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Research Paper: Gas Turbines: Structures and Dynamics

Optimization of Intentional Mistuning Patterns for the Mitigation of the Effects of Random Mistuning

[+] Author and Article Information
Yun Han

Mem. ASME
SEMTE,
Faculties of Mechanical
and Aerospace Engineering,
Arizona State University,
Tempe, AZ 85287-6106
e-mail: yunhan@gmail.com

Raghavendra Murthy

Mem. ASME
SEMTE,
Faculties of Mechanical
and Aerospace Engineering,
Arizona State University,
Tempe, AZ 85287-6106
e-mail: rnmurthy@asu.edu

Marc P. Mignolet

Fellow ASME
SEMTE,
Faculties of Mechanical
and Aerospace Engineering,
Arizona State University,
Tempe, AZ 85287-6106
e-mail: marc.mignolet@asu.edu

Jeff Lentz

Department 93-34/301-134,
Honeywell Aerospace,
P.O. Box 52181,
Phoenix, AZ 85072-2181
e-mail: jeff.lentz@honeywell.com

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received November 3, 2013; final manuscript received November 30, 2013; published online February 11, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 136(6), 062505 (Feb 11, 2014) (9 pages) Paper No: GTP-13-1395; doi: 10.1115/1.4026141 History: Received November 03, 2013; Revised November 30, 2013

This paper focuses on the optimization of intentional mistuning patterns for the reduction of the sensitivity of the forced response of bladed disks to random mistuning. Intentional mistuning is achieved here by using two different blade types (denoted as A and B) around the disk. It is thus desired to find the arrangement of these A and B blades (A/B pattern) that leads to the smallest 99th percentile of the amplitude of blade response in the presence of random mistuning. It is first demonstrated that there usually is a large number of local minima and further that the cost of a function evaluation is high. Accordingly, two novel, dedicated optimization algorithms are formulated and validated to address this specific problem. Both algorithms proceed in a two-step fashion. The first step, which consists of an optimization in a reduced space, leads to a series of good initial guesses. A local search from these initial guesses forms the second step of the methods. A detailed validation effort of this new procedure was next achieved on a single-degree-of-freedom-per-blade model, a reduced order model of a blisk, and that of an impeller considered in an earlier study. In all validation cases, the two novel algorithms were found to converge to the global optimum or very close to it at a small computational cost. Finally, the results of these optimization efforts further demonstrate the value of intentional mistuning to increase the robustness of bladed disks to random mistuning.

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Figures

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Fig. 1

Single-degree-of-freedom-per-blade bladed disk model (all mj are equal)

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Fig. 2

Ninety-ninth percentile of the maximum amplification factor of the forced response with respect to the tuned disk as a function of the level of random mistuning, single-degree-of-freedom-per-blade model in Fig. 1, kC = 16,000 N/m. Blades A and B have natural frequencies 5% lower and higher than the tuned blade, respectively, 17 bladed disk.

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Fig. 3

Ninety-ninth percentile of the maximum amplification factor of the forced response with respect to the tuned disk as a function of the level of random mistuning, single-degree-of-freedom-per-blade model in Fig. 1, kC = 8606 N/m. Blades A and B have natural frequencies 5% lower and higher than the tuned blade, respectively, 18 bladed disk.

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Fig. 4

Ninety-ninth percentile of the maximum amplification factor of the forced response with respect to the tuned disk as a function of the level of random mistuning, single-degree-of-freedom-per-blade model in Fig. 1, kC = 45,430 N/m. Blades A and B have natural frequencies 5% lower and higher than the tuned blade, respectively, 18 bladed disk.

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Fig. 5

Blisk example: (a) blisk view, (b) blade-sector finite element mesh, and (c) natural frequencies versus nodal diameter plot

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Fig. 6

Single sector finite element model of the 17-blade centrifugal compressor rotor

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Fig. 7

Natural frequency versus nodal diameter plot of 17-blade impeller showing the frequency range of the excitation in 14th engine order

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Fig. 8

Ninety-fifth percentile of the amplification factor as a function of the standard deviation of stiffness mistuning, 17-blade impellers with tuned and optimum intentionally mistuned patterns obtained without (circle symbols) and with (square symbols) random mistuning

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