Effects of a Single Blade Incidence Angle Offset on Adjacent Blades in a Linear Cascade

Jiří Fürst,David Šimurda,Jan Lepicovsky,Martin Lasota,Petr Šidlof,Josef Musil,Jan Pech

doi:10.3390/pr9111974

Abstract

The paper presents a numerical and experimental investigation of the effect of incindence angle offset in a two-dimensional section of a flat blade cascade in a high-speed wind tunnel. The aim of the current work is tp determine the aerodynamic excitation forces and approximation of the unsteady blade-loading function using a quasi-stationary approach. The numerical simulations were performed with an in-house finite-volume code built on the top of the OpenFOAM framework. The experimental data were acquired for regimes corresponding to the numerical setup. The comparison of the computational and experimental results is shown for the static pressure distributions on three blades and upstream and downstream of the cascade. The plot of the aerodynamic moments acting on all five blades shows that the adjacent blades are significantly influenced by the angular offset of the middle blade.

Highlights

At present, the most important vibration problem faced by designers and operators of large-power turbomachines is blade aeroelastic instability called “blade flutter”—flowinduced oscillation of the turbine or compressor blades
Blade flutter problems started to appear with increasing frequency in high-efficiency power-generating turbines with slender and lighter blades, which are more prone to suffering from flutter [2]
The increased requirements for the flexibile operation of power plants employing steam turbines lead to off-design operation regimes, which often result in an onset of blade flutter [3]

Summary

Introduction

At present , the most important vibration problem faced by designers and operators of large-power turbomachines is blade aeroelastic instability called “blade flutter”—flowinduced oscillation of the turbine or compressor blades. These violent blade vibrations eventually lead to blade fractures with catastrophic consequences. Blade flutter problems started to appear with increasing frequency in high-efficiency power-generating turbines with slender and lighter blades, which are more prone to suffering from flutter [2]. The increased requirements for the flexibile operation of power plants employing steam turbines lead to off-design operation regimes, which often result in an onset of blade flutter [3]. It was reported that 90% of the potential flutter and high-cycle fatigue problems are covered during development testing, the remaining few problems account for nearly 30% of the total development cost and are responsible for over 25% of all engine distress events [4]

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