Film Cooling Modeling of Turbine Blades Using Algebraic Anisotropic Turbulence Models

2014 ◽  
Vol 136 (11) ◽  
Author(s):  
Xueying Li ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Film Cooling ◽  
Turbine Blades ◽  
Turbulence Models ◽  
Leading Edge ◽  
Good Prediction ◽  
Anisotropic Model ◽  
Scalar Flux ◽  
Film Cooling Effectiveness ◽  
Anisotropic Turbulence ◽  
Density Ratios

The complex structures in the flow field of gas turbine film cooling increase the anisotropy of turbulence making it difficult to accurately compute turbulent eddy viscosity and scalar diffusivity. An algebraic anisotropic turbulence model is developed while aiming at a more accurate modeling of the Reynolds stress and turbulent scalar-flux. In this study, the algebraic anisotropic model is validated by two in-house experiments. One is a leading edge with showerhead film cooling and the other is a vane with full coverage film cooling. Adiabatic film cooling effectiveness under different blowing ratios, density ratios, and film cooling arrangements were measured using pressure sensitive paint (PSP) technique. Four different turbulence models are tested and detailed analyses of computational simulations are performed. Among all the turbulence models investigated, the algebraic anisotropic model shows better agreement with the experimental data qualitatively and quantitatively. The algebraic anisotropic model gives a good prediction of the vortex strength and turbulence mixing of the jet, therefore improves the prediction of the scalar field.

Film Cooling Modeling of Turbine Blades Using Algebraic Anisotropic Turbulence Models

2014 ◽  
Author(s):  
Xueying Li ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Film Cooling ◽  
Turbine Blades ◽  
Turbulence Models ◽  
Leading Edge ◽  
Good Prediction ◽  
Anisotropic Model ◽  
Scalar Flux ◽  
Film Cooling Effectiveness ◽  
Anisotropic Turbulence ◽  
Density Ratios

The complex structures in the flow field of gas turbine film cooling increase the anisotropy of turbulence making it difficult to accurately compute turbulent eddy viscosity and scalar diffusivity. An algebraic anisotropic turbulence model is developed while aiming at a more accurate modeling of the Reynolds stress and turbulent scalar flux. In this study the algebraic anisotropic model is validated by two in-house experiments. One is a leading edge with showerhead film cooling and the other is a vane with full coverage film cooling. Adiabatic film cooling effectiveness under different blowing ratios, density ratios and film cooling arrangements were measured using PSP technique. Four different turbulence models are tested and detailed analyses of computational simulations are performed. Among all the turbulence models investigated, the algebraic anisotropic model shows better agreement with the experimental data qualitatively and quantitatively. The algebraic anisotropic model gives a good prediction of the vortex strength and turbulence mixing of the jet, therefore improves the prediction of the scalar field.

Algebraic Anisotropic Turbulence Modeling of Compound Angled Film Cooling Validated by PIV and PSP Measurements

2013 ◽  
Author(s):  
Xueying Li ◽  
Yanmin Qin ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Flow Field ◽  
Reynolds Stress ◽  
Film Cooling ◽  
Eddy Viscosity ◽  
Turbulence Modeling ◽  
Good Prediction ◽  
Anisotropic Model ◽  
Scalar Flux ◽  
Film Cooling Effectiveness ◽  
Anisotropic Turbulence

The complex structures in the flow field of gas turbine film cooling lead to the anisotropic property of the turbulent eddy viscosity and scalar diffusivity. An algebraic anisotropic turbulence model is developed while aiming at a more accurate modeling of the Reynolds stress and turbulent scalar flux. In this study the algebraic anisotropic model is validated by a series of in-house experiments for cylindrical film cooling with compound angle injection of 0, 45, and 90 deg. Adiabatic film cooling effectiveness and flow field are measured using PSP and PIV techniques on film cooling test rig in Tsinghua University. Detailed analyses of computational simulations are performed. The algebraic anisotropic model gives a good prediction of the secondary vortices associated with the jet and the trajectory of the jet, therefore improves the prediction of the scalar field. On one hand, the anisotropic eddy viscosity improves the modeling of Reynolds stress and the predictive flow field. On the other hand, the anisotropic turbulent scalar-flux model includes the role of anisotropic eddy viscosity in modeling of scalar flux and directly improves the turbulent scalar flux prediction.

