A testing plant for water turbines was installed as the first attempt by water turbine makers in Japan in the year 1926 by the Hitachi Engineering Works at their Kameido Works, Tokyo. This paper is the first report of the model tests of the propeller type water turbines made in this testing plant during the last two years. The first aim of the tests was to obtain the typical model, upon which the subsequent tests were to be made to know the effect of each of the factors affecting the turbine characteristics separately, for example, the effect of the profile, length, number and the inclination of the blades, the height of the guide vanes, the diameter of the runner hub, etc. After 14 model tests, the following one was chosen as the typical, i.e. the one having 4 blades with a special aerfoil, showing 84.5 % efficiency, including the mechanical losses, at the specific speed of 150 in English units. The hydraulic efficiency of the model would be higher by 1 to 3 %, if the mechanical losses were measured and eliminated ; the estimated efficiency of an actual runner of 9.5 ft. in diameter, which is five times greater than the model in the linear scale, is 91.1 %, calculating by the Moody's approximate formula.
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