Particulate Emission Control in Gasoline Direct Injection Engines

Gasoline direct injection (GDI) engines have become prevalent in modern light-duty vehicles owing to their improved thermodynamic efficiency and lower fuel consumption compared with port-fuel-injection systems. However, the high-pressure injection of liquid fuel directly into the combustion chamber can create locally rich zones, incomplete vaporisation and wall impingement, which promote soot formation and ultrafine particulate emissions. These particles, typically comprising carbonaceous cores with adsorbed hydrocarbons and trace metals, pose health risks and contribute to atmospheric pollution. In response, regulatory regimes such as Euro 6d-Temp and Real Driving Emissions (RDE) standards now impose strict limits on particulate number (PN) emissions from GDI vehicles. Engine-based strategies to reduce particulate formation include optimised multi-pulse injection timing, elevated injection pressures, cooled exhaust gas recirculation (EGR) and lean-burn concepts to improve mixture homogeneity and lower flame temperatures. After-treatment solutions have evolved from advanced three-way catalysts (TWCs) tailored for reduced PM slip to dedicated gasoline particulate filters (GPFs) employing wall-flow or porous metallic substrates. These filters can achieve over 90 % removal of solid soot and nucleation-mode particles under certification cycles. Ongoing developments in catalyst formulations, substrate geometries and filter regeneration strategies aim to sustain high filtration efficiency across cold starts, transient loads and extended service life, thereby aligning GDI performance with future low-emission mandates.

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Particulate Emission Control in Gasoline Direct Injection Engines publication trend

The graph below shows the total number of articles in particulate emission control in gasoline direct injection engines across all publications each year (not limited to Nature Index journals).

Technical terms

Gasoline Direct Injection (GDI): An engine design in which fuel is injected at high pressure directly into the combustion chamber to enhance efficiency.

Particulate Matter (PM): Solid or liquid particles suspended in exhaust gases, varying in size from ultrafine (<100 nm) to coarse (>2.5 µm).

Particle Number (PN): A metric quantifying the number of particles emitted per unit distance or work, used to regulate ultrafine emissions.

Gasoline Particulate Filter (GPF): An after-treatment device featuring porous substrates that trap solid soot and nucleation-mode particles from GDI exhaust.

Exhaust Gas Recirculation (EGR): A technique that recirculates a portion of exhaust gases back into the intake to reduce peak combustion temperatures and minimise soot formation.

Ultrafine Particles (UFP): Particles with diameters below 100 nm, associated with deep lung penetration and adverse health effects.

References

1. A Review of Particulate Number (PN) Emissions from Gasoline Direct Injection (GDI) Engines and Their Control Techniques. Energies (2018).
2. European Regulatory Framework and Particulate Matter Emissions of Gasoline Light-Duty Vehicles: A Review. Catalysts (2019).
3. Influence of Three-Way Catalyst on Gaseous and Particulate Matter Emissions During Gasoline Direct Injection Engine Cold-start. Johnson Matthey Technology Review (2017).
4. Laboratory and On-road Evaluation of a GPF-equipped Gasoline Vehicle. Catalysts (2019).
5. Particle Number Emissions of a Euro 6d-Temp Gasoline Vehicle under Extreme Temperatures and Driving Conditions. Catalysts (2021).