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  • 1.
    Rynell, Anders
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    A numerical investigaton of aerodynamic and acoustic installation effects caused by an upstream automotive radiatorManuscript (preprint) (Other academic)
    Abstract [en]

    An automotive radiator, situated closely upstream of an operating fan, modifies the flow field impinging on the fan blades. This in turn is reflected in the noise produced. In addition, the operating condition is changed attributed to the intrinsic pressure loss of the radiator. Further, additional structural elements scatter the sound originating from the impeller due to extraneous or intrinsic sources imposed by the radiator in the system. This paper numerically examines these effects by aerodynamically and acoustically modeling of the radiator as a porous medium. The flow field is resolved utilizing the methodology of improved delayed detached eddy simulation (IDDES) and the sound in the far-field is computed by a finite element sound propagation solver given the velocity components on an interface defined as the sound source plane. The sound pressure level (SPL) is presented for different rotational speeds and microphone positions and is compared to the measured SPL of a similar setup. The acoustic properties of the radiator alone is related to the sound transmission behavior simulated and measured. The results presented are in accordance with the behavior acquired experimentally.

  • 2.
    Rynell, Anders
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    A numerical study of fan noise linked to imposed synthetic turbulence impinging the rotorManuscript (preprint) (Other academic)
    Abstract [en]

    A study has been conducted to numerically examine the noise generation mechanisms associated witha low-speed fan operating in a turbulent-rich inflow. Although, the turbulent content in the upstreamflow is an important aspect of the noise characteristics associated with subsonic fans, it is often omittedin numerical investigation. In this paper the turbulent structures are generated by the synthetic eddymethod (SEM) which ensures that the vortical structures imposed on the inflow boundary are temporallyand spatially correlated. The flow field is resolved using the Improved Delayed Detached Eddy Simulation(IDDES), which enables in addition to the deterministic tonal components associated with the blade passingfrequency (BPF) and its harmonics, the continuous envelope of broadband noise associated with turbulenceto be scrutinized. In the present work, the noise produced from the tip leakage flow is suppressed by aslightly less resolved tip region. Hence the effect on the noise produced associated with both the inflowturbulence and the vortices in the tip region are examined. The sound pressure level (SPL) in the far-fieldis obtained from the Ffowcs–Williams and Hawkings acoustic analogy. Validation with experimental resultsof a similar setup is provided. The results presented accentuates the need for properly constructed inletboundary conditions where turbulent structures, either part of the inflow or developed in the tip region,reinforce the noise produced.

  • 3.
    Rynell, Anders
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    A numerical study of noise characteristics originating from a shrouded subsonic automotive fanManuscript (preprint) (Other academic)
    Abstract [en]

    The characteristics of the noise radiated from a reduced automotive cooling module is numerically studied with focus on the interaction effects linked to the sound generation mechanisms and the acoustic scattering caused by the confined installation. The flow field is simulated by adopting the formulation of IDDES, which is a numerical technique that enables large scale structures to be resolved and the wall-bounded flow to be treated either in DDES or WMLES depending on the turbulent content within the boundary layer. By comparing the simulated fan performance to two sets of experimental data of a similar setup, the aerodynamic results obtained from IDDES are validated and conformed to the volumetric flow rate delivered for the pressure drop measured. The acoustic part of the study comprises evaluation of the sound source associated with the momentum distribution imposed on the surroundings at an interface slightly upstream the fan. At the microphone positions upstream the installation, the SPL falls within the SPL range measured and the acoustic power delivered by the fan conforms to the SWL obtained from the comparison method in the reverberation room. The system response function, estimated by subtracting the SWL for the free-field simulation from the SWL associated with the reduced automotive cooling modulemarks spectral humps at fixed frequencies, irrespectively of sound source. As such, the engineering approach to spectral decomposition method earlier published which, enables isolating the acoustical properties of the installation from the source, is validated and found to hold.

  • 4.
    Rynell, Anders
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design. Scania, Södertälje, Sweden.
    Acoustic characterization of an underhood cooling module for a heavy duty vehicle2014Licentiate thesis, comprehensive summary (Other academic)
  • 5.
    Rynell, Anders
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    An experimental and numerical study of an automotive cooling module2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Heavy vehicles are major emitters of noise. Especially at idle or low vehicle speeds a large portion of the noise emanates from the fan that forces the flow through the cooling module. The aim of this work is to investigate and reveal aerodynamic and acoustic installation effects linked to the cooling package. This introduces a multidisciplinary approach involving examination of the flow field, sound generation and sound propagation. The work includes two main parts: an experimental and a numerical part. The cooling module used throughout this work, named reduced cooling module, primarily includes a radiator, a shroud, a fan and a hydraulic engine to simplify the aeroacoustics analysis.

