In-Cylinder Flow Analysis of the Mercedes-Benz do Brasil Lean Burn CNG M366LAG Engine

A computational fluid dynamics (CFD) analysis of the M366LAG in-cylinder flow was performed to explain what are the reasons for the measured engine slower combustion which results from the replacement of the intake valve seat angle of 45° by 20°.

Simulations showed that a quite different in-cylinder flow resulted from the different designs. The 20° geometry was found to generate a weaker turbulent field at the end of the compression stroke, specially around spark plug, which was identified as the cause of the slower combustion. The weaker turbulence is a result of a less coherent flow structure which is less capable of both storing the main flow kinetic energy until the compression stroke end and of taking advantage of squish to generate turbulence.