74 PROGRESS IN TURBINE SHIP PROPULSION. 



This divided flow combination is adaptable to constant speed steamers and will 

 generally give nearly as good performance in steam consumption as the cross com- 

 pound unit previously referred to ; and it has one advantage, that reversing elements 

 may be, placed in both turbines as in the cross compound unit without the need of 

 the labyrinth packing between the ahead and astern exhaust chambers in the high- 

 pressure elements. Although not being compounded one with the other, the revers- 

 ing elements are not as economical as the cross compound unit first described. At 

 full power the steam passes in parallel through three sets of low-pressure blades 

 (if the low-pressure turbine be double flow), thus permitting smaller turbine di- 

 ameters or higher rotative speeds, or both if desired, without reducing the adapt- 

 ability of the turbine to expand to low pressures. This type of installation has the 

 advantage of smaller cross connecting pipes than the straight cross compound. 



There is a further modification of these arrangements known as the "series di- 

 vided flow" as illustrated in Fig. 21, Plate 48, which provides for certain of the 

 turbine elements being operated in parallel for maximum powers and in series for 

 reduced powers. It will be observed from the figure that the blade proportions 

 work out with approximate corrections for either the series or the parallel condi- 

 tion of operation. This combination renders unnecessary the installation of a sepa- 

 rate turbine for use when cruising. The relative performances of these respective 

 types of turbines are exhibited in curves. Fig. 22, Plate 49. 



Some installations have been made where cruising turbines have been employed 

 and attention is called to the arrangement for coupling the cruising turbine, shown in 

 Fig. 23, Plate 50. It has been regarded in the past as desirable that the cruising 

 turbines be arranged so that they may be operated when connected to the main tur- 

 bines at the maximum speed of the main units, the idea having been that should 

 the engineer go up to full power of the vessel and forget to disconnect this cruis- 

 ing turbine, no injury would result therefrom. This meant that when the cruis- 

 ing turbine was in service it had to operate at very low blade speeds and be there- 

 fore quite heavy or the cruising turbine cannot be arranged to be very economical. 

 It is the practice of the Westinghouse Company to design the cruising turbine 

 geared to the main turbine and designed for the speeds at which it is required in 

 service, which would be dangerously high should it not be disconnected at full power. 



The design shown in Fig. 23 provides that should the cruising turbine oper- 

 ate above a predetermined speed, steam will automatically be shut off from it and 

 the clutch automatically opened. The arrangement of this installation provides that 

 the steam maneuvering valve is employed whether the cruising turbine is in opera- 

 tion or not. Means are provided for readily synchronizing the cruising turbine to 

 the speed of the main turbine and throwing the clutch without affecting the speed 

 of the vessel, provided it is running at speeds corresponding to that at which the 

 cruising turbine should be operated. 



An interesting equipment suitable for patrol boats and cutters is shown in Figs. 

 24, 25, and 26, Plates 51 to 53, of which three are in service and some fifty more 

 building. They are exceedingly simple, the turbine comprising a single reentry 



