Investigation on the Effect of Different Lands on Trailing Edge Slot Film Cooling

2018 ◽  
Vol 0 (0) ◽  
Author(s):  
Yang Xu ◽  
Hui-ren Zhu ◽  
Wei-jiang Xu ◽  
Jian-sheng Wei
Keyword(s):  
Nusselt Number ◽  
Film Cooling ◽  
Turbine Blades ◽  
Experimental Studies ◽  
Navier Stokes ◽  
Trailing Edge ◽  
Cooling Effectiveness ◽  
Wall Functions ◽  
Film Cooling Effectiveness ◽  
Slot Film Cooling

Abstract Trailing edge slot film cooling is a widely used method for protecting the trailing edge of turbine blades from hot gas impingement. The structures that separate the slots, known as “lands,” come in a variety of configurations. This paper presents the effects of the trailing edge with different lands on the film cooling performance. Experimental studies are conducted on the film cooling effectiveness and Nusselt number with different lands. Four trailing edge configurations, including the straight lands, the beveling lands, the fillet lands and the tapered lands are considered under four blowing ratios (0.5, 0.7, 1.0 and 1.5). The Reynolds numbers of mainstream is fixed as 375,000. Film cooling effectiveness and Nusselt number performances are measured by transient liquid crystal measurement technique. Reynolds-averaged Navier-Stokes (RANS) simulation with realizable k-ε turbulence model and enhanced wall functions are performed using a commercial code Fluent. In each case, the slot height is kept constant. It is shown that the beveling lands, the fillet lands and the tapered lands have higher cooling effectiveness and lower Nusselt number compared with the straight lands. Under higher blowing ratios, the trailing edges of all four lands have higher cooling effectiveness and higher Nusselt number.

Application of Unsteady CFD Methods to Trailing Edge Cutback Film Cooling

2014 ◽  
Author(s):  
S. Ravelli ◽  
G. Barigozzi
Keyword(s):  
Film Cooling ◽  
Guide Vane ◽  
Navier Stokes ◽  
Trailing Edge ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Nozzle Guide Vane ◽  
Unsteady Rans ◽  
Exit Mach Number ◽  
Nozzle Guide

The main purpose of this numerical investigation is to overcome the limitations of the steady modeling in predicting the cooling efficiency over the cutback surface in a high pressure turbine nozzle guide vane. Since discrepancy between Reynolds-averaged Navier–Stokes (RANS) predictions and measured thermal coverage at the trailing edge was attributable to unsteadiness, Unsteady RANS (URANS) modeling was implemented to evaluate improvements in simulating the mixing between the mainstream and the coolant exiting the cutback slot. With the aim of reducing the computation effort, only a portion of the airfoil along the span was simulated at an exit Mach number of Ma2is = 0.2. Three values of the coolant-to-mainstream mass flow ratio were considered: MFR = 0.66%, 1.05%, and 1.44%. Nevertheless the inherent vortex shedding from the cutback lip was somehow captured by the URANS method, the computed mixing was not enough to reproduce the measured drop in adiabatic effectiveness η along the streamwise direction, over the cutback surface. So modeling was taken a step further by using the Scale Adaptive Simulation (SAS) method at MFR = 1.05%. Results from the SAS approach were found to have potential to mimic the experimental measurements. Vortices shedding from the cutback lip were well predicted in shape and magnitude, but with a lower frequency, as compared to PIV data and flow visualizations. Moreover, the simulated reduction in film cooling effectiveness toward the trailing edge was similar to that observed experimentally.

Trailing Edge Film Cooling of Gas Turbine Airfoils: External Cooling Performance of Various Internal Pin Fin Configurations

2010 ◽  
Author(s):  
T. Horbach ◽  
A. Schulz ◽  
H.-J. Bauer
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Turbine Blades ◽  
Back Surface ◽  
Trailing Edge ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Major Interest ◽  
Pin Fins ◽  
Discharge Behavior

