Numerical Study and Analysis of Pollutant Production and Emission Control Using Ion Current Prediction in the SI Engine

A novel chemical non-equilibrium model and computer code for the calculation of the combustion and ionization in the cylinder of Spark Ignition (SI) gasoline engine were developed and presented at SAE 2002 World Congress. It was the only model which gave the chance to predict two peaks of ion current as a result of chemical and thermal ionization of combustion products.

Chemical non-equilibrium approach, detailed modeling of combustion and flame front propagation, the possibility to predict very small concentrations of combustion products (molar fraction down to 10 ^{- 28}) including ions and electrons and independence from quantity and type of substances and chemical reactions provided the universal and powerful tool for the numerical investigation of sophisticated processes occurred during the working (power) stroke.

New investigation were focused on following items:

• the adaptation of the above mentioned model and software to the different geometry of SI engines;
• adaptation of the general model of combustion and ionization for the natural gas engines;
• investigation of the correlation between operational parameters of engine and ion current;
• investigation of influence of operational parameters of gasoline and natural gas SI engines on the emission;
• search the correlation between NO emission and ion current to provide NO emission control and reducing using ion current measuring and prediction.

As a result, the improved model was developed which gives the chance to analyze the operation parameters behavior both for gasoline and natural gas engines with different engine geometry, air/fuel ratio and operational regimes. The strong influence and controlling role of chemical non-equilibrium in the pollutants production both for natural gas engine and for gasoline was demonstrated. Novel results of the engine operational parameters influence on the NO production were obtained. The correlation between ion current and NO production both for gasoline and natural gas engines was illuminated in the wide range of engine operational regimes. Special investigation have been fulfilled to provide NO production control and decreasing for natural gas engines in the course of engine operation. The results of numerical study were confirmed by experimental data.