Hidefumi Fujimoto

A study on the formation of vertical vortex in the cylinder of an I.C. engine using CFD: Effect of intake valve closing timing

Air flows in the intake ports and cylinders of a four-valve gasoline engine were numerically analyzed by means of an original CFD code named “GTT”. In this code, the k-e turbulence model was used and the Chakravarthy-Osher 3rd order TVD scheme was applied to the convection terms in all the governing differential equations. The validity of the code was confirmed by comparing the calculated results of the mean velocity and turbulence intensity with the measured ones by means of LDV. Using the present code, the effect of the intake valve closing timing on the formation of vertical vortex in the cylinder of a four-valve engine was investigated. It was found that the turbulence energy in the combustion chamber near compression TDC can be increased by the retardation of intake valve closing timing in the case of intense vertical vortex, because the vertical vortex is intensified by the back flow from the cylinder to the intake ports.

An evaluation method for quality of air–fuel mixture distribution and movement in combustion chamber of DISI engine using CFD

Abstract To evaluate quantitatively CFD calculation results of air–fuel mixture behavior: spatial distribution and movement in a combustion chamber of a direct injection spark ignition (DISI) engine, coefficients of the spray model were optimized and accuracy of local fuel concentration at the spark gap under running engine conditions was obtained, using experimental measurement results of fast flame ionization detector (FID) as a criterion. A statistical method was employed to pick out important factors: mixture evaluation indices, comparing calculated mixture behavior and experimentally measured fuel economy of a single cylinder engine through a multiple regression analysis. The validity of the index was also confirmed.