THE MERITS OF THE TURBINE

New Zealand Times, Volume XXVIII, Issue 6027, 11 October 1906, Page 5

THE MERITS OF THE TURBINE

No subject is being more energetically discussed among engineers than the merits of the tui-bino, and-’ opinions conflict a good deal. As is apt to be l the case, the first unadulterated enthusiasm—that, for -instance, felt when the Turbima made its , famous 40-mile an hour dabii rcund the fleet at Spithead—has not been fully warranted by nine or ten years’ experience. The strongest case for the turbine is put by Parsons and his followers. They claim that the piston engine has reached finality, and must be superseded in all vessels over 16 knots sea-speed, ‘ which means in about onefilth of the world’s tonnage. Parsons—the Hon. Charles Algernon Parsons, M.A.. D.Sc., F.K.S.—will no doubt fake place among the first rank of inventois, a position for which he was well equipped. both by nature and art. He is the fourth son of that third Earl of Kosse whoso telescope became famous, and was long the largest in the world; and ho graduate as 11th \)7rangier at Cambridge in 1876. A judicious: summing up of the turbine question has been done by H. G. Sadler. Reliability, economy, and adaptability to changing conditions are the general points to bo kept in mind as regards a marine engine. The turbine does not suffer from comparison with re. ciprocating engines as to the first two, but it falls away at present a good deal in the 1 last respect—adaptability. There is a conflict of'interest between the, efficiency of the turbine and the efficiency of the screw. The turbine must be driving at a high rate of revolution to bo worth while; but, on the other hand, when it passes a certain limit of speed the efficiency of the ©crow falls off rapidly; and not only so, but smaller screws must be employed. Minor advantages of tho turbine are that it gains in economy of weight and space, and. its forces are so well balanced that there is little vibration. Of course, the invention is ; still in its infancy, and there are a number of rival systems. : These fail generally under two types distinguished by the pressure existing in the clearance spaces between the guide and the rotating blades. If this pressure is greater than that of the steam as it leaves the rotating blades, tho turbine is classed as "reaction typo”. if equal, as "impulse type." Some systems demand a high speed of revolution, and this has to be broken down by gearing. By reason of its greater simplicity, the turbine is lees liable to breakage than the reciprocating engine, though where the steam velocity is high there is considerable erosion of the blades. A fundamental difficulty is that reversing is not possible; for this purpose a special reversing turbine or a reciprocating engine has to be provided. This is a serious drawback, and puts the turbine out of court for vessels which must be frequently. stopped and started." Mr Sadior sums up the case by remarking that so far as reliability; is concerned there seems to be no reason why the turbine should be inferior to the reciprocating engine, while from the point view ofeconomy and speed the turbine has shown itself in many ways superior. At very low speeds, however, the reciprocating engine is superior in economy of steam, but against this the turbine requires lees oil, and rather less engineroom staff. The turbine in its present state is not suitable for all classes of ships. , Where the speed is high it may be used to advantage, but in slow cargo boats, or for those vessels that have to be started and stopped at frequent intervals, the turbine is not suitable. None the less, it can be widely applied, from the small yacht up to the Cunarder, with 70.000 indicated horse-power.