Comparison of Sodium Sulphate Deposition Rate Models Based on Operational Factors Influencing Hot Corrosion Damage in Aero-Engines

2020 ◽  
Author(s):  
Evangelia Pontika ◽  
Panagiotis Laskaridis ◽  
Theoklis Nikolaidis ◽  
Max Koster
Keyword(s):  
Gas Turbine ◽  
Analysis Of Variance ◽  
Deposition Rate ◽  
Hot Corrosion ◽  
Molten Salts ◽  
Experimental Studies ◽  
Corrosion Damage ◽  
Sodium Sulphate ◽  
Operating Conditions ◽  
Aircraft Engines

Abstract Hot corrosion is defined as the accelerated oxidation/sulphidation in the presence of alkali metal molten salts. It is a form of chemical attack that causes good metal loss. Current lifing models in aircraft engines focus on creep, fatigue and oxidation while hot corrosion damage has been overlooked as being of secondary importance. However, the absence of hot corrosion lifing models for aircraft engines often leads to unexpected and unexplained hot corrosion findings by aircraft engine operators and Maintenance, Repair and Overhaul (MRO) providers during inspections. Although hot corrosion does not cause failure on its own, the interaction with other damage mechanisms can reduce component life significantly, consequently, there is a requirement for including hot corrosion in the damage prediction process of aircraft engines. In both theoretical and experimental studies in literature, deposition of molten salts is identified as one of the primary conditions for hot corrosion to occur and an increased amount of deposited liquid salts accelerates the attack. Currently, most hot corrosion studies are limited to experimental testing of superalloys which are pre-coated with a controlled layer of salts. Such experimental studies are disconnected from gas turbine operating conditions during service. The present paper analyses two deposition rate models applicable to gas turbine operating conditions using Design of Experiments. Design space exploration is presented by taking into account gas turbine operating parameters which vary during a flight as well as temperature ranges where hot corrosion can occur. Analysis of variance is presented for 6 input parameters using Box-Behnken 3-level factorial design. Results from the Analysis of Variance indicate that the deposition rate models are sensitive to pressure and salt concentration in the gas flow. Finally, the saturation point of sodium sulphate has been investigated within the operating range of gas turbine and it was found that it can vary significantly under different conditions.

Numerical and Experimental Evaluation of a Dual-Fuel Dry-Low-NOx Micromix Combustor for Industrial Gas Turbine Applications

2018 ◽  
Vol 11 (1) ◽  
Author(s):  
Harald H. W. Funke ◽  
Nils Beckmann ◽  
Jan Keinz ◽  
Sylvester Abanteriba
Keyword(s):  
Gas Turbine ◽  
Combustion Process ◽  
Experimental Studies ◽  
Research Process ◽  
Operating Conditions ◽  
Experimental Investigations ◽  
Dual Fuel ◽  
Pure Hydrogen ◽  
Ongoing Research ◽  
Industrial Gas Turbine

Abstract The dry-low-NOx (DLN) micromix combustion technology has been developed originally as a low emission alternative for industrial gas turbine combustors fueled with hydrogen. Currently, the ongoing research process targets flexible fuel operation with hydrogen and syngas fuel. The nonpremixed combustion process features jet-in-crossflow-mixing of fuel and oxidizer and combustion through multiple miniaturized flames. The miniaturization of the flames leads to a significant reduction of NOx emissions due to the very short residence time of reactants in the flame. The paper presents the results of a numerical and experimental combustor test campaign. It is conducted as part of an integration study for a dual-fuel (H2 and H2/CO 90/10 vol %) micromix (MMX) combustion chamber prototype for application under full scale, pressurized gas turbine conditions in the auxiliary power unit Honeywell Garrett GTCP 36-300. In the presented experimental studies, the integration-optimized dual-fuel MMX combustor geometry is tested at atmospheric pressure over a range of gas turbine operating conditions with hydrogen and syngas fuel. The experimental investigations are supported by numerical combustion and flow simulations. For validation, the results of experimental exhaust gas analyses are applied. Despite the significantly differing fuel characteristics between pure hydrogen and hydrogen-rich syngas, the evaluated dual-fuel MMX prototype shows a significant low NOx performance and high combustion efficiency. The combustor features an increased energy density that benefits manufacturing complexity and costs.

