176 STEAM-TURBINES,
per hour, the number of pounds of steam which a perfect engine would require per horse-power hour under the above condi- tions, is 1,980,000 266,076 =7.4 approximately. If an actual engine, operating under the same conditions, uses 13 pounds of steam per delivered horse-power hour, its efficiency is 7.4+13=0.57. The efficiency of any steam engine may be calculated in a similar manner, from results of tests; thus Efficiency= 1,980,000 water ratex available energy in foot pounds per pound of steam per hour. The table given below shows the use which may be made of such calculations in determining the effect upon efficiency produced by varying conditions of operation. Calculating from the water rates given below the variation. of efficiency with load and with superheat is shown in the following table. (Particulars of turbine given below.) 100 Superheat. Saturated Steam. Test No. Test B.H,P. W. K. Effic. 7.8 W.R. No. B.H.P. W.R. Effie.-8.35÷W.R. 2 1 269. 402. 649. 13.3 16.2 .481 14.6 .534 .586 1 766. 13.1 .595 1234 245. 19.4 .430 106. 16.2 .516 650. 14.6 .572 716. 14.7 .568 3 956. 13.5 6 1195, .577 5 1144. 15.7 .532 14.1 .553
Westinghouse-Parsons 400 K.W. Steam Turbine, 3600 R.P.M., with automatic by-pass valve. Work absorbed by water-brake. Tests to determine economy to be gained by use of 100° F. superheat. Steam-pressure in main steam-pipe 150 pounds gage or 165 pounds absolute in both cases below. Vacuum 27 inches in both cases. Bucket speed varying from
