Detached Eddy Simulation of Film Cooling Performance on the Trailing Edge Cutback of Gas Turbine Airfoils

Abstract

The present study deals with the unsteady flow simulation of trailing edge film cooling on the pressure side cut back of gas turbine airfoils. Before being ejected tangentially on the inclined cut-back surface, the coolant air passes a partly converging passage that is equipped with turbulators such as pin fins and ribs. The film mixing process on the cut back is complicated. In the near slot region, due to the turbulators and the blunt pressure side lip, turbulence is expected to be anisotropic. Furthermore, unsteady flow phenomena like vortex shedding from the pressure side lip might influence the mixing process (i.e., the film cooling effectiveness on the cut-back surface). In the current study, three different internal cooling designs are numerically investigated starting from the steady RaNS solution, and ending with unsteady detached eddy simulations (DES). Blowing ratios M = 0.5; 0.8; 1.1 are considered. To obtain both, film cooling effectiveness as well as heat transfer coefficients on the cut-back surface, the simulations are performed using adiabatic and diabatic wall boundary conditions. The DES simulations give a detailed insight into the unsteady film mixing process on the trailing edge cut back, which is indeed influenced by vortex shedding from the pressure side lip. Furthermore, the time averaged DES results show very good agreement with the experimental data in terms of film cooling effectiveness and heat transfer coefficients. Transactions of the ASME Downloaded From: http://turbomachinery.asmedigitalcollection.asme.org/ on 09/18/2013 Terms of Use: http://asme.org/terms Journal of Turbomachinery APRIL 2006, Vol. 128 / 299 Downloaded From: http://turbomachinery.asmedigitalcollection.asme.org/ on 09/18/2013 Terms of Use: http://asme.org/terms

DES study of blade trailing edge cutback cooling performance with various lip thicknesses

“…Martini et al. [28] [29] [21] [22]) are adopted here to evaluate the heat transfer coefficient at the pin-fin surfaces inside the cooling passage, the discharge coefficient, the film-cooling effectiveness along the protected wall surfaces, the shedding frequency of the wake flow and the dynamic thermal mixing between the mainstream hot gas flow and the cold coolant gas, etc. Table 1 gives the summary of numerical test conditions applied in the present studies.…”

“…Similar to the grid resolution, the time-step must also be small enough to guarantee a sufficiently fine temporal resolution for the unsteady flow effects. With respect to these requirements, a small time-step size of 1.25 × 10 -5 seconds is applied in these computations when considering the shedding frequency obtained by Martini et al [28] [29] for the same flow problem.…”

“…After the verification of the modelling procedures and boundary conditions, the SST k-ω turbulence model based DES is employed for the simulations and the experimental measurements of Martini et al [21] [22] [28] [29] and Horbach et al [6] are used for validation. Two blowing ratios (M = 0.5, 1.1) are considered for this purpose.…”

“…At a moderate blowing ratio M = 0.8, it was found that the DES slightly over-predicts the film-cooling effectiveness after a non-dimensional stream wise location x/H > 8 (hereafter H denotes the slot height), whereas at a high blowing ratio M = 1.1 it under-predicts after x/H > 5. The same configuration has also been studied computationally by Martini et al [28] [29] who used DES with the Spalart-Allmaras (SA) turbulence model. It was found that DES-SA results significantly under-predicted filmcooling performance at all three test blowing ratios of 0.5 < M < 1.1, with a maximum discrepancy of approximately 10% between the predictions and the measurements.…”

Influence of Parameters on vibrations for Centrifugal Pump Based on the Modal Dynamics Method

“…al [4] and Byskov, R et.al [5] applied the large eddy simulation in the field of turbomachinery to solve more details of the flow field and restricted to low Reynolds numbers. In addition, the hybrid methods [6][7][8][9] like detached eddy simulation are used increasingly. Many researchers [10][11][12][13][14] studied the fault diagnoses of the centrifugal pump or rotational machinery.…”