Research On Cutting Performance Of Shearer Drum And Cutting System Dynamics

The shearer is the main equipment for mechanization coal mining, and it is widely used for coal mining under different geological conditions due to its high production, high efficiency and better suitability. And the cutting performance of the shearer has an importance significant for the reliability, the running stability, the excavating productivity and the enterprise economic efficiency. With regard to this, the theoretical analysis, simulation and experiment are combined to investigate the cutting performance of shearer drum and dynamic characteristic of the cutting system in this thesis.Based on the similarity theory and according to the shearer cutting theory, the similarity criterions for the coal characteristic, the drum, the pick and the cutting load are built. And the cutting test-bed of coal & rock, ten types of picks and drums are developed. Simultaneously, the analogy coal wall for cutting test is developed by considering the compressive strength and density of the coal, and taking the joint and stratification of the coal as the foundation for making the coal wall. The relationship between the compressive strength of coal and the ratio of fine coal and cement is researched by testing; the result indicates that along with the increasing of the ratio, the compressive strength decreases with a exponential form.Utilizing the experiment as research method and making the analogy coal wall of uniform property and with coal-rock interface as cutting object, the influence of the coal characteristic, pick structure parameters and drum structure parameters on the drum cutting torque, cutting specific consumption and lump coal percentage are investigated, and the relationship expression and variation laws are acquired. The results indicate that the drum cutting torque, cutting specific consumption and lump coal percentage have a exponent relation with a majority of correlation parameters. The cutting torque increment has a linear relation with the gangue thickness and compressive strength difference value of coal, and it increases along with them.According to the experiment data and taking the wavelet theory as guidance, the wavelet analysis and power spectrum analysis are conducted for the cutting load, the detail wave of the load change and the change trend of load along with the coal characteristic change are obtained. And the influence laws of the coal-rock interface form on the cutting system frequency are acquired, too. But, the change trends of the power spectrums are all the same, there are not obvious main frequencies to appear, the frequency spectrum analysis can't availably recognize for the load spectrum, indicating that the cutting process is a typical aperiodic phenomenon.The load variation is described by utilizing catastrophe theory, and based on the built constitutive model of catastrophe and dynamic model, the cusp catastrophic model of the drum cutting coal is established, and the rigidity and energy conditions are acquired for the shearer cutting availably. The researches indicate that the rigidity of the shearer haulage system should be smaller than the resistance cutting rigidity of coal, otherwise the cutting part of shearer will vibrate strongly, and the drum and transmission part will be damaged. Simultaneously, the energy release rate of the cutting drum should be bigger than the needed energy for coal broken, otherwise the drum stall will appear, even the drum damaged.Based on the fractal theory, the characteristic factor model of cutting load is established, and the inherence properties included in the cutting load are analyzed. And the phenomenon that the cutting loads have different cutting characteristic factor in different cutting conditions is discovered, providing an available parameter to distinguish different cutting process. And the cutting characteristic factor decreases along with the increase of gangue thickness and coal compressive strength. At the same time, the fractal model of cutting lump distribution is established, and the relationships between the lump distribution and the pick, the drum, the coal characteristic and the cutting depth are investigated. The conclusion that the cutting lump distribution of coal has fractal characteristic is acquired, and the reasons that there are fractal characteristics for the cutting load is found, and indicate that the energy release is stratified in the drum cutting process.On the bases of the chaos theory, the dynamic characteristic of cutting coal system is explored, and taking the phenomenon that cutting load has nondeterminacy which is its outward behave as a chaos phenomenon of a determinacy dynamic system, the inherence essence laws included in the external phenomenon which are disorder, nondeterminacy and nonperiodicity are revealed. The conclusion that the cutting load is not random noise, moreover has chaos characteristic, which should be described with determinacy model, is obtained by investigating the Lyapunov exponent spectrum and the maximum Lyapunov exponent under different cutting conditions. Based on this, the chaos model of the drum cutting coal system is established, and the curve for simulating the cutting load variation is acquired through changing the chaos factor value, which provides a new method for researching the dynamic characteristic of the drum cutting system.