3D Simulations And Experimental Validation of High EGR - PHCCI Combustion

The present work addresses the possibility to correctly simulate Partial Homogeneous Charge Compression Ignition (PHCCI) combustion, obtained by the application of EGR up to 60% without using detailed kinetic models. In particular, the laminar and turbulent time characteristic model has been analyzed and improved. The study illustrates the prediction capabilities that can be achieved with such an approach.

The paper reports the results obtained from the simulation of a single cylinder research engine and a four-cylinder diesel engine to verify the validity of the proposed method independently of engine geometry and configuration. All numerical results are compared with experimental pressure traces and rates of heat release, as well as with NO_x and soot emissions over a wide range of operating conditions. With the modified characteristic time model, realistic simulations of engine combustion up to EGR values of about 60% have been obtained for both engines. In particular, simulations quantitatively predicted the reduction of the in-cylinder peak pressure and NO emissions as well as the increase of soot as the EGR rate was increased.