A High-Order LES Turbulent Model to Study Unsteady Flow Characteristics in a Low Pressure Turbine Cascade

Abstract

In this work, unsteady viscous flow analysis around Low Pressure Turbine (LPT) cascade using a High-Order LES (Large Eddy Simulation) turbulence model is carried out to investigate basic physical process. In the aerospace industry, input shaft power for fan and compressor components of turbine engines is most commonly supplied by the LPT. Considering this fact, in the endeavor of developing engines of increased efficiency and decreased weight LPT is an important component worth paying attention. Therefore, a better understanding of low-Reynolds number flow transition and separation behavior is very much essential to such improvements. Blades in the LPT environment may be designed for higher loading if the effects of passing wakes on bypass transition are properly included in the design. Also, under the LPT working conditions, boundary layers along a large extent of blade surface can remain laminar, even in the presence of elevated free-stream turbulence levels. The laminar boundary layers are then particularly susceptible to flow separation over the aft portion of blade suction surfaces, causing blockage in flow passages and a significant reduction in turbine efficiency. Related to weight reduction, the blade spacing in LPT can be increased with a rise in per blade loading. Increased blade spacing however, is accompanied by more extensive boundary layer separation on the suction surface of each blade due to uncovered turning, resulting in a further reduction of efficiency and additional wake losses. In the present work, experimental work is numerically simulated. Features of the flow-fields are described and compared with the experimental data on baseline case and active flow separation control using Vortex Generator Jet (VGJ).