Transition Modeling Effects on Turbine Rotor Blade Heat Transfer Predictions (original) (raw)
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Application of transition modelling in CFD for use with turbine blades
2011
The design of internally-cooled gas turbine blades requires accurate predictions of distributions of blade temperature values and temperature gradients. This requires accurate predictions of heat transfer distributions from the hot gas (on the blade external surfaces) and the coolant (on the blade internal cooling passage surfaces). Navier-Stokes solvers assume the flow to be either fully laminar or fully turbulent, and solve accordingly. The current validation test was designed to characterise the turbine blade external surface heat transfer predictive capability of a commercial RANS solver, which was augmented by a transition onset model, and compare the predictive accuracy with that of a boundary layer solver which also utilised a transition model. The validation case chosen was that of Consigny and Richards, in which blade Reynolds number, free stream turbulence degree, downstream Mach number and incidence angle were all varied independently. Four turbulence modelling options ha...
Transition modelling for the prediction of the heat transfer coefficient of a gas-turbine blade
Applied Energy, 1994
A BS TRA C T The presented procedure aims at selecting the best of nine well-known transition models to predict the heat-transfer coefficient of a blade when compared with some experimental data. For the suction surface, the Schlichting transition-start model gave the best prediction followed by that of Seyb. For the pressure surface, the transition-origin models predictions were considered but the concept of natural transition appears questionable.
Prediction of Turbine Blade Passage Heat Transfer Using a Zero and a Two-Equation Turbulence Model
Volume 4: Heat Transfer; Electric Power; Industrial and Cogeneration, 1994
Predictions of the heat transfer rates on the hot surfaces of a turbine cascade blade passage as influenced by the turbulence models was examined. A zero equation turbulence model supplemented by a bypass transition model and a two equation low Reynolds number model were chosen for this study. The experimental data of Graziani et. al. were used for comparison. The comparisons suggest that at least for the experimental data considered in this work the use of a two-equation model does not provide an overall more accurate solution than the zero equation model. This conclusion is strengthened if one takes into account the relative economy of computations with the algebraic model.
Computations of Heat Transfer in Transitional Turbine Flows
10th AIAA/ASME Joint Thermophysics and Heat Transfer Conference, 2010
A computational study of heat transfer in transitional flows in turbines is performed employing γ-Re Ѳ transition model. The model and the numerical approach have been previously validated against PAK-B blade cascade experiments under a wide range of Reynolds numbers and freestream turbulence intensities. This paper extends validation of γ-Re Ѳ transition model against detailed heat transfer measurements on a vane subjected to inlet turbulence generated by a mock combustion system configuration representative of recently developed catalytic and dry low NO x combustors. The experiments include six different inlet turbulence conditions and a range of Reynolds numbers. The results indicate that the model is able to predict transition onset and length accurately at low and medium levels of freestream turbulence. However at higher turbulence intensities and higher Re cases the discrepancies between experiments and computations were observed.
Numerical Simulation of Turbine Blade Heat Transfer Using Two-Equation Turbulence Models
2000
The development of high performance gas turbines requires high turbine inlet temperatures that can lead to severe thermal stresses in the turbine blades, particularly in the first stages of the turbine. Therefore, the major objective of gasturbine designers is to determine the thermal and aero-dynamical characteristics of the turbulent flow in the turbine cascade. This work is a numerical simulation of fluid flow and heat transfer in the turbine blade using different two-equation turbulence models. The turbulence models used here were based on the eddy viscosity concept, which determined the turbulent viscosity through time-averaged Navier-Stokes differential equations. The most widely accepted turbulence models are the two-equation models, which involves the solution of two transport equations for the turbulent kinetic energy, k, and its rate of dissipation, e or w. In the present simulation, four two-equation turbulence models were used, the standard k-e model, the modified Chen-K...
EPJ Web of Conferences, 2017
The contribution deals with the simulation of the transitional flows with heat transfer by means the EARSM turbulence model of Hellsten [1] completed by the algebraic transition model of Straka and PĜíhoda [2] and by the three-equation model of Walters and Cokjlat [3]. The both mathematical models were tested for the flat plate flow on a heated wall measured by Sohn and Reshotko [16] and then applied to the simulation of compressible flow through the VKI turbine blade cascade according to measurements of Arts et al. [4]. The simulations were carried out for subsonic and transonic regimes at various free-stream turbulence levels. The best agreement of numerical results with experimental data was achieved by the URANS approach applied for the EARSM model with the algebraic transition model giving good results for both subsonic and transonic regimes as well.
