Experimental investigation of an actively controlled automotive cooling fan using steady air injection in the leakage gap

Abstract

In an axial fan, a leakage flow driven by a pressure gradient between the pressure side and the suction side occurs in the gap between the shroud and the casing. This leakage flow is in the opposite direction to the main flow and is responsible for significant energy dissipation. Therefore, many authors have worked to understand this phenomenon in order to reduce these inherent energy losses. Up to now, most of the studies reported in the literature have been passive solutions. In this paper, an experimental controlling strategy is suggested to reduce the leakage flow rate. To this end, a fan with hollow blades and a specific drive system were designed and built for air injection. Air is injected in the leakage gap at the fan periphery. The experiment was performed for three rotation speeds, five injection rates and two configurations: 16 and 32 injection holes on the fan's circumference. The experimental results of this investigation are presented in this article