Numerical Investigation of Counter-Rotating Open Rotor Noise Emission in Different Flight Conditions

2012 ◽  
Author(s):  
Eirene Rebecca Busch ◽  
Manuel Keßler ◽  
Ewald Krämer
Keyword(s):  
Numerical Simulations ◽  
Numerical Investigation ◽  
Acoustic Analysis ◽  
Noise Emission ◽  
Rotor Noise ◽  
Total Noise ◽  
Open Rotor ◽  
Blade Tip

Noise emission of a 9×7 and 8×8 open rotor configuration in cruise and in take-off conditions is examined by 3D unsteady numerical simulations utilising the chimera method to represent rotor movement. The acoustic analysis has been carried out with a Ffowcs Williams-Hawkings code over one rotor revolution with a resolution of 360 time steps. To ensure covering of all sources while keeping numerical losses low different hull surfaces have been examined. The comparison of two configurations at different flight conditions shows two main noise generating effects: the single rotor emission and emission caused by interaction of the rotors. The single rotor emission can mostly be seen in the rotor plane whereas the interaction can be examined at an angle of 20 to 45 and 135 to 155 degrees to the rotating axis with approximately the same share of total noise in take-off conditions. In cruise conditions the single rotor emission prevails over the interaction. This can be explained by the transonic blade tip speeds during cruise. Due to the reduced tip speeds in take-off interaction noise contributes to the total noise with a higher share than in cruise conditions. The 8×8-configuration shows higher noise emissions by interaction since the rotor-rotor interactions occur simultaneously.

URANS Simulations and Experimental Investigations on Unsteady Aerodynamic Effects in the Blade Tip Region of a Shrouded Fan Configuration

2017 ◽  
Author(s):  
Gi-Don Na ◽  
Frank Kameier ◽  
Nils Springer ◽  
Michael Mauß ◽  
C. O. Paschereit
Keyword(s):  
Applied Sciences ◽  
Numerical Simulations ◽  
Aerodynamic Performance ◽  
Design Parameters ◽  
Experimental Investigations ◽  
Acoustic Measurements ◽  
Noise Emission ◽  
Industrial Partner ◽  
University Of Applied Sciences ◽  
Blade Tip

The acoustical characteristics of cooling fans are an essential criterion of product quality in the automotive industry. Fan modules have to suffice growing customer expectations which are reflected in the comfort requirements set by car manufacturers around the world. In order to locate dominant acoustic sources and to reduce the noise emission generated by a shrouded fan configuration, numerical simulations and experimental investigations are performed. The working approach considers variously modified fan geometries and their evaluation regarding arising vortex flow phenomena and their effect on a decreased sound pressure level (SPL) in consideration of an improvement or the constancy of aerodynamic fan performance. Particular emphasis lies on the analysis of secondary flows in the blade tip region by post-processing CFD-results. Due to the large number of geometrical modifications investigated and the importance of highly resolved eddy structures, a hybrid approach is chosen by applying the SAS-SST turbulence model in URANS simulations. The SAS (Scale Adaptive Simulation) delivers LES (Large Eddy Simulation) content in unsteady regions of a RANS-simulation and exhibits not nearly the high computational effort needed to perform a full scale LES. An assessment of the actual propagation of noise emission into the far-field is made by performing experimental investigations on the most promising modifications. The acoustic measurements are carried out in a fan test stand in the anechoic chamber of Duesseldorf University of Applied Sciences. The aerodynamic performance is measured in a fan test rig with an inlet chamber setup in accordance to ISO 5801. The measured acoustical and aerodynamic performances are validated by the industrial partner. The results of the acoustic measurements are in turn utilized to determine indicators of noise radiation in the numerical simulation. Within this work an innovative geometry modification is presented which can be implemented into shrouded fan configurations with backward-skewed blades. The new design exhibits a reduced SPL (A-weighted) of approx. 4 dB over the entire operating range while showing no significant deterioration on the aerodynamic performance. While the design was registered for patent approval cooperatively by the industrial partner and Duesseldorf University of Applied Sciences, further investigations regarding variations of design parameters are performed and presented in this paper. All numerical simulations are performed with ANSYS CFX, a commercial solver widely spread in the industry. Methods similar to those shown in this work can be implemented in the design phase of axial fans in order to develop acoustically optimized fan geometries.

