Study of Diesel Engine Size-Scaling Relationships Based on Turbulence and Chemistry Scales

Engine design is a time consuming process in which many costly experimental tests are usually conducted. With increasing prediction ability of engine simulation tools, engine design aided by CFD software is being given more attention by both industry and academia. It is also of much interest to be able to use design information gained from an existing engine design of one size in the design of engines of other sizes to reduce design time and costs. Therefore it is important to study size-scaling relationships for engines over wide range of operating conditions. This paper presents CFD studies conducted for two production diesel engines - a light-duty GM-Fiat engine (0.5L displacement) and a heavy-duty Caterpillar engine (2.5L displacement). Previously developed scaling arguments, including an equal spray penetration scaling model and an extended, equal flame lift-off length scaling model were employed to explore the parametric scaling connections between the two engines. Prior to investigation of the scaling relations based on turbulence and chemistry timescales, several issues had to be addressed for the present CFD study of engine scaling. The research offers insights on the scaling rules for engines of different sizes over broad engine operating regimes and will benefit the engine design process and provide guidelines for meeting future emission regulations.