Overall Effectiveness of a Blade Endwall With Jet Impingement and Film Cooling

2013 ◽  
Vol 136 (3) ◽  
Author(s):  
Amy Mensch ◽  
Karen A. Thole
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Jet Impingement ◽  
Heat Transfer Analysis ◽  
Transfer Model ◽  
Convective Cooling ◽  
Impingement Cooling ◽  
Internal Impingement ◽  
The Impact ◽  
Overall Effectiveness

Ever-increasing thermal loads on gas turbine components require improved cooling schemes to extend component life. Engine designers often rely on multiple thermal protection techniques, including internal cooling and external film cooling. A conjugate heat transfer model for the endwall of a seven-blade cascade was developed to examine the impact of both convective cooling and solid conduction through the endwall. Appropriate parameters were scaled to ensure engine-relevant temperatures were reported. External film cooling and internal jet impingement cooling were tested separately and together for their combined effects. Experiments with only film cooling showed high effectiveness around film-cooling holes due to convective cooling within the holes. Internal impingement cooling provided more uniform effectiveness than film cooling, and impingement effectiveness improved markedly with increasing blowing ratio. Combining internal impingement and external film cooling produced overall effectiveness values as high as 0.4. A simplified, one-dimensional heat transfer analysis was used to develop a prediction of the combined overall effectiveness using results from impingement only and film cooling only cases. The analysis resulted in relatively good predictions, which served to reinforce the consistency of the experimental data.

Overall Effectiveness of a Blade Endwall With Jet Impingement and Film Cooling

2013 ◽  
Author(s):  
Amy Mensch ◽  
Karen A. Thole
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Jet Impingement ◽  
Heat Transfer Analysis ◽  
Transfer Model ◽  
Convective Cooling ◽  
Impingement Cooling ◽  
Internal Impingement ◽  
The Impact ◽  
Overall Effectiveness

Ever increasing thermal loads on gas turbine components require improved cooling schemes to extend component life. Engine designers often rely on multiple thermal protection techniques, including internal cooling and external film cooling. A conjugate heat transfer model for the endwall of a seven blade cascade was developed to examine the impact of both convective cooling and solid conduction through the endwall. Appropriate parameters were scaled to ensure engine relevant temperatures were reported. External film cooling and internal jet impingement cooling were tested separately and together for their combined effects. Experiments with only film cooling showed high effectiveness around film cooling holes due to convective cooling within the holes. Internal impingement cooling provided more uniform effectiveness than film cooling, and impingement effectiveness improved markedly with increasing blowing ratio. Combining internal impingement and external film cooling produced overall effectiveness values as high as 0.4. A simplified one-dimensional heat transfer analysis was used to develop a prediction of the combined overall effectiveness using results from impingement only and film cooling only cases. The analysis resulted in relatively good predictions, which served to reinforce the consistency of the experimental data.

Heat Transfer Analysis of Jet Impingement Cooling on a Simulated Ceramic Matrix Composite Surface

2017 ◽  
Author(s):  
Karthik Krishna ◽  
Mark Ricklick
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Matrix Composite ◽  
Ceramic Matrix Composite ◽  
Jet Impingement ◽  
Ceramic Matrix ◽  
Heat Transfer Analysis ◽  
Test Surface ◽  
Composite Surface ◽  
The Impact

Ceramic Matrix Composite is a woven material characterized by a significant level of surface waviness of 35–60μm and surface roughness of 5–6μm. To be implemented in a future gas turbine engine they will be cooled traditionally to increase power and efficiency. To analyze the CMC surface effects on heat transfer rate, an impinging circular jet on a simulated CMC surface is studied experimentally and the CMC surface is represented by a high resolution CNC machined surface. The test parameters are jet to plate distance of 7 jet diameters, oblique impingement angles of 45° and 90° and Reynolds numbers of 11,000 to 35,000. The test surface is broken down into constant temperature segments, and individual segment Nusselt number is determined and plotted for the various impingement cases studied. Area-Averaged results show negligible changes in average Nusselt number as compared to the hydrodynamically smooth surface. The impact of the CMC surface feature is negligible compared to the uncertainty in heat transfer coefficient, and therefore traditional design tools can be utilized.

