Evaluation through pressure and mass velocity distributions of the linear acoustical description of I. C. engine exhaust systems

Linear acoustic theory is still the most widely used tool for exhaust system design in I. C. engines. In this paper, the pressure and mass velocity distributions along the exhaust system are used to evaluate the results from linear acoustic theory. These results are compared with those obtained from a full non-linear calculation validated against engine test experiments. The analysis performed allows the influence of two relevant aspects to be separated: the linear representation of the source (engine and manifold) and the linear description of the exhaust system itself. The results indicate that good qualitative agreement may be attained in general, but some differences associated with non-linear effects can appear.