II. Performance Curves of Pumps and Centrifugal Fans

II. Performance Curves of Pumps and Centrifugal FansExperimental and theoretical analysis demonstrates that inherent relationships exist between the performance parameters of any impeller pump or centrifugal fan. The intricate relationship between a pump or fan's performance characteristics is represented graphically as a curve known as its performance curve. The performance curve of a pump or centrifugal fan provides a comprehensive, integrated, and intuitive reflection of its operational performance. Due to the complexity of fluid flow within pumps or fans, precise performance curves can currently only be obtained through experimental measurement. The performance curve of a pump or centrifugal fan typically uses flow rate as the horizontal coordinate. Key components of a pump's performance curve include: - Head versus flow rate (H-Q) - Shaft power versus flow rate (suction) - Efficiency versus flow rate (φ-Q) - Permissible vacuum suction height or net positive suction head (NPSH) (h). Fan performance curves primarily include total pressure-flow rate, open pressure-flow rate, axial power-flow rate, total pressure efficiency-flow rate, and pulsation efficiency. Centrifugal fan performance curves are often expressed using dimensionless parameters: total pressure coefficient-flow coefficient, power coefficient-flow coefficient, efficiency-flow rate, etc. The above illustrates the performance curves for pumps and centrifugal fans. Plotting the head (total pressure)-flow curves at different rotational speeds on a single graph yields the general performance curve for pumps and centrifugal fans. The shape characteristics of impeller pump and centrifugal fan performance curves primarily depend on the impeller structure, which is closely related to their specific speed.