Below are technical summaries of current GUIde 5 Consortium projects.
Grand Challenges in Turbomachinery Forced Response and Non-Synchronous Vibration (NSV)
Robert Kielb, Ph.D., & Kenneth C. Hall, Ph.D., Duke University
Nicole Key, Ph.D., Purdue University
Duke and Purdue Universities have joined forces to propose a comprehensive experimental and computational program for GUIde 5. It is a combined experimental and computational approach to address “Grand Challenges” research topics. This combined approach will enable better test planning, better interpretation of the measurements, and improved confidence in the modeling. This work addresses three areas of high interest to the industrial members: Unsteady Aerodynamics, Low Order Excitations and Test Rig Development. Following is a detailed description.
This effort addresses a number of sub-topics in the area of Unsteady Aerodynamics. First is an experimental/ computational effort to explore higher order modes in the multistage high-speed compressor at Purdue University. We are using a combined experimental/computational approach to address three Low Order Excitation topics:
(1) Distortion - To address inlet distortion effects including boundary layer ingestion, a flow field distortion will be introduced at the inlet of the compressor.
(2) Asymmetry - This will be addressed by the design and fabrication of an additional Stator 1 ring where asymmetries such as passage pitch variation are included.
(3) NSV - Benchmark data will be acquired for non-synchronous vibration (NSV) in the three-stage compressor.
Preliminary investigations suggest potential NSV phenomenon present in the facility as shown by pressure signals acquired from a casing-mounted pressure transducer just upstream of the leading edge of Rotor 1. Computational studies of cylinders and 2-D airfoils have been very useful in understanding the NSV lock-on phenomena. Excellent cylinder data is available, but not for a 2-D airfoil. Recently, an NSV study was conducted in the Duke University Wind Tunnel; results show a classical “V” shaped lock-on zone. We are extending this experimental study to help understand lock-on and determine the key parameters controlling lock-on and high amplitude limit cycle response. These experiments, compared with the numerical results obtained with MUSTANG, will give us insight about the flow mechanisms that trigger NSV. With respect to advanced computations, we are addressing rapid screening/design methods, CFD interpolation / extrapolation, and decreased run times by extending and improving Duke University's MUSTANG 2 software suite.
Modeling and Analysis of Nonlinear Damping and Mistuning Mechanisms in Rotating Systems
Bogdan Epureanu, Ph.D., University of Michigan
Among the most critical systems in aircraft are propulsion systems. Current and future propulsion systems include complex multistage rotating components that depend on computer aided design and analysis. Models used to capture system level effects must often make simplifying assumptions to produce a model that is computationally tractable. Therefore, systematic techniques to increase computational efficiency are required for predicting the structural dynamics (e.g., for performing free and forced response analyses). This proposal presents a plan to develop the next-generation of advanced reduced order models for predicting the dynamics of complex rotating systems with multiple forms of linear and nonlinear damping, small and large structural mistuning and multistage coupling. Capturing the physics is critical to reach this goal. In the proposed research, advanced structural dynamic modeling techniques will be developed for complex rotating systems and experimental testing will be performed to validate novel Coulomb friction modeling techniques.
In the past few years, significant progress has been made at the University of Michigan (UofM) in developing highly efficient modeling, simulation, and identification techniques for predicting the nonlinear vibration response of multistage systems, aeroelastic systems, and rotating systems with cracked blades. Advanced simulation codes have been developed at UofM, such as the code packages ROMA, VICTER, CID, and PRIME. Herein, an integrated approach which uniquely combines key scientific elements developed at UofM is proposed along with new and significant technological advancements.
The main goals are: (1) to model and predict the nonlinear vibration response of complex single (and multi-) stage rotating systems that contain Coulomb friction due to shroud-to-shroud dampers, platform dampers, and shroud interlocks (where the effective damper stiffness is important); (2) to create an efficient modeling tool for capturing the effects of nonlinear damping coatings on the vibration of complex rotating systems, including predicting the amplitude-dependent localization in their response caused by stiffness and damping mistuning these coatings introduce into the system; (3) to collect an experimental dataset to provide the contact parameters (friction coefficient, contact stiffness, microslip curves) to the computational tools and to validate the Coulomb friction model developed in this project; (4) to create an efficient integrated modeling framework that incorporates small stiffness and damping mistuning as well as large mistuning (large damping mistuning and/or damage) in multistage systems with the new modeling techniques for Coulomb friction damping and nonlinear damping coatings.
The proposed research will provide new capabilities for modeling the response of rotors with Coulomb friction and will develop novel, advanced techniques for integrating nonlinear damping coatings with stiffness and damping mistuning into efficient reduced order models (ROMs). Additionally, this effort will provide the necessary fundamental physical insight to understand, measure, and predict damping and the effective damper stiffness in mistuned bladed disks and blisks. Furthermore, the proposed research will provide fundamental progress in creating an efficient integrated modeling framework for generating novel fast nonlinear ROMs able to handle multiple forms of nonlinear damping and mistuning in single- and multi-stage turbomachinery.
Experimental Investigation of Airfoil Damping for an Excited Bladed Disk and a Blisk Operating at Engine Design Speed
Michael G. Dunn, Ph.D., & Kiran D'Souza, Ph.D., The Ohio State University
The Ohio State University's research is to embark upon a dedicated measurement program designed to investigate airfoil damping. This work entails efforts to verify computational tools developed for turbomachinery applications using measurements obtained from engine hardware operated at design speed. The experiments and modeling will be conducted on a newly designed blisk specifically developed for this research program. Experiments will be performed using an underground spin pit facility at the Gas Turbine Laboratory of OSU. These are aimed at identifying damping and mistuning properties of the rotor while it rotates within the facility. Light probe and strain gauge data will be collected to compare their effectiveness. The experimental effort enables the identification of key parameters used in a series of computational tools that have been developed recently. Computational models and tools with updated parameters can be verified against measurements by using them to predict the responses at different conditions. The computational tools include various mistuning and (nonlinear) damping identification methods that have not yet been verified using data obtained from rotating hardware. Computational models and reduced order models will be used in the verification.