A Contra-Rotating Open Rotor Noise Reduction Methodology by Using Anhedral Blade Tip

2021 ◽  
pp. 1-26
Author(s):  
Tianxiao Yang ◽  
Wenjun Yu ◽  
Dong Liang ◽  
Xiang He ◽  
Zhenguo Zhao
Keyword(s):  
Noise Reduction ◽  
Polar Angle ◽  
Aerodynamic Performance ◽  
Tip Vortex ◽  
Rotor Noise ◽  
Lean Angle ◽  
Open Rotor ◽  
Blade Tip

Abstract In this paper, a novel Contra-Rotating Open Rotor (CROR) noise reduction methodology based upon the anhedral blade tip applied to the front blade is developed. Results indicate that anhedral blade tip can provide noise reduction over 60 deg. polar angle range in both upstream and downstream areas at takeoff condition. The noise reduction becomes more significant as the lean angle of anhedral blade tip increases, and the maximum noise reduction is over 4 dB. Further analysis shows that anhedral blade tip decreases the strength and size of blade tip vortex shed from the front blade, and reduces its interaction with the rear rotor, which decreases the fluctuation of loading acting on the rear rotor and its loading noise. Furthermore, the anhedral blade tip does not have strong effect on the aerodynamic performance of CROR at cruise.

Numerical Simulations of Unsteady Aerodynamic Effects in the Blade Tip Region of Cooling Fans

2016 ◽  
Author(s):  
Gi-Don Na ◽  
Frank Kameier ◽  
Nils Springer ◽  
Michael Mauß
Keyword(s):  
Applied Sciences ◽  
Numerical Simulations ◽  
Aerodynamic Performance ◽  
Secondary Flows ◽  
Acoustic Measurements ◽  
Noise Emission ◽  
Industrial Partner ◽  
University Of Applied Sciences ◽  
Blade Tip ◽  
The University

The acoustical characteristics of fans are an essential criterion of product quality and are continually growing in importance as for example cooling fan modules in the automotive industry have to suffice high comfort requirements. In order to locate dominant acoustic sources and to reduce the noise emission generated by a shrouded fan configuration, numerical simulations are performed. The working approach considers variously modified fan geometries and their evaluation regarding arising vortex flow phenomena and their effect on a decreased sound pressure level (SPL) in consideration of an improvement or the constancy of aerodynamic fan performance. Particular emphasis lies on the analysis of secondary flows in the blade tip region by postprocessing CFD-results. Due to the large number of geometrical modifications investigated and the importance of highly resolved eddy structures, a hybrid approach is chosen by applying the SAS-SST turbulence model in URANS simulations. The SAS (Scale Adaptive Simulation) delivers LES (Large Eddy Simulation) content in unsteady regions of a RANS-simulation and exhibits not nearly the high computational effort needed to perform a full scale LES. An assessment of the actual propagation of noise emission into the far-field is made by performing experimental investigations on the most promising modifications. The acoustic measurements are carried out in a fan test stand in the anechoic chamber of the University of Applied Sciences Duesseldorf. The aerodynamic performance is measured in a fan test rig with an inlet chamber setup in accordance with ISO 5801. The measured acoustical and aerodynamic performance is validated by the industrial partner. The results of the acoustic measurements are in turn utilized to determine indicators of noise radiation in the numerical simulation. Within this work an approach is presented where the analyses of secondary flows in the blade tip region provide the basis for an innovative noise reduction design in a shrouded fan configuration. The new design exhibits a reduced SPL (A-weighted) of approx. 4 dB over the entire operating range while showing no significant deterioration on the aerodynamic performance. The design was registered for patent approval cooperatively by the industrial partner and the University of Applied Sciences Duesseldorf, while minor design parameters are still subject to further improvements. All numerical simulations are performed with Ansys CFX, a commercial solver widely spread in the industry. Methods similar to those shown in this work can be implemented in the design phase of axial fans in order to develop acoustically optimized fan geometries.

