• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.10
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• pp.1281-1292
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• 2001

Experiments were done for the comparison of performance and flow characteristics between a two -stage axial flow fan and a counter-rotating axial flow fan. Each stage of the two -stage axial flow fan used fur the present study has an eight bladed rotor and thirteen slater blades. The front and the rear rotor of the counter - rotating axial flow fan have eight blades each and are driven by coaxial counter ro latins shafts through a gearbox located between the rear rotor and the electric motor. Both of the two axial fan configurations have identical rotor blades and the same operating condition fur the one -to-one comparison of the two. Performance curves of the two configurations were obtained and compared by varying the blade pitch angles and axial gaps between the blade rows. The fan characteristic curves were obtained following the Korean Standard Testing Methods for Turbo Fans and Blowers (KS B 6311). The fa n flow characteristics were measured using a five-hole probe by a non-nulling method. The velocity profiles between the hub and tip of the fans were measured and analyzed at the particular operating condition s of peak efficiency, minimum and maximum pressure coefficients. The peak efficiency of the counter-rotating axial fan was improved about 2% respectively, compared with the two stage axial fan. At the minimum pressure coefficient point of the two stage axial fan, the fan inlet flow patterns show that axial velocity highly decreased in the vicinity of the blade tip region. Also, the reverse flow took place at the blade tip.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.192.1-192.1
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• 2010

Micro hydraulic turbines take a growing interest because of its small and simple structure as well as high possibility of applying to micro and small hydropower resources. The differential pressure exiting within the city water pipelines can be used efficiently to generate electricity like the energy generated through gravitational potential energy in dams. In order to reduce water pressure at the inlet of water cleaning centers, pressure reducing valves are used widely. Therefore, pressure energy is wasted. Instead of using the pressure reduction valve, a micro counter-rotating hydraulic turbine can be replaced to get energy caused by the large differential pressure found in the city water pipelines. In this paper, detail studies have been carried out to acquire basic design data of micro counter-rotating hydraulic turbine, output power, head, and efficiency characteristics on various number of runner vane. Moreover, the influences of pressure, tangential and axial velocity distributions on turbine performance are also investigated.

• The KSFM Journal of Fluid Machinery
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• v.18 no.3
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• pp.53-59
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• 2015

Tidal turbine, which is relatively similar to wind turbine in term of operational principle, has become a potential solution for the sustainable development of global energy. This paper introduces author's work on tidal turbine which aims to improve the power efficiency by the adaption of counter-rotating concept. The turbine system is modelled and analyzed using computational simulation commercial code. Compared with other works, the counter-rotating tidal turbine presented here is expected to operate stably with high performance throughout a wide range of tip-speed-ratio. Moreover, the equability of individual performance of each rotor is an advantage.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.7
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• pp.20-28
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• 2002

In this paper, the aerodynamic performance prediction of a 30kW counter-rotating (C/R) wind turbine system has been made by using the momentum theory as well as the two-dimensional quasi-steady strip theory with special care on the wake and the post-stall effects. In order to take into account the wake effects in the performance analysis, the wind tunnel test data obtained for a scaled blade are used. Both the axial and rotational inductions behind the auxiliary rotors are determined through the wake model. In addition, the optimum chord and twist distributions along the blades are obtained from the Glauert's optimum actuator disk model considering the Prandtl's tip loss effect. The performance results of the counter-rotating wind turbine system are compared with those of the conventional single rotor system and demonstrated the effectiveness of the counter-rotating wind turbine system.

