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Effects of pin-fins with trapezoidal endwall on heat transfer characteristics in gas turbine blade internal cooling channels

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Abstract

All the studies about pin-fins so far focus on investigating the geometry and configurations of pin-fins to perceive the mechanism of the flow and vortices and maximize the heat transfer efficiency index (HTEI) of the channel. However, questions remained about the effect of the endwall, which can be used to develop and conserve the vortices around the pins. These vortices are typically the key factors influencing the heat transfer capacity of the channel but have not been investigated properly. This work numerically investigates the vortices development and preservation of the channel with three types of endwall-turbulation systems, i.e., the flat endwall, the protruding endwall, and the indented endwall, and the structure of the flow therein. The heat transfer characteristics, which include Nusselt number, friction factor, and HTEI, are studied and compared between all cases with Reynolds numbers ranging from 7400 to 36000. It is reported in the results that, with these new endwall configurations, the high heat transfer regions near the pin-fins are remarkably enlarged compared to the flat endwall. Moreover, in the meantime, both the new endwall configurations enhanced the heat transfer capacity of the channel near the pin-fins, represented by the Nusselt number. The HTEI of these two new designs outperform the baseline case by 37.8 % with the indented endwall and 15.9 % with the protruding endwall. It is discovered that the increase in Nu when applying the trapezoidal endwall to the channel is mainly produced by the combination of the indentations and the protrusions. The protrusions are meant to increase the momentum of the gas passing through it so that the flow will interact more productively with the heated wall. The indentations, on the other hand, enlarge the area of the horseshoe vortices (HV) and preserve it when it is on the verge of collapse. By varying the height of the indentation and the protrusion, it is found that with the small height, both configurations produce a much lower friction factor but much higher heat transfer capacity, leading to a relatively higher HTEI, up to 77.7 % and 41.5 % higher than the flat endwall case of the indented and protruding endwall, respectively. The investigations resulted in diminishing the wake behind the pin-fin with a high-height trapezoidal endwall. For the indented endwall, the deep endwall increases the velocity at the entrance of the indentations and induces more turbulence when the flow exits them. These phenomena result in higher heat transfer of the channel. Besides, the highly elevated protruding endwalls increase heat transfer by creating more turbulence around them and the pin-fins but induce more pressure loss penalty. These results indicated the great potential for improving the heat transfer capability of pin-fins by optimizing endwall con-figurations, which could benefit future designs for industries.

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Abbreviations

D :

Pin-fin diameter, mm

D h :

Equivalent hydraulic diameter of the channel, mm

f :

Friction factor of the heated channel with pin-fins

f0 :

Friction factor of the smooth channel

h :

Heat transfer coefficient, Wm−2 K−1

H :

Height of the rectangular channel/Pin-fins, mm

k :

Fluid thermal conductivity, Wm−1 K−1

L :

Length of the heated channel, mm

L d :

Length of the development channel, mm

L o :

Length of the outlet channel, mm

L p :

Length of the plain heated channel, mm

L t :

Overall length of the channel, mm

Nu :

Heat transfer Nusselt number

Nu 0 :

Nusselt number of the smooth channel

q :

Heat flux on the heated wall, Wm−2

Re :

Reynolds number

S x :

Spanwise spacing of pin-fins, mm

S y :

Streamwise spacing of pin-fins, mm

T b :

Fluid bulk temperature, K

T w :

Wall temperature, K

ΔP :

Pressure drop across the heated channel, Pa

W :

Width of the rectangular channel, mm

Pr :

Prandtl number

η :

Heat transfer efficiency index

λ :

Thermal conductivity, W/(m. K)

μ :

Fluid dynamic viscosity, Ns/m2

ρ :

Fluid density, Kg/m3

RANS :

Reynolds-averaged navier-stokes

HV :

Horseshoe vortices

HTEI :

Heat transfer efficiency index

SST :

Shear stress transport

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Acknowledgments

This research is funded by the Ministry of Education and Training (MoET) under Project No. B2023-BKA-11.

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Authors and Affiliations

  1. School of Mechanical Engineering, Hanoi University of Science and Technology, No 1, Dai Co Viet Road, Hai Ba Trung District, Hanoi, 11615, Vietnam

    Cong-Truong Dinh, Khanh-Duy Cong Do & Hoanh-Son Truong

  2. Viettel Building-Hoa Lac Hi-Tech Park, Viettel Aerospace Institute, Thach That, Hanoi, 100000, Vietnam

    Duy-Hung Chung

Authors
  1. Cong-Truong Dinh
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Correspondence to Cong-Truong Dinh.

Additional information

Cong-Truong Dinh is a lecturer and researcher in Aerospace Propulsion Engineering at Hanoi University of Science and Technology since 2018. He received a Master of Research from University of Paris 6, France in Aerodynamic and Aeroacoustic. He graduated from Inha Uni-versity, South Korea with a Doctoral degree in Mechanical Engineering in 2017. His works are concentrated in Turbomachinery (compressors, turbines, fans and pumps, etc.), Heat-augmentation devices in turbines (ribs, dimples, pin-fins, film-cooling, and rim seal between rotor and stator, etc.), Combustion and Auxiliary systems in Turbomachinery and Propulsion.

Khanh-Duy Cong Do is an engineer of Aerospace Engineering of the School of Mechanical Engineering, Hanoi University of Science and Technology, Hanoi, Vietnam. He received his Engineer Diploma in Aerospace Engineering from Hanoi University of Science and Technology. His research interests include modern heat transfer, aerospace propulsion and CFD.

Duy-Hung Chung is an engineer of Aerospace Engineering of the School of Mechanical Engineering, Hanoi University of Science and Technology, Hanoi, Vietnam. His research interests include aerodynamics, modern heat transfer and aerospace propulsion. He works at Viettel Aerospace Institute (VTX), a vietnamese military-run conglomerate specializes in research and development in the field of aerospace technoloy and satellite communications.

Hoanh-Son Truong is a Associate Professor at Hanoi University of Science and Technology since 2019. He received a Master of Research from Hanoi University of Science and Technology in Machinery Technology in 1993. He graduated from Ritsumeikan University, Japan with a Doctoral degree in Mechanical Engi-neering in 2000. He researchs in Grinding Technology, Manufacturing Technology, CAD/CAM-CNC Technology and High Speed Machining.

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Dinh, CT., Do, KD.C., Chung, DH. et al. Effects of pin-fins with trapezoidal endwall on heat transfer characteristics in gas turbine blade internal cooling channels. J Mech Sci Technol 37, 2199–2210 (2023). https://doi.org/10.1007/s12206-023-2107-9

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  • DOI: https://doi.org/10.1007/s12206-023-2107-9

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