Study Of Flow Field And Injection Characteristics Of Oil Injection Twin-Screw Air Compressor

Twin-screw compressor is widely used in petrochemical industry,machinery manufacturing,coal,mining,textile and other national economic fields because of its compact structure,reliable operation and high efficiency.Oil injection can play a prominent role in sealing,lubrication,cooling and noise reduction of twin-screw compressors,and also has a great influence on the overall performance of twin-screw compressors.In this paper,the injection characteristics of screw compressor are numerically simulated based on computational fluid dynamics(CFD)and multiphase flow(VOF)model.The effects of different nozzle diameters,positions,directions and numbers on the distribution of oil and temperature in the compression chamber and on the volumetric efficiency and exhaust temperature of the compressor are analyzed.The effects of different working conditions on the force of the compressor screw rotor are also analyzed to improve the operating stability of the compressor.The main research contents include:(1)Based on the design theory of screw compressor rotor profile,the data of Yin-Yang rotor profile are obtained,and the twin screw compressor model is established according to the profile data.The influence mechanism of oil injection on the working performance of screw compressor is studied,and the process of oil injection atomization,oil droplet movement and heat transfer of oil and gas are analyzed.(2)The internal flow field model of the oil-injected twin-screw air compressor was constructed.Based on CFD and VOF models,the distribution of the injection state of different injection port positions and injection port directions in a working cycle was analyzed.Taking the central injection port as an example,the diffusion process of oil in the compression chamber during the first cycle of the positive rotor rotation was analyzed.The flow change of the compressor and the force characteristics of the rotor,as well as the distribution characteristics of pressure,temperature and oil in the internal flow field were studied.(3)The distribution of temperature field and oil in the compression chamber was analyzed by different nozzle diameter,position,direction and number.The flow rate,exhaust temperature and compressor power of the compressor under different working conditions are obtained by simulation.By comparing the heat transfer performance of oil and gas under different working conditions and the influence on the volumetric efficiency of the compressor,a better injection effect is obtained.(4)The transient analysis of the compressor flow field is carried out.The variation law of the rotor force under compression and over compression under the working pressure of 0.4 MPa,0.6 MPa,0.8 MPa and 1.0 MPa is studied.The influence of oil injection condition and oil-free condition on the force of the rotor is compared.By analyzing the influence of exhaust pressure and injection on the force of screw rotor,the variation of torque,gas axial force and gas radial force of rotor under different injection conditions is analyzed.