The coreless microgenerators implemented in electromagnetic vibration energy harvesting devices usually suffer from power deficiency. This can be noticeably improved by optimizing the distribution of separate turns within the armature winding. The purposeful optimization routine developed in this work is based on numerical identification of the turns that contribute most to the electromotive force and the elimination of those with the least contribution in order to reduce the internal impedance of the winding. The associated mixed integer nonlinear programming problem is solved comparatively using three approaches employing surrogate models based on kriging. The results show very good performance of the strategy based on a sequentially refined kriging in terms of the ability to accurately localize extremum and reduction of the algorithm execution time. As a result of optimization, the output power of the system increased by some 300 percent with respect to the initial configuration.
The effects of composite motion involving action of torsion and axial moment on the vibrating element on characteristics of a new cantilever-type nonlinear electromagnetic vibration energy harvester are analyzed. The systems with softening and hardening action of the magnetic force are analyzed. The impact of the phenomenon on electromagnetic quantities of the system is investigated using the 2d analytical and 3d numerical models. The simulated and measured frequency-response characteristics show noticeable differences when the phenomenon is taken into account.
The paper proposes a solution to the problem of estimating the uncertainty of the output power with respect to the design parameters for an electromagnetic vibration energy harvesting converter. Due to costly utilisation of time-domain mathematical models involved in the procedure of determination of the average output power of the system, an algorithm for developing the surrogate model that enables rapid estimation of this quantity within the prescribed frequency band limits is proposed. As a result, the metamodel sensitive to the most impactful design parameters is developed using Kriging with successive refinement of the design grid for gaining the accuracy. Under operational conditions with a constant magnitude of the acceleration signal and the prescribed frequency band limits, the surrogate model enables evaluation of the average output power of the system at 105 design points in less than 2 s of computer execution time. The consistency and accuracy of the results obtained from the surrogate model is confirmed by comparison of selected results of computations with measurements carried out on the manufactured prototype. Based on the latter and the surrogate model, the confidence intervals for the design procedure were determined and the most important spread quantities were estimated, providing quantitative information on the accuracy of the design procedure developed for the considered system.
Розглянуто ресурсні можливості жароміцних матеріалів роторних деталей «гарячої частини» авіаційних газотурбінних двигунів (ГТД) і енергетичних установок (ГТУ) в прискорених термоциклічних випробуваннях. Показано можливість застосування розрахункового методу на основі емпіричної математичної моделі граничних термомеханічних напружень екстремальних рівнів, що діють у критичних точках деталей «гарячої частини» ГТД. При цьому припускається, що зразки матеріалів працюють на термоциклічних режимах, максимально наближених до умов роботи роторних деталей в критичних точках, що лімітують термін служби і призначений ресурс авіаційних ГТД та енергетичних ГТУ.Ключові слова: емпірична модуль, граничні статичні і термічні (термомеханічні) напруження, термомеханічні прискорені випробування, жароміцні матеріали, «гаряча точка» ГТД.
The considered resource possibilities of heatproof materials of rotor details of "hot part" of aviation turboengines (GTE) and power plants (PP) are in speed-up thermal-cycle tests. The shown possibility of applicationof calculation method is on the basis of empiric mathematical model of maximum thermo-mechanical tensions of extreme levels which operate in the critical points of details of "hot part" of GTE. It is thus assumed that the standards of materials work on the thermal-cycle modes of maximally close to the terms of work of rotor details in critical points which limit tenure of employment and appointed resource of aviation GTE and PP.
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