CFD Applied for the Identification of Stiffness and Damping Properties for Smooth Annular Turbomachinery Seals in Multiphase Flow

Abstract

This paper presents a first venture into quantifying stiffness and damping coefficients for turbomachinery seals in multiphase flow using Computational Fluid Dynamics (CFD). The study focusses on the simplest seal type: the smooth annular seal. The investigation is conducted for both wet-gas and bubbly flow regimes in which the primary phase is gas (air) and liquid (water), respectively. For the wet gas regime three different Liquid Volume Fraction (LVF) conditions are included in the study; 5%, 3% and 0%. Similarly for the bubbly flow regime three Gas Volume Fractions (GVF) conditions are included; 5%, 3% and 0%. An Eulerian-Eulerian modelling approach is taken, applying an inhomogeneous model, where the primary phase is treated as continuous and the secondary phase is included as dispersed. The Instationary Perturbation Method (IPM) is applied to identify the rotordynamic coefficients, in which the rotor is harmonically perturbed, and forces acting on the rotor are quantified through integration of the pressure and shear stresses. The perturbation is repeated for different frequencies to uncover any frequency dependence. The results presented in this paper are intended as an initial comparison basis for the experimental results to be obtained by applying the multiphase seal test facility currently in development, as part of a collaboration between Lloyd’s Register Consulting, the Technical University of Denmark, OneSubsea, TOTAL and Statoil.

A CFD-Based Frequency Response Method Applied in the Determination of Dynamic Coefficients of Hydrodynamic Bearings. Part 1: Theory

“…The perturbation frequencies were varied from 0.8× to 1.2× multiples of the rotational frequency Ω. Performing the CFD simulations near the rotational speed alleviates the need to resolve multiple time scales (high frequency perturbation) or run the simulations for long physical time with a small time step (low frequency perturbation) [38]. At low perturbation frequencies, the simulation must be run for a long physical time to capture several oscillations of the perturbation boundary.…”

Design and Calibration of a Full Scale Active Magnetic Bearing Based Test Facility for Investigating Rotordynamic Properties of Turbomachinery Seals in Multiphase Flow

“…The test facility is designed to be able to mirror the Instationary Perturbation Method (IPM) applied for numerical estimation of seal properties using CFD. This method is described in detail in [26,[35][36][37][38], and relies on perturbing the seal flow by moving the shaft in a prescribed 1D sinusoidal pattern with a constant amplitude and for multiple frequencies. Acquiring information on the reaction forces exerted on the seal rotor allows the coefficients of Eqn.…”

“…This research venture was initiated to ensure validated predictive capabilities through state of the art Computational Fluid Dynamics (CFD) benchmarked using high quality experimental data. The state of the art regarding determination of rotordynamic coefficients for seals in multiphase flow using CFD can be found in [35].…”

Investigation of the Dynamic Characteristics of an Eccentric Annular Seal on the Basis of a Transient CFD Method with Three Whirl Models

“…It was revealed that the magnitudes of dynamic coefficients of the seal obtained by the three whirl models match very well with the experimental results, and the values of the corresponding dynamic coefficients are almost the same for all rotor whirl models. The transient CFD method with the whirl models was also employed by Voigt [18], Yan et al [19,20] and Jiang [21] to calculate the dynamic characteristics of annular seals.…”