Evaluation of the influence of volute roughness on turbocharger compressor performance from a manufacturing perspective

This paper presents a comprehensive surface roughness evaluation of a mass-produced turbocharger centrifugal compressor for automotive application. The aim is to study the impact of surface roughness on compressor performance and manufacturability of the volute. Surface roughness data for different components has been obtained from drawing specifications and sample measurements. Detailed compressor performance evaluation has been made in three parts using CFD. In the first part, the overall compressor performance variation has been simulated from stall to choke over a speed line; initially with all smooth surfaces and later, with rough surfaces. The second part decomposes the performance variation into its sources by simulating each compressor component individually with its specific roughness. Moreover, a performance sensitivity analysis has been conducted to identify the components most responsive to limited surface roughness deviation. In the third part, the volute is subdivided into five sections and a performance sensitivity analysis has been performed by sequentially varying the surface roughness for each section within a particular deviation range. The analysis revealed the sections which essentially require smoothing via sand core coating. Lastly, the roughness specifications have been reviewed especially for the volute, keeping in view the benefits the new specifications may have on overall compressor performance and manufacturing costs.