Numerical Model for Intake System in SI Engine

Abstract

Exploiting acoustic phenomena of gas dynamics means to increase charge density. The acoustic phenomena in the intake system give a supercharging effect and influence the volumetric efficiency of the engine. Helmholtz resonance theory can be exploited to achieve the design of the intake manifold. Intake airflow pressure loss was minimized and tuned for peak airflow at the desired RPM corresponding to maximum torque. The current work involves testing various intake lengths on a SI engine Honda G×100 generally used to power SH×2000 Generator. Also, the effect of air temperature traveling the intake manifold was evaluated. Comparison with experimental results provide empirical verification of computer modeling and confirm the role of reflecting compression and expansion pressure waves as the primary mechanism of intake tuning. An acceptable agreement between numerical and existent experimental results was obtained, especially at low engine speed, which highlight the validity of the theoretical chosen model. This research identifies the optimal intake manifold geometry corresponding to the maximum torque, the optimum length is at 180 mm and the optimum A/L ratio is at 3.7 mm. Additionally, adding 20 ℃ the intake temperature will lead to an increase of the optimal engine speed with about 100 rpm. A three dimensional mesh give a satisfactorily understand of the relationship between optimal intake manifold geometry, intake temperature and engine speed.