A CFD (computational fluid dynamics) study on the effects of operating an engine with low intake valve lift at idle corresponding speed
Résumé
Reducing fuel consumption is a prime objective in order to meet regulatory and customer demands. Given this context, an original port fuel injected engine featuring variable valve actuation was initially investigated when operating at idle with low intake valve lift. An improvement of both fuel economy and engine cycle-to-cycle variability was recorded at idle operation, which is a prominent feature of real world driving, especially in congested city traffic. To complete the picture, however, results concerning the engine's internal aerodynamics are necessary. In the present study, the internal aerodynamics and gas exchange phenomena of the engine are examined when using low intake valve lift. For this purpose, a 3D CFD (computational fluid dynamics) dynamic simulation of the motored engine at a speed corresponding to idle operation has been adopted. Experimentation was also performed to obtain data to set the initial and boundary conditions and to calibrate and validate the CFD model. The results provide important insights into the effects of operating the engine with low intake valve lift: increased flow velocity, turbulence and swirl intensity and reduction of internal EGR (exhaust gas recirculation). Thus, this CFD study confirmed our previous work recorded phenomena mentioned as the cause of the engine's idle operation improvement.