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).
Analysing engine pumping losses, scavenging pressure, and potential improvements to valve timing and design.
| Identifier | ExFiles\Box 54\4\ Scan051 | |
| Date | 25th September 1924 | |
| R.R. 493a (50a) (D.B. 175 25-9-24) J.H.D. EXPERIMENTAL REPORT. -2- Expl. No. REF: Hs {Lord Ernest Hives - Chair} /Rn {Mr Robinson} /LG5.9.24. transfer port for the supercharge is only .625" X .687" in area with irregular outline, while the scavenging is also restricted. We expect the pumping losses to be slightly increased when the engine is running under its own power. Increasing the scavenging pressure by operating the relief valve on the reservoir, augments the pumping losses from 3 lbs/sq.in. to 18 lbs/sq.in., the whole motoring loss is increased by over 30%. This is evidently sufficient to nullify any resultant gain in I.M.E.P. as the engine will not run under its own power with this scavenging pressure. As a summary of our impressions of the engine at the moment, we should say that by attention to the ignition and carburation, we may be able to improve the I.M.E.P. slightly. We believe that further improvement will be possible by altering the period and timing of the scavenging port. It seems, however, as if it will be necessary to completely re-design the rotary valve if any B.HP. is to be obtained or high speed work indulged in, as the mechanical efficiency at present is impossible. For thermal efficiency, the exhaust valve period and timing may require attention while the fact that the long transfer port is part of the combustion chamber will be bad for this factor. Piston friction will also be a serious factor at higher speeds. ---------------- Hs {Lord Ernest Hives - Chair} /Rn. {Mr Robinson} | ||