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Squirrel cage fans (SCFs) are widely used in a variety of household appliances. Due to the restriction on installation size, the design of high-efficiency SCFs with high flow capacities is an important topic. In this study, we proposed a novel rounded rectangle volute profile (RRVP) for the design of compact high-flow SCFs. At first, we used computational fluid dynamics (CFD) to simulate the aerodynamic performances of three SCFs having the same impeller but different volutes, which were the common logarithmic-spiral volute profile, the cutting volute profile, and the RRVP volute at the maximum flow rate working condition. The CFD simulations indicate that the fan with RRVP volute has the highest flow rate at the maximum flow rate working condition. Then, we proposed a parameterization method for the RRVP with 16 control variables. The multiobjective evolutionary algorithm based on decomposition (MOEA/D) and Kriging model was used to optimize the aerodynamic shape of the compact SCF with an RRVP volute. Twenty-three control variables were used in the multiobjective optimization process, including the optimization of the blade angles and the impeller position. Optimization results show that the maximum volumetric flow rate of the optimal SCF with an RRVP volute increases from 147.1 cubic feet per minute (CFM) to 191.1 CFM, and the fan efficiency also increases from 32.21% to 33.5%, compared with the original SCF with the common logarithmic-spiral volute. Two main factors were found to increase the flow capacity and efficiency of the optimal SCF under strict size constrains. First, the RRVP became smooth and large, which reduced the flow loss and increased the flow cross-section; second, the eccentrically mounted impeller of the optimal fan enlarged the flow section near the outlet of the volute. [ABSTRACT FROM AUTHOR]

In this paper, we build a model for calculating the drag coefficient and ultimate settling velocity of high-density and large-diameter solid particles in cylindrical pipes. The settling process of particles in a cylindrical pipe was recorded by using a high-speed camera. Based on the analysis of the experimental data, a gap area ratio was introduced into the model in order to predict the resistance coefficient and ultimate settling velocity of the particles settling in the open space, enabling the model to predict the resistance coefficient and ultimate settling velocity of spherical particles settling in cylindrical pipes. The values of the ultimate settling velocity and the drag coefficient that were obtained with the proposed formulas were validated using experimental data and computational fluid dynamics results. The model was found to be accurate and reliable. [ABSTRACT FROM AUTHOR]

A novel full-process test bench was developed to replace lengthy and costly deep-water experiments. This platform can accurately simulate the dynamic characteristics of hydrokinetic turbines and can be used to evaluate their power-supply capabilities under various conditions. The hydrokinetic turbine power model was established by obtaining discrete performance data through experimentally validated computational fluid dynamics simulations and building surrogate models using the response surface methodology. This approach offers higher accuracy and broader applicability than empirical models. Moreover, a stepper motor platform based on a speed control scheme is proposed for the first time that can achieve high-precision transient simulation with a simplified control mechanism. This platform was employed to assess the power supply capacity of two hydrokinetic turbines under constant and typical deep-sea flow speeds. The ductless Archimedes screw hydrokinetic turbine was found to be more suitable for the deep water application than the high-solidity horizontal axis turbine due to its high self-start capacity and power coefficient. Furthermore, a case study was conducted on the design of a deep-sea in-situ power generation system at Luzon Undercurrent. Results suggest that a ductless Archimedes screw hydrokinetic turbine with a 1000 mm radius can comfortably cater to the energy demands of miniature AUVs. [Display omitted] • A test bench is developed for deep-water in-situ power generation systems. • A stepper motor is controlled to reproduce the turbine characteristics. • Power generation of various turbines is assessed based on the test bench. • A case study is performed for the Luzon Undercurrent application. [ABSTRACT FROM AUTHOR]