| At present,the online dynamic balancing of machine tool spindles generally adopts the indirect online dynamic balancing method of adding a balance head,which uses the compensation unbalance force provided by the balance head to offset the centrifugal force of the spindle.However,existing online dynamic balancing devices generally have problems such as complex structure,poor matching,and long-term deformation of the balancing device.Therefore,on the premise of meeting sufficient balance accuracy,reduce the influence of the balance device on the balance accuracy due to its own deformation or temperature and other external conditions,reduce the problem of inconcise installation and disassembly due to complex structure,and maximize the balance device to meet a variety of machine tools.And a wider speed range is the future development direction of online dynamic balancing technology.This thesis uses the principle that the blade will generate a pressure difference due to the incoming flow speed at a fixed pitch angle and thus generate a driving force.A blade balancing method is proposed,that is,the blade is generated due to different speeds and pitch angles during the synchronous rotation of the blade with the main shaft The pressure difference counteracts the unbalanced spindle force.The main contents are as follows:(1)Establish a single-degree-of-freedom damped vibration model of the main shaft,analyze its amplitude and phase characteristics during the movement,and establish a foundation for the blade dynamic balancing method;according to the speed and change of the main shaft of the balanced blade,the synchronous movement of the balanced blade with the main shaft is clarified The mechanism and characteristics of on-line dynamic balancing are carried out;then the blade characteristics of different profiles are analyzed.Considering that the blade pressure and the aerodynamic center position not only affect its aerodynamic efficiency,the assembly and installation of the balancing head also affects the balancing ability,so it is determined that It is an excellent blade profile;finally,by combining with the influence coefficient method,the advantages of the method of using blades for dynamic balancing in line dynamic balancing are clarified.(2)Through CFD technology,analyze the stability of the aerodynamic characteristics of low Reynolds number blades and the driving force generated.Using the blade thickness as a variable,the thrusts of the four common blade profiles at different rotation speeds and elevation angles are numerically calculated and the relationship and law are established.The aerodynamic efficiency of the four blades was evaluated by the change curve of the thrust resistance ratio,and the thrust and resistance ratio curves of the four blades were compared.Finally,the excellent blade profile NACA0012 that can provide a larger range of propulsion change and does not change with the rotation speed was determined.(3)Based on the cloud map of the airflow around the blade,by analyzing the pressure and velocity distribution of the NACA0012 blade at different elevation angles,comparative analysis of the blade's thrust characteristics and efficiency due to changes in the airflow around the blade under different aerodynamic conditions The reason for the difference is to avoid the uneven airflow distribution affecting the performance of the balanced blade and to initially determine the working attitude of the balanced blade at the best performance;then by analyzing the correlation between the pressure center distribution and the aerodynamic center,the NACA0012 line blade is determined at 7° Excellent aerodynamic performance at elevation angle.Finally,considering the influence of temperature,the maximum temperature range around the blade under normal temperature is used as the changing condition,and the lift resistance coefficient and pressure distribution under different temperature differences are analyzed.The changes have well verified that the change of normal temperature hardly affects the balance performance of the blade..(4)For the working conditions such as the speed and deformation of the blade in actual operation,the simulation is mainly verified by the fluid-solid coupling method: a two-degree-of-freedom pitch model is established,and its flutter stall is calculated by the quasi-steady flow field,and the blade Verification of the degree of convergence at different speeds;comprehensively considering a larger elevation angle and moving speed,taking the optimal elevation angle of 7° as an example,the stress of the blade during the motion process is analyzed by the fluid-structure coupling method,and the stress distribution is generally uniform,The maximum deformation is smaller. |
PDF Full Text Request