Effects of Rotation on Blade Surface Heat Transfer: An Experimental Investigation
Journal of Turbomachinery, 1998
Measurements of turbine blade surface heat transfer in a transient rotor facility are compared with predictions and equivalent cascade data. The rotating measurements involved both forward and reverse rotation (wake-free) experiments. The use of thin-film gages in the Oxford Rotor Facility provides both time-mean heat transfer levels and the unsteady time history. The time-mean level is not significantly affected by turbulence in the wake; this contrasts with the cascade response to free-stream turbulence and simulated wake passing. Heat transfer predictions show the extent to which such phenomena are successfully modeled by a time-steady code. The accurate prediction of transition is seen to be crucial if useful predictions are to be obtained.
Numerical Heat Transfer, Part A: Applications, 1997
A three-dimensional Navier-Stokes code has been used to compute the heat transfer coefficient on two film-cooled turbine blades, namely the VKI rotor with six rows of cooling holes including three rows on the shower head, and the C3X vane with nine rows of holes including five rows on the shower head. Predictions of heat transfer coefficient at the blade surface using three two-equation turbulence models, specifically, Coalcley's q-to model, Chien's k-e model and Wilcox's km model with Menter's modifications, have been compared with the experimental data of Camci and Arts (1990) for the VKI rotor, and of Hylton et al. (1988) for the C3X vane along with predictions using the Baldwin-Lomax (B-L) model taken from Garg and Gaugler (1995). It is found that for the cases considered here the two-equation models predict the blade heat transfer somewhat better than the B-L model except immediately downstream of the film-cooling holes on the suction surface of the VKI rotor, and over most of the suction surface of the C3X vane. However, all twoequation models require 40% more computer core than the B-L model for solution, and while the qco and k-e models need 40% more computer time than the B-L model, the k-co model requires at least 65% more time due to slower rate of convergence. It is found that the heat transfer coefficient exhibits a strong spanwise as well as streamwise variation for both blades and all turbulence models. NOMENCLATURE au sonic speed at T. c true chord of the blade d coolant hole diameter h heat transfer coefficient based on (T.-T.) ho standard value (= 1135.6 W/m2-K = 200 Btuftir-fe-R) k turbulence kinetic energy turbulence length scale m mass flow rate M Mach number pressure square root of turbulence kinetic energy coolant hole radius Re Reynolds number distance from the leading edge along the pressure or suction surface = s/s" on the suction surface, and =-s/s", on the pressure surface temperature Tu turbulence intensity shear velocity V, average coolant velocity at the hole exit y-coordinate of the Cartesian coordinate system with origin at the geometric stagnation point distance in wall coordinates (= yv ./v) z-coordinate along the span Kronecker delta Ay distance (from the wall) of the first point off the wall turbulence dissipation rate ratio of specific heats p viscosity kinematic viscosity p density to specific turbulence dissipation rate (= enc) Subscripts c for coolant (average value) in value at inlet m maximum value n corresponding to uncooled blade o stagnation value T turbulent value ,i derivative with respect to i-direction coordinate
Heat Transfer to Rotating Turbine Blades in a Flow Undisturbed by Wakes
Volume 4: Heat Transfer; Electric Power; Industrial and Cogeneration, 1994
The flow over the high pressure blades of a gas turbine is disturbed by wakes and shock waves from the nozzle guide vanes upstream. These disturbances lead to increased heat transfer to the blade surfaces, the accurate prediction of which is an essential stage in the design process. The Oxford Rotor experiment consists of a highly instrumented 0.5 m diameter shroudless turbine which is supplied with air from a piston tube during the 200 ms run time and simulates realistic engine Mach and Reynolds numbers. Previous experiments have measured blade surface pressures and heat transfer rates, and compared them with similar data from linear cascades. The present work is designed to enable the accuracy of rotation terms in computational fluid dynamics (CFD) calculations to be assessed, by providing heat transfer data from the rotating frame in the absence of wakes. Flow disturbances were avoided by removing the nozzle guide vanes, the correct angle of incidence onto the rotor blades being ...
Prediction of Unsteady Rotor-Surface Pressure and Heat Transfer From Wake Passings
Journal of Turbomachinery, 1992
The research described in this paper is a numerical investigation of the effects of unsteady flow on gas turbine heat transfer, particularly on a rotor blade surface. The unsteady flow in a rotor blade passage and the unsteady heat transfer on the blade surface as a result of wake/blade interaction are modeled by the inviscid flow/boundary layer approach. The Euler equations that govern the inviscid flow are solved using a time-accurate marching scheme. The unsteady flow in the blade passage is induced by periodically moving a wake model across the passage inlet. Unsteady flow solutions in the passage provide pressure gradients and boundary conditions for the boundary-layer equations that govern the viscous flow adjacent to the blade surface. Numerical solutions of the unsteady turbulent boundary layer yield surface heat flux values that can then be compared to experimental data. Comparisons with experimental data show that unsteady heat flux on the blade suction surface is well pre...