A Study For Wave Character And Safety Of Supersonic Slot Jet Of Circular Gas Bearing In The High Supply Pressure

High pressurized circular thrust bearing with bisymmetric contraction can overcome the disadvantage of the bearing capacity limited by the air supply pressure.In theory,the bearing capacity will increase linearly with the increase of the supply pressure.But when the air flow to the clearance of the bearing will be supersonic.A type of supersonic disk slot jet will be formed.With a great noise and partial low temperature,experimenter may get hurted when they operate by Supersonic jet.The jet noise is closely contacted with Mach wave radiation.So,study the characteristics of supersonic disk gap jet flow field of high pressure supplied gas bearing is a base to study noise for ensuring bearing-experiment personnel safety.Unexpanded supersonic jet structure was got through a numerical simulation on0.3 mm clearance of bearing by Fluent on SST k-? model.Result shows that lowunexpanded wave system in supersonic disk slot jet flow field is similar as that of low-unexpanded supersonic axisymmetric jet flow field.high-unexpanded disk slot supersonic jet flow field just shows a part of the intercepting shock wave without Mach disc in the initial period,then the intercepting shock reduce to compression wave.While expanded supersonic jet structure was got through a numerical simulation on 2 mm clearance of bearing,but in the expanded disk slot jet flow field,shock wave structures can't be found,therefore,high-expanded,mid-expanded low-expanded can't define.Sound pressure level of noise is simulated by fluent with broadband noise source model in the jet flow field.According to the results and ISO and USA ear protect standards and this paper's analysis of example,experimenter should not enter?zone in the temperature field.In the noise field,? area still could not enter even wearing earplugs;? area,wear earplugs can enter this area,but the working hours must under0.25 h;After ? area,this area is safe,if wear earplugs,you can work continuously.The results of this paper may be show a strong guiding significance for bearing-experiment design.