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.

Heat Transfer in a Rib and Pin Roughened Rotating Multipass Channel With Hub Turning Vane and Trailing-Edge Slot Ejection

2017 ◽  
Vol 10 (2) ◽  
Author(s):  
Hao-Wei Wu ◽  
Hootan Zirakzadeh ◽  
Je-Chin Han ◽  
Luzeng Zhang ◽  
Hee-Koo Moon
Keyword(s):  
Heat Transfer ◽  
Orientation Angle ◽  
Side Wall ◽  
Internal Cooling ◽  
Test Model ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Pin Fin ◽  
Pin Fins ◽  
Cooling Air

A multipassage internal cooling test model with a 180 deg U-bend at the hub was investigated. The flow is radially inward at the inlet passage while it is radially outward at the trailing edge passage. The aspect ratio (AR) of the inlet passage is 2:1 (AR = 2) while the trailing edge passage is wedge-shaped with side wall slot ejections. The squared ribs with P/e = 8, e/Dh = 0.1, α = 45 deg, were configured on both leading surface (LE) and trailing surface (TR) along the inlet passage, and also at the inner half of the trailing edge passage. Three rows of cylinder-shaped pin fins with a diameter of 3 mm were placed at both LE and TR at the outer half of the trailing edge passage. For without turning vane case, heat transfer on LE at hub turn region is increased by rotation while it is decreased on the TR. The presence of turning vane reduces the effect of rotation on hub turn portion. The combination of ribs, pin-fin array, and mass loss of cooling air through side wall slot ejection results in the heat transfer coefficient gradually decreased along the trailing edge passage. Correlation between regional heat transfer coefficients and rotation numbers is presented for with and without turning vane cases, and with channel orientation angle β at 90 deg and 45 deg.

APPLICATION OF SCALE ADAPTIVE SIMULATION MODEL TO STUDYING COOLING CHARACTERISTICS OF A HIGH PRESSURE TURBINE BLADE CUTBACK TRAILING EDGE WITH DIFFERENT COOLING CONFIGURATIONS

2021 ◽  
pp. 1-53
Author(s):  
Yuefeng Li ◽  
Huazhao Xu ◽  
Jianhua Wang ◽  
Wei Song ◽  
Ming Wang ◽  
...  
Keyword(s):  
High Pressure ◽  
High Pressure Turbine ◽  
Baseline Model ◽  
Trailing Edge ◽  
Cooling Effectiveness ◽  
Adaptive Simulation ◽  
Rear Part ◽  
Pin Fins ◽  
A Minor ◽  
Better Than

Abstract This paper adopted Scale Adaptive Simulation (SAS) to investigate fluid flow and cooling characteristics in detail downstream of a high pressure turbine (HPT) blade trailing edge (TE) cutback region. The effects of typical TE configurations on cutback cooling performance are investigated including three types of internal turbulators, the cutback with/without land extensions and three kinds of ejection lip profiles. The elliptic pin fins with streamwise orientation significantly improve ηaw at the rear part of the cutback surface over the baseline model with cylindrical pin fins and slightly increase Cd. However, the elliptic pin fins with spanwise orientation drastically reduce the ηaw and Cd. Downstream of the cutback, the coherent structures are strongly disturbed and become chaotic compared to the TE with cylindrical and streamwise oriented elliptic pin fins. The application of land extensions only causes an evident change to the coherent structure immediate downstream of the lip, and slightly improves ηaw and reduces Cd over the baseline model on the rear part of the cutback surface. Rounded lip shapes B and C also show an obvious increase in ηaw on the rear part of the cutback surface but only a minor increase in Cd compared to the straight lip shape A. The rounded lip helps the coolant diffuse into the TE cutback and reduce the intensity of mixing. Due to larger rounding radius of shape B, the cooling effectiveness predicted by shape B is slightly better than shape C.

