From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
The theoretical power increase from higher compression ratios in engines.
| Identifier | ExFiles\Box 43\1\ Scan094 | |
| Date | 1st August 1925 | |
| H.R. 493a (50s) (D.B. 175 25-9-24) J.H.D. EXPERIMENTAL REPORT. -1- Expl. No. REF: Hs{Lord Ernest Hives - Chair}/AR/LG28. 8.25. NOTES ON THEORETICAL INCREASE IN POWER FOR GIVEN INCREASE IN COMPRESSION RATIO. The theoretical increase in power and B.M.E.P. due to increased compression ratio can be obtained from the usual air cycle efficiency formula using Tizard & Pye's Index of .296. Curves lX. and X. give the theoretical and actual power and B.M.E.P. curves for compression ratios of 6.09 to 1 and 6.28 to 1, the theoretical curves being calculated from those obtained with compression ratio 5.27 to 1 (Curve lll) For purposes of comparison, B.M.E.P. curves of the Condor lV. engine are included. These have been reduced from a compression ratio of 6.5 to 1 to 6.09 to 1 and 6.28 to 1 respectively, and allowance has also been made for the difference in size of the Eagle and Condor engine cylinders. This allowance, according to Ricardo's figures, gives a further reduction of 3.1% (No allowance for difference in cyl. sizes has been made in the Condor lV. B.M.E.P. curve given on Curve lV.) Note :- (1) Curve lX. Compression ration 6.09 to 1. (a) Eagle lX. Carburetters. The actual power curve is about 6 HP. below the theoretical up to 2100 r.p.m., after which the deficiency increases. (b) Eagle Vlll. Carburetters. The actual power curve follows the theoretical fairly closely. contd :- | ||