โ Scribed by Francis Hodgkinson
No coin nor oath required. For personal study only.
Steam pressures and temperatures have increased in steps from 150 lb. per in .2 to a maximum pressure of 1,400 lb. per in .' with corresponding improvements in heat and steam consumptions . Increase in pressure has not presented difficulties . A proportionately higher blading constant is required because of increased heat drop . The maximum steam pressure is limited to parts of the turbine whose physical dimensions are small,, so there has been no difficulty in securing adequate strength of the parts as far as the mere pressure is concerned .
A problem arises, however, when pressures are increased . There is a greater deposition of moisture during expansion unless the amount of superheat is also increased . The higher the turbine efficiency, the greater is the quantity precipitated . If steam is expanded from a higher to a lower pressure by means of a nozzle of 10o per cent. efficiency, the available heat equivalent of work is in the form of kinetic energy . The heat contained in the steam leaving the nozzle is the total heat of the initial steam minus the heat equivalent of the kinetic energy and the expansion is said to be at constant entropy . If the kinetic energy could be absorbed by blades also at too per cent. efficiency, there would be no change in the total heat of the steam in passing the blades . Any losses in the blades however, would be at the expense of available work and would, appear either as increasing the total heat of the steam or as residual velocity leaving the blade, or both .
The expansion in the nozzle within the superheated range
๐ SIMILAR VOLUMES
Sept., I9O5.] ImJ)roz,e2JzeJzg (~Delaa,are Rl'z'er alcd Harbor. r 79 Negotiations have been completed with the owners of property between Vine and Green Streets with a vie~x of carrying the improvement to the northward. This work uow awaits authorization from Councils. The completion of the paving