The computational fluid dynamics (CFD) method is used to investigate the three-dimensional cavitation flow fields in a mixed-flow pump with high specific speed. In the numerical modeling, the homogeneous mixture model and Navier-Stokes equation with RNG k − ε turbulence model are employed. At the best efficiency condition, the cavitation location on the impeller blades and the distribution situation of vapor volume fraction were analyzed, as well as the performance curve between the pump's NPSHA and efficiency were predicted. The results show that, the cavitation directly affects the pressure distribution on impeller blade surfaces, and also results in change of the pump external characteristic. Under the primary cavitation condition, Water vapors first accumulate on the suction surface of blade's leading edge, which is close to the tip. With the decrease of inlet total pressure, the cavitation region extended towards the trailing edge and water vapor fraction volume become larger gradually. When cavitation is serious, water vapors mainly accumulate on the suction surface of blade's trailing edge. The prediction curve has the same trend as the practical curve, which can reveal the mixed-flow pump cavitation within the static characteristics.

For pumping stations, the effective scheduling of daily pump operations from solutions to the optimum design operation problem is one of the greatest potential areas for energy cost-savings, there are some difficulties in solving this problem with traditional optimization methods due to the multimodality of the solution region. In this case, an ACO model for optimum operation of pumping unit is proposed and the solution method by ants searching is presented by rationally setting the object function and constrained conditions. A weighted directed graph was constructed and feasible solutions may be found by iteratively searching of artificial ants, and then the optimal solution can be obtained by applying the rule of state transition and the pheromone updating. An example calculation was conducted and the minimum cost was found as 4.9979. The result of ant colony algorithm was compared with the result from dynamic programming or evolutionary solving method in commercial software under the same discrete condition. The result of ACO is better and the computing time is shorter which indicates that ACO algorithm can provide a high application value to the field of optimal operation of pumping stations and related fields.

There are recirculation zones and vortexes in the forebay of pumping stations which effect the flow pattern and reduce the efficiency of the pump.The incompressible N-S equations are solved by the finite volume method. The Realizable k-ε turbulence model and the SIMPLE algorithm for pressure-velocity coupling are used. The flow pattern of bottom sills with different positions is calculated. Large recirculation zones and the serious bias flow occur on the both sides in the forebay when there is nothing in the forebay, as well as, flow conditions of sideway pump stations is also bad due to mainstream compression .There is a large recirculation zone and serious bias flow when the bottom sill is too far from the sumps. On the other hand, the flow pattern of sump is badly affected when it is too close to the sumps. The flow pattern is improved when the bottom sill is installed in the right position.There is optimized location where the flow will be pumped uniformly into the sump. The results indicate that the calculation results show a good agreement with the test results. The research results can be applied in the similar forward diffuse forebay of pumping stations.

Three dimensional Laser Doppler Velocimetry (3D-LDV) technique was used to measure the impeller exit flow field of bulb tubular pump, the average velocity distribution of the exit section was obtained, and the energy performance of bulb tubular pump was obtained by model test. The flow field of tubular pump also simulated by CFD based on Navier-Stokes equations and RNG k - model. The calculated performance curve was consistent with the model test results, and the calculated velocities of impeller exit compared with the LDV measurement results, it was shown that the distribution of circumferential velocity and axial velocity were close to each other, but the radial velocity deviation between the LDV results and the CFD ones was obviously, the reasons of deviation were analyzed. The experimental results can provide the references for the impeller and diffuser design of tubular pumps, it also can improve the accuracy of calculation and perfect simulation.

PIV (Particle Image Velocimetry), as an non-intrusive flow measurements technology, is widely used to investigate the flow fields in many areas. 3-D (three Dimensional) PIV has seldom been used to measure flow field in rotational impeller of centrifugal pump due to the difficulty of calibration in samll space. In this article, a specially manufactured water tank was used to perform the calibration for 3-D PIV measurement. The instantaneous absolute velocity in one impeller passage was obtained by merging of three sub zones and the relative velocity was acquired by velocity decomposition. The result shows that, when the pump runs at the condition of design flow rate, the radial component velocity W r appears a concave distribution except the condition of R=45 mm. With the increase of radius, the circumference location of the minimum radial component velocity W r moves from the pressure side to the suction side. At the same time, the tangential component velocity W θ on the suction side decreases gradually with the increase of radius, while the component on the pressure side increases gradually. The secondary flow in different radius section has also been shown. At last, the error of PIV measurements was analyzed, which shows that the test results are accurate and the measured data is reliable.

The unstable operating region affected safety of pump start-up and limited the range of stable operating. When there are three flowrates points matching along with one lift, the hydraulic unstable operating region happened. The range region of unstable operation region is from peak to bottom of performance curve when the axial flow pump was test on the closed test rig. There are two factors, rotating stall and bad inlet condition, which cause the unstable operating region. The unstable operating regions of different pumping system are presented. The unsteady CFD calculations were done to present the internal flow pattern and hydraulic pressure when axial flow pump and mixed flow pump were operated on the unstable operating region. The frequency spectrum is given of one of the force components in radial direction, as measured in the whriling frame of reference. It is important to prevent and avoid unstable operating region along with the construction of South to North water transfer of China and reconstruction of large scale pumping station.