Development of semi-empirical soot emission model for a CI engine

Area of Science:

• Combustion Science and Engineering
• Automotive Emissions Control

Background:

• Diesel engines produce harmful soot emissions, primarily during fuel injection.
• Diesel particulate filters (DPFs) capture over 99% of soot, but regeneration reduces fuel economy.
• Real-time soot estimation is crucial for controlling emissions and DPF regeneration under transient conditions.

Purpose of the Study:

• To develop a zero-dimensional, semi-empirical model for estimating engine-out soot emissions in diesel engines.
• To correlate soot formation with fuel-air mixing at the lift-off length and combustion parameters.
• To incorporate the Nagle and Strickland-Constable mechanism for soot oxidation rate calculation.

Main Methods:

• Developed a zero-dimensional engine-out soot estimation model.
• Correlated soot formation with equivalence ratio at lift-off length, injected fuel mass, and combustion duration.
• Integrated the Nagle and Strickland-Constable mechanism for soot oxidation.
• Validated the model against steady-state experimental data and transient Worldwide Harmonized Light Vehicles Test Cycle (WLTC) conditions.

Main Results:

• Achieved an R² of 0.901 and a root mean square error of 10.8 mg/m³ for steady-state conditions.
• Demonstrated approximately 6% accumulated soot error during WLTC validation when combined with an in-cylinder pressure model.
• Showed model effectiveness even without an in-cylinder pressure sensor.

Conclusions:

• The developed zero-dimensional soot model accurately estimates engine-out soot emissions.
• The model can be used for real-time feedback control to minimize soot and optimize DPF regeneration.
• This approach enhances fuel economy and reduces tailpipe emissions in diesel engines.