Heat Transfer Analysis of a Wedge Shaped Duct With Pin Fin and Pedestal Arrays: A Comparison Between Numerical and Experimental Results

2004 ◽  
Author(s):  
Antonio Andreini ◽  
Carlo Carcasci ◽  
Andrea Magi
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Experimental Results ◽  
Heat Transfer Analysis ◽  
Bottom Surface ◽  
Mean Flow ◽  
Trailing Edge ◽  
Pin Fin

The use of pin fin arrays in channels is one of the best choices to enhance overall heat transfer in gas turbine trailing edge blade cooling. Furthermore, in this particular application, the use of cross-pins in the trailing edge section of a turbine blade is a good way for supplying structural integrity to the blade itself. In this paper, results of several 3D RANS calculations performed in channels with cross-pins disposition such as in a typical trailing edge of a gas turbine blade are shown. 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. Two computational domains have been considered: they both consist in a wedge shaped channel with a stream-wise normal pin fin or pedestal arrays. The aim of the numerical analysis is the evaluation of convective Heat Transfer Coefficient (HTC) on the planar bottom surface of the wedge-shaped duct: this surface is commonly named “endwall” surface. Detailed analysis of the flow field points out the coexistence of an horse-shoe vortex, a stagnant wake behind the pin and a mean flow acceleration due to convergent shape of the channel. Calculations reveal the presence of a weak jet-like flow field toward endwall surfaces caused by the strong recirculation behind each pin.

The effect of single-sided ribs on heat transfer and pressure drop within a trailing edge internal channel of a gas turbine blade

2021 ◽  
pp. 1-43
Author(s):  
Suhyun Kim ◽  
Seungwon Suh ◽  
Seungchan Baek ◽  
Wontae Hwang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Secondary Flow ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Sharp Corner ◽  
Trailing Edge ◽  
Edge Channel ◽  
Ribbed Channel

Abstract Convective cooling in a gas turbine blade internal trailing edge channel is often insufficient at the sharp trailing edge. This study examines convective heat transfer and pressure drop within a simplified trailing edge channel. The internal passage has been modeled as a right triangular channel with a 9° angle sharp corner. Smooth baseline and ribbed copper plates were heated from underneath via a uniform heat flux heater and examined via infrared thermography. Non-uniformity in the heat flux due to conduction is corrected by a RANS conjugate heat transfer calculation, which was validated by the mean velocity, friction factor, and temperature fields from experiments and LES simulations. Nusselt number distributions illustrate that surface heat transfer is increased considerably with ribs, and coupled with the vortices in the flow. Heat transfer at the sharp corner is increased by more than twofold due to ribs placed at the center of the channel, due to secondary flow. The present partially ribbed channel utilizes secondary flow toward the corner, and is presumed to have better thermal performance than a fully ribbed channel. Thus, it is important to set the appropriate rib length within the channel.

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.

Effect of Rotation on a Gas Turbine Blade Internal Cooling System: Numerical Investigation

2016 ◽  
Author(s):  
E. Burberi ◽  
D. Massini ◽  
L. Cocchi ◽  
L. Mazzei ◽  
A. Andreini ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Flow Field ◽  
Transfer Coefficient ◽  
Numerical Investigation ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Cooling System ◽  
Leading Edge ◽  
Internal Cooling

