. Development and electrical distribution of water power . al head, and is generally less 66 DEVELOPMENT AND DISTRIBUTION OF WATER POWER The Pelton or jet impulse wheels are suitable for heads above150 feet. They have the advantages of high efficiency, simplicity,and low cost. Fig. 36 shows the general arrangement of this formof wheel. The water emerges from the nozzle at a velocity equal to 8\/head and strikes against the wheel buckets. These areformed with a double curvature having a rib in the middle as water strikes against the sharp edge of the rib, divides in twoequ
. Development and electrical distribution of water power . al head, and is generally less 66 DEVELOPMENT AND DISTRIBUTION OF WATER POWER The Pelton or jet impulse wheels are suitable for heads above150 feet. They have the advantages of high efficiency, simplicity,and low cost. Fig. 36 shows the general arrangement of this formof wheel. The water emerges from the nozzle at a velocity equal to 8\/head and strikes against the wheel buckets. These areformed with a double curvature having a rib in the middle as water strikes against the sharp edge of the rib, divides in twoequal parts, half going into one side of the bucket and half into theother. The water impinges against the bucket surfaces and atthe same time sustains a change in the direction of its motion, beingdischarged by bounding back practically in the opposite directionto the direction of flow from the nozzle, but slightly to the side sothat the reversed water does not encounter the incoming nozzleflow. The object of this design is to completely reverse the direc-. Fig. 37. tion of flow of the water and have it leave the wheel at practicallyzero velocity, thus abstracting all the kinetic energy from thewater. The peripheral velocity of the wheel is practically one-half the WATER-WHEELS 67 spouting velocity of the water, and the efficiency of this type of wheelis often as high as eighty-five per cent. In a wheel of given size, thepower may be increased by simply increasing the number of nozzles,each nozzle adding a proportional amount of power. This in-crease generally is not to be carried further than five nozzles to anywheel, a certain distance between nozzles being necessary for the
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