Automotive Turbochargers Compressor Onset of Surge Prediction using Computational Fluid Dynamics

Abstract

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. To reduce computational time a small volume of compressed air system, essentially a small ‘B’ system as introduced by Greitzer [1], is used in the CFD model. CFD results have been compared with gas stand compressor maps and have good agreements for the compressor map points.This paper presents a CFD analysis near the low flow region at constant turbo speed to predict automotive centrifugal compressor surge phenomenon.