Numerical Analysis on the Leading Edge Film Cooling of Bifurcation Holes for Gas Turbine Blade

2021 ◽  
Author(s):  
Zhonghao Tang ◽  
Gongnan Xie ◽  
Honglin Li ◽  
Wenjing Gao ◽  
Chunlong Tan ◽  
...  
Keyword(s):  
Turbine Blade ◽  
Film Cooling ◽  
Turbulence Models ◽  
Leading Edge ◽  
Spanwise Direction ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Cylindrical Holes ◽  
Lift Off

Abstract Film cooling performance of the cylindrical film holes and the bifurcated film holes on the leading edge model of the turbine blade are investigated in this paper. The suitability of different turbulence models to predict local and average film cooling effectiveness is validated by comparing with available experimental results. Three rows of holes are arranged in a semi-cylindrical model to simulate the leading edge of the turbine blade. Four different film cooling structures (including a cylindrical film holes and other three different bifurcated film holes) and four different blowing ratios are studied in detail. The results show that the film jets lift off gradually in the leading edge area as the blowing ratio increases. And the trajectory of the film jets gradually deviate from the mainstream direction to the spanwise direction. The cylindrical film holes and vertical bifurcated film holes have better film cooling effectiveness at low blowing ratio while the other two transverse bifurcated film holes have better film cooling effectiveness at high blowing ratio. And the film cooling effectiveness of the transverse bifurcated film holes increase with the increasing the blowing ratio. Additionally, the advantage of transverse bifurcated holes in film cooling effectiveness is more obvious in the downstream region relative to the cylindrical holes. The Area-Average film cooling effectiveness of transverse bifurcated film holes is 38% higher than that of cylindrical holes when blowing ratio is 2.

Experimental Study of Leakage Flow on Flow Field and Film Cooling of High Pressure Turbine Blade Platform

2015 ◽  
Author(s):  
Kenichiro Takeishi ◽  
Yutaka Oda ◽  
Shintaro Kozono
Keyword(s):  
High Pressure ◽  
Film Cooling ◽  
Turbine Blades ◽  
Leading Edge ◽  
Horseshoe Vortex ◽  
Temperature Fields ◽  
Leakage Flow ◽  
High Pressure Turbine ◽  
Film Cooling Effectiveness ◽  
Injection Angle

An experiment has been conducted to study stator/rotor disc cavity leakage flow on the platform of a highly loaded stationary linear blade cascade. The linear cascade consists of a scaled-up model of the high-pressure turbine blades of an E3 (Energy efficient engine) and leakage slot models installed under the platform. Experiments have been conducted to investigate the effect of the slot injection angle, leakage flow rates, distance between the leading edge of the blade and the slot, and spacing of the blades. The film-cooling effectiveness was measured by pressure sensitive paint (PSP), and the temperature fields and flow fields were investigated using laser-induced fluorescence (LIF) and particle image velocimetry (PIV), respectively. It was observed from the experiments that the leakage flow covered the surface of the blade platform when the distance between the leading edge and the slot was zero; however, with increasing distance, the horseshoe vortex dominates near the junction of the blade leading edge, and the leakage flow could not cover the region. It was also found that the leakage flow has an effect that promotes the formation of the horseshoe vortex for some experimental conditions.

Assessment of URANS and DES for Prediction of Leading Edge Film Cooling

2011 ◽  
Vol 134 (3) ◽  
Author(s):  
Toshihiko Takahashi ◽  
Ken-ichi Funazaki ◽  
Hamidon Bin Salleh ◽  
Eiji Sakai ◽  
Kazunori Watanabe
Keyword(s):  
Turbulence Model ◽  
Film Cooling ◽  
Turbulence Modeling ◽  
Turbine Blades ◽  
Leading Edge ◽  
Vortex Structures ◽  
Temperature Fields ◽  
Detached Eddy Simulation ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness

This paper describes the assessment of CFD simulations for the film cooling on the blade leading edge with circular cooling holes in order to contribute durability assessment of the turbine blades. Unsteady RANS applying a k-ε-v2-f turbulence model and the Spalart and Allmaras turbulence model and detached-eddy simulation (DES) based on the Spalart and Allmaras turbulence model are addressed to solve thermal convection. The CFD calculations were conducted by simulating a semicircular model in the wind tunnel experiments. The DES and also the k-ε-v2-f model evaluate explicitly the unsteady fluctuation of local temperature by the vortex structures, so that the predicted film cooling effectiveness is comparatively in agreement with the measurements. On the other hand, the predicted temperature fields by the Spalart and Allmaras model are less diffusive than the DES and the k-ε-v2-f model. In the present turbulence modeling, the DES only predicts the penetration of main flow into the film cooling hole but the Spalart and Allmaras model is not able to evaluate the unsteadiness and the vortex structures clearly, and overpredict film cooling effectiveness on the partial surface.

