Effect of disk angle-of-attack on aerodynamic performance of small propellers

The aerodynamic performance of four 12-inch diameter propellers was investigated at propeller disk angles-of-attack ranging from 0° to 90° and at advance ratios ranging from 0 to 0.55. Aerodynamic load measurements using a six-axis load cell showed that the thrust of all four propellers increased with an increasing disk angle-of-attack, for all the advance ratios investigated. On the other hand, power consumption demonstrated lower sensitivity to variations in the propeller angle-of-attack. The load difference between the advancing and retreating blades caused pitch and yaw moments, which increased with an increasing propeller angle-of-attack. When plotted as a function of the inflow advance ratio, the thrust, power and propulsive efficiency plots overlapped for the range of disk angle-of-attacks. Analytical prediction of the performance of the rotor was carried out using blade element theory. Comparisons of the experimental data acquired and the predictions using different inflow models was made. The evaluation showed that the Glauert [15] and Coleman et al. [16] inflow models are capable of predicting propeller performance at a wide range of non-zero disk angle-of-attack with maximum discrepancy of 15%.