scholarly journals Effect of Coal Constituents on the Liquid-Assisted Capture of Impacting Ash Particles in Direct Coal-Fired Gas Turbines

1988 ◽  
Author(s):  
R. Nagarajan ◽  
R. J. Anderson
Keyword(s):  
Physicochemical Properties ◽  
Surface Temperature ◽  
Temperature Dependence ◽  
Deposition Rate ◽  
Gas Turbines ◽  
Turbine Blades ◽  
Coal Ash ◽  
Ash Deposition ◽  
Sticking Coefficient ◽  
Hot Gas

With the growing interest in burning pulverized coal directly in gas turbines, the problem of fouling — blockage of hot-gas pathways by thick ash deposits — is receiving increased attention. The inertial deposition rate of supermicron ash, which determines the fouling propensity of the coal via the thickness of the deposit, depends linearly on the sticking fraction of ash material arriving at the cooled surfaces, e.g., turbine blades and guide vanes. The magnitude and temperature-dependence of the sticking coefficient will depend on the inventory, composition and physicochemical properties of the liquid ‘glue’ consistent with the prevailing temperature, pressure and trace inorganic elemental compositions. As the deposit evolves in time, it encounters several deposition regimes in the order of increasing surface temperature, each characterized by a different source of liquid glue. The effect of coal-ash constituents on the extent of each of these sticking regimes is investigated theoretically here by means of a model of ‘self-regulated’ ash deposition.

Assessing of Hot Gas Parts Using Advanced Eddy Current Testing Methods

2008 ◽  
Author(s):  
Matthias Jungbluth ◽  
Vinay Jonnalagadda ◽  
Erwan Baleine ◽  
Mattias Broddega˚rd ◽  
Rolf Wilkenho¨ner ◽  
...  
Keyword(s):  
Eddy Current ◽  
Gas Turbines ◽  
Thermal Protection ◽  
Protective Coatings ◽  
Turbine Blades ◽  
Diagnostic Methods ◽  
Design Parameters ◽  
Gas Temperature ◽  
Diagnostic Measures ◽  
Hot Gas

The turbine section of state-of-the-art industrial gas turbines is exposed to the most severe conditions such as high temperatures, corrosive environments and high mechanical stresses for several tens of thousands of hours. To withstand these conditions, turbine blades and vanes have become the most sophisticated parts. This, together with advanced manufacturing technologies, strict quality requirements and maximum reliability demands, affects costs. Different design features have been realized in the past to meet the ambitious requirements, and are also under constant development. Blades and vanes made of superalloys with directionally-solidified or single-crystal structure are used to provide highest strengths at temperatures as near as possible to the hot gas temperature. The high integrity and conformity of the parts are required to realize the material potential. Different advanced diagnostic methods are applied to ensure these over time. Another way to increase the operating temperatures of gas turbines is the application of corrosion and thermal protection coatings for one or several rows of the blades and vanes. Deviations in the specified coating thickness tend to reduce the lifetime of such coatings significantly. Hence, the monitoring of this property during the manufacturing requires special nondestructive diagnostic measures. Service exposed parts, which need to be refurbished when the protective coatings are spent, offer a significant operation potential after refurbishment. To guarantee the design parameters during the next service interval, several nondestructive material evaluation methods are available for the necessary part property assessment. Multifrequency Eddy Current has proven itself as an appropriate NDE technique to accomplish the above diagnostic requirements. The paper will give an overview of results gained at Siemens with model based Eddy Current methods using measurement systems developed by Jentek Sensors Inc., USA, and CESI, Italy. Potential applications and limitations of the method also will be discussed.

