Rotating Heat Transfer Measurements on a Multi-Pass Internal Cooling Channel: II — Experimental Tests

2016 ◽  
Author(s):  
Fabio Pagnacco ◽  
Luca Furlani ◽  
Alessandro Armellini ◽  
Luca Casarsa ◽  
Anthony Davis
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Rotation Axis ◽  
Internal Cooling ◽  
Test Model ◽  
Transfer Coefficients ◽  
Present Contribution ◽  
The Real ◽  
The Third ◽  
Ribbed Channel

The present contribution is focused on heat transfer measurements on internal cooling channels of a high pressure gas turbine blade in static and rotating conditions. A novel rig designed for the specific purpose was used to assess the heat transfer coefficients on a full internal cooling scheme of an idealized blade. The channel has a multi-pass design. Coolant enters at the blade hub in the leading edge region and move radially outwards inside a two-sided ribbed channel. The second passage is again a two-sided ribbed channel with a trapezoidal cross section of high aspect ratio, while inside the third leg low aspect-ratio cylindrical pin fins are arranged in a staggered configuration to promote flow turbulence. Inside the third passage, the coolant is progressively discharged at the blade trailing edge and finally at the blade tip. The test model differs with respect to the real design only because there is no curvature due to the blade camber. Conversely, the correct stagger angle of the real blade with respect to the rotation axis is preserved. Experiments were performed for static and rotating conditions with engine similar conditions of Re=21000 and Ro=0.074, both defined at the channel inlet. Transient liquid crystal technique was used for the measurement of the heat transfer coefficient (HTC) on both pressure and suction sides internal surfaces of the channel. From the spatially resolved HTC maps available, it is possible to characterize the thermal performances of the whole passage and to highlight the effect of rotation.

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.

Heat Transfer in Rotating Multipass Rectangular Ribbed Channel With and Without a Turning Vane

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Jiang Lei ◽  
Shiou-Jiuan Li ◽  
Je-Chin Han ◽  
Luzeng Zhang ◽  
Hee-Koo Moon
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Aspect Ratio ◽  
Rectangular Channel ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
The Third ◽  
Ribbed Channel ◽  
Rotation Numbers ◽  
Turn Region

This paper experimentally investigates the effect of a turning vane in hub region on heat transfer in a multipass rectangular channel with rib-roughed wall at high rotation numbers. The experimental data were taken in the second and the third passages (aspect ratio = 2:1) connected by an 180 deg U-bend. The flow was radial inward in the second passage and was radial outward after the 180 deg U-bend in the third passage. The square-edged ribs with P/e = 8, e/Dh = 0.1, and α = 45 deg were applied on the leading and trailing surfaces of the second and the third passages. Results showed that rotation increases heat transfer on the leading surface but decreases it on the trailing surface in the second passage. In the third passage, rotation decreases heat transfer on the leading surface but increases it on the trailing surface. Without a turning vane, rotation reduces heat transfer on the trailing surface and increases it on the leading surface in the hub 180 deg turn region. After adding a half-circle-shaped turning vane, heat transfer coefficients do not change in the second passage before-turn while they are different in the turn region and after-turn region in the third passage. Regional heat transfer coefficients are correlated with rotation numbers for multipass rectangular ribbed channel with and without a turning vane.

Heat Transfer Measurements in an Internal Cooling System Using a Transient Technique With Infrared Thermography

2012 ◽  
Author(s):  
Christian Egger ◽  
Jens von Wolfersdorf ◽  
Martin Schnieder
Keyword(s):  
Heat Transfer ◽  
Data Analysis ◽  
Infrared Thermography ◽  
Outer Surface ◽  
Cooling System ◽  
Internal Cooling ◽  
Test Model ◽  
Cooling Channel ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

