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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.
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.
To detect knock, a piezoelectric knock sensor (basically a microphone) bolted to the engine block responds to unique frequencies caused by engine knock. The sensor generates a small voltage that is sent to the electronic control unit , which processes the signal to determine if, in fact, knock is occurring.
In both cases, combustion timing is explicitly controlled. In an HCCI engine, however, the homogeneous mixture of fuel and air is compressed and combustion begins whenever sufficient pressure and temperature are reached. This means that no well-defined combustion initiator provides direct control.
In 1995, leaded fuel accounted for only 0.6% of total gasoline sales and less than 2,000 tons of lead per year. From January 1, 1996, the Clean Air Act banned the sale of leaded fuel for use in on-road vehicles in the United States. Possession and use of leaded gasoline in a regular on-road vehicle now carries a maximum US$10,000 fine in the ...
Pressure in cylinder pattern in dependence on ignition timing: (a) - misfire, (b) too soon, (c) optimal, (d) too late. In a spark ignition internal combustion engine, ignition timing is the timing, relative to the current piston position and crankshaft angle, of the release of a spark in the combustion chamber near the end of the compression stroke.
This one at least lasted 2–3 years but then was discontinued due to improper technical contrivances. Hot air engines is a story of trials and errors, and it took another 20 years before hot air engines could be used on an industrial scale. The first reliable hot air engines were built by Shaw, Roper, Ericsson. Several thousands of them were ...
A continuous stream of air flows through the air-breathing engine. This air is compressed, mixed with fuel, ignited and expelled as the exhaust gas. In reaction engines, the majority of the combustion energy (heat) exits the engine as exhaust gas, which provides thrust directly. Examples. Typical air-breathing engines include: Reciprocating engine