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).
Analysis of the cause of continuous explosions in the exhaust when an engine is coasting with the throttle slightly open.
| Identifier | WestWitteringFiles\P\2July1926-September1926\ Scan049 | |
| Date | 13th August 1926 | |
| contd :- -2- Hs{Lord Ernest Hives - Chair}/ACLL/LG13.8.26. ------------------ By these means we were able to reproduce the trouble laid down in each of the afore mentioned cases. From general observation of the first tests with this apparatus we were prompted to suggest the following condition which could exist and cause the trouble described in case (1) - viz: that of continuous explosions when coasting with throttle slightly open. When the engine is motored over with a small throttle opening the suction is very high, and the charge drawn in although it should be correctly proportioned with regard to fuel and air, forms only a very small proportion of the cylinder capacity. With the amount of residuals in the cylinders the resulting contents would be in all probability too diluted to fire; a state assisted by the low pressure and probable low degree of turbulence. When the exhaust valve opens the cylinder pressure would be below atmospheric - due to the high suction and no explosion - and air or exhaust gas would rush in from the exhaust manifold and further dilute the contents. The exhaust manifold, under these conditions, will gradually become charged with the mixture drawn from the carbur-etter which has not burnt in the cylinder, and after several cycles the medium drawn back past the exhaust valve will increase the combustible contents of the cylinder until just sufficiently rich to ignite. The burning would naturally be slow on account of weakness and still flaming when the exhaust valve opened would so ignite the combustible contents of the manifold and cause the noise complained of. The cycle would then be repeated. contd :- | ||