In this paper a transient method for measuring heat transfer coefficients in internal cooling systems using infrared thermography is applied. The experiments are performed with a two-pass internal cooling channel connected by a 180° bend. The leading edge and the trailing edge consist of trapezoidal and nearly rectangular cross sections, respectively, to achieve an engine-similar configuration. Within the channels rib arrangements are considered for heat transfer enhancement. The test model is made of metallic material. During the experiment the cooling channels are heated by the internal flow. The surface temperature response of the cooling channel walls is measured on the outer surface by infrared thermography. Additionally, fluid temperatures as well as fluid and solid properties are determined for the data analysis. The method for determining the distribution of internal heat transfer coefficients is based on a lumped capacitance approach which considers lateral conduction in the cooling system walls as well as natural convection and radiation heat transfer on the outer surface. Because of time-dependent effects a sensitivity analysis is performed to identify optimal time periods for data analysis. Results are compared with available literature data.

Heat Transfer in Rotating Multi-Pass Rectangular Ribbed Channel With and Without a Turning Vane

2012 ◽  
Author(s):  
Jiang Lei ◽  
Shiou-Jiuan Li ◽  
Je-Chin Han ◽  
Luzeng Zhang ◽  
Hee-Koo Moon
Keyword(s):  
Heat Transfer ◽  
Rectangular Channel ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
The Third ◽  
Ribbed Channel ◽  
Rotation Numbers ◽  
Loss Coefficients ◽  
Channel Loss ◽  
Turn Region

This paper experimentally investigates the effect of turning vane on hub region heat transfer in a multi-pass rectangular channel with rib-roughed wall at high rotation numbers. The experimental data were taken in the second and the third passages (Aspect Ratio = 2:1) connected by 180° U-bend. The flow was radial inward in the second passage and was radial outward after the 180° U-bend in the third passage. The square-edged ribs with P/e = 8, e/Dh = 0.1, and α = 45° were applied on the leading and trailing surfaces of the second and third passages. Results showed that rotation increases heat transfer on the leading surface but decreases it on the trailing surface in the second passage. In the third passage, rotation decreases heat transfer on the leading surface but increases it on the trailing surface. Without a turning vane, rotation reduces heat transfer on the trailing surface and increases it on the leading surface in the hub 180° turn region. After adding a half-circle-shaped turning vane, heat transfer coefficients do not change in the second passage before-turn while they are different in the turn region and after-turn region in the third passage. Regional heat transfer coefficients and channel loss coefficients are correlated with rotation numbers for multi-pass rectangular ribbed channel with and without a turning vane.

Heat Transfer and Pressure Drop Measurements in a High Aspect Ratio Channel With Circular Pins and Strip Fins

2019 ◽  
Vol 12 (3) ◽  
Author(s):  
Metapun Nuntakulamarat ◽  
Chao-Cheng Shiau ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Aspect Ratio ◽  
Heat Transfer Enhancement ◽  
High Aspect Ratio ◽  
Thickness Effect ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
Transfer Coefficients ◽  
Pin Fin

Abstract This paper focuses on the measurements of heat transfer enhancement and pressure drop of different pin or fin configurations in a high aspect ratio (AR = 9.57/1.2) channel. Two different pin-fin shapes including circular pins and strip fins were studied. Different pin-fin spacings for circular pins (S/D = 2, 4) and strip fins (S/W = 8, 16) were investigated, respectively. In addition, the thickness effect of the strip fin was included in this study. The regionally averaged heat transfer measurement method was used to acquire the heat transfer coefficients on two opposite featured surfaces within the test channel. For each configuration, the tested Reynolds number was ranging from 20,000 to 80,000. The results indicate that the channel with circular pins has better heat transfer enhancement and higher pressure loss than their strip fins counterparts. However, the strip fins are considered better designs in terms of thermal performance. For the gas turbine designers aim at developing an improved internal cooling feature, this work demonstrates the great potential of the strip fins as a novel and effective cooling design compared with the conventional circular pins.

