EGR Strategies Pertaining to High Pressure and Low Pressure EGR in Heavy Duty CNG Engine to Optimize Exhaust Temperature and NOx Emissions

CNG has proven to be a concrete alternative to gasoline and diesel fuel for sustained mobility. Due to stringent emission norms and sanctions being imposed on diesel fuel vehicles, OEMs have shifted their attention towards natural gas as an efficient and green fuel. Newly implemented BS VI emission norms in India have stressed on the reduction of Nitrogen Oxides (NOx) from the exhaust by almost 85% as compared to BS IV emission norms. Also, Indian Automotive market is fuel economy cautious. This challenges to focus on improving fuel economy but without increase in NOx emissions. Exhaust Gas Recirculation (EGR) has the potential to reduce the NOx emissions by decreasing the in-cylinder temperature. The objective of the paper is to model a CNG TCIC engine using 1D simulation in order to optimize the NOx emissions and maintain exhaust temperatures under failsafe limits. The 1D model is optimized in steady state conditions using the control parameters such as EGR flow rate, power achieved and maximum exhaust temperatures within the boundary conditions. The simulation is carried out using High Pressure (HP) EGR and Low Pressure (LP) EGR design optimization and predictions were made regarding the exhaust gas temperature. This simulation model is validated using actual experimental results and the finalized EGR strategy is used to optimize the NOx emissions.