| Disc brake device is the important part of megawatt wind turbine and its characteristic is High speed and heavy load during the braking.Some problems like different degrees of vibration and braking instability have been arisen during brake periods under the different working conditions,such as the initial braking speed,the spring braking force and the friction coefficient between the brake pairs,due to the interaction of the various components for the brake and the influence of heat-generating.Multi-body dynamic model of brake mechanical assembly including brake spring,brake caliper and compensatory mechanism and thermal-mechanical coupling model of the brake are established,and the influence of braking parameters on the dynamic characteristics of the main brake components and braking stability of brake in the actual working condition is studied to find the best braking parameters for reducing vibration and achieving stable braking.The following is the main research content:(1)Based on the theory of multi-body dynamics,a flexible multi-body dynamics model for the mechanical assembly of the megawatt wind turbine disc brake,is built.Some main parts are included in the model besides brake pads and disc,such as brake spring,active brake caliper,passive brake caliper and compensatory mechanism.It is researched that how are the force on the brake pads and dynamic characteristics of the main brake parts influenced by the different brake parameters,in the background of unstable spring braking force and interaction among components during the braking process.The results show that with the increase about the values of the braking parameters,the extent of variation about the force on brake pads is enlarged,the brake spring force is changed greatly,and the vibration of the main brake components are also exacerbated greatly.(2)Based on the theory of heat-generating by friction in thermal-mechanical coupling,the simplified finite element model,used for megawatt wind turbine disc brake,is established,and the different forces of brake pads are loaded into the model as boundary conditions.The distribution and change with time,concerned temperature field and stress field of the brake,are analyzed.It is researched that how is dynamic characteristics of the brake disc and pads influenced when the brake parameters are different,in the background of unstable spring braking force,interaction among components and heat-generating by friction between brake pair during the braking process.It shows that the vibration of brake pad and brake disc is more intense,with the enlarging of braking parameters.(3)The research method of braking stability for brake is obtained by applying the factors of affecting vibration revealed by the Sperling vibration bench test,such as the change rate of acceleration and vibrant kinetic energy for the vibrant body.The effect of braking parameters on the distribution of brake disc axial acceleration with frequency is analyzed,which is applied to the calculation of brake stability index.The influence of braking parameters on braking stability is studied to find the ways of achieving effective,reliable and stable braking.It shows that the matched initial braking rotational speed and the spring braking force can be set for brake by the brake stability index to achieve the best braking efficiency,when the friction coefficient of the brake pair is determined.In this paper,the dynamic characteristics of the braking process for megawatt wind turbine disc brake are analyzed by the analytic methods of multi-body dynamics and thermal-mechanical coupling,and the influence of the braking parameters on the dynamic characteristics of the brake components is obtained.On that basis,the braking stability analysis is carried out to get the best combinations of brake parameters that reduce vibration and achieve highly efficient braking.It provides a theoretical basis for highly efficient braking of megawatt wind power generation. |
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