Stability Improvement of a Turbocharger Centrifugal Compressor by a Nonaxisymmetric Vaned Diffuser

Abstract

The nonuniformity of the flow field induced by a nonaxisymmetric volute significantly degrades the stability of a turbocharger centrifugal compressor. In this paper, a nonaxisymmetric vaned diffuser is investigated as a nonaxisymmetric flow control method using both three-dimensional computational fluid dynamics (CFD) and experiment. The numerical study first focuses on the relationship between the flow field and the static pressure distortion, and the steady CFD results indicate that the positive static pressure gradient in the rotating direction facilitates flow separation in the vaned diffuser and induces a nonuniform flow field. A nonaxisymmetric flow control method with variable stagger and solidity of the vaned diffuser is developed to suppress the flow separation, and the guideline of the method suggests narrowing flow passages where the flow separates or closing diffuser vanes upstream of flow separations. Steady CFD also presents the flow field of the investigated turbocharger centrifugal compressor with volute, and flow separation is found in the flow passages near the volute tongue. Under the guidance of the nonaxisymmetric flow control method, several nonaxisymmetric vaned diffusers are designed to make the flow field uniform, which are believed to be beneficial for compressor stability. Finally, an experiment is carried out to validate the positive effects of the nonaxisymmetric vaned diffuser for stability improvement. The test data show that Non-AxisVD (with a nonaxisymmetric vaned diffuser) extends the stable flow range (SFR) of the compressor by 26% compared with the AxisVD (with an axisymmetric vaned diffuser), at the cost of acceptable decreases in the maximum total pressure ratio and peak efficiency.

Effect of Vaned and Vaneless Diffuser on the Performance of Turbo Blowers

“…A signi cant issue arises from the increased distortion in the ow around the pipes, particularly in non-symmetrical areas like bent suction pipes and scrolls. This trend raises the possibility of reduced e ciency and limits the operating range [10].…”

Roles of vanes in diffuser on stability of centrifugal compressor

“…In consideration of the vital role of the diffuser passage near the volute tongue on flow instabilities 24 and the comparability of pressure fluctuations measured by different probes arranged circumferentially, what will be investigated below pays more attention to the probes close to the volute tongue, which mainly include I-2 and II-3.…”

Effect of bend-induced inlet distortion on a centrifugal compressor performance and stall inception

“…Nevertheless, for a turbocharger centrifugal compressor with high pressure ratio, the use of variable diffuser vanes could extend the stable operating range with an acceptable decline of aerodynamic performance, according to the study of Zheng. 17 and Huang. 18…”