Flow and Heat Transfer in a High-Aspect-Ratio Rib-Roughed Cooling Channel with Longitudinal Intersecting Ribs

2018 ◽  
Vol 59 (4) ◽  
pp. 679-686 ◽  
Author(s):  
C. Zhang ◽  
Z. Wang ◽  
J. Kang
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Cooling Channel ◽  
Flow And Heat Transfer

Influence of the 180° Bend Geometry on the Pressure Loss and Heat Transfer in a High Aspect Ratio Rectangular Smooth Channel

2004 ◽  
Author(s):  
Detlef Pape ◽  
Herve´ Jeanmart ◽  
Jens von Wolfersdorf ◽  
Bernhard Weigand
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Aspect Ratio ◽  
Cross Section ◽  
High Aspect Ratio ◽  
Pressure Loss ◽  
Rectangular Cross Section ◽  
Flow Structures ◽  
Cooling Channel ◽  
Smooth Channel

An experimental and numerical investigation of the pressure loss and the heat transfer in the bend region of a smooth two-pass cooling channel with a 180°-turn has been performed. The channels have a rectangular cross-section with a high aspect ratio of H/W = 4. The heat transfer has been measured using the transient liquid crystal method. For the investigations the Reynolds-number as well as the distance between the tip and the divider wall (tip distance) are varied. While the Reynolds number varies from 50’000 to 200’000 and its influence on the normalized pressure loss and heat transfer is found to be small, the variations of the tip distance from 0.5 up to 3.65 W produce quite different flow structures in the bend. The pressure loss over the bend thus shows a strong dependency on these variations.

Study On Flow and Heat Transfer Characteristics of a New-Proposed Alternating Elliptical U-Channel in the Mid-Chord Region of Gas Turbine Blade

2021 ◽  
Author(s):  
Kun Xiao ◽  
Juan He ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Thermal Performance ◽  
Cooling Channel ◽  
Gas Turbine Blade ◽  
Heat Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Bend Channel

Abstract This paper proposed an alternating elliptical U-bend cooling channel which can be applied in the mid-chord region of gas turbine blade and manufactured by precision casting, based on the optimal flow field structure deduced from the Field Synergy Principle, and investigated the flow and heat transfer characteristics in this alternating elliptical U-bend cooling channel thoroughly. Numerical simulations were performed by using 3D steady solver of Reynolds-averaged Navier-Stokes equations (RANS) with the standard k-e turbulence model. The influence of alternating of cross section on heat transfer and pressure drop of the channel was studied by comparing with the smooth elliptical U-bend channel. On this basis, the effect of aspect ratio (length ratio of the major axis to the minor axis) and alternating angle were further investigated. The results showed that, in the first pass of the alternating elliptical U-bend channel, for different Re, four or eight longitudinal vortices were generated. In the second pass, the alternating elliptical channel restrained the flow separation to a certain extent and a double-vortex structure was formed. The average Nusselt number of the alternating elliptical U-bend channel was significantly higher than that of the straight channel, but the pressure loss only increased slightly. With the increase of aspect ratio, the thermal performance of the channel increased, and when the alternating angle is between 40° and 90°, the thermal performance nearly kept constant and also the best.

Study on Flow and Heat Transfer Characteristics of a New-Proposed Alternating Elliptical U-Channel

2020 ◽  
Author(s):  
Kun Xiao ◽  
Juan He ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Cross Section ◽  
Internal Cooling ◽  
Short Axis ◽  
Cooling Channel ◽  
Heat Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
First Pass ◽  
The Cross

