Aeroelasticity Research for Turbomachine Applications
01 May 1979-Journal of Aircraft (American Institute of Aeronautics and Astronautics (AIAA))-Vol. 16, Iss: 5, pp 320-326
TL;DR: An overview of the research effort, coordinated between industry, government, and universities, directed toward the development of phenomcnologically founded approaches to induced vibrations in turbomachines.
Abstract: The continuing demand for increased performance in turbine engine turbomachinery has aggravated dynamic problems in the various components, particularly the blading. These problems are generally classified into the categories of either flutter or forced response. Historically, the complexity of the flowfield necessitated the development of empirical flutter and forced-response design techniques. However, such empirical correlations have proven to be inadequate when extrapolated beyond past experience levels. Hence, current research effort, coordinated between industry, government, and universities, is directed toward the development of phenomcnologically founded approaches to these problems. Presented herein is an overview of this ajtack on aerodynamical!}' induced vibrations in turbomachines.
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TL;DR: In this article, the authors demonstrate that the field of aeroelasticity continues to play a critical role in the design of modern aerospace vehicles, and several important problems are still far from being well understood.
Abstract: The primary objective of this paper is to demonstrate that the field of aeroelasticity continues to play a critical role in the design of modern aerospace vehicles, and several important problems are still far from being well understood. Furthermore, the emergence of new technologies, such as the use of adaptive materials (sometimes denoted as smart structures technology), providing new actuator and sensor capabilities, has invigorated aeroelasticity, and generated a host of new and challenging research topics that can have a major impact on the design of a new generation of aerospace vehicles.
150 citations
TL;DR: In this paper, the authors present a survey of recent advances in the theoretical and computational modeling of turbomachinery unsteady flows through blade rows, including the use of Euler and Navier-Stokes simulations.
Abstract: Introduction T HE unsteady aerodynamic analyses intended for turbomachinery aeroelastic and aeroacoustic predictions must be applicable over wide ranges of blade-row geometries and operating conditions and unsteady excitation modes and frequencies. Also, because of the large number of controlling parameters involved, there is a stringent requirement for computational efficiency. To date these requirements have been met only to a limited extent. As a result, aeroelastic and aeroacoustic design predictions are, for the most part, still based on the classical linearized unsteady aerodynamic analyses developed in the early 1970s. During the past decade, significant advances in unsteady aerodynamic prediction capabilities have been achieved. In particular, researchers have developed efficient linearized analyses that account for the effects of important design features, such as real blade geometry, mean blade loading, and operation at transonic Mach numbers, on the unsteady aerodynamic response of the blading to imposed structural and external aerodynamic excitations. The improvements in physical modeling that such linearizations allow are motivating their current implementation into aeroelastic and aeroacoustic design prediction systems. Also, considerable progress has been made on developing time-accurate Euler and Navier-Stokes simulations of nonlinear unsteady flows through blade rows. Although not yet suitable for design use, such analyses offer opportunities for an improved understanding of the unsteady aerodynamic processes associated with blade vibration and noise generation. These recent advances in the theoretical and computational modeling of turbomachinery unsteady flows are reviewed in the present survey.
101 citations
01 Jan 1990
TL;DR: The paper reviews the areas of unsteady cascade flows, structural modeling, and flutter prediction methods, and recommends that future research include investigations of novel approaches to flutter calculations that can take full advantage of parallel processing supercomputers.
Abstract: A review of the field of turbomachinery aeroelasticity is presented. Developments over the past decade are emphasized, and an assessment of possible future directions of research is offered. The paper reviews the areas of unsteady cascade flows, structural modeling, and flutter prediction methods. Representative results for unsteady flow calculations and flutter boundary predictions in subsonic, transonic, and supersonic flows are discussed, including recent calculations based on the methods of computational fluid mechanics. Results from current attempts to correlate experimental data with theoretical predictions are discussed briefly. It is recommended that future research include investigations of novel approaches to flutter calculations that can take full advantage of parallel processing supercomputers. The feasibility of using mistuning and aeroelastic tailoring as passive flutter suppression techniques should also be pursued.
