Abstract:Due to the harsh requirements of low leakage and long stability under high operating conditions,an annular microgroove floating seal was proposed.Aimed at the problem of dynamic characteristic,the convergence problem of eccentric gas film was considered,the mutagenicity of Rayleigh step to gas film period was defined,the transient Reynold equation was established by using small disturbance method,and the disturbance trace relation between pressure and film thickness was obtained.The matrixes of the dynamic stiffness and dynamic damping were constructed,and the effects of groove,structure and operating conditions on the dynamic characteristic coefficient were studied.The results show that the curves of cross stiffness kxy and kyx are symmetrical to those of cross damping cxy and cyx respectively,and the variation rules of main stiffness kxx and kyy,main damping cxx and cyy are consistent.The main stiffness reaches the maximum at the helix angle of -20°and 30°.The main stiffness and main damping reach the maximum when the groove number is 10,and the difference of the cross stiffness and the sum of the cross damping tends to zero,indicating that it is beneficial to the sealing stability when the groove number is 10.The sealing system may be unstable when the rotating speed exceeds 38 000 r/min.The pressure difference has an obvious influence on the pressure flow and shear flow of the seal,which makes the sealing system in the stage of vortex divergence.In the condition of large eccentricity,the enhancement of the cuneiform effect resists the nonuniformity of gas film pressure and thicknessdistribution,which is beneficial to the convergence of vortex.However,the increase of gas film thickness increases the probability of seal instability.It is inferred that the ring microgroove floating seal is more suitable for the service conditions of small film thickness,low pressure,high speed and large eccentricity.