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).
Investigation into engine pre-ignition and the effect of warming up the fuel-air charge.
Identifier | ExFiles\Box 34\2\ Scan105 | |
Date | 15th May 1918 | |
Contd. -4- EH1/LG15.5.18. engine which demonstrates the effect of warming up the charge it frequently happens when the ignition is switched on to start the engine, the coil "buzzes" for some time and then after a period of time the charge fires. The only effect we can see has happened is that the spark warms up the portion of the charge round the plug so that it ignites. Another point we have investigated lately, is that if an engine has been running full power and is stopped down quickly by closing the throttle and switching off, or switching off without closing the throttle, it will drop in speed without firing until it is turning very slowly then it will start firing, pre-igniting and so keep running for a considerable time. We frequently have had it happen that an engine has been stopped down and we have gone to turn it after it has stopped for a minute or two and it has pre-ignited. One would assume that the ignition takes place due to over-heating ignition plug or exhaust valve because they form the hottest portions of the combustion chamber. On our test engine however, we are able to observe that the ignition plugs and exhaust valves are quite cool and black when this ignition takes place. We have removed the ignition wires altogether so as to be sure there is no leakage in the switch. One would imagine that if the charge is ignited by any over-heated portion of the combustion chamber, it would go on firing immediately it is switched off and when the combustion chamber must be hottest, but when it has cooled down. The only reason we can see that it fires at the low speed, is that then the charge is warmed up. There are two Contd | ||