Chapter 3 - NOx and PM trade-off in IC engines

Abstract

Harmful pollutants that are released from internal combustion (IC) engines such as nitrogen oxides (NOx) and particulate matter (PM) are extremely detrimental to air quality and human health. In recent years, multiple emission control techniques have been explored to control vehicular emissions during pre-/postcombustion phases in IC engines. The previous chapter highlighted the formation of NOx emissions and the kinetics involved in the process. However, it is important to understand the control aspects of the same due to the complex relationship between NOx and PM emissions. Hence, this chapter mainly focuses on the trade-off between NOx and PM in IC engines. Currently, the most important dispute in the IC engine is the nitrogen oxides and particulate matter trade-off, with a minimum reduction in power and brake-specific fuel consumption. Optimization of combustion properties and in-cylinder control techniques introducing the split injection technique along with other engine input parameters and some other possible techniques are reviewed. Various techniques to solve the issue of reducing NOx and PM simultaneously by oxygenated alternative fuels are discussed along with the limitations and challenges. The optimal trade-off and simultaneous reduction between NOx and PM emissions using various engine input parameters assisted by combustion modes and after-treatment devices are discussed along with the studies incorporating these techniques.