Catalytic Combustion – In a catalytic diesel filter, fuel-derived hydrocarbons introduced into the exhaust gases through an in-cylinder fuel injection strategy or through a dedicated exhaust injector are oxidized over an oxidation catalyst.
Flame combustion - The fuel is burned in an oil burner, usually with a dedicated supply of combustion air, and the flame enters the exhaust system.
Combined Flame and Catalytic Combustion – A combination of the above methods where the fuel burner is followed by a catalytic combustion system.
Burner systems offer greater regeneration flexibility at the expense of more complex hardware. Burner systems can be designed to regenerate under any engine operating condition, whereas catalytic combustion systems require a certain minimum catalyst temperature. Even if additional thermal management strategies are implemented, regeneration may not be possible in the catalytic system under low engine load conditions when exhaust gas temperatures are below the catalyst light-off temperature. In the combined burner-catalyst approach, a small burner (micro-burner) installed upstream of the catalyst facilitates catalyst light-off regardless of engine operating conditions.
The fuel burner system may be designed to perform regeneration under any engine operating condition, or may require the engine to operate while regenerating under certain conditions (e.g., at low idle). Therefore, burner systems can be divided into two categories:
1. Single point burner system
Single-point filtration systems require vehicle operator intervention to perform regeneration, which occurs under steady-state conditions. When the filter control system detects that the maximum soot load has been reached, it alerts the operator that filter regeneration should be initiated. Single-point filters require the engine to idle during the regeneration cycle (usually 15-20 minutes) or use a blower to provide airflow and require the engine to be shut down for regeneration. The burner operates at constant power, which is selected to increase the exhaust gas temperature to the desired level.
The use of single-point systems is limited to certain retrofit applications, such as construction machinery or diesel forklifts operating in enclosed spaces. They are not suitable for on-road use due to the required operator intervention and idling or shutdown time required during regeneration.
2. Full flow burner system
The full-flow burner system features fully automatic regeneration based on actual exhaust gas flow during the vehicle's normal operating cycle. When a predetermined soot load accumulates, the filter controller triggers regeneration without intervention or knowledge of the vehicle operator. The filter control unit starts the burner and controls its operation to maintain the required filter temperature. After the filter is cleaned, the controller stops the burner and the filter enters the next loading cycle.
Full flow oil burner filters require an electronic control unit to maintain thermal balance regeneration, thereby minimizing overall thermal stress on the filter. Here, the term "thermal balance" refers to the thermal energy generated by the burner corresponding to the soot