FOR AUXILIARY PURPOSES ON BOARD SHIP. 155 



BLOWERS. 



Apart from generator sets the first serious application in the U. S. Navy of the 

 small turbine was forced-draft sets on torpedo-boat destroyers. The great im- 

 portance of the successful and continual operation of this apparatus, the serious 

 losses that had been sustained by the breaking down of engine-driven fans on trial 

 trips and in service, made the Government and shipbuilders seriously consider the 

 possibilities of some other form of drive that would be more reliable. 



Motor drive was impracticable, and the steam turbine, therefore, presented the 

 only feasible solution provided a machine could be designed giving a reasonable 

 economy with a mechanical design that would insure absolute reliability. 



The next step, namely, economy, was easily demonstrated. A deputation con- 

 sisting of Capt. C. W. Dyson, Rear- Admiral Little, Captain Higgins of the U. S. 

 Navy Department, and representatives of practically all the shipyards visited the 

 works of the Terry Steam Turbine Co. on June 15, 1909, and conducted exhaustive 

 tests on a standard horizontal turbine with the same diameter of wheel that would 

 be used for a vertical turbine of the same power (see Transactions American So- 

 ciety Naval Engineers, Vol. XXI, No. 3, August i, 1909). 



The economy proved satisfactory. The next step was the satisfactory me- 

 chanical design. 



The first design submitted to the Navy Department by the writers for a forced- 

 draft unit was a horizontal turbine, geared to vertical fan shaft, thus permitting 

 the use of standard type of turbine running at high speed with resulting good water 

 rate. However, the Bureau preferred to sacrifice economy for reliability, and re- 

 quested that the design be modified to a direct-connected vertical-shaft unit, thus 

 cutting down the weight and removing possible trouble at the gear. 



This led to the design and adoption of the Terry type BV which for many 

 years has been standard in the U. S. Navy (Plate 73). 



As in all other turbine development work since the very first the trouble 

 was not at all serious as far as the turbine itself was concerned, but in the design 

 of a satisfactory driven member. 



At the time of which we are writing, there was no fan developed for tur- 

 bine speeds to give the required volume (23,000 cubic feet per minute) at the low 

 head necessary of only 5 inches with an open type of fan, the cased type being 

 prohibitive. Also, the screw type of fan could not be considered on account of 

 the noise. Several fan-makers tackled the problem and did not appreciate what 

 they were up against, and it is interesting to note the lack of knowledge that ex- 

 isted in this branch of engineering at that time. The first fan was guaranteed 

 on paper to run at 2,500 revolutions per minute and require a horse-power of 30. 

 After several very disheartening attempts at procuring a reliable fan, a successful 

 fan was finally built, but the speed had by this time been dropped to 1,700 and the 

 horse-power had gone up to 60. 



The efficiency of the first fan was in the neighborhood of 25 per cent. By 



