Numerical Research Of Cavitation Flow In Centrifugal Pump

Due to the relationship between monitoring signal and the development of cavitationhas has not yet formed a clear correspondence which on account of cavitationdevelopment situation at the scene of the complex operation almost impossible to directlyobserved, so it couldn’t accurately assess whether cavitation have occurred inside themachine and the development of cavitation according to the collected signals, and alsomakes difficulties to evaluate cavitation development degree inside the hydraulicmachine in the real-time by cavitation monitoring system. Numerical simulation can beused as a complementary method to predict the development of cavitation, and also to bea identification criterion in the acoustic and vibration monitoring system.First of all, the process of numerical simulation of cavitation has been put forwardin view of the difficulties faced by the experimental method to predict cavitation, andthen calculated the cavitation character of the NACA0009hydrofoil based on thestandard-turbulence model and the Rayleigh-Plesset cavitation model. throughcomparing with the test data, which verify the reliability of the numerical simulationmethod to predict cavitation.The cavitation performance and the time-frequency information of virtualmonitoring which both on the wall of volute and outlet of impeller were predictedthrough simulating the unsteady cavitating flow in centrifugal pump. The bubbledistribution rules in the impeller were obtained under different cavitation developingstages, along with the decreasing of pressure in the inlet, bubbles were first appeared onthe suction side of blade first and gradually expanding along the direction of flow, thenfull of the flow channel, which changed the uniform and worse performance. During thedifferent stages of cavitation, the first frequency of pressure pulsation in volute was bladepass frequency and the amplitude near the volute tongue was the greatest Since the effect of rotor-stator interaction was greater than by blade, the high frequency components weremore presented on outlet of impeller than on the wall of volute along with away from thevolute tongue. With the development of cavitation, the peak-peak value change of Ydirection impeller force is more obvious than X direction and Z direction impeller force.The more Y direction impeller force, the more cavitation developing.In addition, the effects mechanism of blade number (Z) on hydraulic performance incentrifugal pump was also investigated. The outlet geometric parameters were optimizedon the basis of changing blade number by using the centrifugal pump efficiency and headas the objective functions. Energy characteristic and the performance of cavitation wereobtained. Also dynamic information of the forces on impeller and the pressure pulsationson the wall of volute were captured.Although the result of numerical calculation were not very accurate to the real modelas made a simplified, but it can be used as a auxiliary criterion in the criterion ofidentification cavitation development state through comparing the numerical simulationwith the real machine test monitoring signal.