Numerical and Experimental Studies of Labyrinth Seal Aeroelastic Instability

Abstract

A labyrinth seal is commonly used to decrease the flow leakage loss between rotating and static components in aero engines. It is susceptible to aeroelastic instability because of its low stiffness. The aim of this study is to clarify the physical mechanism of labyrinth seal flutter and to establish a method to predict and suppress it effectively. To achieve this, both numerical and experimental investigations are conducted using ANSYS CFX and ANSYS Mechanical. These solvers are coupled to simulate the flutter precisely. Also, to assess the accuracy of the simulation qualitatively and quantitatively, a test rig is built. In the first part of this study, the accuracy of the numerical method is confirmed for several test cases with different seal clearance variations. Both one-way and two-way fluid structure interaction (FSI) analyses are performed. Flutter inception is evaluated in detail for various pressure ratios and rotation speeds. The numerical results show reasonably good agreement with the experimental results. It is also confirmed that the aeroelastic instability is very sensitive to the seal clearance variations. These results show the same tendency as those in previous works [1–5]. In the second part of this study, this paper tries to develop a flutter suppression method without deteriorating the flow leakage performance. This is achieved by changing the seal geometry without changing the seal clearance variation. To detect the important geometric parameters, the contribution of each geometric component to aeroelastic instability is carefully analyzed. On the basis of this, the seal geometry is modified and its performance is also evaluated. The optimized labyrinth seal shows good performance in terms of flow leakage and aeroelastic stability. Through this study, a new method to suppress the flutter with low flow leakage is established.

Nonlinear Flutter Analysis of the Zero Nodal Diameter of a Labyrinth Seal

“…The results are compared with Abbott's stability criterion suggesting that complex seal configurations are not appropriate to be treated with simple stability criteria based on the comparison of the structural and acoustic frequencies. More recently, Miura and Sakai (2019) have compared CFD results with experimental data obtained in an in-vacuum rotating rig. The numerical results show reasonably good agreement with the measurements.…”

Higher-Order Conceptual Model for Labyrinth Seal Flutter

“…This model showed the existence of new dimensionless parameters which played a key role in seal instability. More recently, the model was extended to deal with stepped seals [11,12] and new experiments conducted [13]. A short review of the relevant studies conducted on seal instabilities, as well as of their respective conclusions and shortcomings, is given next.…”

“…All previous studies relied on experimental data and simplified analytical models since CFD methods were not affordable at that time. Recently, there has been a renewed interest in seal flutter, and the identification of its relevant parameters using CFD tools [18,19,20,13]. Despite these efforts, no new clear conclusions were drawn apart from the success in matching the scarce experimental results.…”