Forschung auf dem Gebiet des Ingenieurwesens A

The star-wheel reducer has been regarded as a promising alternative solution for industrial power transmission where large transmission ratio and high power density are required. As one of the most overwhelming concerns in the early design stage of such kind of transmission device, its dynamic performance must be evaluated in advance to provide guidelines for vibration suppression and tolerance control. For this purpose, this paper proposes a methodology of dynamic modeling for the star-wheel reducer and analyzes the dynamic behaviors of the transmission system. By using the technique of substructure synthesis, an analytical elasto-dynamic model is established in which the effects of component compliances and manufacturing/assembling errors are included. The differential motion equations of each subsystem are derived with the 2nd Newtonian law. These differential motion equations are further assembled by the compatibility conditions among the subsystems to formulate a governing equation of the overall transmission system. Based on the established dynamic model, a modal analysis and a dynamic analysis are carried out to reveal the modal characteristics and the steady-state responses of the star-wheel reducer. The results show that the first 6 orders natural frequencies are ranging from 66.2 to 197 Hz and are much higher than the reducer’s input frequency of 16.7 Hz under input speed of 1000 r/min. In addition, the meshing forces of the two phases of star-wheel are similar only with a phase difference of 180°. Finally, a test-rig is set up to perform an experimental modal test and a vibration test. The satisfactory agreement between the experimental data and the theoretical simulation results proves the correctness and accuracy of the proposed dynamic model. The present study is expected to provide a fundamental framework for error controlling and performance enhancement of the star-wheel reducer.

Auf der Grundlage einer Energiebilanz für den Zirkulationsprozeß in Seitenkanalmaschinen werden die Kennliniencharakterostiken in Abhängigkeit physikalischer und geometrischer Größen aufgestellt und Optimalbereiche zum Erreichen günstiger Energieübertragungsverhältnisse und damit verbesserter Wirkungsgrade aufgestellt. Ergebnisse verschiedener Berechnungsverfahren werden gegenübergestellt. Die Einsatzgebiete der Seitenkanalmaschine als Bindeglied zwischen Strömungs-und Verdrängermaschine werden erläutert.

The paper contents the results of temperature and stress field calculations occurring in the cross-section of first tube of the platen superheater P3 in the boiler BP 1150 (steam capacity 1150t/h). The non-uniform heat flux distribution resulting from radiation (from flue gas in the superheater as well as from the furnace) and convection has been taken into account. Calculations have been carried out for two coals, with lower and higher heating value. Einfluss ungleichmäßiger Rohrbeheizung auf die Spannungen in Überhitzerrohren

Knowledge of the expected tooth root bending strength plays a decisive role in the design of gear sets. Due to dimensional and shape changes resulting from distortion due to the heat treatment, unintentional, partial grinding in the tooth root area may occur, particularly in the application range of large gears. The influences of an unintentional grinding zone on the tooth root bending strength have not yet been clarified with sufficient accuracy. As a result, grinding zones lead to uncertainties when evaluating the tooth root bending strength and thus to a loss of time and cost in the field of industrial practice. This paper presents experimental investigations on the influence of grinding zones on the tooth root bending strength of case carburized gears. For the experimental investigations, there are three unground reference variants with different blasting treatments: non-blasted, mechanical cleaned by shot blasting and shot peened. The unground reference variants are examined regarding their tooth root bending strength. For the other test gear variants, different grindings zones are applied resulting in light and strong material removal by grinding. The variants with the different grinding zones are examined analogously regarding their tooth root bending strength and are subsequently compared to the reference variants. The results of the experimental investigations show that grinding zones can have diverse influences on the tooth root bending strength of case carburized gears – Non-blasted gears do not show changes regarding the tooth root bending strength with regard to light or strong grinding zones applied within this investigation. – Shot blasted (mechanical cleaned) gears show no change in the tooth root bending strength for light grinding zones (grinding application does not significantly alter the original residual stress state in the tooth root area). – Shot blasted (mechanical cleaned) gears show a reduction of the tooth bending strength of up to 20 % with regard to strong grinding zones (grinding application does significantly alter the original residual stress state in the tooth root area). – Shot peened gears show a behavior similar to that of shot blasted gears with reductions of the tooth root bending strength of up to 30 %. – Shot peening the strong grinding zones as a repair measure can increase the reduced tooth root bending strength again. However, for the investigated test gears, the resulting tooth root bending strength was below the shot blasted reference variant. The results of this paper help to evaluate the influence of grinding zones on the tooth root bending strength of case carburized gears more precisely compared to the generalized reductions of current standards and classifications. The results can be incorporated in standards such as DIN 3390 as well as ISO 6336 and can be applied in the field of industrial practice. Eventually, the findings help to reduce the current loss of time and cost caused by uncertainties regarding grinding zones.

Some interesting studies are made in this paper on the life management of a composite wind turbine blade. It presents the details of finite element modeling and validation, blade response under service loading conditions, power coefficient evaluation for the optimum design parameters of the blade configuration, development of failure envelope and fatigue life estimations. Finite element analysis results are found to be in good agreement with existing test results on a typical composite blade configuration. The failure envelope generated from the present modified failure criterion correlates well with the test results on different composite materials. The procedure adopted in this paper can be utilized for optimum design of large size composite wind turbine blades.