Modeling of Thermally Grown Oxide Layer Growth as a Moving Boundary Problem

2013 ◽  
Author(s):  
Michael Benissan ◽  
Stephen Akwaboa ◽  
Amitava Jana ◽  
Patrick Mensah
Keyword(s):  
Boundary Problem ◽  
Bond Coat ◽  
Gas Turbines ◽  
Moving Boundary ◽  
Turbine Blades ◽  
Heat Diffusion ◽  
Inlet Temperature ◽  
Algebraic Equations ◽  
Heat Diffusion Equation ◽  
Extreme High Temperature

Thermal efficiency of energy conversion systems such as gas turbines can be increased greatly with an increase in the turbine inlet temperature of combustion gases. However, this necessitates the use of efficient cooling techniques in addition to thermal barrier coatings (TBCs) to help significantly improve the life expectancy of gas turbine blades. The effect of TBC use is the formation of oxides, particularly alumina, at the interface of the ceramic top coat and bond coat material during in-service application. This effect is well known to cause failure of TBCs exposed to extreme high temperature environments. The objective of this paper is to present a micro-scale finite difference thermal model for the TBC-Substrate system that considers growth of the TGO layer and predicts in-situ thermal gradients. The governing equation is the transient heat diffusion equation discretized over a 1-D domain using mean value finite volume method with grid adaptation for zones involving depletion of bond coat (BC) material and TGO growth; hence, necessitating a moving interfacial boundary problem. The resulting algebraic equations are simultaneously solved in MATLAB to produce temperature distributions and BC/TGO interfacial locations. The model has utility in studying the evolution of residual stresses and hence prediction of TBC durability and failure.

Development and Fabrication of Silicon Nitride Components for Ceramic Gas Turbine

1997 ◽  
Author(s):  
Keisuke Makino ◽  
Ken-Ichi Mizuno ◽  
Toru Shimamori
Keyword(s):  
High Temperature ◽  
Silicon Nitride ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Turbine Blades ◽  
High Strength ◽  
Inlet Temperature ◽  
Turbine Inlet Temperature ◽  
Spark Plug ◽  
Power Turbine

NGK Spark Plug Co., Ltd. has been developing various silicon nitride materials, and the technology for fabricating components for ceramic gas turbines (CGT) using theses materials. We are supplying silicon nitride material components for the project to develop 300 kW class CGT for co-generation in Japan. EC-152 was developed for components that require high strength at high temperature, such as turbine blades and turbine nozzles. In order to adapt the increasing of the turbine inlet temperature (TIT) up to 1,350 °C in accordance with the project goals, we developed two silicon nitride materials with further unproved properties: ST-1 and ST-2. ST-1 has a higher strength than EC-152 and is suitable for first stage turbine blades and power turbine blades. ST-2 has higher oxidation resistance than EC-152 and is suitable for power turbine nozzles. In this paper, we report on the properties of these materials, and present the results of evaluations of these materials when they are actually used for CGT components such as first stage turbine blades and power turbine nozzles.

scholarly journals Analytical and Experimental Study of Residual Stresses in Thermal Barrier Coatings Deposited on Gas Turbine Blades in Laboratory Dimensions by APS and HVOF Methods to Calculate the Optimal Thickness

2021 ◽  
Vol 3 (1) ◽  
pp. 63-67
Author(s):  
Esmaeil Poursaeidi ◽  
◽  
Farzam Montakhabi ◽  
Javad Rahimi ◽  
◽  
...  
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Analytical Model ◽  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
Turbine Blades ◽  
Thermal Barrier ◽  
Inlet Temperature ◽  
Optimal Thickness ◽  
Barrier Coatings

The constant need to use gas turbines has led to the need to increase turbines' inlet temperature. When the temperature reaches a level higher than the material's tolerance, phenomena such as creep, changes in mechanical properties, oxidation, and corrosion occur at high speeds, which affects the life of the metal material. Nowadays, operation at high temperatures is made possible by proceedings such as cooling and thermal insulation by thermal barrier coatings (TBCs). The method of applying thermal barrier coatings on the turbine blade creates residual stresses. In this study, residual stresses in thermal barrier coatings applied by APS and HVOF methods are compared by Tsui–Clyne analytical model and XRD test. The analytical model results are in good agreement with the experimental results (between 2 and 8% error), and the HVOF spray method creates less residual stress than APS. In the end, an optimal thickness for the coating is calculated to minimize residual stress at the interface between the bond coat and top coat layers.