Rotating Heat Transfer Measurements on a Multi-Pass Internal Cooling Channel: I — Rig Development

2016 ◽  
Author(s):  
Fabio Pagnacco ◽  
Luca Furlani ◽  
Alessandro Armellini ◽  
Luca Casarsa ◽  
Anthony Davis
Keyword(s):  
Heat Transfer ◽  
Turbine Blades ◽  
Cold Temperature ◽  
Internal Cooling ◽  
Test Model ◽  
Temperature Step ◽  
Present Contribution ◽  
Gas Turbine Blades ◽  
Spatially Resolved ◽  
Main Components

The present contribution describes the design and realization of a rotating test rig for heat transfer measurements on internal cooling passages of gas turbine blades. The aim is to study the effects of Coriolis and buoyancy forces on the heat transfer distribution inside realistic cooling schemes. Spatially resolved heat transfer data are obtained by means of transient thermochromic liquid crystals (TLC) technique. In order to replicate the same buoyancy effects induced by the Coriolis forces during rotation, the transient measurements are performed with a cold temperature step on the coolant flow. New solutions are adopted to generate the cold temperature step, acquire the experimental data on board of the rotating test model and to control the experimental parameters during tests execution. The main components of the rig will be described in the paper, together with an overview of the data processing methodology that has been developed.

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.

Heat Transfer Measurements in an Internal Cooling System Using a Transient Technique With Infrared Thermography

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Christian Egger ◽  
Jens von Wolfersdorf ◽  
Martin Schnieder
Keyword(s):  
Heat Transfer ◽  
Data Analysis ◽  
Infrared Thermography ◽  
Outer Surface ◽  
Cooling System ◽  
Internal Cooling ◽  
Test Model ◽  
Cooling Channel ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

In this paper, a transient method for measuring heat transfer coefficients in internal cooling systems using infrared thermography is applied. The experiments are performed with a two-pass internal cooling channel connected by a 180 deg bend. The leading edge and the trailing edge consist of trapezoidal and nearly rectangular cross-sections, respectively, to achieve an engine-similar configuration. Within the channels, rib arrangements are considered for heat transfer enhancement. The test model is made of metallic material. During the experiment, the cooling channels are heated by the internal flow. The surface temperature response of the cooling channel walls is measured on the outer surface by infrared thermography. Additionally, fluid temperatures as well as fluid and solid properties are determined for the data analysis. The method for determining the distribution of internal heat transfer coefficients is based on a lumped capacitance approach, which considers lateral conduction in the cooling system walls as well as natural convection and radiation heat transfer on the outer surface. Because of time-dependent effects, a sensitivity analysis is performed to identify optimal time periods for data analysis. Results are compared with available literature data.

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 Heat Transfer From Low Aspect Ratio Pin Fins

2007 ◽  
Author(s):  
Michael E. Lyall ◽  
Alan A. Thrift ◽  
Atul Kohli ◽  
Karen A. Thole
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Gas Turbines ◽  
Channel Height ◽  
Internal Cooling ◽  
Number Range ◽  
Pin Fin ◽  
Heat Transfer Augmentation ◽  
Low Aspect Ratio ◽  
Pin Fins

The performance of many engineering devices from power electronics to gas turbines is limited by thermal management. Heat transfer augmentation in internal flows is commonly achieved through the use of pin fins, which increase both surface area and turbulence. The present research is focused on internal cooling of turbine airfoils using a single row of circular pin fins that is oriented perpendicular to the flow. Low aspect ratio pin fins were studied whereby the channel height to pin diameter was unity. A number of spanwise spacings were investigated for a Reynolds number range between 5000 to 30,000. Both pressure drop and spatially-resolved heat transfer measurements were taken. The heat transfer measurements were made on the endwall of the pin fin array using infrared thermography and on the pin surface using discrete thermocouples. The results show that the heat transfer augmentation relative to open channel flow is the highest for smallest spanwise spacings and lowest Reynolds numbers. The results also indicate that the pin fin heat transfer is higher than the endwall heat transfer.

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