Increasing turbine inlet temperature is one of the main strategies used to accomplish the demands of increased performance of modern gas turbines. As a consequence, optimization of the cooling system is of paramount importance in gas turbine development. Leading edge represents a critical part of cooled nozzles and blades, given the presence of the hot gases stagnation point and the unfavourable geometry for cooling. This paper reports the results of a numerical investigation aimed at assessing the rotation effects on the heat transfer distribution in a realistic leading edge internal cooling system of a high pressure gas turbine blade. The numerical investigation was carried out in order to support and to allow an in-depth understanding of the results obtained in a parallel experimental campaign. The model is composed of a trapezoidal feeding channel which provides air to the cold bridge system by means of three large racetrack-shaped holes, generating coolant impingement on the internal concave leading edge surface, whereas four big fins assure the jets confinement. Air is then extracted through 4 rows of 6 holes reproducing the external cooling system composed of shower-head and film cooling holes. Experiments were performed in static and rotating conditions replicating the typical range of jet Reynolds number (Rej) from 10000 to 40000 and Rotation number (Roj) up to 0.05, for three crossflow cases representative of the working condition that can be found at blade tip, midspan and hub, respectively. Experimental results in terms of flow field measurements on several internal planes and heat transfer coefficient on the LE internal surface have been performed on two analogous experimental campaigns at University of Udine and University of Florence respectively. Hybrid RANS-LES models were used for the simulations, such as Scale Adaptive Simulation (SAS) and Detached Eddy Simulation (DES), given their ability to resolve the complex flow field associated with jet impingement. Numerical flow field results are reported in terms of both jet velocity profiles and 2D vector plots on symmetry and transversal internal planes, while the heat transfer coefficient distributions are presented as detailed 2D maps together with radial and tangential averaged Nusselt number profiles. A fairly good agreement with experimental measurements is observed, which represent a validation of the adopted computational model. As a consequence, the computed aerodynamic and thermal fields also allow an in-depth interpretation of the experimental results.

Numerical Studies on Effect of Channel Orientation in a Rotating Smooth Wedge-Shaped Cooling Channel

2014 ◽  
Author(s):  
Balamurugan Srinivasan ◽  
Anand Dhamarla ◽  
Chandiran Jayamurugan ◽  
Amarnath Balu Rajan
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Cooling Channel ◽  
Transfer Enhancement ◽  
Trailing Edge ◽  
Pin Fins ◽  
Channel Orientation ◽  
The Heat Transfer Coefficient

The increasing demands of better efficiency of modern advanced gas turbine require higher turbine inlet temperatures, which gives great challenges to turbine blade designers. However, the temperature limits of turbine blade material are not high enough to ensure its survival in such incredible operating temperature. Hence, both internal and external cooling approaches have been developed and widely used in today’s turbine blade. To internal cooling problems, a variety of cooling enhancement approaches, such as impingement and turbulators, are employed in order to meet the different needs in leading, middle and trailing region. One of the most critical parts in turbine blade is trailing edge where it is hard to cool due to its narrow shape. Pin-fins are widely used to cool the trailing edge of rotor and stator blades of gas turbine engine. Pin-fins offer significant heat transfer enhancement, they are relatively easy to fabricate and offer structural support to the hollow trailing edge region. The flow physics in a pin-fin roughened channel is very complicated and three-dimensional. In this work, we have studied the effect of channel orientation on heat transfer in a rotating wedge-shaped cooling channel using numerical methods. Qiu [1] studied experimentally heat transfer effects of 5 different angles of wedge shaped channel orientation for the inlet Reynolds number (5100 to 21000) and rotational speed (zero to 1000 rpm), which results in the inlet Rotation number variation from 0 to 0.68. They observed that compared to the non-rotating condition, there is about 35% overall heat transfer enhancement under highest rotation number. The above said results are validated using current studies with Computational Fluid Dynamics (CFD) revealed that rotation increases significantly the heat transfer coefficient on the trailing surface and reduces the heat transfer coefficient on the leading surface. This is due to the higher velocities associated with the converging geometry near trailing surface.

scholarly journals Validation and Analysis of Numerical Results for a Two-Pass Trapezoidal Channel With Different Cooling Configurations of Trailing Edge

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
Waseem Siddique ◽  
Lamyaa El-Gabry ◽  
Igor V. Shevchuk ◽  
Torsten H. Fransson
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Secondary Flow ◽  
Gas Turbine ◽  
Bottom Surface ◽  
Trailing Edge ◽  
Enhancement Of Heat Transfer ◽  
Trapezoidal Channel ◽  
Ribbed Channel ◽  
Edge Surface

