Steady State Investigations of DPF Soot Burn Rates and DPF Modeling

This work presents the experimental investigation of Diesel Particulate Filter (DPF) regeneration and a calibration procedure of a 1D DPF simulation model based on the commercial software AVL BOOST v. 5.1. Model constants and parameters are fitted on the basis of a number of steady state DPF experiments where the DPF is exposed to real engine exhaust gas in a test bed. The DPF is a silicon carbide filter of the wall flow type without a catalytic coating. A key task concerning the DPF model calibration is to perform accurate DPF experiments because measured gas concentrations, temperatures and soot mass concentrations are used as model boundary conditions. An in-house developed raw exhaust gas sampling technique is used to measure the soot concentration upstream the DPF which is also needed to find the DPF soot burn rate. The soot concentration is measured basically by filtering the soot mass of a sample gas continuously extracted from the engine exhaust pipe for 1-2 hours while also measuring the gas flow passed through the filter. A small silicon carbide wall flow DPF protected in a sealed stainless steel filter housing is used as sample filter. Measured DPF pressure drop characteristics are used to fit model constants of soot and filter properties. Measured DPF gas conversions and soot burn rates are used to fit model activation energies of four DPF regeneration reactions using O2 and NO2 as reactants. Modeled DPF pressure drops and soot burn rates are compared to the steady state DPF experiments in the temperature range between 260 and 480 °C. The model widely reproduces the experimental results. Especially the exponential soot burn rate versus temperature is accurately reproduced by the model.