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Electron microscopic time-lapse visualization of surface pore filtration on particulate matter trapping process
Ryoko Sanui1, Katsunori Hanamura1
1Department of Mechanical and Control Engineering, Tokyo Institute of Technology, Meguro-ku, Tokyo, Japan.
Abstract:
A scanning electron microscope (SEM) was used to dynamically visualize the particulate matter (PM) trapping process on diesel particulate filter (DPF) walls at a micro scale as 'time-lapse' images corresponding to the increase in pressure drop simultaneously measured through the DPF. This visualization and pressure drop measurement led to the conclusion that the PM trapping in surface pores was driven by PM bridging and stacking at constricted areas in porous channels. This caused a drastic increase in the pressure drop during PM accumulation at the beginning of the PM trapping process. The relationship between the porous structure of the DPF and the depth of the surface pore was investigated in terms of the porosity distribution and PM penetration depth near the wall surface with respect to depth. The pressure drop calculated with an assumed surface pore depth showed a good correspondence to the measured pressure drop.
Insights
Diesel particulate filters trap particulate matter (PM) in surface pores through bridging and stacking, causing increased pressure drop. This study visualizes PM trapping dynamics and relates it to filter structure.
Area of Science:
- Mechanical Engineering
- Materials Science
- Environmental Science
Background:
- Diesel engines produce particulate matter (PM), necessitating exhaust aftertreatment systems like diesel particulate filters (DPF).
- Understanding PM trapping mechanisms is crucial for optimizing DPF efficiency and longevity.
- Previous studies often lacked micro-scale dynamic visualization of the PM trapping process.
Purpose of the Study:
- To dynamically visualize the micro-scale particulate matter (PM) trapping process on diesel particulate filter (DPF) walls.
- To correlate PM trapping mechanisms with pressure drop changes within the DPF.
- To investigate the relationship between DPF porous structure and PM penetration depth.
Main Methods:
- Utilized scanning electron microscopy (SEM) for time-lapse visualization of PM trapping.
- Simultaneously measured pressure drop across the DPF during PM accumulation.
- Analyzed porosity distribution and PM penetration depth in relation to filter depth.
Main Results:
- PM trapping in surface pores is driven by bridging and stacking at constricted areas.
- This mechanism causes a significant increase in pressure drop at the beginning of PM accumulation.
- Calculated pressure drop based on assumed surface pore depth correlated well with measured values.
Conclusions:
- PM trapping in DPFs is a dynamic process influenced by pore structure and PM accumulation patterns.
- The initial drastic pressure drop increase is attributed to PM bridging and stacking in surface pores.
- The study provides insights into DPF filtration mechanisms and validates models for predicting pressure drop.
