Computational Investigations in the Trailing Edge Region of Cooled Turbine Vane: Comparison of Different Channel Shapes

2007 ◽  
Author(s):  
N. Kulasekharan ◽  
B. V. S. S. S. Prasad
Keyword(s):  
Incompressible Flows ◽  
Three Dimensional ◽  
Constant Heat Flux ◽  
Trailing Edge ◽  
Pressure Loss Coefficient ◽  
Pin Fin ◽  
Pin Fins ◽  
Rib Turbulators ◽  
Energy Equations ◽  
End Wall

Thermal hydraulic characteristics of coolant flow through passages consisting of rib turbulators, pin fin array and trailing edge slot are reported. Channels of straight, trapezoidal and curved shapes are considered. Continuity, momentum and energy equations for a three dimensional incompressible flows are solved. A constant heat flux value is specified over the coolant channel walls, rib surfaces and circumferential faces of the pin-fins. Total pressure loss coefficient, pin end-wall and pin surface averaged Nusselt number are estimated and presented for the pin array, for Reynolds number ranging from 20,000 to 40,000. Cambered channels showed highest pin end wall averaged heat transfer than trapezoidal channel, which is higher than the straight channel.

Influence of Rib Turbulators on Pin-Fin Heat Transfer in the Trailing Region of Gas Turbine Vane: A Numerical Study

2006 ◽  
Author(s):  
N. Kulasekharan ◽  
B. V. S. S. S. Prasad
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Constant Heat Flux ◽  
Transfer Coefficients ◽  
Flux Boundary Condition ◽  
Pin Fin ◽  
Pin Fins ◽  
Rib Turbulators

A numerical investigation is carried out for estimating the influence of rib turbulators on heat transfer and pressure drop of staggered non-uniform pin-fin arrays of different shapes, in a simulated cambered vane trailing region. Pin-fins of square, circular and the diamond shapes, each of two sizes (d) were chosen. The ratio of span-wise pitch to longitudinal pitch is 1.06 and that to the pin size are 4.25 and 3.03, for all pin shapes. A constant heat flux boundary condition is assumed over the coolant channel walls, rib surfaces and circumferential faces of the pin-fins. Reynolds number is varied (20,000<ReD<40,000) by changing the coolant outlet to inlet pressure ratio. Pin end-wall and pin surface averaged heat transfer coefficients and Nusselt numbers are estimated and detailed contours of heat transfer coefficient on both the pressure and suction surfaces are presented. Whilst there is an enhancement in heat transfer and pressure drop with ribs for all the pin shapes, diamond pins have shown the highest enhancement values for both ribbed and non-ribbed configuration.

Evaluation of Wall Heat Transfer in Blade Trailing-Edge Cooling Passage

2013 ◽  
Vol 284-287 ◽  
pp. 738-742 ◽  
Author(s):  
Yu Feng Yao ◽  
Marwan Effendy ◽  
Jun Yao
Keyword(s):  
Heat Transfer ◽  
Transfer Model ◽  
Internal Cooling ◽  
Wall Heat Transfer ◽  
Trailing Edge ◽  
Pin Fin ◽  
Pin Fins ◽  
Cooling Passage ◽  
End Wall ◽  
Good Agreement

Model configurations of turbine blade trailing-edge internal cooling passage with staggered elliptic pin-fins in streamwise and spanwise are adopted for numerical investigation using computational fluid dynamics (CFD). Grid refinement study is performed at first to identify a baseline mesh, followed by validation study of passage total pressure loss, which gives 2% and 4% discrepancies respectively for two chosen configurations in comparison with experimental measurements. Further investigations are focused on evaluation of wall heat transfer coefficient (HTC) of both pin-fin and end walls, and it is found that CFD predicted pin-fin wall HTC are generally in good agreement with test data for the streamwise staggered elliptic pin-fins, but not the spanwise staggered elliptic pin-fins in which some discrepancies occur. CFD predicted end wall HTC have shown reasonable good agreement for the first three rows, but discrepancies seen in downstream rows are around a factor of 2-3. A ratio of averaged pin-fin and end walls HTC is estimated 1.3-1.5, close to that from a circular pin-fin configuration that has 1.8-2.1. Further study should focus on improving end wall HTC predictions, probably through a conjugate heat transfer model.

