Investigations of Automotive Turbocharger Acoustics

Centrifugal compressors working in the surge side of the map generate a broadband noise in the range of 1 to 3 kHz, named as whoosh noise. This noise is perceived at strongly downsized engines operating at particular conditions (full load, tip-in and tip-out maneuvers). A 3-dimensional CFD model of a centrifugal compressor is built to analyze fluid phenomena related to whoosh noise. A detached eddy simulation is performed with the compressor operating at the peak pressure point of 160 krpm. A steady flow rig mounted on an anechoic chamber is used to obtain experimental measurements as a means of validation for the numerical model. In-duct pressure signals are obtained in addition to standard averaged global variables. The numerical simulation provides global variables showing excellent agreement with experimental measurements. Pressure spectra comparison is performed to assess noise prediction capability of numerical model. The influence of the type and position of the virtual pressure probes is evaluated. Pressure decomposition is required by the simulations to obtain meaningful spectra. Different techniques for obtaining pressure components are analyzed. At the simulated conditions, a broadband noise in 1-3 kHz frequency band is detected in the experimental measurements. This whoosh noise is also captured by the numerical model.

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“…The most commonly considered measurements are external radiated noise [1,2], orifice noise [5,10], and internal (in-duct) flow noise [1,3,15].…”

Section: Turbocharger Noise Measurementsmentioning

confidence: 99%

“…Some authors [5,10] rely on single sensor measurements for either external and internal measurements, while others prefer sophisticated methods involving more sensors in order to obtain spatially averaged noise on the external case [1,2], or to allow the use of wave decomposition techniques on the internal case [3,15].…”

Section: Turbocharger Noise Measurementsmentioning

confidence: 99%

Methodology for experimental validation of a CFD model for predicting noise generation in centrifugal compressors

Broatch

Galindo

Garcia

et al. 2014

International Journal of Heat and Fluid Flow

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“…The quality of the measurement results was however very poor at higher pressure ratios. An experimental study conducted by Veloso and El nemr (2012) in cooperation with Tiikoja et.al. (2011) uncovered the passive acoustic characteristics of an automotive turbocharger compressor unit discussing the behavior over a frequency range up to 1600 Hz, indicating characteristic acoustic transmission loss curves for different operating conditions under ideal and steady non-pulsating flow operations.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation of transmission loss in an automotive turbocharger compressor under ideal and real engine operating conditions

Nemr

Veloso

Girstmair

et al. 2017

European Conference on Turbomachinery Fluid Dynamics and Hermodynamics

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Acoustic transmission losses are expected to occur over the turbocharger compressor, especially along its rotating wheel section. Experiments on the acoustic characteristics of automotive turbocharger compressors were performed to investigate this acoustic transmission loss behavior. Two different rotor sizes were acoustically investigated considering approximately the same performance characteristics of the compressors. The investigated variants passed through two phases of measurements: The first phase was performed under ideal operating conditions involving a steady non-pulsating flow on an acoustic component test rig for turbochargers. Whereas the second phase was conducted under real engine operating conditions including pulsating flow of a modern 6-cylinder gasoline engine on an engine test rig. Comparisons between the two measurement phases show a considerable agreement between the two test rig setups for different operating conditions.

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“…The most commonly considered measurements are external radiated noise [21,22], orifice noise [25,34], and internal (in-duct) flow noise [21,22,23,50]. Other experimental studies such as the ones carried out by Mongeau et al [28] or Raitor and Neise [30] are based on a detailed instrumentation of the impeller with pressure transducers.…”

Section: Turbocharger Noise Measurementsmentioning

confidence: 99%

“…Some authors [25,34] rely on single sensor measurements for either external and internal measurements, while others prefer sophisticated methods involving more sensors in order to obtain spatially averaged noise on the external case [21,22], or to allow the use of wave decomposition techniques on the internal case [23,50].…”

Section: Turbocharger Noise Measurementsmentioning

confidence: 99%

A numerical approach for predicting flow-induced acoustics at near-stall conditions in an automotive turbocharger compressor

Garcia¹

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Airborne turbocharger noise is becoming a topic of major concern for automotive manufacturers. Particularly, a broadband noise named as whoosh is detected during some engine conditions (full load, tip-in and tip-out maneuvers). This thesis aims to contribute to the understanding of turbocharger compressor flow-induced acoustics by means of 3-dimensional CFD.A methodology to compare CFD and experimental spectra is developed so as to solve the issue of the different location of pressure probes. Pressure decomposition and different types of monitors are required by the model in order to provide meaningful spectra. A tip clearance sensitivity analysis is performed, concluding that tip clearance has an impact on compressor global variables but not on noise generation. CAD tip clearance profile is therefore safely used throughout the thesis. Most important set-up parameters such as grid spacing, solver type or time-step size are evaluated. The model is defined so that noise prediction accuracy is guaranteed in the whole hearing range. In any case, the time-step increment sensitivity analysis reflects that a significant save in computational effort could be made but retaining the right prediction of main spectra features.Finally, three operating conditions are studied at same compressor speed; from best efficiency point to a working point close to surge. All the points present backflows (flow moving from the passage outlet towards the inlet) near the shroud, although their thickness increase when reducing the mass flow. This recirculation zone increase the meridional velocity and improve incidence angle, thus extending the stability margin. Noise emission also is more intense as flow is reduced, particularly at low frequency range. At best efficiency point, a periodic flow separation is observed on the blades suction side. Stalled cells are transported towards the exducer producing a pulsating jet-wake structure that may increase the broadband noise slightly below the main blade passing frequency.In the two points with less mass flow, inducer and diffuser rotating stall can be noticed, causing the so-called whoosh noise. Actually, the point closest to surge presents an increase in the low frequency content found which masks whoosh noise. In this working point, a tornado-like structure is identified in the mixing region between the incoming and recirculating flows, increasing secondary flows and causing large pressure oscillations at the inducer. It is v considered that this phenomenon is responsible for the low frequency noise content rise.Keywords: CFD simulation; Aeroacoustics; Whoosh noise; Rotating stall; URANS; DES vi ResumenLos fabricantes del sector automotriz se están empezando a preocupar por el ruido aéreo generado por el turbogrupo. En particular, un ruido de banda ancha denominado whoosh es detectado en ciertas condiciones (a plena carga y en aceleraciones y desaceleraciones. Esta tesis pretende contribuir al entendimiento de la aeroacústica de los compresores de turbogrupos utilizando CFD tridimens...

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Investigations of Automotive Turbocharger Acoustics

Cited by 19 publications

References 7 publications

Methodology for experimental validation of a CFD model for predicting noise generation in centrifugal compressors

Methodology for experimental validation of a CFD model for predicting noise generation in centrifugal compressors

Experimental investigation of transmission loss in an automotive turbocharger compressor under ideal and real engine operating conditions

A numerical approach for predicting flow-induced acoustics at near-stall conditions in an automotive turbocharger compressor

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