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Measuring Sub-23 Nanometer Real Driving Particle Number Emissions Using the Portable DownToTen Sampling System
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Particle Number Emissions From Compression Ignition Engines: A Critical Review of Current Understandings
Zheng Fu1,2, Chenyang Fan1, Ze Guan1
1Henan Provincial International Joint Laboratory of Energy Conservation and Pollutant Control of Energy Power Equipment, College of Vehicle and Traffic Engineering, Henan University of Science and Technology, Luoyang 471003, China.
ACS Omega
|January 8, 2026
Summary
Controlling particle number (PN) emissions from compression ignition engines is crucial for reducing urban pollution. Diesel particulate filters (DPFs) show the highest PN reduction, while alternative fuels have inconsistent effects.
Area of Science:
- Environmental Science
- Mechanical Engineering
- Combustion Science
Background:
- Particulate matter (PM) from compression ignition (CI) engines significantly pollutes urban atmospheres, impacting human health and the environment.
- Reducing ultrafine particle emissions, particularly particle number (PN), is a key goal for advancing CI engine technologies.
Purpose of the Study:
- To provide recent updates on the effectiveness of various control strategies for reducing PN emissions from CI engines.
- To analyze the chemical composition, formation mechanisms, and in-cylinder processes influencing PN emissions.
- To compare the efficacy of different technologies for optimizing PN reduction.
Main Methods:
- Review of existing literature on CI engine emissions and control strategies.
- Analysis of in-cylinder technologies (injection, operating conditions, fuel formulation) and their impact on particle size distribution and PN.
- Evaluation of after-treatment systems, including catalysts and diesel particulate filters (DPFs), and their combined effects.
Main Results:
- Diesel particulate filters (DPFs) demonstrated the highest reduction in PN emissions among evaluated technologies.
- The interaction between catalysts and DPF regeneration was found to unexpectedly increase PN emissions.
- Alternative fuels showed variable efficacy in reducing PM and PN emissions, contrary to expectations.
Conclusions:
- DPFs are highly effective for reducing PN emissions from CI engines.
- Further research is needed to understand the inconsistent effects of alternative fuels on PN emissions.
- This review serves as a reference for developing advanced PN reduction technologies and updating emission regulations.
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