Geometrical Modification of the Unsteady Pressure to Reduce Low-Pressure Turbine Flutter

2017 ◽  
Vol 139 (9) ◽  
Author(s):  
Christian Peeren ◽  
Konrad Vogeler
Keyword(s):  
Turbine Blade ◽  
Local Stability ◽  
Free Standing ◽  
Unsteady Pressure ◽  
Low Pressure Turbine ◽  
Physical Mechanisms ◽  
Local Modification ◽  
Blade Section ◽  
Turbine Design ◽  
The Impact

In this work, the impact of the airfoil shape on flutter is investigated. Flutter occurs when the blade structure is absorbing energy from its surrounding fluid leading to hazardous amplification of vibrations. The key for a more stable design is the local modification of the blade motion induces unsteady pressure, which is responsible for local stability. Especially for free-standing blades, where most exciting aerodynamic work transfer is found at the upper tip sections, a reshaping of the airfoil is expected to beneficially influence stability. Two approaches are pursued in this work. This first approach is based on flow physics considerations. The unsteady pressure field is decomposed into four physical mechanisms or effects and each effect investigated. The second approach is used to validate the conclusions made in the theoretical part by numerical optimizing the geometry of a representative turbine blade. Selected optimized designs are picked and compared with each other in terms of local stability, aerodynamics, and robustness with respect to the boundary conditions. Both approaches are applied for a freestanding and interlocked turbine blade section. The found design potential is discussed and the link to the differences mechanisms, introduced in the first part, established. Based on the observations made, design recommendations are made for a flutter-reduced turbine design.

Heat Transfer in a Rib and Pin Roughened Rotating Multi-Pass Channel With Hub Turning Vane and Trailing-Edge Slot Ejection

2015 ◽  
Author(s):  
Hao-Wei Wu ◽  
Hootan Zirakzadeh ◽  
Je-Chin Han ◽  
Luzeng Zhang ◽  
Hee-Koo Moon
Keyword(s):  
Heat Transfer ◽  
Side Wall ◽  
Internal Cooling ◽  
Test Model ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Heat Transfer Coefficients ◽  
The Third ◽  
Pin Fins ◽  
Cooling Air

A three-passage internal cooling test model with a 180° U-bend at the hub turn portion was used to perform the investigation. The flow is radially inward at the second passage, while it is radially outward at the third passage after the U-bend. Measurement was conducted at the second and the third passages. Aspect ratio of the second passage is 2:1 (AR=2), while the third passage is wedge-shaped with side wall slot ejections. The squared ribs with P/e = 8, e/Dh = 0.1, α = 45°, were configured on both leading and trailing surfaces along the second passage, and also the inner half of the third passage. Three rows of cylinder-shaped pin-fins with diameter of 3 mm were placed at both leading and trailing surfaces of the outer half of the third passage. The results showed that the rotating effects on radial inward flow and radial outward flow are consistent with previous studies. When there is no turning vane, heat transfer on the leading surface at hub turn region is increased by rotation, while it is decreased on the trailing surface. The presence of turning vane reduces the effect of rotation on hub turn portion. Ejection and pin-fin array enhance heat transfer at the third passage. Even though there is mass loss of cooling air along the third passage with side wall slot ejection, the heat transfer coefficient remains high until the end of the passage. Correlation between regional heat transfer coefficients and rotation numbers is presented for both cases of with and without turning vane.

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.

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 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 The Effect of Vortex Shedding on the Unsteady Pressure Distribution Around the Trailing Edge of a Turbine Blade

1996 ◽  
Author(s):  
G. Cicatelli ◽  
C. H. Sieverding
Keyword(s):  
Pressure Distribution ◽  
Turbine Blade ◽  
Large Scale ◽  
Guide Vane ◽  
Turbine Blades ◽  
Pressure Fluctuations ◽  
Flow Characteristics ◽  
Wake Flow ◽  
Trailing Edge ◽  
Unsteady Pressure

The wakes behind turbine blade trailing edge are characterized by large scale periodic vortex patterns known as the von Karman vortex street. The failure of steady-state Navier-Stokes calculations in modeling wake flows appears to be mainly due to ignoring this type of flow instabilities. In an effort to contribute to a better understanding of the time varying wake flow characteristics behind turbine blades, VKI has performed large scale turbine cascade tests to obtain very detailed information about the steady and unsteady pressure distribution around the trailing edge of a nozzle guide vane. Tests are run at an outlet Mach number of M2,is,=0.4 and a Reynolds number of Rec = 2·106. The key to the high spatial resolution of the pressure distribution around the trailing edge is a rotatable trailing edge with an embedded miniature pressure transducer underneath the surface and a pressure slot opening of about 1.5° of the trailing edge circle. Signal processing allowed or differentiation between random and periodic pressure fluctuations. Ultra-short schlieren pictures help in understanding the physics behind the pressure distribution.

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