In a trial with a compound engine, with 130 lb. absolute pressure, the missing quantity at cut-off rose from 11.7 per cent. at 405 revolutions to 29.66 per cent. at 130 revolutions, the consumption of feed water increasing from 20.35 lb. to 23.67 lb. This saving of 14 per cent. was due solely to increase of speed. Similar trials had been made with a simple engine. In one simple trial at slow speed the missing quantity rose to 44.5 per cent. of the whole feed water. ------------------------------+-----+------------+-------------+------+-------------+-------------+------ Intended mean | | | | | | | admission pressure Lb.| 40 | 90 | 110 | 130 | 150 | 160 | 170 ------------------------------+-----+------+-----+------+------+------+------+------+------+------+------ Simple, Compound, or Triple.| S. | S. | C. | S. | C. | C. | C. | T. | C. | T. | T. Actual mean | | | | | | | | | | | admission pressure Lb.|40.88| 92.65|87.54|106.3 |109.3 |130.6 |149.9 |151.9 |158.5 |158.1 |172.5 Percentage ratio of actual | | | | | | | | | | | mean pressure, referred to | | | | | | | | | | | low pressure piston, to | | | | | | | | | | | theoretical mean pressure |98.2 |100 |91.3 |100.7 | 94.8 | 94.2 | 94.6 | 84.54| 95.9 | 85.3 | 85.2 Indicated horse power |16.51| 31.61|28.14| 33.5 | 33 | 36.31| 38.59| 35.69| 39.55| 35.56| 38.45 ------------------------------+-----+------+-----+------+------+------+------+------+------+------+------ Feed water actually used per | | | | | | | | | | | indicated H.P.H.-- | | | | | | | | | | | Simple Lb.|42.76| 26.89| ... | 26 | ... | ... | ... | ... | ... | ... | ... Compound Lb.| ... | ... |34.16| ... | 21.37| 20.35| 19.45| ... | 19.19| ... | ... Triple Lb.| ... | ... | ... | ... | ... | ... | ... | 19.68| ... | 19.19| 18.45 Steam required theoretically | | | | | | | | | | | per 1 H.P.H. Lb.|34.67| 19.24|19.86| 17.9 | 17.65| 16.25| 15.23| 15.16| 14.87| 14.9 | 14.36 Percentage efficiency |81.1 | 71.5 |82.2 | 68.8 | 82.5 | 80 | 78.3 | 77 | 77.4 | 77.6 | 77.8 ------------------------------+-----+------+-----+------+------+------+------+------+------+------+------ Percentage of feed water | | | | | | | | | | | missing at cut off in | | | | | | | | | | | high pressure cylinder | ... | ... | ...