High inlet temperatures in a gas turbine lead to an increase in the thermal efficiency of the gas turbine. This results in the requirement of cooling of gas turbine blades/vanes. Internal cooling of the gas turbine blade/vanes with the help of two-pass channels is one of the effective methods to reduce the metal temperatures. In particular, the trailing edge of a turbine vane is a critical area, where effective cooling is required. The trailing edge can be modeled as a trapezoidal channel. This paper describes the numerical validation of the heat transfer and pressure drop in a trapezoidal channel with and without orthogonal ribs at the bottom surface. A new concept of ribbed trailing edge has been introduced in this paper which presents a numerical study of several trailing edge cooling configurations based on the placement of ribs at different walls. The baseline geometries are two-pass trapezoidal channels with and without orthogonal ribs at the bottom surface of the channel. Ribs induce secondary flow which results in enhancement of heat transfer; therefore, for enhancement of heat transfer at the trailing edge, ribs are placed at the trailing edge surface in three different configurations: first without ribs at the bottom surface, then ribs at the trailing edge surface in-line with the ribs at the bottom surface, and finally staggered ribs. Heat transfer and pressure drop is calculated at Reynolds number equal to 9400 for all configurations. Different turbulent models are used for the validation of the numerical results. For the smooth channel low-Re k-ɛ model, realizable k-ɛ model, the RNG k-ω model, low-Re k-ω model, and SST k-ω models are compared, whereas for ribbed channel, low-Re k-ɛ model and SST k-ω models are compared. The results show that the low-Re k-ɛ model, which predicts the heat transfer in outlet pass of the smooth channels with difference of +7%, underpredicts the heat transfer by −17% in case of ribbed channel compared to experimental data. Using the same turbulence model shows that the height of ribs used in the study is not suitable for inducing secondary flow. Also, the orthogonal rib does not strengthen the secondary flow rotational momentum. The comparison between the new designs for trailing edge shows that if pressure drop is acceptable, staggered arrangement is suitable for the outlet pass heat transfer. For the trailing edge wall, the thermal performance for the ribbed trailing edge only was found about 8% better than other configurations.

Unsteady CFD Analysis of Turbulent Flow and Heat Transfer in a Gas Turbine Blade Trailing Edge Subjected to Rotation

2012 ◽  
Author(s):  
Domenico Borello ◽  
Giovanni Delibra ◽  
Cosimo Bianchini ◽  
Antonio Andreini
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Heated Surface ◽  
Heat Removal ◽  
Gas Turbine Blade ◽  
Trailing Edge ◽  
Flow And Heat Transfer ◽  
The Impact

Internal cooling of gas turbine blade represents a challenging task involving several different phenomena as, among others, highly three-dimensional unsteady fluid flow, efficient heat transfer and structural design. This paper focuses on the analysis of the turbulent flow and heat transfer inside a typical wedge–shaped trailing edge cooling duct of a gas turbine blade. In the configuration under scrutiny the coolant flows inside the duct in radial direction and it leaves the blade through the trailing edge after a 90 deg turning. At first an analysis of the flow and thermal fields in stationary conditions was carried out. Then the effects of rotational motion were investigated for a rotation number of 0.275. The rotation axis here considered is normal to the inflow and outflow bulk velocity, representing schematically a highly loaded blade configuration. The work aimed to i) analyse the dynamic of the vortical structures under the influence of strong body forces and the constraints induced by the internal geometry and ii) to study the impact of such motions on the mechanisms of heat removal. The final aim was to verify the design of the equipment and to detect the possible presence of regions subjected to high thermal loads. The analysis is carried out using the well assessed open source code OpenFOAM written in C++ and widely validated by several scientists and researchers around the world. The unsteadiness of the flow inside the trailing edge required to adopt models that accurately reconstructed the flow field. As the computational costs associated to LES (especially in the near wall regions) largely exceed the available resources, we chose for the simulation the SAS model of Menter, that was validated in a series of benchmark and industrially relevant test cases and allowed to reconstruct a part of the turbulence spectra through a scale-adaptive mechanism. Assessment of the obtained results with steady-state k-ω SST computations and available experimental results was carried out. The present analysis demonstrated that a strong unsteadiness develops inside the trailing edge and that the rotation generated strong secondary motions that enhanced the dynamic of heat removal, leading to a less severe temperature distribution on the heated surface w.r.t the non rotating case.

