Effect of Aspect Ratio on Heat Transfer of Triangular Internal Cooling Channel of Gas Turbine Blade

2021 ◽  
Vol 45 (3) ◽  
pp. 135-143
Author(s):  
Seok Min Choi ◽  
Seungyeong Choi ◽  
Hee Seung Park ◽  
Hyung Hee Cho
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Gas Turbine Blade

Study On Flow and Heat Transfer Characteristics of a New-Proposed Alternating Elliptical U-Channel in the Mid-Chord Region of Gas Turbine Blade

2021 ◽  
Author(s):  
Kun Xiao ◽  
Juan He ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Thermal Performance ◽  
Cooling Channel ◽  
Gas Turbine Blade ◽  
Heat Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Bend Channel

Abstract This paper proposed an alternating elliptical U-bend cooling channel which can be applied in the mid-chord region of gas turbine blade and manufactured by precision casting, based on the optimal flow field structure deduced from the Field Synergy Principle, and investigated the flow and heat transfer characteristics in this alternating elliptical U-bend cooling channel thoroughly. Numerical simulations were performed by using 3D steady solver of Reynolds-averaged Navier-Stokes equations (RANS) with the standard k-e turbulence model. The influence of alternating of cross section on heat transfer and pressure drop of the channel was studied by comparing with the smooth elliptical U-bend channel. On this basis, the effect of aspect ratio (length ratio of the major axis to the minor axis) and alternating angle were further investigated. The results showed that, in the first pass of the alternating elliptical U-bend channel, for different Re, four or eight longitudinal vortices were generated. In the second pass, the alternating elliptical channel restrained the flow separation to a certain extent and a double-vortex structure was formed. The average Nusselt number of the alternating elliptical U-bend channel was significantly higher than that of the straight channel, but the pressure loss only increased slightly. With the increase of aspect ratio, the thermal performance of the channel increased, and when the alternating angle is between 40° and 90°, the thermal performance nearly kept constant and also the best.

Experimental Study on Flow Behavior and Heat Transfer Enhancement with Distinct Dimpled Gas Turbine Blade Internal Cooling Channel

2021 ◽  
pp. 1-28
Author(s):  
Farah Nazifa Nourin ◽  
Ryoichi S. Amano
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Thermal Performance ◽  
Diameter Ratio ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Transfer Enhancement

Abstract The study presents the investigation on heat transfer distribution along a gas turbine blade internal cooling channel. Six different cases were considered in this study, using the smooth surface channel as a baseline. Three different dimples depth-to-diameter ratios with 0.1, 0.25, and 0.50 were considered. Different combinations of partial spherical and leaf dimples were also studied with the Reynolds numbers of 6,000, 20,000, 30,000, 40,000, and 50,000. In addition to the experimental investigation, the numerical study was conducted using Large Eddy Simulation (LES) to validate the data. It was found that the highest depth-to-diameter ratio showed the highest heat transfer rate. However, there is a penalty for increased pressure drop. The highest pressure drop affects the overall thermal performance of the cooling channel. The results showed that the leaf dimpled surface is the best cooling channel based on the highest Reynolds number's heat transfer enhancement and friction factor. However, at the lowest Reynolds number, partial spherical dimples with a 0.25 depth to diameter ratio showed the highest thermal performance.

Detailed Local Heat Transfer Measurements in a Model of a Dendritic Gas Turbine Blade Cooling Design

2011 ◽  
Author(s):  
James Batstone ◽  
David Gillespie ◽  
Eduardo Romero
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Large Scale ◽  
Surface Film ◽  
Internal Heat ◽  
Internal Cooling ◽  
Gas Turbine Blade ◽  
Lift Off ◽  
Number Of Branches

A novel form of gas turbine blade or vane cooling in which passages repeatedly branch within the wall of the cooled component is introduced in this paper. These so called dendritic cooling geometries offer particular performance improvements compared to traditional cooling holes where the external cross flow is low, and conventional films have a tendency to lift off the surface. In these regions improved internal cooling efficiency is achieved, while the coolant film is ejected at a low momentum ratio resulting in reduced aerodynamic losses between the film and hot gases, and a more effective surface film. By varying the number of branches of the systems at a particular location it is possible to tune the flow and heat transfer to the requirements at that location whilst maintaining the pressure margin. The additional loss introduced using the internal branching structure allows a full film-coverage arrangement of holes at the external blade surface. In this paper the results of transient heat transfer experiments characterising the internal heat transfer coefficient distribution in large scale models of dendritic passages are reported. Experiments were conducted with 1, 2 and 3 internal flow branches at a range of engine representative Reynolds numbers and exit momentum ratios. CFD models are used to help explain the flow field in the cooling passages. Furthermore the sensitivity of the pressure loss to the blowing ratio at the exit of the cooling holes is characterised and found to be inversely proportional to the number of branches in the dendritic system. Surprisingly the highly branched systems generally do not exhibit the highest pressure losses.

