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This research revolves around the ventilation system of range hoods and discusses the optimization of the flow field from the perspectives of reverse engineering (RE), the Taguchi method (TM), and computer aided engineering (CAE). These were integrated to develop an impeller system with an optimized air discharge volume. Analyses show that the arc length of the blades and the deflection angle of the impellers are the most prominent factors affecting the volume of the air discharge. A maximum air discharge volume was achieved during the experiment with 54 blades and a deflection angle of $65^{\circ }$, which is an enhancement of 17.5% in comparison with that of the original design. In an environment with shortened product life cycles, the results from this research are expected to improve the air discharge efficiency of impellers and effectively reduce the time needed for the development of ventilation systems.

This paper focuses on the efficiency improvement of a centrifugal fan used in a vacuum cleaner. In order to check the performance of the centrifugal fan system, computational fluid dynamics (CFD) analysis is used. The numerical simulation with CFD tool is carried out with RNG $k-𝜀$ two-equation turbulence model based on Reynolds-averaged Navier–Stokes equations. To perform the coupling between rotating impeller and stationary area, the multiple reference frame (MRF) model is used. The numerical results of the fan are validated against with experimental results and are found to be highly reliable. The design and optimization of diffuser and impeller of a centrifugal fan are realized by using numerical investigations. For reducing the kinetic energy loss inside the fan, a guide baffle is added to optimize diffuser. The optimization results show that overall efficiency of the fan is improved by 5.27% and considering the lower efficiency of impeller caused by blockage at the blade inlet, etc., the design of impeller with long-short blades is proposed. Several cases of affecting factors under different operating conditions are simulated. Relative length (denoted as $\sigma$) and circumferential position of short blades are chosen as design variables. It is found that the efficiency of a fan with a relative length of 0.7 can be increased by 9.34%, and the best circumferential position of short blades is between two adjacent long blades.

To reduce the calculation cost and improve the accuracy of flow field prediction, an adaptive proper orthogonal decomposition (APOD) surrogate model based on K-means clustering algorithm was proposed to reconstruct the flow field of impeller. The experiment samples were designed by introducing the perturbation of the blade control parameters such as blade wrap angle and blade angle of outlet. K-means clustering algorithm was used to classify the sample blade shapes, and find out the cluster of the objective blade. The snapshot set, which consisted of the blade shape and the flow field data of impeller, can be described as a linear combination of orthogonal basis by POD method. The radial basis function (RBF) was used to fit the orthogonal basis coefficients of the objective blade, and then the flow field of objective impeller was reconstructed. The traditional fixed sample POD (FPOD) method and the proposed APOD method were used to reconstruct the flow field in impeller, respectively, and the prediction results of the two methods were compared and analyzed. The results show that the proposed APOD method could quickly and accurately reconstruct the objective flow field. The flow field prediction accuracy of the APOD method is significantly higher than the FPOD method, and the calculation time for the flow field prediction is less than 1/360 of the CFD.

Impellers of centrifugal compressors are generally loaded by fluctuating aerodynamic pressure in operations. Excessive vibration of the impellers can be induced by unsteady airflows and lead to severe fatigue failures. Traditional transient stress analyses implemented in time domain generally require multiple load-step, very time-consuming computations using input of temporal pneumatic force previously obtained from Computational fluid dynamics (CFD) analyses. For quick evaluation of structural integrity of impellers, it is necessary to develop random vibration models and solution approaches defined in frequency domain. In this paper, the Pseudo-Excitation Method (PEM) is used to obtain power spectral density of three-dimensional, dynamic displacement and stress of impellers. A finite element model of an unshrouded impeller of a centrifugal compressor is generated based on the result of unsteady CFD analysis. Compared with the direct transient stress analyses in time domain, the pseudo-excitation method provides accurate and fast estimation of dynamic response of the impeller, making it an applicable and efficient method for analyzing random vibration of impellers.

In this study, a numerical study has been carried out to analyze the factors of the efficiency decrease at backward flow situation in an axial fan with adjustable blades. The analysis is done with the pitch angle of 36° on the forward flow and of -26° on the backward flow. The numerical results show that the air flow rates of the pitch angle of 36° and -6° are calculated to be 285 cubic meter per min (CMM) and 212 CMM, respectively. The results are similar to the experimental results by Chang et al.¹ The results had the maximum error of 10.6% compared with the experimental results. The fan efficiency decrease is caused by the fact that the axial fan used for this study was designed for the forward flow. As the results, the pitch angle of -26° has induced the recirculation around the impeller blade, impeller cover and downstream. This recirculation caused the large decrease in total pressure coefficient. This turned out to be the main cause of the efficiency decrease.

In this paper, analytical algorithms and advanced computer simulation package was used to study the performance of a pumping system and the best angle of attack for a Shape Memory Impeller by comparing the analytical algorithm and simulation. From the results, it shows that the best angle of attack is 12 degree at the outlet angle with respect to the inlet angle. Increasing the angle of attack from 35 degree to 45 degree at the outlet there is huge increase in flow rate by 63.47% and slight decrease in the impeller Torque from 35 degrees to 42 degrees by 0.72%. This study successfully conceptualised a Shape Memory Smart Centrifugal Impeller that will increase fluid flow rate through a given system if the fluid temperature increases above a given transition temperature using NiTi Shape Memory Alloys was achieved.