'Knock' in Internal Combustion Engines

Abstract

THERE is evidence that the phenomenon of 'knock' in spark-ignition engines is connected with the production of peroxides in the last part of the fuel-air mixture to be burnt. Thus we have found that of all the intermediate products of combustion which have been identified in the gases sampled from the engine, the peroxides are the only ones which possess an appreciable pro-'knock' effect. Egerton et al.¹ have shown that peroxides, probably alkyl hydroperoxides, are present in the pre-combustion processes, and Stern and Polliak² have identified hydrogen peroxide in samples taken from an engine cylinder. This work has now been extended to enable quantitative determinations to be made of the total peroxide content of gas samples. At the same time, we have determined the aldehyde content.