An analytical study on the vibration and energy flow behaviors of a coupled cylindrical shell-plate structure is presented. An analytical model capable of handling general boundary and coupling conditions is developed in which the interactions of all internal forces and moments for both the shell and plate have been taken into account at the junction via four types of coupling springs with arbitrary stiffness and covering all the degrees of freedom, and each of the plate and shell displacement functions is expressed as the superposition of a two-dimensional Fourier series and several supplementary functions. The unknown expansions coefficients are obtained using the Rayleigh-Ritz procedure. The effectiveness and accuracy of the present solution are validated against the FEM results. The energy flow behaviors through this structure are investigated through parametric power flow and structural intensity analysis. The contribution of internal forces or moments to the power flow and the influence of key system parameters on the energy flow are analyzed numerically, including coupling locations, coupling conditions, boundary conditions, and excitation location. The results shed light on the effects of system parameters on the energy flow behaviors of the class of coupled shell-plate structure.
The unsteady characteristics of tip-leakage flow in axial fans with circumferential skewed blades were investigated at off-design conditions using particle image velocimetry (PIV) and wall pressure test. Two circumferential skewed fans, with the blade skew angles at 8.3° forward and backward, respectively, were investigated in this study. The instantaneous flow field in tip clearance region was measured using PIV at peak pressure condition. The static pressure fluctuations near blade tip were captured at off-design conditions using pressure sensors mounted on casing wall. From the measured results, the structure and instantaneous characteristics of tip-leakage flow in circumferential skewed fans were analysed. The tip-leakage vortex instability and its relation with circumferential skewed blades, to expand stall-free operation range of axial fans, were discussed. The forward-skewed blade is found to be effective in controlling tip-leakage flow to expand stall-free operation range at off-design conditions.
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