• International Journal of Aeronautical and Space Sciences
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• v.16 no.4
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• pp.485-492
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• 2015

Small advance ratio and low Reynolds number of stratospheric propulsion system bring lots of challenges to the design of propellers. Contra-rotating propeller configuration is proposed to improve the propulsion efficiency. In this paper, the feasibility of contra-rotating propeller for stratospheric airship has been assessed and its performance has been investigated by wind tunnel tests. The experimental results indicate, at relatively low Reynolds number, although the advance ratio is fixed, the performance of propellers is different with variation of Reynolds number. Moreover, at the same Reynolds number, the efficiency of contra-rotating propeller achieved appears to be a few percent greater than that for a standard conventional propulsion system. It can be concluded that contra-rotating propellers would be an efficient means to improve the performance of stratospheric airship propulsion system.

• Journal of the Society of Naval Architects of Korea
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• v.50 no.5
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• pp.349-354
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• 2013

The blades of flexible propellers are formed by overlaying and adhering many layers of thin glass-fiber fabric sheets, are compressed and dried in the rigid mold. The current manufacturing process can not avoid the rather irregular deformation of the blades composed of non-isotropic non-uniform fabric structures, and inevitably introduces the different shape-forming errors between blades. In this paper, several flexible model propellers are precisely measured with three-dimensional optical instrument and compared with the original design geometry. The model propellers with the as-measured geometry are evaluated with the lifting-surface-theory-based propeller analysis code. The open-water performance are presented and discussed. The importance of the manufacturing accuracy is addressed to be able to apply the flexible propellers for propulsion of marine vehicles.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.11
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• pp.917-926
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• 2012

The analysis of aerodynamic characteristics for aircraft propellers is studied to develop high efficiency composite propellers. It is to verify the accuracy and reliability of predicting the efficiency characteristics of aircraft propellers by applying nonlinear numerical analysis. The numerical simulation method incorporated the CFD code, which is based on RANS (Reynolds Averaged Navier-Stocks) equation. The study includes a comparative analysis between the numerical simulation results and the wind tunnel test results of the full-scale aircraft propeller. The comparison shows that thrust and power coefficients of the propeller calculated by nonlinear numerical analysis are higher than those based on the results generated from the wind tunnel test. The efficiency of the propeller calculated by numerical analysis matches closely to the efficiency based on the wind tunnel test results. The verification results are analyzed, then, will be used in optimizing the design and manufacture of the subject aircraft propeller studied.

• Bulletin of the Society of Naval Architects of Korea
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• v.22 no.2
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• pp.12-26
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• 1985

This paper describes the experimental method to predict the propeller induced fluctuating pressure on the hull surface. Cavitations of the three model propellers with varying degree of skews, $0^{\circ},\;36^{\circ}\;and\;72^{\circ}$, were observed and the fluctuating pressure induced by the cavitating propellers in the flat plate above these propellers were measured simultaneously at 9 points in the wake field generated by the wire-mesh screens. Another model propeller designed for the dummy model ship was tested in a similar way behind the dummy model ship. The effects of skew variation on the cavitation patterns and fluctuating pressures were illustrated, and the influence of tip-clearances on the fluctuating pressures was also demonstrated. As a result, it is shown that the level of fluctuating pressure and cavity extent could be controlled to some extent by introducing the skews and tip clearances.

• Bulletin of the Society of Naval Architects of Korea
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• v.17 no.3
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• pp.5-17
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• 1980

A basic procedure to design marine propellers by a curved lifting line theory was shown. By adapting discrete singularity method, it became possible to take into account of skew, rake and the contraction of slip stream in the early stage of preliminary design procedure. It is also shown that lifting line theory based on the discrete singularity method converges to a common solution obtained by induction factor method with a relatively small number of discrete elements. Lifting the blade geometry more accurately on the basis of hydrodynamic principles. A number of numerical results from lifting line calculation are presented for the purpose of comparison with the previous method, and with these results two sample designs are carried out, which are wake-adapted optimum and wake-adapted non-optimum propellers.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.207-212
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• 2003

Recently there has been a remarkable increase in the number of high speed and large ships, and the high power involved for propulsion of above ships have brought high pitch ratio and high skew propeller. The recent tendency toward highly skewed propeller has increased the load on propeller blades and the fatigue strength of propeller blades has become the critical point in design of propellers for above ships. In this paper fatigue tests in sea water were carried out on propeller material of Ni-Al bronze. The stress and environmental conditions of the test were selected to be close to those of full size propellers in use. The effect of stress ratio, stress frequency, revolution number of propeller for above ships numbers and so on were discussed.

