DRY STEAM FOR ENGINES

Hawke's Bay Herald-Tribune, Issue 190, 28 August 1937, Page 17

DRY STEAM FOR ENGINES

An important development in the production of a more efficient and ecouomical steam engine for ships is claimed by the North Eastern Marine Engineering Company. It is also claimed that it completes the line of development started by James Watt, about 150 years ago. This consisted in reducing cylinder condensation by means of a separnte condenser. Steam to be uscd efficiently must bo heated to such a degree that it becomes a gas. When it is in this state it is| invisible, as can be seen by what appears to be a clear space at the nozzle of a steam pipe before the steam has absorbed mpisture from the air and becomes visible as white vapour. The main feature of the new development is that steam while expanding in the cylinders is never allowed to get wet. Practieally complete cylinder dryness, which is essential for cylinder efficieney, is insured by reheating the steam during its passage through the engine, so that it cannot acquire moisture. This new engine has been installed iu t\Vo steamers of over 9000 tons gross. One of them, the Lowther

Castle, has recently completed her maiden voyage of some 7000 miles at an average speed of 10£ knots on a coal consumption of 14 tons of north country coal per day. This, it is claimed, shows a fuel eeonomy of 10 to 15 per cent., compared to a corresponding etraight superheated installation. The operation of the steam in this ■xew engine 's as follows:— The superheated steam is generated in special Scotch boilers at 220 pounds pressaure and 775 degrees F. temperature. The steam, before being admitted to the high-pressure cylinder, passes through a reheater in which its temperature is reduced to about 600 degre.es F. The exhaust from this cylinder also passes through the reheater and has its temperature raised by an amount corresponding to the fall of the high-pres-sure steam temperature. The reheated exhaust steam then passes to the medium and low-pressura cylinders, and is fmally exhausted from the latter direet to the condenser. The prineipar effect of the reheating is to reduce the wetness of the steam to a negligible quantity and so to improva the engine 's qffieiency. *