Development and Evaluation of Silicon Nitride Components for Ceramic Gas Turbine

1998 ◽  
Author(s):  
Yasushi Hara ◽  
Katsura Matsubara ◽  
Ken-ichi Mizuno ◽  
Toru Shimamori ◽  
Hiro Yoshida
Keyword(s):  
Silicon Nitride ◽  
Gas Turbines ◽  
High Speed ◽  
Gas Flow ◽  
Impact Damage ◽  
Turbine Blades ◽  
Impact Testing ◽  
Particle Impact ◽  
Inlet Temperature ◽  
Power Turbine

NGK Spark Plug Co., Ltd. has been developing various silicon nitride materials, and the technology for fabricating components for ceramic gas turbines (CGT) using theses materials. We are supplying silicon nitride material components for the project to develop 300 kW class CGT for co-generation in Japan. EC-152 was developed for components that require high strength at high temperature, such as turbine blades and turbine nozzles. In order to adapt the increasing of the turbine inlet temperature (TIT) up to 1350 °C in accordance with the project goals, we developed two silicon nitride materials with further improved properties: ST-1 and ST-2. ST-1 has a higher strength than EC-152 and is suitable for first stage turbine blades and power turbine blades. ST-2 has higher oxidation resistance than EC-152 and is suitable for power turbine nozzles. On applying these silicon nitride ceramics to CGT engine, we evaluated various properties of silicon nitride materials considering the environment in CGT engine. Particle impact testing is one of those evaluations. Materials used in CGT engine are exposed in high speed gas flow, and impact damage of these materials is considered to be a concern. We tested ST-1 in the particle impact test. In this test, we observed fracture modes, and estimated the critical impact velocity. This paper summarizes the development of silicon nitride components, and the result of evaluations of these silicon nitride materials.

Numerical Simulation on Gas Turbine Film Cooling of Curved Surface With Backward Injection

2012 ◽  
Author(s):  
Shashank Shetty ◽  
Xianchang Li ◽  
Ganesh Subbuswamy
Keyword(s):  
Numerical Simulation ◽  
Gas Turbine ◽  
Film Cooling ◽  
Gas Turbines ◽  
Turbine Blades ◽  
Operating Conditions ◽  
Strong Mixing ◽  
Inlet Temperature ◽  
Film Cooling Effectiveness ◽  
Aerodynamic Loss

Due to the unique role of gas turbine engines in power generation and aircraft propulsion, significant effort has been made to improve the gas turbine performance. As a result, the turbine inlet temperature is usually elevated to be higher than the metal melting point. Therefore, effective cooling of gas turbines is a critical task for engines’ efficiency as well as safety and lifetime. Film cooling has been used to cool the turbine blades for many years. The main issues related to film cooling are its poor coverage, aerodynamic loss, and increase of heat transfer coefficient due to strong mixing. To overcome these problems, film cooling with backward injection has been found to produce a more uniform cooling coverage under low pressure and temperature conditions and with simple cylindrical holes. Therefore, the focus of this paper is on the performance of film cooling with backward injection at gas turbine operating conditions. By applying numerical simulation, it is observed that along the centerline on both concave and convex surfaces, the film cooling effectiveness decreases with backward injection. However, cooling along the span is improved, resulting in more uniform cooling.

