Design of automobile devices with reduced flow noise

Abstract

Large eddy simulations (LESs) were performed to appraise unsteady internal flows in the solenoid valve of an anti-lock braking system (ABS) and the centrifugal fans of a belt-driven starter generator (BSG), and the flow-induced noise source were obtained using Lighthill’s acoustic analogy. An optimal design was acquired through qualitative evaluation of the far-field acoustic pressure fluctuations by applying the Ffowcs Williams and Hawkings (FW-H) integral method. The solenoid valve operation was assumed to be linear in an axial direction, and an Overset grid scheme was adopted to realize the plunger motion. In the minutely lifted state of the plunger during the entire process, the strong pressure fluctuations occurred due to the separated upstream flows on the end of plunger convex surface. As the results of such turbulence nature, the fluctuations of the internal flows could be identified as the aurally unpleasant noise. The flow separation, one of the significant causes of the flow-induced noise, were delved and appraised in the perspective of varying the location by geometrical modifications. An optimal plunger design to reduce flow-induced noise was obtained as featuring of a small radius, a non-wounded surface, and a large tip angle. The reduction of flow-induced noise for the centrifugal fan of a BSG was performed with various fan design. The vortex impingement by separated wake flows from precedence blades were main cause of the flow-induced noise. The flow noise was diminished by newly designed blade, such as the satooth on top edges and the step leading edges. The present LES studies were clarified prediction of flow-induced noise under moving boundary conditions, and it could be widely utilized the research base in industrial fields.