ENGINEERING PROGRESS IN THE U. S. NAVY. 65 



heating surface per indicated horse-power for vessels fitted with the new type 

 of engines and with boilers having superheaters, and also for vessels with the 

 older type of engines and no superheat. 



In laying down these curves, the actual generating heating surfaces and 

 superheating surfaces have been retained, and the grates have been increased 

 or decreased in order to have a constant ratio of heating to grate surface of 

 48.5, this being the ratio for the boilers of the Minnesota. At the same 

 time, the air pressures have been corrected inversely as the ratio of the new 

 grates to the actual grates. 



The results obtained are shown as follows : — 



Ctirves of indicated horse-power per square feet of grate surface. 



A — With m.oderate superheat and modern engines. 

 B — No superheat and unimproved engines. 



Curves of square feet of heating surface per indicated horse-power. 



A — Generating and superheating surface per indicated horse-power 

 with modern engines. 



C — Generating surface per indicated horse-power with modern engines 

 and superheat. 



B — Generating surface per indicated horse-power with unimproved 

 engines and no superheat. 



With the advent of the turbine for marine propulsion, if the full benefit 

 of the new machine was to be realized, a high vacuum in the condensers 

 became imperative. In order to obtain such vacuums, the Parsons Com- 

 pany originated the vacuum augmentor, and this addition to the condensing 

 plant is used extensively in the naval service. In some vessels in the service, 

 in place of the ordinary air pump with augmentor, air pumps of the dual type, 

 as manufactured by Weir, have been fitted, while in other vessels both wet 

 and dry-air pumps have been used. 



Of these systems, that with augmentors and also the dual type appear 

 to give the greatest satisfaction in service, and in addition require less weight 

 and space than the wet and dry system. Abroad, a new system, known as 

 the "Kinetic, "has been developed, and all reports received concerning it have 

 been very favorable, but no example of this system yet exists in the American 

 naval service. In conjunction with these improved pump systems has 

 occurred an improvement in the tube spacing and the bafiling of the con- 

 densers in order that a better separation of air from the water of conden- 

 sation will occur in the condensers. 



