Numerical Study of Friction and Heat Transfer Influence on Spark Ignition Engine Manifolds

Abstract

A model has been developed in order to analyse the influence of friction and heat transfer between the exhaust gases and the inside wall of the exhaust manifold on spark ignition engine performance. One-dimensional unsteady compressible flow equations are used to describe instantaneous evolution of the flow inside the manifolds. Special attention is paid to friction and convective heat transfer source terms. A high-order total variation diminishing (TVD) scheme is applied to compute a second-order accurate numerical solution of the unsteady flow in engine manifolds. The combustion process in the spark ignition engine cylinder is described by a two-zone thermodynamic model. A series of numerical tests has been carried out. The influence of friction and convective heat transfer between the exhaust flow and the inside wall manifolds has been studied by analysing computed and experimental engine performance curves. Also, the instantaneous pressure at the exhaust manifold has been studied. The manifold pressure predicted by the developed model is successfully compared with experimental data from a spark ignition engine. From these comparisons it has been found that friction and heat transfer in exhaust manifolds play an important role in engine performance. Furthermore, it has been checked that the performance is not very sensitive to which friction factor correlation is chosen, whereas the engine performance is rather dependent on the constant factor set in the heat transfer correlation.