Numerical Simulation of Unsteady Flow in Engine Intake Manifolds

The objective of this paper is to present a numerical simulation method for the calculation of an unsteady, one-dimensional flow and heat transfer in the branched intake manifolds of multi-cylinder engines. The method operates on the one-dimensional differential conservation equations for a variable-area duct network with friction and heat transfer at the walls. The latter processes are represented by appropriate drag and heat transfer coefficient correlations, as also are the losses which occur at junctions and other geometrical irregularities. The equations are solved by a time-marching finite-volume method, on a computational mesh in which the velocities are located between the pressures which drive them. The main novelty of the approach is the use of an efficient non-iterative implicit solution algorithm which allows the size of the computational time step to be controlled solely by accuracy, rather than numerical stability, considerations, in the interests of economy

The method is assessed by application to flow calculations in the intake manifold of a motored four-cylinder engine, for which time-varying velocity data and overall volumetric efficiency information is available, for a range of engine speeds. For this purpose the manifold calculations are coupled with overall conservation equations for the mass, momentum and energy exchanges with each cylinder. Satisfactory agreement is obtained between the measured and calculated