The Principle of Particulate Matter Capture by DPF Substrates in Diesel Vehicles
Briefly introduce the working principle of DPF substrates in capturing particulate matter from diesel vehicles.
The Principle of Particulate Matter Capture by DPF Substrates in Diesel Vehicles
The DPF (Diesel Particulate Filter) captures and periodically burns off carbon particles from exhaust gas through the physical filtration and regeneration mechanisms of a wall-flow honeycomb ceramic substrate, achieving a capture efficiency of over 90%.
Basic Structure of the DPF Substrate
The DPF utilizes a wall-flow honeycomb ceramic structure: adjacent channels are alternately plugged, forcing the exhaust gas to pass through the channel walls, where particulate matter is trapped.
Parameter | Typical Value |
Material | Cordierite (mainstream) or Silicon Carbide |
Cell Density | 200-300cpsi |
Wall Thickness | 0.3-0.5mm |
The Threefold Physical Mechanism of Capture
Mechanism | Particle Size Range | Principle |
Diffusion/Interception | <100nm | Brownian motion causes particles to strike and be trapped by pore walls |
Interception/Straining | 0.1-1μm | Particle size exceeds pore size, causing blockage |
Inertial Impaction | >1μm | High particle inertia causes impact and capture against walls |
The combination of three mechanisms enables the DPF to achieve a capture efficiency of over 90% across the entire particle size range.
Filtration Process and Efficiency
Exhaust enters the inlet → Inlet is blocked → Forced to pass through the channel walls → Particulate matter is trapped → Clean exhaust is discharged
Initial efficiency: 70%–80% (fresh wall surface)
Operational efficiency: >90% (the soot cake layer acts as the filtration medium after formation)
Regeneration: Maintaining capture efficiency
Particulate accumulation → Pressure drop increases → Regeneration required to burn off accumulated carbon:
Regeneration Method | Temperature | Principle |
Passive regeneration | 250-450℃ | Continuous oxidation of carbon particles using NO₂ |
Active regeneration | 550-650℃ | Temperature rise via post-injection of fuel to burn off accumulated carbon |
Key Influencing Factors
Factor | Impact |
Cell density/wall thickness | 300 cpsi + thin walls offer high efficiency but result in higher pressure drop |
Ash accumulation | Engine oil ash is non-combustible; periodic ash removal is required (approx. every 100,000 km) |
Regeneration frequency | Approximately every 500–800 km under urban driving conditions |
Summary
The capture principle of the DPF can be summarized as follows: a wall-flow substrate forces exhaust gas to pass through the walls, where three combined mechanisms—diffusion, interception, and inertial impaction—capture carbon particles across the entire size range with an efficiency exceeding 90%. Filtration efficiency improves further once the soot cake layer forms, while a combination of passive and active regeneration ensures sustained operation. The DPF functions as a "capture-regeneration" cyclic system, with its long-term effectiveness depending on regeneration frequency and ash management.