J. García-Tíscar

Simulations and measurements of automotive turbocharger compressor whoosh noise

Turbocharger noise has become a major concern in downsized automotive engine development. In this paper, the analysis is focused on the whoosh noise produced by the compressor when it is working near surge. A centrifugal compressor has been acoustically characterized on a turbocharger test rig mounted on an anechoic chamber. Three in-duct pressure signals forming a linear array are registered in order to obtain pressure components. In this way, meaningful pressure spectra and sound intensity level (SIL) compressor maps are obtained, showing an increase of SIL in the frequency window corresponding to whoosh noise. Besides, detached eddy simulations (DES) of the centrifugal compressor flow in two operating conditions near surge are performed. Good agreement is found between the experimental measurements and the CFD solutions in terms of predicted pressure spectra. Flow analysis is used to identify patterns responsible for the different features of the pressure spectra. At the simulated conditions, rotating instabilities in the compressor diffuser and inducer cause pressure oscillations in the frequency range of whoosh noise.

Acoustic characterization of automotive turbocompressors

The performance of different experimental techniques proposed in the literature for acoustic characterization was assessed through the study of the noise generated by the compressor of an automotive turbocharger under different working conditions in an engine test cell. The most critical restrictions of in-duct intensimetry methods regarding frequency limitations are presented and experimentally demonstrated. The results provided by those methods were correlated against a reference intensity probe. A beamforming method based on three-sensor-phased arrays appears to be the most reliable approach in the plane wave range, presenting higher accuracy than the more common two-microphone method and simple pressure level measurements. Also, preliminary results from a novel radiated noise quantification technique based on acoustic particle velocity are presented and discussed. The results indicate that further research on this topic is required.

Experimental analysis of cyclical dispersion in CI vs. SI engines and its significance for combustion noise numerical modelling

European Regional Development Fund (Dotacion de infraestructuras cientifico tecnicas para el Centro Integral de Mejora Energetica y Medioambiental de Sistemas de Transporte, CiMeT) (FEDER-ICTS-2012-06). Programa de Apoyo para la Investigacion y Desarrollo (PAID) Universitat Politecnica de Valencia (FPI-S2-2016-1353).

Impact of simple surge-enhancing inlet geometries on the acoustic behavior of a turbocompressor

This article reports the results of an experimental campaign where four different inlet geometries for the compressor of an automotive turbocharger were acoustically characterized. These four geometries (a straight pipe for reference, a tapered duct, a 90° elbow and a reservoir) were selected for their potential for deep surge margin enhancement, while being simple enough to be commonly found in production vehicles. A detailed measurement of this surge margin enhancement was performed, together with acoustic measurements of both radiated and orifice noise at design conditions of best isentropic efficiency and also close to the deep surge limit. Results demonstrated that while all the proposed geometries indeed enlarged the usable air mass flow range, changes in the acoustic behavior of the system could be positive, neutral or even negative. It is therefore important to carefully consider accurate noise measurements before implementing these geometric solutions in production vehicles and to further pursue research on the link between the characteristic flow pattern produced by each inlet geometry and the noise emission of the turbocompressor.