The present paper describes an experimental study on trailing edge film cooling of modern high-pressure turbine blades using coolant ejection through planar slots on a pressure side cutback. The experimental test section consists of a generic scaled-up trailing edge model in an atmospheric open loop wind tunnel, which has been used in earlier studies by Martini et al. (e.g. [1]). An infrared thermographic measurement technique is employed, which allows for the application of engine-realistic density ratios around 1.6 by increasing the main flow temperature. The effects of different geometric configurations on the structure and performance of the cooling film are investigated in terms of film cooling effectiveness, heat transfer, and discharge behavior. Among other issues, the interaction between internal turbulators, namely an array of pin fins, with the ejection slot lip is of major interest. Therefore, different designs of the coolant ejection lip are studied. Four different ratios of lip thickness to ejection slot height (t/H = 0.2, 0.5, 1.0, 1.5) are investigated as well as three different lip profiles representing typical manufacturing imperfections and wear. Other geometric variations comprise elliptic pin fins with spanwise and streamwise orientation and the application of land extensions from the internal coolant cavity onto the cut-back surface. The blowing ratio is varied between 0.2 < M < 1.25. In terms of film cooling effectiveness the results show a strong dependency on ejection lip thickness and minor improvements are obtained with a rounded ejection lip profile. Significant improvements are achieved using land extensions. The elliptic pin fins have a strong effect on discharge behavior as well as on film cooling effectiveness and heat transfer. Except for the elliptic pin fins, the geometric variations have only a minor influence on heat transfer.

Parametric Study on Anti-Vortex Film Cooling Hole Arrangements

2014 ◽  
Vol 660 ◽  
pp. 664-668
Author(s):  
Kamil Abdullah ◽  
Hazim Fadli Aminnuddin ◽  
Akmal Nizam Mohammed
Keyword(s):  
Film Cooling ◽  
Thermal Protection ◽  
Turbine Blades ◽  
Vortex Pair ◽  
Navier Stokes ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Lateral Film ◽  
Lift Off

Film cooling has been extensively used to provide thermal protection for the external surface of the gas turbine blades. Numerous number of film cooling holes designs and arrangements have been introduced. The main motivation of these designs and arrangements are to reduce the lift-off effect cause by the counter rotating vortices (CRVP) produce by cylindrical cooling hole. One of the efforts is the introduction of newly found anti-vortex film cooling design. The present study focuses on anti-vortex holes arrangement consists of a main hole and pair of smaller holes. All three holes share a common inlet with the outlet of the smaller holes varies base on it relative position towards the main hole. Three anti-vortex holes arrangements have been considered; downstream anti-vortex hole arrangement (DAV), lateral anti-vortex hole arrangement (LAV), and upstream anti-vortex hole arrangement (UAV). In addition, a single hole (SH) film cooling has also been considered as the baseline. The investigation make used of ANSYS CFX software ver. 14. The investigations are made through Reynolds Average Navier Stokes analyses with the application of shear k-ε turbulence model. The results show that the anti-vortex designs produce significant improvement in term of film cooling effectiveness and distribution. The LAV arrangement shows the best film cooling effectiveness distribution among all considered cases and is consistent for all blowing ratios (BR). The results also unveil the formation of new vortex pair on both side of the primary hole CRVP. Interaction between the new vortices and the main CRVP structure reduce the lift off explaining the increased lateral film effectiveness.

Three-Dimensional Velocity and Scalar Field Measurements of an Airfoil Trailing Edge With Slot Film Cooling: The Effect of an Internal Structure in the Slot

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Julia Ling ◽  
Sayuri D. Yapa ◽  
Michael J. Benson ◽  
Christopher J. Elkins ◽  
John K. Eaton
Keyword(s):  
Film Cooling ◽  
Three Dimensional ◽  
Field Measurements ◽  
Resonance Imaging ◽  
Trailing Edge ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Horseshoe Vortices ◽  
Edge Span ◽  
Slot Film Cooling

Measurements of the 3D velocity and concentration fields were obtained using magnetic resonance imaging for a pressure-side cutback film cooling experiment. The cutback geometry consisted of rectangular slots separated by straight lands; inside each of the slots was an airfoil-shaped blockage. The results from this trailing edge configuration, the “island airfoil,” are compared to the results obtained with the “generic airfoil,” a geometry with narrower slots, wider, tapered lands, and no blockages. The objective was to determine how the narrower lands and internal blockages affected the average film cooling effectiveness and the spanwise uniformity. Velocimetry data revealed that strong horseshoe vortices formed around the blockages in the slots, which resulted in greater coolant nonuniformity on the airfoil breakout surface and in the wake. The thinner lands of the island airfoil allowed the coolant to cover a larger fraction of the trailing edge span, giving a much higher spanwise-averaged surface effectiveness, especially near the slot exit where the generic airfoil lands are widest.

