Impact of EGR and engine speed on HCCI engine performance and tail pipe emissions

Increasing air-to-fuel ratio has been considered as one of the advantages of HCCI combustion. A diluted in-cylinder mixture leads to lower temperatures and therefore lower NO emissions. This improvement is due to a higher trapped residual rate in the cylinder when higher lambda is set. Higher lambda means more air therefore more trapped residual is required to deliver enough energy for auto-ignition. Analysis show that HC, CO in HCCI mode are heavily dependent on engine speed. HC emission was influenced by engine speed more than CO and NO emissions. (C) 2017 The Authors. Published by Elsevier Ltd.