Repair of Advanced Gas Turbine Blades

2005 ◽  
Author(s):  
Julie McGraw ◽  
Reiner Anton ◽  
Christian Ba¨hr ◽  
Mary Chiozza
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
High Efficiency ◽  
High Reliability ◽  
Turbine Blades ◽  
Base Material ◽  
Operating Experience ◽  
Cost Effective ◽  
Directionally Solidified ◽  
Hot Gas

In order to promote high efficiency combined with high power output, reliability, and availability, Siemens advanced gas turbines are equipped with state-of-the-art turbine blades and hot gas path parts. These parts embody the latest developments in base materials (single crystal and directionally solidified), as well as complex cooling arrangements (round and shaped holes) and coating systems. A modern gas turbine blade (or other hot gas path part) is a duplex component consisting of base material and coating system. Planned recoating and repair intervals are established as part of the blade design. Advanced repair technologies are essential to allow cost-effective refurbishing while maintaining high reliability. This paper gives an overview of the operating experience and key technologies used to repair these parts.

Improving the Efficiency of Heavy-Fuelled Gas Turbines: The Successful Experience Achieved at the Yugadanavi 300 MW CCGT in Sri Lanka

2016 ◽  
Author(s):  
Nuhuman Marikkar ◽  
Matthieu Vierling ◽  
Maher Aboujaib ◽  
Dmitry Sokolov ◽  
Bruno Monetti ◽  
...  
Keyword(s):  
Sri Lanka ◽  
Gas Turbines ◽  
Energy Conversion Efficiency ◽  
High Energy ◽  
Low Grade ◽  
Ash Deposition ◽  
Suppression Effect ◽  
Hot Gas ◽  
High Energy Conversion Efficiency ◽  
Vanadium Species

An important asset of heavy duty gas turbines (“GT”) is their ability to burn a large variety of hydrocarbons, including low grade ones such as ash-forming fuels, in a well-controlled manner while achieving fairly high energy conversion efficiency. In fact, there is still a considerable margin for improving the efficiency of gas turbines burning ash forming fuels if one succeeds in reducing the deposition of the ash in the turbine section which represents however a challenging technology lock. The main difficulty for achieving this ambitious objective lies in the additional fouling entailed by the “inhibition process”. Indeed a magnesium-based corrosion inhibitor is injected into the GT combustors in order to suppress the corrosion threat placed by the highly fusible vanadium species coming from the fuel. This additive represents a substantial increase in the amount of ash crossing the machine whereby substantially accentuating the fouling of the hot gas path parts. Within a joint initiative, LTL Holdings Ltd, GE Power & Water and the UTBM University have successfully tested a novel family of vanadium inhibitors called “bimetallic inhibitors” that combines magnesium and iron and lead to a considerable reduction in ash deposition while keeping intact the anti-corrosion protection. This new inhibitor family brings a decisive improvement in GT efficiency as well as a significant increase in plant availability. Indeed it enables reducing the frequency of the machine shutdowns that are periodically required to remove the ash deposits through water wash. In addition, iron procures an interesting soot suppression effect. The paper outlines the development carried out in this project and sets out the successful field test performed in 2015 at the Yugadanavi 300 MW power plant in Sri Lanka.

Chemistry of Ash-Deposits on Gas Turbines Hot Parts: Reactivity of Nickel, Zinc and Iron Oxides in (Na, V, S) Molten Salts

2008 ◽  
Vol 595-598 ◽  
pp. 169-176 ◽  
Author(s):  
Emmanuel Rocca ◽  
Lionel Aranda ◽  
Michel Molière
Keyword(s):  
High Temperature ◽  
Gas Turbines ◽  
Turbine Blades ◽  
Thermochemical Study ◽  
Efficient Inhibitor ◽  
Hot Gas ◽  
Machine Performance ◽  
Expansion Turbine ◽  
General Complex ◽  
Complex Chemistry

When ash-forming oils or contaminated distillate oils are used as fuels in land-based, marine or aero gas turbines, the hot gas path components, mainly the partition vanes and the blades of the expansion turbine are subjected to the deposition of slags that are corrosive at high temperature due to their low liquidus temperature. This hot corrosion process - if not properly inhibited - entails a dramatic life reduction of the hot gas path parts. MgO is a traditional, efficient inhibitor. Recently, it has been found that NiO also suppresses the corrosiveness of the (Na,S,V) melts by trapping vanadium in a refractory vanadate (Ni3V2O8); this compound is friable and does not tend to accumulate on turbine blades. The use of inhibitors entails losses in both machine performance and availability. Moreover, other metals can interfere with the inhibition process. In particular, zinc and iron are often inadvertently introduced in gas turbines fuels during their transportation or storage and they can significantly interact with nickel. This paper distinguishes the interactions between NiO on one hand and both ZnO and Fe2O3 on the other hand in the general complex chemistry of ash. The thermochemical study of (Na,S,V) melts in presence of Ni confirms that nickel is a good "trapper" of vanadium oxide at high temperature. However, they also show that nickel can react with iron to form the very stable ferrite NiFe2O4 and a low melting point vanadate phase. On the contrary, the presence of zinc affects to a lesser extent the reactivity of NiO versus V2O5 despite the formation of Ni1-xZnxO solid solutions.