Validation of Multi-Frequency Eddy Current MWM Sensors and MWM-Arrays for Coating Production Quality and Refurbishment Assessment

2003 ◽  
Author(s):  
Vladimir Zilberstein ◽  
Ian Shay ◽  
Robert Lyons ◽  
Neil Goldfine ◽  
Thomas Malow ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Eddy Current ◽  
Coating Thickness ◽  
Bond Coat ◽  
Gas Turbines ◽  
Corrosion Damage ◽  
Operating Conditions ◽  
Ongoing Research ◽  
Metallic Bond ◽  
Thickness Measurements

Coatings for oxidation, corrosion, and thermal protection provide the required materials performance for gas turbine blades and vanes in state-of-the-art industrial gas turbines. These turbines must withstand severe operating conditions for well over ten thousand hours. Variations in the coating thickness, and increased porosity, can influence the lifetime of such coatings significantly. For components that have been removed from service, effective assessment of the aged coating and substrate condition is critical for refurbish/replace/continue-to-run decisions. A suitable device for coating thickness measurement and detection of unacceptable porosity is needed for ensuring the quality of such coatings. In this paper, we present new results on coating thickness measurements for metallic MCrAlY overlay coatings on gas turbine parts. These measurements were performed with a Meandering Winding Magnetometer (MWM®) eddy-current sensor using grid methods. This technique allows proper coating measurements even after a diffusion heat treatment for a better coating adhesive strength. The MWM technology enables measurement of the coating thickness, the absolute electrical conductivity (which may in turn be related to porosity or other properties of interest), and lift-off, which is related to surface roughness. Single-channel MWM sensors and multi-channel imaging MWM-Arrays permit capture of features of interest for a population of components. New capabilities for inspecting gas turbine components are, thus, provided. Inspection applications include metallic and non-metallic coating thickness measurements, porosity measurements, and detection of cracks on complex surfaces. Results of coating assessment for a production line of gas turbine vanes by means of a multifrequency MWM technique are presented for various combinations of coatings and base metals. A description of improved multiple frequency quantitative inversion methods is provided for simultaneous and independent measurement of multiple unknowns such as metallic bond coat thickness, metallic bond coat porosity, and top coat thickness. Ongoing research focuses on characterization of aged components using MWM sensors and imaging MWM-Arrays as well as on development of enhanced algorithms for four and five unknown coating / substrate properties. In a recent study of hot corrosion, uncoated nickel alloy specimens were characterized using an MWM sensor with grid methods. Preliminary results indicated that, within the limitations of the three-unknown single-layer model used, the method could readily identify specimens with no apparent corrosion damage, specimens with moderate corrosion damage, and specimens with severe corrosion damage.

Numerical and Experimental Evaluation of a Dual-Fuel Dry-Low-NOx Micromix Combustor for Industrial Gas Turbine Applications

2017 ◽  
Author(s):  
H. H.-W. Funke ◽  
N. Beckmann ◽  
J. Keinz ◽  
S. Abanteriba
Keyword(s):  
Gas Turbine ◽  
Combustion Process ◽  
Experimental Studies ◽  
Research Process ◽  
Operating Conditions ◽  
Experimental Investigations ◽  
Dual Fuel ◽  
Pure Hydrogen ◽  
Ongoing Research ◽  
Industrial Gas Turbine

