2o6 



NA TURE 



[Decemher i6, 1909 



existing non-condensing plant can be more tlian doubled 

 by the simple application of an exhaust, steam turbine and 

 condenser. Such installations are now in use all over the 

 country, and from being absolutely a waste product exhaust 

 steam has become a most valuable by-product in many 

 works. In many cases the exhaust, steam is intermittent, 

 such as the exhaust steam from a winding engine of a 

 colliery. Such intervals, if not too long, can be bridged 

 over by a .thermal accumulator. The principle of thermal 

 storage is itself a' comparatively old idea in connection with 

 steam boilers, having been proposed by Druitt Halpin in 

 1891—2, but the best-known form of . accumulator for use 

 in connection with exhaust steam turbines is that of Prof. 

 Rateau, where a tank containing water has the. exhaust 

 steam blown through it so that alternately, the exhaust 

 steam is partly condensed, and the water in the tank boils, 

 and thus the supply given to the turbine is constant. 



In many cases, however, the stops are too long to be 

 bridged over by any form of thermal accumulator, and in 

 such cases what are called " mixed pressure " turbines 

 have been introduced, in which there is a high-pressure 

 part revolving idly when exhaust steam is used, but when 

 the exhaust steam supply fails, by an automatic arrange- 

 ment this high-pressure part is supplied with live steam, 

 and thus the turbine continues to be driven. 



The first applications of the steam turbine to driving 

 machinet-y were in the driving of electrical machinery, and 

 on land this still continues to be the greatest use for steam 

 turbines, and a full account of turbo-alternators and 

 dynamos is given. 



.\n important development during the past few years 

 has been the application of the steam turbine for driving 

 air compressors. .An ordinary steam turbine when driven 

 backwards does not act as an air compressor, but if the 

 blades are suitably shaped it forms a verv efficient one, 

 and this fact has led to a large development in the applica- 

 tion of steam turbines. 



Such turbo-blowing engines are largely used for blast 

 furnaces, the blast pressures required ranging generally 

 from 10 lb. to \b lb. per square inch. 



It may be mentioned that the weight of a turbo-blowing 

 engine complete is 25 tons, and the weight of a recipro- 

 cating engine of the .same power 430 tons, or seventeen 

 times heavier than the turbine. 



For producing pressures higher than 25 lb. per square 

 inch; the design of the blowing engine is usually of the 

 centrifugal type, and consists of a number of centrifugal 

 fans specially constructed to withstand the stresses caused 

 by the high speed of revolution. 



In the third lecture an account is given of the greatest 

 development of the steam turbine, that for marine pro- 

 pulsion. 



The large and increasing amount of horse-power, and 

 the greater size and speed of the modern engines,' tend 

 towards some form which shall be light, capable of perfect 

 balancing, and economical in steam. The marine engine 

 of the piston type does not fulfil these requirements. This 

 led to the well-known Ttirhinia being built, which proved 

 the success of the steam turbine for marine propulsion. 

 After the Turbinia. the Viper and Cobra, torpedo-boat 

 destroyers, followed, but the next great step was the King 

 Edward, built in 1902. The arrangement of the turbines 

 was altered considerably from that of the Turbinia in order 

 to get increased manoeuvring power. Three shafts were 

 still retained, with two screws on the wing shafts and one 

 on the centre shaft, which revolved at rather lower speed ; 

 but, instead of all the three turbines being in series, the 

 steam passed first through the centre high-pressure one, 

 and then was divided between two low-pressure turbines, 

 port and starboard. In the same casing as these low- 

 pressure turbines, and at the exhaust end, the stern turbines 

 were incorporated. This gave much better manoeuvring 

 power than with the arrangement in the Turbinia, as when 

 manoeuvring the high-pressure turbine was cut' out and 

 steam admitted direct to either or both of the low-pressure 

 turbines or to the astern turbines, thus giving as good 

 manoeuvring power as in the case of a twin-screw ship 

 with reciprocating engines. 



