A Design Method to Prevent Low Pressure Turbine Blade Flutter

Abstract

A design approach to avoid flutter of low pressure turbine blades in aircraft engines is described. A linearized Euler analysis, previously validated using experimental data, is used for a series of parameter studies. The influence of mode shape and reduced frequency are investigated. Mode shape is identified as the most important contributor to determining the stability of a blade design. A new stability parameter is introduced to gain additional insight into the key contributors to flutter. This stability parameter is derived from the influence coefficient representation of the cascade, and includes only contributions from the reference blade and its immediate neighbors. This has the effect of retaining the most important contributions to aerodynamic damping while filtering out terms of less significance. This parameter is utilized to develop a stability map, which provides the critical reduced frequency as a function of torsion axis location. Rules for preliminary design and procedures for detailed design analysis are defined. [S0742-4795(00)01401-0]

Flutter prediction in turbomachinery with energy method

“…It is well known that flutter boundaries are very sensitive to blade mode shapes and that the reduced frequency plays a secondary role. A comprehensive numerical study of the influence of both parameters for LPT airfoils was performed by Panovsky and Kielb [5] and supported by the experimental work done by Nowinski and Panovsky [6]. Also, a reduced-order model for simulation and stability analysis of highincidence flutter and rotating stall, based on an actuator disc approach, was constructed by Copeland and Rey [7], which was predicted in good agreement with the measurements.…”

Numerical Investigation of the Effect of Flutter Instability of the Blade on the Unsteady Flow in a Modern Low-Pressure Turbine

“…A 'high-lift' blade design, which increases the required aerodynamic loads on the blade but using fewer blades, is one of the outcomes [4]. However, this design not only decreases the highly correlated LPT flutter parameter known as reduced frequency but also introduces the higher per-stage loading [5][6][7], potentially leading to aeroelastic instabilities such as flutter as a result of a high aspect ratio of the blade [8]. Many structural failures of the blade of LPTs are directly associated with aeroelastic instability problems [9].…”

Analysis of classical flutter in steam turbine blades using reduced order aeroelastic model

“…In the quest to generate more power in the nuclear power plants giant steam turbines are being installed. The large low pressure steam turbine blades are more prone to mechanical vibration due to longer size and less stiffness, which leads to high-cycle fatigue failure and in worse case blade loss and damaging the whole system.The aeroelasticity of low-pressure turbine blade has been the subject of much attention in the past and recent years [1,2]. Aerodynamic damping is considered as an crucial parameter to quantify the classical flutter or aeroelastic stability of the system.…”