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ABSTRACT
Due to its high filtration efficiency, wall-flow diesel particulate filter (DPF) has become the mainstream purification device for particulate matters (PM) of diesel engine all over the world. China VI emission regulations further tightens PM emissions, which puts out higher demands on all aspects of DPF performance. In the paper, experimental and numerical study were conducted on a common-rail diesel engine for the pressure drop and temperature field characteristics of asymmetric cell technology (ACT) diesel particulate filter for silicon carbide (SiC-DPF) with high cell density and thin wall. The results show that the application advantage of ACT DPF is significant under the conditions of higher soot loading and higher engine speed while SCT DPF is more suitable for the conditions of lower soot loading (less than 4 g/L). When ash loading exceeds 30 g/L, the pressure drop of ACT DPF is remarkably lower than that of symmetric cell technology (SCT) DPF. Compared with SCT DPF, the gas flow velocity is faster at the channel outlet and the particulate concentration deposited along the axial direction is more homogeneous for ACT DPF. Therefore, pressure drop is reduced efficiently with the increasing soot loading. Moreover, the regeneration temperatures inside the ACT DPF are uniform and stable, and the peak temperature does not exceed 750°C during active regeneration with the soot loading of 8 g/L, thus regeneration is safe.
Nomenclature
| Abbreviations | = | |
| ACT | = | Asymmetric cell technology |
| CDPF | = | Catalyst diesel particulate filter |
| CO | = | Carbon monoxide |
| DOC | = | Diesel oxidation catalyst |
| DPF | = | Diesel particulate filter |
| HC | = | Hydrocarbon |
| NO | = | Nitric oxide |
| NO2 | = | Nitrogen dioxide |
| PM/PN | = | Particulate matter/particle number |
| SCT | = | Symmetric cell technology |
| SiC | = | Silicon carbide |
| Symbol | = | |
| A1 | = | Free inlet channel cross section (m2) |
| A2 | = | Free outlet channel cross section (m2) |
| d1 | = | Diameter of the DPF inlet/outlet channel (m) |
| D | = | Channel width (m) |
| F | = | Channel pressure drop correlation |
| F1 | = | Friction coefficient in the inlet channel(-) |
| F2 | = | Friction coefficient in the outlet channel(-) |
| kash | = | Ash layer permeability (m2) |
| ksoot | = | Soot cake layer permeability (m2) |
| kwall,i | = | Loaded filter substrate wall permeability of discretized slab (m2) |
| L | = | Channel length (m) |
| i | = | Filter wall discretization interval number |
| p1 | = | Pressure in the inlet channel (Pa) |
| p2 | = | Pressure in the outlet channel (Pa) |
| Q | = | Inlet volumetric flow rate (m3/s) |
| S1 | = | Wet perimeter of the free inlet channel (m) |
| S2 | = | Wet perimeter of the outlet channel (m) |
| Uw,1 | = | Soot layer inlet velocity (m/s) |
| Uw,1-2 | = | Ash layer wall velocity (m/s) |
| Uw,2 | = | Substrate wall velocity (m/s) |
| Uinlet | = | Inlet gas velocity (m/s) |
| Uoutlet | = | Outlet gas velocity (m/s) |
| vw,1 | = | Wall velocity in the inlet channel (m/s) |
| vw,2 | = | Wall velocity in the outlet channel (m/s) |
| Vtrap | = | Total DPF volume (m3) |
| wash | = | Ash layer thickness (m) |
| wslab,i | = | Thickness of each discretized slab in the filter substrate layer (m) |
| wsoot | = | Soot cake layer thickness (m) |
| wwall | = | Substrate filter wall thickness (m) |
| Greek letter | = | |
| βash | = | Forchheimer constant in ash layer (1/m) |
| βsoot | = | Forchheimer constant in soot cake layer (1/m) |
| βwall | = | Forchheimer constant in substrate wall layer (1/m) |
| μ | = | Gas viscosity (Pa∙s) |
| ρ | = | Gas density in DPF(kg/m3) |
| ρ1 | = | gas density in the inlet channel (kg/m3) |
| ρ2 | = | Gas density in the outlet channel (kg/m3) |
| ρinlet | = | Gas density at inlet (kg/m3) |
| ρoutlet | = | Gas density at outlet (kg/m3) |
| ζcontraction | = | Contraction pressure drop coefficient(-) |
| ζexpansion | = | Expansion pressure drop coefficient(-) |
Highlight
● ACT SiC-DPF with high cell density and thin wall is the latest filter to meet the increasingly stringent emission regulations.
● The combined effects of soot and ash loading on the SCT and ACT SiC-DPF pressure drop were studied and compared in depth.
● The pressure drop intersections between SCT and ACT SiC-DPF under different diesel engine speeds are proposed.
● The particulate concentrations deposited along the axial direction are compared between SCT and ACT SiC-DPF.
● Experimental analysis was conducted about the temperature field of ACT SiC-DPF during the active regeneration.
Acknowledgments
The authors would like to acknowledge the financial supports to the research provided by National Natural Science Foundation of China (51866004) and Scientific Research Foundation of Yunnan Provincial Department of Education (2019Y0033).