A parametric study of airframe effects on the noise emission from installed contra-rotating open rotors

2018 ◽  
Vol 17 (6-8) ◽  
pp. 624-654 ◽  
Author(s):  
J Kennedy ◽  
P Eret ◽  
GJ Bennett
Keyword(s):  
Experimental Investigation ◽  
Wind Tunnel ◽  
Parametric Study ◽  
Emission Angle ◽  
Flow Speed ◽  
Scale Model ◽  
Far Field ◽  
Noise Emission ◽  
Rotor Noise ◽  
Open Rotor

This work reports on the results of the Clean Sky WENEMOR project which has conducted an extensive experimental investigation of installed contra-rotating open rotors on a scale model of an advanced regional aircraft configuration. The tests were conducted in the Pininfarina Wind Tunnel, Italy and the data used for this analysis were taken from a linear far-field array of microphones. The contra-rotating open rotors were operated in pusher and tractor modes with approach and takeoff settings for revolutions per minute and thrust. Realistic modern blade profiles were supplied and utilized through the Clean Sky Green Regional Aircraft program. A range of airframe geometries was tested which included interchangeable tails, engine pylon elongation, engine pylon rotation, and variable wing to engine distance. Changes in the contra-rotating open rotor noise emission to the far field as a function of flow speed, angle of attack, and airframe geometry were clearly identified. The influence of airframe geometry on contra-rotating open rotor tonal content, directivity, and broadband levels is reported for emission angles from [Formula: see text] to [Formula: see text]. Both significant noise increases and decreases with respect to the baseline airframe configurations were detected in both the tonal and broadband levels as a function of emission angle (ranging from 10 to 25 dB at the blade passing frequency tones). While the changes to the tonal level were generally greater than those of the broadband level, the broadband levels are shown to be significant when considering the influence of airframe geometries on contra-rotating open rotor noise emission.

Advanced open rotor noise prediction

2014 ◽  
Vol 118 (1208) ◽  
pp. 1125-1135 ◽  
Author(s):  
M. J. Kingan
Keyword(s):  
High Speed ◽  
Broadband Noise ◽  
Current Status ◽  
Prediction Methods ◽  
Noise Prediction ◽  
Acoustic Data ◽  
Rotor Noise ◽  
Future Challenges ◽  
Open Rotor ◽  
Development And Validation

Abstract The purpose of this paper is to describe the current status of open rotor noise prediction methods and to highlight future challenges in this area. A number of analytic and numerical methods are described which can be used for predicting ‘isolated’ and ‘installed’ open rotor tonal noise. Broadband noise prediction methods are also described and it is noted that further development and validation of the current models is required. The paper concludes with a discussion of the analytical methods which are used to assess the acoustic data collected during the high-speed wind-tunnel testing of a model scale advanced open rotor rig.

scholarly journals Limitations of Phased Array Beamforming in Open Rotor Noise Source Imaging

AIAA Journal ◽  
2014 ◽  
Vol 52 (8) ◽  
pp. 1810-1817 ◽  
Author(s):  
Csaba Horváth ◽  
Edmane Envia ◽  
Gary G. Podboy
Keyword(s):  
Phased Array ◽  
Noise Source ◽  
Source Imaging ◽  
Rotor Noise ◽  
Open Rotor ◽  
Array Beamforming

Numerical investigation of blade-tip-vortex dynamics

2018 ◽  
Vol 9 (3) ◽  
pp. 373-386 ◽  
Author(s):  
Kurt Kaufmann ◽  
C. Christian Wolf ◽  
Christoph B. Merz ◽  
Anthony D. Gardner
Keyword(s):  
Numerical Investigation ◽  
Vortex Dynamics ◽  
Tip Vortex ◽  
Blade Tip

Numerical Investigation of Residual Formability and Deformation Localization During Continuous-Bending-Under-Tension

2012 ◽  
Author(s):  
Chetan Nikhare ◽  
Brad L. Kinsey ◽  
Yannis Korkolis
Keyword(s):  
Numerical Simulations ◽  
Numerical Investigation ◽  
Sheet Metal ◽  
Past Research ◽  
Gauge Length ◽  
Tension Test ◽  
Deformation Localization ◽  
Percent Elongation ◽  
Continuous Bending ◽  
Bending Under Tension