Experimental Evaluations of the Relative Contributions to Overall Effectiveness in Turbine Blade Leading Edge Cooling

2018 ◽  
Author(s):  
Carol E. Bryant ◽  
Connor J. Wiese ◽  
James L. Rutledge ◽  
Marc D. Polanka
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Leading Edge ◽  
Internal Surface ◽  
Internal Cooling ◽  
Transfer Coefficients ◽  
Impingement Cooling ◽  
External Cooling ◽  
Turbine Component ◽  
Overall Effectiveness

Gas turbine hot gas path components are protected through a combination of internal cooling and external film cooling. The coolant typically travels through internal passageways, which may involve impingement on the internal surface of a turbine component, before being ejected as film cooling. Internal cooling effects have been studied in facilities that allow measurement of heat transfer coefficients within models of the internal cooling paths, with large heat transfer coefficients generally desirable. External film cooling is typically evaluated through measurements of the adiabatic effectiveness and its effect on the external heat transfer coefficient. Efforts aimed at improving cooling are often focused on either only the internal cooling or the film cooling; however, the common coolant flow means the internal and external cooling schemes are linked and the coolant holes themselves provide another convective path for heat transfer to the coolant. Recently, measurements of overall cooling effectiveness using matched Biot number turbine component models allow evaluation of the nondimensional wall temperature achieved for the fully cooled component. However, the relative contributions of internal cooling, external cooling, and convection within the film cooling holes is not well understood. Large scale, matched Biot number experiments, complemented by CFD simulations, were performed on a fully film cooled cylindrical leading edge model to evaluate the effects of various alterations in the cooling design on the overall effectiveness. The relative influence of film cooling and cooling within the holes was evaluated by selectively disabling individual holes and quantifying how the overall effectiveness changed. Several internal impingement cooling schemes in addition to a baseline case without impingement cooling were also tested. In general, impingement cooling is shown to have a negligible influence on the overall effectiveness in the showerhead region. This indicates that the cost and pressure drop penalties for implementing impingement cooling may not be compensated by an increase in thermal performance. Instead, the internal cooling provided by convection within the holes themselves was shown, along with external film cooling, to be a dominant contribution to the overall cooling effectiveness. Indeed, the numerous holes within the showerhead region impede the ability of internal surface cooling schemes to influence the outside surface temperature. The results of this research may allow improved focus of future efforts on the forms of cooling with the greatest potential to improve cooling performance.

Overall Effectiveness and Flowfield Measurements for an Endwall With Nonaxisymmetric Contouring

2015 ◽  
Vol 138 (3) ◽  
Author(s):  
Amy Mensch ◽  
Karen A. Thole
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Transfer Model ◽  
Internal Cooling ◽  
Blowing Ratio ◽  
Passage Vortex ◽  
Endwall Contouring ◽  
Overall Effectiveness

Endwall contouring is a technique used to reduce the strength and development of three-dimensional secondary flows in a turbine vane or blade passage in a gas turbine. The secondary flows locally affect the external heat transfer, particularly on the endwall surface. The combination of external and internal convective heat transfer, along with solid conduction, determines component temperatures, which affect the service life of turbine components. A conjugate heat transfer model is used to measure the nondimensional external surface temperature, known as overall effectiveness, of an endwall with nonaxisymmetric contouring. The endwall cooling methods include internal impingement cooling and external film cooling. Measured values of overall effectiveness show that endwall contouring reduces the effectiveness of impingement alone, but increases the effectiveness of film cooling alone. Given the combined case of both impingement and film cooling, the laterally averaged overall effectiveness is not significantly changed between the flat and the contoured endwalls. Flowfield measurements indicate that the size and location of the passage vortex changes as film cooling is added and as the blowing ratio increases. Because endwall contouring can produce local effects on internal cooling and film cooling performance, the implications for heat transfer should be considered in endwall contour designs.

