Research On The Hydrodynamic Characteristic Of Cvcloidal Propeller And Optimization

The boat industry of our country is developing so rapidly that it needs better propeller badly. While the traditional cycloidal propeller can not satisfy it because of it complex structure and hard manufacture. Additionally, there is a large angular acceleration when it works which is harmful to the propeller and affects the further development. The omnidirectional vertical axis propeller (OVAP) can avoid these problems efficiently because of its simple structure and. unique law of motion. The blades rotate around their respective axis with a constant angular speed which can eliminate the transient shock. However, research on the hydrodynamic characteristic of the OVAP is rarely. This paper studies the hydrodynamic characteristic of the OVAP with the method of numerical simulation and the results show that the OVAP owns excellent hydrodynamic performance and high efficiency.Firstly, numerical calculation has been done based on the structure characteristic and the motion law. According to the results of the numerical calculation, the mathematic model of the OVAP can be gotten. Compared this model with the mechanical analysis of the airfoil under the condition of unsteady flow, the efficiency of the OVAP for the different advance coefficients can be calculated. The results show that the OVAP owns higher efficiency than the cycloidal propeller and the horizontal axis propeller.Secondly, the hydrodynamic characteristic of the OVAP is simulated by structured mesh and sliding grid technique. The contours of velocity and pressure under various time, different revolving speeds and various advance coefficients. The results show that the flow condition is related to the attack angle closely. Meanwhile, the thrust coefficient and the torque coefficient can be gotten from the simulating results. Then the efficiency can be calculated with these two coefficients. The changing trend between the efficiency come from the numerical calculation and the efficiency gotten from the numerical simulation is coincident, which proves the accuracy of the numerical simulation.Thirdly, the cavitation characteristic has been analyzed under various time, revolving speeds and various advance coefficients. The results show the attack angle, revolving speed and advancing coefficient affects the cavitation behavior significantly. At the same time, the process of generation and disappearance of the cavitation will influence the steady of the flow greatly.Finally, research on the structure parameter optimization including the blade amount, the blade shape and the distance between two propellers has been done. Results are as follows:when the blade number increases, the efficiency decreases while the stability of the propeller improves. When the blade shape changes, the efficiency improves firstly and then decreases. The same to the cavitation behavior. When the distance between the two propellers increases, the interaction between the two propellers weakens and the efficiency decreases.