Turbomachinery Aeroelasticity Using a Time-Linearised Multi Blade-row Approach

In turbomachinery, the continuous drive towards low weight and improved efficiency has led to the design of slender and lighter blades, resulting in higher stress levels and aeroelasticity interactions on blades. Consequently, fast and accurate predictions of turbomachinery aeroelasticity phenomena are essential to modern aero-engine design. Current prediction methods can be divided into three main categories: classical, nonlinear time-accurate,and harmonic. Classical methods work with simplified geometries and simplified flow conditions, and are therefore not reliable for design. Nonlinear time-accurate methods are usually accurate, but they demand too much computational effort to be used for design in the foreseeable future. Harmonic methods currently meet design efficiency requirements, but they can still lack accuracy in real turbomachinery applications. Several research works suggest that one of the reasons for this is that most current methods ignore potentially important multi blade-row effects. . In this thesis, a harmonic Iinearised solver for the computation of multi-stage unsteady turbomachinery flows was developed. Blade-row interactions were represented using the theory of spinning modes. The new method uses either the 3-D Euler or Navier-Stokes equations and is well suited to the computation of flutter and forced response. Efficient solutions were obtained thanks to the use of state-of-the-art acceleration techniques, such as local Jacobi. preconditioner, multigrid, and GMRES. The method uses modern 3-D nonreflective boundary conditions, which use a wave-splitting method to minimise numerical reflections at the far-field boundaries. It also uses a novel inter-row boundary condition, based on the same wave-splitting method, to transfer waves between blade-rows. The new method was first tested for stator-rotor interaction and flutter on both simplified. geometries and flow conditions; results showed excellent agreement with the reference solutions. The method was then validated on industrial turbine configurations. Results were compared with nonlinear time-accurate unsteady solutions and experimental data and showed good agreement. It was demonstrated that multi-blade-row effects on the----. aerodynamic damping and the modal force of the vibrating blade-row are significant. The new method is also very efficient; large gains in computing time were obtained compared to ) fully nonlinear time-accurate methods.EThOS - Electronic Theses Online ServiceGBUnited Kingdo