Numerical Analysis of Heat Transfer in a Leading Edge Geometry With Racetrack Holes and Film Cooling Extraction

2013 ◽  
Author(s):  
Luca Andrei ◽  
Antonio Andreini ◽  
Riccardo Da Soghe ◽  
Bruno Facchini ◽  
Stefano Zecchi
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Numerical Study ◽  
Internal Heat ◽  
Leading Edge ◽  
Jet Impingement ◽  
Internal Surface ◽  
Heat Transfer Process ◽  
University Of Florence ◽  
The Impact

A numerical study of a state of the art leading edge cooling scheme was performed to analyze the heat transfer process within the leading edge cavity of a high pressure turbine airfoil. The investigated geometries account a trapezoidal supply channel with a large racetrack impingement holes. The coolant jets, confined among two consequent large fins, impact the leading edge internal surface and it is extracted from the leading edge cavity through both showerhead holes and film cooling holes. The CFD setup has been validated by means of the experimental measurements performed on a dedicated test rig developed and operated at University of Florence. The aim of this study is to investigate the combined effects of jet impingement, mass flow extraction and fins presence on the internal heat transfer of the leading edge cavity. More in details, the paper analyses the impact, in terms of blade metal temperature, of large fins presence and positioning. Jet’s Reynolds number is varied in order to cover the typical engine conditions of these cooling systems (Rej = 20000 – 40000).

scholarly journals Conjugate Heat Transfer Analysis of Flat Plate Subjected to Impingement and Film Cooling

2021 ◽  
Vol 9 (9) ◽  
pp. 1667-1678
Author(s):  
Devaraj K
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Flat Plate ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Jet Impingement ◽  
Heat Transfer Analysis ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness

Abstract: The present computational study involves a flat plate subjected to combined effect of jet impingement and film cooling. A conjugate heat transfer model in conjunction with k-ω SST turbulence model is employed to study the turbulence effects. The effect of Reynolds number varying from 389 to 2140 on static temperature, Nusselt number and film cooling effectiveness has be discussed for the blowing ratios of 0.6, 0.8, 1.0. The variation in the size of vortices formed on the impinging surface with Reynolds number is studied. It has been observed that the local Nusselt number shows a rising trend with the increase in Reynolds number, while the static temperatures follow the downfall in its values. As a result, an enhancement in the effectiveness is observed, which is credited to the capabilities of combined impingement and film cooling. At Reynolds number of 972, the coolant jet is found to be attached to the surface, for this condition the heat transfer phenomena for blowing ratios of 0.6, 0.8, 1.0, 1.2, 1.6, 2.0, 2.4, 2.6 are studied to understand the flow distribution on the plate surface. Keywords: Jet impingement, film cooling, effectiveness, conjugate heat transfer

Heat Transfer Measurements of Vane Endwall With Film Cooling and Impingement Cooling

2015 ◽  
Author(s):  
Xueying Li ◽  
Mingfei Li ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Heat Transfer ◽  
Mass Flow ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Hot Spot ◽  
Transfer Characteristic ◽  
Temperature Sensitive ◽  
Film Cooling Effectiveness ◽  
Impingement Cooling ◽  
Overall Effectiveness

