Abstract
The effect of the pore size distribution on size-resolved filtration efficiency was investigated for two ceramic particulate filters using particulate matter (PM) generated by a spark-ignition direct-injection engine fueled with gasoline. The cordierite filter tested had a porosity of 43%, a median pore diameter of 12 μm, and a wide pore size distribution with a lognormal standard deviation (σ′) of 0.4. The aluminum titanate filter had very similar porosity, median pore diameter, and thickness, but significantly narrower pore size distribution (σ′ = 0.1). The testing of two filters under identical experimental conditions enabled the impact of the pore size distribution on filtration performance to be evaluated. Filtration experiments were performed focusing on just the filter wall, starting from a clean filter until the transition to cake filtration (filtration efficiency > 99%). Time-resolved particle size distribution measurements were used to evaluate the progression of filtration performance and estimate trapped mass within the filter. The aluminum titanate filter, with a narrow pore size distribution, exhibited significantly better diffusion capture efficiency. The negative impact of higher flow velocity on diffusion capture efficiency was more pronounced for a narrower pore size distribution. Flow distributions measured using capillary flow porometry were used to develop a cylindrical pore flow model to understand the impact of the differences in pore size distribution on observed trends in diffusion capture efficiency within a clean filter. The model predicted a larger impact of superficial velocity on capture efficiency for filters with narrower pore size distributions as seen from the experiments. The experimental results and data demonstrate that the bubble point diameter and width of the pore size distribution significantly influence diffusion capture efficiencies for filters with very similar median pore diameter, porosity, and thickness.
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Data Availability
Data supporting the findings of this study are available from the corresponding author [VS] on request.
Abbreviations
- CAD:
-
crank angle degrees
- CFP:
-
capillary flow porometry
- CoV:
-
coefficient of variation
- CPMA:
-
centrifugal particle mass analyzer
- CT:
-
computed tomography
- DMA:
-
differential mobility analyzer
- EEPS:
-
engine exhaust particle sizer
- EFA:
-
exhaust filtration analysis system
- EOI:
-
end of injection
- FE:
-
filtration efficiency
- GDI, :
-
gasoline direct ignition
- GPF:
-
gasoline particulate filter
- IMEP:
-
indicated mean effective pressure
- IPSD:
-
integrated particle size distribution
- LEP:
-
liquid extrusion porosimetry
- LIP:
-
liquid intrusion porosimetry
- MIP:
-
mercury intrusion porosimetry
- PFD:
-
partial flow diluter
- PM:
-
particulate matter
- PSD:
-
particle size distribution
- SIDI:
-
spark-ignition direct-injection
- SMPS:
-
scanning mobility particle spectrometer
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Acknowledgments
The authors would also like to thank the filter manufacturers for providing the wafer samples used in the present study.
Funding
This work was funded by General Motors through the Collaborative Research Laboratory at the University of Wisconsin-Madison Engine Research Center and the US Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy, Vehicle Technology Office.
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Viswanathan, S., Stewart, M.L. & Rothamer, D.A. Experimental Investigation of the Effect of Pore Size Distribution on Nano-particle Capture Efficiency Within Ceramic Particulate Filters. Emiss. Control Sci. Technol. 7, 26–40 (2021). https://doi.org/10.1007/s40825-021-00184-4
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DOI: https://doi.org/10.1007/s40825-021-00184-4