USING a high-speed motion picture camera, the authors made flame photographs in three different engines operating under a number of different conditions described as after-running, autoignition, preignition, and knock.
Engine explosions occurring during after-running are recorded in a combustion chamber relatively free from deposits, and explosions typical of autoignition, preignition, and knock were photographed in the presence of combustion-chamber deposits.
In general, it is shown that combustion-chamber deposits in the process of purging themselves eliminate one problem, namely the tendency of the combustion space to fill up with solid material; but at the same time other problems are created, those of autoignition, and “wild ping” or heavy knock which loosens the deposits.