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The acoustic and performance characteristics of an automotive centrifugal compressor are studied on a steady-flow turbocharger test bench, with the goal of advancing the current understanding of compression system instabilities at the low-flow range. Two different ducting configurations were utilized downstream of the compressor, one with a well-defined plenum (large volume) and the other with minimized (small) volume of compressed air. The present study measured time-resolved oscillations of in-duct and external pressure, along with rotational speed. An orifice flow meter was incorporated to obtain time-averaged mass flow rate. In addition, fast-response thermocouples captured temperature fluctuations in the compressor inlet and exit ducts along with a location near the inducer tips.

The effect of aerodynamically induced pre-swirl on the acoustic and performance characteristics of an automotive centrifugal compressor is studied experimentally on a steady-flow turbocharger facility. Accompanying flow separation, broadband noise is generated as the flow rate of the compressor is reduced and the incidence angle of the flow relative to the leading edge of the inducer blades increases. By incorporating an air jet upstream of the inducer, a tangential (swirl) component of velocity is added to the incoming flow, which improves the incidence angle particularly at low to mid-flow rates. Experimental data for a configuration with a swirl jet is then compared to a baseline with no swirl. The induced jet is shown to improve the surge line over the baseline configuration at all rotational speeds examined, while restricting the maximum flow rate. At high flow rates, the swirl jet increases the compressor inlet noise levels over a wide frequency range.

The advent of Eco-Boost technology in gasoline engines creates new challenges that need to be addressed with innovative designs. One of them is flow induced noise caused by flow, entering the turbocharger, at off design operation. At certain vehicle operation conditions, the mass flow rate and pressure ratio are such that compressor wheel generates a broad band frequency noise caused by flow separation from blade surfaces, which is called ‘whoosh’ noise. Flow bench and engine testing can be used to detect flow induced noise, but understanding the fundamental mechanisms of such noise generation is necessary for developing an effective design. This paper describes Computational Aero-Acoustic (CAA) analyses performed to study the effects of inlet condition on the whoosh noise. A 3D Computational Fluid Dynamics (CFD) simulation performed including the entire compressor wheel and volute. The wheel consisted of six main and six splitter blades.

Flow bench and engine testing can be used to detect flow induced noise, but understanding the fundamental mechanisms of such noise generation is necessary for developing an effective design. This paper describes Computational Aero-Acoustic (CAA) analyses performed to obtain the broad-band and BPF noise sources A computational aero-acoustics simulation on the aerodynamic noise generation of an automotive radiator fan assembly is carried out. Three-dimensional Computational Fluid Dynamics (CFD) simulation of the unsteady flow field was performed including the entire impeller and shroud to obtain the source of an audible broad-band flow noise between 2 to 4 kHz. Static pressure probes placed around the outer-periphery and at the center of the impeller inlet side and, at the shroud cavities to capture the noise sources. The static pressure at all probe locations were FFT (Fast Fourier Transform) processed and sound pressure level (SPL) was calculated.

The stable operation of turbocharger compressor at low flow rates is important to provide low end engine torque for turbocharged automotive engines. Therefore, it is important to be able to predict the lowest flow rates at different turbocharger speeds at which the surge phenomenon occurs. For this purpose, three-dimensional Computational Fluid Dynamics (CFD) simulations were performed on the turbocharger compressor including the entire compressor wheel and volute. The wheel consisted of six main and six splitter blades. Historically, flow bench and engine testing has been used to detect surge phenomenon. However a complete 3D CFD analysis can be performed upfront in the design to calculate low end compressor surge performance. The analyses will help understand the fundamental mechanisms of stalled flow, the surge phenomenon, and impact of compressor inlet conditions on surge.