Numerical And Experimental Investigation of Aerodynamics On Flow Around A Highly Loaded Low-Pressure Turbine Blade with Flow Separation Under Steady And Periodic Unsteady Inlet Flow Condition

摘要

Understanding the behavior of flow field around a turbine blade is of importance in gas turbine engineering and it can affect the design and performance of engine elements. An important phenomena that can affect the flow regime is the effect that impinging wakes, originating from stator blades, have on the flow around rotor blades. Reynolds Averaged Navier-Stokes (RANS) equation, in conjunction with turbulence models enables us to model flow fields. This study numerically and experimentally investigates the behavior of the boundary layer development along the suction and pressure surfaces of a highly loaded low-pressure turbine blade under steady and unsteady inlet flow condition. For unsteady case a range of reduced frequencies of the incoming wakes were modeled and studied. Also it includes a comprehensive assessment of predictive capability of RANS numerical tools. To evaluate the reliability of current RANS-based numerical method, a rigorous boundary layer and heat transfer measurement were done in unsteady boundary layer cascade facility of Turbomachinery Performance and Flow Research Lab (TPFL) of Texas A&M University. Aerodynamics experiments include measuring the onset of the boundary layer, its transition, separation and re-attachment using miniature hot wire probes. All measurements were performed for different wake frequencies and flow conditions and results were compared to the obtained simulation results. Comparisons of the experimental and numerical results detail the differences in predictive capabilities of the RANS methods in terms of the locating the onset and length of separation, velocity profile inside boundary layer, velocity fluctuations.