NUMERICAL ANALYSIS OF INTERNAL COMBUSTION ENGINE INTAKE NOISE WITH A MOVING PISTON AND A VALVE

Traditionally, intake noise from internal combustion engine has not received much attention compared to exhaust noise. But nowadays, the intake noise is a major contributing factor to automotive passenger compartment noise levels. The main objective of this paper is to identify the mechanism of generation, propagation and radiation of the intake noise. With a simple geometric model, it is found that one of the main noise sources for the intake stroke is the pressure surge, which is a compression wave due to the compressed air near the intake valve after closing. The pressure surge, which has the non-linear acoustic behavior, propagates and radiates with relatively large amplitude. In this paper, unsteady compressible Navier–Stokes equations are employed for the intake stroke of axisymmetric model having a single moving piston and a single moving intake valve. To simulate the periodic motion of the piston and the valve, unsteady deforming mesh algorithm is employed. For the purpose of perfect closing of the intake valve, the numbers of mesh are changed using a Lagrange interpolation. In order to resolve the small amplitude waves at the radiation field, essentially non-oscillatory (ENO) schemes are used. The source of the intake noise can be identified through the visualization of propagation in a finite duct and radiation to the far fields. Comparison with measured data is given for in-duct pressure showing a better agreement than the one-dimensional calculation data.