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).
Comparison of the Lorraine and Goshawk engines, focusing on gas velocity, mechanical efficiency, friction losses, and ignition systems.
| Identifier | WestWitteringFiles\Q\February1927-March1927\ 110 | |
| Date | 2nd February 1927 guessed | |
| contd :- -6- fallen appreciably before this velocity on the Goshawk although the maximum value occurs about 130 ft/sec. For the former gas velocity the corresponding engine speed on the Lorraine is 2750 r.p.m. while on the Goshawk it is just below 2000 r.p.m. which is probably one of the reasons why the Lorraine maintains a high volumetric efficiency a up to a higher speed than the Goshawk which is shewn by the M.E.P. curves. On Print 3. are given compression pressure and mechanical efficiency curves. The overall mechanical efficiency of the Lorraine is higher than the Goshawk but actually there is little difference in the power absorbed in rotating the engine up to 2000 r.p.m. although above this it becomes greater. The higher efficiency is due to the greater specific power output. Perhaps a better comparison of the friction losses of these two engines is given on Print 12. which shews the horse power absorbed in rotating the engine per unit capacity and by this basis of comparison we avoid including any advantage resulting from higher compression ratio and other factors. We see for its capacity the Lorraine loses more power in rotating the engine than the 20 HP. above 2000 r.p.m. The loss consists of that due to both friction and pumping. IGNITION AND SPARK PLUG POSITION. Delco dual coil ignition is employed provided with the usual automatic advance. The two spark plugs are symmetrically arranged on opposite sides of the combustion chamber and the times of ignition are synchronised. The synchronisation is not electrical but relies upon the setting of the contd :- | ||