Rig and Engine Validation of the Nonlinear Forced Response Analysis Performed by the Tool OrAgL

Abstract

Since the first nonlinear forced response validation of frictionally coupled bladed disks, more than 20 years have passed, and numerous incremental modeling and simulation refinements were proposed. With the present work, we intend to assess how much we have improved since then. To this end, we present findings of an exhaustive validation campaign designed to systematically validate the nonlinear vibration prediction for the different friction joints at blade roots, interlocked shrouds and under-platform dampers. An original approach for the identification of crucial contact properties is developed. By using the dynamic Lagrangian contact formulation and a refined spatial contact discretization, it is demonstrated that the delicate identification of contact stiffness properties can be circumvented. The friction coefficient is measured in a separate test, and determined as unique function of temperature, preload, wear state. Rotating rig and engine measurements are compared against simulations with the tool OrAgL, developed jointly by the Leibniz Universität Hannover and the University of Stuttgart, in which state-of-the-art component mode synthesis (CMS) and harmonic balance methods (HBMs) are implemented.

Stress recovery algorithm for reduced order models of mechanical systems in nonlinear dynamic operative conditions

“…The design of real engineering structures often requires the generation of accurate FEMs with a high density of nodes. Nonlinear forced response analyses on such structures are usually carried out with in-house developed codes [2,[14][15][16], which operate on a limited number of DOFs in order to avoid the expensive computational costs typical of iterative solution methods (e.g. the Newton-Raphon method (NRM) [17]).…”

“…Finally, the Fourier coefficients of the contact forces are computed by using the Fast Fourier transform (FFT) and substituted into Eqn. 15.…”

“…For each stress map the location where the maximum stress occurs is circled in red Fig. 15 Evolution of the critical location at the blade airfoil for each nonlinear forced response. The colored circles denote stress concentration at specific airfoil locations: lower fillet (blue, critical location N 1 ), mid-airfoil (green, critical location N 2 ) and upper fillet (red, critical location N 3 ) the shape of the excited mode leads in general to a different location where the maximum Von Mises stress occurs.…”

Experimental Verification of the Dynamic Model of Turbine Blades Coupled by a Sealing Strip

“…Once the geometry of blades and disk have been defined, a possible solution to shift the natural frequencies and to introduce damping, is to insert friction contact surfaces between the different elements of the bladed disk. These friction contact surfaces can be between elements which are integral parts of the blades [1][2][3][4][5][6][7][8][9] such as shrouds or interlocked tip platforms, or, as an alternative, they can come from the contact with external devices such as underplatform dampers (UPDs) [10][11][12][13][14][15][16][17][18]. The UPDs are metal masses inserted between the blades, pushed against the blade platforms by the centrifugal force.…”