To reduce the vibration stresses arising in the working blades of turbines during resonant excitations caused by the frequency of passage of the blades of the nozzle apparatus, it is necessary to control the level of aerodynamic exciting forces. One of the ways to reduce dynamic stresses in rotor blades under operating conditions close to resonant, in addition to structural damping, maybe to reduce external exciting forces. To weaken the intensity of the exciting forces, it is possible to use a nozzle apparatus with multi-step gratings, as well as with non-radially mounted blades of the nozzle apparatus.This article presents the results of numerical calculations of exciting aerodynamic forces, as well as the results of experimental measurements of stresses arising in pairwise bandaged working blades with a frequency zCA ⋅ fn, where fn – is the rotor speed, zCA – is the number of nozzle blades. The object of research was the high-pressure turbine stage of a gas turbine engine. Two variants of a turbine stage were investigated: with the initial geometry of the nozzle apparatus having the same geometric neck area in each interscapular channel and with the geometry of the nozzle apparatus obtained by alternating two types of sectors with a reduced and initial throat area.The presented results are obtained on the basis of numerical simulation of a viscous unsteady gas flow in a transonic turbine stage using the SUnFlow home code, which implements a numerical solution of the Reynolds-averaged Navier-Stokes equations. Discontinuity of a torrent running on rotor blades is aggravated with heat drops between an ardent flow core and cold jets from film cooling of a blade and escapes on clock surfaces. Therefore, at simulation have been allowed all blowngs cooling air and drain on junctions of shelves the impeller.As a result of the replacement of the nozzle apparatus with a constant passage area by a nozzle apparatus with a variable area, a decrease in aerodynamic driving force by 12.5 % was obtained. The experimentally measured stresses arising in a pairwise bandaged blade under the action of this force decreased on average by 26 %.
The Influence of the Open Axial Clearance on the Gas Flow and Energy Losses in the Turbine Stage with a Shroud on Working Blades