Detailed Studies on the Flow Field and Heat Transfer Characteristics Inside a Realistic Serpentine Cooling Channel With a S-Shaped Inlet

2018 ◽  
Author(s):  
Ken-ichi Funazaki ◽  
Hikaru Odagiri ◽  
Takeshi Horiuchi ◽  
Masahide Kazari
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Flow Visualization ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Cooling Channel ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Inner Surface

Accurate temperature prediction of turbine blades for gas turbine is very important to assure the life-span of the blade under a hostile hot gas environment and intense centrifugal force. Therefore, there have been a number of studies carried out to clarify the cooling performance of serpentine cooling channel inside a turbine blade for gas turbine, however, it remains to be quite difficult to make an accurate numerical prediction of the performance. Apart from the effects of disk rotation as well as large temperature gradient near the wall, such a poor predictability can be attributed to the complicated vortical motions caused by the rib-roughened cooling channel whose cross-sectional shape varies along the channel and by the existence of u-bends. Furthermore, since the cooling channel inside a real turbine blade usually has a curved or S-shaped inlet, which may induce flow separation as well as swirl developed in the inlet, it can be imagined that the flow and heat transfer inside the cooling channel is likely to become much more complicated than that with a straight inlet. Despite this situation, only few studies are made in order to examine the flow and heat transfer characteristics inside the cooling channel with s-shaped inlet. Accordingly, this study aims at detailed experimental and numerical investigations on the flow and heat transfer characteristics of a realistic serpentine rib-roughened cooling channel with an s-shaped inlet, which is modeled from an actual HP turbine blade for gas turbine. This study employs a transient TLC (Thermochromic Liquid Crystal) technique to measure the heat transfer characteristics, along with the flow visualization on the inner surface of the channel using oil mixed with titanium powder. Note that a special focus in this flow visualization is placed on the area of s-shaped inlet. As for the flow measurement, 2D-PIV (Particle Image Velocimetry) method is used to understand time-dependent vortical structures of the flow field that can have significant impacts on the heat transfer. RANS-based numerical simulation is also executed to predict the heat transfer distribution on the inner surface of the cooling channel.

Numerical Investigation of Flow and Heat Transfer in Gas Turbine Serpentine Passage Cooling and Comparison With Experimental Data

2013 ◽  
Author(s):  
S. Kathiravan ◽  
Roberto De Prosperis ◽  
Alessandro Ciani
Keyword(s):  
Heat Transfer ◽  
Secondary Flow ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Physical Phenomenon ◽  
Flow Path ◽  
Heat Transfer Analysis ◽  
Gas Turbine Blade ◽  
Cooling Flow ◽  
The Impact

Due to recent advancements made in computational technology, CFD tools are capable of accurately capturing complex physical phenomenon. The proposed novel CFD methodology improves the prediction reliability and capability of Gas Turbine Blade heat transfer and secondary flow behaviour. This paper discusses a robust CFD based methodology to validate the complex gas turbine blade cooling design using detailed 3D flow & conjugate heat transfer analysis. Both primary and secondary flow domains along with blade metal are considered in one single integrated CFD model. This will capture the coupled heat transfer and tip vortices mixing effects and hence accurately predict the secondary cooling flow. The secondary flow path geometry consists of serpentine passages with turbulator features in the flow path to improve the effective heat transfer. Several sensitivity studies were performed using the above model to understand the impact of turbulator fillets, tip hole coating thickness, domain interface and suitably accounted for in the full scale simulation. The numerical simulation results were extensively validated with GE industrial Frame5 gas turbine prototype test thermocouple data and thermal profiles (span-wise) obtained from metallographic images. This novel method gives a thorough understanding of flow-thermal physics involved in serpentine cooling and helps to optimize effective cooling flow usage.

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