NUMERICAL INVESTIGATION OF ROTOR WAKE-STATOR INTERACTION. PDF Download
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Languages : en
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Iv In this thesis, numerical solutions of a 2D stator compressor cascade at a given inlet Mach number (0.7) and four values of incidence (49°, 51°, 53° and 55°) are obtained. Reynolds averaged, thin layer, compressible Navier Stokes equations are solved. Different grid types have been generated. Finite differencing approach and LU - ADI splitting technique are used. Three block parallel Euler and Navier Stokes solutions are compared with the experimental results. Baldwin-Lomax turbulence model is used in the turbulent predictions and boundary layer comparisons and numerical results are in good agreement with the experiment. On the last part of the study, a rotor wake in the inlet flow has been introduced in the steady and unsteady analyses. The influence of this wake and the wake location in the inlet flow, to the total force and pressure is presented. The results have been showed that there is a relationship between the wake position and the incidence value of the case.
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Languages : en
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Book Description
Iv In this thesis, numerical solutions of a 2D stator compressor cascade at a given inlet Mach number (0.7) and four values of incidence (49°, 51°, 53° and 55°) are obtained. Reynolds averaged, thin layer, compressible Navier Stokes equations are solved. Different grid types have been generated. Finite differencing approach and LU - ADI splitting technique are used. Three block parallel Euler and Navier Stokes solutions are compared with the experimental results. Baldwin-Lomax turbulence model is used in the turbulent predictions and boundary layer comparisons and numerical results are in good agreement with the experiment. On the last part of the study, a rotor wake in the inlet flow has been introduced in the steady and unsteady analyses. The influence of this wake and the wake location in the inlet flow, to the total force and pressure is presented. The results have been showed that there is a relationship between the wake position and the incidence value of the case.
Author: Karl Engel
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Languages : en
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Author: Giovanna Cavazzini
Publisher: LAP Lambert Academic Publishing
ISBN: 9783659321511
Category :
Languages : en
Pages : 692
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The interaction between rotating and stationary parts affects the flow field inside both components, modifying the machine performance in terms of operating stability, structural vibrations, noise and pressure pulsations. The aim of this book is to improve the understanding of the rotor-stator interaction phenomena with an extensive in-depth investigation of their characteristics, origin, development and effects on the machine performance. An unusual acoustical approach, aimed at identifying a possible connection between noise emissions and inner fluid-dynamics, was proposed and combined with a PIV experimental analysis in order to study the unsteady flow phenomena developing inside the pump vaned diffuser. These analysis, coupled with a numerical analysis on the same turbomachine, allowed to analyze in-depth the effects of the rotor-stator interaction on the machine flow field and hence on its performance.
Author: Steven Ernest Gorrell
Publisher:
ISBN:
Category :
Languages : en
Pages : 260
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At close spacing the rotor bow shock is actually chopped by the stator trailing edge forming a pressure wave on the upper surface of the stator that propagates upstream until it weakens. In the reference frame relative to this pressure wave, the flow is supersonic and a moving shock wave exists that produces an entropy rise. The lower efficiency, pressure ratio, and mass flow rate measured at close spacing is a result of this extra loss. The magnitude of loss production is affected by the strength of the bow shock at the location it interacts with the trailing edge of the stator. Furthermore, the more blades present in the stator the more loss producing interactions take place. At far spacing the rotor bow shock has degenerated into a bow wave where it interacts with the stator trailing edge and is not chopped, therefore no pressure wave forms on the wake generator upper surface.
