Experimental investigation of active control by steady air injection in the tip clearance gap of an axial fan

摘要

In an axial fan, a leakage flow driven by the pressure gradient between the pressure side and suction side occurs in the tip clearance gap. This secondary flow is in opposite direction to the working flow and is responsible for important energy dissipations. Therefore, many authors have worked to understand this phenomenon in order to reduce these inherent energy losses. Up till now, most of the studies reported in literature are passive solutions. In this paper, an experimental controlling strategy is suggested to reduce the secondary flow rate. To this aim, a fan with hollow blades and a specific drive system were designed and built for air injection. Air is injected in the tip clearance gap at the fan periphery. The experiment was performed for 3 rotation speeds, 5 injection rates and 2 configurations: 16 and 32 injection holes at the fan periphery. The experimental results of this investigation are presented in this article.