Experimental investigation on effects of cross-flow Reynolds number and blowing ratios to film cooling performance of the Y-shaped hole

Film cooling performance of the compound hole and the Y-shaped hole configurations with the cross-flow coolant channel is investigated experimentally and numerically in this paper. The Reynolds numbers of coolant flow are fixed as 50000 and 100000 respectively. The film cooling effectiveness and heat transfer coefficient were measured by the transient liquid crystal measurement technique under three blowing ratios of 0.5, 1.0 and 2.0 respectively. And flow resistance measurements were also performed to obtain the discharge coefficient of the two film hole configurations. Numerical simulations with Reynolds-averaged Navier-Stokes (RANS) method were performed to explain the experiment results. The results show that the distribution feature of film cooling effectiveness for the compound hole and Y-shaped hole configurations is different. The film cooling effectiveness of the Y-shaped hole configuration is higher than that of the compound hole, and the film spanwise coverage is larger than that of the compound hole under all cases. For two film hole configurations, the heat transfer coefficient increases with the increase of the cross-flow Reynolds number and the blowing ratio. The heat transfer coefficient of the compound hole and Y-shaped hole configurations is close to each other under small cross-flow Reynolds number. However, under large cross-flow Reynolds number, the compound hole configuration has much higher heat transfer coefficient. The discharge coefficient increases gradually with the rising blowing ratio, then tend to a fixed value. Under the condition of the small cross-flow Reynolds number, the discharge coefficient of two film hole configurations is high. The discharge coefficient of the Y-shaped hole configuration is a little higher than that of the compound hole configuration under the condition of the large blowing ratio.

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Experimental Investigation and Optimal Design on the Film Cooling Performance of Fan-Shaped Hole With Vortex Generator Fed by Crossflow

10.1115/gt2021-59144 ◽

2021 ◽

Author(s):

Jie Wang ◽

Chao Zhang ◽

Xuebin Liu ◽

Liming Song ◽

Jun Li ◽

...

Keyword(s):

Reynolds Number ◽

Film Cooling ◽

Vortex Generator ◽

Optimized Design ◽

Combined Model ◽

Cooling Effectiveness ◽

Cooling Performance ◽

Film Cooling Effectiveness ◽

Blowing Ratio ◽

Shaped Hole

Abstract Aiming at investigating the effects of crossflow and vortex generator on film cooling characteristics of fan-shaped hole, the film cooling performance was measured experimentally by infrared camera. The blowing ratio is fixed at 0.5 and 1.5. The Reynolds number of the mainstream based on the hole diameter remains at 7000 and the inlet Reynolds number of crossflow is 40000. The experimental results show that the film cooling performance becomes better when the blowing ratio increases from 0.5 to 1.5 for each model, and the film cooling performance becomes worse under the influence of crossflow. When the blowing ratio is 1.5, the area-averaged film cooling effectiveness of the fan-shaped hole model with vortex generator decreases by 16.6% because of the influence of crossflow. The combined model always performs better compared with the model without vortex generator under all working conditions. When the blowing ratio becomes 1.5, under the influence of crossflow, the area-averaged film cooling effectiveness of the combined model could increase by 14.8%, compared with the model without vortex generator. To further improve the film cooling performance, the global optimization algorithm based on the Kriging method and the CFD technology are coupled to optimize the combined model under crossflow condition at the high blowing ratio, and the optimized design is verified by experiments. The experimental results show that the area-averaged film cooling effectiveness of the optimized design increases by 17.8% compared with the reference model.

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Experimental Investigation of Sweeping Jet Film Cooling in a Transonic Turbine Cascade

Journal of Turbomachinery ◽

10.1115/1.4046548 ◽

2020 ◽

Vol 142 (4) ◽

Author(s):

Mohammad A. Hossain ◽

Munevver E. Asar ◽

James W. Gregory ◽

Jeffrey P. Bons

Keyword(s):

