scholarly journals Parametric Studies of Laminated Cooling Configurations: Overall Cooling Effectiveness

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Chen Wang ◽  
Chunhua Wang ◽  
Jingzhou Zhang
Keyword(s):  
Flow Rate ◽  
Film Cooling ◽  
Density Ratio ◽  
Numerical Results ◽  
Hole Diameter ◽  
Coolant Flow ◽  
Coolant Flow Rate ◽  
Cooling Efficiency ◽  
Obvious Effect ◽  
Cooling Effectiveness

Combing the advantages of film cooling, impingement cooling, and enhanced cooling by pin fins, laminated cooling is attracting more and more attention. This study investigates the effects of geometric and thermodynamic parameters on overall cooling effectiveness of laminated configuration, and model experiments were carried out to validate the numerical results. It is found that the increases in film cooling hole diameter and pin fin diameter both result in the increase in cooling effectiveness, but the increases in impingement hole diameter, impingement height, and spanwise hole pitch degrade the cooling performance. The increase of the coolant flow rate causes the increase in cooling efficiency, but this effect becomes weaker at a high coolant flow rate. The coolant-to-mainstream density ratio has no obvious effect on cooling effectiveness but affects wall temperature obviously. Moreover, based on the numerical results, an empirical correlation is developed to predict the overall cooling efficiency in a specific range, and a genetic algorithm is applied to determine the empirical parameters. Compared with the numerical results, the mean prediction error (relative value) of the correlation can reach 8.3%.

Film Cooling Effectiveness Distributions on a Turbine Blade Cascade Platform With Stator-Rotor Purge and Discrete Film Hole Flows

2006 ◽  
Author(s):  
Lesley M. Wright ◽  
Sarah A. Blake ◽  
Je-Chin Han
Keyword(s):  
Turbine Blade ◽  
Flow Rate ◽  
Film Cooling ◽  
Coolant Flow ◽  
Coolant Flow Rate ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Wide Range ◽  
Mainstream Flow ◽  
Purge Flow

An experimental investigation has been completed to obtain detailed film cooling effectiveness distributions on a cooled turbine blade platform within a linear cascade. The platform has a labyrinth-like seal upstream of the blades to model a realistic stator-rotor seal configuration. Additional coolant is supplied to the downstream half of the platform via discrete film cooling holes. The coolant flow rate through the upstream seal varies from 0.5% to 2.0% of the mainstream flow, while the blowing ratio of the coolant through the discrete holes varies from 0.5 to 2.0 (based on the mainstream velocity at the exit of the cascade). Detailed film cooling effectiveness distributions are obtained using the pressure sensitive paint (PSP) technique under a wide range of coolant flow conditions and various freestream turbulence levels (0.75% or 13.4%). The PSP technique clearly shows how adversely the coolant is affected by the passage induced flow. With only purge flow from the upstream seal, the coolant flow rate must exceed 1.5% of the mainstream flow in order to adequately cover the entire passage. However, if discrete film holes are used on the downstream half of the passage, the platform can be protected while using less coolant (i.e. the seal flow rate can be reduced).

Film Cooling Effectiveness Distributions on a Turbine Blade Cascade Platform With Stator-Rotor Purge and Discrete Film Hole Flows

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Lesley M. Wright ◽  
Sarah A. Blake ◽  
Je-Chin Han
Keyword(s):  
Turbine Blade ◽  
Flow Rate ◽  
Film Cooling ◽  
Coolant Flow ◽  
Coolant Flow Rate ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Wide Range ◽  
Mainstream Flow ◽  
Purge Flow

An experimental investigation to obtain detailed film cooling effectiveness distributions on a cooled turbine blade platform within a linear cascade has been completed. The Reynolds number of the freestream flow is 3.1×105, and the platform has a labyrinthlike seal upstream of the blades to model a realistic stator-rotor seal configuration. An additional coolant is supplied to the downstream half of the platform via discrete film cooling holes. The coolant flow rate through the upstream seal varies from 0.5% to 2.0% of the mainstream flow, while the blowing ratio of the coolant through the discrete holes varies from 0.5 to 2.0 (based on the mainstream velocity at the exit of the cascade). Detailed film cooling effectiveness distributions are obtained using the pressure sensitive paint (PSP) technique under a wide range of coolant flow conditions and various freestream turbulence levels (0.75% or 13.4%). The PSP technique clearly shows how adversely the coolant is affected by the passage induced flow. With only purge flow from the upstream seal, the coolant flow rate must exceed 1.5% of the mainstream flow in order to adequately cover the entire passage. However, if discrete film holes are used on the downstream half of the passage, the platform can be protected while using less coolant (i.e., the seal flow rate can be reduced).

