The Effect of Interblade Phase Angle and Solidity on the Time-Variant Aerodynamic Response of a Compressor Stator.

1979 ◽  
Author(s):  
R. R. Allran
Keyword(s):  
Phase Angle ◽  
Interblade Phase Angle

scholarly journals Unsteady Gapwise Periodicity of Oscillating Cascaded Airfoils

1982 ◽  
Author(s):  
F. O. Carta
Keyword(s):  
Unsteady Flow ◽  
Fourier Coefficient ◽  
Phase Angle ◽  
Leading Edge ◽  
Experimental Measurements ◽  
Pressure Data ◽  
Linear Cascade ◽  
Aerodynamic Damping ◽  
The Stability ◽  
Interblade Phase Angle

Tests were conducted on a linear cascade of airfoils oscillating in pitch to measure the unsteady pressure response on selected blades along the leading edge plane of the cascade and over the chord of the center blade. The pressure data were reduced to Fourier coefficient form for direct comparison, and were also processed to yield integrated loads and, particularly, the aerodynamic damping coefficient. In addition, results from two unsteady theories for cascaded blades with nonzero thickness and camber were compared with the experimental measurements. The three primary results that emerged from this investigation were: (a) from the leading edge plane blade data, the cascade was judged to be periodic in unsteady flow over the range of parameters tested, (b) as before, the interblade phase angle was found to be the single most important parameter affecting the stability of the oscillating cascade blades, and (c) the real blade theory and the experiment were in excellent agreement for the several cases chosen for comparison.

scholarly journals Euler Solutions for Transonic Oscillating Cascade Flows Using Dynamic Triangular Meshes

1993 ◽  
Author(s):  
C. J. Hwang ◽  
S. Y. Yang
Keyword(s):  
Experimental Data ◽  
Phase Angle ◽  
Transonic Flow ◽  
Lift Coefficient ◽  
Pressure Coefficient ◽  
Oscillation Amplitude ◽  
Time History ◽  
Present Approach ◽  
Instantaneous Pressure ◽  
Interblade Phase Angle

The modified total-variation-diminishing scheme and an improved dynamic triangular mesh algorithm are presented to investigate the transonic oscillating cascade flows. In a Cartesian coordinate system, the unsteady Euler equations are solved. To validate the accuracy of the present approach, transonic flow around single NACA 0012 airfoil pitching harmonically about the quarter chord is computed first. The calculated instantaneous pressure coefficient distributions during a cycle of motion compare well with the related numerical and experimental data. To further evaluate the present approach involving nonzero interblade phase angle, the calculations of transonic flow around oscillating cascade of two unstaggered NACA 0006 blades with interblade phase angle equal to 180 deg are performed. From the instantaneous pressure coefficient distributions and time history of lift coefficient, the present approach, where a simple spatial treatment is utilized on the periodic boundaries, gives satisfactory results. By using the above solution procedure, transonic flows around oscillating cascade of four biconvex blades with different oscillation amplitudes, reduced frequencies and interblade phase angles are investigated. From the distributions of magnitude and phase angle of the dynamic pressure difference coefficient, the present numerical results show better agreement with the experimental data than those from the linearized theory in most of the cases. For every quarter of one cycle, the pressure contours repeat and proceed one pitch distance in the upward or downward direction for interblade phase angle equal to −90 deg or 90 deg, respectively. The unsteady pressure wave and shock behaviors are observed. From the lift coefficient distributions, it is further confirmed that the oscillation amplitude, interblade phase angle and reduced frequency all have significant effects on the transonic oscillating cascade flows.

Euler Solutions for Transonic Oscillating Cascade Flows Using Dynamic Triangular Meshes

1995 ◽  
Vol 117 (3) ◽  
pp. 393-400 ◽  
Author(s):  
C. J. Hwang ◽  
S. Y. Yang
Keyword(s):  
Experimental Data ◽  
Phase Angle ◽  
Transonic Flow ◽  
Lift Coefficient ◽  
Pressure Coefficient ◽  
Oscillation Amplitude ◽  
Time History ◽  
Present Approach ◽  
Instantaneous Pressure ◽  
Interblade Phase Angle

