The Research Of Rotor Blade Tip Shape Effect On The Flow Characteristics

The rotor tip shape is one of the key constraints to improve the helicopter flight speed,so the optimization design of the blade tip is an important issue in the field of helicopter computational fluid dynamics.The Navier-Stokes equtions are sovled by RANS method,using moving overset grid.The influence of backward-swept,taper and anhedral on aerodynamic characteristics in hover are studied and the change rules is analyzed by using this computational fluid dynamics method.The main research work of this paper is as follows:Firstly,the research background of configurations of the tip have been discussed,the numerical simulation methods of helicopter rotor flow field and the research status of new blade tips have been summarized,and the necessity of optimum design of propeller tip has been pointed out.The numerical simulation methods of this paper are introduced in the second chapter.The moving nested grid is used to solve the Reynolds averaged N-S equations,and the flow characteristics of the rotor blade in hover is obtained.Then the effects of different turbulence models on the simulation results have been analyzed and the numerical simulation method has been determined by comparing with the experimental results.In the third,fourth,fifth chapter,the influence of the parameters such as backward-swept,taper and anhedral are studied.The characteristic parameters,including the pressure coefficient,drag coefficient,hovering efficiency and so on,are investigated.And the influence of the different blade tips including deformation starting position and sweep angle/ taper ratio/ anhedral angle on the rotor flow characteristics have been analyzed.From these analyses,the conclusions about how the tip shape parameters affect the blade surface air loading are drawn.In the sixth chapter,the basic tip shapes which can improve the flow characteristics were chosen based on the influence regular pattern of the tip shape variation above,and four kinds of combined blade tip blades were designed.Then the variation of flow characteristics before and after the optimal design of the blade tip shape is analyzed by numerical simulation.At last,this paper summarizes the influence regular pattern of different tip shape of the rotor flowfield.Some tip shape optimization design methods are put forward to further reduce the helicopter speed limit,and to provide important technical support and foundation to improve the performance of helicopter.