Abstract This paper proposed an alternating elliptical U-shaped internal cooling channel and investigated the flow and heat transfer characteristics, based on the optimal flow field structure deduced from the Field Synergy Principle. The channel consisted of the straight sections and the transition sections. In the straight sections, the cross section of the channel is ellipse, and in the transition sections, the long axis gradually shortened into the short axis, and the short axis gradually expanded to the long axis. However, the cross-section area of the channel remained unchanged. Numerical simulations were performed to solve 3D steady Reynolds-averaged Navier-Stokes equations (RANS) with the standard k-ε turbulence model. The influence of alternating of the cross section on heat transfer and pressure drop of the channel was studied by comparing with the smooth elliptical U-shaped channel, and all the cases were conducted with the Re numbers from 10,000 to 40,000. On this basis, the investigation on alternating elliptical U-shaped internal cooling channel performance was made mainly into two parts. One was the effect of aspect ratio which was set as from 1.1 to 2.0, while the other was the effect of alternating angle θ which was set as from 10° to 90°. The results showed that for the flow field, there was no vortex in the first pass of the smooth elliptical U-shaped channel. On the contrary, in the first pass of the alternating elliptical U-shaped channel, after the transition section, for different Re numbers, four or eight longitudinal vortices were generated. In the second pass, the flow separation in smooth elliptical U-shaped channel was serious because of the centrifugal force at the elbow, while the alternating elliptical channel restrained the flow separation to a certain extent and formed a double-vortex structure just like the vortex cooling. The average Nusselt number of the alternating elliptical U-shaped channel was significantly higher than that of the straight channel, but the pressure loss increased slightly. In addition, with the increase of aspect ratio, the thermal performance of the channel increased in the study range, and when the alternating angle is between 40° to 90°, the thermal performance nearly kept constant and the best.

scholarly journals Optimization Design of Lattice Structures in Internal Cooling Channel with Variable Aspect Ratio of Gas Turbine Blade

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3954
Author(s):  
Liang Xu ◽  
Qicheng Ruan ◽  
Qingyun Shen ◽  
Lei Xi ◽  
Jianmin Gao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Optimization Model ◽  
Lattice Structure ◽  
Turbine Blades ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Cooling Channels ◽  
Mechanical Performances ◽  
Type Lattice

Traditional cooling structures in gas turbines greatly improve the high temperature resistance of turbine blades; however, few cooling structures concern both heat transfer and mechanical performances. A lattice structure (LS) can solve this issue because of its advantages of being lightweight and having high porosity and strength. Although the topology of LS is complex, it can be manufactured with metal 3D printing technology in the future. In this study, an integral optimization model concerning both heat transfer and mechanical performances was presented to design the LS cooling channel with a variable aspect ratio in gas turbine blades. Firstly, some internal cooling channels with the thin walls were built up and a simple raw of five LS cores was taken as an insert or a turbulator in these cooling channels. Secondly, relations between geometric variables (height (H), diameter (D) and inclination angle(ω)) and objectives/functions of this research, including the first-order natural frequency (freq1), equivalent elastic modulus (E), relative density (ρ¯) and Nusselt number (Nu), were established for a pyramid-type lattice structure (PLS) and Kagome-type lattice structure (KLS). Finally, the ISIGHT platform was introduced to construct the frame of the integral optimization model. Two selected optimization problems (Op-I and Op-II) were solved based on the third-order response model with an accuracy of more than 0.97, and optimization results were analyzed. The results showed that the change of Nu and freq1 had the highest overall sensitivity Op-I and Op-II, respectively, and the change of D and H had the highest single sensitivity for Nu and freq1, respectively. Compared to the initial LS, the LS of Op-I increased Nu and E by 24.1% and 29.8%, respectively, and decreased ρ¯ by 71%; the LS of Op-II increased Nu and E by 30.8% and 45.2%, respectively, and slightly increased ρ¯; the LS of both Op-I and Op-II decreased freq1 by 27.9% and 19.3%, respectively. These results suggested that the heat transfer, load bearing and lightweight performances of the LS were greatly improved by the optimization model (except for the lightweight performance for the optimal LS of Op-II, which became slightly worse), while it failed to improve vibration performance of the optimal LS.

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