• International Journal of Fluid Machinery and Systems
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• v.1 no.1
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• pp.76-85
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• 2008

In order to extract micro hydropower in the very low specific speed range, a Positive Displacement Turbine (PDT) was proposed and steady performance was determined experimentally. However, the suppression of large pressure pulsation is inevitable for practical application of PDT. The objective of the present study is to reveal the mechanism and the characteristics of pressure pulsation in PDT by use of CFD and to suppress the pressure pulsation. Unsteady CFD analysis has revealed that large pressure pulsation is caused by large variation of rotational speed of the following rotor, while the driving rotor, which is output rotor, keeps constant speed. Here is newly proposed a 4-lobe helical type rotor which can reduce the pressure pulsation drastically and the performance prediction of new PDT is determined.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.14 no.4
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• pp.11-16
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• 2006

The wind turbine rotor blade is faced with various aeroelastic problem as rotor blades become bigger and lighter by the use the composite material. The aeroelastic analysis of a wind turbine rotor blade requires its aerodynamic model and structural model. For effective aeroelastic analysis, it is required the simple and effective structural model of the blade. In the present study, we introduce the effective equivalent structural modeling of the blade for aeroelastic analysis. The equivalent beam model of the composite blade based on its 3D finite element model is established. The free vibration analysis shows that the equivalent beam model of the blade is equivalent to its 3D finite element model.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.160-163
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• 2010

We performed three-dimensional CFD analysis to investigate the effect of the nozzle-rotor axial gap of a partial admission supersonic turbine on the stage performance and the flow field. The computations are conducted for five axial gaps using flow analysis program, $FLUENT^{TM}$. The results show that the axial gap between nozzle and rotor give the effect on the mass flow rates of tip leakage and the flow angle at the rotor outlet.

• Journal of Wind Energy
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• v.2 no.1
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• pp.61-67
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• 2011

In the present study, numerical unsteady simulations of the NREL Phase VI wind turbine in downwind operation conditions were conducted to investigate rotor-tower interaction. The calculations were performed using an unstructured mesh, incompressible Reynolds-averaged Navier-Stokes flow solver. To capture the unsteady effects associated with the tower shadow between the rotor blades and the tower, the wind turbine was modelled including the rotor, tower, hub, and nacelle. The present results generally showed good agreements with available experimental data. At the lowest wind speed, the pressure distribution was characterized by a complete collapse of the suction peak on the blade when the blade passes through the tower wake. It was found that unsteady effects play a significant role in the response of the blades.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.5
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• pp.39-45
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• 2006

Structural health monitoring has been conducted by non-destructive evaluation method when a turbine rotor system of an aircraft engine has cracks. Local stiffness of a turbine rotor system is degraded and critical speed is changed due to the presence of cracks in rotor. Critical speed which is affected by location and depth of crack, is obtained using compliance matrix of cracked rotor. The database of the obtained critical speed is used to evaluate structural health monitoring of a rotor system of a gas turbine engine.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1002-1006
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• 2015

In this paper, design and analysis of permanent magnet synchronous generator for ocean thermal energy conversion (OTEC) considering magnetically coupled turbine-rotor system is discussed. In particular, the rotor dynamics considering bearing span and journal shaft diameter is highlighted. The two topologies of permanent magnet synchronous generator with magnetic coupling are employed for comparison of computed rotor dynamics and generating characteristics. The analysis results show that the critical speed of the turbine-rotor system is higher when the rotor is coupled by magnetically coupling. Finally, the experimental results confirmed the validity of the proposed design and analysis scheme and successful development.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.9
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• pp.26-33
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• 2010

A multi-MW wind turbine is a huge mechanical structure, of which the rotor diameter is more or less than 100 m. Rotor blades experience unsymmetric mechanical loads caused by the interaction of incoming wind with the tower and wind shear effect. These mechanical loads are transferred to the entire structure of the wind turbine and are known as the major reasons for shortening the life span of the wind turbine. Therefore, as the size of wind turbine gets bigger, the mitigation of mechanical loads becomes more important issue in wind turbine control system design. In this paper, a concept of an individual pitch control(IPC), which minimizes the mechanical loads of rotor blades, is introduced, and simulation results using IPC are discussed.

• Ocean Systems Engineering
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• v.14 no.2
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• pp.141-156
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• 2024

The turbine system converts the kinetic energy of water flow to electricity by rotating the rotor in a restricted waterway between the seabed and free surface. A turbine system's immersion depth and rotation direction are significantly critical in the turbine's performance along with the shape of the rotor. This study has investigated the hydrodynamic performance of the Savonius hydrokinetic turbine (SHT) according to the immersion depth and rotation direction using computational fluid dynamics (CFD) simulations. The instantaneous torque, torque coefficient, and power coefficients are calculated for the immersion ratios Z/D ranging [0.25, 3.0] and both clockwise (CW) and counterclockwise (CCW) rotations. A flow visualization around the rotor is shown to clarify the correlation between the turbine's performance and the flow field. The CFD simulations show that the CCW rotation produces a higher power at shallow immersion, while the CW rotation performs better at deeper immersion. The immersion ratio should be greater than the minimum of Z/D=1.0 to obtain the maximum power production regardless of the rotation direction.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.413-422
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• 2005

In this paper, numerical results for 3-D supersonic turbine flow have been firstly compared with the experimental results to verify results computed by $Fine^{TM}/Turbo$. It was found that $Fine^{TM}/Turbo$ can accurately predict flow characteristics within supersonic turbine. Next, an grid system for 3D turbine flow was optimized selected through grid independency test. Finally the effect of axial gap between rotor and nozzle and chamfer angle of blade edge on the flow characteristics within 3-D supersonic turbine was analyzed with Frozen Rotor method.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.40.2-40.2
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• 2011

A Counter-rotating wind turbine is one of the new concepts that are proposed to increase the performance of a wind turbine. It has two rotors rotating in the same axis, and it is known that its power coefficient can reach to 0.64 in the ideal case. While the BEMT is widely used to analyze the aerodynamic performance of wind turbines, the analysis of the counter-rotating wind turbine by using it is limited due to the aerodynamic interaction between the two rotors. In this study, the vortex lattice method is used to consider the effect of the front rotor on the rear rotor of the counter-rotating wind turbine and calculate the aerodynamic performance of it. The power and thrust sharing in the two rotors of the counter-rotating wind turbine are predicted and the total power and thrust are compared with that of a single rotor. Moreover, the wake convection and expansion rate is also compared with that of a single rotor.