1862 London Exhibition: Catalogue: Class VIII.: George Rennie and Sons
From Graces Guide
1964. RENNIE, GEORGE, and SONS, 6 Holland Street, Blackfriars, and Greenwich.
Marine condensing engine for screw propellers, high and low pressure, with surface condensation.
HIGH AND LOW PRESSURE MARINE CONDENSING ENGINE.
The above is an engraving of a high and low pressure, marine screw steam engine, placed in a vessel of war.
In class 8 is exhibited a working model of the above arrangement.
The advantage of 2 cylinders in direct-acting marine screw engines, is that of working steam expansively, whereby economy of steam and fuel is obtained, depending upon the pressure of steam, and the relative volumes of the high and low pressure cylinders. The engines are fitted with surface condensers, with copper tubes, and improved centrifugal pumps for circulating the water In condensers; these pumps being made on a double curvature principle; of least resistance to the flow of water occasioned by the centrifugal force generated by the angular velocity of the pump.
Engines on the above principle are fitted with boilers in proportion; apparatus for super-heating the steam, and feed-water heaters may be made to consume not more than 2 lbs. of coal per actual or indicated horse-power.