The Effects of Two Catalyzed Particulate Filters on Exhaust Emissions from a Heavy Duty Diesel Engine: Filtration and Particulate Matter Oxidation Characteristics Studied Experimentally and Using a 1- D 2- Layer Model

A 1-D 2-layer model developed previously at MTU was used in this research to predict the pressure drop, filtration characteristics and various properties of the particulate filter and the particulate deposit layer. The model was used along with dilute emission data to characterize two catalyzed particulate filters (CPFs) having different catalyst loading and catalyst application processes. The model was calibrated and validated with data obtained from steady state experiments conducted using a 1995 Cummins M11-330E heavy-duty diesel engine with manual EGR with different fuels for the two different CPFs. The two different catalyzed particulate filters were CPF III (5 gms/ft³ Pt) and CPF V (50 gms/ft³ Pt). Both the CPFs had cordierite substrates with CPF III and CPF V had MEX and NEX catalyst type formulation respectively. The CPF III filter was catalyzed using a solution-impregnated process while the CPF V filter was catalyzed using a wash coat process. Experiments with the CPF III were conducted using conventional low sulfur fuel (CLSF) while ultra low sulfur fuel (ULSF) was used in conjunction with the CPF V. The model was used to predict the pressure drop, particulate mass retained inside the CPF, particulate mass filtration efficiency and concentration downstream of the CPFs with good agreement between the experimental and simulated results. Emissions characterization experiments were conducted for the CPFs in the dilute exhaust at rated speed (1800 rpm) and 25, 50, 75 and 100 % load conditions designated as Modes 11, 10, 9 and 8 respectively. The emissions characterized included, 1)TPM, SOL, SOF and sulfates using the gravimetric method, 2) TC, EC and OC using the thermal optical method (TOM), 3) gas phase emissions and 4) particle The two CPFs were compared based on the raw experimental, dilute experimental and simulated results to determine the influence of the differences in the CPFs on their performance.