.5.6. Fuel burner
The use of a burner system is a straightforward way
to heat up the catalyst. Figure 12(f) is a simplified
schematic of a burner catalyst system. The combus-
tion chamber is located just in front of the converter
to ensure rapid and efficient heat transfer. When the
engine is started a temperature sensor, located on the
converter shell, checks whether the catalytic converter
is above or below its light-off temperature. 74 If it
detects a lower temperature, the burner is turned on
for a certain period of time defined by the temperature
level. With the start of the burner the secondary air
pump and ignition are switched on and shut-off valves
for both fuel and secondary air are opened. By
means of a sparking voltage the primary side of the
ignition module detects whether the ignition function
is working properly. Only when this condition is met,
the fuel is added by controlling the fuel supply system,
metered in the fuel regulator to a constant flow
rate and supplied to the burner nozzle virtually at
atmospheric pressure. As soon as a sufficiently high
catalyst bed temperature is sensed, both secondary air
and fuel supply shut-off values are reset to their
normally closed positions.