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21.
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对电动增压器用低比转速离心压气机轮毂轮缘进行优化设计。采用NUMECA/FINE Design 3D对压气机进行几何参数化,生成数据库样本,利用人工神经网络和遗传算法对轮毂轮缘型线进行优化,并进行流场分析。仿真结果表明,在设计转速为40000 r/min时,优化后设计点压比和效率分别提高6.59%和3.73%。 相似文献
23.
《全球能源互联网(英文)》2020,3(4):313-323
Recently, power electronic transformers (PETs) have received widespread attention owing to their flexible networking, diverse operating modes, and abundant control objects. In this study, we established a steady-state model of PETs and applied it to the power flow calculation of AC–DC hybrid systems with PETs, considering the topology, power balance, loss, and control characteristics of multi-port PETs. To address new problems caused by the introduction of the PET port and control equations to the power flow calculation, this study proposes an iterative method of AC–DC mixed power flow decoupling based on step optimization, which can achieve AC–DC decoupling and effectively improve convergence. The results show that the proposed algorithm improves the iterative method and overcomes the overcorrection and initial value sensitivity problems of conventional iterative algorithms. 相似文献
24.
本文采用拉伸试验、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等手段,研究了7B04铝合金在施加和不施加直流电条件下,经470℃固溶和100-140℃时效处理后的组织和力学性能。与传统的T6处理(470 oC/30 min+120 oC/24h)相比,固溶和/或时效处理时施加500A的电流,可显著提高GPII区的析出密度,进而提高峰时效状态下的拉伸强度和延伸率。固溶过程中施加直流电可将随后时效合金达到峰值强度的时间明显缩短12h。 相似文献
25.
The addition of surfactants to modify the surface property of nanoparticles (NPs) from hydrophilic to hydrophobic also enhances their interfacial properties. Several approaches were previously proposed to calculate the surface tension/interfacial tension (IFT) for different systems in the presence of NPs, surfactants, and electrolytes. However, most of these approaches are indirect and require several measured parameters. Therefore, a mathematical model is developed here to calculate the surface tension/IFT for these systems. The developed model takes into account the cohesive energy due to the interaction of the surfactant CH2 groups, the electric double layer effect due to the interaction among the ions of NPs, surfactants, and electrolytes, and the dipole–dipole interaction of NPs and electrolytes. The developed model is compared and validated with the laboratory experimental data in literature. The results reveal further understanding of the mechanisms involved in stabilization of oil/water emulsion in the presence of NPs, surfactants, and electrolytes. 相似文献
26.
针对现有电动阀门控制系统可嵌入性差的问题,设计了一种基于CAN总线的网络化、多通道、开度型阀门嵌入式控制系统。其中,上位机主要用于下达各阀门开度等控制指令并同时监测其工作状态,而下位机采用双MCU架构,主MCU用于控制各阀门的开度大小,从MCU负责采集开度反馈电流以实现闭环控制。下位机采用了模糊PID算法进行控制参数的动态整定,可满足阀门在不同工况下的控制精度要求,并通过OLED屏显示各通道阀门的实际开度值。实验表明,该控制系统运行稳定,能实现对多通道开度阀的精准控制,控制精度在0.6%以内,并支持远程上位机控制和现地控制等多种工作模式。 相似文献
27.
28.
Harry Charalambous Shikhar Krishn Jha Kent Harrison Christian Ryan Thomas Lay Thomas Tsakalakos 《Journal of the European Ceramic Society》2018,38(10):3689-3693
In conventional flash sintering, the current rises nonlinearly to a set current limit, accompanied by a spike in the power density. This sudden power spike may cause hot spot formation, in which current preferentially channels through a small area, causing localized melting while other areas remain unsintered. By using a controlled current ramp early on the sudden power spike can be avoided. In addition, by changing the ramp rate material properties such as porosity, grain size and conductivity can be tuned. 相似文献
29.
Guilherme S. Pandolfi Felipe G. Pinheiro Rodrigues Paulo J. Modenesi 《Welding International》2018,32(3):188-199
This paper evaluates indications of arc constriction by the thermal and electrical insulation caused by oxides of a single component in A-TIG welding of austenitic stainless steels. Changes in arc dimensions, in its electric voltage and in weld bead morphology caused by three oxide fluxes (SiO2, Cr2O3 e Al2O3) applied with two surface densities (30 e 60 g/m2), and with and without a flux-free central strip (of 1, 2 and 4 mm) were studied. Results showed no significant change in the width of the electric arc for the experimental conditions used, therefore not supporting a possible mechanical constriction in the electric arc by oxide electrical and thermal insulation. Lateral filming indicated that the arc is delayed by the fluxes with silica causing the strongest effect. The presence of a clean central strip in the flux layer decreased weld penetration and weld bead cross section, besides the reduction of the width of the bead. Therefore, the results of the present work seem to support Marangoni convection as the main mechanism responsible for increasing penetration in A-TIG welding of stainless austenitic steels. 相似文献
30.
《Journal of the European Ceramic Society》2020,40(11):3766-3770
Ceramic varistors are electronic components which have a sharp change (over several orders of magnitude) of their electrical resistance at a well-defined voltage (switching voltage). Starting at low voltages, the resistance is large. But by exceeding the switching voltage the resistance drops dramatically and the component acts as a good conductor. Mounted parallel to a consumer, they are used as protection devices against over voltage loading. In the technical routine yearly billions of varistors are used to protect power lines, transformation stations, electronic devices, microelectronic systems or even LEDs.In service large temperature differences may come into existence, which cause severe mechanical stresses that even may destroy the components. The basic principles of the varistor behaviour are explained and examples of mechanical failure are discussed. 相似文献