基于分形理论的无油润滑涡旋压缩机端面摩擦问题研究

发布时间：2019-01-06 08:19

【摘要】：涡旋压缩机是一种新型高效的容积式压缩机，具有结构紧凑、运行平稳、噪声低等特点，其应用范围目前已从空调制冷向医药、食品、燃料电池等需求无油污染的洁净压缩气体的领域拓展。由于涡旋压缩机特定的运动方式，存在较多摩擦副，其摩擦损耗在很大程度上影响着涡旋压缩机的效率和性能。摩擦副的表面形貌对压缩机的性能和摩擦副相互作用表面间的摩擦、磨损、混合润滑特性及接触刚度等都具有很大的影响。摩擦力和摩擦因数则是反映摩擦副摩擦磨损行为的重要参数，所以，对摩擦副材料初始表面形貌与其摩擦信号相关性的研究，将对零件的加工过程、质量控制以及提高零件的使用性能等具有重要的意义。无油润滑涡旋压缩机摩擦副摩擦特性不仅与压缩机运行工况、负载有关，而且还与摩擦副对偶材料、表面初始特性以及运行过程中摩擦副端面分形特征有关，因此通过对摩擦副端面微观接触和受力分析，建立摩擦力数学模型，预测涡旋压缩机摩擦学系统的摩擦行为，可为压缩机动力学特性分析和理论设计提供参考。本课题基于摩擦学和分形理论，，通过试验对自润滑材料聚醚醚酮PEEK、聚酰亚胺PI、聚醚砜PES与涡旋压缩机常用材料球墨铸铁QT对磨的摩擦性能进行了研究，并选用不同初始表面的PEEK，在触针式表面轮廓仪上对初始表面轮廓进行采集，在JSM-5600LV扫描电子显微镜下观察其表面形貌，在UMT-3MT摩擦试验机上进行PEEK/QT摩擦副试样试验。运用分形理论对表面形貌及摩擦信号进行分形表征，并对PEEK初始表面形貌与其摩擦信号相关性进行研究。在试验的基础上，结合M-B分形模型和滑动摩擦力分形预测模型，依据无油润滑涡旋压缩机的结构、运行方式及受力特点，在分析动静涡旋摩擦副端面微观接触状态及微观接触受力情况的基础上，建立了无油润滑涡旋压缩机动静涡旋端面摩擦副的摩擦力分形预测模型，并通过实例计算，对该模型进行了验证与分析。结果表明，聚醚醚酮初始表面和摩擦信号均具有显著的分形特征；在相同速度，相同初始表面下，摩擦信号的分形维数随着载荷的增大而增大；在相同速度，不同载荷下，磨合初期摩擦信号的分形维数均与初始表面分形维数负相关。根据预测模型分析可得，表面分形维数对摩擦力的影响有一最佳值；在最佳表面分形维数下，摩擦力F随着G*和A*r的减小而降低；动静涡旋端面摩擦副材料性能对摩擦力也有很大的影响，选择合适的自润滑材料及配对摩擦副可提高无油润滑涡旋压缩机的使用性能及寿命。
[Abstract]:Scroll compressor is a new type of high efficient displacement compressor with compact structure, stable operation, low noise and so on. Its application range has been from air conditioning to refrigeration to medicine and food. Fuel cells and other demand for clean compressed gas without oil pollution in the field of expansion. Because of the specific movement mode of scroll compressor, there are many friction pairs, and its friction loss greatly affects the efficiency and performance of the scroll compressor. The surface morphology of the friction pair has great influence on the performance of the compressor and the friction, wear, mixed lubrication characteristics and contact stiffness of the friction pair. Friction force and friction coefficient are important parameters to reflect friction and wear behavior of friction pairs. Quality control and improving the performance of parts are of great significance. The friction characteristics of the friction pair of the oil-free scroll compressor are not only related to the operating condition and load of the compressor, but also to the dual materials of the friction pair, the initial surface characteristics and the fractal characteristics of the end surface of the friction pair during operation. Therefore, the mathematical model of friction force is established by analyzing the micro contact and force on the end face of friction pair, and the friction behavior of tribological system of scroll compressor is predicted, which can provide a reference for the dynamic characteristic analysis and theoretical design of compressor. Based on tribology and fractal theory, the friction properties of polyether ether ketone (PEEK,) polyimide polyethersulfone (PI,) polyethersulfone (PES) and nodular cast iron (QT), a common material of scroll compressor, were studied by experiments. PEEK, with different initial surfaces was selected to collect the initial surface profile on the stylus type surface profilometer. The surface morphology was observed under JSM-5600LV scanning electron microscope and the PEEK/QT friction pair specimen test was carried out on the UMT-3MT friction tester. Fractal theory is used to characterize the surface morphology and friction signal, and the correlation between the initial surface morphology of PEEK and its friction signal is studied. On the basis of test, combined with M-B fractal model and sliding friction force fractal prediction model, according to the structure, operation mode and force characteristics of oil-free lubricated scroll compressor, Based on the analysis of the microcosmic contact state and microcosmic contact force of the static and static vortex friction pair, a fractal prediction model of the friction force of the static and static vortex end surface friction pair of the oil-free scroll compressor is established, and the calculation is carried out through an example. The model is verified and analyzed. The results show that both the initial surface and the friction signal of polyether ether ketone have significant fractal characteristics, and the fractal dimension of friction signal increases with the increase of load at the same velocity and at the same initial surface. At the same velocity and different loads, the fractal dimension of the initial friction signal is negatively correlated with the initial surface fractal dimension. According to the prediction model analysis, the influence of surface fractal dimension on friction force has an optimum value, and under the optimum surface fractal dimension, the friction force F decreases with the decrease of G * and ar. The material performance of the static and static vortex end face friction pair also has a great influence on the friction force. Choosing suitable self-lubricating material and matching friction pair can improve the performance and service life of the oil-free lubricated scroll compressor.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：TH45

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