Prediction of Broadband Noise in an Automotive Centrifugal Compressor with Three-Dimensional Computational Fluid Dynamics Detached Eddy Simulations 2019-01-1487
Centrifugal compressors for automotive turbochargers must operate over wide speed and flow ranges to provide the required air pressure and mass flow rate to the intake manifold of the internal combustion engines. At a fixed rotational speed, the flow-field near the inducer of the impeller becomes increasingly unstable with decreasing flow rate, as the incidence angle grows between the air flow approaching the impeller, relative to the tangent of the main impeller blades at the leading edge. Flow-field measurements conducted earlier have revealed that once the incidence angle exceeds a critical value (nearly independent of rotational speed) of approximately 15°, reversed flow near the periphery (blade tips) penetrates upstream of the impeller, with a high tangential velocity in the direction of impeller rotation. As the incidence angle is increased towards this critical value, whoosh noise elevates in the 4-7 kHz range, where it remains high for a significant portion of the mid-flow operating range, before decreasing at further elevated incidence angles. In order to further understand this phenomenon, a detailed, three-dimensional (3D) computational fluid dynamics (CFD) model of the experimental setup was constructed to study how the impeller flow-field changes with flow rate and contributes to noise generation. Predictions from this 3D CFD model agree reasonably well with experiments, including the steady-state performance and noise as captured from the pressure transducer installed in the compressor inlet duct. The unsteady flow-field of the 3D CFD predictions is then spatially analyzed to identify regions with the highest noise and investigate the contributing flow structures.
Rick Dehner, Ahmet Selamet
Ohio State University
Noise and Vibration Conference & Exhibition