A ubiquitous experiment to characterize the formability of sheet metal is the standard uniaxial tension test. Past research [1–3] has shown that if the material is repeatedly bent and unbent during this test (termed Continuous-Bending-under-Tension, or CBT), the percent elongation at failure increases significantly (e.g., from 22% to 290% for an AISI 1006 steel [1]). However, past experiments have been conducted with a fixed stroke of the CBT device, which limits the formability improvements. This phenomenon has also been empirically observed in industry; the failure strains of a sheet which is passed through a drawbead (i.e., that has been bent and unbent three times before entering the die) are higher than those of the original sheet. Thus, the residual formability of the material after a specified number of CBT passes is of interest, to determine if multiple drawbeads would be beneficial in the process. Also of interest is the localization of the deformation during the process as this will provide a better physical understanding of the improved formability observed. In this paper, numerical simulations are presented to assess these effects. Results show that the formability during CBT is dictated by the uniaxial response of the material until the standard elongation at failure is exceeded. This limit can be exceeded by the CBT process. However, failure then occurs as soon as the CBT process is terminated. Also, the deformation is more uniformly distributed over the entire gauge length during the CBT process which leads to the increased elongations observed.

Effect of Burner and Resonator Impedances on the Acoustic Behavior of Annular Combustion Chambers

2006 ◽  
Author(s):  
Annalisa Forte ◽  
Sergio Camporeale ◽  
Bernardo Fortunato ◽  
Francesca Di Bisceglie ◽  
Marco Mastrovito
Keyword(s):  
Numerical Simulations ◽  
Combustion Chamber ◽  
Structural Damage ◽  
Acoustic Pressure ◽  
Acoustic Analysis ◽  
Complex Geometry ◽  
Connected Components ◽  
Acoustic Behavior ◽  
Combustion Chambers ◽  
Helmholtz Resonators

Premixed combustion is the commonly adopted technique to reduce NOx emissions from gas turbine combustion chambers, but it has been proved to be susceptible to thermo-acoustic instabilities, known as humming. These self-excited oscillations can reduce the efficiency of the turbine and generate structural damage to the combustion chamber. One of the proposed suppression methods lies in the application of Helmholtz resonators to the combustion chambers. This passive technique is advantageous in carrying out appreciable oscillation damping with modest costs and long life, but it is effective only in a restricted range of frequency, close to resonator eigenfrequency. Therefore, in order to design effective resonators, it is necessary to know the eigenfrequencies of the annular combustion chamber, because combustion instabilities arise in correspondence of these frequencies. Acoustic analysis of combustion chamber and its connected components may be carried out by means of Finite Element Method, but it requires a considerable computational effort due to the complex geometry of the complete system, which needs to be meshed by a refined grid. A combined numerical and experimental technique allows the authors to increase computational efficiency by adopting coarser and more regular meshes. First acoustic behavior of annular combustion chamber has been studied by means of numerical simulations and, therefore, the influence of the burners has been taken into account by substituting burner geometries by experimentally measured acoustic impedances. Then some Helmholtz resonators, tuned to one eigenfrequency of the combustion chamber, have been designed and manufactured. Their acoustic impedances have been experimentally measured and applied as boundary conditions into FE simulations of the annular chamber. In this way the acoustic pressure field inside the damper-equipped combustion chamber has been analyzed. Numerical simulations of the annular chamber, with burner and damper impedances applied, show that Helmholtz resonators are effective in oscillation suppression in correspondence of their resonance frequency, but may produce the splitting of the acoustic pressure peak of the chamber into two new peaks, whose frequencies lie on either side of the original common eigenfrequency. The amplitudes of these two new pressure peaks appear lower than the amplitude of the baseline one. The proposed technique can be used as an effective design tool: acoustic analysis of annular combustion chamber, with burner impedance applied, produces accurate indications about its acoustic behavior and allows the design of new passive suppression systems and the evaluation of their performances.

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