Time domain bidirectional iteration-based turbine vane flutter stress forecasting method

Abstract

The invention discloses a time domain bidirectional iteration-based turbine vane flutter stress forecasting method. The method is characterized in that: a set of bidirectional iteration method for a time domain is designed by taking a vane and a surrounding flow field thereof as a three-dimensional fluid solid coupling system, and the flutter stress of the vane is obtained by alternately solving vane deformation and unsteady flow field. The method comprises the following steps of: setting a structural calculation module, a fluid calculation module, a data conversion module, a flutter stress output module, an initial value calculation module and a bidirectional iteration module in a computer; acquiring static vane deformation and steady flow field serving as an initial value by nonlinear iteration; alternately calling the structural calculation module and the fluid calculation module to propel the whole system on time; transmitting fluid solid boundary information through the data conversion module; and outputting the flutter stress on time history. The method realizes integrated calculation of the vane and the flow field, takes the nonlinearity of the coupling system into consideration, and can allow the observation of the whole flutter development process and forecast the flutter stress of the vane.

Description

(1) Technical field [0001] The invention relates to a method in the field of computer-aided analysis tools, in particular to a method for predicting flutter stress of turbine blades based on time-domain bidirectional iteration. The invention belongs to the technical field of impeller machinery simulation. (2) Background technology [0002] At present, in the turbomachinery, there is a complex interaction between the vibrating blade and the surrounding fluid. The elastic blade affects the flow field through its deformation, and the disturbance of the flow field changes the shape of the blade in turn. Among such fluid-structure interaction phenomena, flutter has the greatest impact on structural reliability. Flutter is a kind of self-excited vibration. The unsteady aerodynamic force on the blade surface comes from the motion of the blade itself. The unsteady aerodynamic force and the unsteady motion of the blade are mutually causal and increase in cycle, which makes the blade...

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Problems solved by technology

[0004] First of all, the traditional energy method and eigenvalue method both assume that the blade moves in a given form, isolate the flow field and the blade motion, ignore the influence of the deformation of the elastic blade itself on the flow field, and rarely consider the centrifugal force on the blade deformation. and the influence of the flow field, it is impossible to realize the integrated calculation of aerodynamics and structure, and there are large calculation errors

[0005] Second, due to the strong nonlinearity in both fluid and structure, the nonlinearities in these two domains superimpose alternately, forming a more complex coupled nonlinearity

The existing flutter prediction methods all introduce a large number of linearization assumptions, and even only use one-way transmission from the structure to the fluid, which weakens or even eliminates the coupling nonlinearity, cannot accurately describe the nonlinear phenomenon, and reduces the simulation accuracy

[0006] Thirdly, existing methods cannot show the entire time course of flutter development, nor can they obtain flutter stress, which is just a very important indicator of flutter phenomena

[0007] Finally, the previous time-advance-based turbine flutter numerical simulation methods all use a fixed time step, which cannot be effectively adjusted in the calculation, resulting in low calculation speed and efficiency, and even difficulty in convergence; and most The use of commercial structural finite element calculation software requires repeated manual intervention in the calculation, and the entire calculation process and algorithm cannot be optimized within the software for the characteristics of fluid-solid coupling calculations, which increases operational complexity and reduces calculation efficiency. Existing forecasting methods based on time advancement have high calculation costs and poor economy

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