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 estimated performance of a supercharged Bentley engine.
| Identifier | ExFiles\Box 140\1\ scan0097 | |
| Date | 20th December 1934 | |
| To E.{Mr Elliott - Chief Engineer} from Hs{Lord Ernest Hives - Chair}/Smth. c. to Wor.{Arthur Wormald - General Works Manager} c. to By.{R.W. Bailey - Chief Engineer} Supercharged Bentley. Attached are estimated performance curves for the Bentley engine with various C.R's and boost pressures. The performances when supercharged have been worked out on the assumption that the effective boost temperature is the temperature of the dry air when compressed in the same manner as the mixture, and that there is no further heating of the charge. The curves may be summarised as follows :- (1) When unboosted, the maximum pressure rises almost linearly with the C.R. being 380 lbs/sq.in. at 4/1 and 1160 lbs/sq.in. at 10/1. On the other hand, increase in power per ratio of compression becomes less as the C.R. increases; thus, an increase in C.R. at high ratios involves an increase in max. pressure of 28 lbs/sq.in./B.H.P. (2) Under boosted conditions the max. pressure varies practically linearly with the power output. At 6.5/1 C.R. and with a 50% efficient blower the increase in max. pressure incurred by stepping up the power by 1 H.P. is only 6 lbs/sq.in. (3) The influence of the blower efficiency on power output is appreciable. (4) The specific fuel consumption is practically independent of the boost pressure. (5) For a constant max. pressure the power output falls linearly as the C.R. is increased. (6) For the same degree of detonation one would expect to be able to produce more power on a low compression boosted engine than on a high compression unboosted engine. We attach curves showing the unboosted and boosted performances of the Graham engine. These have been compiled from various sources, and are of somewhat doubtful authenticity, and we are writing to Graham's to confirm them. | ||