preignition


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Related to preignition: Spark knock

preignition

[¦prē·ig′nish·ən]
(mechanical engineering)
Ignition of the charge in the cylinder of an internal combustion engine before ignition by the spark.

preignition

The ignition of the fuel-air charge prior to the spark plug firing. Preignition caused by some other ignition source such as an overheated spark plug tip, carbon deposits in the combustion chamber, and, rarely, a burned exhaust valve. All act as a glow plug to ignite the charge. Preignition occurs during the compression stroke, and the engine continues to fire with the ignition system switched off, although probably not all its cylinders. There is no explosion as in a detonation and the rise of temperature and pressure is much greater, probably resulting in catastrophic consequences. Preignition is often experienced when attempting to start a hot engine or during an attempt to shut down a hot engine, and it usually results in a backfire through the intake manifold.
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However, this could not be confirmed because their intake pressure operating ranges were limited by surface preignition, presumably caused by the long-reach spark plug.
An accelerometer is used to measure preignition in gasoline-burning engines.
This deposit tends to block proper heat transfer out of the cylinder, raising temperatures throughout the combustion cycle and increasing the tendency toward detonation or preignition.
The "ping" associated with low-grade fuel in a car can become preignition and explosive detonation in an aircraft engine after only seconds of high-power operation, causing engine failure.
The fuel variable included the constant heat of preignition of dry fuels ([Q.sub.d]: 581 kJ/kg) such that the fuel variable had the same units as intensity (kilowatts per metre):
To reduce the tendency for preignition, motorists are required to use high-octane fuels, which are more expensive than regular fuels.
Pre-Launch Insurance (sometimes referred to as "preignition," transit and ground property) is generally maintained by the owner-operator to cover the satellite and related equipment against all risks of physical loss or damage occurring at any time or place prior to launch, including while in the transit, storage, "preignition (while at the launch site)," mating to the launcher and other phases.
Severe or extreme detonation can quickly lead to engine destruction directly, or by launching preignition, which can destroy an engine in seconds.
It is worth noting that the conclusions of this study apply to conventional end-gas knock only, and do not consider engine oil impacts on stochastic preignition, which is a distinctly different phenomenological event.
These insights are extended to the discussion of superknock, which previous studies suggest, is a manifestation of developing detonation (DD) that can occur at low values of [xi] High values of [P.sub.ko] needed for [xi] to be low enough for DDs to occur can only come about because of another stochastic process - preignition, which is also briefly discussed.
The term "cool flame" is conventionally used to collectively describe the low- and intermediate-temperature (approximately 500K-900 K) oxidative preignition reactions emerging in reactive systems fed with organic fuels, such as saturated and unsaturated hydrocarbons, alcohols, aldehydes, ketones, acids, oils, ethers, and waxes [13, 14].