Dynamic thrust of the propeller in oblique flows in continuous conversion mode of tiltrotor

Abstract Tiltrotor exhibits a conversion mode with strong nonlinear aerodynamic characteristics. The thrust characteristics of propellers are one of the crucial factors determining the performance of tiltrotor with electric propulsion systems in the conversion mode, which is affected by multiple factors such as the advance ratio, tilt angle, and wing blocking effect. In the present study, a numerical method based on the overset mesh method is established to simulate the six degrees of freedom motion of real blade models, which is suitable for simulations of the continuous conversion mode of tiltrotor. Numerical simulations are conducted on the continuous tilting process of the propeller/wing system with various propeller advance ratios to analyze the variation and the underlying principles of propeller dynamic thrust, and to summarize the equivalent inflow velocity under different tilt angles during the conversion process. The results show that the propeller thrust increases as the tilt angle increases and the propeller advance ratio decreases. The uneven force on the advancing and retreating blades causes an increase in thrust oscillation amplitude. The advance ratio influences the total thrust by affecting the forward component of the thrust. The resultant force direction angle of the propeller in the conversion mode is 2°–10° greater than the tilt angle, and the difference in angle increases as the propeller advance ratio increases. A new formula for the equivalent inflow velocity of the propeller during the tilting process is summarized. This could help to estimate the dynamic thrust of the propeller in the conversion mode of tiltrotor.