WONDERS OF ENGINEERING.

Northland Age, Volume VI, Issue 4, 13 September 1909, Page 2

WONDERS OF ENGINEERING.

THE ADVANCE OF THE MARINE TURBINE. Great though the success of the marine steam turbine has been, it is still far from perfection. As the President of the Institute of Marine Engineers put the case this year in his opening address, “The steam turbine, especially for marine purposes, is still in its infancy, although it is a very sturdy infant." 1 Like some children when finding I their feet, the turbine runs too fast, j and the efforts of engineers are meanj time being directed towards the disi covery of means to modify its i speed without sacrifice to utility. It !is fairly common knowledge that | hitherto turbo-propulsion has been j restricted to men-of-war, fast pasi senger steamers, and speedy yachts. i The invention has made little or no headway amongst the immense fleet of slower cargo carriers, because, at the speeds which suit their traffic, the turbine offers no economy over reciprocating engines. Several plans are now being tested with a view to overcome this disadvantage. Of these the most advanced, now being tried in several vessels recently launched, is to combine reciprocating engines with turbines in one system. Such a combination is to be placed in the White Star Laurentic. building at Belfast, it is being fitted experimentally in the yacht Emerald, which was five years ago the first turbinedriven craft to cross tho Atlantic ; and it is at work in the Otaki, on her maiden voyage to New Zealand. The last-named has three propellers, of which the central one is coupled to a turbine, whilst the others are each driven by a set of triple expansion engines. The steam is first used in these engines in the ordinary wav, but on leaving the lowpressure cylinders it passes to the turbines, which is thus driven by its final expansion. If this arrangement answers in practice it will do away with the excessive coal consumption which is the chieJ objection to running turbines at slow speeds. Another development—likely, it is said, to be adopted by the Admiralty in a cruiser to be» built shortly—is to abplish any direct connection between turbine and propeller, and. instead, to couple the former to an electric generator whose power would be applied to the latter At first sight this appears to be a retrograde step, because one of the most obvious advantages of turbine propulsion is that the motor and the screw are on a single shaft, and to introduce intermediate mechanism is to destroy this simplicity But, on the other hand, electricity is a much more “elastic" power than that developed by marine steam turbines, ! and, granting, as is claimed, that t here need be no appreciable loss of energy in the transformation thus suggested, electricity could be much more easily adapted than steam to overcome several of the difficulties in the way of the more general adoption of the turbine engine. At present, for example, it is necessary to have a separate turbine for each line of propeller shafting, and, in the majority of cases, separate turbines and propellers for going astern, as the main mechanism cannot be reversed in the way that reciprocating engines are. But with a single turbo-generator—possibly duplicated for safety—developing electricity, the power obtained could be applied to drive any suitable number of shafts in either direction at any rate desired, whilst the prime mover at the same time maintained a constant full-power speed, which is precisely the condition under which steam turbines are found to be most, economical. Another advantage of this system, as it appears in theory, is connected 1 with the propellers themselves, which work worst at the high speeds that, suit turbines best. Thus, when coupled direct, the faster the turbine revolves the less work the screw does. It might, in fact, be driven so quick - ly as to create a vacuum in the water within which its blades would find so little to grip that increase of driving power would actually cause the ship to go slower. This has actually happened, the phenomenon thus exhibited being technically known as cavitation. The laws

governing it are still very obscure, hut its effects would be greatly modified if, through < electricity or otherwise, the number of revolutions of the turbine could be reduced at the propeller. Alternatively, of course, the shape of the propeller might be modified to suit the turbine, but it is rather a curious circumstance that none of the many efforts made to attain this end have yet achieved more than partial success. A fortune awaits the man who invents a fully effective turbine propeller. Many plans have also been suggested for reducing the speed t*o more useful proportions by means of gearing, and even of belting, but so far none of these have solved the problem An ideal marine turbine would be one working on coal or oil gas without the intervention of steam at all. but such an arrangement is still in the region of experiment, although there are said to be models in existence which indicate the idea to be not only possible, but probably successful. Lf it proved so, the invention would, of course revolutionise much besides marine engineering ; a practically effective gas turbine would, for instance, “scrap" every motor-car now on the road. Meantime, it appears not improbable that the evolution of the present internal combustion engine, in conjunction with electricity, tnay eliminate the marine steam turbine altogether. Suction coal gas plants have already replaced steam boilers in H.M S fattier, in a German torpedo craft, on the Highland passenger steamers, and elsewhere. It is also reported that the next big battleship to be built at Devonport is to have gas engines. Picture these as attached to dynamos developing driving power for application to the propellers, and you will have some idea of a change which may ere long make the steam turbine as much a back number as the turbine itself has made the reciprocating engine. —"Weekly Telegraph."