Effect of blowing ratio on Film-Cooling effectiveness of Ginkgo Shaped Holes: A numerical approach

2021 ◽  
Author(s):  
Muhammad Awais ◽  
Reaz Hasan ◽  
Md. Hamidur Rahman
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Thermal Protection ◽  
Turbine Blades ◽  
Operating Conditions ◽  
Bottom Surface ◽  
Inlet Temperature ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Lift Off

Modern gas turbine engines operate at significantly high temperatures to improve thermal efficiency and power output to a greater extent. The enhancement in rotor inlet temperature (RIT) increases the heat transfer rate to the turbine blades which requires sophisticated cooling schemes to maintain the blade temperature in acceptable levels. Therefore, the present work refers to the numerical investigation of film cooling technique applied in gas turbines. The cooling performance of two different shaped holes namely Ginkgo Forward (GF) and Ginkgo Reverse (GR)) were investigated in terms of centerline and local lateral effectiveness and comprehensive comparison was made with the cooling performance of cylindrical (CY) hole. The investigations were performed at two density ratios (DR=1.6, 2.0) and three different blowing ratios (BR=1.0, 1.5 and 2.0). At all the operating conditions, the results demonstrated significant augmentation in centerline and lateral effectiveness when GR shaped hole was employed followed by the GF and CY cooling holes. For shaped holes, the low velocity gradient through the film alleviated jet lift off and turbulence intensity resulting in decreased entrainment of hot gas to bottom surface. To conclude, the lateral coverage due to the shaped cooling holes significantly enhanced the thermal protection and overall cooling performance.

scholarly journals Recent Development in Turbine Blade Film Cooling

2001 ◽  
Vol 7 (1) ◽  
pp. 21-40 ◽  
Author(s):  
Je-Chin Han ◽  
Srinath Ekkad
Keyword(s):  
Turbine Blade ◽  
Film Cooling ◽  
Gas Turbines ◽  
High Performance ◽  
Pressure Ratio ◽  
Turbine Blades ◽  
Protective Layer ◽  
Turbine Rotor ◽  
Industrial Applications ◽  
Inlet Temperature

Gas turbines are extensively used for aircraft propulsion, land-based power generation, and industrial applications. Thermal efficiency and power output of gas turbines increase with increasing turbine rotor inlet temperature (RIT). The current RIT level in advanced gas turbines is far above the .melting point of the blade material. Therefore, along with high temperature material development, a sophisticated cooling scheme must be developed for continuous safe operation of gas turbines with high performance. Gas turbine blades are cooled internally and externally. This paper focuses on external blade cooling or so-called film cooling. In film cooling, relatively cool air is injected from the inside of the blade to the outside surface which forms a protective layer between the blade surface and hot gas streams. Performance of film cooling primarily depends on the coolant to mainstream pressure ratio, temperature ratio, and film hole location and geometry under representative engine flow conditions. In the past number of years there has been considerable progress in turbine film cooling research and this paper is limited to review a few selected publications to reflect recent development in turbine blade film cooling.

scholarly journals Multidisciplinary design optimization of film-cooled gas turbine blades

1999 ◽  
Vol 5 (2) ◽  
pp. 97-119 ◽  
Author(s):  
Shashishekara S. Talya ◽  
J. N. Rajadas ◽  
A. Chattopadhyay
Keyword(s):  
Objective Function ◽  
Design Optimization ◽  
Gas Turbine ◽  
Upper Bound ◽  
Film Cooling ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Heat Diffusion ◽  
Heat Transfer Analysis ◽  
Heat Diffusion Equation

Design optimization of a gas turbine blade geometry for effective film cooling toreduce the blade temperature has been done using a multiobjective optimization formulation. Three optimization formulations have been used. In the first, the average blade temperature is chosen as the objective function to be minimized. An upper bound constraint has been imposed on the maximum blade temperature. In the second, the maximum blade temperature is chosen as the objective function to be minimized with an upper bound constraint on the average blade temperature. In the third formulation, the blade average and maximum temperatures are chosen as objective functions. Shape optimization is performed using geometric parameters associated with film cooling and blade external shape. A quasi-three-dimensional Navier–Stokes solver for turbomachinery flows is used to solve for the flow field external to the blade with appropriate modifications to incorporate the effect of film cooling. The heat transfer analysis for temperature distribution within the blade is performed by solving the heat diffusion equation using the finite element method. The multiobjective Kreisselmeier–Steinhauser function approach has been used in conjunction with an approximate analysis technique for optimization. The results obtained using both formulations are compared with reference geometry. All three formulations yield significant reductions in blade temperature with the multiobjective formulation yielding largest reduction in blade temperature.

