Automated dynamic optimization of the blades of the gas turbine engines

Аuthors

Melnikova G. V.¹, Shorr B. F.^1*, Sal'nikov A. V.^1**, Nigmatullin R. Z.^2***

1. Central Institute of Aviation Motors named after P.I. Baranov, CIAM, 2, Aviamotornaya str., Moscow, 111116, Russia
2. Central Institute of Aviation Motors, CIAM, 2, Aviamotornaya St., Moscow, 111116, Russia

*e-mail: shorr@ciam.ru
**e-mail: salnikov@ciam.ru
***e-mail: nigmarz@ciam.ru

Abstract

This paper is about the method of turbo machinery blades dynamic optimization. The method allows receiving the necessary dynamic characteristics of the blades taking into account long-term static strength and requirements of gas dynamics and structural constraints.
For optimization the special software is developed using programming language APDL in ANSYS. The software automates all modification processes of the original blades structure and includes a procedure for the automatic transfer of quasi-3D model cross-sections point coordinates to the 3D modal analysis ANSYS package and back. The process of blades dynamic optimization is performed using software LMS OPTIMUS. The optimization process is completed when all requirements to the structure are satisfied with a given accuracy.
The software allows performing the dynamic optimization of the blades as part of wheel taking into account shroud, interlock and disk. As the variable parameters of a blade airfoil, chords, maximum thickness, global coordinates of the mass centers and setting angles of the blade cross sections are used. Cross sections point coordinates are obtained for each of optimization iteration according to varying parameter. Two automated methods of the blade dynamic optimization are proposed. The first way assumes calculation of influence factors determining the section parameters change against the frequency (or several frequencies) change. Basing on the analysis of the influence factors their optimal combination is obtained. This approach takes a little time (a few hours). The second way is to use the standard methods of multi-criteria optimization, realized in the package LMS OPTIMUS. Therefore, the time of the optimal design obtaining significantly increases (several days) but the quality of the optimal design becomes better. The example of typical blades dynamic optimization using both approaches is performed. The original blade has a small margin (<2.8%) in relation to the possible resonance of the first oscillation mode with the harmonic k = 4 to the rotation frequency. By optimization using the first method the margin increases to 10% and the blade mass grows by 8.2%. The second optimization method leads to the margin increase to 9.8% but the mass grows only by 4%. The use of the proposed methods and modern software packages for multi-criterion optimization allows to automate a process of the blades dynamic optimization, reduce the time and laboriousness of the design process, and improve the quality of the designed wheel units.

Keywords:

dynamic optimization, blade, blade airfoil natural frequencies, stresses, resonance

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