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November, 1909 power and the overall efficiency of the in- stallation would be sufficiently improved to result in a reduction of over 35 per cent in the coal consumption. It is unofficially reported that the consumption of these vessels is about 4,700 tons per voyage. Reckoning the cost of the coal at $3.25 per ton, the saving in coal alone would be $5,300 per voyage, to say nothing of the smaller cost for wages and sustenance for the lesser number of stokers that would be required. The increased car- go capacity resulting not only from a reduction of over 1,600 tons in the coal required to be carried on each voyage, but also from the greatly re- duced weight of the equipment, and the space necessary for 'it, is an asset the value of which it is difficult to over-estimate. If greater speed would be regarded as more attractive than the possible economies mentioned above, it is easy to see that with the same boiler capa- city as is now installed in these ships, the better economy of the high speed turbine would make it practicable to use much more powerful propelling ma- chinery without increasing the amount of coal consumed. The additional pow- er in the turbines, together with the greater propeller efficiency that is pos- sible, would easily give the increased speed that would insure: the disembark- "ing of trans-Atlantic passengers on the fifth day with certainty and regularity, instead of only on occasions when all of the conditions are unusually favor- able. The Mauretania and Lusitania have two high pressure and two low pressure coal turbines, and two reversing turbines working on four shafts. According to the best information obtainable 'the high pressure turbines have each 128 double rows of blades, and the low pressure turbines 60 double rows each. The total length of thé blading ex- clusive of the relatively small amount in the reversing turbines, is about 115 miles, and the total surface area of the blades is considerably more than three-quarters of an acre, or equal to the sail area of a large ship. Propulsive Power in Three Turbines. By using the reduction gear, the same total propulsive power could be installed in three turbines, There 1s nothing problematical about this state- ment, as turbines developing the requisite power, and of the same general design as would in connection with the reduc- tion gear be suited to marine work, have been operating successfully for a long time, and their power and econ- omy are now matters of authentic rec- ord. Each turbine would have only 51 TAE Marine REVIEW | double rows of blades, a total in the three turbines of 153, or only 25 in ex- cess of the number of rows in one of the high pressure turbines alone in the present installations on board the Cunard flyers. The total length of the blading in the three high speed tur- bines would be less than 6 per. cent -of that in the low speed turbines, Each shaft would be driven by a complete and independent self-contained turbine, and each shaft would have its own reversing turbine so that the entire screw equipment would be avail- able for backing instead of only one- half of it, as is the case in the present arrangement. or ; However much the new system prom- ises for express steamers in the mer- cantile marine, it has vastly more im- portant advantages as applied to naval vessels, The express steamer normally runs at its highest speed, and this is the condition for maximum turbine ef- ficiency. This is especially true in -the case of turbines connected directly to the propeller shaft, for the reason that as outlined before the peripheral speeds and number of rows of blades are at best below the requirements of efficient design, and any dropping below the max- imum working speed accentuates the bad effect of this deficiency. Cruising Speed of Naval Vessels. On the other hand, in the case of a battleship or a cruiser, maximum speed is only an emergency. condition. The normal cruising speed is only about 60 per cent of the maximum speed, and requires perhaps less than 25 per cent of the maximum power. It is at the cruising speed that 'turbine propelled naval vessels have shown to disadvan- tage as compared with vessels pro- -pelled by the best types of reciprocating engines. By reason of the more liberal blading that is possible in a high speed turbine, its economic performance is less sensitive to departures from max- imum rotative speed, than is that of the low speed turbine. as the entire expansion of the steam takes place in a single turbine, the total' power may be distributed con- veniently among three entirely inde- pendent units, driving one central and two wing propellers. The central unit alone will suffice for ordinary cruising speeds, and can be. operated always at somewhere near its most economi- cal conditions of working. In naval service, the ability to start the turbines when cold, and quickly bring them to full speed may often be of the very highest importance. With turbines directly connected to the pro- peller shafts, the lengths and diame- -and Macalpine Furthermore, 443 ters of the rotors and casings are such that in order to prevent serious dis- tortion from unequal heating and ex- pansion, it has been found necessary in practice to bring all of the turbine machinery to the normal working tem- perature before it may safely be set in motion. I have been informed by those having charge of turbine ma- chinery on a large battleship, that the preliminary warming often requires some hours. -- Give a Sturdier Construction. In the double flow turbine which it is proposed to use with the Melville gearing, the smaller dimensions 'consequent on the higher speeds give a sturdier construction in which the tendency to distortion is re- duced to a negligible minimum; and an elastic self-adjusting mounting for the stationary blades, easily removable for examination without unseating the rotor, compensates for any inequality in the «. expansion . of: the. retor © ane the casing, and effectually prevents the stripping of the blades even if there should be actual contact be- tween the stationary blades and the body of the rotor, or between the moy- ing blades and the casing. With this construction, steam, even though it car- ries large quantities of water of con- densation with it, may be admitted to cold turbines, and full speed obtained in less than a minute, The United States government has lately awarded contracts for two new battleships, to be equipped with steam turbines. These battleships are to have a speed of 20% knots, which will require in round numbers 28,000 shaft horsepower. With 55 per cent propeller efficiency the effective propelling power will be about 15,400 horsepower. With the 65 per cent propeller efficiency that is_ easily - possible with the reduction gear and a propeller at a lower speed of reyolu- tion, this same propelling power would require less than 24,000 horsepower 'on the shaft. The average steam consumption guaranteed at full power is about 14% -- lb. per shaft horsepower. With the better steam economy of the high speed turbine, the boiler capacity required would be re- duced fully one third. With the same bunker capacity, the radius of action would be enormously increased, which is an advantage of incalculable value. If the same boiler equipment as is now proposed were maintained, there would still be a saving in weight of over 250 tons, or approximately one- eighth of the total penalty weight of the machinery in each' ship, resulting solely from the substitution of the high speed turbine and reduction gear