Experimental Film Cooling Effectiveness of Multi-Row Patterns on Flat and Step-Down Surfaces

2019 ◽  
Author(s):  
Filippo Baldino ◽  
Mohammad E. Taslim
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Hole Diameter ◽  
Constant Density ◽  
Airfoil Surface ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Flat Surfaces ◽  
Step Down ◽  
Turbine Airfoils

Abstract Multiple rows of film cooling holes have been widely used for the protection of gas turbine airfoils and other hot sections. In the common approach, however, the streamwise surfaces between the film holes may not receive enough protection. The objective of this research was to overcome this issue by introducing a new layout of film cooling, the step-down surfaces. Pressure-sensitive paint technique was used to test three pairs of geometries. Each pair consists of a flat and a step-down surface for back to back comparisons, under otherwise identical conditions. Two rows of 30° angled cylindrical holes of 3.175 mm diameter, exiting at the step bottom corner, introduced the coolant to the surface. Two spanwise pitch-to-diameter ratios of 2 and 4, two row distance to hole diameter of 4 and 8, four blowing ratios of 0.25, 0.5, 0.75 and 1, all at a constant density ratio of 1 were tested. Adding a step-down of the order of 0.8 hole-diameter proved to significantly increase the overall film cooling effectiveness. Two major improvements compared to a flat surfaces were observed: (a) longer streamwise film cooling effectiveness (b) more uniform spanwise distribution of coolant. The main reason of all the improvements is the aerodynamic phenomenon governing the flow evolution, the Coanda effect. The latter, indeed, enhances the flow attachment to the airfoil surface downstream the step.

Film Cooling Measurements for a Laidback Fan-Shaped Hole: Effect of Coolant Crossflow on Cooling Effectiveness and Heat Transfer

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Marc Fraas ◽  
Tobias Glasenapp ◽  
Achmed Schulz ◽  
Hans-Jörg Bauer
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Film Cooling ◽  
Gas Flow ◽  
Density Ratio ◽  
Coolant Flow ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Film Cooling Holes

Internal coolant passages of gas turbine vanes and blades have various orientations relative to the external hot gas flow. As a consequence, the inflow of film cooling holes varies as well. To further identify the influencing parameters of film cooling under varying inflow conditions, the present paper provides detailed experimental data. The generic study is performed in a novel test rig, which enables compliance with all relevant similarity parameters including density ratio. Film cooling effectiveness as well as heat transfer of a 10–10–10 deg laidback fan-shaped cooling hole is discussed. Data are processed and presented over 50 hole diameters downstream of the cooling hole exit. First, the parallel coolant flow setup is discussed. Subsequently, it is compared to a perpendicular coolant flow setup at a moderate coolant channel Reynolds number. For the perpendicular coolant flow, asymmetric flow separation in the diffuser occurs and leads to a reduction of film cooling effectiveness. For a higher coolant channel Reynolds number and perpendicular coolant flow, asymmetry increases and cooling effectiveness is further decreased. An increase in blowing ratio does not lead to a significant increase in cooling effectiveness. For all cases investigated, heat transfer augmentation due to film cooling is observed. Heat transfer is highest in the near-hole region and decreases further downstream. Results prove that coolant flow orientation has a severe impact on both parameters.

Influence of Coolant Density on Turbine Blade Platform Film-Cooling

2012 ◽  
Vol 4 (2) ◽  
Author(s):  
Diganta P. Narzary ◽  
Kuo-Chun Liu ◽  
Je-Chin Han
Keyword(s):  
Turbine Blade ◽  
Flow Rate ◽  
Turbulence Intensity ◽  
Film Cooling ◽  
Density Ratio ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Mainstream Flow ◽  
Purge Flow

Detailed parametric study of film-cooling effectiveness was carried out on a turbine blade platform of a five-blade linear cascade. The parameters chosen were freestream turbulence intensity, upstream stator-rotor purge flow rate, discrete-hole film-cooling blowing ratio, and coolant-to-mainstream density ratio. The measurement technique adopted was temperature sensitive paint (TSP) technique. Two turbulence intensities of 4.2% and 10.5%; three purge flows between the range of 0.25% and 0.75% of mainstream flow rate; three blowing ratios between 1.0 and 1.8; and three density ratios between 1.1 and 2.2 were investigated. Purge flow was supplied via a typical double-toothed stator-rotor seal, whereas the discrete-hole film-cooling was accomplished via two rows of cylindrical holes arranged along the length of the platform. The inlet and the exit Mach numbers were 0.27 and 0.44, respectively. Reynolds number of the mainstream flow was 7.5 * 105 based on the exit velocity and chord length of the blade. Results indicated that platform film-cooling effectiveness decreased with turbulence intensity, increased with purge flow rate and density ratio, and possessed an optimum blowing ratio value.

