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.

In this paper, a transonic compressor cascade was optimized to improve its aerodynamic performance. A new blade parameterization method with 16 control variables was first proposed to fit the shapes of the suction and the pressure side, as well as the leading edge. Then, the Kriging surrogate-model-based genetic algorithm (GA) was used to optimize the performance of the transonic cascade. The optimization algorithm is effective in reducing the total pressure loss while extending the working range of the cascade. The results show that the total pressure loss coefficient could be reduced by 11% at the best airflow angle and the working range could be extended by 6.9% for the optimized cascade in two-dimensional simulations. Similar improvement results could also be obtained in the simulations of their linear cascade cases. Detailed analyses show that the relative maximum thickness positions of the optimized blades move forward by about 10% to the leading edge, and the radii of curvature of the front half of the suction and pressure surfaces increase, compared with the initial blade. This makes the front half of the optimized blades look more closely like a wedge. Consequently, the passage shock strength is reduced and the shock changes from the passage normal shock to oblique shock. The weakened shock strength leads to the disappearance of the flow separation caused by the shock boundary layer interaction on the suction surfaces of the optimized blades, and results in a narrowed wake width at the outlet section.

The large superconducting magnet are widely used and play an important role in nuclear fusion device, high-energy accelerator, space target infrared and other forefront fields. In this paper, we design several cryogenic centrifugal compressor stages for helium refrigerator with 3.3K∼11K inlet temperature, used in exhausting the low-pressure and low-temperature saturated helium steam, further producing superfluid helium and cooling the large superconducting magnet. Due to the cryogenic compressor running environment and the internal structure, about 30W heat leakage from impeller hubs and the end of shafts into the flow passages are unavoidable, and it is necessary to consider this heat leakage in the centrifugal compressor impeller design. Firstly, adding the heat leakage into thermodynamic process and centrifugal compressor effective formula, then adjusting the inlet and outlet design parameters according to the heat transfer rate and make the preliminarily designs of each stage of the compressor. Four different methods for varying p design condition parameters are compared by CFD simulation. The 3-D impellers are designed by the Streamline Curvature Method, and the vaneless diffusers and volutes are designed by the inlet and outlet section aerodynamic parameters. When the best design method is determined, the blade profiles are further adjusted in order to improve the stage performance. Finally, the characteristic curves under variable working conditions and the generalized stage performance curves of each stage are calculated. In this paper, we delve into a high efficiency centrifugal compressor stage design method with the consideration of heat transfer effect. In the next step, more running data will be obtained after the further experiments and the long-term operation.

Large axial-flow fans have found wide applications in many fields, such as the fans used for boilers in power stations, the fans in ventilation systems for coal mines and the fans for wind tunnels. The power consumption of those large axial-flow fans is often high up to several thousand kilo-Watts. Because of this, the aerodynamic performance improvement of the axial-flow