【作者】 刘送永；

【导师】 杜长龙；

【作者基本信息】 中国矿业大学 ， 机械设计及理论， 2009， 博士

【摘要】 滚筒式采煤机是机械化采煤的主要设备,具有高产高效、适应性强的优点,被广泛应用于不同地质条件下的煤炭开采,其截割性能的优劣对于整机的可靠性、运行稳定性、采煤生产率以及企业的经济效益具有重要意义。为此,本论文采用理论分析、仿真和试验相结合的方法,对滚筒采煤机滚筒截割性能及截割系统动力学特性进行了研究。本论文以相似理论为基础,以采煤机截煤理论为依据,通过建立煤岩性质、滚筒、截齿以及截割载荷的相似准则,研制了煤岩截割试验台、10种截齿和10种滚筒。同时,在考虑煤岩抗压强度、密度的基础上,将煤岩的节理、层理特性作为配置模拟煤壁的依据,研制了试验用模拟煤壁,并通过试验研究了其抗压强度与粉煤和水泥比值间的关系,研究表明,随着粉煤与水泥的比值增大,煤壁抗压强度成指数关系减小。以试验为研究方法,以均质模拟煤层和含有煤岩界面模拟煤层为截割对象,研究了煤岩性质、截齿结构参数、滚筒结构参数以及截割运动参数对滚筒截割扭矩、截割比能耗、块煤率的影响,并得到了相关参数间的关系表达式和变化规律。研究结果表明,滚筒截割扭矩、截割比能耗和块煤率与大部分相关参数成指数形式变化;截割扭矩增量随煤层中夹矸厚度、构成煤岩界面两种煤岩抗压强度的差值的增加成线性关系增大。以试验数据为依据,以小波理论为指导,对截割载荷进行了小波分析和功率谱分析,得到了载荷变化的细节波形及其随煤岩性质不同的变化趋势;同时,也获得了煤岩界面形式对系统频率的影响规律。但是,所有功率谱的变化趋势基本相同,除了滚筒旋转的基频和倍频之外,并无其它明显主频出现,发现频谱分析不能对载荷谱进行有效识别,表明截割载荷是一种非周期信号。利用突变理论描述滚筒截煤过程的载荷变化,在建立滚筒截割煤岩本构模型和动力学模型的基础上,建立了滚筒截割煤岩的尖点突变模型,并得到了采煤机有效截割煤岩的刚度条件和能量条件。研究表明,采煤机牵引系统的刚度必须小于煤岩的阻侵刚度,否则将引起采煤机截割部的强烈振动,导致滚筒、传动部分的损坏;同时,滚筒的能量释放率必须大于煤岩破碎所需能量,否则滚筒将出现堵转,甚至损坏。基于分形理论,建立了截割载荷的特征因子模型,并分析了截割载荷中所蕴含的固有特性。通过研究发现,不同截割条件下的载荷具有明显的不同截割特征因子,提供了一种对不同截割过程、不同煤岩性质的有效识别参数。并且,随着煤层夹矸厚度和构成煤岩界面的两种煤岩抗压强度差值的增大,截割特征因子减小。同时,基于分形理论建立了煤截割块度分布的分形模型,研究了块度分布规律与截齿、滚筒、煤岩性质、切削厚度的关系,得出了煤的截割块度分布具有分形特征的结论,找到了采煤机截割载荷具有分形特性的原因,并说明滚筒截割过程能量释放是层次性。以混沌理论为依据,探索滚筒截割煤岩系统的动力学特性,将具有不确定性的载荷外在表现看作是某一确定性动力系统的混沌现象,揭示滚筒截割载荷的无规律性、不确定性、非周期性等外在现象所蕴藏的内在本质规律。通过研究不同截割条件下载荷的Lyapunov指数谱和最大Lyapunov指数,证明采煤机滚筒的截割载荷不是随机信号,而具有混沌特性,应以确定性模型对其进行描述。在此基础上,建立了滚筒截割煤岩系统的混沌模型,并通过改变混沌因子的值,初步得到了可以模拟试验载荷变化特征的曲线,为研究滚筒截割系统的动力学特性提供了一种新的方法。更多还原

【Abstract】 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.更多还原