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        Prediction model of stall evolution stages in a centrifugal impeller based on characteristic analysis of the hydraulic torque of blades and support vector machine

        Luan Shi,Zhuqing Liu,Wei Yang,Yaojun Li,Xiaodong Liu,Ran Tao 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.10

        If a centrifugal impeller is in deep stall, it requires a large amount of additional energy to break free. As such, it is crucial to study the prediction method of impeller stall and establish its relationship with force and torque. This study employs a computational fluid dynamics numerical simulation method to analyze the flow field within the impeller of a centrifugal pump, while monitoring the changes in hydraulic torque of the blades. By examining the impeller’s internal flow field characteristics and external (energy performance) characteristics curves under different working conditions, the stall process was classified into three stages: germination, transition and stabilization. The evolution of stall cells under different stall stages was also analyzed. We utilized time-frequency conversion and analysis to extract characteristic parameters from instantaneous hydraulic torque results generated under different working conditions. A more effective model for predicting impeller stall stages was built by virtue of support vector machine algorithm. The proposed model exhibits improved feasibility and effectiveness in comparison to traditional prediction methods. It is expected to have significant implications for stable operation monitoring and safety protection of centrifugal pumps.

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        Magnetic and Structural Properties of MnBi<SUB>1-x</SUB>Ti<SUB>x</SUB> Alloys

        Suyin Zhang,Pengyue Zhang,HuanChang Jiang,Yaojun Shi,Nengjun Yu,Hongliang Ge 한국자기학회 2014 Journal of Magnetics Vol.19 No.3

        MnBi1-xTix (x = 0, 0.4, 0.7, 1) alloys were prepared by arc-melting, followed by heat treatment. X-ray diffraction (XRD) and vibrating sample magnetometer (VSM) were used to measure and investigate the phase structure and magnetic properties. The temperature dependent magnetization curves indicate that the phase transitions between LTP and HTP MnBi occur with heating or cooling in MnBi1-xTix (x ≤ 0.7) samples. However, MnTi samples are in Mn₂Ti single-phase, with very low magnetic properties. Furthermore, the coercivity exhibits a positive temperature coefficient. The results show that the optimal content of Ti for the coercivity of MnBi1-xTix alloy is x = 0.4. For MnBi sample, the coercivity reaches a maximum value of 1.13 T at 550 K. However, the remanence and energy product show apparent decrease with the addition of Ti in MnBi1-xTix alloys.

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