Numerical Investigation of Pin-Fin Influences on Cooling Air Flow Characteristics in Blade Trailing Edge Region

2019 ◽  
Author(s):  
Weilong Wu ◽  
Huazhao Xu ◽  
Jianhua Wang ◽  
Xiangyu Wu ◽  
Lei Wang
Keyword(s):  
Turbine Blade ◽  
Flow Characteristics ◽  
Baseline Model ◽  
Trailing Edge ◽  
Performance Function ◽  
Pin Fin ◽  
Low Pressure Turbine ◽  
Pin Fins ◽  
Turbine Design ◽  
Cooling Air

Abstract This paper numerically investigated the influences of pin-fin size and layout on the flow characteristics of cooling air in the trailing edge of a real low pressure turbine blade. The discussion was given first for the baseline model without pin fins (denoted as M0) under a turbine design condition and two off design conditions. Then a comparison of the flow fields in the turbine blade especially in the trailing edge region was performed with three more trailing edge models, with the purpose of discovering the benefits of using pin fin configurations in a real low pressure turbine blade. The other three models (denoted as M1, M2, M3) have pin fins in different diameters and arrangements. The M1 model has a row of 13 pin fins with a diameter of 2mm, and the M2 and M3 models have two rows of pin fins arranged in a staggered pattern with a diameter of 1.2mm. Compared to the baseline model M0, it is shown that an addition of pin fin configurations helps greatly to improve cooling flow distributions and to mitigate the blockage of coolant in trailing slots. Meanwhile, the adoption of pin fins has not only affected significantly the flow field in the trailing passage but also has moderately affected flow fields in the middle and forward cooling passages. Increasing pressure ratio can increase total mass flow rate with no significant change in flow patterns. The baseline blade Model M0 shows a high value of 6 for a friction loss related performance function at the turbine design condition. However, only a moderate increase in the value of the performance function is discovered for all the three blades with pin fins.

Investigation of Innovative Trailing Edge Cooling Configurations With Enlarged Pedestals and Square or Semicircular Ribs: Part II—Numerical Results

2008 ◽  
Author(s):  
Emiliano Di Carmine ◽  
Bruno Facchini ◽  
Luca Mangani
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Convective Heat Transfer Coefficient ◽  
Turbulence Models ◽  
Internal Cooling ◽  
Trailing Edge ◽  
Pressure Losses ◽  
Structural Resistance ◽  
Pin Fins ◽  
Rib Turbulators

Trailing edge is a critical region for turbine airfoils since this part of the blade has to match aerodynamic, cooling and structural requirements at the same time. In fact aerodynamic losses are strictly related to trailing edge thickness which, on the contrary, tends to be increased to implement an internal cooling system, in order to face high thermal loads. At the moment the most employed devices consist of pin fins of various shapes, which contribute to both heat transfer enhancement and structural resistance improvement. Enlarged pedestals decrease pressure losses in comparison with multirow pin fins, even if the heat transfer increase is limited. This work deals with the investigation of the usage of enlarged pedestals, inserted in a wedge shaped duct, in conjunction with square or semicircular rib turbulators. The aim of the analysis is the evaluation of the convective Heat Transfer Coefficient (HTC) distribution over the endwall surface and the pressure drop of the converging duct. Numerical analysis used 3D RANS calculations. An in-house modified object-oriented CFD code and a commercial one were used. Several turbulence models and mesh types were tested. Numerical calculations were compared with experimental results obtained on the same geometries using a transient Thermochromic Liquid Crystals (TLC) based technique. Goals of this comparison are both the evaluation of the accuracy of CFD packages with standard two equation turbulence models in heat transfer problems with complex geometries and the analysis of flow details to complete and support experimental activity.

Pressure Drop and Heat Transfer Characteristics of Pin Fin Enhanced Microgaps in Single Phase Microfluidic Cooling

2013 ◽  
Author(s):  
Zhimin Wan ◽  
Yogendra K. Joshi
Keyword(s):  
Three Dimensional ◽  
Thermal Characteristics ◽  
Practical Interest ◽  
Electrical Performance ◽  
Signal Delay ◽  
Pin Fin ◽  
Dense Arrays ◽  
Pin Fins ◽  
3D Stacking ◽  
Semiconductor Chips