Heat Transfer ◽

Experimental Investigation ◽

Mach Number ◽

Film Cooling ◽

Total Pressure ◽

Suction Surface ◽

Cooling Performance ◽

Aerodynamic Loss ◽

Comparison Results ◽

Shaped Hole

Abstract The sweeping jet (SJ) film cooling hole has shown promising cooling performance compared to the standard shaped hole in low-speed conditions. The present work demonstrates the first attempt of SJ film cooling at an engine relevant Mach number. An experimental investigation was conducted to study the SJ film cooling on a nozzle guide vane suction surface. A well-established additive manufacturing technique commonly known as stereolithography (SLA) was utilized to design a transonic, engine representative vane geometry in which a row of SJ holes was used on the vane suction surface. Experiments were performed in a linear transonic cascade at an exit Mach number of 0.8 and blowing ratios of BR = 0.25–2.23. The measurement of heat transfer was conducted with the transient IR method, and the convective heat transfer coefficient (HTC) and adiabatic film cooling effectiveness were estimated using a dual linear regression technique (DLRT). Aerodynamic loss measurements were also performed with a total pressure Kiel probe at 0.25Cax downstream of the exit plane of the vane cascade. Experiments were also conducted for a baseline-shaped hole (777-hole) for a direct comparison. Results showed that the SJ hole has a wider coolant spreading in the lateral direction near the hole exit due to its sweeping motion that improves the overall cooling performance particularly at high blowing ratios (BR > 1). Aerodynamic loss measurement suggested that the SJ hole has a comparable total pressure loss to the 777-shaped hole.

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Experimental Investigation of Film Cooling Performance on Blade Endwall with Diffusion Slot Holes and Stator-Rotor Purge Flow

Journal of Turbomachinery ◽

10.1115/1.4050120 ◽

2021 ◽

pp. 1-28

Author(s):

Zhi-Qiang Yu ◽

Jianjun Liu ◽

Chen Li ◽

Baitao An ◽

Guang-Yao Xu

Keyword(s):

Film Cooling ◽

Flow Direction ◽

Cross Flow ◽

Orientation Angle ◽

Cooling Effectiveness ◽

Cooling Performance ◽

Film Cooling Effectiveness ◽

Pressure Surface ◽

Blowing Ratio ◽

Shaped Hole

Abstract This paper focuses on the influences of the discrete hole shape and layout on the blade endwall film cooling effectiveness. The diffusion slot hole was first applied to the blade endwall and compared with the fan-shaped hole. The effect of upstream purge slot injection on the film cooling performance of the discrete hole was also investigated. Experiments were performed in a linear cascade with a exit Reynolds number of 2.64×105. The film cooling effectiveness on the blade endwall were measured by the pressure sensitive paint technique. Results indicate that the diffusion slot hole significantly increases the film cooling effectiveness on the blade endwall compared to the fan-shaped hole, especially at high blowing ratio. The maximum relative increment of the cooling effectiveness is over 40%. The layout with the discrete holes arranged lining up with the tangent direction of the blade profile offset curves exhibits a comparable film cooling effectiveness with the layout with the discrete holes arranged according to the cross-flow direction. The film cooling effectiveness on the pressure surface corner is remarkably enhanced by deflecting the hole orientation angle towards the pressure surface. The combination of purge slot and diffusion slot holes supplies a full coverage film cooling for the entire blade endwall at coolant mass flow ratio of the purge slot of 1.5% and blowing ratio of 2.5. In addition, the slot injection leads to a non-negligible influence on the cooling performance of the discrete holes near the separation line.

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Experimental Investigation of Film Cooling Performance on Blade Endwall With Diffusion Slot Holes and Stator-Rotor Purge Flow

Volume 7B: Heat Transfer ◽

10.1115/gt2020-14417 ◽

2020 ◽

Author(s):

Zhiqiang Yu ◽

Jianjun Liu ◽

Chen Li ◽

Baitao An ◽

Guangyao Xu

Keyword(s):

