scholarly journals Supersonic Stall Flutter of High-Speed Fans

1982 ◽  
Vol 104 (3) ◽  
pp. 675-682 ◽  
Author(s):  
J. J. Adamczyk ◽  
W. Stevans ◽  
R. Jutras
Keyword(s):  
Dynamic Response ◽  
Rotor Blade ◽  
High Speed ◽  
Aerodynamic Force ◽  
Rotor System ◽  
Flexural Mode ◽  
Disk Model ◽  
Actuator Disk ◽  
Blade Row ◽  
Flutter Boundary

An analytical model is developed for predicting the onset of supersonic stall bending flutter in axial-flow compressors. The analysis is based on a modified two-dimensional, compressible, unsteady actuator disk theory. It is applied to a rotor blade row by considering a cascade of airfoils whose geometry and dynamic response coincide with those of a rotor blade element at 85 percent of the span height (measured from the hub). The rotor blades are assumed to be unshrouded (i.e., free standing) and to vibrate in their first flexural mode. The effects of shock waves and flow separation are included in the model through quasisteady, empirical, rotor total-pressure-loss and deviation-angle correlations. The actuator disk model predicts the unsteady aerodynamic force acting on the cascade blading as a function of the steady flow field entering the cascade and the geometry and dynamic response of the cascade. Calculations show that the present model predicts the existence of a bending flutter mode at supersonic inlet Mach numbers. This flutter mode is suppressed by increasing the reduced frequency of the system or by reducing the steady-state aerodynamic loading on the cascade. The validity of the model for predicting flutter is demonstrated by correlating the measured flutter boundary of a high-speed fan stage with its predicted boundary. This correlation uses a level of damping for the blade row (i.e., the log decrement of the rotor system) that is estimated from the experimental flutter data. The predicted flutter boundary is shown to be in good agreement with the measured boundary. These results show that the model can be used to estimate the relative stability between operating points of a given rotor system. If, in addition, a measure of the mechanical damping of the rotor system is available, the model can also be used to estimate the absolute stability at an operating point.

Dynamic Response of the Vertical Rotor System to Base Excitation

2008 ◽  
Author(s):  
Jianli Zuo ◽  
Jianjun Wu ◽  
Ping Li ◽  
Shenjian Su
Keyword(s):  
Dynamic Response ◽  
Physical Model ◽  
High Speed ◽  
Lagrange Equation ◽  
Rotor System ◽  
Operating Speed ◽  
Base Excitation ◽  
Rotating Machine ◽  
Vertical Rotor ◽  
Rotary Speed

The physical model of a high-speed vertical rotating machine was taken as the example. The motion differential equations of the rotor system were established by the Lagrange equation and numerically solved by the Wilson-θ method. The whirling characteristics of the rotor excited by the base’s harmonic motions have been analyzed. The whirling directions are different between the rotor’s upper and lower ends. And the whirling characteristics of the rotor vary with the frequency of the base’s motion. Besides, there exists such a region of the rotor’s rotary speed, in which the whirling characteristics and amplitudes of the rotor system are relatively steady, so the aseismic tests at a certain lower speed can be done to examine the aseismic capability of the rotor system at operating speed.

The Simulation of Turbomachinery Blade Rows in Asymmetric Flow Using Actuator Disks

1997 ◽  
Vol 119 (4) ◽  
pp. 723-732 ◽  
Author(s):  
W. G. Joo ◽  
T. P. Hynes
Keyword(s):  
Supersonic Flow ◽  
Flow Field ◽  
Boundary Conditions ◽  
High Speed ◽  
Axial Position ◽  
Numerical Implementation ◽  
Asymmetric Flow ◽  
Actuator Disk ◽  
Blade Row ◽  
Flow Through

This paper describes the development of actuator disk models to simulate the asymmetric flow through high-speed low hub-to-tip ratio blade rows. The actuator disks represent boundaries between regions of the flow in which the flow field is solved by numerical computation. The appropriate boundary conditions and their numerical implementation are described, and particular attention is paid to the problem of simulating the effect of blade row blockage near choking conditions. Guidelines on choice of axial position of the disk are reported. In addition, semi-actuator disk models are briefly described and the limitations in the application of the model to supersonic flow are discussed.

Investigation on the Excitation Characteristics and Dynamic Response of the Multi-Support Flexible Rotor With Misalignment

2017 ◽  
Author(s):  
Sen Xiao ◽  
FaYong Wu ◽  
YanHong Ma ◽  
Jie Hong
Keyword(s):  
Dynamic Response ◽  
High Speed ◽  
Structural Characteristics ◽  
Rotation Frequency ◽  
Frequency Component ◽  
Typical Feature ◽  
Rotor System ◽  
Flexible Rotor ◽  
Rotor Systems ◽  
Response Characteristics

Aiming at the misaligned problems of high-speed flexible multi-supported rotor system, considering the structural characteristics and load characteristics of the rotor, the unbalanced excitation of the rotor with misalignment is presented and quantitatively described. The mechanical model of the high-speed flexible rotor system with multi-support under misaligned excitation is established. Based on the finite element method, the dynamic equation of the rotor system is given and the dynamic response characteristics of rotor systems are studied. The results show that the misalignment for the highspeed multi-support flexible rotor system can not only lead to 2X excitation and support stiffness nonlinearity, but also bring additional unbalanced excitation to the rotor system. The 2X frequency component is one typical feature for the rotor system with bearing misalignment. The vibration response of the rotor showed a trend of “increased slowly first, then reduced quickly as the rotation frequency increased”, and it turns to be more obvious with the increasing of the nonlinear stiffness and unbalance.

