Flutter, Forced Response, NSV, Mistuning, and System ID Computational Support for GUIde Experimental Projects
The Duke University research, similar to that of GUIde 5, provides computational support to GUIde Consortium-funded experimental efforts. This includes the Purdue University compressor experiments of GUIde 5, new experimental efforts of GUIde 6, and any other cases recommended by the Consortium’s Steering Committee. Duke will utilize its significant experience in computational flutter, forced response, NSV, mistuning and system identification. This effort is not to just predict responses to compare with experimental data, but will investigate the physics. As an example, forced response computations include three fundamental ingredients: (1) the forcing function, (2) damping (structural and aerodynamic) and (3) mistuned response. As shown in GUIde 5, if the errors in the three ingredients cancel out, you can get what appears to be excellent agreement with experimental data. Duke’s efforts directly addresses four research needs: (1) System Identification, (2) Forced Response, (3) Flutter, and (4) NSV/FSI.
Enhanced Physical Understanding of Forced Response, Inlet Distortion, and Blade Row Interactions in the Purdue 3-Stage Compressor
The GUIde 5 Consortium funded a joint effort between Purdue and Duke Universities to investigate forced response in the Purdue 3-stage axial compressor. During the project, several interesting questions arose that will be addressed in GUIde VI with additional experiments and computations aimed to enhance our physical understanding of the phenomena. Key improvements or new experiments motivated by GUIde V results include:
- Dual Plane NSMS Measurements, Higher Order Mode Strain Gage Measurements
- Strength of 44EO excitation of R1 1T Mode when S1 Count is Reduced to 38 and New IGV Count
- Non-Uniform Vane Spacing Strain Gage Measurements
- Spinning Mode Measurements to Support Harmonic Balancing
- Multistage Computations with Vane Clocking
- Inlet Distortion Experiments with Increased Distortion Levels
- Intentional Mistuning Experiments.
University of Michigan
Next Generation Dampers and Nonlinear Damping Identification
The research addresses: (a) Advanced Damping Development / Validation and (b) Friction Damping. The main theme of the proposed research is the integration of computational and experimental efforts for accurate and robust modeling of nonlinear mistuned blisk dynamics with contact at arbitrary interfaces, consequently enabling investigation into design for the next generation of blisk dampers. The main goal of the research is to develop adaptable and high-performance ROMs for blisks with contact interfaces which employ novel concepts in data-driven nonlinear system ID, and to deploy these ROMs to synthesize novel dynamic damping mechanisms and create next generation dampers. Computational modeling tools and experiments will be developed to create models for the prediction of multi-harmonic responses of mistuned nonlinear blisks and for data-driven ID of damping and mistuning due to contacts characterized by both frictional forces and impacts. These techniques will be used to design the next generation of advanced dampers by exploring concepts such as impulse mistuning and parametric resonance based damping. Experimentally collected data will be used for ID and validation of these computational models and advanced damper designs. Hence, the main tasks of the proposed research are to:
- Generate efficient inverse ROM formulations with sufficient adaptability and robustness to capture dominant effects in multi-harmonic dynamics exhibited by blisks with contact nonlinearities and mistuning represented directly in the reduced-order space;
- Develop advanced data-driven contact modeling and system ID methods for robust and accurate representation of the nonlinear damping and stiffness mistuning effects of contact at interfaces of arbitrary location and design;
- Create novel damping mechanisms based on (a) impulse mistuning, and (b) parametric resonance, and use the computational tools in items (1)-(2) to identify optimal blade and damper arrangements and validate designs for next generation blisk dampers; and
- Design and manufacture an adaptive experimental setup for bench tests on blisk-like and blade-like structures with nonlinear interfaces, and collect experimental datasets to validate of computational toolsets for modeling, system ID and damper design.
Leibniz Universitat Hannover
High Fidelity Experimental Investigations of Turbomachinery Aeroelasticity at the Institute of Turbomachinery and Fluid Dynamics
An experimental quantification of aerodynamic damping in the axial turbine is conducted in the course of the project AG Turbo-2020 “Acoustic excitation of blade vibrations in a rotating system. For that purpose, blisk vibrations are excited acoustically. The vibration amplitude is detected by a Tip Timing System. Based on the decay behavior, the aerodynamic damping can be determined. The acoustic excitation unit was developed and tested by Freund et al. (2013, 2014). Further investigations focusing on controlled blade excitation by piezo actuators were conducted in the low-speed axial compressor. The aim of the investigation was active vibration damping using actuators (Goltz et al., 2009; Siemann et al., 2009; Belz et al. 2013). In an ongoing research project mistuning effects on aerodynamically and structural mechanically linked blades are investigated.
In the 4-stage axial compressor of the TFD, non-synchronous vibrations are examined by Hellmich et al. (2008). Acoustic resonance is detected and investigated in detail. The results show a non-synchronous resonance propagating as a standing wave in the axial direction with three wavelengths along the circumference.