Effects of Four Types of Pre-swirls on the Leakage, Flow Field, and Fluid-Induced Force of the Rotary Straight-through Labyrinth Gas Seal

Qingfeng Wang,Lidong He

doi:10.1186/s10033-019-0370-6

Qingfeng Wang, Lidong He

Open Access

https://doi.org/10.1186/s10033-019-0370-6

Copy DOI

Abstract

The labyrinth seal in turbomachinery is a key element that restricts leakage flow among rotor-stator clearances from high-pressure regions to low-pressure regions. The fluid-induced forces on the rotor from seals during machine operation must be accurately quantified to predict their dynamic behavior effectively. To understand the fluid-induced force characteristics of the labyrinth seal more fully, the effects of four types of pre-swirls on the leakage, flow field, and fluid-induced force of a rotary straight-through labyrinth gas seal (RSTLGS) were numerically investigated using the proposed steady computational fluid dynamics (CFD) method based on the three-dimensional models of the RSTLGS. The leakage, flow field, and fluid-induced force of the RSTLGS for six axial pre-swirl velocities, four radial pre-swirl angles, four circumferential positive pre-swirl angles, and four circumferential negative pre-swirl angles were computed under the same geometrical parameters and operational conditions. Mesh analysis ensures the accuracy of the present steady CFD method. The numerical results show that the four types of pre-swirls influence the leakage, flow field, and fluid-induced force of the RSTLGS. The axial pre-swirl velocity remarkably inhibits the fluid-induced force, and the circumferential positive pre-swirl angle and circumferential negative pre-swirl angle remarkably promote the fluid-induced force. The effects of the radial pre-swirl angle on the fluid-induced force are complicated, and the pressure forces and viscous forces show the maximum or minimum values at a specific radial pre-swirl angle. The pre-swirl has a negligible impact on the leakage. The four types of pre-swirls affect the leakage, flow field, and fluid-induced force of the RSTLGS to varying degrees. The pre-swirl is the influence factor affecting the leakage, flow field, and fluid-induced force of the RSTLGS. The conclusions will help to understand the fluid-induced force of labyrinth seals more fully, by providing helpful suggestions for engineering practices and a theoretical basis to analyze the fluid–structure interaction of the seal-rotor system in future research.

Highlights

Turbomachineries contain numerous labyrinth seals operating within close proximity to rotating parts, for preventing flow recirculation in the compressor and turbine stages, to meter cooling air to various parts of theWang and He C hin
To obtain a more detailed insight into the fluid-induced force of the labyrinth seal, the present study applies the steady computational fluid dynamics (CFD) method based on the three-dimensional model of the rotary straight-through labyrinth gas seal (RSTLGS)
Analysis Method In this work, the leakage, flow field, and fluid-induced force of the RSTLGS are analyzed in terms of the leakage flow rates, velocity vectors, velocity streamlines, Table 3 Boundary conditions

Summary

Introduction

Turbomachineries contain numerous labyrinth seals operating within close proximity to rotating parts, for preventing flow recirculation in the compressor and turbine stages, to meter cooling air to various parts of the. With the CFD program, the numerical simulation method has been used to study the leakage flow and rotordynamic characteristics of labyrinth seals by Moore [20], Hirano et al [21], Pugachev et al [22], and Subramanian et al [24]. To obtain a more detailed insight into the fluid-induced force of the labyrinth seal, the present study applies the steady CFD method based on the three-dimensional model of the rotary straight-through labyrinth gas seal (RSTLGS). Governing Equations CFD is a computer-based tool for simulating the behavior of systems involving fluid flow, heat transfer, and other related physical processes. The shear stress transport (SST) model in ANSYS CFX 17.0 is chosen to simulate the fluid flow in the seal. The SST model accounts for the transport of the turbulent shear stress and provides highly accurate predictions of the onset and amount of flow separation under adverse pressure gradients

Numerical Calculation Method

Inlet Outlet Seal wall Rotor wall

Axial Radial Circumferential positive Circumferential negative

Results and Discussion

Findings

Conclusions