A New Evaluation Method for the Thermodynamic Behavior of Air Intake Systems

At the runner outlets of an air intake manifold for an internal combustion engine, the firing order of the engine and the valve timing are leading to a transient pressure excitation. The resulting pressure waves in the air intake system (inlet manifold and upstream line including air cleaner) have a significant effect on volumetric efficiency. A natural air overcharge - called ram effect - is caused at specific engine rpm that corresponds to a perfect timing between the intake valve closing and the maximum pressure at the intake valve.

This paper presents a new measuring method, used to characterize the dynamic behavior of the air intake system, and to forecast the impact of some of their parameters on volumetric efficiency. A mathematical model of the air intake system was built which is based on the electrical analogy and which uses the well-known results of the resonance RLC circuits. The measuring equipment, specifically developed for this analysis, and used to validate the mathematical model on different cases, is presented in the document.

The potentiality of the presented approach is illustrated in the paper by practical examples of applications, and by correlation made with 1D and 3D simulations.