• Journal of the Society of Naval Architects of Korea
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• v.54 no.6
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• pp.453-460
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• 2017

In order to investigate propulsion efficiency and cavitation characteristics for expanded area ratio variation of the 8800TEU class container propeller, a series of performance tests were conducted at Large Cavitation Tunnel (LCT) and Towing Tank (TT) in KRISO. The cavitation test of the existing propellers (KP1029 & KP1030) was conducted using FRP model ship in LCT. On the basis of LCT test results, it was required to design propeller with better propulsion efficiency and cavitation performance. Two propellers (KP1171 & KP1172) with decreased expanded area ratio were designed on the basis of KP1029 propeller. The new design propellers showed higher efficiency than KP1029 and reasonable cavitation performance. In the future, they will be applied as the standard propeller for the propeller design of the large container ship. Through the performance test and prediction results for the new design propellers, it is thought that high-load propeller with better propulsion efficiency and cavitation performance will be developed constantly.

• Selected Papers of The Society of Naval Architects of Korea
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• v.1 no.1
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• pp.76-90
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• 1993

A new propeller series is developed using the newly developed blade section (KH 18 section) which has better cavitation characteristics and higher lift-drag ratio at wade angle-of-attack range than a conventional section. The radial patch distribution of the new series propellers is variable stance they were designed adaptively to a typical wake distribution. Basic geometric particulars of the series propellers. such as chord length, thickness, skew and rake distributions, are determined on the basis of recent full scale propeller geometric data. The series is developed for propellers having 4 blades, and blade area ratios of 0.3, 0.45, 0.6 and 0.75. Mean pitch ratios are varied as 0.5, 0.6, 0.7, 0.95 and 1.1 for each blade area ratio. The new propeller series consists of 20 propellers and is named as the KD(KRISO-DAEWOO)-propeller series. Propeller open-water tests are performed at the towing tank, and cavitation observation tests and fluctuating pressure tests are carried out at the cavitation tunnel of KRISO. $B_{p}-\delta$ curves, which can be used to select the optimum propeller diameter at the preliminary design stage, are derived from a regression analysis of the propeller open-water test results. The KD-cavitation chart is derived from the cavitation observation test results by choosing the local maximum lift coefficient and the local cavitation number as parameters. The cavity extent predicted by the KD-cavitation chart would be more accurate compared to that by an existing cavitation charts, such as the Burrll's cavitation chart, since the former is derived from the cavitation observation test results in a typical ship's wake, while the lather is derived from the test results in a uniform flow.

• Journal of Aerospace System Engineering
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• v.15 no.3
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• pp.30-44
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• 2021

Experimental investigation of counter-rotating propellers is subject to multiple time and cost constraint because of additional design parameters unlike single propeller. Also, a lot of computing time and resources are required for numerical analysis due to consideration of the interference between the upper and lower propellers. In the present study, numerical simulations were conducted to investigate the hover performance of counter-rotating propellers by using actuator method which is considered to be time-efficient. The accuracy of the present numerical methods was validated by comparing the ANSYS Fluent which is commercial CFD code. The axial spacing and rotational speed were selected as the analysis variables, and the aerodynamic performance was obtained under various conditions. Based on the obtained results, the Figure of Merit (FM) of single propeller and counter-rotating propellers and a prediction factor which enables prediction of counter-rotating propeller performance using a single propeller were derived to evaluate availability of the actuator method.

• Korean Journal of Materials Research
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• v.27 no.8
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• pp.409-415
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• 2017

For enhanced cavitation erosion resistance of vessel propellers, an electroless Ni-P plating method was introduced to form a coating layer with high hardness on the surface of Cu alloy (CAC703C) used as vessel propeller material. An electroless Ni-P plating reaction generated by Fe atoms in the Cu alloy occurred, forming a uniform amorphous layer with P content of ~10 wt%. The amorphous layer transformed to (Ni3P+Ni) two phase structure after heat treatment. Cavitation erosion tests following the ASTM G-32 standard were carried out to relate the microstructural changes by heat treatment and the cavitation erosion resistance in distilled water and 3.5 wt% NaCl solutions. It was possible to obtain excellent cavitation erosion resistance through careful microstructural control of the coating layer, demonstrating that this electroless Ni-P plating process is a viable coating process for the enhancement of the cavitation erosion resistance of vessel propellers.