Flow Field Analysis And Thermal Fluid Solid Coupling Of Supercritical Carbon Dioxide Dry Gas Seal

The supercritical carbon dioxide Brayton cycle has the advantages of clean working medium,high cycle efficiency,high energy density and small equipment volume,etc.it is a hot research topic in recent years.Because of the latent heat phenomenon of phase transformation when the circulating working medium crosses the critical point,the motor turbine coaxial rotor and the sealing system of the system also face a series of complex problems.In the micro scale dry gas seal of Brayton cycle turbine and compressor,S-CO₂ is the first choice because of its own physical and chemical properties.However,the physical parameters of S-CO₂ are highly nonlinear near the critical point,which greatly increases the research and design difficulty of S-CO₂ dry gas seal.In order to explore the influence of its operating conditions and structural parameters on the S-CO₂ dry gas seal,this paper uses Solidworks software to establish 1/N_g geometric model of spiral groove calculation domain,imports ICEM software to carry out structured grid division,uses REFPROP software to obtain the phase data of S-CO₂,and compiles these physical parameters into C language program and transfers them into fluent UDF platform to simulate the flow field,so as to explore the influence of the physical parameters on the flow field,The interaction of different operating parameters and structural parameters on film pressure distribution,film opening force and leakage under actual gas effect,inertial effect,centrifugal effect and turbulence effect.The results show that with the increase of rotating speed,the opening force and leakage of the gas film increase first,then decrease,and then tend to be stable;the increase of pressure difference makes the opening force and leakage of the gas film increase;the increase of the thickness of the gas film leads to the decrease of the opening force and the increase of the leakage of the gas film.In the aspect of the influence of groove parameters,the opening force and leakage amount first increase and then decrease with the increase of groove depth;the increase of groove number makes the opening force and leakage amount increase;while the influence of helix angle on the leakage amount is greater than the opening force.No matter the opening force,leakage amount,film rigidity or rigid leakage ratio,the sealing performance of double groove is always better than that of single groove.The results show that the seal performance of dry gas seal is better when the film thickness is 3.05?m,the groove depth is 5.05?m,the number of grooves is 12,and the helix angle is 15°.In the workbench,the thermal stress coupling analysis module,fluid flow?fluent?flow field analysis module and static structural field analysis module are transferred in.Then,the pressure and temperature of the flow field are loaded and the dynamic and static rings are restricted by the region and the force to analyze the stress and strain of the seal ring under the thermal fluid solid coupling.The results show that under the same coupling condition,the maximum stress-strain of SiC is less than that of WC,the stress-strain of double grooves is always greater than that of single groove,and the stress-strain of the corresponding static ring of double grooves is also greater than that of single groove.The deformation of the moving ring is mainly composed of two parts.In addition to the normal positive taper deformation on the surface of the moving ring caused by the thermal force of the air film,there are also the normal negative taper expansion deformation on the surface of the moving ring caused by the shear heat generated by the high-speed rotation of the moving ring.Because the normal negative taper deformation offsets some positive taper deformation,the deformation on the surface of the moving ring is smaller than that of the static ring.However,the maximum deformation of the static ring is only the result of unidirectional thermal force of the gas film.