Analysis of pre-ignition to super-knock: Hotspot-induced deflagration to detonation

• Detonation in super-knock was demonstrated for the first time by optical diagnostics.
• Pre-ignition was captured under high temperature and high pressure conditions.
• Detonation is initiated in the unburned mixture for closed system.
• High pressure oscillation induced by detonation.
• Super-knock mechanism was proposed as DDP.

Occurrence of sporadic super-knock is the main obstacle in the development of advanced gasoline engines. By utilizing a rapid compression machine, events of pre-ignition and super-knock in a closed system under high temperature and high pressure were captured by synchronous high-speed direct photography and pressure measurement, with the results demonstrating that the mechanism of super-knock is constituted by hotspot-induced deflagration to detonation followed by high-pressure oscillation (DDP).

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