Numerical simulation and experimental verification of gasoline intake port design

Hybrid vehicle engines modified for high exhaust gas recirculation (EGR) is a good choice for high efficiency and low NOx emissions. However, high EGR will dilute the engine charge and may cause serious performance problems such as incomplete combustion, torque fluctuation, and engine misfire. An efficient way to overcome these drawbacks is to intensify tumble leading to increased turbulent intensity at the time of ignition. The enhancement of turbulent intensity will increase flame velocity and improve combustion quality, therefore increasing engine tolerance to higher EGR.;It is known that the experimental characterization of the near top dead center flow field in engines is not practical and cost effective in an engine development environment. Instead, CFD is more convenient, more economical, and more versatile to study the in-cylinder flow physics if its accuracy is validated with experimental results. To achieve the goal of increasing tolerance to EGR, this dissertation reports investigations of intake port design simulation.;A CFD based intake port development methodology was developed. It includes preliminary study of hardware and software selection, a systematically validation study of verifying the accuracy of the CFD tool, and finally a transient study as real engine operation condition determining the effectiveness of the optimized shape. A new intake port was designed to demonstrate the methodology. The resulting tumble ratio in the modified intake port has a much larger peak value, about twice the original peak. This indicates that airflow is well organized and the momentum provided by intake port is also well preserved in modified design. In the modified design, the well-preserved tumble breaks up through the end of compression, which will transfer the energy stored as tumble into kinetic turbulence energy. It is found the turbulent kinetic energy in the modified case is twice that of the original version when tumble breaks up, which will greatly improve the combustion quality and increase tolerance to EGR. The developed CFD based methodology was proven with the successfully application in the intake port configuration design.