Development and Application of an Internal Heat-Transfer Measurement Technique for Cooled Real Engine Components

2020 ◽  
Author(s):  
Asif Ali ◽  
Lorenzo Cocchi ◽  
Alessio Picchi ◽  
Bruno Facchini ◽  
Simone Cubeda
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Measurement Technique ◽  
Cooling System ◽  
Convective Heat Transfer Coefficient ◽  
Internal Heat ◽  
Test Duration ◽  
External Temperature ◽  
Ir Camera ◽  
Internal Heat Transfer

Abstract The aim of this work is to present the development and application of a measurement technique that allows to record internal heat transfer features of real components. In order to apply this method, based on similar approaches proposed in previous literature works, the component is initially heated up to a steady temperature, then a thermal transient is induced by injecting cool air in the internal cooling system. During this process, the external temperature evolution is recorded by means of an IR camera. Experimental data are then exploited to run a numerical procedure, based on a series of transient finite-element analyses of the component. In particular, the test duration is divided into an appropriate number of steps and, for each of them, the heat flux on internal surfaces is iteratively updated as to target the measured external temperature distribution. Heat flux and internal temperature data for all the time steps are eventually employed in order to evaluate the convective heat transfer coefficient via linear regression. This technique has been successfully tested on a cooled high-pressure vane of a Baker Hughes heavy-duty gas turbine, which was realised thanks to the development of a dedicated test rig at the University of Florence, Italy. The obtained results provide sufficiently detailed heat transfer distributions in addition to allowing to appreciate the effect of different coolant mass flow rates. The methodology is also capable of identifying defects, which is demonstrated by inducing controlled faults in the component.

Development and Application of an Internal Heat-transfer Measurement Technique for Cooled Real Engine Components

2021 ◽  
Author(s):  
Asif Ali ◽  
Lorenzo Cocchi ◽  
Alessio Picchi ◽  
Bruno Facchini ◽  
Simone Cubeda
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Measurement Technique ◽  
Cooling System ◽  
Convective Heat Transfer Coefficient ◽  
Internal Heat ◽  
Test Duration ◽  
External Temperature ◽  
Ir Camera ◽  
Internal Heat Transfer

Abstract The aim of this work is to present the development and application of a measurement technique that allows to record internal heat transfer features of real components. In order to apply this method, based on similar approaches proposed in previous literature works, the component is initially heated up to a steady temperature, then a thermal transient is induced by injecting cool air in the internal cooling system. During this process, the external temperature evolution is recorded by means of an IR camera. Experimental data are then exploited to run a numerical procedure, based on a series of transient finite-element analyses of the component. In particular, the test duration is divided into an appropriate number of steps and, for each of them, the heat flux on internal surfaces is iteratively updated as to target the measured external temperature distribution. Heat flux and internal temperature data for all the time steps are eventually employed in order to evaluate the convective heat transfer coefficient via linear regression. This technique has been successfully tested on a cooled high-pressure vane of a Baker Hughes heavy-duty gas turbine, which was realised thanks to the development of a dedicated test rig at the University of Florence, Italy. The obtained results provide sufficiently detailed heat transfer distributions in addition to allowing to appreciate the effect of different coolant mass flow rates. The methodology is also capable of identifying defects, which is demonstrated by inducing controlled faults in the component.

scholarly journals Measurement of Internal Heat Transfer Distribution of Highly-Loaded Gas Turbine Blade by Combined Experimental/Numerical Method

2020 ◽  
Vol 197 ◽  
pp. 10007
Author(s):  
Asif Ali ◽  
Lorenzo Cocchi ◽  
Alessio Picchi ◽  
Bruno Facchini
Keyword(s):  
Heat Transfer ◽  
Surface Temperature ◽  
Gas Turbine ◽  
Cooling System ◽  
Internal Heat ◽  
Infrared Camera ◽  
External Temperature ◽  
Internally Cooled ◽  
Inlet Conditions ◽  
Internal Heat Transfer

To ensure a passable life span of gas turbine hot gas path components the measurement of metal surface temperature is paramount. Experimental analyses on internally cooled devices are often performed on simplified or scaled up geometries, which reduces the applicability of the results to the actual real hardware. A more reliable estimation of cooling performance could be obtained if the real engine component is directly studied. To achieve this goal, an experimental campaign is performed to investigate the internal heat transfer distribution of an industrial blade, cooled by means of an internal U-shaped channel. During the experiment the blade is heated to a known temperature, then a coolant is introduced through the internal channel to induce a thermal transient, during which the external surface temperature is measured with the help of an infrared camera. Then a transient thermal finite element simulation is performed with the same boundary and inlet conditions of the experiment. Based on the output of the simulation, the internal heat transfer distribution is updated until convergence between simulation output external temperature and the experimental temperature is achieved. In order to start the iterative procedure, a first attempt estimation of the internal heat transfer distribution is obtained with a lumped thermal capacitance model approach. Different experiments were performed with different mass flow rates and the results are compared with available literature data. The obtained results allow to observe detailed heat transfer phenomena, strongly bound to the relevant features of the actual real cooling system.

