The nature of "superknock" and its origins in SI engines

• Extremely high knock intensities are observed occasionally in turbo charged spark ignition (SI) engines. Such events have been informally described as "Super knock" and are often associated with pre-ignition. Knock is initiated by auto ignition at one or more "hot spots". The mode of propagation of the resulting pressure wave depends on the propagation velocity of the auto ignitive front. When this becomes coupled with the acoustic wave, a localised detonation begins to develop, resulting in a very high rate of pressure rise. It is shown, through semi quantitative analysis including chemical kinetic calculations, that developing detonation becomes more likely when end-gas pressures and temperatures increase and might be the reason for "Super knock".

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Farkostteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Vehicle Engineering (hsv//eng)

Nyckelord

Auto-ignition

Chemical kinetics

Gas pressures

High rate

Hot spot

Knock intensity

Pressure waves

Propagation velocities

Semi-quantitative analysis

SI Engines

Spark ignition engines

Acoustics

Combustion knock

Detonation

Engines

Ignition

Fuel economy

Publikations- och innehållstyp

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