Investigation of post-oxidation mechanism on emissions and turbo performance in a DISI engine

Highlights: • Influence of ignition and injection timing on post-oxidation were characterized. • Retarding of spark timing leads to better post-oxidation phenomena. • Retarding of spark and advance of injection timing shows better emissions and turbo-lag. • Further injection advancing leads to fuel losses with scavenged air. • Thermal efficiency shows reverse effect due to fuel losses in scavenging phenomena. A detailed investigation of ignition and injection timing influence on post-oxidation phenomenon which in-turn can improve turbo-performance along with the emissions of a turbocharged (SI) engine. In this research a novel methodology by adopting the scavenging-based post-oxidation phenomenon was investigated. Firstly, 1-D simulation model was developed, and the model was validated with the experimental results. Then, the simulation was used for the investigation of ignition and injection timing influence on post-oxidation. Thereafter, experimental tests for the post-oxidation were conducted. From the results, it can be stated that the retard of ignition timing shifts the combustion phase towards late which increased the exhaust pressure and temperature. This could increase the chances of the actuation of the post-oxidation reaction in the exhaust manifold. Moreover, it was also found that the injection of fuel during the overlap phase and after overlap had significant influence on the post-oxidation process. Fuel injection during the overlap can increase the possibility of scavenging a fraction of fuel and promote post-oxidation reaction. In both cases, it was found that the emissions and turbo-performance become better at late spark and early injection timing due to oxidation reaction. However, thermal efficiency was affected which will be optimized in the future.