Optimization-Aided Forced Response Analysis of a Mistuned Compressor Blisk

Abstract

The forced response of the first rotor of an engine 3E (technology program) (ESE)-type high pressure compressor (HPC) blisk is analyzed with regard to varying mistuning, varying engine order (EO) excitations and the consideration of aero-elastic effects. For that purpose, subset of nominal system modes (SNM)-based reduced order models are used in which the disk remains unchanged while the Young's modulus of each blade is used to define experimentally adjusted as well as intentional mistuning patterns. The aer odynamic influence coefficient (AIC) technique is employed to model aero-elastic interac tions. Furthermore, based on optimization analyses and depending on the exciting EO and aerodynamic influences it is searched for the worst as well as the best mistuning dis tributions with respect to the maximum blade displacement. Genetic algorithms using blade stiffness variations as vector o f design variables and the maximum blade displace ment as objective function are applied. An allowed limit of the blades' Young's modulus standard deviation is formulated as secondary condition. In particular, the question is addressed if and how far the aero-elastic impact, mainly causing aerodynamic damping, combined with mistuning can even yield a reduction of the forced response compared to the ideally tuned blisk. It is shown that the strong dependence of the aerodynamic damp ing on the interblade phase angle is the main driver for a possible response attenuation considering the fundamental blade mode. The results of the optimization analyses are compared to the forced response due to real, experimentally determined frequency mis tuning as well as intentional mistuning. Journal of Engineering for Gas Turbines and PowerJ o u rn a l o f E n g in e erin g fo r G as T u rb in es and Pow er JANUARY 2015, Vol. 137 / 0 12 50 4-9

Exploration of blade detuning tests for mistuning identification of blisks

“…Similar observations can also be found in [14], where the blade participation in a blisk modes is quantified by the blade percentage of the total blisk modal strain energy. Excellent correlation is achieved between the coupling index and the modal strain energy analysis in terms of blisk mode classification.…”

“…This procedure basically works as a model updating strategy. It relies on the simulations of the experimental process and on the iterative update of the blade stiffness parameters based on either a mass-spring-damper blisk model [12] or a full finite element blisk model [13] or even a reduced order blisk model [14]. More recently in [15], it was numerically highlighted that inter-blade coupling is responsible for the inaccurate blade mistuning identification through blade detuning tests.…”

Model update and validation of a mistuned high-pressure compressor blisk

“…Petrov and Ewins ( 5 ) used optimisation algorithms to find the worst forced response of bladed disks in terms of academic studies. Similar objectives have been addressed in Refs 6 and 7. However, the majority of publications were considering measured or preset mistuning patterns, yielding magnification factors from 1 to hardly greater than 2 as exemplarily reported in Ref.…”

Dynamic Characteristics Analysis of Bladed Disk Turbomachines Based on Intentional Mistuning

“…Известно, что конструкции облопаченных дисков претерпевают сильное увеличение динамического отклика из-за расстройки параметров в сочетании с низким уровнем структурного демпфирования. Негативные эффекты расстройки параметров в отношении вынуж-денного отклика облопаченных дисков более 50 лет были предметом интенсивных исследований многих авторов [1][2][3][4].…”