Steam turbines; a practical and theoretical treatise for engineers and students, including a discussion of the gas turbine . allest section of a nozzle is always very nearly .58 ofthe initial pressure (Pi). t Very elaborate curves of the velocities resulting from the adiabatic expansionof dry saturated steam have been prepared and published in some American the several stages in nearly all types of turbines, such curves can be ofvery little use to practical men, because the condition that the steam admitted tothe nozzles is dry and saturated occurs infrequently. That some of
Steam turbines; a practical and theoretical treatise for engineers and students, including a discussion of the gas turbine . allest section of a nozzle is always very nearly .58 ofthe initial pressure (Pi). t Very elaborate curves of the velocities resulting from the adiabatic expansionof dry saturated steam have been prepared and published in some American the several stages in nearly all types of turbines, such curves can be ofvery little use to practical men, because the condition that the steam admitted tothe nozzles is dry and saturated occurs infrequently. That some of the authorsneglected to mark the curves for steam initially dry and saturated deservessevere criticism. The curves, as given, are very misleading, as they are apparentlyintended for general application for all qualities and superheats. NOZZLE DESIGN 47 Initial Pressure, Pa (5 to 50 Lbs.)5 10 15 20 25 30 3-5 40 45 L2 ^ EE EE —; = Tj|t H EH EE n = EE he = EEE _ ll || = n E=E ~ 1 1 8 n JEE ^P H 60 80 ,100 120 140 160 180 200 220 Pressure, PL (50 to 260 L,bs.) Fig. 19. Curves Showing Values of 60 Total Heat (H) 4 Fig. 20. Illustrates the Use of the Entropy-Total Heat Chart for Deter-mining the Available Energy in a Pound of Steam. 48 THE STEAM TURBINE In addition to the values already obtained it is only necessaryto get v0 and vi (the specific volumes of dry saturated steam at thecorresponding pressures P0 and Pi) to determine all the termsin the equation for the expansion ratio as already given, andputting now the subscript 2 for x in equation (8) to express theconditions corresponding to the pressure P2; then f-l&xSxS, (so A0 V2 v0 x0or . 148s w vv .767 w • 1 / A2 = -JX-i* X —:— X -J—L X .0590 = square inches (area3919 .939 at mouth). The author has found as the result of some investigations regarding the design of nozzles that the expansion ratio (—^ J of a properly designed nozzle is very nearly proportional to the
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