Ratio of propeller thrust to total thrust of ducted propellers

The design of ducted propellers is much more challenging than that of isolated propellers, as the complexity of the interference between the ductand the propeller makes it difficult to determine the induced velocity at the propeller. In the present study, a momentum model of ducted propellers is established. Based on the model, the ratio of the propeller thrust to the total thrust of ducted propellers, denoted as k, is analyzed, and its relationship with the induced velocity at the propeller is obtained. Furthermore, the variation law of k in the hoveringand forward flight states is revealed by numerical analysis based on Computational Fluid Dynamics (CFD) simulations. For a given duct configuration, the following variation law of k is found: in the hovering state, k hardly varies with the change of the propeller's rotational speed; in the forward flight state, the k valueand the thrust coefficient of the ducted propeller show a linear relationship. The linear relationship is independent of both the rotational speedand the incoming wind velocity, which is very beneficial for establishing an engineering model about the value of k. In addition, the uniform law of k values for ducted propellers with different number of blades is revealed. The present study enriches the theoretical understandings about ducted propellersand has potential values for application in the ducted propeller design.