Session: 15-07: Numerical Studies of Internal Cooling

Submission Number: 178708

The Effect of Coriolis Force on Flow Mechanism and Heat Transfer in Different Types of U-Shaped Channels 

With the continuous increase in gas turbine inlet temperature, the thermal load on key components such as turbine blades has risen significantly, making efficient internal cooling technology crucial for ensuring blade structural integrity and service life. U-shaped cooling channels are a mainstream solution for internal cooling of gas turbine blades due to their compact structure, good cooling uniformity, and adaptability to complex spatial layouts. However, these channels face a trade-off between enhanced heat transfer and increased flow resistance, and balancing the two is key to design optimization. This study aims to deeply reveal the flow and heat transfer mechanisms in U-shaped channels and provide theoretical support and engineering guidance for the design of high-performance turbine cooling structures.

Using ANSYS Fluent as the computational platform, 3D U-shaped channel models were established (based on typical blade internal cooling channels), including a smooth channel with aspect ratio AR=1:2 and a 60° inclined square rib-enhanced channel (rib height-to-hydraulic diameter ratio e/Dh=0.094, rib pitch-to-height ratio p/e=10). Simulations covered stationary and rotating conditions (rotation number Ro=0–0.5, rotation axis parallel to the channel rotation direction). The SST k-ε turbulence model was adopted (near-wall mesh refinement to ensure Y⁺<1), with Nusselt number ratio Nu/Nu₀ and turbulent kinetic energy (TKE) as core evaluation indices, combined with grid independence verification (2.18 million/3.52 million grids for smooth/ribbed channels).

Results showed: 1) For smooth U-shaped channels, under stationary conditions, flow in the first channel was symmetric; wall non-uniform turbulent stress induced secondary flow converging along the central axis, and centrifugal force in the bend generated typical Dean vortices, with local separation vortices inside increasing TKE. Under rotation (Ro=0.1), Coriolis force altered the flow field—fluid deflected upward in the first channel forming a double-vortex structure, TKE peaked at vortex cores and near-wall shear layers, and the flow field became asymmetric. Heat transfer was uniform stationary but asymmetric rotating: Nu/Nu₀ increased at the trailing surface (Coriolis force aligned with main flow enhancing wall impingement) and decreased at the leading surface. 2) For ribbed channels, stationary conditions saw ribs induce strong secondary flow and impingement, enhancing turbulence, TKE, and uniform heat transfer; rotating conditions saw Coriolis force dominate—core flow deflected to the trailing surface, suppressing leading-side turbulence (lower TKE) while synergizing with rib-induced secondary flow at the trailing surface to strengthen vortices and heat transfer, causing significant TKE and heat transfer asymmetry. 3) For channels with different bend angles (90° vs 135°), at Ro=0.1, 90° channels had higher overall Nu/Nu₀ (stronger secondary flow impingement in bends/second channel inlet) and faster Nu/Nu₀ growth with Ro; 135° channels had milder heat transfer, lower rotation sensitivity, and weaker asymmetry due to reduced impingement.

In conclusion, Coriolis force dominates heat transfer distribution in rotating U-shaped channels, inducing fluid deflection and flow asymmetry (enhanced trailing-side, suppressed leading-side heat transfer, worsening with rotation). Its coupling with rib-induced secondary flow further strengthens turbulence and heat transfer. Channel bend angle significantly affects rotational-secondary flow interaction, with 90° channels showing stronger Coriolis-induced enhancement than 135° ones. This study provides key references for gas turbine blade cooling channel optimization.

 

Presenting Author: Yujie Sun 南京未来能源系统研究院

Presenting Author Biography: Jointly cultivated by Hohai University and Nanjing College, University of Chinese Academy of Sciences (UCAS), I am a Master's degree candidate majoring in Power Engineering, and currently pursuing studies at Nanjing Institute of Future Energy System (Chinese Academy of Sciences).

Authors:

Yujie Sun Nanjing Future Energy System Research Institute
Shanyou Wang National Key Laboratory of Science and Technology on Advanced Light-duty Gas-turbine
Xinyu Ma National Key Laboratory of Science and Technology on Advanced Light-duty Gas-turbine
Qinzong Xu National Key Laboratory of Science and Technology on Advanced Light-duty Gas-turbine
Qiang Du National Key Laboratory of Science and Technology on Advanced Light-duty Gas-turbine