3D Velocity and Scalar Field Measurements of an Airfoil Trailing Edge With Slot Film Cooling: The Effect of an Internal Structure in the Slot

2012 ◽  
Author(s):  
Julia Ling ◽  
Sayuri D. Yapa ◽  
Michael J. Benson ◽  
Christopher J. Elkins ◽  
John K. Eaton
Keyword(s):  
Film Cooling ◽  
Field Measurements ◽  
Pressure Side ◽  
Resonance Imaging ◽  
Trailing Edge ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Horseshoe Vortices ◽  
Edge Span ◽  
Slot Film Cooling

Measurements of the 3D velocity and concentration fields were obtained using magnetic resonance imaging for a pressure side cutback film cooling experiment. The cutback geometry consisted of rectangular slots separated by straight lands; inside each of the slots was an airfoil-shaped blockage. The results from this trailing edge configuration, the “island airfoil,” are compared to the results obtained with the “generic airfoil,” a geometry with narrower slots, wider, tapered lands, and no blockages. The objective was to determine how the narrower lands and internal blockages affected the average film cooling effectiveness and the spanwise uniformity. Velocimetry data revealed that strong horseshoe vortices formed around the blockages in the slots, which resulted in greater coolant non-uniformity on the airfoil breakout surface and in the wake. The thinner lands of the island airfoil allowed the coolant to cover a larger fraction of the trailing edge span, giving a much higher spanwise-averaged surface effectiveness, especially near the slot exit where the generic airfoil lands are widest.

Experimental and Numerical Study on the Effect of Fan-Shaped Hole Configuration on Film Cooling Effectiveness

2019 ◽  
Author(s):  
Hyun Jae Seo ◽  
Sang Hyeon Park ◽  
Jae Su Kwak ◽  
Young Seok Kang
Keyword(s):  
Film Cooling ◽  
Numerical Study ◽  
Turbine Blades ◽  
Experimental Studies ◽  
Shape Parameters ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Hole Shape ◽  
Expansion Angle ◽  
Shaped Hole

Abstract Film cooling technique has been widely applied to protect gas turbine blades from high temperature combustion gases. In this study, to improve the cooling effectiveness of fan-shaped film cooling holes, the effect of the main shape parameters on the film cooling effectiveness was investigated through numerical and experimental studies. Commercial software based on Reynolds Averaged Navier-Stokes (RANS) analysis was used in the numerical study, and the PSP (Pressure Sensitive Paint) technique was used to experimentally measure the film cooling effectiveness. The design points for the optimization were derived by the Box-Behnken method, which is one of the design of experiments (DOE). Three shape parameters of a fan-shaped hole were selected as design variables: the forward expansion angle, the lateral expansion angle, and the length of cylindrical part of the hole. The area-averaged film cooling effectiveness was selected as an objective function and the optimal hole shape of each analysis was obtained using the response surface methodology (RSM). It was confirmed that the film cooling effectiveness was affected by all three variables in both numerical and experimental results. Both analyses showed similar trends of each variable on film cooling effectiveness, but the optimal hole shape obtained by each method was different. The difference is attributed to flow separation not captured by RANS based analysis and surface roughness caused by the manufacturing process and the PSP coating in experimental analysis. Notably, the experimentally optimized hole showed better film cooling effectiveness than that of the numerically optimized hole in the comparison experiments.

Trailing Edge Film Cooling of Gas Turbine Airfoils—External Cooling Performance of Various Internal Pin Fin Configurations

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
T. Horbach ◽  
A. Schulz ◽  
H.-J. Bauer
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Turbine Blades ◽  
Open Loop ◽  
Trailing Edge ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Major Interest ◽  
Pin Fins ◽  
Discharge Behavior

