Effect of Blade Coating on a Centrifugal Pump Operation under Sediment-Laden Water Flow

Applying a high strength coating on a blade’s surface could significantly prolong the service life of a centrifugal pump under sediment-laden water flow because of its protection. To explore the effect of blade coating, the characteristics of energy, vibration and pressure fluctuation of a centrifugal pump (the specific speed (ns) is 81.46) with different polyurethane coating thickness coefficients were experimentally studied under sediment-laden water flow. Keeping the blade outlet angle, blade inlet angle and blade shape unchanged, the head H and efficiency η under both sediment-laden flow and clear water flow decrease significantly as the coating thickness coefficient increases. The axis rotating frequency and blade passing frequency are the main excitation frequencies of the pump vibration velocity amplitude and outlet pressure fluctuation. The vibration velocity amplitude and outlet pressure fluctuation at the frequency of 1 BPF are the largest. At the frequency of 1 axis rotating frequency, they are the second in all cases. The peak values of both vibration velocity amplitude and outlet pressure fluctuation are proportional to the coating thickness coefficient. An analysis was performed for several increasing coating thicknesses, corresponding to coating coefficients from K0 to K3. When the coating thickness coefficients are K0, K1, and K2, the peak value of vibration velocity amplitude under sediment-laden flow is larger than that under clear water flow, but the very small difference between them undercoating thickness coefficient K3. The peak values of pressure fluctuations under different flow rates decrease first and then increase with the increasing coating thickness coefficient, and lowest points are all located at the coating thickness coefficient K1.