Coupled 1D-quasi3D fluid dynamic models for the simulation of IC engine intake and exhaust systems

The performances of an internal combustion engine are usually evaluated on the basis of global parameters such as power, torque, fuel consumption, pollutant and acoustic emissions. These depend to some extent on the performances of the single stand-alone components of the engine, but above all are influenced by how the single components are assembled to form the system. For this reason, when engine optimization is performed in a CAE enviroment, the numerical simulation needs to be extended to the entire engine system, comprising cylinders, pipe system, plenums, silencers, aftertreatment devices. The main constraint for an entire engine simulation is the computational burden, therefore suitable modeling approaches have to be adopted in order to balance accuracy and simulation runtime, i.e. introducing suitable simplification in relation with the level of detail required by the analysis [1,2]. In order to simplify the problem, making it possible the simulation of the entire system, the 1D approximation has been traditionally introduced. In this framework, the modeling of the complex shape devices (e.g. air-boxes, plenums, silencers, etc) is addressed resorting to simplified approaches, namely 0D approximation and equivalent 1D pipe schemes [3]. These approaches, although simplified, generally allow, after a process of refinement, calibration and improvement, to build a reliable model of the engine, which can be applied for the investigation of the performance of the engine under different operating conditions and for the optimization of the pipe system.