Slow Motion Shows Knocking and Non-Knocking Explosions 360126

PREVIOUS studies of flame propagation in a gasoline engine have suffered from the handicap that only a partial view of the combustion space was obtained. This disadvantage has now been overcome by covering the whole top of a single-cylinder ell-head engine with a quartz plate so that an unobstructed view of the combustion-chamber is allowed.
To record, at known intervals, the progress and shape of the flame fronts a special camera has been built which photographs 30 individual pictures of a single explosion. Simultaneously, a pressure-time card is recorded. The interval between pictures is 2.4 crankshaft degrees; consequently, 5000 pictures per sec. are photographed at an engine speed of 2000 r.p.m.
These photographs may be studied individually or projected as “slow-motion” movies which show the ignition spark, the spread of the flame through the charge, and the gas movements behind the flame.
Pictures of non-knocking and knocking explosions are presented. The latter reveal in a most striking manner the occurrence of spontaneous ignition in sections of the charge well ahead of, and completely separated from, the advancing flame front.


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