Thermodynamics of the steam turbine

📕 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. 1911 Excerpt: ...of flow would be constant; but in Fig. 45 the conditions make the clear distance and the velocity of flow constant, and the blade lengths must also be constant. Of the several influences affecting the lengths of blades and guides, the most effective is reducing the exit angle; next comes the reduction of velocity of the steam on account of friction, and lastly the drying and consequent increase of specific volume of the steam. As already explained on page 95 the following relation should exist when the steam passes from the nozzles into the first set of blades: namely, the peripheral distance from one nozzle to the next, measured along the edge of the dividing plate or member, should be equal to the peripheral width of the blade edge multiplied by the number of blades per nozzle. Thus, in the design just computed, that distance is 0.03 X 3.80 = 0.114 as shown on page 135. The proper blade length will then be equal to the radial length of the nozzle at exit. This relation comes from the fact that the velocity of flow from the nozzle is also the velocity of flow into the blades; this is true in any case whether or not the exit angles are reduced and whether or not account is taken of friction. The velocity of flow being the same the clear space, measured on the periphery, for a nozzle must be equal to the sum of the clear spaces between the corresponding number of blades. The extended discussion of the relations of clear spaces and blank spaces is given, so that the allowance for friction may be the better understood. Having the length of the first set of blades at entrance, the other lengths of blades and guides may be found by making them directly proportional to the specific volumes, and inversely proportional to the velocities and the net distances; the v...