AMERICAN TURBINE 



518 



construction an extremely large discharge area is ensured, while by 

 making the wheel deep at inlet, 

 the inlet area is corresponding- 



i 



]y increased. The wheel thus 

 becomes of very compact con- 

 struction and is capable of deal- 

 ing with a large volume of 

 water, but has the grave defect 

 that in virtue of this great 

 depth its efficiency at part gate 

 is comparatively low. 



In the turbine illustrated, 

 the wheel diameter is 15 inches 

 and the depth 7-J inches at 

 entrance, while at exit the di- 

 ameter is 18J inches, the over- 

 all depth of the vanes being 

 14J inches. The guide vanes, 

 twenty- seven in number, are- 

 fixed, and give a mean inlet 

 angle of about 26. The wheel 

 vanes, nineteen in number, are 

 flat at entrance, and are in- 

 clined forwards towards the 

 direction of rotation, making 

 an angle of about 110 with 

 the tangent to the inlet 

 circle. 



The vane angle at exit varies 

 from 12 to 20, the minimum 

 value being that affecting the 

 radial outward discharge. As 

 may be readily understood, the 

 difficulty of designing these 

 exit edges so as to give the 

 correct inclination at each ra- 

 dius is almost insuperable, and 

 experiment proves the only 

 safe guide as to the precise curvature to give to the vanes. Governing is 

 performed by means of a cylinder gate set between guide vanes and wheel, 



H.^. L L 



FIG. 245." New American " Turbine. 



