Exhaust temperature control for safe and efficient thermal regeneration of diesel particulate filter

Abstract

Abstract It is crucial for the diesel particulate filter (DPF) that the exhaust temperature at the DPF inlet is well managed and accurately controlled during the thermal regeneration process, in order to ensure the integrity of the filter and improve regeneration efficiency simultaneously. However, this is challenging because the DPF and the upstream diesel oxidation catalyst are complex systems with complicated chemical, thermal and fluid phenomena, especially in real-world driving where the operation and environment conditions are varying and unpredictable. In some cases when the engine speed is suddenly dropped to idle (DTI) from normal operation conditions, uncontrolled regeneration events may occur and result in excessive temperature spikes inside the DPF that may melt down the filter. The objective of this work is to improve safe, reliable and efficient filter operation during the DPF thermal regeneration process, thus reducing the risk of destructive melting of the DPF. Firstly, an experimental method based on the DTI regeneration tests is investigated under a wide range of operation conditions with different soot load levels and regeneration temperatures. Results indicate that the target regeneration temperature curve can be derived as an empirical function of the amount of soot loading in the DPF, which is essential to ensure regeneration safety of the filter in runtime. Then, a novel control strategy combining a model-based feedforward control law and a feedback control law based on the internal model control approach is proposed and developed. The presented control strategy is finally validated under transient conditions in the real driving cycles. Results show that the temperature overshoot is less than 5% during the initial regeneration control stage and the tracking error remains within ±15 °C of the target regeneration temperature, which is beneficial to safe and efficient thermal regenerations of the filter.