| Coal separation can effectively remove gangue and sulfur and phosphorus elements in raw coal,which is an important means of energy saving and emission reduction and clean utilization of coal.With the strategic westward movement of China's coal industry,the importance of dry coal preparation for arid and semi-arid coal rich and water deficient mining areas in Northwest China is becoming increasingly obvious.The vibrating flip-flow screen is an important part of the dry coal preparation process.It is widely used in the depulverization of wet fine-grained raw coal.Therefore,its performance and stability directly affect the normal operation of the entire raw coal washing system.Compared with the traditional vibrating screen,due to the complexity and particularity of the structure of the vibrating flip-flow screen,there are long-term problems in actual operation such as poor amplitude stability,difficult to determine the screen surface parameters,and easy damage and heat generation of elastic elements.With the development trend of large-scale and refined coal preparation equipment,the traditional empirical analogy design method can no longer meet the parameter selection and design requirements of the vibrating flip-flow screen.With the development trend of large-scale and fine coal preparation equipment,the traditional empirical analogy design method can not meet the parameter selection and design requirements of vibration flip-flow screen.In order to solve this problem,this paper comprehensively adopts the method of theoretical modeling,simulation analysis and experimental test,focusing on the motion characteristics of flexible screen surface,material parameter inversion,and motion form under complex excitation.From the perspective of dynamics,the modal characteristics of the screen body and the factors affecting the robustness of motion are analyzed;based on the hybrid damping model and the structure-thermodynamic joint simulation,the frequency-amplitude variation characteristics and temperature field distribution of the shear rubber spring are analyzed.The research methods and conclusions provide theoretical support for the dynamic design and optimization of the vibrating flip-flow screen.Based on strain energy theory and Lagrangian functional variational rigidity,a statically indeterminate pressure bar model describing the deflection curve of the fixed-supported screen surface at both ends is proposed.And use the perturbation method to derive the precise expression of screen surface deflection with the amount of screen surface pre-compression.Compared with the field test data of screen surface deflection,it is proved that the proposed statically indeterminate pressure bar model has higher calculation accuracy than the existing calculation model.Based on the model of statically indeterminate pressure bar,the influence of the variation of screen surface length and precompression on the shape of screen surface deflection curve and the maximum deflection of the middle point is analyzed by numerical calculation;through regression analysis,the regression equation of the maximum deflection of the middle point of the screen surface with respect to the length and precompression of the screen surface is established.In order to solve the problem of determining the parameters of the screen surface flexible body modeling under the condition of composite excitation,a method combining the experimental data and optimization algorithm is proposed to identify the mechanical parameters of screen surface materials based on the finite element simulation model.On this basis,combined with the calculation results of the statically indeterminate pressure bar model,the flexible body model which fits the actual initial installation state of the screen surface is established.According to the characteristics of the vibration model,the influence of the vibration parameters,the acceleration and the vibration response of the flexible screen are analyzed.The mathematical model between the deflection,velocity and acceleration of the middle point of the screen surface and the excitation parameters is established,and the accuracy of the model is verified by the model machine test.Aiming at the amplitude stability of the circular vibrating flip-flow screen,considering the influence between the floating screen box and the main screen body,a 6-DOF dynamic model reflecting the plane coupling motion of the circular vibration flip-flow screen is established,and the modal frequencies and mode distributions of the system are calculated.The influence trend and significant degree of the structural parameters on the structural dynamic characteristics are determined through the sensitivity analysis.The elastic mixed damping model is introduced to identify the parameters of dynamic restoring force of shear rubber spring,and the influence of vibration frequency and amplitude on spring restoring force is obtained.Based on the response surface method,the approximate model between the parameters of the elastic mixed damping model and the amplitude and frequency is constructed,and the multi degree of freedom dynamic equation including nonlinear restoring force is constructed,and a combined method of genetic algorithm and state space method is proposed to solve the problem.The accuracy of the model results is verified by vibration test.On the basis of measuring the loss curve and excitation load of rubber shear spring,the stress distribution and temperature field distribution of rubber shear spring under different frequency amplitude conditions were obtained by using the coupling analysis method of finite element statics and thermodynamics.The failure path and internal temperature rise law of shear rubber spring are analyzed.This paper contains 108 figures,42 tables and 158 references. |
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