Numerical simulation on trapping efficiency of steady filtration process indiesel particulate filter and its experimental verification

ZHANG Gui-ju(张桂菊)^{1, 2}, EJia-qiang(鄂加强)^{1, 3}, ZUO Qing-song(左青松)¹, GONG Jin-ke(龚金科)^{1, 3}, ZUO Wei(左威)^{1, 3}, YUAN Wen-hua(袁文华)²

(1. College of Mechanical and Vehicle Engineering, Hunan University, Changsha, 410082, China;
2. Department of Mechanical and Energy Engineering, Shaoyang University, Shaoyang 422004, China;
3. Institute of new energy and energy-saving &emission-reduction technology,
Hunan University, Changsha 410082, China)

Abstract:Taking wall-flow diesel particulate filter (DPF) as the research objective and separately assuming its filtering wall to be composed of numerous spherical or cylindrical elements, two different mathematical models of steady filtration for wall-flow diesel particulate filter were developed and verified by experiments as well as numerically solved. Furthermore, the effects of the macro- and micro-structural parameters of filtering wall and exhaust-flow characteristic parameters on trapping efficiency were also analyzed and researched. The results show that: 1) The two developed mathematical models are consistent with the prediction of variation of particulate size; the influence of various factors on the steady trapping efficiency is exactly the same. Compared to model 2, model 1 is more suitable for describing the steady filtration process of wall-flow diesel particulate filter; 2)The major influencing factors on steady trapping efficiency of wall-flow diesel particulate filter are the macro-and micro-structural parameters of filtering wall; and the secondary influencing factors are the exhaust-flow characteristic parameters and macro-structural parameters of filter; 3)The steady trapping efficiency will be improved by increasing filter body volume, pore density as well as wall thickness and by decreasing exhaust-flow, but effects will be weakened when particulate size exceeds a certain critical value; 4) The steady trapping efficiency will be significantly improved by increasing exhaust-flow temperature and filtering wall thickness, but effects will be also weakened when particulate size exceeds a certain critical value; 5) The steady trapping efficiency will approximately linearly increase with reducing porosity, micropore aperture and pore width.

Key words:wall-flow diesel particulate filter; steady filtration; trapping efficiency; packed-bed filtration theory; fiber filtration theory