Additively Manufactured Winding Design for Thermal Improvement of an Oil-cooled Axial Flux Permanent Magnet Machine

This article proposes a new additively manufactured winding with integrated heat sinks to improve thermal performance of an oil-cooled yokeless and segmented armature (YASA) axial flux permanent magnet machines. The heat sinks featuring pin-fin structure are integrated to the two sides and top of the winding to increase the heat transfer area and convective heat transfer coefficient, thus improving the thermal performance. Computational fluid dynamics is employed to evaluate the thermal performance of the proposed winding, which is further compared with that of the state-of-the-art rectangular winding. Besides, the influence of pin spacing in streamwise direction, tilt angle, flow rate and resistances on the thermal performance and pressure drops of the proposed winding are investigated. Finally, prototypes of the proposed winding and the counterpart rectangular winding are manufactured to verify the numerical analyses. The experimental results show that the winding temperature of the proposed winding can be reduced by 27.6 °C compared with that of rectangular winding

Experimental study on dynamic characteristics of shipboard steam power system under rapid and large disturbance of generating power

ObjectivesThis study seeks to explore the dynamic response characteristics of a marine steam power system under the condition of rapid and large power disturbance. MethodsA complete set of onshore experimental devices for a steam power system is established, and the dynamic response characteristics are studied by applying power disturbance by simulated load. ResultsThe experimental results show that under the condition of a single period disturbance, the fluctuation range of the drum pressure is within ± 1.5% and that of the propeller speed is within ± 2.5%; under the condition of continuous periodic disturbance, the fluctuation range of the drum pressure is within ± 2.5% and that of the propeller speed is within ± 3.5%; during the experiment, the steam power system generally runs in a stable manner. ConclusionThe results of this study can provide technical support for the actual operation and use of steam power systems

Convective Heat Transfer Characteristics on End-Winding of Stator Immersed Oil-Cooled Electrical Machines for Aerospace Applications

The stator immersed oil cooling has emerged as a promising thermal management method for high power density electric machines applied in aerospace applications. However, due to the complex geometry of end-winding, the research on the convective heat transfer coefficient (CHTC) for the flooded stator is still at infancy. This article investigates the convective heat transfer characteristics on end-winding of stator immersed oil-cooled electrical machines by computational fluid dynamics (CFD) methods and experiments implemented on a motorette. The variation law of the CHTCs of end-winding with flow rate is thoroughly investigated. Subsequently, new dimensionless correlations are defined using Nusselt numbers as a function of Reynolds numbers, which are further applied into a detailed lumped-parameter thermal network (LPTN) for rapid evaluation of temperature distribution. Finally, the obtained simulation results are verified by local temperature measurements. The experimental results also show that the proposed stator immersed oil-cooled structure can withstand a current density of up to 30 A/mm2 with a corresponding continuous power density of 6.8 kW/kg

The Processing Map of Laser Powder Bed Fusion In-Situ Alloying for Controlling the Composition Inhomogeneity of AlCu Alloy

In-situ alloying is a facile method for exploring high-performance metallic materials for additive manufacturing. However, composition inhomogeneity is inevitable, and it is a double-edged sword for the properties of in-situ alloyed parts. Appropriately controlling the composition inhomogeneity benefits the applications of in-situ alloying in specific microstructural and properties design. In this work, the Al20Cu alloy was selected as the benchmark alloy to investigate the tailoring of composition inhomogeneity. The morphology and area percentage of composition inhomogeneity in the as-built samples were firstly analyzed. These results provided evidence for the formation of composition inhomogeneity and indicate that its content is tightly dependent on processing parameters. The characteristics of the molten pool under various processing parameters were investigated by modeling the laser remelting process. Based on these, a processing map was established to guide the tailoring of composition inhomogeneity. This study expands the understanding of the formation mechanism of composition inhomogeneity in in-situ alloyed parts and sheds light on employing laser powder bed fusion in-situ alloying for new materials development

The State Journal

Weekly newspaper from Mulhall, Oklahoma that includes local, state, and national news along with advertising. Established December 19, 1902