Unsteady Pressure Measurements around Rotor of an Axial Flow Fan under Stable and Unstable Operating Conditions

Abstract

This study presents some measurement results on the unsteady pressure fields around rotor under stable and unstable operating conditions of an axial flow fan. The unsteady static pressure of rotor passage was measured by using high frequency pressure transducers mounted on the casing wall. The measurements on the unsteady total pressure at rotor inlet and outlet were also conducted with specially designed high frequency total pressure probe. Double Phase-Locked Ensemble Averaging Technique was used for analysis of pressure fluctuations around the rotor at rotating stall onset point. From the results, the unsteady pressure fields during stable and unstable operations of the axial fan were investigated and compared with each other. Particularly one period of rotating stall could be divided into two regions, stalled flow and unstalled flow region respectively. Furthermore the former could be also classified into two zones, bubbled and disturbed region by their features. The flow characteristics for each zone were described in detail and the static and total pressure fields were also analyzed in terms of the pressure distribution along pressure side and suction side on the blade tip profile.

Numerical Simulation and Analysis of Three Dimensional Flow Field of a Counter-Rotating Fan with Various Angles

“…When the operating point reaches the left of point B which is the highest point of the curve, the outlet pressure and the air volume lose correspondence, and the fan becomes unstable, it will lead to the counter-rotating fan's surge phenomenon and reduce equipment operation safety. Meanwhile, considering the grid voltage fluctuation may cause the speed decrease, thus we require the pressure in the operating point must not exceed the 90% of the maximum static pressure [14][15]. In addition, the Figure 12 also shows that the counter-rotating fan's stable operating zones are different in different setting angles.…”