Understanding the Influence of Turbine Geometry and Atmospheric Turbulence on Wind Turbine Wakes

2016 ◽  
Author(s):  
Ping Gu ◽  
Jim Y. J. Kuo ◽  
David A. Romero ◽  
Cristina H. Amon
Keyword(s):  
Wind Turbine ◽  
Atmospheric Turbulence ◽  
Aerodynamic Force ◽  
Atmospheric Condition ◽  
Atmospheric Effects ◽  
Wake Region ◽  
Near Wake ◽  
Disk Model ◽  
Actuator Disk ◽  
Far Wake

A wind turbine wake is divided into two regions, near wake and far wake. In the near wake region, the flow is highly turbulent and is strongly influenced by the rotor geometry. In the far wake region, the influence of rotor geometry becomes less important as atmospheric effects become dominant. However, how turbine geometry and atmospheric condition affect the two wake regions is not well studied. In this work, the influence of atmospheric turbulence and the blade aerodynamic forces on wake development is studied using computational fluid dynamics (CFD) models. The CFD simulation results are based on an actuator disk model and an k–ε turbulence model. The effects of blade geometry are captured by prescribing aerodynamics forces exerted by a LM8.2 blade on an actuator disk, and are compared with that of an equivalent uniform normalized force, under two atmospheric turbulence conditions. The finding shows that the length of the near wake region is strongly affected by atmospheric turbulence, with the wake becoming fully developed as far as 2.5 rotor diameters downstream of the rotor under low turbulence conditions. Furthermore, the velocity profile in the far wake region is independent of the blade profile. In other words, in the cases studied, an actuator disk with an equivalent uniform force will produce nearly identical velocity profiles in the far wake region as one with nonuniform aerodynamic force profiles. These findings have implications on existing wake models where the far wake is the region of interest. Specifically, the beginning of the far wake region should be properly defined for each scenario, and that it is not necessary to provide detailed rotor geometry for far wake simulations.

scholarly journals Study on Dynamic Response of Assembly Type Gear-Rotor System

2011 ◽  
Vol 2-3 ◽  
pp. 912-917
Author(s):  
Ji Shuang Dai ◽  
Peng Zhang ◽  
Chao Feng Li ◽  
Bo Wang ◽  
Bang Chun Wen
Keyword(s):  
Dynamic Response ◽  
Working Conditions ◽  
High Speed ◽  
Critical Speed ◽  
Rotor System ◽  
Coupled Systems ◽  
Tilting Pad ◽  
Bearing Stiffness ◽  
Unbalance Force ◽  
Stiffness Characteristics

The dynamic model of a rotor system of assembled compressor is established. Based on the single axis analysis, and considering the tilting-pad bearing stiffness characteristics with speed variations, the paper analyses whole system’s nature characteristic with gearing mesh factors. It mainly expands with the form of amplitude-frequency drawing and spectrum charts, and examines the dynamic response with each key position of coupled systems under the two working conditions. The results show that, because of the existence of gear meshing effect, Low speed axis and high-speed axis in the corresponding speed shaft appeared a few larger vibration amplitudes, at high speed axis add unbalance force, can arouse resonance of this axis in the first two order critical speed, but in the other axis don’t have obvious display.

The Investigation of Turbine and Exhaust Interactions in Asymmetric Flows— Blade-Row Models Applied

2003 ◽  
Vol 125 (1) ◽  
pp. 121-127 ◽  
Author(s):  
J. J. Liu ◽  
T. P. Hynes
Keyword(s):  
Exhaust System ◽  
Numerical Approach ◽  
Flow Properties ◽  
Asymmetric Flow ◽  
Disk Model ◽  
Field Coupling ◽  
Actuator Disk ◽  
Blade Row ◽  
Sample Application ◽  
Asymmetric Flows

This paper describes the blade-row models applied to the asymmetric flow-field coupling between turbine and exhaust system. Numerical actuator disk is applied to represent a turbine blade row around the whole annulus and flow properties across the disk can jump to achieve required flow turning and entropy rise. The derivation of disk boundary conditions and the implementation in CFD solvers are described in detail. Validation of the actuator disk model and sample application of the present numerical approach are presented.

The Effect of Strain Rate on the Material Characteristics of Nickel-Based Superalloy Inconel 718

2007 ◽  
Vol 340-341 ◽  
pp. 283-288 ◽  
Author(s):  
Jung Han Song ◽  
Hoon Huh
Keyword(s):  
Dynamic Response ◽  
High Strain Rate ◽  
Strain Rate ◽  
Turbine Blade ◽  
Inconel 718 ◽  
High Speed ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Experimental Results ◽  
Stress Wave Propagation

The dynamic response of the turbine blade materials is indispensable for analysis of erosions of turbine blades as a result of impulsive loading associated with gas flow. This paper is concerned with the dynamic material properties of the Inconel 718 alloy which is widely used in the high speed turbine blade. The dynamic response at the corresponding level of the strain rate should be acquired with an adequate experimental technique and apparatus due to the inertia effect and the stress wave propagation. In this paper, the dynamic response of the Inconel 718 at the intermediate strain rate ranged from 1/s to 400/s is obtained from the high speed tensile test and that at the high strain rate above 1000/s is obtained from the split Hopkinson pressure bar test. The effects of the strain rate on the dynamic flow stress, the strain rate sensitivity and the failure elongation are evaluated with the experimental results. Experimental results from both the quasi-static and the high strain rate up to 3000/s are interpolated in order to construct the constitutive relation that should be applied to simulate the dynamic behavior of the turbine blade made of the Inconel 718.

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