36 citations
TL;DR: A surrogate modeling approach is presented by absorbing the strength of particle swarm optimization (PSO) algorithm and least-squares support vector regression (LSSVR) to improve the computational efficiency of probabilistic flutter evaluation of compressor blade.
22 citations
01 Jan 1980
TL;DR: In this article, data relevant to several types of aeroelastic instabilities were obtained using both turbojet and turbofan engines in particular, data relative to separated flow (stall) flutter, choke flutter and system mode instabilities.
Abstract: Data relevant to several types of aeroelastic instabilities were obtained using several types of turbojet and turbofan engines In particular, data relative to separated flow (stall) flutter, choke flutter, and system mode instabilities are presented The unique characteristics of these instabilities are discussed, and a number of correlations are presented that help identify the nature of the phenomena
11 citations
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62 citations
TL;DR: In this article, the effects of compressibility on both the fluctuating lift and fluctuating moment coefficients for cascaded airfoils due to an upstream nonuniformity are determined by obtaining a solution to the time-dependent, compressible, two-dimensional partial differential equation which describes the perturbation velocity potential.
Abstract: The effects of compressibility on both the fluctuating lift and the fluctuating moment coefficients for cascaded airfoils due to an upstream nonuniformity are determined by obtaining a solution to the time-dependent, compressible, two-dimensional partial differential equation which describes the perturbation velocity potential. This is accomplished through an application of Fourier-trans form theory, with the resulting integral solution equation evaluated numerically by a matrix-inversion technique. The results presented show the variation in both the fluctuating lift and the fluctuating moment coefficients over the mean cascade inlet Mach number range of 0.0 (incompressible) to 0.9 with the cascade solidity, cascade stagger angle, interblade phase angle and reduced frequency as parameters.
59 citations
TL;DR: In this paper, an experimental technique is described which corroborates the predictions of several new analyses of the unsteady response of an airfoil to high frequency flow fluctuations and shows a chordwise variation of pressure phase angle which is not predicted by the incompressible analysis of Sears.
Abstract: An experimental technique is described which corroborates the predictions of several new analyses of the unsteady response of an airfoil to high frequency flow fluctuations. The periodically fluctuating flowfield was produced by the natural shedding of vortices from a transverse cylinder to yield a reduced frequency of 3.9 based on airfoil semichord. Unsteady pressure measurements were made on an instrumented airfoil mounted downstream and above the turbulent wake of the cylinder. These unsteady pressures were found to be in good agreement with current compressible theories and show a chordwise variation of pressure phase angle which is not predicted by the incompressible analysis of Sears. Large reductions of the unsteady lift and phase angle were also observed for large airfoil incidence angles.
49 citations
TL;DR: In this article, the authors present an analysis for determining the unsteady flowfield produced by an oscillating cascade placed in a supersonic stream which has a subsonic velocity component normal to the cascade.
Abstract: This paper presents an analysis for determining the unsteady flowfield produced by an oscillating cascade placed in a supersonic stream which has a subsonic velocity component normal to the cascade. The analysis is based on the assumptions of an inviscid, two dimensional, linearized flowfield. Solutions for the velocity potential and the blade pressure distributions which satisfy the blade-to-blade periodicity condition are developed explicitly in terms of disturbance functions distributed on blade and wake surfaces. The boundary conditions of flow tangency at blade surfaces and continuity of pressure across wake surfaces provide integral relations which can be solved numerically to evaluate the disturbance functions. Predicted blade pressure distributions are in good agreement with results determined from a previous finite cascade solution. Further, in the two limiting cases of sonic axial velocity and zero frequency, the present solution approaches the lower limit of Lane's solution for supersonic axial flow, and it reduces to an Ackeret type of steady-state solution, respectively. The numerical examples indicate that a single~degree- of-freedom torsional instability will exist over a broad range of cascade parameter values.
42 citations