Fuel injected upstream of the catalyst evaporates and reacts in the catalyst. The catalytic combustion generates heat which heats the DPF to a temperature where soot is rapidly oxidized.
The control unit monitors the system during operation, determines when a regeneration event is needed, and adjusts the fuel dosing rate to match exhaust gas mass flow rate and necessary temperature increase.
The start and stop sequences used ensures safe operation during regenerations and prevents clogging of the nozzle.