Abstract
The corner separation in the high-loaded compressors deteriorates the aerodynamics and reduces the stable operating range. The flow pattern is further complicated with the interaction between the aperiodic corner separation and the periodically wake-shedding vortices. Accurate prediction of the corner separation is a challenge for the Reynolds-Averaged Navier–Stokes (RANS) method, which is based on the linear eddy-viscosity formulation. In the current work, the corner separation is investigated with the Delayed Detached Eddy Simulation (DDES) approach. DDES results agree well with the experiment and are systematically better than the RANS results, especially in the corner region where massive separation occurs. The accurate results from DDES provide a solid foundation for mechanism study. The flow structures and the distribution of Reynolds stress help reveal the process of corner separation and its interaction with the wake vortices. Before massive corner separation occurs, the hairpin-like vortex develops. The appearance of the hairpin-like vortex could be a signal of large-scale corner separation. The strong interaction between corner separation and wake vortices significantly enhances the turbulence intensity. Based on these analyses, entropy analysis is conducted from two aspects to study the losses. One aspect is the time-averaged entropy analysis, and the other is the instantaneous entropy analysis. It is found that the interaction between the passage vortex and wake vortex yields remarkable viscous losses over the 0–12% span when the corner separation has not yet been triggered; however, when the corner separation occurs, an enlarged region covering the 0–30% span is affected, and it is due to the interaction between the corner separation and wake vortices. The detailed coherent structures, local losses information and turbulence characteristics presented can provide guidance for the corner separation control and better design.
Highlights
The corner separation, which widely exists in the junction area of high-loaded compressors [1], is one of the main concerns in the compressor community
A series of experimental and numerical studies has been conducted about the parameters affecting corner separation, including two-dimensional and three-dimensional separations, the influence of surface roughness and the interaction between tip clearance and corner separation [2,3,4]
The static pressure coefficient Cp is defined as Cp =
Summary
The corner separation, which widely exists in the junction area of high-loaded compressors [1], is one of the main concerns in the compressor community. A series of experimental and numerical studies has been conducted about the parameters affecting corner separation, including two-dimensional and three-dimensional separations, the influence of surface roughness and the interaction between tip clearance and corner separation [2,3,4]. Despite these efforts, the mechanisms of corner separation are still not fully understood. A number of experimental and high-fidelity numerical studies have been carried out in this field. Ma et al experimentally studied the corner separation under different incidence angles [5,6] and numerically studied the intermittency
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