The Steam Turbine
by Sir CHARLES A. PARSONS, K.C.B. Best viewed with window no wider than the above line.
THE STEAM TURBINE In modern times the progress of science has been phenomenally rapid. The old methods of research have given place to new. The almost infinite complexity of things has been recognized and methods, based on a co-ordination of data derived from accurate observation and tabulation of facts, have proved most successful in unravelling the secrets of Nature; and in this connection I cannot but allude to the work at the Cavendish Laboratory and also to that at the Engineering Laboratory in Cambridge, and tot he association of Professor Ewing with the early establishment of records in steam consumption by the turbine. In the practical sphere of enginerring the same systematic research is now followed, and the old rule of thumb methods have been discarded. The discoveries and data made and tabulated by physicists, chemists, and metallurgists, are eagerly sought by the engineer, and as far as possible utilized by him in his designs. In many of the best equipped works, also, a large amount of experimental research, directly bearing on the business, is carried on by the staff. The subject of our lecture today is the Steam Turbine, and it may be interesting to mention that the work was initially commenced because calculation showed that, from the known data, a successful steam turbine ought to be capable of construction. The practical development of this engine was thus commenced chiefly on the basis of the data of physicists, and as giving some idea of the work involved in the investigation of the problem of marine propulsion by turbines, I may say that about 24,000 £ was spent before an order was received. Had the system been a failure or unsatisfactory, nearly the whole of this sum would have been lost. Further, in order to prove the advantage of mechanical gearing of turbines in mercantile and war vessels about 20,000 £ has been recently expended, and considerable financial risks have been undertaken in relation to the first contracts. With these preliminary remarks I now come to the subject of our lecture. The first turbine of which there is any record was made by Hero of Alexandria, 2,000 years ago, and it is probably obvious to most persons that some power can be obtained from a jet of steam either by the reaction of the jet itself, like a rocket or by its impact on some kind of paddle wheel. About the year 1837 several reaction steam wheels were made by Avery at Syracuse, New York, and by Wilson at Greenock, for driving circular saws and cotton gins. Fig. 3 shows the rotor of Avery's machine: steam is introduced into it through a hollow shaft, and, by the reaction of the jets at the extremities, causes rotation. The rotor was 5 feet across, and the speed 880 feet per second. These wheels were inefficient, and it is not so obvious that an http://www.history.rochester.edu/steam/parsons/part1.html[1/27/2011 5:59:14 PM]
The Steam Turbine, Part I
economical engine could be made on this principle. In the year 1888 Dr de Laval of Stockholm undertook the problem with a considerable mearsure of success. He caused the steam to issue from a trumpet-shaped jet, so that the energy of expansion might be utilized in giving velocity to the steam. Recent experiments have shown that in such jets about 80 per cent of the whole of the available energy in the steam is converted into kinetic energy of velocity in a straight line, the velocity attained into a vacuum being about 4,000 feet per second. Dr de Laval caused the steam to impinge on a paddle wheel made of the strongest steel, which revolved at the highest speed consistent with safety, or about half the velocity of the modern rifle bullet, for the centrifugal forces are enormous. Unfortunately, materials are not strong enough for the purpose, and the permissible speed of the wheel can only reach about two-thirds fo that necessary...