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首页> 外文期刊>Journal of turbomachinery >Characterization and Impact of Secondary Flows in a Discrete Passage Centrifugal Compressor Diffuser
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Characterization and Impact of Secondary Flows in a Discrete Passage Centrifugal Compressor Diffuser

机译：离散通道离心压缩机扩压器中二次流的特性及其影响

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摘要

Truncating the exit of a discrete passage centrifugal compressor diffuser is observed to enhance a research compressor's stall line. By interrogating the experimental data along with a set of well-designed Reynolds-Averaged Navier-Stokes computations, this improvement is traced to the reduced impact of secondary flows on the truncated diffuser's boundary layer growth. The secondary flow system is characterized by counter-rotating streamwise vortex pairs that persist throughout the diffuser passage. The vortices originate from two sources: flow nonuniformity at the impeller exit and separation off the leading edge cusps unique to a discrete passage diffuser. The latter detrimentally impacts the diffuser pressure rise capability by accumulating high loss flow along the diffuser wall near the plane of symmetry between the vortices. This contributes to a large passage separation in the baseline diffuser. Using reduced-order modeling, the impact of the vortices on the boundary layer growth is shown to scale inversely with the diffuser aspect ratio, and thus, the separation extent is reduced for the truncated diffuser. Because the diffuser incidence angle influences the strength and location of the vortices, this mechanism can affect the slope of the compressor's pressure rise characteristic and impact its stall line. Stall onset for the baseline diffuser configuration is initiated when the vortex location and the corresponding passage separation transition from pressure to suction side with increased cusp incidence. Conversely, because the extent of the passage separation in the truncated diffuser is diminished, the switch in separation side does not immediately initiate instability.
机译：观察到截断离散通道离心式压缩机扩散器的出口可增强研究型压缩机的失速线。通过询问实验数据以及一组设计良好的雷诺平均Navier-Stokes计算，这种改进可追溯到二次流对截顶扩散器边界层生长的影响减小。二次流系统的特征是在整个扩散器通道中持续存在反向旋转的涡流对。涡流有两个来源：叶轮出口处的流动不均匀和分离通道扩散器独特的前缘尖端。后者通过在旋涡之间的对称平面附近沿扩散器壁累积高损失流，从而不利地影响扩散器压力上升能力。这有助于基线扩散器中的较大通道分离。使用降阶建模，涡流对边界层生长的影响显示为与扩散器的长宽比成反比，因此，截断的扩散器的分离程度减小了。由于扩压器的入射角会影响涡流的强度和位置，因此该机制会影响压缩机的压力上升特性的斜率并影响其失速线。当涡旋位置和相应的通道间隔从压力侧过渡到吸力侧且尖点发生率增加时，就会开始基线扩散器配置的失速发作。相反，由于截断的扩散器中通道分离的程度减小了，所以分离侧的开关不会立即引发不稳定性。

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