Heat Transfer in a Rotating, Blade-Shaped, Two-Pass Cooling Channel With a Variable Aspect Ratio

2021 ◽  
Author(s):  
I-Lun Chen ◽  
Izzet Sahin ◽  
Lesley M. Wright ◽  
Je-Chin Han ◽  
Robert Krewinkel
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Gas Turbine ◽  
Cross Section ◽  
Pressure Loss ◽  
Planar Geometry ◽  
Internal Cooling ◽  
Cooling Channel ◽  
First Passage ◽  
Rotating Blade

Abstract This study features a rotating, blade-shaped, two-pass cooling channel with a variable aspect ratio. Internal cooling passages of modern gas turbine blades closely follow the shape and contour of the airfoils. Therefore, the cross-section and the orientation with respect to rotation varies for each cooling channel. The effect of passage orientation on the heat transfer and pressure loss is investigated by comparing to a planar channel design with a similar geometry. Following the blade cross-section, the first pass of the serpentine channel is angled at 50° from the direction of rotation while the second pass has an orientation angle of 105°. The coolant flows radially outward in the first passage with an aspect ratio (AR) = 4:1. After a 180-degree tip turn, the coolant travels radially inward into the second passage with AR = 2:1. The copper plate method is applied to obtain the regionally-averaged heat transfer coefficients on all the interior walls of the cooling channel. In addition to the smooth surface case, 45° angled ribs with a profiled cross section are also placed on the leading and trailing surfaces in both the passages. The ribs are placed such that P/e = 10 and e/H = 0.16. The Reynolds number varies from 10,000 to 45,000 in the first passage and 16,000 to 73,000 in the second passage. The rotational speed ranges from 0 to 400 rpm, which corresponds to maximum rotation numbers of 0.38 and 0.15 in the first and second passes, respectively. The blade-shaped feature affects the heat transfer and pressure loss in the cooling channels. In the second passage, the heat transfer on the outer wall and trailing surface is higher than the inner wall and leading surface due to flow impingement and the swirling motion induced by the blade-shaped tip turn. The rotational effect on the heat transfer and pressure loss is lower in the blade-shaped design than the planar design due to the feature of angled rotation. The tip wall heat transfer is significantly enhanced by rotation in this study. The overall heat transfer and pressure loss in this study is higher than the planar geometry due to the blade-shaped feature. The heat transfer and pressure loss characteristics from this study provide important information for the gas turbine blade internal cooling designs.

Numerical Investigation on the Modified Bend Geometry of a Rotating Multipass Internal Cooling Passage in a Gas Turbine Blade

2018 ◽  
Vol 10 (6) ◽  
Author(s):  
Naris Pattanaprates ◽  
Ekachai Juntasaro ◽  
Varangrat Juntasaro
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Internal Cooling ◽  
Gas Turbine Blade ◽  
Reduced Pressure ◽  
Improve Heat Transfer ◽  
Cooling Passage ◽  
Internal Cooling Passage

Abstract The present work is aimed to investigate whether the modification to the bend geometry of a multipass internal cooling passage in a gas turbine blade can enhance heat transfer and reduce pressure drop. The two-pass channel and the four-pass channel are modified at the bend from the U shape to the bulb and bow shape. The first objective of the work is to investigate whether the modified design will still improve heat transfer with reduced pressure drop in a four-pass channel as in the case of a two-pass channel. It is found out that, unlike the two-pass channel, the heat transfer is not improved but the pressure drop is still reduced for the four-pass channel. The second objective is to investigate the rotating effect on heat transfer and pressure drop in the cases of two-pass and four-pass channels for both original and modified designs. It is found out that heat transfer is improved with reduced pressure drop for all cases. However, the modified design results in the less improvement on heat transfer and lower reduced pressure drop as the rotation number increases. It can be concluded from the present work that the modification can solve the problem of pressure drop without causing the degradation of heat transfer for all cases. The two-pass channel with modified bend results in the highest heat transfer and the lowest pressure drop for rotating cases.

Flow structure and heat exchange analysis in internal cooling channel of gas turbine blade

2016 ◽  
Vol 25 (4) ◽  
pp. 336-341 ◽  
Author(s):  
Ryszard Szwaba ◽  
Piotr Kaczynski ◽  
Piotr Doerffer ◽  
Janusz Telega
Keyword(s):  
Heat Exchange ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Flow Structure ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Gas Turbine Blade
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