Влияние противодавления на аэроупругие колебания лопаточного венца последней ступени турбомашины в трехмерном потоке идеального газа

Abstract

Проведен численный анализ аэроупругого поведения лопаточного аппарата последней ступени турбомашины при различных значениях давления в конденсаторе с учетом неравномерности потока, вызванной лопатками статора и неравномерным в окружном направлении распределением давления за рабочим колесом из-за неосесимметричного патрубка, а также нестационарных эффектов, вызванных колебаниями лопаток. Предложенный метод решения связанной задачи позволяет прогнозировать амплитудно-частотный спектр колебаний лопаток, включая вынужденные, самовозбуждающиеся колебания и автоколебания с целью повышения экономичности и на- дежности лопаточных аппаратов турбомашин.

The turbomachine working process can be described as the conversion of the heat energy of actuating medium into the mechanical energy of rotary rotor, i.e. as the force interaction between the gas flow and the moving cascades. This process can be viewed as a steady-state process, due to its cyclic repetition at least each other rotor revolution. However, the main cycle is accompanied by many nonstationary phenomena that occur in aerodynamic cascades traversing the inhomogeneous field. Nonstationary flow behavior produces a considerable influence on the energy conversion in the turbine cascade, which results in the aerodynamic excitation of vibrations in the blade row. Aerodynamically excited vibrations of turbine and compressor blades can result in the structure failure and therefore the most important reliability and safety problem must be solved. This scientific paper gives the numerical simulation data for the 3D flow of an ideal gas through the last stage of the turbomachine at different pressure values in the capacitor taking into consideration the nonuniform flow caused by the stator blades, the nonuniform pressure distribution in the exhaust nozzle and nonstationary effects caused by blade vibrations. The numerical method is based on the solution of coupled aeroelastic problem for 3D flow of an ideal gas through the turbine cascade and the nonaxisymmetric exhaust nozzle, including the annular diffuser. The coupled problem was solved using a partial integral method including integral Euler equations and dynamic equations for vibrating blades (the modal approach) at each time step with the information exchange. This method of the solution of coupled aeroelastic problem allows us to predict the amplitude – frequency spectrum of blade vibrations, including forced self-excited vibrations and self oscillations to increase the efficiency and reliability of the blade rows of turbomachines.