The success of the A'ln? Edward, together with that of 

 the Ti'^ei- and Cobra, led the Admiralty to have turbines 

 fitted into one of four third-class cruisers, and the vessel 

 NO. 2094, ^'Oh. 82] 



chosen was. the Amethyst. Extensive trials were . carried 

 out between her and her. sister ship,, the Topaz, with 

 reciprocating engines, each being 350 feet .long and of 3000 

 tons displacement. The result was that at all speeds above 



14 knots the turbine was the more economical, being 



15 per cent, better at 18 knots, 31 per cent, better at 

 205 knots, and 38 per cent, better at 22-1 knots. 



With . cross-Channel boats it has been found that the 

 turbine vessels use 25 per cent, less coal per passenger, and 

 travel 2 knots faster, than those with reciprocating engines, 

 and the Lusitania has been shown by Sir William White 

 to be 16 per cent, more efficient than the great German 

 reciprocating liners. 



The application of the steam turbine to the propulsion 

 of slow-speed ships, that is, ships of below 15 to 18 knots, 

 has up to the present been difficult, owing to the low 

 speed of revolution of the screws making the turbines 

 large and heavy, as well as not economical. This difficulty 

 has now been got over by the use of an arrangement 

 patented by Mr. Parsons some years ago, viz. the com- 

 bination of reciprocating engines and exhaust turbines, 

 similar to what was described before for land work. Here 

 each utilises the part of the e.xpansion for which it is best 

 suited — the reciprocating engine for the high-pressure part 

 of the range and the turbine for the low-pressure where 

 the volume of steam is large. 



It is interesting to note that in the early days of the 

 screw propeller the great difficulty was to make the engines 

 run fast enough for the screw, and spur gearing was 

 adopted in many cases in the first half of the last century. 

 Gearing has been entirely dropped for the last , fifty or 

 sixty years, but now the difficulty in many cases is to 

 make the turbine run slow enough for the screw, and once 

 more gearing is being considered so as to make the turbine 

 adaptable for use in slow-speed steamers, which, after all, 

 constitute by far the greater part of the shipping of the 

 world. 



The combination system described above does this, but 

 gearing a high-speed turbine to a slow-speed screw would 

 also accomplish what is needed. 



Eighty years ago there was nothing but primitive spur 

 gearing, with generally wooden teeth in one member, but 

 now we have steel gears accurately cut by modern 

 machinery, often with helical teeth, and running in oil 

 baths. 



At the present date there are about t2o vessels actually 

 on service fitted with turbines, representing about 1,250,000 

 horse-power, and these comprise practically all the high- 

 speed ships which have been recently built. Some seventy 

 more are under construction, representing another 1,000,000 

 horse-power, or a total of 2,2^0,000 horse-power, and the 

 curve of progress as yet shows no sign of saturation. 



THE OUTLOOK OF SCIENCE.^ 

 p)ROB.'\BLY there never was a lime when the scientific 

 •'- spirit was more active than at the present moment. 

 We see evidence of this on all hands. In the realms of 

 abstract science we have researches dealing with profound 

 questions as to the intimate nature of matter that were 

 not within the sphere of thought only a few years ago. 

 The theories of electrons which are founded on mathe- 

 matical and physical investigation give us a glimpse into 

 worlds of movement of which those before us had no 

 conception, and of stores of energy that may one day be 

 liberated in the service of mankind. That mysterious 

 agency, electricity, is now seen to be probably at the 

 basis of all phenomena, physical, chemical, vital, and a 

 new interpretation is given of many actions going on all 

 around us. The relation of matter to the circumambient 

 aether also engages the speculations of men of science. 



Researches at extremely low temperatures, down near 

 to absolute zero, as carried out by Dewar, are enabling 

 the physicist and chemist to criticise the properties of 

 matter from a new point of view. The microscope, 

 hitherto an instrument used mostly by the biologist, is 

 now employed in the investigation of the molecular struc- 

 ture of metals and other substances, as these are modified 



1 From an address delivered to the associates and studen's of the r.lasgow 

 and We«t of Srotlanl Technical College on October s8 by Prof. Jchn G. 

 McKend ick, F.R.S. 



