Influence of Aerodynamic Probes for Measuring Distorted Inflow on the Performance in a High-Speed Axial Flow Fan

Experimental evaluation of aero-engine compressor performance under distorted inflow conditions is clearly specified in airworthiness standards. In such tests, six to eight multi-hole comb pneumatic probes are commonly used to quantify the distortion intensity. However, it is still unclear whether the presence of these probes modifies the downstream distorted flow and, consequently, affects the accuracy and reliability of the performance evaluation. To address this issue, a numerical study was conducted on the distortion intensity with and without inlet measuring pneumatic probes in a two-stage high-speed axial flow fan. The results show that, compared with the case without pneumatic probes, the installation of inlet pneumatic probes increases the inlet total pressure and temperature distortion intensities by 0.011 and 0.0015, respectively. However, the pneumatic probes can act as guide vanes to reduce the swirl angle, it leads to a significant 0.0411 decrease in the swirl distortion intensity. This reduction in swirl distortion further decreases the angle of attack at the rotor blade leading edge and increases the inlet axial velocity, thereby enhancing the flow capacity and improving the corrected flow rate and pressure ratio by 1.09% and 1.56%, respectively. The optimization of the inlet angle of attack reduces flow separation and increases the efficiency by 1.7%. Accounting for the influence of the probes brings the numerical simulation results closer to the experimental data. It demonstrates that the pneumatic probes exert a dual effect on the distorted flow field in practical applications.