Research On Static Characteristics And Aerothermal Of Foil Thrust Gas Bearings

With the increasing of the speed and performance requirements of the small turbo turbine,the requirements of the bearing capacity of the dynamic pressure gas thrust bearing is increasingly rigorous,and the study of key parements and influence law of bearing will be helpful to enhance the design capability of the bearing.At the same time,the aerothermal produced by high speed rotating bearing can cause the loss of the bearing,so it is very important to master the aerothermal characteristics of foil type dynamic pressure gas bearing,which is particularly important to bearing reliability design.In this paper,the static and aerodynamic characteristics of dynamic pressure gas thrust bearing are studied by numerical simulation and experiments,and the main contents and results are as follows:First of all,taking foil dynamic pressure gas thrust bearing as the research object.Establishing the variable-section gas-film gap model,and using SST k-?flow model,Using numerical simulation to study the rotational speed??=1×10⁴r/min⁵×10⁴r/min?,the rotating state?the rotary slope,the reverse slope rotation,the thrust disc rotation,bearing rotation?,bearing clearance ratio(h/h_out=5²5),variable section pitch ratio?b=0.2⁰.8?and other paraments'influence on the bearing gas film pressure distribution and bearing capacity of the law,the results show that:The bearing capacity becomes larger as the rotation speed increases,and the maximum increase is 4 times.The bearing capacity produced by the rotation of the inclined plane is much larger than the bearing capacity produced by the reverse bevel rotation,the maximum is 76.5N,which indicates that this type of bearing is not suitable for the application environment with rotor inversion;the bearing capacity of thrust disc rotation and bearing rotation is approximately same,the maximum variance is not more than 5%;The bearing capacity decreases as the air film gap ratio increases,which drops by 50%⁸0%at different speeds,this rule makes the dynamic pressure gas thrust bearing can adjust the bearing capacity according to the change of load force;and the bearing capacity increases first and then decreases as pitch ratio increases.When b=0.5,the bearing capacity is maximum,and the maximum bearing capacity is larger than the minimum bearing capacity 15%³0%.Then,a viscous dissipation term is introduced to calculate the dimensionless temperature distribution of the gas film gap in different working conditions on the basis of the calculation of the bearing speed,and the inlet/outlet pressure?P₁=0.1MPa¹.2MPa?,and the inlet/outlet temperature?T₁=300k³75k?,and the bearing clearance ratio,and the variable section pitch ratio.The results of the numerical analysis shows that the gas film temperature ratio decreases significantly as inlet/outlet pressure ratio increases?1¹2?under the condition of single terminal inlet,and the most decrease is 2.04,and increases as the rotational speed increases;and decreases as the inlet temperature increases;and the change of bearing clearance ratio and pitch ratio has little influence on it.Under the same change of inlet/outlet pressure,the gas film temperature ratio decreases as inlet/outlet pressure increases,and the most decrease is 1.68,the gas film temperature ratio increases as rational speed increases;The temperature of the gas film decreases as the gap ratio of the bearing increases and the temperature ratio of the highest point varies with the pitch ratio.Finally,a test rig for the aerodynamic characteristics of the foil-type dynamic pressure gas thrust bearing is established,which is used to test the influence of bearing speed,inlet pressure and inlet temperature on the dimensionless temperature field of gas film,and the results show that the numerical calculation is in accordance with the test result,and the calculated result is about 16%larger than the test result.The bearing rotational speed and the inlet temperature both increases as temperature ratio decreases.Since the cooling and lubrication are the same inlet,the inlet pressure increases first and then drops,and there is an optimal inlet pressure.The results of this paper can provide technical reference for the performance and cooling optimization design of this type of bearing.