Mechanism for pressure drop variation caused by filtration of diesel particulates

Abstract

Diesel engines have better fuel consumption efficiency than gasoline engines. To reduce the particle emission in the diesel exhaust, a ceramic filter, called diesel particulate filter, has been developed. Unfortunately, the pressure drop (filter backpressure) continues to increase, resulting in an increase in fuel conversion rate as well as available torque. In order to develop the filter with lower pressure drop, the filter structure is strategically optimized in the design of the filter product. To do so, the information on phenomena during the filtration is needed. This article sets out numerically to study the variation in the pressure drop when the particulates are trapped inside the porous walls of diesel particulate filter. To discuss the flow dynamics and pressure drop caused by the soot deposition, the numerical simulation is purposely conducted in two-dimensional coordinate. This is because the variation in flow channel through pores during the filtration can be visualized easily. Here, eight filters were tested systematically. Utilizing these simulation results, we try to explain the main factors for the pressure drop variation during the filtration. Based on the presented results, it is shown that the flow field is gradually varied during the filtration. The knowledge regarding the well-known pressure drop variation observed in the stage from the depth filtration to the surface filtration is provided.