Spiral Groove Liquid-film Seal Research Articles

Analysis of dynamic characteristics of spiral groove liquid film seal under thermal–fluid–solid coupling

Purpose The purpose of this paper is to investigate the dynamic characteristics of spiral groove liquid film seal under the effect of thermal–fluid–solid coupling. Design/methodology/approach The dynamic analysis model of spiral groove liquid film seal under the effect of thermal–fluid–solid coupling was established by perturbation method. The steady-state and perturbation Reynolds equations were solved, and the steady-state sealing performance and dynamic characteristic coefficients of the liquid film were obtained. Findings Compared with the liquid film without coupling method, a divergent seal gap is formed between the seal rings under the effect of thermal–fluid–solid coupling, the minimum liquid film thickness decreases, the dynamic stiffness and damping coefficients of the liquid film are increased and the thermoelastic deformation of the end-face improves the dynamic performance of the liquid film seal. Originality/value The dynamic characteristics of the spiral groove liquid film seal under the effect of thermal–fluid–solid coupling are studied, which provides a theoretical reference for optimizing the dynamic performance of the non-contacting liquid film seal.

Influence of turbulent cavitating flow on performance characteristics of spiral groove liquid film seal

Spiral groove liquid film seal is expected to be the prime candidate for application to high-speed liquid-oxygen turbopumps, and the lubricant flow between the sealing faces is turbulent due to the liquid-oxygen properties and the working conditions. Based on the Ng–Pan model and mass-conserving algorithm, the modified dynamic Reynolds equation considering flow regime and cavitation is obtained, which is solved by the finite-difference method. The effects of flow regime and cavitation on the performance of spiral groove liquid film seal are analyzed. The results indicate that the balanced film thickness and opening force increase due to the turbulent flow. The cavitation ratio increases in the laminar–turbulent transition region, which reduces the opening force and liquid film stiffness.

Influence of power-law fluid on transient performance of liquid film seal based on the time-dependent non-Newtonian dynamic Reynolds equation

The effects of lubricant's non-Newtonian property on dynamic characteristics of spiral groove liquid film seal are presented in this paper. The modified dynamic Reynolds equation for non-Newtonian fluid is derived, which is solved simultaneously with the kinematic equation. The transient response to the rotor's axial runout and angular misalignment, such as the axial and angular movement of stator ring, the transient film thickness, are presented for different power-law indexes, as well as the transient performance parameters. The results indicate that the seal has larger film thickness under the lubrication condition with dilatant lubricant while the stator ring has better tracking property operating with shear-thinning lubricant. Overall, the non-Newtonian property should be considered in the design of liquid film seal.

Effects of operating conditions on cavitation induction of spiral groove liquid-film seal (SG-LFS)

PurposeThe purpose of this paper is to study the effects of operating conditions including process coefficient, lubricant viscosity and cavitation pressure on the cavitation of spiral groove liquid-film seal (SG-LFS).Design/methodology/approachA mathematical model of SG-LFS is established based on the JFO boundary and a relative density is introduced. The universal governing equation after a coordinate transformation is discretized by the FVM method and solved by the Gauss-Seidel relaxation scheme.FindingsThe results indicate that the two-dimensional size of cavitation and cavitation degree are affected significantly by the process coefficient and lubricant viscosity but the effect of cavitation pressure can be ignored.Originality/valueThe effect mechanisms of operating conditions on the cavitation of SG-LFS are studied by the JFO boundary and cavitation degree characterized by a relative density. The results presented are helpful to perfect and deeply understand the cavitation mechanism of liquid-film seal.Peer reviewThe peer review history for this article is available at:https://publons.com/publon/10.1108/ILT-03-2020-0083/

Dynamic response of spiral groove liquid film seal to impact conditions

Abstract The dynamic response of the spiral groove liquid film seal to three types of impact are studied by developing a three-DOF dynamic model which takes average flow model, cavitation effect, squeeze effect and face contact into account. A Gaussian pulse function is first applied to simulate the impact to the seal. Results indicate that the seal can maintain hydrodynamic lubrication regime to avoid significant face contact regardless of the impact type. The pressure variation impact does not necessarily induce leakage due to the dramatically narrowed sealing gap. The shaft drifting and bending impact conditions can bring about leakage risk, but the symptomatic flow rate induced by the former is much heavier than that by the latter at the representive moment.

Analysis of dynamic characteristics of spiral groove liquid film seal considering cavitation

PurposeThe purpose of this paper is to investigate the dynamic characteristics of a spiral groove liquid film seal considering the effect of cavitation.Design/methodology/approachA mathematical model of a spiral groove liquid film seal was established based on the mass-conserving Jakobsson–Floberg–Olsson cavitation boundary condition. The film rupture and film reformation boundaries were assumed to be unchanged under infinitesimal perturbation conditions. Governing equations under steady and perturbed states were solved by the finite element method, and then the dynamic characteristics of the spiral groove liquid film seal were theoretically investigated considering the effect of cavitation.FindingsThe results indicate that dynamic coefficients considering cavitation are smaller than those neglecting cavitation. The difference value is consistent with the change in cavitation area. The liquid film seal does not suffer axial instability whether considering cavitation, but its angular instability is more likely to occur when cavitation is considered.Originality/valueFor liquid lubricated non-contacting mechanical seals, the dynamic characteristics considering cavitation are investigated. The results are expected to provide a theoretical basis for improving the design method of liquid film seals.