Unsteady End-wall Pressure Measurements Using Near-field DIY Sensors on Fouled Fan Rotor Blades

Abstract

The fouling is identifiable by the presence of dust on rotor and stator blades, and its main origin, in industrial turbomachinery, is the presence of a film of moist or lubricant driven to the trailing edge by the near-wall flow, or centrifuged toward the casing by impeller rotation. Solid particles pile up on them, leading to eccentricity and load unbalance. The formation of build-up results in performance reduction, and the chance of a deposit detachment while the impeller spun, may cause damages due to the impact on the machine parts.In industrial fans, the presence of fouling influences the characteristic curve and could anticipate stall when the flow rate is throttled. Rotating stall is an aerodynamic instability with a typical frequency about half the rotor frequency, acoustically identifiable from the changes in the emitted rotor noise, due to displacement from the stability. This work investigates rotating stall dynamics on an axial fan with fouled blades. The stall is identified with time-resolved pseudo-sound measurements in the end-wall region using DIY sensors. The signals have been analysed in frequency domain, and time domain using a phase space reconstruction technique. It is demonstrated a modification of the dynamic to stall and are identified diverse stall precursors.