Effect of Blade Profile on Four-Passage Serpentine Configuration Designed to Negate Coriolis Effect on Heat and Fluid Flow

2019 ◽  
Author(s):  
Ajay Sarja ◽  
Srivatsan Madhavan ◽  
Prashant Singh ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Thermal Stresses ◽  
Turbine Blades ◽  
Suction Side ◽  
Stationary Condition ◽  
Internal Cooling ◽  
Coriolis Effect ◽  
Smooth Case ◽  
Smooth Channel ◽  
Rib Turbulators

Abstract Gas turbine blades are equipped with serpentine internal cooling channels with 180-degree bends, through which relatively colder air is routed to cool the internal walls. It has been established that under the influence of rotation, pressure and suction side internal wall heat transfer characteristics are very different, which leads to non-uniform metal temperatures, and hence higher levels of thermal stresses. Present study addresses this non-uniformity in heat transfer using parallel rotation to negate Coriolis effect. Further, the blade curvature does not allow rectangular or trapezoidal passages, which are typically studied. In this paper, we have numerically investigated a realistic design for the four-passage channel, where the cooling design can actually be incorporated in a blade. Four-passage configuration also features 90-degree square shaped rib turbulators, and the corresponding baseline case is smooth channel. Numerical simulations have been carried out at Reynolds numbers of 5000, 10000 and 25000 and Rotation numbers were varied between 0 and 0.25. For smooth case, heat transfer enhancement was found to be higher on suction (leading) side compared to pressure (trailing) side under both stationary and rotating conditions. The enhancement levels between stationary and rotation conditions varied marginally in these designs, indicating that buoyancy effects were insignificant. For ribbed case, the effect of 90-degree rib turbulators on local heat transfer was more pronounced on the suction side when compared to smooth case. Under rotating conditions, it was found that the cooling levels were similar to the stationary condition for both pressure and suction side internal walls.

An Eight-Passage Serpentine Design for Negating Coriolis Force Effect on Heat Transfer

2018 ◽  
Author(s):  
Prashant Singh ◽  
Srinath Ekkad
Keyword(s):  
Heat Transfer ◽  
Coriolis Force ◽  
Thermal Stresses ◽  
Local Level ◽  
Turbine Blades ◽  
Suction Side ◽  
Stationary Condition ◽  
Internal Cooling ◽  
Transfer Coefficients ◽  
Stationary Conditions

Gas turbine blades are subjected to elevated heat loads due to high temperature gases exiting the combustor section. Complex internal and external cooling techniques are employed in blades to protect them from the hot gases. Blades are equipped with internal cooling passages which are connected to each other by 180-degree bends. The coolant flow is typically from blade root-to-tip and blade tip-to-root. Further, since the blades are subjected to rotation, the fluid dynamics and heat transfer inside these serpentine channels get modified. Under the influence of Coriolis force and centrifugal buoyancy force induced by rotation, the heat transfer for radially outward flow enhances on the trailing side (pressure side) and reduces on the leading side (suction side). A reverse trend in heat transfer is observed for radially inward flow. This heat transfer trend leads to non-uniform blade temperature leading to increase in thermal-stresses. Prolonged operation under critical thermal stresses can lead to significant damage and increase in maintenance and overhaul. This paper presents a novel 8-passgae serpentine design, where passages are arranged along the chord of the blade which has similar heat transfer coefficient distribution on both leading and trailing walls. Detailed heat transfer coefficients were measured using transient liquid crystal thermography under stationary and rotating conditions. Heat transfer experiments were carried out for Reynolds numbers ranging from 14264 to 83616 under stationary conditions. Rotation experiments were carried out at Rotation number of 0.05. Heat transfer enhancement levels of approximately two times the Dittus-Boelter correlation (for developed flow in smooth tubes) were obtained under stationary conditions. Under rotating conditions, we found that the heat transfer levels on the leading and trailing sides were similar to each other and with the stationary condition. Some differences in heat transfer were observed on local level, when rotation cases were compared against the stationary cases.