On Selection of Reference Temperature of Heat Transfer Coefficient for Complicated Flows

2007 ◽  
Author(s):  
X. C. Li ◽  
J. Zhou ◽  
K. Aung
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Surface Temperature ◽  
Transfer Coefficient ◽  
Wall Temperature ◽  
Convective Heat Transfer Coefficient ◽  
Internal Heat ◽  
Reference Temperature ◽  
The Heat Transfer Coefficient

One of the most fundamental concepts in heat transfer is the convective heat transfer coefficient, which is closely related with the flow Reynolds number, flow geometry and the thermal conditions on the heat transfer surface. To define the heat transfer coefficient, a reference temperature is needed besides the surface temperature and heat flux. The reference temperature can be chosen differently, such as the fluid bulk mean temperature (for internal flows) and the temperature at the far field (for external flows). For complicated flows, the adiabatic wall temperature, defined as the wall temperature when the surface heat flux is zero, is commonly adopted as the reference temperature. Other options can also be applied to complicated flows. This paper analyzed some of the potential selections of the reference temperature for different flow settings, including film cooling, jet impingement with cross flows and a mixing flow in a straight duct with or without internal heat source. Both laminar and turbulent flows are considered with different boundary conditions. Dramatic changes of heat transfer coefficient are observed with different reference temperatures. In some special conditions the heat transfer coefficient becomes negative, which means the heat flux has a different direction with the driving temperature difference defined. An innovative method is proposed to calculate the heat transfer coefficient of complicated flows with constant surface temperature.

Numerical study of the heat transfer effect on a centrifugal compressor performance

2014 ◽  
Vol 229 (12) ◽  
pp. 2207-2220 ◽  
Author(s):  
Lili Gu ◽  
Armin Zemp ◽  
Reza S Abhari
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Centrifugal Compressor ◽  
Numerical Study ◽  
Scale Up ◽  
Internal Heat ◽  
Transfer Effect ◽  
Heat Transfer Analysis ◽  
Compressor Performance ◽  
Internal Heat Transfer

This paper presents a study of the heat transfer influence on the centrifugal compressor performance. The compressor studied in this paper is based on the scale-up of a turbocharger compressor equipped with a shroudless impeller. To account for the heat transfer effect, a conjugate heat transfer analysis is performed with computational fluid dynamics techniques. The heat transfer phenomena not only externally but also internally are investigated at the design point. The grids adopted in the study are verified at the baseline, with an excellent agreement found between numerical simulations and measurements. The results provide an insight into the dependence of the heat transfer influences on the heat flux paths. The path of the external heat flux passing through the impeller shaft is found to have a great impact on the compressor performance. The study of internal heat transfer shows that the shroud surface dominates the internal heat transfer effect on the efficiency loss. Furthermore, the heat transfer influence is also investigated on the compressor performance at other operating points. The results imply a positive potential margin for the improvement of compressor efficiency by means of heat transfer control.

Experimental Investigation on Impingement Array Cooling Systems Through IR Thermography

2016 ◽  
Author(s):  
L. Cocchi ◽  
B. Facchini ◽  
S. Giuntini ◽  
L. Winchler ◽  
L. Tarchi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Convective Heat Transfer Coefficient ◽  
Wind Tunnel Test ◽  
Target Surface ◽  
Open Loop ◽  
Outer Side ◽  
Ir Thermography ◽  
Ir Camera ◽  
Impingement Plate

This paper reports the results of an experimental campaign involving heat transfer measurements on the target surface of an impingement jet array. Test were performed with the help of an open loop wind tunnel test rig, housing a model of the cooling system. The model general layout consists of an impingement channel, designed as a straight duct with rectangular section. A side of the channel is a steel impingement plate, while the opposite side acts as the impingement target surface and is composed of an electrically heated Inconel sheet supported by a thin steel plate. The coolant flow is provided by a plenum located upstream the impingement plate. The combined use of an inverter controlled electric fan and four rotary vanes vacuum pumps allows air circulation inside the model. Convective heat transfer coefficient on the impingement target surface is evaluated through a steady-state technique. The temperature of the target surface is measured through IR thermography: the outer side of the target surface is painted with a high-emissivity black coating and is observed by an IR camera; the inner temperature is then obtained through a simple finite difference model of the target plate. In the present work, different impingement layouts were tested (3 ≤ Sx/d ≤ 10, 3 ≤ Sy/d ≤ 20, 2.5 ≤ H/d ≤ 3.33) for different values of jet Reynolds number (2000 ≤ Rej ≤ 19000). Heat transfer results show a good agreement with the existing correlations, thus providing a validation for the adopted measurement technique, and extend the investigation to holes pitch values outside from correlations.

