Numerical Investigation of the Influence of Circumferential Flow Inhomogeinity on the Power Loading of HPT Blades

Анотація

One of the methods used for the reduction of dynamic stresses in turbine blades when operating conditions are close to resonance conditions can be the reduction of external exciting forces. This scientific paper gives the data of  numerical investigation of the influence of circumferential inhomogeneity before the turbine wheel on the level of nonstationary aerodynamic forces applied to turbine blades. With regard to the numerical flow simulation the full temperature field inhomogeneity was specified at the turbine inlet including the film deposition of the nozzle diaphragm. Nonstationary flows in the high pressure turbine stage were calculated for the three geometrical options of nozzle diaphragm: 1 – the initial geometry has the same area of geometric throat in each blade channel; 2 – the geometry obtained by the interlacing the two types of sectors; each includes three channels that have the enlarged area а₂ or the reduced area а₁ of throat; 3 – the geometry obtained by the interlacing of channels that have the enlarged area а₂ or the reduced area а₁ of throat; Using the Fourier –analysis data for nonstationary forces the spectral analysis of the dynamic component of these forces was done. A decrease in the level of nonstationary aerodynamic forces of z∙fn frequency was obtained for the turbine blade, where fn is the rotor speed, z is the number of blades in the nozzle diaphragm.