Study on the suitable high-frequency PIV sample for centrifugal pump visualization based on impeller speed

The flow characteristics in centrifugal pump are complicated due to its complex geometry structure. Based on micro-internal circulation experimental bench and high-frequency PIV system, the velocity field at different experimental conditions is measured and the velocity values under different PIV sample frequencies are compared and analyzed. The results indicate that within the relative velocity error limit of 5%, the minimum sample frequency of the high-frequency PIV system should be greater than 2000 Hz for the impeller with speed of 600 r/min at design condition. While the speeds of the impeller are 400 r/min and 500 r/min, the minimum sample frequency must be higher than 1428 Hz and 1667 Hz, respectively. The minimum sample frequency only needs to reach about 1111 Hz when the impeller speed is reduced to 300 r/min. However, it requires a higher minimum sample frequency for the impeller at part-load conditions. The minimum sample frequency should be higher than 3333 Hz, 2500 Hz and 2000 Hz for the impeller speed with 600 r/min, 500 r/min and 400 r/min, respectively. When the impeller speed is less than 600 r/min, the sample frequency of high-frequency PIV system should not exceed 5000 Hz. The results provide important reference indicators for the construction of high-frequency PIV system used in centrifugal pumps. Graphical abstract