Heat engines; steam, gas, steam turbines and their auxiliaries
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. 1914 Excerpt: ...is increased by the loss of heat through the cylinder wall by conduction. This may be reduced by surrounding the cylinder with steam at boiler pressure. Such an arrangement is called a steam jacket. The effect of the steam jacket is to reduce initial condensation and to increase the re-evaporation. The steam used by the steam jacket is always charged to the engine as though it had been used in the cylinder. Engines with jackets show increased economy, particularly when operated at slow speed. The higher the speed of the engine, the less is the element of time during which the jacket can affect the steam in the cylinder and the less effective the jacket becomes. In cases of slow-speed engines with large ratios of expansion, the use of the jacket will show a saving of from 10 to 20 per cent. 99. Superheating.--Superheating the steam previous to its admission to the engine is used as a means of reducing initial condensation. A sufficient amount of superheat should be given to the steam so that on admission of steam to the cylinder, the cylinder walls take up this superheat instead of condensing the steam. The effect of this is to leave the cylinder walls entirely dry, reducing the amount of heat which would be conducted to the walls, as dry gas is one of the best non-conductors of heat. The experiments of Professor Gutermuth show that with sufficient superheat the economy of a simple non-condensing engine may be made to equal that of a compound condensing engine. 100. Compound Expansion.--By increasing the steam pressure and using a longer range of expansion, the range of temperatures in the cylinder of a steam engine is much increased, thereby increasing the initial condensation. In order to reduce the range of temperatures in the cylinder, it has been found ...