Research On Morphing Marine Propeller Based On Smart Material

As one of the most widely used propellers, the screw propeller has significant influence on the performance of marine vehicles. However, the conventional nickel-aluminum-bronze(NAB) screw propellers that are widely utilized are not able to meet the vehicles’ requirements as the marine vehicle techniques develop very fast, thus they need higher-performance propellers to provide thrust. Nowadays, there exist two main methods to improve the propellers’ performance, on the one hand, an improvement should be done to increase the propellers’ performance; on the other hand, a novel propeller should be pursued. Therefore, it is necessary to improve the propeller further or pursue other kinds of propellers. Based on the first method, the thesis comes up with a novel concept of “morphing marine propeller” to improve the performance of the conventional marine propeller to anticipate that the improved propeller can perform well.Based on the piezoelectric stack actuator, a novel morphing screw propeller is designed. Each blade of the propeller including an active rotatable flap(ARF), can change its local camber by rotating the flap. Then a new type of piezoelectric actuator has been selected, and when the actuator generates the displacement, the rotation displacement of the ARF is generated through the transmitting of the transmission mechanism. One set of transmission mechanism is designed to arrange in the propeller blade to push the ARF rotating around its shaft. With regard to the various rotation angles, different local camber will be obtained by the morphing marine propeller(MMP), thus, the marine vehicles can be propelled by different thrusts, which need different torques and therefore different efficiencies can be acquired with various thrusts and torques. The contents of the thesis are as follows:(1) The international and domestic theories on marine propellers, morphing propellers are investigated, especially for the CFD methods to analyze the propellers’ hydrodynamics.(2) The basic theories of CFD method to analyze the propellers ’ hydrodynamic force are expounded, including the three conservation laws, turbulence models as well as their transport equations.(3) The derivation of coordinates transformation equations is performed and programing these equations by FORTRAN language. Then a conventional marine propeller(CMP) with two blades is designed by SOLIDWORKS, and then the ARF can be designed based on the CMP design. For ARF design, the main parameters include its size, shape and position relative to the blade. As to the design of the actuator, the amplifiers to enlarge the displacement of the piezoelectric stack are selected. There exist two schemes to design the amplifier, one is rhombus amplifier and the other is ellipse amplifier. After performing the simulation by utilizing Static Structural module in ANSYS WORKBENCH, we can obtain the amplifying ability of the amplifiers. By comparison, the rhombus amplifier performs better than the ellipse amplifier. Thus, the rhombus amplifier is selected to be the qualified amplifier. When considering the design of the transmission mechanis m, the thesis designs a set of transmission mechanism to transmit the displacement. After arranging the actuator and transmission mechanism, the MMP can be obtained by connecting the ARF. Then a simplified MMP are fabricated by a 3D printer(Maker Bot Replicator 2X), whose material is ABS plastic.(4) Based on the design and simplification, the FLUENT is used to simulate the fluid dynamics around the propeller when the ARF rotates from-5° to +5° as well as the advance coefficient from 0.3 to 0.7 and the rot ation speed of the MMP is 900 rpm. This process is the so-called open water simulation. Through this simulation, various thrusts(thrust coefficients), torques(torque coefficients) and efficiencies can be acquired. Then we can find the disciplines of the M MP, namely, the thrusts(thrust coefficients), torques(torque coefficients) and efficiencies varying trends with the different rotation angles and advanced speeds, so as to provide a foundation to the controlling work.