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The reduced engine speeds allow more time for autoignition chemistry to complete thus promoting the possibility of pre-ignition and so called "mega-knock". Under these circumstances, there is still significant debate as to the sources of the pre-ignition event. [3] Pre-ignition and engine knock both sharply increase combustion chamber temperatures.
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.
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 first known flight of an aircraft powered by a pulse detonation engine took place at the Mojave Air & Space Port on 31 January 2008. [4] The project was developed by the Air Force Research Laboratory and Innovative Scientific Solutions, Inc. The aircraft selected for the flight was a heavily modified Scaled Composites Long-EZ, named ...
Detonation (from Latin detonare 'to thunder down/forth') [1] is a type of combustion involving a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it.
Low-speed pre-ignition (LSPI), also known as stochastic pre-ignition (SPI), [1] is a pre-ignition event that occurs in gasoline vehicle engines when there is a premature ignition of the main fuel charge. [2] LSPI is most common in certain turbocharged direct-injection vehicles operating in low-speed and high-load driving conditions. [3]
In World War II, xylidine was an important antiknock agent in very high performance aviation gasolines. Its purpose was to permit high levels of boost pressure in multiple-stage turbochargers, and thus high power at high altitudes, without causing detonation that would destroy the engine.
This causes the cylinder head temperature to increase to a very high level, which dramatically increases the risk of detonation (see: engine knocking). Adding the ADI fluid raises the mean octane level of the charge preventing pre-ignition and also lowers the cylinder temperatures to a more acceptable level.