HEAT TRANSFER AND FRICTION IN HIGH ASPECT RATIO INTERNAL COOLING CHANNELS MACHINED WITH VARIOUS TECHNIQUES

2010 ◽  
Author(s):  
Lucky Tran ◽  
Carson Slabaugh ◽  
J. Kapat ◽  
Mark Ricklick
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Internal Cooling ◽  
Cooling Channels

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.

Heat Transfer and Pressure Drop Measurements in a High Aspect Ratio Channel With Circular Pins and Strip Fins

2019 ◽  
Vol 12 (3) ◽  
Author(s):  
Metapun Nuntakulamarat ◽  
Chao-Cheng Shiau ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Aspect Ratio ◽  
Heat Transfer Enhancement ◽  
High Aspect Ratio ◽  
Thickness Effect ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
Transfer Coefficients ◽  
Pin Fin

Abstract This paper focuses on the measurements of heat transfer enhancement and pressure drop of different pin or fin configurations in a high aspect ratio (AR = 9.57/1.2) channel. Two different pin-fin shapes including circular pins and strip fins were studied. Different pin-fin spacings for circular pins (S/D = 2, 4) and strip fins (S/W = 8, 16) were investigated, respectively. In addition, the thickness effect of the strip fin was included in this study. The regionally averaged heat transfer measurement method was used to acquire the heat transfer coefficients on two opposite featured surfaces within the test channel. For each configuration, the tested Reynolds number was ranging from 20,000 to 80,000. The results indicate that the channel with circular pins has better heat transfer enhancement and higher pressure loss than their strip fins counterparts. However, the strip fins are considered better designs in terms of thermal performance. For the gas turbine designers aim at developing an improved internal cooling feature, this work demonstrates the great potential of the strip fins as a novel and effective cooling design compared with the conventional circular pins.

Investigation of a High Aspect Ratio Rectangular Channel With High Blockage Ratio Round-Corner Ribs

2004 ◽  
Author(s):  
Christophe Diette ◽  
Tony Arts ◽  
Olivier Sgarzi ◽  
Emmanuel Laroche
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Large Scale ◽  
Flow Direction ◽  
Flow Behavior ◽  
Rectangular Channel ◽  
Internal Cooling ◽  
Liquid Crystal Thermography ◽  
Main Flow Direction

The flow behavior and heat transfer were measured in a large scale, high aspect ratio, turbine blade rib-roughened internal cooling channel. The ribs, installed on one wall, were inclined at 90 deg with respect to the main flow direction and generated a blockage of 20%. The rib corners were rounded to take into account manufacturing aspects. The bulk flow Reynolds number was 20,000. Pressure drop and velocity measurements were first conducted. Liquid crystal thermography was applied to quantify the heat transfer, not only along the ribbed and the smooth opposite walls but also on the rib itself. Numerical simulations were conducted with two flow solvers, IGG/FINE (Numeca) and MSD (ONERA) and compared with measurements. They also supported the analysis of the flow behavior. The influence of round-corner versus sharp edge ribs was numerically evaluated with IGG/FINE.

Topology Optimization of High Aspect Ratio Internal Cooling Channels As a Design for Additive Manufacturing

2020 ◽  
Author(s):  
Shinjan Ghosh ◽  
Jayanta S. Kapat
Keyword(s):  
Heat Transfer ◽  
Topology Optimization ◽  
Additive Manufacturing ◽  
Aspect Ratio ◽  
Gas Turbine ◽  
High Aspect Ratio ◽  
Design Parameters ◽  
Internal Cooling ◽  
Computational Domain ◽  
Pin Fin

Abstract High aspect ratio channels are a common internal cooling feature in Gas Turbine blades, mostly suitable for the trailing edge region or mid-chord regions. Traditionally such channels are fitted with rib-turbulators and/or pin-fin turbulators to augment heat transfer and prevent material failure. Highly efficient internal cooling of blades can improve the efficiency of a real Gas Turbine power cycle by tolerating higher Turbine Inlet Temperatures (TIT). Multi-physics Topology optimization (TO) has been employed in the current study to find optimized shape of these ducts, with an aim to increase heat transfer, while constraining the pressure drop across the channel. This method, commonly used in structural problems, is a novel topic of research when applied to fluid-thermal studies. Material distribution in the computational domain is varied by changing porosity value in each cell and thereby altering the fluid path and creating a conjugate heat transfer problem. Each cell has a value of Brinkmann porosity factor which either simulates a blockage, or a fluid region depending on a low or high value of this design variable. Hence the degree of freedom is high in this method, and there is no manual bias introduced, unlike in parametric shape optimization which is limited to a few design parameters. The unconventional geometries obtained as an end product of this optimization process can thus be an alternative to existing rib/pin-fin type of cooling geometries. The recent progress in additive manufacturing can now facilitate the manufacturing of complicated shapes. An in-house Open-FOAM solver has been used to carry out the process in only twice the amount of time compared to a regular RANS-CFD. 3-Dimensional rectangular channels with inlet aspect ratios of 4:1 and 8:1 have been considered as baselines with a constant inlet velocity. Resulting optimum geometries were found to have organic tree like branching arrangements of rib-like wall roughness and v-shaped structures.

Investigations on Nusselt Number Enhancement in Ribbed Rectangular Turbine Blade Cooling Channels of Different Aspect Ratios and Rotation Numbers

2013 ◽  
Author(s):  
Behnam Nouri ◽  
Knut Lehmann ◽  
Arnold Kühhorn
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Aspect Ratio ◽  
Turbine Blade ◽  
High Heat ◽  
Internal Cooling ◽  
Cooling Channels ◽  
Aspect Ratios ◽  
Number Distribution ◽  
Nusselt Number Distribution

In the drive for higher cycle efficiencies in gas turbine engines, turbine blades are seeing an increasingly high heat load. This in turn demands improvements in the internal cooling system and a better understanding of both the level and distribution of the internal heat-transfer. A typical approach to enhance the internal cooling of the turbine blade is by casting angled ‘low blockage’ ribs on the walls of the cooling channels. The objective of the present paper is to determine the detailed Nusselt number distribution in rectangular internal channels with ribs. This knowledge can be used to guide the overall design e.g. to achieve high levels of heat-transfer where required. The effects of rotation as well as the interaction effects of the position and direction of ribs on opposite walls of the cooling channel have been investigated. Numerical calculations have been carried out using the commercial CFD code Fluent to investigate the local Nusselt number enhancement factor in rectangular ducts of different aspect ratios (0.5, 1 and 2) which have 45° or 90° angled ribs located on two opposite walls. This has been studied for different Rotation number Ro (0–0.45) and with a Reynolds number >30000. The first series of studies has been carried out with the same experimental setup as by Han [1]. The geometry was slightly changed to avoid the effect of high heat transfer at the entry. This study identifies important vortical structures, which are dependent on the direction and the position of the ribs. This has a profound effect on the distribution of heat-transfer within the passage. It is shown that the two smooth walls of the duct have different average Nusselt number ratio Nu/NuFD enhancement depending on the rib angle. In addition, based on numerical investigations, simple correlations have been developed for the rotational influence of the internal Nusselt number distribution. A major finding is that the effect of rotation is dominant for low aspect ratio channels and the local enhancement due to the rib position and angle is more dominant for high aspect ratio channels.

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