Effect of the Biot Number on Metal Temperature of Thermal-Barrier-Coated Turbine Parts: Real Engine Measurements

2012 ◽  
Author(s):  
Marc Henze ◽  
Laura Bogdanic ◽  
Kurt Muehlbauer ◽  
Martin Schnieder
Keyword(s):  
Reynolds Number ◽  
Gas Turbine ◽  
Load Condition ◽  
Metal Temperature ◽  
Thermal Barrier ◽  
Application Process ◽  
Hot Gas ◽  
Model Predictions ◽  
Lower Load ◽  
The Impact

For numerous hot gas parts (e.g. blades or vanes) of a gas turbine, thermal barrier coating (TBC) is used to reduce the metal temperature to a limit that is acceptable for the component and the required lifetime. However, the ability of the TBC to reduce the metal temperature is not constant, it is a function of Biot and Reynolds number. This behavior might lead to a vane’s or blade’s metal temperature increase at lower load relative to a reference load condition of the gas turbine (i.e. at lower operating Reynolds number). A measurement campaign has been performed, to evaluate metal temperature measurements on uncoated and coated turbine parts in Alstom’s GT26 test power plant in Switzerland. Herewith the impact of varying Reynolds number on the ability of the TBC to protect the turbine components was evaluated. This paper reports on engine-run validation, including details on the application of temperature sensors on thermal-barrier-coated parts. Different methods for the application of thermocouples that were taken into account during the development of the application process are shown. Measurement results for a range of Reynolds number are given and compared to model predictions. Focus of the evaluation is on the measurements underneath the TBC. The impact of different Reynolds number on the ability of the TBC to protect the parts against the hot gas is shown. TBC coated components show under certain circumstances higher metal temperatures at lower load compared to a reference load condition. The measurement values obtained from real engine tests can be confirmed by 1D-model predictions that explain the dependency of the TBC effect on Biot and Reynolds number.

Effect of the Biot Number on Metal Temperature of Thermal-Barrier-Coated Turbine Parts—Real Engine Measurements

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Marc Henze ◽  
Laura Bogdanic ◽  
Kurt Muehlbauer ◽  
Martin Schnieder
Keyword(s):  
Reynolds Number ◽  
Gas Turbine ◽  
Load Condition ◽  
Metal Temperature ◽  
Thermal Barrier ◽  
Application Process ◽  
Hot Gas ◽  
Model Predictions ◽  
Lower Load ◽  
The Impact

For numerous hot gas parts (e.g., blades or vanes) of a gas turbine, thermal barrier coating (TBC) is used to reduce the metal temperature to a limit that is acceptable for the component and the required lifetime. However, the ability of the TBC to reduce the metal temperature is not constant, it is a function of Biot and Reynolds number. This behavior might lead to a vane's or blade's metal temperature increase at a lower load relative to a reference load condition of the gas turbine (i.e., at lower operating Reynolds number). A measurement campaign has been performed to evaluate metal temperature measurements on uncoated and coated turbine parts in Alstom's GT26 test power plant in Switzerland. Therefore, the impact of varying Reynolds number on the ability of the TBC to protect the turbine components was evaluated. This paper reports on engine-run validation, including details on the application of temperature sensors on thermal-barrier-coated parts. Different methods for the application of thermocouples that were taken into account during the development of the application process are shown. Measurement results for a range of Reynolds number are given and compared to model predictions. Focus of the evaluation is on the measurements underneath the TBC. The impact of different Reynolds number on the ability of the TBC to protect the parts against the hot gas is shown. TBC coated components show under certain circumstances higher metal temperatures at lower load compared to a reference load condition. The measurement values obtained from real engine tests can be confirmed by 1D-model predictions that explain the dependency of the TBC effect on Biot and Reynolds number.

scholarly journals Geometric Effects of Thermal Barrier Coating Damage on Turbine Blade Temperatures