Author: Akil A. Rangwalla
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Languages : en
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Author: Daniel Espinal
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Category :
Languages : en
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The objective of this research is to investigate and confirm the periodicity of the Non-Synchronous Vibration (NSV) mechanism of a GE axial compressor with a full-annulus simulation. A second objective is to develop a high fidelity single-passage tool with time-accurate unsteady capabilities able to capture rotor-stator interactions and NSV excitation response. A high fidelity methodology for axial turbomachinery simulation is developed using the low diffusion shock-capturing Riemann solver with high order schemes, the Spalart-Allmaras turbulence closure model, the fully conservative unsteady sliding BC for rotor-stator interaction with extension to full-annulus and single-passage configurations, and the phase lag boundary conditions applied to rotor-stator interface and circumferential BC. A URANS solver is used and captures the NSV flow excitation frequency of 2439 Hz, which agrees reasonably well with the measured NSV frequency of 2600 Hz from strain gage test data. It is observed that the circumferentially traveling vortex formed in the vicinity of the rotor tip propagates at the speed of a non-engine order frequency and causes the NSV. The vortex travels along the suction surface of the blade and crosses the passage outlet near blade trailing edge. Such a vortex motion trajectory repeats in each blade passage and generates two low pressure regions due to the vortex core positions, one at the leading edge and one at the trailing edge, both are oscillating due to the vortex coming and leaving. These two low pressure regions create a pair of coupling forces that generates a torsion moment causing NSV. The full-annulus simulation shows that the circumferentially traveling vortex has fairly periodical behavior and is a full annulus structure. Also, frequencies below the NSV excitation frequency of 2439 Hz with large amplitudes in response to flow-separation related phenomena are present. This behavior is consistent with experimental measurements. For circumferentially averaged parameters like total pressure ratio, NSV is observed to have an effect, particularly at radial locations above 70% span. Therefore, to achieve similar or better total pressure ratio a design with a smaller loading of the upper blade span and a higher loading of the mid blade spans should be considered. A fully-conservative sliding interface boundary condition (BC) is implemented with phase-lag capabilities using the Direct Store method for single-passage simulations. Also Direct Store phase-lag was applied to the circumferential BCs to enforce longer disturbance wavelengths. The unsteady simulation using single-blade-passage with periodic BC for an inlet guide vane (IGV)-rotor configuration captures a 2291 Hz NSV excitation frequency and an IGV-rotor-stator configuration predicts a 2365 Hz NSV excitation frequency with a significantly higher amplitude above 90\% span. This correlates closely to the predicted NSV excitation frequency of 2439 Hz for the full-annulus configuration. The two-blade-row configuration exhibits the same vortex structures captured in the full-annulus study. The three-blade-row configuration only captures a tip vortex shedding at the leading edge, which can be attributed to the reflective nature of the BCs causing IGV-rotor-stator interactions to be augmented, becoming dominant and shifting NSV excitation response to engine order regime. Phase-lag simulations with a Nodal Diameter (ND) of 5 is enforced for the circumferential BCs for the three-blade-row configuration, and the results exactly matched the frequency response and flow structures of the periodic simulation, illustrating the small effect that phase-lag has on strongly periodic flow disturbances. A ND of 7 is enforced at the sliding interface, however the NSV excitation completely disappears and only the wake propagation from IGV-Rotor-Stator interactions are captured. Rotor blade passage exhibits a circumferentially travelling vortex similar to those observed in the full-annulus and two-blade-row simulations. This can occur when the rotating instability responsible for the NSV no longer maintains a pressure variation with a characteristic frequency signature as it rotates relative to the rotor rotation, and now has become the beginning of a spike-type stall cell. In this scenario the travelling vortex has become evidence of part-stall of the upper spans of the rotor blade, but stalling is contained maintaining stable operation. In conclusion, an efficient method of capturing NSV excitation has been proposed in a high-fidelity manner, where only 2% of the computational resources used in a full-annulus simulation are required for an accurate single-blade-passage multi-stage simulation.
Author: Elham Roshani Moghaddam
Publisher:
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Category :
Languages : en
Pages :
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Author: M. Barnett
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Category : Aerofoils
Languages : en
Pages : 42
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Author: David A. Topol
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Category :
Languages : en
Pages :
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Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781726169813
Category :
Languages : en
Pages : 46
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Book Description
This report provides a study of rotor and stator scattering using the SOURCE3D Rotor Wake/Stator Interaction Code. SOURCE3D is a quasi-three-dimensional computer program that uses three-dimensional acoustics and two-dimensional cascade load response theory to calculate rotor and stator modal reflection and transmission (scattering) coefficients. SOURCE3D is at the core of the TFaNS (Theoretical Fan Noise Design/Prediction System), developed for NASA, which provides complete fully coupled (inlet, rotor, stator, exit) noise solutions for turbofan engines. The reason for studying scattering is that we must first understand the behavior of the individual scattering coefficients provided by SOURCE3D, before eventually understanding the more complicated predictions from TFaNS. To study scattering, we have derived a large number of scattering curves for vane and blade rows. The curves are plots of output wave power divided by input wave power (in dB units) versus vane/blade ratio. Some of these plots are shown in this report. All of the plots are provided in a separate volume. To assist in understanding the plots, formulas have been derived for special vane/blade ratios for which wavefronts are either parallel or normal to rotor or stator chords. From the plots, we have found that, for the most part, there was strong transmission and weak reflection over most of the vane/blade ratio range for the stator. For the rotor, there was little transmission loss.Meyer, Harold D.Glenn Research CenterACOUSTIC SCATTERING; AERODYNAMIC NOISE; NOISE PREDICTION; TURBOFANS; TURBOFAN ENGINES; ROTOR BLADES (TURBOMACHINERY); STATOR BLADES; CASCADE FLOW; VANES; SCATTERING COEFFICIENTS; COMPUTER PROGRAMS; THREE DIMENSIONAL MODELS; COMPUTERIZED SIMULATION; TRANSMITTANCE; REFLECTANCE; TRANSMISSION LOSS...