The Dry-Low-NOx (DLN) Micromix combustion technology has been developed originally as a low emission alternative for industrial gas turbine combustors fueled with hydrogen. Currently the ongoing research process targets flexible fuel operation with hydrogen and syngas fuel. The non-premixed combustion process features jet-in-crossflow-mixing of fuel and oxidizer and combustion through multiple miniaturized flames. The miniaturization of the flames leads to a significant reduction of NOx emissions due to the very short residence time of reactants in the flame. The paper presents the results of a numerical and experimental combustor test campaign. It is conducted as part of an integration study for a dual-fuel (H2 and H2/CO 90/10 Vol.%) Micromix combustion chamber prototype for application under full scale, pressurized gas turbine conditions in the auxiliary power unit Honeywell Garrett GTCP 36-300. In the presented experimental studies, the integration-optimized dual-fuel Micromix combustor geometry is tested at atmospheric pressure over a range of gas turbine operating conditions with hydrogen and syngas fuel. The experimental investigations are supported by numerical combustion and flow simulations. For validation, the results of experimental exhaust gas analyses are applied. Despite the significantly differing fuel characteristics between pure hydrogen and hydrogen-rich syngas the evaluated dual-fuel Micromix prototype shows a significant low NOx performance and high combustion efficiency. The combustor features an increased energy density that benefits manufacturing complexity and costs.

Design of an optically accessible turbulent combustion system

2018 ◽  
Vol 233 (1) ◽  
pp. 336-349
Author(s):  
Mohammad A Hossain ◽  
Ahsan Choudhuri ◽  
Norman Love
Keyword(s):  
Gas Turbine ◽  
Turbulent Combustion ◽  
High Intensity ◽  
Flame Structure ◽  
Experimental Studies ◽  
Deep Understanding ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Operating Pressure ◽  
Combustion System

In order to design the next generation of gas turbine combustors and rocket engines, understanding the flame structure at high-intensity turbulent flows is necessary. Many experimental studies have focused on flame structures at relatively low Reynolds and Damköhler numbers, which are useful but do not help to provide a deep understanding of flame behavior at gas turbine and rocket engine operating conditions. The current work is focused on the presentation of the design and development of a high-intensity (Tu = 15–30%) turbulent combustion system, which is operated at compressible flow regime from Mach numbers of 0.3 to 0.5, preheated temperatures up to 500 K, and premixed conditions in order to investigate the flame structure at high Reynolds and Damköhler numbers in the so-called thickened flame regime. The design of an optically accessible backward-facing step stabilized combustor was designed for a maximum operating pressure of 0.6 MPa. Turbulence generator grid was introduced with different blockage ratios from 54 to 67% to generate turbulence inside the combustor. Optical access was provided via quartz windows on three sides of the combustion chamber. Extensive finite element analysis was performed to verify the structural integrity of the combustor at rated conditions. In order to increase the inlet temperature of the air, a heating section is designed and presented in this paper. Separate cooling subsystem designs are also presented. A 10 kHz time-resolved particle image velocimetry system and a 3 kHz planer laser-induced fluorescence system are integrated with the system to diagnose the flow field and the flame, respectively. The combustor utilizes a UNS 316 stainless steel with a minimum wall thickness of 12.5 mm. Quartz windows were designed with a maximum thickness of 25.4 mm resulting in an overall factor of safety of 3.5.

Chemical Kinetic Models for Enhancing Gas Turbine Flexibility: Model Validation and Application

2016 ◽  
Author(s):  
Felix Güthe ◽  
Martin Gassner ◽  
Stefano Bernero ◽  
Thiemo Meeuwissen ◽  
Torsten Wind
Keyword(s):  
Gas Turbine ◽  
Experimental Studies ◽  
Operating Conditions ◽  
Theoretical Modelling ◽  
Validation Data ◽  
Part Load ◽  
Stable Conditions ◽  
Safety Margins ◽  
Wide Range ◽  
Operational Range