• International Journal of Fluid Machinery and Systems
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• v.9 no.2
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• pp.129-136
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• 2016

An experimental investigation was carried out to improve the performance of a counter-rotating type horizontal-axis tidal stream power unit. Front and rear blades were designed separately based on modified blade element momentum (BEM) theory, and their performances at different conditions of blade tip speed ratio were measured in a wind tunnel. Three different groups of blades were designed successively, and the results showed that Group3 possessed the highest power coefficient of 0.44 and was the most satisfactory model. This experiment shows that properly increasing diameter and reducing chord length will benefit the performance of the blade.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.6
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• pp.1590-1597
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• 1994

The aerodynamic analysis of a $6{\times}6$ counter-rotating propfan around a missile-like-body has been completed analytically using a frequency domain panel method. The present method requires Fourier transformation of flow field around the propfan in computing the velocities normal to the propfan lifting surfaces. The aerodynamic performance curve is determined by angle of attack and nonuniform inflow conditions. The inflow conditions result from the variations of missile flight speed, angle of attack, propfan location relative to control surfaces and control surface deflection angle. The two cases of propfan location relative to control surface, front and behind, are analyzed and the aerodynamic results are presented.

• Journal of the Korean Society of Combustion
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• v.21 no.1
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• pp.31-37
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• 2016

Swirler generates the overall swirling flow in the combustion chamber and this swirling flow governs the flame stability and enhances fuel atomization. This paper deals with the flare angle effects on flow streamlines, recirculation zone, Central Toroidal Recirculation Zone(CTRZ) and Corner Recirculation Zone(CRZ) in the model combustion chamber using counter-rotating swirler. 2D PIV system was employed to obtain the velocity components and test condition was obtained using Reynolds Analogy equivalent to air test. We observed transitional flow patterns of flare angle increased. The obtained results show that the flare angle controls the behavior of Recirculation zone, Central Toroidal Recirculation Zone and Corner Recirculation Zone.

• International Journal of Fluid Machinery and Systems
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• v.6 no.4
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• pp.170-176
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• 2013

Counter Rotating Turbine (CRT) is an axial turbine with a nozzle followed by a rotor and another rotor that rotates in the opposite direction of the first one. Axial spacing between blade rows plays major role in its performance. Present work involves computationally studying the performance and flow field of CRT with axial spacing of 10, 30 and 70% for different mass flow rates. The turbine components are modeled for all the three spacing. Velocity, pressure, entropy and Mach number distributions across turbine stage are analyzed. Effect of spacing on losses and performance in case of stage, Rotor1 and Rotor2 are elaborated. Results confirm that an optimum axial spacing between turbine components can be obtained for the improved performance of CRT.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.166.1-166.1
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• 2011

The rotor design is fundamental to the performance and dynamic response of the Counter-rotating marine tidal current turbine. The wind industry has seen significant advancement single rotor blade technology, offering considerable knowledge and making it easy to transfer to tidal stream energy converters. In this paper, 3D flow and performance an alysis on a 100 kW counter-rotating marine current turbine blade was carried out by using the 3-D Navier-Stokes commercial solver(ANSYS CFX-11.0) to provide more efficient design techniques to design engineers. The front and rear rotor diameter is 8m and the rotating speed is 24.72rpm. Hexahedral meshing was generated by ICEM-CFD to achieve better quality of results. The rated power and its approaching stream velocity for design are 100 kW and 2 m/s respectively. The pressure distribution on the blade's suction side tells us that the pressure becomes low at the leading edge of the airfoil as it moves from the hub to the tip.

• Journal of Aerospace System Engineering
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• v.10 no.1
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• pp.1-7
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• 2016

During flight of the aircraft, the vortex merging phenomenon appears under the certain condition between co-rotating vortices which were generated at the wing tip and lifting-surface. And then these merged vortices at both sides show counter-rotating pattern to affect on the downstream of the aircraft. In this paper, the numerical simulations are conducted assuming this phenomenon in two-dimensional co-rotating or counter-rotating vortices pairs. Two-dimensional incompressible Navier-Stokes equations were converted into Vorticity-Streamfunction form and the Galerkin spectral method was adopted. The third order Runge-Kutta method was used for time integration. The effects on the vortex merger and degree of vortex merger were investigated according to time, Reynolds number, and changes in the distance between two vortices.