studies have tried to determine the sound method of design on small-hydro turbines. These have appeared to realize a reasonably efficient small-hydro turbine. Nonetheless, specific and accurate design data have not as yet been established for the shape of the runner blade. Hence, this study examines the performance characteristic of an axial propeller turbine with 0~8% camber variations. The results of output power, efficiency, and pressure distribution of the turbine are graphically depicted. The definition of camber refers to the NACA airfoil. The commercial finite element analysis (FEA) packages, ANSYS, and CFX are used in this study. The results revealed the performance characteristics on small-hydro turbine and suggested a highly efficient section shape of the runner.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.260-265
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• 2004

The materials of ship screw propeller are commonly the manganese bronze. The seawater corrosion and cavitation of the screw propeller reduce tire propulsive performance of ship. In screw manufactory, tire corrosion rust of tire screw propeller is removed by a hand grinding. The grinding work makes the dust of the heavy metals from the manganese bronze. The dust makes indoor working environment poor. A friendly-environmental and automatic corrosion removing apparatus was developed for the improvement of screw processing and working environment. The corrosion rust of a screw propeller was remarkably removed by using apparatus. And the screw surface roughness was improved by a blasting effect of the apparatus performance test. Anode polarization curves on jour processing conditions, that is to say, grinding, blasting, wire-brushing, fine sand papering, were confirmed by a potentiostat. Especially, two kinds of medias, alumina and emery, were used in the blasting processing. Then, investigated tire cavitation erosion of specimen. This result proved that tire blasting work has considerably improved the corrosion resistance of a screw propeller.

• 해양환경안전학회지
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• 제22권1호
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• pp.123-128
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• 2016

프로펠러 표면의 생물 부착이 프로펠러 성능에 상당한 영향을 미치지만 프로펠러 표면 거칠기와 관련된 연구는 상대적으로 선체 표면에 비하여 많지 않다. 본 연구에서는 Schultz(2007)가 발표한 Granville's similarity-law scaling 절차에 기초하여 실선 7 m 크기의 탱커 프로펠러에 표면 부착물 상태가 서로 다른 3가지 경우를 고려하여 프로펠러 단독 효율의 감소의 변화를 Lifting surface code를 사용하여 수치적 계산을 수행하여 효율을 비교하였다. 본 논문에서의 결과는 표면 거칠기가 큰 석회질 부착물($k_s=0.001$)은 선박 설계 속도(J=0.5)에서 최대 15 %의 프로펠러 효율 감소를 보였음을 확인하였으며 이는 선박 운항 시 생물 부착에 의한 효율 감소에 대한 평가가 고려되어야 한다는 점을 나타내고 있다.