The modified total-variation-diminishing scheme and an improved dynamic triangular mesh algorithm are presented to investigate the transonic oscillating cascade flows. In a Cartesian coordinate system, the unsteady Euler equations are solved. To validate the accuracy of the present approach, transonic flow around a single NACA 0012 airfoil pitching harmonically about the quarter chord is computed first. The calculated instantaneous pressure coefficient distribution during a cycle of motion compare well with the related numerical and experimental data. To evaluate further the present approach involving nonzero interblade phase angle, the calculations of transonic flow around an oscillating cascade of two unstaggered NACA 0006 blades with interblade phase angle equal to 180 deg are performed. From the instantaneous pressure coefficient distributions and time history of lift coefficient, the present approach, where a simple spatial treatment is utilized on the periodic boundaries, gives satisfactory results. By using this solution procedure, transonic flows around an oscillating cascade of four biconvex blades with different oscillation amplitudes, reduced frequencies, and interblade phase angles are investigated. From the distributions of magnitude and phase angle of the dynamic pressure difference coefficient, the present numerical results show better agreement with the experimental data than those from the linearized theory in most of the cases. For every quarter of one cycle, the pressure contours repeat and proceed one pitch distance in the upward or downward direction for interblade phase angle equal to −90 deg or 90 deg, respectively. The unsteady pressure wave and shock behaviors are observed. From the lift coefficient distributions, it is further confirmed that the oscillation amplitude, interblade phase angle, and reduced frequency all have significant effects on the transonic oscillating cascade flows.

Effect of Shock Wave Movement on Aerodynamic Instability of Annular Cascade Oscillating in Transonic Flow

1988 ◽  
Author(s):  
Hiroshi Kobayashi
Keyword(s):  
Shock Wave ◽  
Phase Angle ◽  
Test Facility ◽  
Blade Surface ◽  
Compressor Cascade ◽  
Reduced Frequency ◽  
Wide Range ◽  
Cascade Flutter ◽  
Annular Cascade ◽  
Interblade Phase Angle

Effects attributable to shock wave movement on cascade flutter were examined for both turbine and compressor blade rows, using a controlled-oscillating annular cascade test facility and a method for accurately measuring time-variant pressures on blade surfaces. Nature of the effects and blade surface extent influenced by the shock movement were clarified in a wide range of Mach number, reduced frequency and interblade phase angle. Remarkable unsteady aerodynamic force was generated by the shock movement and it significantly affected the occurrence of compressor cascade flutter as well as turbine one. For turbine cascade the interblade phase angle remarkably controlled the effect of the force, while for compressor one the reduced frequency dominated it. The chordwise extent on blade surface influenced by the shock movement was suggested to be about 6% chord length.

Development of a Multi-Shaker-Control to Investigate the Influence of the Interblade Phase Angle on Frictionally Damped Turbine Blades

2021 ◽  
Author(s):  
Florian Jäger ◽  
Ferhat Kaptan ◽  
Lars Panning-Von Scheidt ◽  
Jörg Wallaschek
Keyword(s):  
Phase Angle ◽  
Phase Difference ◽  
Degrees Of Freedom ◽  
Turbine Blades ◽  
Mode Shapes ◽  
Nodal Diameter ◽  
Cyclic Symmetric ◽  
Symmetric Structures ◽  
Interblade Phase Angle ◽  
Experimental Effort

Abstract Constructive damper concepts are developed and integrated in turbomachinery to reduce vibration amplitudes generated by dynamic loads. The potential damping effectiveness of friction-based damper concepts is strongly dependent on the relative motion between adjacent blades, besides other factors such as normal force. In cyclic symmetric structures the phase difference is determined by the excited nodal diameter, which leads to different damper movements and efficiencies for given mode shapes. Several studies on the investigation of the damper performance of different underplatform damper geometries have been carried out on non-rotating test stands consisting usually of two blades in order to reduce the experimental effort before setting up rotational tests. Based on the existing modes of the two blades and the application of commonly just one shaker, the investigations are limited to the in-phase and out-of-phase modes. In this paper an experimental approach is developed to reduce the gap of transferability between non-rotating and rotational tests to analyze the effects of a variable interblade phase angle on the damping effect of underplatform dampers. For this purpose, a cascaded control system using two shakers is being developed to control the force amplitudes and the phase difference between the response of the two blades. The control algorithm is designed in a model-based way by using a two degrees of freedom oscillator with friction contact and is subsequently integrated in the non-rotating test stand.