    The experimental part comprises measurements of the sound emanated from the cooling package. A new approach to the spectral decomposition method is developed yielding the fan sound power or spectrum to be formulated as a product of a source part and a system part scaling with the Strouhal number and the Helmholtz number. Also, a separate determination of the transmission loss of the radiator is performed. The impact of the radiator on the transmitted noise was found to be negligible.

    The numerical part incorporates comparisons from two aeroacoustics studies; a configuration where the fan is forced to operate at a fixed operation point and measured flow and turbulence statistics are available and the reduced cooling module. A hybrid turbulence modeling technique, IDDES, is adopted for the flow simulations. The sound propagation is calculated by the Ffowcs-Williams and Hawkings acoustic analogy when assuming a free-field sound propagation and by a finite element solver in the frequency domain to capture the installation effects. The simulated SPL conforms to the measured SPL and the blade response to the turbulent inflow and to the tip resolution, respectively, produce noise which spectral shape distribution is modified in accordance with earlier experimental findings published. Furthermore, the influence of an upstream radiator in close contact with the fan on the flow and sound fields is investigated. Here, the simulated aeroacoustic characteristics were found to change similarly to the acoustic measurements with and without radiator.

  • 6.
    Rynell, Anders
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Inclusion of Upstream Turbulent Inflow Statistics to Numerically Acquire Proper Fan Noise Characteristics2016Conference paper (Refereed)
    Abstract [en]

    To obtain realistic noise characteristics from CAA studies of subsonic fans, it is important to prescribe properly constructed turbulent inflow statistics. This is frequently omitted; instead it is assumed that the stochastic characteristics of turbulence, absent at the initial stage, progressively develops as the rotor inflicts the flow field over time and hence that the sound generating mechanism governed by surface pressure fluctuations are asymptotically accounted for. That assumption violates the actual interplay taking place between an ingested flow field and the surface pressure fluctuations exerted by the blades producing noise. The aim of the present study is to examine the coupling effect between synthetically ingested turbulence to sound produced from a subsonic ducted fan. The steady state inflow parameters are mapped from a precursor RANS simulation onto the inflow boundaries of a reduced domain to limit the computational cost. The flow field is resolved utilizing IDDES for turbulence handling and the computational domains are configured for both a single blade and a circumferential complete five bladed fan. The results clearly reveal the limitations of restricting the computational analysis to a single blade. Additionally, a separate investigation of the upstream inlet section shows that the deterministic flow structures generated at the inlet plane are selfsustained within the inlet section. The outcome stresses the importance of incorporating correlated inflow statistics for turbomachinery noise studies. Moreover, the acoustic analogy formulated by Ffowcs -Williams and Hawkings is employed to study the low frequency spectral distribution. Previously conducted measurements are used for validation of both the flow field statistics and the far-field sound field.

  • 7.
    Rynell, Anders
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design. Scania, Södertälje, Sweden.
    Chevalier, M.
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    A numerical study of noise characteristics originating from a shrouded subsonic automotive fan2018In: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 140, p. 110-121Article in journal (Refereed)
    Abstract [en]

    The characteristics of the noise radiated from a reduced automotive cooling module are numerically studied focusing on the interaction effects linked to the sound generation mechanisms and the acoustic scattering caused by the confined installation. The flow field is simulated by adopting the formulation of Improved Delayed Detached Eddy Simulation (IDDES), which is a numerical technique that enables large-scale structures to be resolved and the wall-bounded flow to be treated depending on the turbulent content within the boundary layer. By comparing the simulated fan performance to two sets of measurement data of a similar setup, the aerodynamic results obtained from IDDES are validated and conformed to the volumetric flow rate delivered for the pressure drop measured. The acoustic part of the study comprises evaluation of the sound source associated with the momentum distribution imposed on the surroundings at an interface slightly upstream of the fan. At the microphone positions upstream of the installation, the SPL falls within the SPL range measured and the acoustic power delivered by the fan conforms to the SWL obtained from the comparison method in the reverberation room. The system response function, estimated by subtracting the SWL for the free-field simulation from the SWL associated with the reduced automotive cooling module marks spectral humps at fixed frequencies, irrespectively of sound source. As such, the engineering approach to the spectral decomposition method earlier published, which enables the acoustical properties of the installation to be isolated from the source, is validated and found to hold.

