Measurement and unsteady RANS simulations are performed using a time-accurate and high-resolution flow solver to clarify unsteady flow field inside a single-stage axial turbine. The final goal of this study is to reveal how and to what extent unsteady aerodynamic interaction inside the turbine stage affects the turbine stage efficiency, and the focus in this paper mainly deals with the effect of stator-rotor axial gap. A simple but realistic computational model is constructed, for example the blade-count ratio used in the numerical simulations is almost the same as that of the real turbine concerned. The flow field is also measured using a five-hole Pitot probe placed downstream of the stator vanes as well as the rotor blades. Detailed comparisons between the experimental data and numerical data are then made to elucidate the effect of the axial gap on the stage performance. It follows that the interaction of stator wake or stator passage vortex with rotor secondary flow is one of the key flow events that control the stage aerodynamic performance.

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For Vertical Axis Lift-type Wind Turbine, in general, it is difficult to evaluate its performance through the scale-model wind tunnel tests, because of the scale effect relating to Reynolds number. However, it is beneficial to figure out the critical value of Reynolds number or minimum size of the wind turbine, when designing this type of micro wind turbine. Therefore, in this study, the performance tests of several scale-models of Vertical Axis Lift-type Wind turbine were investigated with wind tunnel test. The Range of Reynolds number was from 1.5X10⁴ to 2.3X10⁵ which include field-test machine Reynolds number. The results showed that the Reynolds number effect depends on the typical length of blade chord rather than the typical velocity of inlet velocity. In addition, in the range of our investigations, there was a transition point of the Reynolds number where the dominant driving force of wind turbine changed from Drag to Lift.

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As a solution to the energy problem and the environmental problem, wind energy has attracted attentions. In wind farm, wind turbines installed downwind sometimes operate in the wake generated by wind turbines installed upwind. It brings about power output decrement and load fluctuation of wind turbine, directly concerning failure and fatigue damage of the wind turbine. In this study, the observation of wind field in the wake generated by wind turbine in field was performed. The wind speed in wake was observed by using ultrasonic anemometers installed vertically on a meteorological mast. The present paper shows the results about wind speed recovery and wind direction change in the wake. With high turbulence flow, the wind speed in the wake recovers in short distance. It is because that high turbulence stimulates mixing at boundary of wake.

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The spiral water turbine (screw-type turbine, spiral water mill) has a runner whose shape is same as that of Archimedes pump. As this turbine can run on the very low head situation, and it can be very easily set to open water channels, it is suitable to for the very small hydraulic power generating. In this study, the internal flow and its relation to the generated power is analyzed both by model experiment and by CFD. When the whole turbine sinks, the power can be estimated by angular momentum formula. On the other hand, when only a part of the turbine sinks, the internal flow changes largely, and the turbine works as the displacement type of turbine. In both cases, the axial flow velocity is almost same as the axial moving speed of the spiral blade.

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The fundamental characteristics of rotordynamic fluid force moment on the backshroud of a Francis turbine runner in precession motion were studied by model tests and the computations based on a bulk flow model. The backshroud of the runner was modeled by a disk set close to a casing with a small radial clearance at outer periphery. An inward leakage flow was produced by an external pump in the model test. The effects of the leakage flow rate, the pre-swirl velocity at the inlet of the radial clearance, and the axial clearance between the backshroud and casing on the fluid force moment were examined. It was found that the fluid force moment encourages the precession motion at small forward precession angular velocity ratios and the region encouraging the precession motion is affected by the pre-swirl velocity. Through the comparisons of the fluid force moment, unsteady pressure and velocity distributions in the clearance under the precession motions with and without the rotation of the disk, it was found that the normal moment generated by the precession motion without the rotation of the disk did not have the effect of encouraging the precession motion. The swirl flow due to the rotation of the disk was found to be responsible for encouragement of the precession motion.

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In order to clarify the inlet flow field of a semi-open axial fan with bellmouth at low flow-rate region, the experimental investigation was carried out using hot-wire anemometer. The axial and tangential velocity component including the radial velocity component were measured using a single I-type hot-wire probe. The data were processed using a phase-locked averaging technique. Those were also processed using a FFT analyzing. As a result, it was confirmed that there was a radial inflow through the blade tip into the blade passage at non-stall flow-rate condition. However, its radial inflow disappeared near stall flow-rate condition because of strongly tangential flow covering with the blade tip. It was also found that the flow pattern similar to rotating stall existed at its flow-rate condition by means of the results of FFT analyzing.

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