Blade materials used for the geothermal steam turbines are required both corrosion-resistance and erosion-resistance. Thermal coating is one of the effective measures to improve the corrosion-resistance as well as erosion-resistance of the applied material. In this study, six kinds of coating materials were selected and compared by hardness tests, blasting erosion tests, corrosion tests, stress corrosion cracking tests and corrosion fatigue tests. As a result, coating material WC-10Co4Cr by HVOF process showed the most excellent characteristics in regard to both corrosion-resistance and erosion-resistance, and was judged as the most promising candidate applicable to the geothermal steam turbines.

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Pulsating turbulent flow in conical diffusers having total divergence angles of 12, 16 and 24° were investigated experimentally. Distributions of the pressure and axial velocity and the power loss were obtained for the pulsating flows at the Womersley numbers α of 10 to 40, the mean Reynolds numbers of Re_ta = 15, 000∼30, 000 and the oscillatory Reynolds number of Re_os = 10, 000. The power loss of the pulsating flow in the diffusers is larger than that of the steady flow and is highly dependent on the flow rate ratio. A discussion, furthermore, is given for the influences of the divergence angle and the Womersley number on the time-dependent profiles of the phase-averaged velocity and the turbulence intensity.

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The effect of the shape of intake in a vertical pump on the pump performance is investigated experimentally. The velocity around the intake of the pump is measured by using LDV (Laser Doppler Velocimetry) and the flow field is visualized when the pump is operated at the specified capacity. We investigate the relation between the velocity distribution around the intake and the pump performance. It is found that an appearance of a retard region, which develops due to a flow separation at the edge of intake, reduces the pump performance. If the intake has an enough extent, the retarded region is suppressed because the flow separation does not develop. Hence, we determined the minimum expansion rate in the shape of the intake where the pump performance is not affected significantly.

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