To reduce the energy consumption of the double-suction pump, this study optimizes the impeller of the pump based on the Nonlinear Programming Quadratic Lagrangian (NLPQL) algorithm in OptiSLang. Taking the weighted efficiency as the optimization objective, 28 design parameters of the impeller are selected as the input variables, 300 groups of sample schemes are generated through the Advanced Latin Hypercubic Sampling method, and an automatic numerical simulation platform is setup to optimize the impeller under different working conditions. A metamodel of optimal prognosis is built by OptiSLang based on sample data and system response, seven variables with high sensitivity are screened out, and the NLPQL algorithm is adopted to carry out the optimization design to obtain the optimized model. The optimized model is, then, verified by the numerical simulation, and it is analyzed and compared with the original model from external characteristic curves and internal flow mechanism. The results show that: the match between the optimized design variables and the optimization objective is good; the weighted efficiency of the optimized pump is increased by 4.3%, the high efficiency zone is obviously enlarged and the shaft power is significantly decreased; the flow lines in the optimized impeller are obviously improved, the vortex is eliminated, and the velocity distribution is more uniform; the low pressure zone at the inlet of the vane is obviously reduced.

To improve the head and efficiency performance of an ultra-low specific speed centrifugal pump, this paper takes a marine magnetic-driven ultra-low specific speed centrifugal pump with a specific speed of 27 as the object of study. On the basis of the original model impeller with three blades, impeller A and impeller B with four blades of the same outer diameter and outlet widths of 4 and 2.5 mm were optimized and designed. Taking methanol as the medium, the impacts of factors such as the structure of the impeller, the aperture diameter of the throttling ring, and the cutting impeller outer diameter on the hydraulic performance of the ultra-low specific speed centrifugal pump are investigated. The influence of impeller structure, throttle ring aperture, cutting impeller outer diameter, and other factors on the hydraulic performance of an ultra-low specific speed centrifugal pump was explored. The study shows that the flow condition range of the original model impeller pump is very small, and the head decreases very fast, which cannot meet the design requirements; the head and efficiency of impeller A and impeller B are generally improved, but the flow or head deviates from the design condition, so it is necessary to set up a throttling ring or cut the outer diameter of the impeller to regulate the pump's operating parameters. The pump outlets were set up for the 12 and 15 mm inner diameter of the throttle ring and no throttle ring, respectively. Comparative experiments show that impeller A in the design head point using three kinds of throttle ring structure and the pump flow is greater than the design value of impeller B in the throttle ring bore diameter of 15 mm and that the pump flow and head can be achieved at the same time as the design value.

Compared to traditional centrifugal pumps, magnetic pumps are widely used in industries such as chemical, pharmaceutical, and petroleum due to their characteristics of leakage-free operation and the ability to transport toxic and corrosive fluids. However, the efficiency of magnetic pumps is relatively low. Improving the efficiency of pumps helps to reduce energy loss and lower industrial costs. In this study, a magnetic pump was chosen as the research subject. The study aims to improve the efficiency and stability of the magnetic pump by optimizing the impeller blades based on the load curve. A combined approach of a numerical simulation and experimental verification was used to investigate the impact of the anterior loading point (AL), posterior loading point (PL), and slope (SL) in the blade loading curve on the pump’s performance. The slope, which had the most significant impact on pump performance, was selected as the dependent variable to analyze the internal pressure pulsation and main shaft radial force of the magnetic pump. The research found that the hydraulic performance test results of the magnetic pump were in good agreement with the simulation results. When efficiency is used as the optimization objective, the anterior loading point should be moved as far back as possible, and the posterior loading point should be moved as far forward as possible. Through the study of internal pressure fluctuations and radial forces within the pump, the radial force distribution is sequentially as follows: the anterior loading method, posterior loading method, and middle loading method at a rated flow rate. The maximum pressure pulsation amplitude was near the volute casing diffuser area. Compared to the original pump, the optimized magnetic pump showed a 5.05% improvement in hydraulic efficiency under the rated conditions. This research contributes to enhancing the performance and efficiency of magnetic pumps, making them more suitable for various industrial applications.

The collapse of detached vapour clouds results in surface erosion, vibrations, acoustic radiation and loss of performance in hydraulic machines. This paper describes an experimental and numerical investigation of the impact of surface obstacles on cloud cavitation aggressiveness. An aluminium venturi was positioned in the test section of a cavitation tunnel and was exposed to sheet and cloud cavitation. Cross-flow obstacles consisting of rectangular rods of 2, 4 and 6 mm height were positioned at a fixed location on the venturi surface. The Reynolds number was varied between 71000 and 193000. Cavitation aggressiveness was assessed by analysing the frequency content and the amplitude modulation of Acoustic Emissions (AE). Numerical simulations of the cavitating flow were implemented in order to gain a deeper insight on the impact of the obstacles on cavitation. It was observed that the obstacles have the capability to shift the inception of cloud cavitation to a higher Reynolds number and avoid periodical perturbations near the surface. The root mean square value of the AE, which is representative of the cloud cavitation erosiveness, was reduced by 70%. Thus, it was confirmed that surface obstacles offer a simple and efficient solution to reduce the harmful consequences of cloud cavitation.