AXIAL COMPRESSOR FLOW BEHAVIOR NEAR THE AERODYNAMIC STABILITY LIMIT

In this investigation, casing mounted high frequency response pressure transducers are used to characterize the flow behavior near the aerodynamic stability limit of a low speed single stage axial flow compressor. Time variant pressure measurements are acquired at discrete operating points up to the stall inception point and during the transition to rotating stall, for a length of time no shorter than 900 rotor revolutions. The experimental data is analyzed using multiple techniques in the time and frequency domains. Experimental results have shown an increase in the breakdown of flow periodicity as the flow coefficient is reduced. Below a flow coefficient of 0.40 a two node rotating disturbance develops with a propagation velocity of approximately 23% rotor speed in the direction of rotation. During rotating stall, a single stall cell is present with a propagation velocity of approximately 35% rotor speed. The stall inception events present are indicative of a modal stall inception.