Numerical Simulation of Two Pass Gas Turbine Blade Internal Cooling Channels With 90 Degree Varying Height Ribs

2012 ◽  
Author(s):  
Sourabh Kumar ◽  
R. S. Amano
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Gas Turbine ◽  
Thermal Stresses ◽  
Turbine Blades ◽  
Simulation Software ◽  
Inlet Temperature ◽  
Internal Cooling ◽  
Ribbed Channel ◽  
Smooth Channel

Improvement in thermal efficiency of gas turbine can be obtained by operating it at high inlet temperatures. In addition to improving the performance, the cons of high inlet temperature is high thermal stresses on the turbine blades. To improve life and performance of the blade, improved cooling technologies are desired. The main objective of this paper is to perform computational analysis of the ribs with varying height and compare this with 90 degree ribbed channel and smooth channels. The numerical analysis is carried out using ANSYS-Fluent, a flow modeling simulation software. The flow is assumed to be steady state and flow turbulence is modeled using the k-ε with Standard Wall Functions. Local heat transfer and friction loss in a square duct roughened with 90 degree ribs with varying height is investigated for different Reynolds number. The pitch of the rib is considered to be 10 times the height of rib which is 0.0635 m. The square cross section of the channel is .0508x .0508 m2. The pitch of rib to rib height ratio varies from 10 to 20 at the center of the channel. There is a rib considered at the turn section as well. The numerical simulation produced higher heat transfer for the varying height ribs as compared to 90 degree ribbed channel and smooth channel.

Rib Spacing Effect on Heat Transfer and Pressure Loss in a Rotating Two-Pass Rectangular Channel (AR=1:2) With 45-Degree Angled Ribs

2006 ◽  
Author(s):  
Yao-Hsien Liu ◽  
Lesley M. Wright ◽  
Wen-Lung Fu ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Rectangular Channel ◽  
Spacing Effect ◽  
Turbine Blades ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
Cooling Channels ◽  
Smooth Channel

Rib turbulators are commonly used to enhance the heat transfer within internal cooling passages of advanced gas turbine blades. Many factors affect the thermal performance of a cooling channel with ribs. This study experimentally investigates the effect of rib spacing on the heat transfer enhancement, pressure penalty, and thus the overall thermal performance in both rotating and non-rotating rectangular, cooling channels. In the 1:2 rectangular channels, 45° angled ribs are placed on the leading and trailing surfaces. The pitch of the ribs varies, so rib pitch-to-height (P/e) ratios of 10, 7.5, 5, and 3 are considered. Square ribs with a 1.59 mm × 1.59 mm cross-section are used for all spacings, so the height-to-hydraulic diameter (e/Dh) ratio remains constant at 0.094. With a constant rotational speed of 550 rpm and the Reynolds number ranging from 5000 to 40000, the rotation number in turn varies from 0.2 to 0.02. Because the skewed turbulators induce secondary flow along the length of the rib, the very close rib spacing of P/e = 3, has the best thermal performance in both rotating and non-rotating channels. This close spacing yields the greatest heat transfer enhancement, while the P/e = 5 spacing has the greatest pressure penalty. In addition, the effect of rotation is more pronounced in the channel with the rib spacing of 3. As more ribs are added, the channel is approaching a smooth channel, and the strength of the rotation induced vortices increases.

Multi-Pass Serpentine Cooling Designs for Negating Coriolis Force Effect on Heat Transfer: Smooth Channels

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Prashant Singh ◽  
Yongbin Ji ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Thermal Stresses ◽  
Suction Side ◽  
Reynolds Numbers ◽  
Stationary Condition ◽  
Stationary Case ◽  
Transfer Coefficients ◽  
Liquid Crystal Thermography ◽  
Heat Transfer Coefficients ◽  
Stationary Conditions

The combined action of Coriolis and centrifugal buoyancy forces results in nonuniform heat transfer coefficient on pressure and suction side internal walls, hence leading to nonuniform metal temperatures and increased thermal stresses. The present study addresses the problem of nonuniform heat transfer distribution due to rotation effect and proposes novel designs for serpentine cooling passages, which are arranged along the chord of the blade. The two configurations were four-passage and six-passage serpentine smooth channels. Detailed heat transfer coefficients were measured using transient liquid crystal thermography under stationary and rotating conditions. Heat transfer experiments were carried out for Reynolds numbers ranging from 12,294 to 85,000 under stationary conditions. Rotation experiments were carried out for the Rotation numbers of 0.05 and 0.11. Heat transfer enhancement levels of approximately two times the Dittus–Boelter correlation (for developed flow in smooth tubes) were obtained under stationary conditions. Under rotating conditions, we found that the four-passage configuration had slightly lower heat transfer compared with the stationary case, and the six-passage configuration had higher heat transfer on both the leading and trailing sides compared with the stationary case. The leading and trailing side heat transfer characteristics were near-similar to each other for both the configurations, and the rotating heat transfer was near-similar to the stationary condition heat transfer.