On Improving Full-Coverage Effusion Cooling Efficiency by Varying Cooling Arrangements and Wall Thickness in Double Wall Cooling Application

2018 ◽  
Author(s):  
Weihong Li ◽  
Xunfeng Lu ◽  
Xueying Li ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Gas Turbine ◽  
Turbine Blade ◽  
Wall Thickness ◽  
Film Cooling ◽  
Density Ratio ◽  
Cooling Efficiency ◽  
Gas Turbine Blade ◽  
Cooling Effectiveness ◽  
Full Coverage ◽  
Double Wall

Overall cooling effectiveness was determined for a full-coverage effusion cooled surface which simulated a portion of a double wall cooling gas turbine blade. The overall cooling effectiveness was measured with high thermal-conductivity artificial marble using infra-red thermography. The Biot number of artificial marble was matched to real gas turbine blade conditions. Blowing ratio ranged from 0.5 to 2.5 with the density ratio of DR = 1.5. A variation of cooling arrangements, including impingement-only, film cooling-only, film cooling with impingement and film cooling with impingement and pins, as well as forward/backward film injection, were employed to provide a systematic understanding on their contribution to improve cooling efficiency. Also investigated was the effect of reducing wall thickness. Local, laterally-averaged, and area-averaged overall cooling effectiveness were shown to illustrate the effects of cooling arrangements and wall thickness. Results showed that adding impingement and pins to film cooling, and decreasing wall thickness increase the cooling efficiency significantly. Also observed was that adopting backward injection for thin full-coverage effusion plate improves the cooling efficiency.

Scaling Considerations for Thermal and Pressure Sensitive Paint Methods Used to Determine Adiabatic Effectiveness

2020 ◽  
Author(s):  
Luke J. McNamara ◽  
Jacob P. Fischer ◽  
James L. Rutledge ◽  
Marc D. Polanka
Keyword(s):  
Mass Transfer ◽  
Flow Rate ◽  
Film Cooling ◽  
Heat Mass Transfer ◽  
Measurement Techniques ◽  
Experimental Methods ◽  
Coolant Flow ◽  
Coolant Flow Rate ◽  
Pressure Sensitive ◽  
Adiabatic Effectiveness

Abstract To be representative of engine conditions, a measurement of film cooling behavior on an experimental model must have certain nondimensional parameters matched, such as the freestream Reynolds number. However, the coolant flow rate must also be properly scaled between the low temperature tests and engine temperatures to accurately predict film cooling effectiveness. This process is complicated by gas property variation with temperature. Additionally, selection of the appropriate coolant flow rate parameter to scale from low to high temperatures is a topic of continued uncertainty. Furthermore, experiments are commonly conducted using thermal measurement techniques with infrared thermography (IR) but the use of pressure sensitive paints (PSPs) implementing the heat-mass transfer analogy is also common. Thus, the question arises of how the adiabatic effectiveness distributions compare between mass transfer experimental methods and thermal experimental methods and whether these two methods are sensitive to coolant flow rate parameters in different ways. In this study, a thermal technique with IR was compared to a heat-mass transfer method with a PSP on a flat plate model with a 7-7-7 film cooling hole. While adiabatic effectiveness is best scaled by accounting for specific heats with the advective capacity ratio (ACR) using thermal techniques, results revealed that PSP measurements are scaled best with the mass flux ratio (M). The difference in these methods has significant implications for engine designers that rely on PSP experimental data to predict engine thermal behavior as PSP is fundamentally not sensitive to the same highly relevant physical mechanisms to which thermal methods are sensitive.

Scaling Flat Plate, Low Temperature Adiabatic Effectiveness Results Using the Advective Capacity Ratio

2019 ◽  
Author(s):  
Jacob P. Fischer ◽  
James L. Rutledge ◽  
Luke J. McNamara ◽  
Marc D. Polanka
Keyword(s):  
Low Temperature ◽  
Specific Heat ◽  
Flat Plate ◽  
Flow Rate ◽  
Density Ratio ◽  
Flux Ratio ◽  
Coolant Flow ◽  
Coolant Flow Rate ◽  
Rate Parameter ◽  
Adiabatic Effectiveness

