Integrated 1D-MultiD Fluid Dynamic Models for the Simulation of I.C.E. Intake and Exhaust Systems

This work describes the development, application and coupling of two different numerical codes, respectively based on a 1D (Gasdyn) and 3D (OpenFOAM) schematization of the geometrical domain. They have been adopted for the prediction of the wave motion inside the intake and the exhaust systems of internal combustion engines. The HLLC Riemann solver has been implemented both in the CFD and the 1D codes to solve the Euler system of equations, in order to operate with the same solver on the different calculation domains. Moreover, the HLLC solver has been applied to treat the boundary conditions at the interface between the two domains, in such a way to allow the propagation of flow disuniformities through the domain interface, without affecting the solution accuracy. The hybrid approach was used for the simulation of two different test cases: a complex 5 into 1 pipe junction of a high performance V10 engine and a Venturi tube plus a Helmholtz resonator of a single cylinder S.I. engine. Different engine operating points have been simulated at full load, covering a revolution speed range typical of these engines. The results have been compared to experimental measurements and to complete 1D simulations of the same geometries, pointing out that the hybrid approach is capable of giving a better prediction of the wave motion when the geometry is characterized by highly three-dimensional shapes.