Motortech DetCon series, Operating Manual

Page: 13 / 90

13 Rev. 02/2019
3.1 Functional Description
Pos. Designation
Valve
Spark plug
Piston
Normal Combustion
The graphics show the desired type of
combustion of the gas/air mixture in the
combustion chamber. The ignition spark
ignites the gas/air mixture. The flame front
spreads out evenly in the combustion
chamber with the specific laminar flame
speed of the gas/air mixture. The cylinder
pressure increases slightly during
combustion.
Knocking Combustion
Knocking combustion arises if the gas/air
mixture self-ignites before the actual flame
front, but after the ignition
. This system
does not detect so-called early ignition.
The reason for this is an excessive increase
in pressure and temperature of the as yet
non-combusted mixture due to the pressure
and temperature fronts preceding the normal
flame front. The pressure and temperature
fronts arising from the self-ignition, in turn,
make further self-ignitions possible. High-
frequency pressure waves arise in the
combustion chamber, which are introduced
into the engine structure via the walls of the
combustion chamber and released as air-
borne noise into the environment. The
knocking becomes audible in this way
.
Compared to normal combustion,
significantly higher peak pressures arise,
which may lead to major engine damage in
addition to the higher thermal load.
3 Intended Use