Article
A Study on Soot and Ash Accumulation Characteristics of
Diesel Particulate Filter Substrate Using Nondestructive
Computed Radiography X-ray Imaging Technique
Giyoung Park
1
, Hoyoung Ryu
1
, Manjae Kwon
1
and Seangwock Lee
2,
*
Citation: Park, G.; Ryu, H.; Kwon,
M.; Lee, S. A Study on Soot and Ash
Accumulation Characteristics of
Diesel Particulate Filter Substrate
Using Nondestructive Computed
Radiography X-ray Imaging
Technique. Appl. Sci. 2021, 11, 9483.
https://doi.org/10.3390/app
11209483
Academic Editor: Roberto Zivieri
Received: 3 September 2021
Accepted: 8 October 2021
Published: 13 October 2021
Publisher’s Note: MDPI stays neutral
with regard to jurisdictional claims in
published maps and institutional affil-
iations.
Copyright: © 2021 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
1
Graduate School of Automotive Engineering, Kookmin University, Seoul 02707, Korea;
speed3926@kookmin.ac.kr (G.P.); ioncvwz@kookmin.ac.kr (H.R.); kmj9177@kookmin.ac.kr (M.K.)
2
Department of Automotive Engineering, Kookmin University, Seoul 02707, Korea
* Correspondence: energy@kookmin.ac.kr; Tel.: +82-239-59505
Abstract:
The diesel particulate filter of a diesel engine is an after-treatment device that removes
particulate matter from exhaust emissions by filtering and oxidating them through a regeneration
process. When the diesel particulate filter is damaged, a vehicle inspection is usually performed;
if the cause is not found through using on-board diagnostics, then the diesel particulate filter is
removed, and a visual test is conducted. However, it is not easy to find the exact cause of the diesel
particulate filter being damaged, and a visual test takes a long time as the diesel particulate filter
substrate is covered by a canister. In this study, using the computed radiography X-ray imaging
technique, X-ray images were taken after placing an accumulated amount of carbon powder, similar
to soot and ash powder in the substrate. Results confirmed that carbon powder and ash powder were
shown in white in X-ray images, leading to a conclusion that distinguishing between carbon powder
and ash powder is possible by analyzing the pixel value through the image processing technique.
However, since pixel values alone are insufficient for exact quantitative evaluation, various studies
and analyses are necessary for quantitative evaluation.
Keywords:
diesel vehicle; diesel particulate filter (DPF); particulate matter (PM); soot; ash; computed
radiography (CR); X-ray; Image J
1. Introduction
Nanoparticulate matter among air pollutants is a growing environmental concern
worldwide. A data book on automotive particulate matter (PM) reduction published by
the National Assembly of the Republic of Korea indicates that diesel vehicles account
for 29 percent of the total PM emissions in the Seoul Metropolitan Area, followed by
construction equipment (accounting for 22 percent). These results signify that diesel engines
are responsible for more than half of PM emissions in the Seoul Metropolitan Area [
1
]. A few
years ago, research studies reported poorer performance of the after-treatment device due to
an increase in the driving mileage of in-use vehicles [
2
,
3
]. Furthermore, concerns are being
raised over air pollution triggered by aged diesel vehicles and construction equipment
without after-treatment devices. Against this backdrop, stronger controls and regulations
are being imposed, as manifested in the following measures. Firstly, government-backed
projects for attaching after-treatment devices, such as the diesel particulate filter (DPF), to
aged diesel vehicles are being pursued. Secondly, retrofit attachment projects of PM-NOX
simultaneous reduction devices for Euro-4 heavy-duty diesel vehicles or those subject to
lower standards are being done. Lastly, maintenance regulations for diesel vehicles are
being enforced [4].
The DPF is a device that prevents PM from being exhausted into the atmosphere
by filtering the matter generated from diesel vehicles, and the substrate inside the DPF
serves as a filter. Once a certain amount of soot is accumulated after being filtered by the
Appl. Sci. 2021, 11, 9483. https://doi.org/10.3390/app11209483 https://www.mdpi.com/journal/applsci