Film Cooling ◽

Flow Direction ◽

Cross Flow ◽

Orientation Angle ◽

Cooling Effectiveness ◽

Cooling Performance ◽

Film Cooling Effectiveness ◽

Pressure Surface ◽

Offset Curves ◽

Shaped Hole

Abstract This paper focuses on the influences of the discrete hole shape and layout on the blade endwall film cooling effectiveness. The effect of upstream purge slot injection on the film cooling performance of the discrete hole was also investigated. The diffusion slot hole was first applied to the blade endwall. As a comparison, the cooling performance of the fan-shaped hole was also measured. Totally, six discrete-hole cooling configurations (2 hole shapes × 3 layouts) were investigated. Experiments were performed in a seven-blade linear cascade with the exit Reynolds number of 2.64 × 105. The average blowing ratios (BR) of the discrete holes changed from 0.5 to 2.5, and the coolant mass flow ratio of the purge slot (MFR) was fixed at MFR = 1.5%. The distributions of the cooling effectiveness on the blade endwall were measured by the pressure sensitive paint technique. Results indicate that the diffusion slot hole significantly increases the film cooling effectiveness on the blade endwall compared to the fan-shaped hole, especially at high blowing ratio. The maximum relative increment of the cooling effectiveness is over 40%. The layout with the discrete holes arranged lining up with the tangent direction of the blade profile offset curves exhibits a comparable film cooling effectiveness with the layout with the discrete holes arranged according to the cross-flow direction. The film cooling effectiveness on the pressure surface corner is remarkably enhanced by deflecting the hole orientation angle towards the pressure surface. The combination of purge slot and diffusion slot holes supplies a full coverage film cooling for the entire blade endwall at MFR = 1.5% and BR = 2.5. In addition, the slot injection leads to a non-negligible influence on the cooling performance of the discrete holes near the separation line.

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Experimental Investigation of Sweeping Jet Film Cooling in a Transonic Turbine Cascade

Volume 5B: Heat Transfer ◽

10.1115/gt2019-91678 ◽

2019 ◽

Author(s):

Mohammad A. Hossain ◽

Munevver E. Asar ◽

James W. Gregory ◽

Jeffrey P. Bons

Keyword(s):

Heat Transfer ◽

Experimental Investigation ◽

Mach Number ◽

Film Cooling ◽

Total Pressure ◽

Suction Surface ◽

Cooling Performance ◽

Aerodynamic Loss ◽

Comparison Results ◽

Shaped Hole

Abstract The sweeping jet (SJ) film cooling hole has shown promising cooling performance compared to the standard shaped hole in low-speed conditions. The present work demonstrates the first attempt of sweeping jet film cooling at an engine relevant Mach number. An experimental investigation was conducted to study the sweeping jet film cooling on a nozzle guide vane suction surface. A well-established additive manufacturing technique commonly known as Stereolithography (SLA) was unitized to design a transonic, engine representative vane geometry in which a row of SJ holes was used on the vane suction surface. Experiments were performed in a linear transonic cascade at an exit Mach number of 0.8 and blowing ratios of BR = 0.25–2.23. The measurement of heat transfer was conducted with the transient IR method and the convective heat transfer coefficient (HTC) and adiabatic film cooling effectiveness were estimated using a dual linear regression technique (DLRT). Aerodynamic loss measurements were also performed with a total pressure Kiel probe at 0.25Cax downstream of the exit plane of the vane cascade. Experiments were also conducted for a baseline shaped hole (777-hole) for a direct comparison. Results showed that the SJ hole has a wider coolant spreading in the lateral direction near the hole exit due to its sweeping action that improves the overall cooling performance particularly at high blowing ratios (BR>1). Aerodynamic loss measurement suggested that the SJ hole has a comparable total pressure loss to the 777-shaped hole.

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CFD Study of Combined Impingement and Film Cooling Flow on the Internal Surface Temperature Distribution of a Vane

International Journal of Turbo and Jet Engines ◽

10.1515/tjj-2019-0010 ◽

2019 ◽

Vol 0 (0) ◽

Author(s):

Arun Kumar Pujari

Keyword(s):

Reynolds Number ◽

Surface Temperature ◽

Film Cooling ◽

Guide Vane ◽

Cross Flow ◽

Internal Surface ◽

Flow Reynolds Number ◽

Nozzle Guide Vane ◽

Lift Off ◽

Nozzle Guide

Abstract Conjugate heat transfer analysis is carried out on the internal surface of the first-stage nozzle guide vane of a gas turbine, which has both impingement and film cooling holes. The mainstream flow Reynolds number and internal coolant flow Reynolds number systematically changed and its effect on internal local surface temperature variation is studied. It is found that an increase in the coolant mass flow rate causes a non-uniform decrease in the local internal surface temperature. The external film coolant jet-lift off and internal impingement cross-flow are significant contributors to the non-uniform variation in surface temperature. It is also observed that the leading edge regions are prone to jet lift-off, whereas the tip regions of the suction surface are prone to self-induced cross-flow, due to which hot patches are formed in these regions. Hot patches are observed near the hub regions of a pressure surface due to the reduced film thickness on the external surface. From these observations it is concluded that local values of internal surface temperature are differently affected in different regions of the vane surface for a given combination of mainstream and coolant flow rates. Therefore, the conventional method of obtaining the internal temperature distributions by considering generalized geometries may not yield accurate solutions, in predicting the life of the nozzle guide vane.

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