旋回失速抑制を目的とした非軸対称ディフューザによる大流量域の不安定揚程特性に関する実験的考察

抄録

Diffuser Rotating Stall (DRS), a fluid instability in diffuser-type centrifugal pumps, often limits the operating range, prompting the industry to seek solutions. However, a DRS suppression method that does not reduce efficiency has not been implemented in practice. The authors have successfully suppressed DRS while maintaining efficiency by applying a non-axisymmetric diffuser that combines long and short vanes. However, an issue arose: unstable head flow characteristics at high flow rates. In this study, two new types of diffusers were introduced: an axisymmetric diffuser with equal numbers of short and long vanes, and an axisymmetric diffuser consisting solely of short vanes. Performance tests were conducted, and DRS occurrence was confirmed by measuring static pressure fluctuations at the inlet of the vaned diffuser. Performance tests showed that increasing the number of short vanes in the non-axisymmetric diffuser shifts the generated flow rate of the unstable head characteristic toward the high flow rate region. The original efficiency was maintained in all short vane configuration models, and the DRS was suppressed in some models. An analysis based on the stagger angle, focusing on vane shape, revealed a different trend from previous reports, indicating that DRS cannot be predicted based on the stagger angle.