Abstract Effective design of film cooled engine components requires the ability to predict behavior at engine conditions. This is commonly accomplished through low temperature testing on scaled up geometries. The adiabatic effectiveness, η, is one indicator of the performance of a film cooling scheme. Performing an experiment to measure η in a low temperature wind tunnel requires appropriate selection of the coolant flow rate. Perhaps the most common flow rate parameter that is used to characterize the coolant flow relative to the freestream is the mass flux ratio, or blowing ratio, M. This is usually used in lieu of the velocity ratio to account for the fact that the density of the coolant is typically much larger than that of the hot freestream gas. Numerous studies have taken place evaluating the ability of M to properly scale the effects of density ratio and its performance has produced mixed results. The momentum flux ratio, I, is an alternative that is also found to have mixed success, leading some to recommend matching the density ratio to allow simultaneous matching of M and I. Nevertheless, widely varying results in the literature regarding the efficacy of these coolant flow rate parameters to scale the density ratio suggests there may be other largely ignored effects playing a role in the thermal physics. In the present work, thermal experiments were performed to measure adiabatic effectiveness on a flat plate with a single 7-7-7 shaped hole. Various coolant gases were used to give a large range of thermodynamic property variations. It is shown that a relatively new coolant flow rate parameter that accounts for not only density variations but also specific heat variations, the advective capacity ratio (ACR), far exceeds the ability of either M or I to provide matched adiabatic effectiveness between the various coolant gases that exhibit extreme property differences. Particularly considering that the specific heat of the coolant in an engine is significantly lower than the specific heat of the freestream gas, ACR is shown to be appropriate for characterizing non-separating coolant flow situations.

On Improving Full-Coverage Effusion Cooling Efficiency by Varying Cooling Arrangements and Wall Thickness in Double Wall Cooling Application

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Weihong Li ◽  
Xunfeng Lu ◽  
Xueying Li ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Gas Turbine ◽  
Turbine Blade ◽  
Wall Thickness ◽  
Film Cooling ◽  
Density Ratio ◽  
Cooling Efficiency ◽  
Gas Turbine Blade ◽  
Cooling Effectiveness ◽  
Full Coverage ◽  
Double Wall

Overall cooling effectiveness was determined for a full-coverage effusion cooled surface which simulated a portion of a double wall cooling gas turbine blade. The overall cooling effectiveness was measured with high thermal-conductivity artificial marble using infrared thermography. The Biot number of artificial marble was matched to real gas turbine blade conditions. Blowing ratio ranged from 0.5 to 2.5 with the density ratio of DR = 1.5. A variation of cooling arrangements, including impingement-only, film cooling-only, film cooling with impingement, and film cooling with impingement and pins, as well as forward/backward film injection, was employed to provide a systematic understanding on their contribution to improve cooling efficiency. Also investigated was the effect of reducing wall thickness. Local, laterally averaged, and area-averaged overall cooling effectiveness were shown to illustrate the effects of cooling arrangements and wall thickness. Results showed that adding impingement and pins to film cooling, and decreasing wall thickness increase the cooling efficiency significantly. Also observed was that adopting backward injection for thin full-coverage effusion plate improves the cooling efficiency.

Influence of Coolant Density on Turbine Blade Platform Film-Cooling

2009 ◽  
Author(s):  
Diganta P. Narzary ◽  
Kuo-Chun Liu ◽  
Je-Chin Han
Keyword(s):  
Turbine Blade ◽  
Flow Rate ◽  
Turbulence Intensity ◽  
Film Cooling ◽  
Density Ratio ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Mainstream Flow ◽  
Purge Flow

Detailed parametric study of film-cooling effectiveness was carried out on a turbine blade platform of a five-blade linear cascade. The parameters chosen were — freestream turbulence intensity, upstream stator-rotor purge flow rate, discrete-hole film-cooling blowing ratio, and coolant-to-mainstream density ratio. The measurement technique adopted was temperature sensitive paint (TSP) technique. Two turbulence intensities of 4.2% and 10.5%; three purge flows between the range of 0.25% and 0.75% of mainstream flow rate; three blowing ratios between 1.0 and 2.0; and three density ratios between 1.1 and 2.1 were investigated. Purge flow was supplied via a typical double-toothed stator-rotor seal, whereas the discrete-hole film cooling was accomplished via two rows of cylindrical holes arranged along the length of the platform. The inlet and the exit Mach numbers were 0.27 and 0.44, respectively. Reynolds number of the mainstream flow was 7.5*105 based on the exit velocity and chord length of the blade. Results indicated that platform film-cooling effectiveness decreased with turbulence intensity, increased with purge flow rate and density ratio, and possessed an optimum blowing ratio value. The improved effectiveness with density ratio was further validated by the pressure sensitive paint (PSP) technique.

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