Evaluation of Two-Equation Models of Turbulence in Predicting Film Cooling Performance Under High Free Stream Turbulence

2007 ◽  
Author(s):  
Savas Yavuzkurt ◽  
Jawad S. Hassan
Keyword(s):  
Film Cooling ◽  
Free Stream ◽  
Turbulence Models ◽  
Accurate Solution ◽  
Diameter Ratio ◽  
Tube Length ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Free Stream Turbulence ◽  
Density Ratios

The capabilities of four two-equation turbulence models in predicting film cooling effectiveness under high free stream turbulence (FST) intensity (Tu = 10%) were investigated and their performance are presented and discussed. The four turbulence models are: the standard k-ε, RNG, and realizable k-ε models as well as the standard k-ω model all four found in the FLUENT CFD code. In all models, the enhanced wall treatment has been used to resolve the flow near solid boundaries. A systematic approach has been followed in the computational setup to insure grid-independence and accurate solution that reflects the true capabilities of these models. Exact geometrical and flow-field replicas of an experimental study on discrete hole film cooling were generated and used in FLUENT. A pitch-to-diameter ratio of 3.04, injection tube length-to-diameter ratio of 4.6 and density ratios of 0.92 and 0.97 were some of the parameters used in the film cooling analysis. The study covered two levels of blowing ratios (M = 0.5 and 1.5) at an environment of what is defined as high initial free-stream turbulence intensity (Tu = 10%). Performance of these models under a very low initial FST were presented in a paper by the authors in Turbo Expo 2006. In that case, the standard k-ε model had the most consistent performance among all considered turbulence models and the best centerline film cooling effectiveness predictions under very low FST. However, after the addition of high FST in the free-stream, even the standard k-ε model started to deviate greatly from the experimental data (up to 200% over-prediction) under high blowing ratios (M = 1.5). The model which performed the best under high FST but low blowing ratios (M = 0.5) is still the standard k-ε model. In all cases only standard k-ε model results match the trends of data for both cases. It can be said that under high FST with high M all the models do not do a good job of predicting the data. It was concluded that these deviations resulted from the effects of both high FST and high M. Under high M, near the injection holes deviations could result from the limitations of Boussinesq hypothesis relating the direction of Reynolds stress to the mean strain rate. Also, it seems like all models have trouble including the effects of high FST by not being able to take into account high levels of diffusion of turbulence from the free stream. However, standard k-ε model still looks like the best candidate for further improvement with the addition of new diffusion model for TKE under high FST.

Effect of Internal Crossflow Velocity on Film Cooling Effectiveness—Part I: Axial Shaped Holes

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
John W. McClintic ◽  
Joshua B. Anderson ◽  
David G. Bogard ◽  
Thomas E. Dyson ◽  
Zachary D. Webster
Keyword(s):  
Film Cooling ◽  
Velocity Ratio ◽  
Turbine Blades ◽  
Lateral Spreading ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Crossflow Velocity ◽  
Density Ratios ◽  
Film Cooling Holes ◽  
Injection Rates

The effect of feeding shaped film cooling holes with an internal crossflow is not well understood. Previous studies have shown that internal crossflow reduces film cooling effectiveness from axial shaped holes, but little is known about the mechanisms governing this effect. It was recently shown that the crossflow-to-mainstream velocity ratio is important, but only a few of these crossflow velocity ratios have been studied. This effect is of concern because gas turbine blades typically feature internal passages that feed film cooling holes in this manner. In this study, film cooling effectiveness was measured for a single row of axial shaped cooling holes fed by an internal crossflow with crossflow-to-mainstream velocity ratio varying from 0.2 to 0.6 and jet-to-mainstream velocity ratios varying from 0.3 to 1.7. Experiments were conducted in a low speed flat plate facility at coolant-to-mainstream density ratios of 1.2 and 1.8. It was found that film cooling effectiveness was highly sensitive to crossflow velocity at higher injection rates while it was much less sensitive at lower injection rates. Analysis of the jet shape and lateral spreading found that certain jet characteristic parameters scale well with the crossflow-to-coolant jet velocity ratio, demonstrating that the crossflow effect is governed by how coolant enters the film cooling holes.

