Numerical simulation of intake and compression flow in a four-valve pent-roof spark ignition engine and validation with LDV data

Abstract

The intake and compression flows in a motoring four-valve pent-roof spark ignition engine are calculated and compared with the laser Doppler velocimetry (LDV) data. A simple valve treatment technique is used to avoid excessive difficulty in generation of a body-fitted grid for multiple moving valves. A constant-pressure boundary condition is applied at the intake port inlet. Results show good agreement for the fluctuation velocity, while there is some discrepancy in the mean velocity owing to uncertainty in the inlet boundary condition. The tumble ratio and the average fluctuation velocity remain approximately constant or rise slightly owing to the spin-up phenomenon near top dead centre (TDC) after rapid decay of the strong intake flow and turbulence in the compression stroke.