Analysis and Modeling of Plain Open Ends and Bends Inside the Piping Systems of Internal Combustion Engines

Abstract

Controlling the pressure wave propagation inside the inlet and exhaust systems of internal combustion engines is essential for the optimization of the cylinder filling and emptying as well as the combustion process. In this objective, the authors have been developing a new one-dimensional simulation code for several years. This paper presents an investigation of plain open end boundary conditions and bend elements. First, the pressure waves at the pipe inlet are analyzed with the Fluent CFD code. It appears that the losses can be modeled with the use of a coefficient that depends on the Mach number as well as the ratio between the pipe diameter and thickness. Then, the paper focuses on the modeling of bends. The losses in this type of elements can be modeled by the addition of a friction factor in the gas dynamics equations. This factor depends on the bend angle and the ratio between the tube radius of curvature and diameter. Finally, an experimental study aimed at evaluating the accuracy of the 1D simulation code is presented. The code enhancements significantly improve flow calculations and allow for the optimization of the inlet and exhaust systems of internal combustion engines.