Spark plug

The normal process is a rapid-but-smooth combustion of the fuel-air mixture in the engine due to the propagation of a flame front emanating from the spark created between the electrodes of the spark plug. 

Figure C2.11.4. A commercial spark plug witli its electrically insulating ceramic body comprised of alumina and glass (white portion).

Figure C2.11.5. Scanning electron micrographs showing the microstmcture of an alumina ceramic spark-plug body (a) fracture surface and (b) polished and thennally etched cross section.

Lasdy, the importance of electroceramic substrates and insulators should not be overlooked. Here one strives to raise the breakdown strength by eliminating the interesting conduction mechanisms just described. Spark plugs, high voltage insulators, and electronic substrates and packages are made from ceramics like alumina, mullite [55964-99-3] and porcelain [1332-58-7]. 

More complex shapes can be made by cold isostatic pressing (CIP). CIP uses deformable mbber molds of the required shape to contain the powder. The appHcation of isostatic pressure to the mold suspended in a pressure transfer media, such as oil, compacts the powder. CIP is not as easily automated as uniaxial pressing, but has found wide appHcation in the preparation of more complex shapes such as spark plug insulators (26). 

Tips of platinum, platinum—nickel alloy, or iridium can be resistance-welded to spark-plug electrodes for improved reHabiHty and increased lifetime. These electrodes are exposed to extremely hostile environments involving spark erosion, high temperature corrosion, thermal shock, and thermal fatigue. 

The mechanism of poisoning automobile exhaust catalysts has been identified (71). Upon combustion in the cylinder tetraethyllead (TEL) produces lead oxide which would accumulate in the combustion chamber except that ethylene dibromide [106-93-4] or other similar haUde compounds were added to the gasoline along with TEL to form volatile lead haUde compounds. Thus lead deposits in the cylinder and on the spark plugs are minimized. Volatile lead hahdes (bromides or chlorides) would then exit the combustion chamber, and such volatile compounds would diffuse to catalyst surfaces by the same mechanisms as do carbon monoxide compounds. When adsorbed on the precious metal catalyst site, lead haUde renders the catalytic site inactive. 

Artefacts Screwdrivers dismantled spark plug PVC yachting anorak, polymer rope, etc. 

In gas turbines with multiple eans, the deteetors are mounted in eans not equipped with spark plugs to assure flame propagation between eans during startup. Onee the unit is running, more than one indieator must indieate a loss of flame to trip the maehine, although the loss of flame in only one ean is indieated on the annuneiator panel. 

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