The Research On Dynamic Characteristics Of Oil-free Twin-wraps Scroll Compressor

As a new and high effective and low noise displacement compressor, scroll compressor has been widely used in air conditioning and refrigeration with an irreplaceable advantage. Its application is getting much wider as the development of computing technology and manufacturing advances. Application of twin-wraps structure meets the requirement of large magnitude and the oil-free design meets special conditions such as the needs of some clean gas. Therefore, investigation and invention of scroll compressor with high quality oil-free twin-wrap is of great importance in practice. Funded by NSCF funding of "Study of coupling friction and dynamics in oil-free twin-wrap compressor" and "Investigation of friction and rotor dynamics performance in variable volume scroll compressor", the present work is aimed at developing geometrical model, leakage model and heat transfer and dynamic model for oil-free twin-wrap based on the circle involute theory. A theoretical base was established for considering reliability and high performance design of oil-free twin-wrap compressor by the study of orbiting scroll overturning, varying radial dynamic, balance of rotor, and consider institutional dynamics hinge gap.Aimed at gear cutting twin-wraps structure with zero suction angle, a geometrical coordinate system was set up for scrolls with integer and non-integer unfold turns. A complete set of geometrical model was developed by defining exhausting angle based on spread angle in both end and staring central plane. The model can describe the engagement process of dynamic and static scroll and volume vary in each compressor chamber. The characteristics of the twin-wraps structure was analyzed by using the formation of working volume and leakage and heat exchanger of adjacent chamber.Based on analyzing the structure, force, leakage and lubrication of oil-free twin-wrap, the friction pair was categorized and discussed. The friction mathematical of radical bearing friction and side face engagement friction was developed. And self-lubricating materials containing friction associate of applied tribology theory, the mechanical model of the main parts established.Based on the mechanical characteristics of the orbiting scroll, the overturning moment mathematical model on the orbiting scroll was established, and the azimuth angle was defined. According to the basic theory of the roller bearing-Hertz elastic contact theory, the relationships between the radial load and deformation, the outer ring tilt and deformation of needle roller bearing without inner ring were established, and the force model of needle roller bearing was given while the radial force and overturn coexist. The results provide evidence for the selection of scroll geometric parameters and drive bearing. Based on four-link mechanism of scroll compressor, combined with theory of mechanism, a balance analysis of fixed weight of rotor system was made and various design philosophy was proposed. The numerical model of rotor system unbalance and bearing bearer by the balance weights bias was developed. The effect of the radial adjustment on balance was discussed by the change with radial principle. A numerical model of input torque model of the rotor system was developed by the principle of virtual work, and the effect of the balance weights bias and size error on the input torque was analyzed. A theoretical base was provided for the machining accuracy and precision assembly selection.Due to the dimension error, gap of contacting pairs and wear, the scroll compressor is not able to satisfy the ideal four-link condition. Therefore, a model taking these effects into account was developed. By using ADAMAS, the dynamic characteristics of hinge joint components was analyzed, which provides a base for wearing feature in hinge joints.The reliability of self lubrication in orbiting and fixed scrolls inlay was verified with friction tests, dynamic balance test and sample machine testing. Also testified with those tests was the necessity and accuracy of dynamic balance, which provides a theoretical base for developing high performance oil-free compressor and its subsequent investigation.