  • 8.
    Rynell, Anders
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design. Scania, Sweden.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Chevalier, M.
    Scania AB, Sweden.
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Vibration monitoring.
    Acoustic characteristics of a heavy duty vehicle cooling module2016In: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 111, p. 67-76Article in journal (Refereed)
    Abstract [en]

    Studies dedicated to the determination of acoustic characteristics of an automotive cooling package are presented. A shrouded subsonic axial fan is mounted in a wall separating an anechoic- and a reverberation room. This enables a unique separation of the up- and downstream sound fields. Microphone measurements were acquired of the radiated sound as a function of rotational speed, fan type and components included in the cooling module. The aim of the present work is to investigate the effect of a closely mounted radiator upstream of the impeller on the SPL spectral distribution. Upon examination of the SPL spectral shape, features linked specifically to the source and system are revealed. The properties of a reverberant sound field combined with the method of spectral decomposition permit an estimation of the source spectral distribution and the acoustic transfer response, respectively. Additionally, purely intrinsic acoustic properties of the radiator are scrutinized by standardized ISO methods. A new methodology comprising a dipole sound source is adopted to circumvent limitation of transmission loss measurement in the low frequency range. The sound attenuation caused by the radiator alone was found to be negligible.

  • 9.
    Rynell, Anders
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design. Scania, Södertälje, Sweden.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Chevalier, Mattias
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Acoustic characteristics of a heavy duty vehicle cooling moduleManuscript (preprint) (Other academic)
  • 10.
    Rynell, Anders
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design. Scania, Södertälje, Sweden.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Chevalier, Mattias
    Scania, Sweden.
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Acoustical Broadband signatures from RANS Turbulence Quantities2014In: The 21st International Congress on Sound and Vibration, 2014, p. 1541-1548Conference paper (Refereed)
    Abstract [en]

    The high capacity of today's computers open up the possibility of using numerical simulations to provide a reliable support for optimization of the cooling module placed in heavy vehicles from both an acoustical and aerodynamic perspective. Typically the cooling compartment in heavy trucks consists of a large number of components building a complex, geometrically dense, package. Acoustically, adjacent surfaces are known to modify the sound level and the sound directivity caused mainly by the fan. For this reason, prediction of the sound sources and their radiation, using highly resolved turbulent numerical simulations, is still not feasible. In this paper, we present acoustic predictions that are based on results from Reynolds-Averaged Navier-Stokes (RANS) simulations on a given fan setup with the objective to identify noise characteristics from the turbulent quantities, using analytical expressions derived for isolated airfoils. The analytical formulas give the power spectral density (PSD) in the far-field associated with the noise mechanisms known as incoming turbulence noise and trailing edge noise both caused by the scattering of turbulent structures at the airfoil's leading- and trailing edge, respectively. In the fan setup, the fan was closely mounted to a shroud and placed in a wall between two adjacent rooms. Compared to the intricate underhood engine bay in a truck, the surrounding area affecting the acoustic radiation has been heavily reduced. Emphasis is to seize the apparent broadband trends previously measured in a facility customized for acoustical investigations. The fan studied is running at subsonic speed and consists of 11 blades, having a diameter of 0.75 m. The sound pressure level (SPL) calculated using the analytical expressions was found to show broadband properties previously captured during measurements.

  • 11.
    Rynell, Anders
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design. Scania, Södertälje, Sweden.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Chevalier, Mattias
    Scania, Sweden.
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Aeroacoustic calculation using DES together with FW-H for a ducted subsonic fan2014Report (Other academic)
  • 12.
    Rynell, Anders
    et al.
    KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design. Scania, Södertälje, Sweden .
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Chevalier, Mattias
    Scania CV, Sweden.
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Quiet and efficient cooling for IC-engine powered systems2013In: 42nd International Congress and Exposition on Noise Control Engineering 2013, INTER-NOISE 2013: Noise Control for Quality of Life, OAL-Osterreichischer Arbeitsring fur Larmbekampfung , 2013, p. 5677-5686Conference paper (Refereed)
    Abstract [en]

    The cooling module placed in heavy vehicles is a compact installation, consisting of several components that all affect the cooling air stream which results in complex flows. Even though the fan is considered the main source of sound, adjacent surfaces affect the flow and the scattering of the sound radiated from the fan and make it difficult to predict the acoustic source distribution and sound field inside and outside of the cooling system. This paper focus on the noise emissions caused by the flow associated with the cooling fan and the interaction with an upstream radiator. The long- Term objective of the work is to obtain an efficient and accurate simulation tool for the design of silent and efficient cooling systems, where the present work will be a viable tool in the evaluation process. A modular test rig was built that consisted of a radiator, shroud, fan and hydraulic engine mounted in a wall, which was located between an anechoic room and a reverberation room in order to control the sound level of the incoming flow. Acoustic characteristics e.g. sound pressure- And sound power levels, have been measured in both rooms and will later be used to validate future numerical simulations.

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