学 位 論 文 の 要 旨

（様式 6 号） 「課程博士用」

学 位 論 文 の 要 旨

専 攻 名 システム工学 専 攻 氏 名

ふ り が な

ペンポン テイナポブ PHENGPOM TINNAPOB ○

学位論文題

Study on three-dimensional flows in the vicinity of the horizontal axis wind turbine blade 英訳又は和訳 （水平軸風車翼近傍の 3 次元流れに関する研究）

In the present, we are trying to find alternative energy to reduce fossil fuel consumption.

One of the interesting energy sources is the wind power. Wind power can be converted to the electricity without producing greenhouse gases or other pollutants by using wind turbines.

Generally, wind turbines can be divided into two major categories according to the rotor axis arrangement: Horizontal Axis Wind Turbine (HAWT) and Vertical Axis Wind Turbine (VAWT).

The efficiency of a wind turbine is strongly depends on the aerodynamics performance of the turbine blades. There are many ways to increase wind turbine efficiency. The objective of this dissertation focused on a rotor blade shape to improve performance of Horizontal Axis Wind Turbine (HAWT).

In chapter 1, firstly, many kinds of renewable energy and annual growth rates of renewable energy are introduced. The wind power is the most attractive renewable energy in this decade.

The wind power has a highest renewable energy capacity in the year 2014. The wind energy cumulative capacity can roughly estimate of 380 GW from the total renewable energy capacity in the world of 657 GW in the year 2014. And then, historical development of wind energy is also described. Finally, literature survey of Horizontal Axis Wind Turbine (HAWT) and the purpose of this dissertation are discussed.

In chapter 2, the main nomenclatures using for this dissertation are shown.

In chapter 3, the physical principles of wind turbines are described. The design of the horizontal axis wind turbine rotor blade is mostly based on the blade element momentum theory (BEMT). The BEMT was initially developed to treat propeller and helicopter aerodynamics, but it is easily adapted to use with a HAWT rotor blade. The BEMT is a hybrid method that combines the blade element theory with the momentum theory to analyze the aerodynamic performance of a wind turbine. This method is used to outline the governing equations for the aerodynamic design and power prediction of a HAWT rotor. The momentum theory analyses the momentum balance on a rotating annular stream tube passing through a turbine and the blade.

The element theory examines the forces generated by the airfoil lift and drag coefficients at various sections along the blade span. The BEMT provides a series of equations that can be solved iteratively.

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（様式 6 号－続紙）「課程博士用」

AE

氏 名

ふ り が な

A

ペンポン テイナポブ PHENGPOM TINNAPOB

○

Finally, the BEMT provides the predictions of power coefficient, angle of attack, circulation and aerodynamic forces for wind turbine rotor. However, the BEMT is based on only two-dimensional flows (axial and tangential flows). Therefore, the wind turbines always show different performance between design and operation. In fact, the wind turbine at operating condition has a span-wise flow that it is generated by centrifugal force and Coriolis force. Thus, this dissertation will attempt to study the three-dimensional flow characteristics comparing with the BEMT to improve aerodynamic performance of the wind turbine.

In chapter 4, the experimental apparatus and method for this dissertation are described.

The main experimental apparatus, such as the wind tunnel, test wind turbine model, and Laser Doppler Velocimetry (LDV) are presented. The measurements are carried out in a wind tunnel.

To clarify the characteristics of three-dimensional flows in the vicinity of the HAWT blade, the detailed methods of measurement are explained.

Firstly, preliminary experiments are required to check the test wind turbine before starting the LDV measurement. Since, the test wind turbine has a large rotor diameter and the high blockage might be affected by the wake expansion and gives influence on the flow of the span direction. So, the generalized result as a power curve is checked to make sure that the high blockage ratio has not affected to measured results. And then, the blade section displacement is required to check for setting correctly axial position in the LDV measurement point. When the wind turbine operates, the wind turbine blade surface will be transformed a position from a stationary condition due to the fluid force. So, the laser displacement sensor (LDS) is conducted to detect the blade surface displacement between the stationary and operating conditions. The displacement data is applied as an offset value to describe the measurement blade section.

Finally, measured velocities are detected through LDV system. The LDV measurement in this dissertation uses the simultaneously measuring for three-dimensional velocity components.

Two LDV probes are set in both horizontal and vertical directions. The velocity measurements are performed in synchronized mode. The measured velocities by two LDV proves are detected for one particle, so the measuring volume is limited to the point where three pairs of laser beams cross. A very small size of measuring point from combined three measuring volume provided the high spatial resolution and low velocity variance in measuring point.

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（様式 6 号－続紙）「課程博士用」

AE

氏 名

ふ り が な

A

ペンポン テイナポブ PHENGPOM TINNAPOB

○

In chapter 5, the experimental results are discussed. The power coefficient curves of test turbine showed the same trend as typical wind turbine. The maximum power coefficient is 0.43 at the tip speed ratio of λ = 5.2. Measured velocities from the LDV measurement were shown on the blade suction surface as the two-dimensional relative velocity vector and the span-wise velocity contour. The results showed that the two-dimensional relative velocity at inboard radial position r / R = 0.3 indicated higher values than outboard radial position r / R = 0.7 at the leading part. A higher span-wise flow was located in the inner region of the surface boundary layer while the span-wise velocity in the outer region of boundary layer was close to zero. The surface boundary layer thickness increases from leading edge to trailing edge. The boundary layer thickness for a low tip speed ratio always becomes thicker than the optimum tip speed ratio due to local angle of attack. The pressure distribution on the blade section was shown high rotational effects on the inboard as delays transition point and pressure distribution pattern changes. The measured angle of attack at outboard showed good agreement with BEMT prediction. However, the angle of attack at inboard showed difference due to three-dimensional complicated flow. The skin friction on blade section was investigated by surface velocity gradient at radial position r / R

= 0.7 for the optimum tip speed ratio and low tip speed ratio. The results showed that high skin friction coefficient occurred at the leading part for the optimum tip speed ratio. And then, the skin friction distribution was decreased rapidly until near zero, and then the skin friction recovers again when starting turbulent region. The circulation along the blade span was discussed for the optimum and low tip speed ratios. In the case of optimum tip speed ratio. The measured circulation increases with the increase of radial position. The circulation decreases rapidly at the blade tip due to the tip vortex. In the case of low tip speed ratio, the measured circulation at outboard showed low value due to low lift force and stall phenomenon. While, the measured circulation at inboard was shown high circulation due to thick airfoil shape and span-wise flow effect. The blade surface flow trajectory including the span-wise velocity effect is also discussed. The flow trajectory above the chord stations from the leading edge to pitch axis seems not to be affected by the span-wise velocity. However, the flow trajectory was affected significantly above the chord station from pitch axis to trailing edge due to the span-wise velocity.

In chapter 6, the conclusions are summarized for this dissertation.

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