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WA Re oN Ok R E. Vet 2 31 needing but little care in working, and capable of running for a long time with but little wear and tear, which, although in- evitable, can yet be reduced to a very small amount. The loss of steam is entirely confined to the clearance allowed around the shaft. Moreover, the live rings are so constructed as to be very light, and this is of advantage in reducing the gyro- scopic effect which comes into play when the vessel pitches. Fig. 1 shows a longitudinal section of the Rateau turbine. It is taken from the one installed on Messrs. Yarrow's boat. The figure only shows two rings and one diaphragm, as all the others are similar. In this turbine there are 15 moving rings. It has been said that with this system, supposing one could reduce the loss of steam to a minimum, it would, on the other hand, greatly decrease the efficiency by the friction between the rings and the steam contained in the chambers in which the rings rotate. As a matter of fact, however, the friction in our engines of 1,000 to 2,000 H. P. amounts to only 2 or 3 per cent of the maximum power--an insignificant proportion --whereas in turbines without diaphragms, the loss by the escape of steam reaches 10, 15, and even 20 per cent of the maximum horse power, directly the clearances increase at all. All the trial results so far obtained show that our system of turbine is extremely economical in steam consumption. Here are a few of the principal results obtained: Turbines of the Torpedo Boat No. 243.--These were the first multicellular turbines which have been constructed from our designs by Messrs, .Sautter-Harlé & Co. in Paris. These turbines were designed some five years ago, and several im- provements have been since effected which considerably di- minish the consumption of steam. A turbine exactly similar to the one installed in torpedo boat No. 243 was tried under the direction of the French ad- miralty engineers in the workshops of Messrs. Sautter-Harle & Co. This engine was coupled to a three-phase alternator, so as to measure exactly the effective horse power of the tur- bine. The electric current generated was taken up by liquid resistances. As the losses of energy in the alternator had been measured, it was possible to calculate the net effective horse- power of the turbine, and consequently its efficiency. By the "efficiency" of the turbine is meant the ratio of the effective power which it develops on the shaft to that which the steam consumed is capable of giving, assuming that there is no loss between the pressure at admission and the pressure at ex- haust into the condenser. This experiment gave a result high- er by I per cent than had been originally estimated, viz., 54 per cent instead of 53 per cent, and the results are shown in Fig. 3. The curves there drawn are obtained by reducing the speed of rotation to the uniform speed of 1,700 revolutions per minute, and the condenser vacuum to 26 in. of mercury. It will be seen that at full power, with a steam pressure at ad- mission to the turbine of 145 lbs. per square inch, the con- sumption per effective horse power on the shaft is 15.2 lbs. At the normal speed of 1,800 revolutions per minute, for which the engine was designed, the efficiency is rather higher, and the steam consumption rather lower. We can now make en- gines of this power with 60 per cent or even 70 per cent effi- ciency, according to the speed of rotation which can be used for the turbines, depending on the use for which they are designed. Turbine of the Yarrow boat.--The turbine for the Yarrow boat has not yet been tested at the works up to its full speed, but from previous calculations it is estimated that the efficiency should be 61 per cent at a maximum of 2,000 H. P., with z normal speed of 1,500 to 1,600 revolutions per minute. The loss due to friction between the rings and the steam is only 41 H. P., or 2 per cent. With 170 lbs. per square inch pres- sure, and a vacuum of 27 in., the consumption of steam of this engine is ---- = 13.4 lbs. per effective horse power hour, which corresponds to 11.7 Ibs. per indicated horse power for a reciprocating engine having 12 per cent loss due to internal friction, Other turbines----Other turbines driving alternators, contin- uous current dynamos, centrifugal pumps or fans, and con- structed by Messrs. Sautter-Harlé, have been carefully tested, and, among the results obtained, I would call attention to the following: An engine of 600 H. P., a 2,400 revolutions per minute, consumes 14.6 lbs. per electrical horse power per hour. The efficiency of the dynamo being 91 per cent, it follows that the consumption of steam for the turbine was 13.3 lbs. per effective horse power hour, or 11.3 per indicated horse power hour, as- suming the efficiency of the reciprocating engine to be 85 per cent, the steam pressure at admission being 142 lbs. and the condenser vacuum 26 in. An engine of 350 H. P. driving an alternator at 3,000 revolu- tions per minute showed a consumption of 26.2 lbs. per kilo- watt generated by the alternator (including exciter), steam pressure at admission being 152 lbs., and the con- denser vacuum only 24 in. The efficiency of the alternator be- ing 87 per cent, this corresponds to a steam consumption of 14.1 lbs. per indicated horse power hour. It will be seen that this was a case of.a relatively weak snes working with a very poor condenser vacuum. A low-pressure turbine of 350 H. P., installed in a mine at Bruay, gave an efficiency rather higher than the above, the total efficiency of the turbine and dynamo combined reaching 58 per cent, or for the turbine alone 63 per cent. Recent tests have shown that the efficiency of this: engine has remained the same after a year and a half of continuous work, and no appre- ciable increase in total steam consumption for the same amount of energy produced has been observed. A turbine pump of 500 H. P., for raising 950 gallons per minute to a height of over 1,200 ft., and which was recently tested, gave a consumption of 22.5 lbs. per horse power hour in actual water raised, the pressure at admission being go lbs. per square inch, and the condenser vacuum 26 in. The effi- ciency of the pump being 7o per cent, this corresponds to an efficiency of 61 per cent for the turbine. In all the above cases the steam was not superheated. 'It will. be seen from these examples that even for engines of only. 300 to 600 H. P. a working efficiency of over 60 per cent can be obtained, while for engines. of 1,000 H, P. and over, it is certain that upwards of 65 per cent efficiency can be realized, as already stated. Hence it is easy to arrive at the consumption of steam per effective horse power under various circumstances, by using the formula which I have already given. For instance, we could guarantee that for an engine of 5,000 to 6,000 H. P., supplied with steam at 150 lbs., and superheated to 350 deg. centigrade, with 28 in. vacuum, the consumption per effective horse power would not exceed 9.6 Ibs., which corresponds to 8.6 lbs. per horse power hour, as- suming Io per cent to be lost in internal friction. In order to properly understand the value of these figures, it is necessary to compare them with those obtained with re- ciprocating engines. When the expansion of steam in the cylinder has been carried sufficiently far, which occurs at from one-half to two-thirds of full power, the efficiency of powerful reciprocating triple-expansion engines is as much as 62 per cent (this is net efficiency; that is to say, the ratio between the work performed on the shaft and the work that the same amount of steam would give with no loss). But this is not the case when the engines are working at full power, for then, in order not to increase the weights too much, especially on warships, one must increase the admission to the cylinder up to and even beyond 7o per cent. From an investigation made by Mr. Delong, a French admiralty engineer, published in the Transactions of the Association Technique Maritime (1899), the efficiency in work delivered on the pistons of several en-