The present paper describes an experimental study on trailing edge film cooling of modern high pressure turbine blades using coolant ejection through planar slots on a pressure side cutback. The experimental test section consists of a generic scaled-up trailing edge model in an atmospheric open loop wind tunnel, which has been used in several earlier studies. An infrared thermographic measurement technique is employed, which allows for the application of engine-realistic density ratios around 1.6 by increasing the main flow temperature. The effects of different geometric configurations on the structure and performance of the cooling film are investigated in terms of film cooling effectiveness, heat transfer, and discharge behavior. Among other issues, the interaction of internal turbulators, namely, an array of pin fins, with the ejection slot lip is of major interest. Therefore, different designs of the coolant ejection lip are studied. Four different ratios of lip thickness to ejection slot height (t/H=0.2,0.5,1.0,1.5), as well as three different lip profiles representing typical manufacturing imperfections and wear, are investigated. Other geometric variations comprise elliptic pin fins with spanwise and streamwise orientations and the application of land extensions from the internal coolant cavity onto the cutback surface. The blowing ratio is varied at 0.2<M<1.25. In terms of film cooling effectiveness, the results show a strong dependency on ejection lip thickness, and minor improvements are obtained with a rounded ejection lip profile. Significant improvements are achieved using land extensions. The elliptic pin fins have a strong effect on discharge behavior as well as on film cooling effectiveness and heat transfer. Except for the elliptic pin fins, the geometric variations have only a minor influence on heat transfer.

Numerical Predictions of Three-Dimensional Unsteady Turbulent Film-Cooling for Trailing Edge of Gas-Turbine Blade Using Large Eddy Simulation

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Ahmed Khalil ◽  
Hatem Kayed ◽  
Abdallah Hanafi ◽  
Medhat Nemitallah ◽  
Mohamed Habib
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Trailing Edge ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Gas Turbine Blades ◽  
Blowing Ratio ◽  
Eddy Simulation

This work investigates the performance of film-cooling on trailing edge of gas turbine blades using unsteady three-dimensional numerical model adopting large eddy simulation (LES) turbulence scheme in a low Mach number flow regime. This study is concerned with the scaling parameters affecting effectiveness and heat transfer performance on the trailing edge, as a critical design parameter, of gas turbine blades. Simulations were performed using ANSYS-fluentworkbench 17.2. High quality mesh was adapted, whereas the size of cells adjacent to the wall was optimized carefully to sufficiently resolve the boundary layer to obtain insight predictions of the film-cooling effectiveness on a flat plate downstream the slot opening. Blowing ratio, density ratio, Reynolds number, and the turbulence intensity of the mainstream and coolant flow are optimally examined against the film-cooling effectiveness. The predicted results showed a great agreement when compared with the experiments. The results show a distinctive behavior of the cooling effectiveness with blowing ratio variation as it has a dip in vicinity of unity which is explained by the behavior of the vortex entrainment and momentum of coolant flow. The negative effect of the turbulence intensity on the cooling effectiveness is demonstrated as well.

Application of Unsteady Computational Fluid Dynamics Methods to Trailing Edge Cutback Film Cooling

2014 ◽  
Vol 136 (12) ◽  
Author(s):  
Silvia Ravelli ◽  
Giovanna Barigozzi
Keyword(s):  
Film Cooling ◽  
Guide Vane ◽  
Navier Stokes ◽  
Trailing Edge ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Image Velocimetry ◽  
Unsteady Rans ◽  
Exit Mach Number ◽  
Nozzle Guide

The main purpose of this numerical investigation is to overcome the limitations of the steady modeling in predicting the cooling efficiency over the cutback surface in a high pressure turbine nozzle guide vane. Since discrepancy between Reynolds-averaged Navier–Stokes (RANS) predictions and measured thermal coverage at the trailing edge was attributable to unsteadiness, Unsteady RANS (URANS) modeling was implemented to evaluate improvements in simulating the mixing between the mainstream and the coolant exiting the cutback slot. With the aim of reducing the computation effort, only a portion of the airfoil along the span was simulated at an exit Mach number of Ma2is = 0.2. Three values of the coolant-to-mainstream mass flow ratio were considered: MFR = 0.66%, 1.05%, and 1.44%. Nevertheless the inherent vortex shedding from the cutback lip was somehow captured by the URANS method, the computed mixing was not enough to reproduce the measured drop in adiabatic effectiveness η along the streamwise direction, over the cutback surface. So modeling was taken a step further by using the scale adaptive simulation (SAS) method at MFR = 1.05%. Results from the SAS approach were found to have potential to mimic the experimental measurements. Vortices shedding from the cutback lip were well predicted in shape and magnitude, but with a lower frequency, as compared to particle image velocimetry (PIV) data and flow visualizations. Moreover, the simulated reduction in film cooling effectiveness toward the trailing edge was similar to that observed experimentally.

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