Practical Achievable Performance in Diesel Oxidation Catalyst Temperature Control

Practical Achievable Performance in Diesel Oxidation Catalyst Temperature Control — This paper proposes a simple control-oriented model for a Diesel Oxidation Catalyst (DOC). This distributed parameter model accounts for spatially distributed heat generation due to oxidation of reductants. It aims at being used in the context of DOC outlet temperature control, which is required during Diesel Particulate Filter (DPF) active regeneration process. The paper focuses particularly on phenomena involved during variations of gas flow rate through the DOC. These variations take place during changes of engine operating points due to driver’s requests: they are large and frequent, and cannot be avoided. Experimental results presented in this paper show that an increase in the gas flow rate, at constant inlet HC concentration, tends to make DOC outlet temperature overshoot. On the contrary, a decrease in the gas flow rate tends to make DOC outlet temperature undershoot. Using an intra-catalyst measurement, it is shown that these disturbances are related to the inherent distributed 2 Oil & Gas Science and Technology – Rev. IFP Energies nouvelles nature of the system. Compensating for observed outlet temperature variations is physically limited (by actuation limits and reasonable use of the system) and creates a delayed DOC outlet temperature disturbance. As a consequence, it seems that there exists a practical limit for the DOC outlet temperature control performance, which is, for the presented 4-inch long (1.65-L) DOC, approximately ±15◦C around the desired outlet temperature. The proposed simple model, its experimental validation, and the obtained analysis of performance based on testbench results are the main contributions of the article.