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.

scholarly journals Oscillator Fin as a Novel Heat Transfer Augmentation Device for Gas Turbine Cooling Applications

1998 ◽  
Author(s):  
Oguz Uzol ◽  
Cengiz Camci
Keyword(s):  
Heat Transfer ◽  
Kinetic Energy ◽  
Gas Turbine ◽  
Turbulent Kinetic Energy ◽  
Stokes Equations ◽  
Turbine Blades ◽  
Local Heat Transfer ◽  
Internal Cooling ◽  
Pin Fin ◽  
Heat Transfer Augmentation

A new concept for enhanced turbulent transport of heat in internal coolant passages of gas turbine blades is introduced. The new heat transfer augmentation component called “oscillator fin” is based on an unsteady flow system using the interaction of multiple unsteady jets and wakes generated downstream of a fluidic oscillator. Incompressible, unsteady and two dimensional solutions of Reynolds Averaged Navier-Stokes equations are obtained both for an oscillator fin and for an equivalent cylindrical pin fin and the results are compared. Preliminary results show that a significant increase in the turbulent kinetic energy level occur in the wake region of the oscillator fin with respect to the cylinder with similar level of aerodynamic penalty. The new concept does not require additional components or power to sustain its oscillations and its manufacturing is as easy as a conventional pin fin. The present study makes use of an unsteady numerical simulation of mass, momentum, turbulent kinetic energy and dissipation rate conservation equations for flow visualization downstream of the new oscillator fin and an equivalent cylinder. Relative enhancements of turbulent kinetic energy and comparisons of the total pressure field from transient simulations qualitatively suggest that the oscillator fin has excellent potential in enhancing local heat transfer in internal cooling passages without significant aerodynamic penalty.

Numerical and Experimental Investigation for Internal Cooling of Two Pass Gas Turbine Blades Channels Using Broken V Ribs

2014 ◽  
Author(s):  
Sourabh Kumar ◽  
R. S. Amano
Keyword(s):  
Gas Turbine ◽  
Thermal Stresses ◽  
Turbine Blades ◽  
Research Work ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Inlet Temperature ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Square Duct

Improvements in the thermal efficiency of a gas turbine can be obtained by operating it at high inlet temperatures. This high inlet temperature develops high thermal stresses on the turbine blades in addition to improving the performance. Cooling methodologies are implemented inside the blades to withstand those high temperatures. Four different combinations of broken 60° V ribs in cooling channel are considered. The research work investigates and compares numerically and experimentally, internal cooling of channels with broken V ribs. Local heat transfer in a square duct roughened with 60° V broken ribs is investigated for three different Reynolds numbers. Aspect ratio of the channel is taken to be 1:1. The pitch of the rib is considered to be 10 times the width of the rib, which is 0.0635 m. The square cross section of the channel is 0.508 × 0.508 m2 with 0.6096 m length. This study provides information about the best configuration of a broken V rib in a cooling channel.

scholarly journals Machine Learning for the Development of Data Driven Turbulence Closures in Coolant Systems

2020 ◽  
Author(s):  
James Hammond ◽  
Francesco Montomoli ◽  
Marco Pietropaoli ◽  
Richard D. Sandberg ◽  
Vittorio Michelassi
Keyword(s):  
Heat Transfer ◽  
Complex Geometry ◽  
Gene Expression Programming ◽  
Turbine Blades ◽  
Computational Cost ◽  
Data Driven ◽  
Internal Cooling ◽  
Cooling Channels ◽  
Turbulence Closures ◽  
Improved Model

Abstract This work shows the application of Gene Expression Programming to augment RANS turbulence closure modelling for flows through complex geometry, designed for additive manufacturing. Specifically, for the design of optimised internal cooling channels in turbine blades. One of the challenges in internal cooling design is the heat transfer accuracy of the RANS formulation in comparison to higher fidelity methods, which are still not used in design on account of their computational cost. However, high fidelity data can be extremely valuable for improving current lower fidelity models and this work shows the application of data driven approaches to develop turbulence closures for an internally ribbed duct. Different approaches are compared and the results of the improved model are illustrated; first on the same geometry, and then for an unseen predictive case. The work shows the potential of using data driven models for accurate heat transfer predictions even in non-conventional configurations.

Sign in / Sign up

Export Citation Format

Share Document