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.

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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 series of experiments are performed to investigate and quantify the design and off-design three-dimensional mean flow in a centrifugal compressor impeller. The experiments entail the acquisition and analysis of LDV data in the impeller passages of a low speed research mixed-flow compressor operating at its design point and at a point near the inception of rotating stall. The LDV data at both operating points show regions near the impeller exit with a significant velocity deficit on the shroud surface characteristic of the traditional jet-wake structure observed in many centrifugal compressors. At design, the maximum velocity deficit occurs at a location 70% of the passage width from the pressure to the suction surface. At the incipient stall point, the maximum velocity deficit occurs in the shroud suction surface corner, with the data indicating reverse flow.Copyright © 1991 by ASME

Ldv measurements of a mixed-flow impeller at design and near stall

An efficient diffuser is essential for the performance, durability and operability of modern high-speed centrifugal compressor stages. The diffuser entry flow is highly unsteady and complex; featuring shocks, boundary layer/shock interactions, and large incidence variations imposed on the diffuser vanes. The flow structures not only are unsteady but also are strongly dependent on the steady compressor stage loading. To characterize the variation in diffuser flow at different operating points of a high-speed transonic centrifugal compressor, Particle Image Velocimetry experiments are conducted in the Purdue High Speed Centrifugal Compressor facility. The data at all loading conditions demonstrate that the flow field in the diffuser is characterized by a much more complicated structure than that which would be associated with steady, uniform diffusion. The semivaneless space acceleration region’s size is shown to be weakly dependent on loading, where as the diffuser throat structures are strong functions of the loading condition.

PIV Investigation of a High-Speed Centrifugal Compressor Diffuser: Mid-Span Loading Effects

: This report describes the experimental investigation of a linear stationary supersonic compressor cascade incorporating splitter vanes, blades of constant spanwise geometry, and contoured sidewalls. Previous experimental studies of this cascade showed that the cascade performance concurred with the modeled rotor data and that the splitter vane location and/or shape was not optimal. Hence, the overall objective of this program was to experimentally determine if a preferred circumferential position for the splitter vane existed. This was accomplished by modifying the original cascade hardware to permit the splitter vanes to be moved in the equivalent circumferential direction with respect to the principal blades. The aerodynamic characteristics of the cascade were then experimentally determined at 41 test conditions. These covered a range of static pressure ratios between 1.6 and the spill point at the design inlet Mach number, for each of eight splitter vane locations, one of which was the original 50 percent spacing location. (Author)

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA043860&Location=U2&doc=GetTRDoc.pdf

The Effect of Splitter Vane Circumferential Location on the Aerodynamic Performance of a Supersonic Compressor Cascade.

Splitter blades as a passive control technique for flow induced vibrations is investigated by developing an unsteady aerodynamic model to predict the effect of incorporating splitter blades into the design of an axial flow blade row operating in an incompressible flow field. The splitter blades, positioned circumferentially in the flow passage between two principal blades, introduce aerodynamic and/or combined aerodynamic-structural detuning into the rotor. The unsteady aerodynamic gust response and resulting oscillating cascade unsteady aerodynamics, including steady loading effects, are determined by developing a complete first-order unsteady aerodynamic analysis together with an unsteady aerodynamic influence coefficient technique. The torsion mode flow induced vibrational response of both uniformly spaced tuned rotors and detuned rotors are then predicted by incorporating the unsteady aerodynamic influence coefficients into a single-degree-of-freedom aeroelastic model. This model is then utilized to demonstrate that incorporating splitters into axial flow rotor designs is beneficial with regard to flow induced vibrations. NOMENCLATURE

/pdf/passive-control-of-flow-induced-vibrations-by-splitter-1rct8fdak5.pdf

Sanford Fleeter

Papers

Ldv measurements of a mixed-flow impeller at design and near stall

PIV Investigation of a High-Speed Centrifugal Compressor Diffuser: Mid-Span Loading Effects

The Effect of Splitter Vane Circumferential Location on the Aerodynamic Performance of a Supersonic Compressor Cascade.

Passive Control of Flow Induced Vibrations by Splitter Blades

Forcing function generator fluid dynamic effects on compressor bladegust response