This present work is aimed at providing detailed understanding of the flow mechanisms in a highly loaded centrifugal compressor with different diffusers. Performance comparison between compressor stages with pipe diffuser and wedge diffuser was conducted by a validated flow solver. Stage with pipe diffuser achieved a better performance above 80 % rotating speed but a worse performance at lower rotating speeds near surge. Four operating points including the design point were analyzed in detail. The inherent diffuser leading edge of pipe diffuser could create a better operating condition for the downstream diffusion, which reduced the possibility of flow separation in discrete passages at design rotating speed. At 60 % rotating speed operating point, there was a large negative incidence angle. The sharp leading edge of pipe diffuser could largely accommodate this negative incidence as comparison of the round leading edge of wedge diffuser. As a result, a better performance was achieved in the pipe diffuser. At 60 % rotating speed near surge, performance of the pipe diffuser dropped below wedge diffuser. Total pressure loss of pipe diffuser exceeded that of the wedge diffuser due to the larger friction loss near wall at throat and ineffective static pressure recovery.

中文翻译：

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带楔形扩压器和管道扩压器的高压比离心压缩机的研究

本工作旨在详细了解具有不同扩散器的高负荷离心压缩机中的流动机理。使用经过验证的流量求解器对带有扩压器和楔形扩压器的压缩机级之间的性能进行比较。带扩压器的平台在高于80％的转速时可获得更好的性能，但在接近喘振的较低转速下却表现较差。详细分析了包括设计点在内的四个工作点。管式扩散器的固有扩散器前缘可以为下游扩散创造更好的运行条件，从而降低了在设计转速下离散通道中流动分离的可能性。在转速为60％的工作点时，存在较大的负入射角。与楔形扩压器的圆形前缘相比，扩压器的尖锐的前缘可以在很大程度上抵消这种负入射。结果，在管道扩散器中获得了更好的性能。在接近喘振的60％转速下，管式扩散器的性能下降到楔形扩散器之下。扩压器的总压力损失超过了楔形扩压器的压力损失，这是由于喉部壁附近的较大摩擦损失以及无效的静压恢复所致。