Screw-propeller engines, paddle-wheel engines, marine-engine indicating, engine testing, marine side-valve gears, marine condensers, ... repairs, auxiliary marine machinery, marine

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1907 Excerpt: ...F., corresponding to 492 F., absolute. About the lowest temperature to which the steam can be lowered in practice is 562 F., absolute. This temperature corresponds to an absolute pressure of 1 pound, which is probably the lowest pressure attainable in a condenser. 14. The increase of power and economy by the use of the condenser may be shown in another manner. Let ABCDEF, Fig. 2, be an indicator diagram from a noncondensing engine, in which MN is the atmospheric line and OX the vacuum line. The back pressure, as shown by the diagram, is OS. The area of the diagram represents, to some scale, the work done per stroke. Now let a condenser be attached to the engine. The back pressure will be lowered to O T, and the line HK, instead of D E, will now be the lower line of the diagram, and A B C H KL will be the new diagram, its area, as before, representing the work done per stroke. Hence, by adding a condenser to the engine, the work per stroke has been increased by an amount represented by the area F E D H K L, the steam consumption remaining the same. Suppose the steam to be cut off at a point P, making the area of the diagram A PG HK L equal to the area of the original diagram A B CD EF. Then, the work per stroke is the same in both engines, but the condensing engine uses the amount of steam per stroke represented by the length A P, while the non-condensing engine uses the amount represented by A B. Either case shows the economy of the condenser. MAINTAINING A VACUUM 15. As air and vapor will accumulate in the condenser, if they are not removed, the vacuum that was formed by the condensation of the exhaust steam will soon be destroyed. Therefore, to maintain this vacuum, the condenser is fitted with a special pump, known as the air pump, by which the air and v...