• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.3
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• pp.373-380
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• 2019

In this paper, a pico hydro turbine employing low head circulation water at fish farms is designed and evaluated. Due to the advantages of simple structures, small head requirements, and low-cost investment, the constant thickness propeller turbine is considered as a feasible solution. The design process based on the free vortex method is presented in full detail, and a 4-blade runner is built using BladeGen. The turbine performance is analyzed both numerically and via experimental methods. Despite slight differences, the results show similar trends between CFD simulations and experiments carried out on factory test-rigs in a wide range of working conditions. At the design flow rate, the turbine achieves the best efficiency of 70 %, generating 3.5 kW power when rotating at 420 rpm. The internal flow field, as well as the turbine's behavior, are investigated through the distribution of blade streamlines, pressure, and velocity around the runner. Moreover, the pressure coefficient on the blade surface at 3 span positions is plotted while the head loss for each simulation domain is calculated and displayed by charts.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.1
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• pp.46-54
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• 2022

A magnetohydrodynamic (MHD) seawater propulsion thruster has been proposed to reduce propeller noise, propeller pitting, and vessel vibration originated from the propeller cavitation. The MHD thruster was also focused to overcome the limitation of propulsion velocity for the special purpose of marine ships. The research trends and key technologies in the worldwide leading countries are reviewed for the development of MHD propulsion thrusters in Korea. A small performance test device was developed firstly with a conventional solenoid magnet of ≤0.6 Tesla and a helical-type cylindrical duct(inner diameter of 5 cm) of thruster. The artificial seawater was fabricated by a salt solution including a conductivity of 5~6 S/m. The measured flow velocity of artificial seawater in the test device was 0.03~0.42 m/s (0.06~0.84 Knot) with a magnetic field strength of 0.6 Tesla and the applied currents of 10~80 A including the change of anode materials. It was found that the flow direction of seawater was reversed by the directional change of applied current in the solenoid magnet.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.23 no.2
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• pp.51-56
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• 2015

This paper presents the procedure of drag prediction for EAV-1, based on a numerical analysis correlated to an in-flight test. EAV-1, developed by Korea Aerospace Research Institute, is a small-sized UAV to test a hydrogen-fuel cell power system. The long-endurance test flight of 4.5 hours provides numerous in-flight data. The thrust and drag of EAV-1 during the flight test are estimated based on the wind-tunnel test results for EAV-1's propeller performance. In addition, the CFD analysis using a commercial Navier-Stokes code is carried out for the full-scale EAV-1. The computational result suggests that the initial CFD analysis substantially under-predicts the in-flight drag in that the discrepancy is up to 27.6%. Therefore, additional investigation for more accurate drag prediction is performed; the effect of propeller slipstream is included in the CFD analysis through "fan disk" modelling. Also, the additional drag from airplane trim and load factor that actually exists during the flight test in a circular path is considered. These supplemental analyses for drag prediction turn out to be effective since the drag discrepancy reduces to 2.3%.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.11
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• pp.1028-1035
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• 2007

this study, forced vibration analysis was performed on the composite main wing structure of a small scale WIG craft which is equipped two-stroke pusher type reciprocating engine. The structural vibration analysis based on the finite element method was performed using a commercial FEM code, MSC/NASTRAN. Excitations for the frequency response analysis were assumed as the H-mode(horizontal mode), the V-mode(vertical mode) and the X-mode(twisted mode) which are typical main vibration modes of engine. And excitations for the transient response analysis were assumed as the L-mode(longitudinal mode) with the oscillating propeller thrust which occurs.