Full Thermal Experimental Assessment of a Dendritic Turbine Vane Cooling Scheme

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
S. Luque ◽  
J. Batstone ◽  
D. R. H. Gillespie ◽  
T. Povey ◽  
E. Romero
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Pressure Ratio ◽  
Internal Heat ◽  
Flux Ratio ◽  
Internal Cooling ◽  
Cooling Effectiveness ◽  
Experimental Assessment ◽  
Film Cooling Effectiveness ◽  
Internal Heat Transfer

A full thermal experimental assessment of a novel dendritic cooling scheme for high-pressure turbine vanes has been conducted and is presented in this paper, including a comparison to the current state-of-the-art cooling arrangement for these components. The dendritic cooling system consists of cooling holes with multiple internal branches that enhance internal heat transfer and reduce the blowing ratio at hole exit. Three sets of measurements are presented, which describe, first, the local internal heat transfer coefficient of these structures and, secondly, the cooling flow capacity requirements and overall cooling effectiveness of a highly engine-representative dendritic geometry. Full-coverage surface maps of overall cooling effectiveness were acquired for both dendritic and baseline vanes in the Annular Sector Heat Transfer Facility, where scaled near-engine conditions of Mach number, Reynolds number, inlet turbulence intensity, and coolant-to-mainstream pressure ratio (or momentum flux ratio) are achieved. Engine hardware was used, with laser-sintered metal counterparts for the novel cooling geometry (their detailed configuration, design, and manufacture are discussed). The dendritic system will be shown to offer improved overall cooling effectiveness at a reduced cooling mass flow rate due to a more uniform film cooling effectiveness, a decreased tendency for films to lift off in regions of low external cross flow, improved through-wall heat transfer and internal cooling efficiency, increased internal wetted surface area of the cooling holes, and the enhanced turbulence induced in them.

Heat Transfer Analysis Over a Film Cooled Platform of a Vane Cascade With a Non-Uniform Inlet Flow

2017 ◽  
Author(s):  
G. Barigozzi ◽  
S. Ravelli ◽  
H. Abdeh ◽  
A. Perdichizzi ◽  
M. Henze ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Film Cooling ◽  
Cooling System ◽  
Convective Heat Transfer Coefficient ◽  
Leading Edge ◽  
Heat Transfer Analysis ◽  
Flow Distortion ◽  
Inlet Flow ◽  
Inlet Flow Distortion

This paper reports on heat transfer measurements performed on the film cooled platform of a linear nozzle vane cascade, subject to non-uniform inlet flow conditions. An obstruction, installed upstream of the cascade at different tangential positions, was responsible for inlet flow distortion. The platform cooling system included both purge flow from a slot located upstream of the leading edge and coolant ejection from a row of cylindrical holes located upstream of the slot. Testing was performed at inlet Mach number of Ma1 = 0.12 with both slot and combustor holes blowing at nominal conditions. Measured values of adiabatic film cooling effectiveness on the platform were used to obtain a detailed map of the convective heat transfer coefficient. The final goal was to compute the net heat flux reduction (NHFR), due to film cooling, when varying the relative position between obstruction and airfoil. Aligning the inflow non uniformity with the vane leading edge leads to a detrimental increase in the heat flux into the platform, within the vane passage. Conversely, positive NHFR values are observed over most of the platform surface if the inlet flow distortion is moved toward the suction side of the adjacent vane.

Full Thermal Experimental Assessment of a Dendritic Turbine Vane Cooling Scheme

2012 ◽  
Author(s):  
S. Luque ◽  
J. Batstone ◽  
D. R. H. Gillespie ◽  
T. Povey ◽  
E. Romero
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Pressure Ratio ◽  
Internal Heat ◽  
Flux Ratio ◽  
Internal Cooling ◽  
Cooling Effectiveness ◽  
Experimental Assessment ◽  
Film Cooling Effectiveness ◽  
Internal Heat Transfer

A full thermal experimental assessment of a novel dendritic cooling scheme for high-pressure turbine vanes has been conducted and is presented in this paper, including comparisons to the conventional cooling arrangement for these components. The dendritic cooling system consists of cooling holes with multiple internal branches which enhance internal heat transfer and reduce the blowing ratio at hole exit. Three sets of measurements are presented, which describe, first, the local internal heat transfer coefficient of these structures, and, secondly, the cooling flow capacity requirements and overall cooling effectiveness of a highly engine-representative dendritic geometry. Full-coverage surface maps of overall cooling effectiveness were acquired for both dendritic and baseline vanes in the Annular Sector Heat Transfer Facility, where scaled near-engine conditions of Mach number, Reynolds number, inlet turbulence intensity and coolant-to-mainstream pressure ratio (or momentum flux ratio) are achieved. Engine hardware was used, with laser-sintered metal counterparts for the novel cooling geometry (their detailed configuration, design, and manufacture are discussed). The dendritic system will be shown to offer improved overall cooling effectiveness at a reduced cooling mass flow rate due to a more uniform film cooling effectiveness, a decreased tendency for films to lift off in regions of low external cross flow, improved through-wall heat transfer and internal cooling efficiency, increased internal wetted surface area of the cooling holes, and the enhanced turbulence induced in them.

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