The pressure fluctuations on the casing wall of two axial flow compressor rotors with various tip clearances have been analyzed by the use of two kinds of correlation functions. The behavior of the pressure fluctuation varies depending on tip clearance and blade solidity. In the case of small tip clearance, the nature of disturbances becomes random as the flow rate is reduced to a stall condition. For moderate tip clearance, coherent-structured disturbances appear intermittently at low flow rate. They appear more frequently as the solidity is increased and the flow rate becomes lower. For large tip clearance, the coherent structured disturbances exist even at considerably higher flow rates. Corresponding to these features, there are peculiar patterns in the correlation designated as “phase-locked correlation functions.”
Improvement of the characteristics of the low-flow-rate region for axial flow fans.