• Journal of Power System Engineering
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• v.11 no.1
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• pp.33-38
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• 2007

Recent, The propeller had high performance according as high performance of small ship. So, We has the development for azimuth thrusters. This Paper has structure improvement of steering support flange in azimuth thrusters. Steering support flange is very important part. because, Steering support flange supports all weight of azimuth thrusters. We has static & dynamic analysis of Steering support flange, and we discover the very safety. So, We has optimum design for the cost reduction. The first method of optimum design, We has the thickness reduce to 30mm from 5mm. Next method of optimum design, We had added stiffener. And we has the structure & dynamic behavior analysis. We had to dynamic behavior analysis. The first, We had to modal analysis. The result of 1st-modal analysis is that original model had to 76.48hz and new model had to 200.9hz. The second, We had to harmonic analysis. The result, We gave the thrust power to steering support flange. and We had to frequency analysis to $0{\sim}500hz$. The result, Deflection ration reduce to 16.64.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.4
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• pp.48-54
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• 1995

A new propeller open water testing device is developed and tested in a tow tank. The devised dynamometer consists of a torque measuring part, a thrust measuring part and a driving motor with an RPM counter. Torque is designed to be measured directly from the torsion of the structure holding the motor by using strain gauges and, consequently, conventional slip ring is removed. Also, in order to make the device fit in relatively small model ships, the weight and the size of the whole integrated structure are reduced in various ways. The developed tester is proved to be easily utilized in small circulating water channel experiments and is believed to have provided us with essential information for future design of various types of conventional or object oriented force measuring device.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.1
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• pp.10-16
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• 2013

This paper discussed a procedure for noise certification of Aircraft and predicting the full scale over-flight noise of propeller from acoustic wind tunnel measurement of small scale propeller. Noise Certification Procedures is established from International Civil Aviation Organization(ICAO). The data manipulations are then discussed in extrapolation to simulation flight distance and flight simulation. One of the most important point of flight simulation is adjustments for differences between wind tunnel test conditions and flight test conditions. To simulated the noise level estimation procedure for noise data post-process, simulate procedures from data of the wind tunnel noise measurement and the flight noise measurement by using a 7kg degree UAV. This study confirmed an effectively noise estimation procedures by wind tunnel noise test and flight noise test.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.11
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• pp.1221-1229
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• 2014

This paper proposes an approach for predicting the fatigue life of a propeller shaft of a forklift truck by an accelerated life test method. The accelerated life test method adopted in this study is the calibrated accelerated life test, which is highly effective in the prediction of the lifetime and enables significant reduction of the test time as well as a quantification of reliability in the case of small sample sizes. First, the fatigue test was performed under two high stress levels, and then, it was performed by setting low stress levels in consideration of the available test time and extrapolation. Major reliability parameters such as the lifetime, accelerated power index, and shape parameter were obtained experimentally, and the experimentally predicted lifetime of the propeller shaft was verified through comparison with results of an analysis of load spectrum data under actual operating conditions.

• Composites Research
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• v.34 no.1
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• pp.16-22
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• 2021

Polyurethane foam (PUF) can be manufactured in soft, semi-rigid, and hard forms, so it is used in various fields industrially. Among them, rigid PUF has excellent mechanical properties and low thermal conductivity, and is used as a thermal insulation material for buildings and as a cold insulation material in the natural gas transportation field. In this field, there is a steady demand on higher mechanical strength and lower thermal conductivity. In this study, a rigid PUF was manufactured, and the microstructure and physical properties were studied according to the impeller type (propeller, dispersed turbine) of the agitator. Through FE-SEM and Micro-CT analysis, it was confirmed that the average pore size of the foam manufactured with the dispersed turbine was 21.5% smaller than that of the pore made by the propeller. The compressive strength was improved by 15.4%, and the thermal conductivity decreased by 3.1% in the foam with small pores. This result can be utilized for fabricating PUF composites.

• Proceedings of the KWS Conference
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• v.43
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• pp.213-215
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• 2004

Water jet propulsion system has high efficiency on middle to high speed, and it provides better safety than conventional screw propeller because it has not projected propeller and rudder. So many leisure boat and high-speed ferries use this propulsion system. We developed water-jet propulsion unit for small planning boat, and launched that in the boat, after that we tested water-jet unit in the lake. As a result, we certify heat dissipation at the bearing housing and reverse duct's shape for neutral position are important at the design, and alignment water-jet unit and keel line are important at the launching, and ship's resistance performance and jet's propulsion performance also are needed to consideration.