Experimental Study of Oscillating Freestream Effect on the Spatiotemporal Distributions of Leading-Edge Film Cooling

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Hongyi Shao ◽  
Mohamed Qenawy ◽  
Tianlun Zhang ◽  
Di Peng ◽  
Yingzheng Liu ◽  
...  
Keyword(s):  
Experimental Study ◽  
Strouhal Number ◽  
Film Cooling ◽  
Turbine Blades ◽  
Leading Edge ◽  
Fast Response ◽  
Frame Rate ◽  
Cooling Effectiveness ◽  
Oscillation Effect ◽  
Film Cooling Effectiveness

Abstract An experimental study was conducted to investigate the influence of mainstream oscillations on spatio-temporal variation of leading-edge film cooling effectiveness. The investigation utilized fast-response pressure-sensitive paint (Fast-PSP) technique at high frame rate. During the experiment, coolant (i.e., CO2, DR = 1.53) was discharged into three rows of cylindrical holes. Various blowing ratios (i.e., M = 0.50, 0.75, 1.00, and 1.50) were tested under the steady (i.e., f = 0 Hz) and oscillating (i.e., f = 7 Hz and 25 Hz) conditions. The measured instantaneous effectiveness was analyzed in terms of time-averaged and phase-averaged results. The results revealed that the mainstream oscillation, consisting of simultaneous pressure and velocity oscillation, significantly influences the behavior of the film cooling effectiveness. The time-averaged effectiveness significantly decreased at high oscillating frequency (i.e., 13.0–19.8% reduction at M = 0.50, f = 25 Hz compared with f = 0 Hz), especially at low blowing ratios (i.e., M = 0.50 and 0.75). The phase-averaged results captured significant decay in the film distributions associated with backflow caused by negative pressure gradients in coolant holes at certain phases. However, the mainstream oscillation effect was relatively insignificant at high blowing ratios (i.e., M = 1.00 and 1.50), which revealed the robustness of coolant coverage at low coolant Strouhal number (i.e., high blowing ratio) under the same oscillating frequency. Furthermore, the unsteady coolant intermittency showed highly unstable film coverage at high coolant Strouhal number. The coolant decay associated with backflow at high coolant Strouhal number should be considered by the gas-turbine designers in order to improve the lifecycle of turbine blades.

The Influence of Turbulence and Reynolds Number on Slot Film Cooling Over the Downstream Pressure Surface

2019 ◽  
Author(s):  
L. W. Soma ◽  
F. E. Ames ◽  
S. Acharya
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Thermal Stresses ◽  
Surface Film ◽  
Leading Edge ◽  
Internal Cooling ◽  
Film Cooling Effectiveness ◽  
Pressure Surface ◽  
Density Ratios ◽  
Slot Film Cooling

Abstract Pressure surface film cooling from discrete holes can often be challenging due to higher than optimum coolant to surface pressure ratios, effects of high levels of flow field turbulence, and the potential for clogging. Double wall cooling methods can be designed to collect spent cooling air and distribute the film cooling downstream through a slot. Incremental impingement is a new internal cooling method designed for cooling the leading edge region and pressure surface. Internally, incremental impingement includes high solidity pedestals to conduct heat and transmit thermal stresses due to temperature variations between cold and hot side surfaces. Subsequently, the flow is collected downstream from the last row of pedestals and discharged through a slot. Experimental and computational research from mesh slots, which have dense arrays of pedestals upstream from the discharge, and slots downstream from high solidity pedestal arrays have shown that turbulence and vorticity generated inside a film cooling plenum can have a significant impact on downstream film cooling. This impact of plenum flow disturbances is in addition to the film cooling dissipation caused by external flow field turbulence. Incremental impingement, in addition to high solidity pedestals, has impingement jets integrated behind the last row of pedestals which may cause further disruption to the film discharge and flow field interaction. The present measurements document the film cooling effectiveness distributions downstream from a slot located at 62% arc along the pressure surface of a vane. The plenum has been designed to include high solidity pedestals and impingement jets consistent with an incremental impingement geometry. Blowing ratios of 0.4, 0.7 and 1.0 have been investigated at vane exit chord Reynolds numbers of 500,000, 1,000,000 and 2,000,000 at density ratios a little over 1. These conditions have been run at 5 independent turbulence levels ranging from 0.7% to over 17%. The results provide a consistent picture of pressure surface slot film cooling downstream from incremental impingement.

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