Análise da geometria de coletores de admissão em motores sobrealimentados

Abstract

In an Otto cycle internal combustion engine, several factors influence its performance and energy efficiency. Among them, the intake manifold plays a crucial role, as it is responsible for admitting air and distributing it evenly among the cylinders, while also withstanding both positive and negative pressures relative to atmospheric pressure. In this context, it becomes necessary to study the design of intake manifolds for turbocharged Otto cycle engines, considering fundamental principles of fluid mechanics. This work aims to evaluate the influence of intake manifold geometry on the fluid dynamic performance of Otto cycle engines operating under forced induction. The study was conducted through three-dimensional modeling and numerical simulations using SolidWorks Flow Simulation, based on computational fluid dynamics (CFD) methods. Two different intake manifold geometries were analyzed: the MI model, originally developed for naturally aspirated engines, and the unilateral plenum model, specifically designed for turbocharged applications. The simulations were carried out under typical steady-state operating conditions, with intake pressures up to 3 kgf/cm² and air temperature at 40 °C. Variables such as static pressure, pressure loss, average velocity per cylinder, flow lines and vorticity, mass flow rate per cylinder, and Reynolds number were evaluated. The geometrical parameters considered included plenum volume, duct length, and diameter, in order to understand their influence on internal flow behavior. The results showed that the plenum manifold achieved better performance under high-pressure conditions, offering more balanced airflow distribution and lower relative pressure loss, while the MI manifold provided more uniform flow under moderate load conditions. It is concluded that the choice of manifold geometry must take into account the intended operating regime, as it has a direct impact on volumetric efficiency, air-fuel mixture atomization, and overall engine performance.