2019 ◽  
Author(s):  
Shane Colón ◽  
Mark Ricklick ◽  
Doug Nagy ◽  
Amy Lafleur
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Mach Number ◽  
Flat Plate ◽  
Turbine Blades ◽  
Leading Edge ◽  
Thermal Barrier ◽  
Cold Side ◽  
Hot Gas ◽  
Edge Geometry

Abstract Thermal barrier coatings (TBC) found on turbine blades are a key element in the performance and reliability of modern gas turbines. TBC reduces the heat transfer into turbine blades by introducing an additional surface thermal resistance; consequently allowing for higher gas temperatures. During the service life of the blades, the TBC surface may be damaged due to manufacturing imperfections, handling damage, service spalling, or service impact damage, producing chips in the coating. While an increase in aerofoil temperature is expected, it is unknown to what degree the blade will be affected and what parameters of the chip shape affect this result. During routine inspections, the severity of the chipping will often fall to the discretion of the inspecting engineer. Without a quantitative understanding of the flow and heat transfer around these chips, there is potential for premature removal or possible blade failure if left to operate. The goal of this preliminary study is to identify the major driving parameters that lead to the increase in metal temperature when TBC is damaged, such that more quantitative estimates of blade life and refurbishing needs can be made. A two-dimensional computational Conjugate Heat Transfer model was developed; fully resolving the hot gas path and TBC, bond-coat, and super alloy solids. Representative convective conditions were applied to the cold side to emulate the characteristics of a cooled turbine blade. The hot gas path properties included an inlet temperature of 1600 K with varying Mach numbers of 0.30, 0.59, and 0.80 and Reynolds number of 5.1×105, 7.0×105, and 9.0×105 as referenced from the leading edge of the model. The cold side was given a coolant temperature of 750 K and a heat transfer coefficient of 1500 W/m2*K. The assigned thermal conductivities of the TBC, bond-coat, and metal alloys were 0.7 W/m*K, 7.0 W/m*K, and 11.0 W/m*K, respectively, and layer thicknesses of 0.50 mm, 0.25 mm, and 1.50 mm, respectively. A flat plate model without the presence of the chip was first evaluated to provide a basis of validation by comparison to existing correlations. Comparing heat transfer coefficients, the flat plate model matched within uncertainty to the Chilton-Colburn analogy. In addition, flat plate results captured the boundary layer thickness when compared with Prandtl’s 1/7th power-law. A chip was then introduced into the model, varying the chip width and the edge geometry. The most sensitive driving parameters were identified to be the chip width and Mach number. In cases where the chip width reached 16 times the TBC thickness, temperatures increased by almost 30% when compared to the undamaged equivalents. Additionally, increasing the Mach number of the incoming flow also increased metal temperatures. While the Reynolds number based on the leading edge of the model was deemed negligible, the Reynolds number based on the chip width was found to have a noticeable impact on the blade temperature. In conclusion, this study found that chip edge geometry was a negligible factor, while the Mach number, chip width, and Reynolds number based on the chip width had a significant effect on the total metal temperature.

A Study of the Effects of Thermal Barrier Coating Surface Roughness on the Boundary Layer Characteristics of Gas Turbine Aerofoils

1988 ◽  
Vol 110 (1) ◽  
pp. 88-93 ◽  
Author(s):  
R. M. Watt ◽  
J. L. Allen ◽  
N. C. Baines ◽  
J. P. Simons ◽  
M. George
Keyword(s):  
Surface Roughness ◽  
Reynolds Number ◽  
Gas Turbine ◽  
Thermal Barrier Coating ◽  
Guide Vane ◽  
Thermal Barrier ◽  
Coating Surface ◽  
Barrier Coating ◽  
Nozzle Guide Vane ◽  
Nozzle Guide

The effect of thermal barrier coating surface roughness on the aerodynamic performance of gas turbine aerofoils has been investigated for the case of a profile typical of current first-stage nozzle guide vane design. Cascade tests indicate a potential for significant extra loss, depending on Reynolds number, due to thermal barrier coating in its “as-sprayed” state. In this situation polishing coated vanes is shown to be largely effective in restoring their performance. The measurements also suggest a critical low Reynolds number below which the range of roughness tested has no effect on cascade efficiency. Transition detection involved a novel use of thin-film anemometers painted and fired onto the TBC surfaces.

