Numerical Simulation Of Internal Flow Field And Study Of Stress And Deformation Of Oil-free Twin-wraps Scroll Compressor

Scroll compressor,as a new type of positive displacement compressor,has the characteristics of few parts,light weight and stable operation,and is widely used in people's production and life.In view of the current research situation of oil-free scroll compressor,a prototype of oil-free twin-wraps scroll compressor is developed.The internal flow field was simulated transiently,and the stress and deformation distribution of meshing scroll teeth were analyzed.Finally,the performance parameters of the prototype are measured to verify the correctness of the flow field simulation.The specific research work is as follows:(1)The curve equations of twin-wraps are derived,and the scroll line of the prototype are drawn.The main parts and working principle of the prototype are introduced.Through the analysis of the force acting on the moving scroll,the gas force and torque acting on the moving scroll are obtained by means of numerical calculation.The results show that: The change of the gas force and gas torque of the twin-wraps scroll compressor is relatively stable,and the amplitude of the fluctuation is small.The radial gas force is obviously the smallest,and it is a constant value within a week of spindle rotation.The axial gas force is the largest,and both the tangential gas force and the axial gas force change periodically at 90 degrees.Compared with the rotation torque of the scroll,the overturning torque has a greater impact on the compressor and should be taken seriously.(2)From the perspective of modal analysis and harmonic response analysis,the dynamic characteristics of the moving scroll are analyzed by using the finite element method,and the six-order natural frequencies of the moving scroll and the variation law of deformation at different frequencies are obtained under the action of gas force.The results show that the scroll tooth is easy to vibrate,but the natural frequency is much higher than the normal working frequency of the scroll compressor,indicating that the compressor will not produce resonance phenomena and can effectively avoid the normal resonance area,and meet the safety requirements.The load has peak deformation response at 465 Hz,695Hz and 1442 Hz,which is consistent with the modal analysis results.These three frequencies are very close to the natural frequency,and the resonance phenomenon is most likely to occur.(3)Combining the theoretical knowledge of thermodynamics and heat transfer,the thermodynamics of compression process is studied.The thermodynamic analysis of the whole cycle process of the compressor is analyzed,the heat transfer and leakage models of the working chamber and the control equations of the working medium in the simulation calculation are established.(4)By using the method of CFD simulation and dynamic grid technology to numerically simulate the established flow field model,the law of fluid movement inside the compression chamber and the distribution of the velocity field,pressure field,and temperature field were obtained;Study on the law of stress and deformation in the meshing state of scrolls.The results show that the movement of the fluid is consistent with the direction of rotation of the scroll,and there will be a small amount of leakage at the meshing gap;the pressure distribution is relatively uniform,the pressure in the compression chamber increases from outside to inside,and the pressure at the center is the largest;the temperature distribution of each chamber is not uniform enough,and the temperature shows an upward trend from the intake region to the central exhaust region.The temperature load has the greatest influence on the stress and deformation of the scroll teeth,and the stress value in the coupled field is less than the yield strength of the material,indicating that the scroll is safe and reliable in practical use.(5)A test platform was built to test the performance parameters of the prototype,and the variation of power,exhaust temperature and exhaust volume changing with exhaust pressure were obtained under different rotating speeds.The test results show that: at the same speed,with the increase of exhaust pressure,except that the exhaust volume has no obvious change,the exhaust temperature and power are increasing;at the same exhaust pressure,the higher the speed,the higher the exhaust temperature,power and exhaust volume.The correctness of the simulation is further verified by comparing the test data with the simulation data,which provides a certain data support for the further study of the oil-free twin-wraps scroll compressor.