In recent years, market trends towards higher power generation flexibility are driving gas turbine requirements of operation at stable conditions and below environmental emission guarantees over a wide range of operating conditions, such as load, and for changing fuels. In order to achieve these targets, engine components and operation concept need to be optimized to minimise emissions (e.g. CO, NOx) and combustion instabilities, as well as to maximize component lifetime. Therefore the combination of field experience, experimental studies and theoretical modelling of flames with state of the art tools play a key role in enabling the development of such solutions. For many applications the relative changes of reactivity due to changes in operation conditions are important thus in this report a few examples are shown, where chemical kinetics simulations are used to determine the reactivity and to predict engine behaviour. The predicted trends are validated by correlating them to validation data from high pressure test rigs and real gas turbine operational data. With this approach the full operational range from highest reactivity (flashback) to lowest reactivity (blow out or CO emission increase) are covered. The study is focused on the sequential combustor (SEV) of reheat engines and addresses both the safety margins with respect to highly reactive fuels and achievable load flexibility with respect to part load CO emissions. The analysis shows that it is necessary to utilize updated kinetic mechanisms since older schemes have proved to be inaccurate. A version of the mechanism developed at NUI Galway in cooperation with Alstom and Texas A&M was used and the results are encouraging, since they are well in line with experimental test data and can be matched to GT conditions to determine, predict, and optimize their operational range. This example demonstrates nicely how a development over several years starting from fundamental basic research over experimental validation finally delivers a product for power plants. This report therefore validates the kinetic model in combination with the approach to use modelling for guidance of the GT development and extending it fuel capabilities. The GT24 / GT26 can not only be operated with H2 containing fuels, but also at very low part load conditions and with the integration of H2 from electrolysis (∼power to gas ∼PTG) the turndown capability can even be further improved. In this way the energy converted at low electricity prices can be stored and utilised at later times when it is advantageous to run the GT at lower loads increasing the overall flexibility. This development is well suited to integrate renewable energy at highly fluctuating availability and price to the energy provisioning by co-firing with conventional fuels.

Heat Transfer Characteristics of a Blade Trailing Edge With Pressure Side Bleed Extraction

2013 ◽  
Author(s):  
H. Saxer-Felici ◽  
S. Naik ◽  
M. Gritsch
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Gas Turbine ◽  
Cooling System ◽  
Experimental Studies ◽  
Operating Conditions ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Heat Transfer Coefficients ◽  
The Impact

This paper investigates the heat transfer and pressure loss characteristic in the internal cooling system of the trailing edge of a gas turbine blade. The geometrical profile of the blade trailing edge and the operating conditions considered are representative of that normally found in a heavy-duty gas turbine. The trailing edge geometry consists of two radial passages with inclined turbulators which are connected with a bend. The trailing edge section consists of pins rows and a flow ejection cut-out slot. The impact of a cross-over hole in the web connecting the serpentine passages is also investigated. Both numerical and experimental studies were conducted at several passage Reynolds numbers ranging from 104 to 106. Experiments were conducted in a Perspex model at atmospheric conditions. The internal heat transfer coefficients were measured via the transient liquid crystal method and the pressure drop was measured via pressure taps. The impact of blade rotation on the heat transfer and pressure drop was also assessed numerically. Comparison of the measured and predicted heat transfer coefficients and pressure drops shows a good agreement for several flow conditions. The three-dimensional flow field in the passage and in the downstream pin banks was well captured numerically, with and without coolant injection via cross-over hole.

Environmental Degradation of Gas Turbine Materials in Steam

1997 ◽  
Author(s):  
Y. Patel ◽  
D. Tamboli ◽  
V. H. Desai ◽  
N. S. Cheruvu
Keyword(s):  
Gas Turbine ◽  
Environmental Degradation ◽  
Hot Corrosion ◽  
Gas Turbines ◽  
Corrosion Damage ◽  
Deionized Water ◽  
Compressed Air ◽  
Inconel 617 ◽  
Oxidation Damage ◽  
Oxidation And Corrosion

Steam has been proposed as an efficient cooling medium for the hot section components in the advanced gas turbines replacing compressed air for more efficient cooling allowing the turbine to operate at higher efficiency. To evaluate the effect of steam on oxidation and corrosion of hot section materials, three superalloys (X-45, Inconel-617 and IN-738LC) were exposed to steam at 840°C. Steam environments used were (a) steam generated from deionized water, (b) steam generated from deionized water with 5ppm each of NaCl and Na2SO4 and (c) steam generated from deionized water with 50 ppm each of NaCl and Na2SO4. The respective exposure times were 3900, 2950, and 1450 hours. IN-738LC showed severe internal oxidation in steam. In contaminated steam the hot corrosion damage was maximum in Inconel-617. X-45 showed less oxidation damage than IN-738LC and less hot corrosion than Inconel-617.