Three dimensional (3D) stacking of semiconductor chips is an emerging technology which promises improved electrical performance including improved bandwidth, reduced wire interconnection lengths, and reduced signal delay. However, due to the higher power density per unit volume of the stacking, it poses great challenge for thermal management. Inter-tier microfluidic cooling with microgaps with surface area enhancements such as pin fins can potentially achieve superior thermal performance. As such, the hydraulic and thermal characteristics of this configuration over parametric ranges of practical interest are important. Conventional correlations developed in the literature for macropin fins show large errors for dense arrays of micropins. In this work, the hydraulic and thermal characteristics of a microgap with pin fin were investigated for a large range of Reynolds number (Re) based on pin fin diameter (Dp) by numerical modeling. The effects of the pin fin dimensions including diameter, transversal spacing, longitudinal spacing, height and Re on the friction factor (f) and colburn j factor were studied. Correlations of the f and j for dense arrays of micro pins are developed based on parametric runs over 22< Re <357, pin fin diameter of 100 μm, pitch/ diameter ratios of 1.5 ∼ 2.25, and height/ diameter ratios of 1.5 ∼ 2.25. The validity of the correlations is confirmed by experiments. Lastly, a parametric optimization was done and the thermal resistance of the microgap with 150 W heat generation is reduced by 28.5% with the optimized dimensions for a given pumping power compared to an un-optimized pin fin configuration.

Shape Optimization of Pin Fin Arrays Using Gaussian Process Surrogate Models Under Design Constraints

2020 ◽  
Author(s):  
Shinjan Ghosh ◽  
Sudeepta Mondal ◽  
Jayanta S. Kapat ◽  
Asok Ray
Keyword(s):  
High Pressure ◽  
Pressure Drop ◽  
Gas Turbine ◽  
Optimization Problem ◽  
Trailing Edge ◽  
Design Constraints ◽  
Pin Fin ◽  
Pin Fins ◽  
High Pressure Drop ◽  
Pin Fin Arrays

Abstract Internal cooling channels with pin-fin arrays are an important part of gas turbine blade trailing edge design. Short pin-fins act as turbulators in high aspect ratio channels to increase heat transfer and provide structural support to the trailing edge of the blade. Such pin fins however also result in a high pressure drop owing to chaotic flow phenomenon in these highly turbulent flows. High pressure-drop results in higher compressor work due to increased power consumption to push the coolant through these passages. Hence, optimizing the design of pin fin arrays is key to increasing the efficiency of real gas turbine cycles by handling higher turbine inlet temperature and increasing blade life. Moreover, the design process of such pin fin arrays can be computationally very expensive, since it typically involves high-fidelity CFD simulations. The optimization problem involves maximizing Nusselt number, while keeping the friction factor as a constraint. To address this problem, a computationally efficient approach involving Gaussian Processes (GP) surrogate modeling and constrained Bayesian Optimization (BO) has been carried out for optimizing the thermal performance of the pin fin arrays. The multidimensional search space of design parameters includes pin-fin dimensions and shape of the resulting pin-fins. The optimization problem is solved under computational budget limitations and design constraints. A ‘drop’ like optimal design is obtained which has a lower pressure drop and higher Nu compared to the baseline.

Compact Transient Thermal Model of Microfluidically Cooled Three-Dimensional Stacked Chips With Pin-Fin Enhanced Microgap

2021 ◽  
Vol 143 (3) ◽  
Author(s):  
Yuanchen Hu ◽  
Md Obaidul Hossen ◽  
Zhimin Wan ◽  
Muhannad S. Bakir ◽  
Yogendra Joshi
Keyword(s):  
Heat Transfer ◽  
Integrated Circuit ◽  
High Performance ◽  
Heat Dissipation ◽  
Three Dimensional ◽  
Heat Removal ◽  
Power Estimation ◽  
Leakage Power ◽  
Pin Fin ◽  
Pin Fins

Abstract Three-dimensional (3D) stacked integrated circuit (SIC) chips are one of the most promising technologies to achieve compact, high-performance, and energy-efficient architectures. However, they face a heat dissipation bottleneck due to the increased volumetric heat generation and reduced surface area. Previous work demonstrated that pin-fin enhanced microgap cooling, which provides fluidic cooling between layers could potentially address the heat dissipation challenge. In this paper, a compact multitier pin-fin single-phase liquid cooling model has been established for both steady-state and transient conditions. The model considers heat transfer between layers via pin-fins, as well as the convective heat removal in each tier. Spatially and temporally varying heat flux distribution, or power map, in each tier can be modeled. The cooling fluid can have different pumping power and directions for each tier. The model predictions are compared with detailed simulations using computational fluid dynamics/heat transfer (CFD/HT). The compact model is found to run 120–600 times faster than the CFD/HT model, while providing acceptable accuracy. Actual leakage power estimation is performed in this codesign model, which is an important contribution for codesign of 3D-SICs. For the simulated cases, temperatures could decrease 3% when leakage power estimation is adopted. This model could be used as electrical-thermal codesign tool to optimize thermal management and reduce leakage power.

