Investigation On Flow Field Characteristics And Contact Behavior Of Spiral Structure Gas Bearing

Dry spiral gas machinery such as precision spiral groove gas bearings and scroll compressors mainly achieve normal and stable work by the gas hydrodynamic effect during high-speed operation: precision spiral groove gas bearings will generate microgap gas hydrodynamic lubrication at high speeds.When the speed of bearings is low,the gas hydrodynamic effect is small,and effective gas film cannot be formed,resulting in direct surface contact and wear of the bearings.The scroll compressor mainly achieves gas delivery through the gas hydrodynamic effect in the three-dimensional spiral chamber.But when the gas flow is at high speed and high temperature,it will cause wear of the scroll plate surface.In response to these problems,the gas hydrodynamic effect of the dry gas machinery can provide a basis for its surface wear prediction,and has important significance for improving its working life.In this paper,the flow field and gas hydrodynamic effect of micro-gap spiral groove gas bearings and three-dimensional spiral structure scroll compressors are studied.The specific research contents are as follows:The hydrodynamic effect analysis model of the spiral groove gas bearing is established.The FK modified model of the Reynolds equation is used to consider the gas thinning effect.The pressure of the gas in the micro-gap state is calculated.The contact force of the rough surface of the gas bearing is calculated by the GW model based on statistics.The dynamic gas film gap,air bearing force and contact force of the spiral groove gas bearing are obtained.The results show that the higher rotation speed of the gas bearing lead to the greater air bearing force and the smaller contact force.When the air bearing force is greater than the axial load,the contact force will decrease to 0.The analysis model of the dynamic pressure of the gas in the working chamber of the scroll compressors is established.The first dynamic law of thermodynamics and the equation of state of the ideal gas are used.Using the CFD method,the three-dimensional hydrodynamic flow field of the scroll compressor was modeled,and the gas pressure,temperature,and velocity distribution at different speeds and outlet pressures,as well as the outlet flow rate and the force of the movable scroll are obtained.The results show that in the process of inhalation,the temperature and pressure of the gas in the working chamber remain unchanged,and the mass increases.In the process of compression,the pressure and temperature of the gas increase,and the mass remains unchanged.In the process of exhaust,the pressure and temperature of the gas gradually decrease and achieve stability,the quality gradually decreases.The leakage behavior mainly affects the mass of the gas during the process of compression,and the lower speed leads to the more leakage of the gas.The higher speed leads to the higher peak pressure and temperature of the gas in the scroll compressor.The higher gas outlet flow rate and the greater force of the gas on the movable scroll plate are also because of the higher speed.When the outlet pressure is higher,the pressure of the gas in the chamber is higher,the force of the gas on the movable scroll plate is greater.Aiming at the surface contact and friction behavior of gas bearings during operation,a test plan for dynamic friction performance of dynamic pressure gas machinery is proposed,and a test device for dynamic friction performance is built.The effects of speed and load on the hydrodynamic performance of the spiral groove gas bearings are tested,and the critical speed of the gas bearing when the two surfaces of the bearing come out of contact is obtained.