Study on Accuracy of Heat Transfer Coefficient Determination in the Bearing Chamber for Gas Turbine Engine

2020 ◽  
Author(s):  
Illia Petukhov ◽  
Taras Mykhailenko ◽  
Sergiy Yepifanov ◽  
Oleg Shevchuk
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Gas Turbine ◽  
Experimental Studies ◽  
Gas Turbine Engine ◽  
Operating Conditions ◽  
Turbine Engine ◽  
Cooling Medium ◽  
External Cooling

Abstract The heat transfer coefficient (HTC) is one of the key parameters that should be known at the stage of the bearing chamber design. This ensures safe temperature conditions for the lubrication oil and reliable operation of the gas turbine engine. The temperature gradient method is commonly used in experimental practice to determinate the HTC. The accuracy of the HTC determination is sensitive to changing of the bearing chamber operating conditions and should be analyzed at the stage of experimental studies planning. This paper presents a study on the accuracy of HTC determination when the external cooling of the bearing chamber is used to obtain the temperature difference sufficient for measurement. Three ways to reduce the relative error of the HTC determination in the bearing chamber were analyzed: i) decreasing the temperature measurement error; ii) decreasing the temperature of external cooling medium; iii) increasing the external heat transfer coefficient and contribution of wall thermal resistance optimization. For different operating conditions of the bearing chamber, the temperature of the outer wall that ensures the specified accuracy of the experimental HTC and the required parameters of the cooling medium were determined and recommended for practical implementation.

Hot Corrosion Studies Using Electrochemical Techniques of Alloys in a Chloride Molten Salt (NaCl-LiCl) at 650°C

2014 ◽  
Author(s):  
Judith C. Gomez ◽  
Robert Tirawat ◽  
Edgar E. Vidal
Keyword(s):  
Power Generation ◽  
Molten Salt ◽  
Electric Power ◽  
Gas Turbine ◽  
Hot Corrosion ◽  
Molten Salts ◽  
Electrochemical Techniques ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Salt Corrosion

Next-generation solar power conversion systems in concentrating solar power (CSP) applications require high-temperature advanced fluids in the range of 600° to 900°C. Molten salts are good candidates for CSP applications, but they are generally very corrosive to common alloys used in vessels, heat exchangers, and piping at these elevated temperatures. The majority of the molten-salt corrosion evaluations for sulfates with chlorides and some vanadium compounds have been performed for waste incinerators, gas turbine engines, and electric power generation (steam-generating equipment) applications for different materials and molten-salt systems. The majority of the molten-salt corrosion kinetic models under isothermal and thermal cyclic conditions have been established using the weight-loss method and metallographic cross-section analyses. Electrochemical techniques for molten salts have not been employed for CSP applications in the past. Recently, these techniques have been used for a better understanding of the fundamentals behind the hot corrosion mechanisms for thin-film molten salts in gas turbine engines and electric power generation. The chemical (or electrochemical) reactions and transport modes are complex for hot corrosion in systems involving multi-component alloys and salts; but some insight can be gained through thermochemical models to identify major reactions. Electrochemical evaluations were performed on 310SS and In800H in the molten eutectic NaCl-LiCl at 650°C using an open current potential followed by a potentiodynamic polarization sweep. Corrosion rates were determined using Tafel slopes and the Faraday law. The corrosion current density and the corrosion potentials using Pt wire as the reference electrode are reported.

COMPUTATIONAL AND EXPERIMENTAL STUDIES OF A LOW-EMISSION BURNER FOR A PERSPECTIVE TURBOJET ENGINE WITH THE COMPRESSION RATIO EXCEEDING 40

2020 ◽  
Author(s):  
M. A. Danilov ◽  
◽  
M. V. Drobysh ◽  
A. N. Dubovitsky ◽  
F. G. Markov ◽  
...  
Keyword(s):  
Compression Ratio ◽  
Experimental Studies ◽  
The Other ◽  
Aircraft Engines ◽  
Engine Efficiency ◽  
Other Hand ◽  
Turbojet Engine ◽  
Low Emission ◽  
Civil Aircraft ◽  
The One

Restrictions of emissions for civil aircraft engines, on the one hand, and the need in increasing the engine efficiency, on the other hand, cause difficulties during development of low-emission combustors for such engines.

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