An Experimental Determination of the Unsteady Aerodynamics in a Controlled Oscillating Cascade

1977 ◽  
Vol 99 (1) ◽  
pp. 88-96 ◽  
Author(s):  
S. Fleeter ◽  
A. S. Novick ◽  
R. E. Riffel ◽  
J. E. Caruthers
Keyword(s):  
Phase Angle ◽  
Unsteady Aerodynamics ◽  
Time Dependent ◽  
Phase Lag ◽  
Reduced Frequency ◽  
On Line ◽  
Torsional Frequency ◽  
Airfoil Cascade ◽  
Interblade Phase Angle

A unique supersonic inlet flow field unsteady cascade experiment is described wherein the time-dependent pressure distribution within an harmonically oscillating airfoil cascade is quantitatively determined. The torsional frequency of oscillation and the inter-blade phase angle are precisely controlled by means of on-line digital computers. The dynamic data obtained include the chordwise distribution of the unsteady pressure magnitude and its phase lag as referenced to the airfoil motion. Parameters varied include the cascade inlet Mach number, the interblade phase angle, and the reduced frequency. The time-dependent data are correlated with state-of-the-art analytical predictions.

scholarly journals The Aerodynamics of an Oscillating Cascade in a Compressible Flow Field

1989 ◽  
Author(s):  
Daniel H. Buffum ◽  
Sanford Fleeter
Keyword(s):  
Phase Angle ◽  
Incidence Angle ◽  
Major Effect ◽  
Nasa Lewis Research ◽  
Airfoil Surface ◽  
Torsion Mode ◽  
Unique Data ◽  
Reduced Frequency ◽  
Airfoil Cascade ◽  
Interblade Phase Angle

Fundamental experiments are performed in the NASA Lewis Research Center Transonic Oscillating Cascade Facility to investigate and quantify the aerodynamics of a cascade of biconvex airfoils executing torsion mode oscillations at realistic reduced frequency values. Both steady and unsteady airfoil surface pressures are measured at two inlet Mach numbers, 0.65 and 0.80, and two incidence angles, 0 and 7 degrees, with the harmonic torsional airfoil cascade oscillations at realistic high reduced frequency and unsteady data obtained at several interblade phase angle values. The time-variant pressures are analyzed by means of discrete Fourier transform techniques, with these unique data compared with predictions from a linearized unsteady cascade model. The experimental results indicate that the interblade phase angle has a major effect on the chordwise distributions of the airfoil surface unsteady pressure, with the effects of reduced frequency, incidence angle, and Mach number somewhat less significant.

scholarly journals Numerical Investigation of Unsteady Subsonic Compressible Flows Through an Oscillating Cascade

1986 ◽  
Author(s):  
T. H. Fransson ◽  
M. Pandolfi
Keyword(s):  
Phase Angle ◽  
Compressible Flows ◽  
Subsonic Flow ◽  
Aerodynamic Force ◽  
Plate Theory ◽  
Time Dependent ◽  
Periodicity Condition ◽  
Damping Coefficients ◽  
Flow Through ◽  
Interblade Phase Angle

A method for solving numerically the fully time-dependent two-dimensional Euler equations, applied to unsteady subsonic flow through vibrating turbomachine cascades with thin blades, is developed. The blades are assumed to vibrate at a constant interblade phase angle and the computed region is reduced to one blade passage, with the implementation of the interblade phase angle as a periodicity condition. The reliability of the method is validated by comparing it with an analytical flat plate theory, and the importance of radiative inlet and outlet boundary conditions for unsteady flow calculations is shown in an example. The method can be used to compute the aerodynamic force and damping coefficients acting on the blades and to investigate the propagation of unsteady disturbances through a cascade in flutter conditions.

scholarly journals Aerodynamic Force and Moment on Oscillating Airfoils in Cascade

1978 ◽  
Author(s):  
H. Atassi ◽  
T. J. Akai
Keyword(s):  
Integral Equations ◽  
Phase Angle ◽  
Singular Integral ◽  
Incompressible Flow ◽  
Significant Influence ◽  
Aerodynamic Force ◽  
Singular Integral Equations ◽  
Mean Flow ◽  
The Mean ◽  
Interblade Phase Angle

A systematic theory is developed for airfoils in cascade oscillating about their mean position with constant interblade phase angle in a uniform incompressible flow. The theory fully accounts for the effect of angle of attack of the mean flow, the airfoils’ thickness and camber, and the cascade solidity and stagger. The formulation leads to two singular integral equations in the complex plane which are solved numerically by collocation. The results show that for certain values of the interblade phase angle, the airfoils’ thickness and incidence have a significant influence on the unsteady lift and moment particularly for staggered cascades.

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