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ees arine "Turbines The Westinghouse Turbine and Reduction Gear Propelling Machinery for the Collier Neptune Tio the 'introduction | of gears between the turbine and propeller, a number of problems arise which were not met with in the direct arrangement. The use of gears permits the turbine to tun at almost any desired number of revolutions and thus materially re- larger proportion of the ahead power gives in a direct connected installa- tion. This condition for two reasons: First--With the increased speed of the geared turbine, its economy is much higher than that of the direct is rather fortunate FIG, 1--PORT TURBINE LOOKING FORWARD, SHOWING GOVERNOR AND OIL RELAY CYLINDERS duces the size and weight of the tur- bine for any given capacity. With the direct connected arrange- ment, owing to the increase in weight and particularly the length of the turbine, it has been difficult to obtain a sufficiently large proportion of the ahead power in the astern turbine. In many cases where sufficient astern power was available, the small diame- ter of the propeller made this power of little benefit because the thrust in reversing rose to such a point that cavitation occurred and the propeller became ineffective. With the geared installation, how- ever, Owing to the lower speed, the propeller can be made of such ample area that its efficiency, when revers- ing, is very much higher than that of a direct connected one. As as re- sult of this higher propeller efficiency _in the geared unit, a smaller propor- tion of the ahead power gives far better maneuvering qualities than a connected unit. Due to this lower water rate of the ahead turbine, it necessarily follows that the astern turbine (in order to develop a given percentage of power of the ahead on the same weight of steam and same steam conditions) must be designed to give practically as good a water rate as that of the ahead turbine in a direct connected installation. There- fore, to develop the same percentage of the ahead power, the astern turbine in a geared installation must be pro- portionately larger than in the direct connected unit. Second--As the size and the speed of the turbine increases, the power absorbed in running the astern tur- bine idle increases very rapidly, so 'that the greater the proportion of the ahead power it is desired to develop when running astern, the more diffi- cult it becomes to make the ahead turbine as economical as desired. As the power required to drive the astern turbine idle increases with the density of the stream in. which it is rotating, it is obvious that it is more essential to maintaina high vacuumina geared than in a direct connected in- stallation; and the higher the vacuum which can be maintained at all times, the greater the proportion of the ahead power which it is permissible to develop when running astern. Like- wise, if the astern turbine is designed FIG. 2--PORT TURBINE, LOOKING AFT, SHOWING RELAY CYLINDERS GOVERNOR AND OIL