The Investigation On Dynamics Characteristics Of Oil-free Scroll Compressor

Scroll compressor is a new kind of positive machine.Scroll compressor has many favorable features,including high reliability,simple structure,high volumetric efficiency,low vibration and noise relative to other types of compressors.At present with the wide application of the scroll compressor its outstanding advantages have attracted the attentions of a lot of researchers.Due to the special working principle of the scroll compressor,it requires very high precision for structure,therefore the dynamic characteristics quality of the scroll compressor will directly affect the performance of the scroll compressor.The dynamic characteristics of the oil-free scroll compressor which displacement is 0.6m3/min are investigated quantitatively.The main contents of this paper are as follows:(1)The geometric modeling of the oil-free scroll compressor is presented based on the plane meshing theory of scroll profile and the circular involute equation.The evolution of the working chamber volume with respect to the orbiting angle is discussed.The dynamic modeling is developed and dynamic characteristics are discussed.The gas forces and moments acting on the orbiting scroll are solved.The simulation results show that the forces acting on mini-cranks in a cycle are continuous and periodic.Two maximum forces and two minimum forces appear in a period of 2?.The tangential force is far bigger than the other forces so it has a major impact on forces acting on bear of the shaft.(2)The friction losses of the main moving parts are analyzed based on the dynamic modeling.The power and the mechanical efficiency equations are also given.The analysis results show that the friction loss of the main bearing is much larger than that of other bearings.The friction loss of the main bearing is the most important factor affecting the mechanical efficiency.The change range of mechanical efficiency in the scroll compressor is very small.It proves that the oil-free scroll compressor has the very high stability.(3)3D model of the oil-free scroll compressor is established.The kinematics and dynamics of virtual prototype model are simulated by SolidWorks and Adams.Dynamic characteristics of the rigid-flexible coupling model are discussed combined with finite ANSYS.The simulation results show that the motion of the mini-crank of the scroll compressor is the same as that of the main shaft,which verifies the feasibility of mini-cranks as anti-rotation mechanism.The maximum,the change trend of the stress and deformation of the nodes are the same which shows that the forces acting on the three mini-cranks and the motion law are basically the same.The maximum deformation occurs near the groove.(4)The modal analysis of the main shaft and the mini-crank is performed using the finite element software ANSYS,bending and torsion are the main deformation forms of mini-crank and main shaft,the deformation of the counterweights is large,the deformation of the middle part of the main shaft is very small.(5)The experimental rig for developed oil-free scroll compressor prototype is set up.The test results show that the presented model has a satisfactory accuracy and the developed oil-free scroll compressor has the best comprehensive property.