Model-order reduction for prediction of pressure wave propagation dynamics in the IC engine air path system

The automotive industry is currently striving to adopt efficient procedures for model-based control of advanced IC engine systems. Such procedures require accurate and computationally cheap engine air path models predicting the cylinder charge composition and thermodynamic conditions at intake valve closing. To this extent, this paper presents a modeling approach to predict the pressure and flow in the intake and exhaust port of IC engine air path systems. Instead of operating simplifications on the system geometry, an analytical model-order reduction procedure is applied to characterize the dynamics of the air path system starting from the fundamental conservation laws, namely the nonlinear Euler equations for unsteady compressible flows. As a case study, the proposed approach is applied to the characterization of the intake and exhaust flows in the manifolds of a single-cylinder engine. The results are compared against a validated gasdynamic simulation code considering different spatial discretization length conditions. This allows one to establish a trade-off between accuracy and stability and computation time of the proposed solution method.