Effect of Rotation on Heat Transfer in AR = 2:1 and AR = 4:1 Channels Connected by a Series of Crossover Jets

2021 ◽  
pp. 1-19
Author(s):  
Srivatsan Madhavan ◽  
Prashant Singh ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Flow Direction ◽  
Gas Turbine Blade ◽  
Trailing Edge ◽  
Cooling Flow ◽  
Liquid Crystal Thermography ◽  
Pin Fins ◽  
Rib Turbulators

Abstract Detailed heat transfer measurements using transient liquid crystal thermography were performed on a novel cooling design covering the mid-chord and trailing edge region of a typical gas turbine blade under rotation. The test section comprised of two channels with aspect ratio (AR) of 2:1 and 4:1, where the coolant was fed into the AR = 2:1 channel. Rib turbulators with a pitch-to-rib height ratio (p/e) of 10 and rib height-to-channel hydraulic diameter ratio (e/Dh) of 0.075 were placed in the AR = 2:1 channel at 60° relative to flow direction. The coolant after entering this section was routed to the AR = 4:1 section through a set of crossover jets. The 4:1 section had a realistic trapezoidal shape that mimics the trailing edge of an actual gas turbine blade. The pin fins were arranged in a staggered array with a center-to-center spacing of 2.5 times pin diameter. The trailing edge section consisted of radial and cutback exit holes for flow exit. Experiments were performed for Reynolds number of 20,000 at Rotation numbers (Ro) of 0, 0.1 and 0.14. The channel averaged heat transfer coefficient on trailing side was ~28% (AR = 2:1) and ~7.6% (AR = 4:1) higher than the leading side for Ro = 0.1. It is shown that the combination of crossover jets and pin-fins can be an effective method for cooling wedge shaped trailing edge channels over axial cooling flow designs.

Numerical Investigation on the Flow and Heat Transfer Characteristics of the Superheated Steam in the Wedge Duct With Pin-Fins

2013 ◽  
Author(s):  
Gaoliang Liao ◽  
Xinjun Wang ◽  
Xiaowei Bai ◽  
Ding Zhu ◽  
Jinling Yao
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Three Dimensional ◽  
Heat Transfer Characteristics ◽  
Pin Fin ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Pin Fins ◽  
Steam Superheat

By using the CFX software, the three-dimensional flow and heat transfer characteristics in the cooling duct with pin-fin in the blade trailing edge were numerically simulated. The effects of pin-fin arrangements, Reynolds number, steam superheat degrees, streamwise pin density and convergence angle of the wedge duct on the flow and heat transfer characteristics were analysed. The results show that the Nusselt number on the endwall and pin-fin surfaces as well as the pin-fin row averaged Nusselt number increase with the increasing of Reynolds number, while it decreased with the with the increasing of X/D. The pressure drop increases with the increasing of Reynolds number while decreases with the increasing of X/D in the wedge duct. The degree of superheat has little effect on the pressure loss in the wedge duct. A comprehensive analysis and comparison show that the highest thermal performance is reached in the wedge duct when the value of X/D is 1.5.

Analysis of Flow and Heat Transfer in the End-Wall Region of a Turbine Blade Passage

2000 ◽  
Author(s):  
Yumin Xiao ◽  
R. S. Amano
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Leading Edge ◽  
Horseshoe Vortex ◽  
High Heat ◽  
Wall Region ◽  
Trailing Edge ◽  
High Heat Transfer ◽  
Transfer Region ◽  
End Wall

A numerical study has been performed to predict a three-dimensional turbulent flow and end-wall heat transfer in a blade passage. The complex three-dimensional flow in the end-wall region has an important impact on the local heat transfer. The leading edge horseshoe vortex, the leading edge corner vortices, the passage vortex, and the trailing edge wake cause large variations in the entire end-wall region. The heat transfer distributions in the end-wall region are calculated and the mechanism for the high heat transfer region has been revealed. The calculations show that the algebraic turbulence model lacks the ability to predict the heat transfer in the transition region, but it is valid in other flow region. The local high heat transfer downstream of the trailing edge is enhanced by the wake downstream of the trailing edge. The horseshoe vortex results a high heat transfer region near the leading edge and induces the leading edge corner vortices which cause high heat transfer on the end-wall at both sides of blade end-wall corner.

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