Abstract
Based on experimental investigation on a car engine, it was established the relationship between airflow rate and pressure drop along the intake duct versus valve lift. To have an evaluation of charge efficiency, i.e. the theoretical and maximum potential flow of inlet duct during the suction stroke, a model considering the influence of inlet valve through area and came profile and inlet duct geometry was developed. A first method for estimation of charge parameters considers inlet duct and cylinder as two control volumes. The flow between the two control volumes is a function of flow characteristics through the inlet valve, experimental determined, assuming in each computation step the steady flow through the pipe. A second method assumes the unsteady flow through the duct and takes into account the pipe junctions for each cylinder and flow dynamics including the throttle. A two-step hybrid finite difference scheme was used to solve the differential system equations describing the specific processes.
During engine tests the conditions considered in the assumptions seemed justified by reasonably good agreement with some quantities and qualitative data. Therefore the outcome of presented research was not only the improvement of engine performances but also the finding of a correlation between theoretical and experimental results.