Simulation of Radial Compressor Aeroacoustics Using CFD

Abstract

This paper focuses on the application of CFD to the prediction of radial compressor aeroacoustics. It concentrates mainly on automotive turbocharger operations in the low mass-flow range where blade leading-edge and tip separation reduce the compressor performance and induce transient flow behaviour. Whereas the blade-passing is tonal and at high frequency, usually beyond the human hearing range, transience in the flow are turbulence-dominated, broad-band in nature, and in magnitude a significant source of aeroacoustics which appears well within the range of peak human hearing (1–5kHz). Other noise sources occur due to distortions in the flow upstream of the compressor face, and rotating stall. The simulation methodology enumerated here pays attention to all the above flow-induced aeroacoustics. Due consideration is given to turbulence modelling, to ensure that both the narrow-band and broad-band sources are directly resolved in the CFD. Appropriate discretisation practices are adopted, so as to capture both turbulent-convection and sound-propagation mechanisms. Pressure-wave non-reflective boundary conditions are applied to the computational boundaries to remove any artificial resonances in the domain. STAR-CCM+, the commercial CFD code used here, was previously benchmarked against experimental data for the same compressor under ideal installation conditions, then the compressor performance assessed under real installation conditions [1]. The main foci of the studies reported here are to exploit possible improvements in modelling of the device performance and efficiency curves using more detailed wall modelling, comparing low-y+ versus high-y+ wall resolution, and to explore the viability for transient CFD calculations to capture the noise sources in the compressor at the challenging low mass flow end of the performance characteristic.

Blind test comparison of the performance and wake flow between two in-line wind turbines exposed to different turbulent inflow conditions

“…They observed hysteretic behavior for Re C < 1 × 10 5 , which is assumed to be the cause for Reynolds-dependent behavior of the inner blade elements of the upstream turbine under design conditions. Another experimental set of S826 airfoil data was presented by Ostovan et al (2013) from Middle East Technical University (METU) in Turkey. They investigated lift and drag coefficients from Re C = 7.15 × 10 4 to Re C = 1.45 × 10 5 on a two-dimensional wing with a chord length of c L = 0.20 m. No hysteretic effects for low Reynolds numbers were found in this experiment.…”

“…More information about the use of Star-CMM+ in rotating flows can be found in Mendonça et al (2012), for example.…”

Simulations and measurements of automotive turbocharger compressor whoosh noise

“…The phenomenon may be related to the so-called tip clearance noise described by Raitor and Neise (2008), but Galindo et al (2015) found no influence of tip clearance ratio on whoosh noise. Simulations performed by Mendonça et al (2012) predicted a broadband noise at 70% of impeller rotation frequency, which corresponds to the whoosh noise frequency range. Mendonça et al ascribed the broadband feature to rotating stall, although their analysis was focused on the inducer flow behavior.…”

“…Numerical simulations are configured following the criteria used by Mendonça et al (2012). Detached eddy simulations with underlying k-ω SST turbulence model were performed using the rigid body motion approach.…”

“…Additionally, the effects of various resonators at different locations of the intake line on whoosh noise attenuation were studied. Mendonça, Baris, and Capon (2012) conducted a numerical study regarding flow-induced acoustics of an automotive centrifugal compressor. Sound pressure level (SPL) spectra were obtained for points in both inlet and outlet ducts.…”