scholarly journals Gems of Turbine Efficiency

2014 ◽  
Vol 136 (09) ◽  
pp. 76-77
Author(s):  
Lee S. Langston
Keyword(s):  
Single Crystal ◽  
Gas Turbines ◽  
Turbine Blades ◽  
Inlet Temperature ◽  
Jet Engines ◽  
Turbine Inlet Temperature ◽  
Corrosion Resistant ◽  
Commercial Use ◽  
Turbine Efficiency ◽  
Turbine Airfoils

This article discusses the use of turbine single-crystal blades in gas turbines. Single-crystal turbine blades were first used in military engines on Pratt’s F100 engine, which powered the F16 and F15 fighter aircrafts. Their first commercial use was on P&WA’s JT9D-7R4 engine, which received FAA certification in 1982, powering Boeing’s 767 and the Airbus A310. In jet engines, single-crystal turbine airfoils have proven to have as much as nine times more relative life in terms of creep strength and thermal fatigue resistance and over three times more relative life for corrosion resistance, when compared to equiaxed crystal counterparts. Modern high turbine inlet temperature jet engines with long life would not be possible without the use of single-crystal turbine airfoils. By eliminating grain boundaries, single-crystal airfoils have longer thermal and fatigue life, are more corrosion resistant, can be cast with thinner walls, and have a higher melting temperature. These improvements all contribute to higher gas turbine thermal efficiencies.

scholarly journals Computational Modeling and Thermal Paint Verification of Film-Cooling Designs for an Unshrouded High-Pressure Turbine Blade

1999 ◽  
Author(s):  
Steven G. Gegg ◽  
Nathan J. Heidegger ◽  
Ronald A. Mikkelson
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Turbine Blade ◽  
Film Cooling ◽  
Data Exchange ◽  
Turbine Blades ◽  
Inlet Temperature ◽  
High Pressure Turbine ◽  
Extreme High Temperature ◽  
Blade Tip

High pressure turbine blades are exposed to an extreme high temperature environment due to increasing turbine inlet temperature. High heat fluxes are likely on the blade pressure surface. Other regions, such as the trailing edge and blade tip may be difficult to cool uniformly. Unshrouded blades present an additional challenge due to the pressure driven transport of hot gas across the blade tip. The blade tip region is therefore prone to severe thermal stress, fatigue and oxidation. In order to develop effective cooling methods, designers require detailed flow and heat transfer information. This paper reports on computational aerodynamics and heat transfer studies for an unshrouded high pressure turbine blade. The emphasis is placed on the application of appropriate 3-D models for the prediction of airfoil surface temperatures. Details of the film cooling model, boundary conditions and data exchange with heat transfer models are described. The analysis approach has been refined for design use to provide timely and accurate results. Film cooling designs are to be tailored for the best coverage of the blade tip region. Designs include near-tip pressure side films and blade tip cooling holes. Hole placement and angle are investigated to achieve the best coolant coverage on the blade tip. Analytical results are compared to a thermal paint test on engine hardware. In addition to film cooling strategies, other aerodynamic/heat transfer design approaches are discussed to address the cooling requirements for an unshrouded blade.

scholarly journals Effect of spherical blockage configurations on film cooling

2018 ◽  
Vol 22 (5) ◽  
pp. 1933-1942 ◽  
Author(s):  
Jin Wang ◽  
Ke Tian ◽  
Kai Zhang ◽  
Jakov Baleta ◽  
Bengt Sunden
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Rectangular Channel ◽  
Turbine Blades ◽  
Dust Particles ◽  
Inlet Temperature ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Lateral Film ◽  
Comparison Of The Results

With increasing inlet temperature of gas turbines, turbine blades need to be effectively protected by using cooling technologies. However, the deposition from the fuel impurities and dust particles in the air is often found inside film holes, which results in partial hole blockage. In this paper, the deposition geometry is simplified as a rectangular channel, and the effect of three blockage ratios is investigated by using the computational fluid dynamics. In addition, water droplets are also released from the coolant inlet to provide a comparison of the results with and without mist injection. It is found that the lateral film cooling effectiveness is reduced with increasing blockage ratio. For all the cases with the blowing ratio 0.6, 1% mist injection provides an improvement of the cooling performance by approximately 10%.

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