Folding propeller design and analysis for a hybrid driven underwater glider

This paper designed a folding propulsion module dedicated for a hybrid driven underwater glider (HDUG). The blades of the propulsion module can be folded and unfolded in time when a mission needed. In this paper, the design of the driven device and its hydrodynamic performance analysis are described respectively. we used the spline curves to fit the individual data points, base on which we created a three dimensional solid model of an unfolding propeller having smooth surfaces after drawing the profile shape line based on the coordinate transformation. CFD method was used to calculate the performance of the folding propeller in the viscous flow regions with various blade opening angles from 0 to 90 degrees. The thrust coefficient, torque coefficient and propulsive efficiency of the folding propeller have been simulated under different advance coefficients and different blade opening angles. For the purpose of evaluate the degree of drag decrease, we proposed a conception of drag decrease fraction. We obtained the drag decrease fraction of the whole vehicle reached to 45% compared the blades in folding and unfolding. Finally, we gave a result analysis and discussion and found out that the design of the propulsion module meet the requirements well when the motor speed is greater than 800 revolutions per minute.