The switch from diffusive combustion to premixed combustion in a modern gas turbine will change the combustor exit temperature profile to a more uniform one. Hot spot may occur from 10% to 90% vane span. This will directly affect the cooling of the first stage vane especially the endwall region. Cooling characteristics and metal temperature prediction of endwall become critical. A typical endwall configuration with matched non-dimensional parameters to the engine condition was investigated experimentally in this study. Two endwall cooling arrangements at four different coolant to mainstream mass flow ratios (MFR) were tested in a linear cascade. Detailed measurements of aerodynamic, heat transfer coefficient, adiabatic film cooling effectiveness and overall effectiveness of the endwall were performed. The temperature sensitive paint (TSP) and pressure sensitive paint (PSP) were used to acquire these parameters. The conjugate heat transfer characteristic of endwall with film cooling and impingement cooling was discussed. Besides, the influence of coolant mass flow ratio on conjugate heat transfer of endwall was analyzed. The results suggested that for film only case the overall effectiveness increases with the increase of MFR but for the combination case with both film cooling and impingement cooling the growth slows down. 1D and 2D method for overall effectiveness prediction based on experimental data for separate parameters and correlations were also studied.

scholarly journals Experimental Studies on Heat Transfer Analysis of Mild Steel Using Jet Impingement Cooling Technique

2019 ◽  
Vol 7 (3) ◽  
pp. 1267-1272
Author(s):  
Mohammed Asif Kattimani, ◽  
Mohammad Abbas Khan ◽  
Mohd Ishaq ◽  
Mohammed Asad ◽  
Meer Salman Ali
Keyword(s):  
Heat Transfer ◽  
Mild Steel ◽  
Experimental Studies ◽  
Jet Impingement ◽  
Heat Transfer Analysis ◽  
Impingement Cooling ◽  
Cooling Technique

Experimental Investigation of Endwall Heat Transfer With Film and Impingement Cooling

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Xueying Li ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Heat Transfer ◽  
Mass Flow ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Transfer Characteristic ◽  
Temperature Sensitive ◽  
Film Cooling Effectiveness ◽  
Impingement Cooling ◽  
Temperature Sensitive Paint ◽  
Overall Effectiveness

The switch from diffusive combustion to premixed combustion in a modern gas turbine changes the combustor exit temperature profile to a more uniform one. This will directly affect the cooling of the first stage vane especially the endwall region. A typical endwall configuration with matched nondimensional parameters to the engine condition was investigated experimentally in this study. Two endwall cooling arrangements at four different coolant to mainstream mass flow ratios (MFR) were tested in a linear cascade. Detailed measurements of pressure distribution, heat transfer coefficient, adiabatic film cooling effectiveness, and overall effectiveness of the endwall were performed. The temperature-sensitive paint (TSP) and pressure-sensitive paint (PSP) were used to acquire these parameters. The conjugate heat transfer characteristic of endwall with film cooling and impingement cooling was discussed. Moreover, the influence of coolant mass flow rate on conjugate heat transfer of endwall was analyzed. One- and two-dimensional methods for overall effectiveness prediction based on experimental data for separate parameters and correlations were also studied.

Overall Effectiveness and Flowfield Measurements for an Endwall With Non-Axisymmetric Contouring

2015 ◽  
Author(s):  
Amy Mensch ◽  
Karen A. Thole
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Transfer Model ◽  
Internal Cooling ◽  
Blowing Ratio ◽  
Passage Vortex ◽  
Endwall Contouring ◽  
Overall Effectiveness

Endwall contouring is a technique used to reduce the strength and development of three-dimensional secondary flows in a turbine vane or blade passage in a gas turbine. The secondary flows locally affect the external heat transfer, particularly on the endwall surface. The combination of external and internal convective heat transfer along with solid conduction determines component temperatures, which affect the service life of turbine components. A conjugate heat transfer model is used to measure the non-dimensional external surface temperature, known as overall effectiveness, of an endwall with non-axisymmetric contouring. The endwall cooling methods include internal impingement cooling and external film cooling. Measured values of overall effectiveness show that endwall contouring reduces the impingement effectiveness alone, but increases the effectiveness of film cooling alone. Given the combined case of both impingement and film cooling, the laterally averaged overall effectiveness is not significantly changed between the flat and contoured endwall. Flowfield measurements indicate that the size and location of the passage vortex changes as film cooling is added and as the blowing ratio increases. Because endwall contouring can produce local effects on internal cooling and film cooling performance, the implications for heat transfer should be considered in endwall contour designs.

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