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In spark-ignition internal combustion engines, knocking (also knock, detonation, spark knock, pinging or pinking) occurs when combustion of some of the air/fuel mixture in the cylinder does not result from propagation of the flame front ignited by the spark plug, but when one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front.
It's commonly known as "Detonation or Knock". Engine management systems can overcome pre ignition by the means of a knock or detonation sensor. The sensor will detect pre ignition and retard the engines timing to protect the engine from damage. Undesired engine behavior will occur such as loss of performance or power.
Level of service (LOS) is a qualitative measure used to relate the quality of motor vehicle traffic service. LOS is used to analyze roadways and intersections by categorizing traffic flow and assigning quality levels of traffic based on performance measure like vehicle speed, density, congestion, etc.
However, detonation waves may also be used for less destructive purposes, including deposition of coatings to a surface [25] or cleaning of equipment (e.g. slag removal [26]) and even explosively welding together metals that would otherwise fail to fuse. Pulse detonation engines use the detonation wave for aerospace propulsion. [27]
Often one injector may clog while the others carry on normally allowing mild detonation in one cylinder that leads to serious detonation, then pre-ignition. [2] The challenges associated with pre-ignition have increased in recent years with the development of highly boosted and "downspeeded" spark ignition engines.
The basic concept of an RDE is a detonation wave that travels around a circular channel (annulus). Fuel and oxidizer are injected into the channel, normally through small holes or slits. A detonation is initiated in the fuel/oxidizer mixture by some form of igniter. After the engine is started, the detonations are self-sustaining.
The phenomenon is exploited in pulse detonation engines, because a detonation produces a more efficient combustion of the reactants than a deflagration does, i.e. giving a higher yields. Such engines typically employ a Shchelkin spiral in the combustion chamber to facilitate the deflagration to detonation transition. [2] [3]
A pulse detonation engine (PDE) is a type of propulsion system that uses detonation waves to combust the fuel and oxidizer mixture. [ 1 ] [ 2 ] The engine is pulsed because the mixture must be renewed in the combustion chamber between each detonation wave and the next.