scholarly journals Impact of Cooling with Thermal Barrier Coatings on Flow Passage in a Gas Turbine

Energies ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 85
Author(s):  
Yuanzhe Zhang ◽  
Pei Liu ◽  
Zheng Li
Keyword(s):  
Gas Turbine ◽  
Thermal Barrier Coatings ◽  
Thermal Efficiency ◽  
Gas Turbines ◽  
Thermal Barrier ◽  
Power Sources ◽  
Barrier Coatings ◽  
Flow Passage ◽  
Blade Cooling ◽  
The Impact

Inlet temperature is vital to the thermal efficiency of gas turbines, which is becoming increasingly important in the context of structural changes in power supplies with more intermittent renewable power sources. Blade cooling is a key method for gas turbines to maintain high inlet temperatures whilst also meeting material temperature limits. However, the implementation of blade cooling within a gas turbine—for instance, thermal barrier coatings (TBCs)—might also change its heat transfer characteristics and lead to challenges in calculating its internal temperature and thermal efficiency. Existing studies have mainly focused on the materials and mechanisms of TBCs and the impact of TBCs on turbine blades. However, these analyses are insufficient for measuring the overall impact of TBCs on turbines. In this study, the impact of TBC thickness on the performance of gas turbines is analyzed. An improved mathematical model for turbine flow passage is proposed, considering the impact of cooling with TBCs. This model has the function of analyzing the impact of TBCs on turbine geometry. By changing the TBCs’ thickness from 0.0005 m to 0.0013 m, its effects on turbine flow passage are quantitatively analyzed using the proposed model. The variation rules of the cooling air ratio, turbine inlet mass flow rate, and turbine flow passage structure within the range of 0.0005 m to 0.0013 m of TBC thicknesses are given.

A Study on the Flow and Thermal Stress Analysis of the Hot Gas Casing of the Gas Turbine

2006 ◽  
Vol 306-308 ◽  
pp. 169-174
Author(s):  
Young Jin Choi ◽  
Young Shin Lee ◽  
Jae Hoon Kim ◽  
Won Shik Park ◽  
Hyun Soo Kim
Keyword(s):  
Thermal Analysis ◽  
Thermal Stress ◽  
Stress Analysis ◽  
Gas Turbine ◽  
Flow Analysis ◽  
Load Condition ◽  
Temperature Data ◽  
Thermal Gradients ◽  
Thermal Stress Analysis ◽  
Hot Gas

The hot gas casing of the gas turbine has operated in high temperatures and thermal gradients. The structure safety of hot gas casing will be highly depend on the thermal stress. In this paper, flow and thermal stress analysis of the hot gas casing is carried out using ANSYS program. The obtained temperature data by flow analysis of hot gas casing is applied to the load condition of the thermal analysis. The thermal stress analysis is carried out the elastic-plasticity analysis. The pressure, temperature and velocity of the flow and thermal stress of the hot gas casing are presented

scholarly journals Prediction and Analysis of Impact of Thermal Barrier Coating Oxidation on Gas Turbine Creep Life

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
E. A. Ogiriki ◽  
Y. G. Li ◽  
Th. Nikolaidis
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Gas Turbine Engine ◽  
Operating Conditions ◽  
Thermal Barrier ◽  
Creep Life ◽  
Premature Failure ◽  
Turbine Engine ◽  
Oxidation Rates ◽  
The Impact

