Photographic observation of knock with a rapid compression and expansion machine

A new type of rapid compression and expansion machine (RCEM) has been developed, and typical knock scenes were clearly recorded with a high speed laser shadowgraph at a speed of 100,000 frames per second. The RCEM is intended to simulate combustion in an automotive engine. Its piston is driven by an electrohydraulic servo system and is allowed to execute continuous reciprocations up to five times. The combustion chamber is a simple pancake type with an ignition plug on its side and the whole inner view is observable through a glass window on the top.