Impact of Exhaust Gas Recirculation (EGR) on the Emission of the Dual-Fuel Diesel Engine with Hydrogen as a Secondary Fuel

Hydrogen is one of the best alternatives for conventional fuels because it is free from carbon. Hydrogen has its own benefits and limitations in its use as a conventional fuel in automotive engine system. However, hydrogen increases the performance along with NO_x formation. One of the methods to reduce NO_x without comprising its performance is addition of exhaust gas recirculation (EGR). In the present investigation, the formation of carbon monoxide (CO), carbon dioxide (CO₂), un-burnt hydrocarbon (HC) and oxides of nitrogen (NO_x) was measured on four-cylinder water-cooled turbocharged direct ignition (DI) compression ignition diesel engine with diesel as a base fuel and hydrogen as a gaseous fuel (0–5%) by using EGR technique (5–10%) at various load conditions. The formation of NO_x gets decreased by 37.82, 48.29 and 75.95% by using 5%, 10% and 15% EGR, respectively, at 40% load conditions as compared with pure diesel operation. Similarly, as the engine runs on dual-fuel modes with 5% substitutions of diesel fuel with hydrogen fuel (H₂), the formation of NO_x gets decreased by 21.16 and 29.90%, at 40% load conditions by using 5 and 10% EGR, respectively, as compared to pure diesel operation. Further, the formation of CO, CO₂ and HC also gets decreased by the addition of 5% EGR in the gaseous–air mixture, while it increases beyond 5% EGR in dual-fuel mode conditions. The maximum quantity of the hydrogen and EGR substitution is limited due to knock in the engine.