Filho, F., Teixeira, A., Baêta, J., Guzzo, M. et al., "Stratified Torch Ignition Engine: NOx Emissions," SAE Technical Paper 2016-36-0387, 2016, doi:10.4271/2016-36-0387.
The emission of nitric oxide (NOx) is the most difficult to limit among numerous harmful exhaust gas components. The NOX emission of internal combustion engines is mainly NO, but it will be oxidized into NO2 quickly after entering the air. NO is formed inside the combustion chamber in post-flame combustion by the oxidation of nitrogen from the air in conditions that are dependent on the chemical composition of the mixture, temperature and pressure. The correlation between NO emissions and temperature in the combustion chamber is a result of the endothermic nature of these reactions and can be described by extended Zeldovich Mechanism. The stratified torch ignition engine is able to run with lean mixture and low cyclic variability. Due to lean operation, the in-cylinder temperature of the STI engine is significantly lower than the conventional spark ignited one. This fact lead to a substantial reduction in NOx specific emission. In this work the engine out-emissions of NOx, of the STI engine is presented and a detailed analysis supported by the combustion parameters is conducted. The results obtained in this work show a significant decrease in the specific emissions of NOx of the STI engine in comparison with the baseline engine.