Thermal barrier coatings (TBCs) have been widely used in the power generation industry to protect turbine blades from damage in hostile operating environment. This allows either a high turbine entry temperature (TET) to be employed or a low percentage of cooling air to be used, both of which will improve the performance and efficiency of gas turbine engines. However, with continuous increases in TET aimed at improving the performance and efficiency of gas turbines, TBCs have become more susceptible to oxidation. Such oxidation has been largely responsible for the premature failure of most TBCs. Nevertheless, existing creep life prediction models that give adequate considerations to the effects of TBC oxidation on creep life are rare. The implication is that the creep life of gas turbines may be estimated more accurately if TBC oxidation is considered. In this paper, a performance-based integrated creep life model has been introduced with the capability of assessing the impact of TBC oxidation on the creep life and performance of gas turbines. The model comprises of a thermal, stress, oxidation, performance, and life estimation models. High pressure turbine (HPT) blades are selected as the life limiting component of gas turbines. Therefore, the integrated model was employed to investigate the effect of several operating conditions on the HPT blades of a model gas turbine engine using a creep factor (CF) approach. The results show that different operating conditions can significantly affect the oxidation rates of TBCs which in turn affect the creep life of HPT blades. For instance, TBC oxidation can speed up the overall life usage of a gas turbine engine from 4.22% to 6.35% within a one-year operation. It is the objective of this research that the developed method may assist gas turbine users in selecting the best mission profile that will minimize maintenance and operating costs while giving the best engine availability.

Damage Analysis of Thermal Barrier Coatings Subjected to a High-Velocity Impingement of a Solid Sphere

2019 ◽  
Vol 827 ◽  
pp. 349-354
Author(s):  
Kiyohiro Ito ◽  
Fei Gao ◽  
Masayuki Arai
Keyword(s):  
Gas Turbine ◽  
Impact Velocity ◽  
Thermal Barrier Coatings ◽  
High Velocity ◽  
Turbine Blades ◽  
Interfacial Crack ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Wide Range ◽  
The Impact

A delamination of thermal barrier coatings (TBC) applied to turbine blades in gas turbine could be caused by a high-velocity impingement of various foreign objects. It is important to accurately predict the size of interfacial crack for safety operation of gas turbine. In this study, in order to establish a practical equation for prediction of the length of interfacial crack, a high velocity impingement test and a finite element analysis (FEA) based on a cohesive model were conducted. As the result, the length of interfacial crack is linearly increased with the impact velocity. In addition, it was confirmed that it was accurately estimated by the FEA. The equation for prediction of the length of interfacial crack was formulated based on these results and the energy conservation before and after impingement. Finally, the applicability of the equation was demonstrated in a wide range of impact velocity through a comparison with the experimental results.

Development of Nondestructive Testing Method for Examining Thermal Resistance of Thermal Barrier Coatings on Gas Turbine Blades

2013 ◽  
Author(s):  
Takayuki Ozeki ◽  
Tomoharu Fujii ◽  
Eiji Sakai ◽  
Tetsuo Fukuchi ◽  
Norikazu Fuse
Keyword(s):  
Thermal Resistance ◽  
Surface Temperature ◽  
Gas Turbine ◽  
Thermal Barrier Coatings ◽  
Laser Heating ◽  
Turbine Blades ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Gas Turbine Blades ◽  
Hot Gas

In order to improve the efficiency of electric power generation with gas turbines, the turbine inlet gas temperature needs to be increased. Hence, it is necessary to apply thermal barrier coatings (TBCs) to various hot gas path components. Although TBCs protect the substrate of hot gas path components from high-temperature gas, their thermal resistance degrades over time because of erosion and sintering of the topcoat. When the thermal resistance of TBCs degrades, the surface temperature of the substrate becomes higher, and this temperature increase affects the durability of the hot gas path components. Therefore, to understand the performance of serviced TBCs, the thermal resistance of TBCs needs to be examined by the nondestructive testing (NDT) method. This method has already been reported for TBCs applied to a combustion liner. However, recently, TBCs have been applied to gas turbine blades that have complex three-dimensional shapes, and therefore, an NDT method for examining the thermal resistance of TBCs on blades was developed. This method is based on active thermography using carbon dioxide laser heating and surface temperature measurement of the topcoat by using an infrared camera. The thermal resistance of TBCs is calculated from the topcoat surface temperature when the laser beam heats the surface. In this study, the developed method was applied to a cylindrical TBC sample that simulated curvature on the suction side of a blade, and the results showed the appropriate laser heating condition for this method. Under the appropriate condition, this method could also examine the thermal resistance of TBCs present at 70% of the height of the blade. With these results, this method could determine the thermal resistance within an error range of 4%, as compared to destructive testing.

