Mechanism And Application Research Of Unsteady Flows In Gas Turbine

Gas turbine is the core component of the aero-engine, while the turbomachinery flow is inherentlyunsteady. Low pressure turbine always operate at the environment of low Reynolds number, as aresult the suction boundary-layer tends to separate. While the high pressure turbine blades have smallaspect ratio, which lead to large endwall secondary flow loss. Additionally, there exist strong trailingedge shocks in the highly-loaded transonic turbine. Research on these unsteady flows is crucial to thedesign of high performance turbine, deep investigations were conducted in this thesis.The in-house CFD software NUAA-Turbo was used in the thesis. Firstly, the Spalart-Allmarasturbulence model combined with a transition correlation, the sixth order WENO-SYM scheme, DESalgorithm, dual-time-step method and the Phase-lag algorithm were added on the base of the originedition, also the self-dependent gird generation method was developed.Next, the upstream bar and downstream T106A low pressure turbine blade were used to investigatethe unsteady wake-induced boundary layer transition. The separation induced transition, theconvection of wake through a turbine passage, the wake’s negative jet effect, and the wake’s inhibitingeffect on the laminar separation were perfectly captured. The unsteady interaction of the periodicalwake and the boundary layer was exhibited too. Research showed that the wake passing frequency isthe most important factor, the suction boundary layer separation could be controlled by the rationaluse of the upstream wakes, which is important to the improvement of LP turbine performance.After that, the CW-22high pressure turbine blade was used to investigate the endwall secondaryflow. The horseshoe vortex and the passage vortex were captured, also mechanisms of the formationand development of these vortexes were explained.The mechanism of the trailing edge shock in the highly-loaded transonic turbine was theninvestigated, as well as its control technology. The base region is the origin of the trailing edge shockand its loss, while the loss could be reduced by some controlling techniques.Finally, the GE-E3two-stage high pressure turbine was simulated for both steady and unsteady state.The steady case correctly predicted the performance parameter. The unsteady case captured theconvection of upstream wakes and trailing-edge shocks at the second-stage rotor blade. The bladeboundary layer and wake were found to be the most crucial resources of aerodynamic loss.