Dynamic load identification is a commonly used and quite important approach to obtain the excitation loads of structures in engineering practice. In this paper, a novel dynamic load identification method combining the least squares time element method (LSTEM), wavelet scaling function and regularization method is proposed, which performs a better accuracy and a stronger anti-noise ability. It decomposes the time history of dynamic load into a series of time elements, and approximates the load profile at each time element using wavelet scaling functions. In order to balance the accuracy and efficiency for load identification, an optimal wavelet resolution is then determined. Simultaneously, the least squares time element model is derived which establishes the forward model for computing the wavelet coefficient. Finally, the wavelet coefficients for dynamic load identification are accurately and stably solved by implementing regularization. By this method, on the one hand, the wavelet scaling function and LSTEM improve the identification accuracy, and on the other hand, the integral process in the least squares operation gains the anti-noise ability for the load identification. A numerical example of a roof structure and an experiment of a composite laminate are studied and verify the effectiveness of the proposed method.
The vaned diffuser is advantageous in turbo-machinery which needs smaller size, so the vaned diffuser is widely used in the micro/small turbine engine. But the separation and strong mixing are often existent in the flow filed of such diffuser, and the viscous force, precision loss and frictional losses go up as size goes down, so the performance of micro diffuser is decreased. To improve the performance of diffuser in micro turbine engine, a new-style micro diffuser is presented in this investigation, which is composed of full blades and splitters. It is regarded as a series of ducts in design, and the effect of cross-section area distribution along the flow path on the new-style diffuser performance is studied. It not only can improve the performances, but also be easy to manufacture for micro turbine engines. The new-style micro diffuser was applied to replace the traditional vaned diffuser in an 11cm-diameter prototype engine, and the improvement of performance is verified by CFD and experiment. The advanced performance of the optimal micro diffuser (Cp above 0.65, σ above 0.9), is obtained with same external size.
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