Numerical investigation of deep surge in a centrifugal compressor with vaned diffuser and large plenum

Abstract

As the flow rate decreases from stable point to surge point, the complex unsteady flow phenomenon of surge occurs in a centrifugal compressor, which has a significant influence on vast aspects of a compressor. To advance deep understanding of the feature of the deep surge phenomenon, the RANS/URANS numerical simulation is conducted on a centrifugal compressor with a large plenum to analyze the detailed internal flow field in the compressor together with the macroscopic characteristics of the deep surge cycle. The anticlockwise limit cycle obtained from the simulation is firstly analyzed to show the transient characteristics of the stage. Then the variation of blade torque and axial force is presented to show the transient feature in surge cycle together with the proposed prediction of blade torque versus mass flow rate. Meanwhile, there exist different characteristics of the pressure fluctuation along the streamwise direction of the impeller blade, especially the large variation of blade loading near the trailing edge. And the fluctuation of flow field can respectively suppress or promote the hub-corner separation at the process of acceleration or deceleration region, affecting the development of diffuser stall in the surge cycle. The detailed analysis can be helpful to develop the surge model of lumped parameters and determine the effect of surge on impeller blades or downstream components.

Sensitivity Study of Greitzer Model Based on Physical System Parameters of Radial Compressing Units

“…Accurate prediction of the surge onset point can be done with different methods including experiment [20] or computational fluid dynamics simulation. Such simulations for the surge and the rotating stall phenomena were performed by Sundström et al [21], Yang et al [22] or Kulak et al [23]. Even this method also needs additional developments for a better surge line prediction.…”

Spatial-Temporal evolution characteristics of pre-Stage-stall in a centrifugal compressor with a vaneless diffuser and a volute

“…The compressors are required to simultaneously meet the requirement of high efficiency, high-pressure ratio, and broad operating range. [1][2][3] The stable operating range of centrifugal compressors is confined by the unstable flow phenomenon of rotating stall 4 and surge, 5 which also deteriorates the efficiency and induces severe vibrations. 6 The surge, which should be practically avoided, is usually triggered by the stage stall.…”