We propose a new feedback controller architecture. The distinguished feature of our new controller architecture is that it shows structurally how the controller design for performance and robustness may be done separately which has the potential to overcome the conflict between performance and robustness in the traditional feedback framework. The controller architecture includes two parts: one part for performance and the other part for robustness. The controller architecture works in such a way that the feedback control system can be solely controlled by the performance controller when there is no model uncertainties and external disturbances and the robustification controller can only be active when there are model uncertainties or external disturbances.

A new controller architecture for high performance, robust, and fault-tolerant control

The current paper describes the development of pressure-sensitive paint (PSP) technology as an advanced measurement technique for unsteady flow fields and short-duration wind tunnels. Newly developed paint formulations have step response times approaching 1 μs, making them suitable for a wide range of unsteady testing. Developments in binder technology are discussed, which have resulted in new binder formulations such as anodized aluminium, thin-layer chromatography plate, polymer/ceramic, and poly(TMSP) PSP. The current paper also details modeling work done to describe the gas diffusion properties within the paint binder and understand the limitations of the paint response characteristics. Various dynamic calibration techniques for PSP are discussed, along with summaries of typical response times. A review of unsteady and high-speed PSP applications is presented, including experiments with shock tubes, hypersonic tunnels, unsteady delta wing aerodynamics, fluidic oscillator flows, Hartmann tube o...

https://journals.sagepub.com/doi/pdf/10.1243/09544100JAERO243

A review of pressure-sensitive paint for high-speed and unsteady aerodynamics

The literature on reduced-order modeling, simulation, and analysis of the vibration of bladed disks found in gas-turbine engines is reviewed. Applications to system identification and design are also considered. In selectively surveying the literature, an emphasis is placed on key developments in the last decade that have enabled better prediction and understanding of the forced response of mistuned bladed disks, especially with respect to assessing and mitigating the harmful impact of mistuning on blade vibration, stress increases, and attendant high cycle fatigue. Important developments and emerging directions in this research area are highlighted.

/pdf/modeling-and-analysis-of-mistuned-bladed-disk-vibration-380rrehfek.pdf

Modeling and Analysis of Mistuned Bladed Disk Vibration: Status and Emerging Directions

This paper presents an in-depth study of blade vibration problems that seriously impact development of advanced gas turbine configurations. The motivation for this study arises from the author's conviction that structural integrity of power plants is the dominant factor that influences the quality, reliability, and marketability of the product. Implications of this study in the context of potential R&D challenges and opportunities of interest to industry, governments, and academia are discussed.

Flutter and Resonant Vibration Characteristics of Engine Blades

Applications of the unsteady vortex-lattice method in aircraft aeroelasticity and flight dynamics

A mathematical model is developed to predict the suppression of rotating stall in a centrifugal compressor with a vaned diffuser. This model is based on the employment of a control vortical waveform generated upstream of the impeller inlet to damp weak potential disturbances that are the early stages of rotating stall. The control system is analyzed by matching the perturbation pressure in the compressor inlet and exit e owe elds with a model for the unsteady behavior of the compressor. The model was effective at predicting the stalling behavior of the Purdue Low-Speed Centrifugal Compressor for two distinctly different stall patterns. Predictions made for the effect of a controlled inlet vorticity wave on thestability of the compressorshowthat, for minimum controlwave magnitudes, on the order of the total inlet disturbance magnitude, signie cant damping of the instability can be achieved. For control wave amplitudes of sufe cient amplitude, the control phase angle appears to be the most important factor in maintaining a stable condition in the compressor.

Prediction of Active Control of Subsonic Centrifugal Compressor Rotating Stall

The unsteady flowfield through a harmonically oscillating cascade of airfoils is investigated using a timemarching Euler code implemented on a deforming C-grid. Various methods of calculating the boundary conditions are considered, with special attention paid to the unsteady periodic boundary conditions and reducing computer resource requirements. The Euler code is then used to predict the unsteady aerodynamics for both translational and torsional cascade oscillations for several cascade flow geometries. A flat plate cascade is used to verify the flow solver with linear theory predictions. A typical compressor rotor configuration is used to introduce nonlinear effects. The effect of a strong normal shock with varied amplitudes of oscillation demonstrates the nonlinear behavior of the periodic boundary conditions and helps to define the limiting conditions for linearized analyses.

Single-passage Euler analysis of oscillating cascade aerodynamics for arbitrary interblade phase

High-density instantaneous and rotor phase-locked velocity field measurements are made in the centrifugal compressor diffuser vaneless space by means of the particle image velocimetry technique. The technique is challenged in this application by a small length scale and large velocities yielding very small flow time scales and demanding the use of extremely small flow tracking particles. The experiments reveal a detailed picture of the rotor phase-lockedaverageimpellerexitanddiffuserinlet flowfieldasisusefulforunsteady flowmodeling.Strongpassage velocity gradients exist across the vaneless space up to the diffuser vanes, showing that the phase-locked averaged impeller exit flow presents a highly unsteady non-mixed-out velocity field for the downstream vane row. This unsteady vane intake is thus characterized by a strong fluctuation in incidence angle with the passing blade event. Measured time variation in the velocity field indicates a significant time-varying potential field due to incidence fluctuations. Nomenclature Rduct = inlet duct radius r = radius � = radius ratio (diffuser leading-edge radius/impeller tip radius) � = 1 standard deviation

Particle Image Velocimetry Characterization of High-Speed Centrifugal Compressor Impeller-Diffuser Interaction

Blade row interactions affect compressor performance and durability. As design systems expand to account for these interactions, a better understanding of the underlying physics is necessary. In this paper, results from a vane clocking experiment in a three-stage compressor are discussed. Efforts are focused on the second stage, specifically the change in stator 2 wake profiles with respect to the placement of the stator 1 wake. The two clocking conditions presented position the wake from stator 1 at the leading edge of stator 2 and in the middle of the stator 2 passage. The time-accurate data are Fourier decomposed to determine the relative magnitudes of the frequencies in the spectrum. With data acquired at 50 circumferential locations spanning one vane passage for each clocking configuration, an enormous amount of data is collected, and a useful method for synthesizing this information is presented. Results show that, by placing the stator 1 wake at the leading edge of stator 2, the stator 2 boundary-layer response to the large incidence variations associated with the rotor 2 wakes is dampened, resulting in a thinner and more shallow stator 2 wake.

Sanford Fleeter

Papers

Prediction of Active Control of Subsonic Centrifugal Compressor Rotating Stall

Single-passage Euler analysis of oscillating cascade aerodynamics for arbitrary interblade phase

Particle Image Velocimetry Characterization of High-Speed Centrifugal Compressor Impeller-Diffuser Interaction

Vane Clocking in a Three-Stage Compressor: Frequency Domain Data Analysis

Inlet guide vane wakes including rotor effects