Shock Resistance Design of High-Speed Maglev Motor–Stability Considerations and Quantitative Shock Tests

Large external disturbances (such as shock loads) can cause contact between the rotor and touchdown bearings (TDBs). Hence, maintaining the stability of systems with active magnetic bearings (AMBs) is a major challenge for mobile applications such as on-board steam turbines or vehicle turbochargers. In this paper, two key factors (power bandwidth and bi-stable characteristic) that affect the shock stability of AMB-rotor systems are considered in the design of a high-speed maglev motor. Insufficient power bandwidth can induce current saturation leading to destabilization, while a bi-stable characteristic can cause persistent contact between the rotor and TDBs under external disturbances. Theoretical analyzes and criteria are provided, and the influence of these two factors is investigated by base shock experiments of a high-speed maglev motor. These experiments involved mounting a high-speed maglev motor on a shock table then subjecting it to shock loads of different amplitudes. The designed motor continued to operate stably under shock loads up to 20 G, verifying the correctness of the stability considerations.

New Approach of Metal Substrate Fabrication for Metal-Supported Solid Oxide Fuel Cells

Metal-supported fuel cells (MSCs) offer potential material cost and robustness advantage over anode supported cells (ASCs). Because of the very good thermal shock stability of such MSCs, these can be heated up very quickly. However the challenge co-firing of metal substrate and electrolyte stays still unsolved. The production of the core component, the tape casted metal substrate, with defined shrinkage resulting from modification of metal powders is presented in the paper. This approach leads to an adjustment of the shrinkage mismatch during sintering, between metal and ceramic components, and adjustment of target specifications like porosity, green density and layer thickness.

Trigger low-voltage devices electromechanical apparatus

Based on the analysis of the existing classification of low-voltage electromechanical devices, it was proposed, on the basis of the functions performed, to unite into the group of electromagnetic mechanisms the indicating relays, vacuum contactors, time relays with clockwork, and executive bodies of circuit breaker releases. The definition of launching devices is given, the main feature of which is a mechanical characteristic, the change of which, with appropriate coordination with the traction characteristic of an electromagnet, can lead to an improvement of the most important characteristics of these devices, such as power consumption and resistance to mechanical influencing factors. On the example of the calculation of the index relay, it is shown and experimentally confirmed that a change in the initial force of the mechanical characteristic and its rigidity leads to a decrease in power consumption while maintaining shock stability.

Osher Flux with Entropy Fix for Two-Dimensional Euler Equations

We compare in this paper the properties of Osher flux with O-variant and P-variant (Osher-O flux and Osher-P flux) in finite volume methods for the two-dimensional Euler equations and propose an entropy fix technique to improve their robustness. We consider both first-order and second-order reconstructions. For inviscid hypersonic flow past a circular cylinder, we observe different problems for different schemes: A first-order Osher-O scheme on quadrangular grids yields a carbuncle shock, while a first-order Osher-P scheme results in a dislocation shock for high Mach number cases. In addition, a second-order Osher scheme can also yield a carbuncle shock or be unstable. To improve the robustness of these schemes we propose an entropy fix technique, and then present numerical results to show the effectiveness of the proposed method. In addition, the influence of grid aspects ratio, relative shock position to the grid and Mach number on shock stability are tested. Viscous heating problem and double Mach reflection problem are simulated to test the influence of the entropy fix on contact resolution and boundary layer resolution.