Optimization of DPF regeneration with a cylinder pressure based combustion control

Due to steadily tightening exhaust emission legislations and average fleet consumption the optimization of Diesel engines and its after-treatment is necessary more than ever. Therefore, an optimized interaction between combustion and exhaust after treatment is getting more and more important for meeting further emission legislation targets and reducing fuel consumption. Due to its effective filtration efficiency of particulate matter, the wall-flow Diesel Particulate Filter (DPF) has been established as a basic technology of exhaust after-treatment. With increasing accumulation of particulate matter the exhaust back pressure rises, which necessitates a regeneration of the DPF at regular intervals. As the engine exhaust temperatures required for DPF regeneration are not achieved in normal combustion mode, except during full-load operation, the engine management system has to take different measures to raise the exhaust temperature, if no fuel additives are used. This is usually done by a special combustion mode with intake throttling and a modified injection profile. In order to make the combustion inefficient the fuel is injected as late as possible. The latest possible crank angle is limited by combustion stability. Exceeding this stability limit leads to unstable combustion and in the worst case to misfire.