G.— ENGINEERING. 145 



But though so much has been done in the development of prime 

 movers there is perhaps no movement in engineering to-day that is of 

 greater interest, not only to engineers but to the general community, 

 than the attempts that are being made to considerably increase the 

 efficiency of power production from coal and other fuels. The average 

 overall thermodynamic efficiency of the public stations distributing 

 electrical energy in Great Britain for the year ending March 1928 was 

 about 15 per cent. The best station had an efficiency of 21-3 per cent. 

 Recently a power unit has been supplied from England to Chicago which 

 on test gave an efficiency of 34 per cent. — a remarkable figure. Making 

 allowance for boiler losses, efficiencies of from 25 to 35 per cent, ought to 

 be possible, therefore, in the future and if only suitable materials can be 

 developed to meet the onerous conditions of temperature, corrosion and 

 erosion, higher efficiencies than 35 per cent, may be anticipated with steam 

 plant. Still higher thermodynamic efficiencies may be expected, as well 

 as the chemical riches of the coals preserved, if, as a result of research, 

 solid fuel engines or gas turbines can be developed. At the temperature 

 of from 400° F. (205° C.) to 600° F. (315° C.) at which boilers and super- 

 heaters have until recently worked, mild steels have been found suitable. 

 To realise higher efficiencies than at present, much higher temperatures 

 will be required, and at contemplated temperatures of 1000° F. (538° C.) 

 and upwards carbon steels creep at low stresses. Below a certain stress, 

 at a particular temperature, which I have ventured to call ' The Limiting 

 Creep Stress,' the creep ceases or becomes so small that it cannot be 

 observed in, say, a number of days. This ' Limiting Creep Stress ' is 

 evidently the important factor in the problem of high working tem- 

 peratures. Experiments indicate that with alloy steels limiting creep 

 stresses much higher than those obtained from carbon steels may be 

 expected and that alloys of iron, nickel, chromium and with or without 

 other alloyed elements, containing as much as 60 per cent, of nickel and 

 chromium have considerable strength at high temperatures and also 

 resist corrosion and erosion. There is still, however, a very large amount 

 of research to be done in which the laboratory and the workshop must 

 co-operate, as new workshop technique is required before these alloys can 

 be used for specific purposes. 



Research is being undertaken by many manufacturers at great expense 

 and the public finally reap the benefit, but it would appear that in a 

 matter of such vital concern to industry and the community more rapid 

 progress could be made and a much bolder policy pursued if the public 

 organisations and the large power distributing companies and authorities 

 accepted the responsibility of the provision of funds for research. In the 

 Universities much fundamental work can be done if funds are available. 

 The Department of Scientific and Industrial Research has recognised 

 recently the importance of the subject and is assisting industry and the 

 National Physical Laboratory to carry out researches on the physical 

 properties of metals at high temperatures. The metal problem, asso- 

 ciated with the hope of higher efficiencies in heat engines, is also of very 

 great importance in connection with ' low temperature ' carbonisation of 

 coal and other large-scale chemical engineering processes. 



1929 L 



