Effect of advance ratio and blade planform on the propeller performance of a high altitude airship

Experimental investigations on the influences of Reynolds number, blade planform and advance ratio on the aerodynamic performance are carried. Different from conventional aircraft propellers, the HAA propellers are characterized by low Reynolds number, large thrust requirement and low advance ratio. At the moment, the theoretical guidance and industrial experience in designing such propellers are still lacked. In the present study, the influence of Reynolds number is firstly studied via tests of a propeller at different rotational speeds. It is found that, for the propeller with airfoil S1223, the influence of Reynolds number is negligible as Re_0.7 >/1.2 × 10⁵ (Re_0.7 =0.7 μn Db^0.7 μp). The tests regarding the influences of blade planform and advance ratio on propeller performance are carried in the condition of Re_0.7 ≥ 1.5 × 10⁵. The results show that, when advance ratio is below 0.8, the blade with narrow tip is favorable to the propulsive efficiency. Hence, it is suggested that the blade with narrow tip should be adopted by the large thrust and small advance ratio HAA propellers. For HAA propellers with advance ratio greater than 0.8, the propulsive efficiency can be benefitted by increasing the blade tip width. Hence, the blade with wide tip is more suitable in this application.