The Development of Ceramic-Based Thermocouples for Application in Gas Turbines

2001 ◽  
Author(s):  
D. M. Farrell ◽  
J. Parmar ◽  
B. J. Robbins
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Development Project ◽  
Thermal Barrier ◽  
Laboratory Studies ◽  
Barrier Coatings ◽  
Hot Gas ◽  
Elevated Pressures ◽  
Signal Output ◽  
Harsh Conditions

A research and development project has recently been carried out to develop ceramic thermocouple probes (CTPs) capable of measuring temperatures up to 2000°C and rugged enough to withstand extended service in high-temperature gas turbine environments. Existing metallic thermocouple technology cannot withstand such conditions for sustainable periods of time. Following initial laboratory studies, CTP trials were carried out in power generation boilers (Farrell and Higginbottom, 1995). Prototype CTPs were subsequently developed for evaluation in gas turbine (GT) combustors (at atmospheric and elevated pressures) and in a Spey engine (Patent, 1996). The CTPs performed well under the harsh conditions imposed, demonstrating their mechanical integrity and consistency/sustainability of signal output. Initial studies have also been carried out with a view to applying ‘thin-layer’ ceramic thermocouples directly onto thermal barrier coatings to give surface temperatures on stator or other hot gas surfaces, and are briefly mentioned. Rowan Technologies and TÜV Energy Services are currently looking for companies interested in exploiting this new ceramic thermocouple technology.

Development of Actual TBC Exposure Temperature Prediction Method

2004 ◽  
Author(s):  
Masahiko Morinaga ◽  
Tomoharu Fujii ◽  
Takeshi Takahashi
Keyword(s):  
Thermal Conductivity ◽  
Substrate Temperature ◽  
Gas Turbine ◽  
Co2 Laser ◽  
Infrared Camera ◽  
Thermal Barrier ◽  
Remaining Life ◽  
Hot Gas ◽  
Exposure Temperature ◽  
Barrier Performance

Gas turbines are being operated at ever-higher temperatures in order to increase their efficiency. As a result, thermal barrier technology to protect the gas turbine hot gas path parts from high-temperature combustion gas is becoming increasingly important, making it necessary to evaluate the thermal barrier performance of the thermal barrier coating (TBC) coated on these gas turbine hot gas path parts. Thermal barrier performance of the TBC deteriorates with the number of operating hours of the gas turbine. The degradation of TBC thermal barrier performance raises substrate temperature, and this rise in substrate temperature reduces the remaining life of the substrate. We proposed an effective nondestructive inspection (NDI) method to evaluate the thermal barrier performance of the TBC by infrared transient heating of the TBC surface. The temperature behavior closely correlated with the thermal barrier performance of the TBC. The results of numerical analysis and laboratory tests showed that the proposed NDI method was effective for evaluating the thermal barrier performance of TBC. So we developed NDI apparatus to inspect the thermal barrier performance of actual combustion liner TBC. In this NDI apparatus, the surface of the TBC was heated using a CO2 laser, and the temperature of the heated surface measured using an infrared camera. The CO2 laser and infrared camera were fixed, while the measured combustion liner was traversed continuously. The NDI apparatus developed enabled us to inspect the whole inner surface of an actual gas turbine combustion liner. We also showed the correlation with thermal conductivity of a virgin TBC, thermal conductivity of an inspected TBC, operating hours and TBC exposure temperature in our TBC thermophysical property study. The combination of this method and the NDI apparatus developed proved an effective way of clarifying the operating temperature of the hot gas path parts of the gas turbine. In this paper, we show a method for predicting actual gas turbine TBC exposure temperature, important when evaluating the remaining life of gas turbine substrate by the NDI apparatus developed and method of predicting TBC exposure temperature.

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