Steam Turbines Their Design And Construction PDF Download

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1913 edition. Excerpt: ...to the extent of the clearance allowed at the thrust block, which in the case of electriclight units is from 2 to 5 mils. Given the clearance the amount of leakage past the dummy can be estimated as follows: --Referring to Fig. 70, the steam issues from between the first pair of rings with a considerable velocity and kinetic energy. The whole of this is destroyed by internal friction before the steam reaches the second pair of rings, which it does at a reduced pressure and augmented volume. Between these it again expands, acquiring kinetic energy, which is again destroyed before the third pair of rings is reached. This process being repeated at each pair, it will be seen that almost the whole of the available energy of the steam is destroyed by internal friction, and that it issues from between the last pair of rings with a velocity much less than that due to its complete expansion. Subject to certain limitations, detailed below, the discharge through such a packing can be calculated by the formula where w denotes the weight discharged in pounds per second, f l the area available for flow in square feet, pt the initial absolute pressure in pounds per square inch, and Vl the initial specific volume of the steam, whilst N denotes the number of points at which the steam is wire-drawn, and x = where p denotes the absolute pressure Pt on final discharge from the last ring of the packing. The formula can be established as follows: --Let the total energy available in 1 lb. of steam expanding between the initial and final pressures be U heat units. At each point of wire-drawing a certain quantity of energy must be supplied to each pound of steam to create a velocity of flow; let this be denoted by qn heat units, which, as the steam increases..