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 Problem of Fuel-oil Ash Deposition in Open-cycle Gas Turbines

1953 ◽  
Vol 167 (1) ◽  
pp. 291-312 ◽  
Author(s):  
A. T. Bowden ◽  
P. Draper ◽  
H. Rowling
Keyword(s):  
Gas Turbines ◽  
Turbine Blades ◽  
Carbon Particle ◽  
Fuel Oil ◽  
Ash Deposition ◽  
Widespread Application ◽  
Fuel Droplets ◽  
Combustion Loss ◽  
Open Cycle

The loss of power due to the deposition of fuel-oil ash on the turbine blades at present limits the use of boiler fuels in open-cycle gas turbines, and therefore prevents the more widespread application of this form of prime mover in the marine and industrial fields. The nature and occurrence of the ash-forming constituents are discussed, followed by consideration of the possibilities of removal of these from the oil. There appears to be no solution along these lines nor by removal of the ash from the gas stream. The basic factors controlling deposition of ash are still not fully understood and therefore further experimental work is required. However, a method which gives a considerable reduction in deposition has been discovered. In this, combustion of the fuel droplets is controlled so that each droplet burns down and leaves the combustion chamber as a hard, dry, carbon particle containing an appreciable proportion of the ash. The combustion loss due to this unburnt carbon is less than 1 per cent. Long-term engine tests are now required to assess the practical use of the method. Another means of reducing deposition which appears to offer considerable promise is the use of various additives to the fuel or gas stream. Of those tested the oxides of silicon, zinc, and magnesium were the most effective.

scholarly journals Wear Characteristics of Superalloy and Hardface Coatings in Gas Turbine Applications–A Review

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1171
Author(s):  
Ahmad Afiq Pauzi ◽  
Mariyam Jameelah Ghazali ◽  
Wan Fathul Hakim W. Zamri ◽  
Armin Rajabi
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Turbine Blades ◽  
Research Field ◽  
Fatigue Wear ◽  
Hastelloy X ◽  
Hot Gas ◽  
Hard Particles ◽  
Critical Components ◽  
Improve Wear Resistance

In the gas-turbine research field, superalloys are some of the most widely used materials as they offer excellent strength, particularly at extreme temperatures. Vital components such as combustion liners, transition pieces, blades, and vanes, which are often severely affected by wear, have been identified. These critical components are exposed to very high temperatures (ranging from 570 to 1300 °C) in hot-gas-path systems and are generally subjected to heavy repair processes for maintenance works. Major degradation such as abrasive wear and fretting fatigue wear are predominant mechanisms in combustion liners and transition pieces during start–stop or peaking operation, resulting in high cost if inadequately protected. Another type of wear-like erosion is also prominent in turbine blades and vanes. Nimonic 263, Hastelloy X, and GTD 111 are examples of superalloys used in the gas-turbine industry. This review covers the development of hardface coatings used to protect the surfaces of components from wear and erosion. The application of hardface coatings helps reduce friction and wear, which can increase the lifespan of materials. Moreover, chromium carbide and Stellite 6 hardface coatings are widely used for hot-section components in gas turbines because they offer excellent resistance against wear and erosion. The effectiveness of these coatings to mitigate wear and increase the performance is further investigated. We also discuss in detail the current developments in combining these coating with other hard particles to improve wear resistance. The principles of this coating development can be extended to other high-temperature applications in the power-generation industry.

The Problem of Burning Residual Oils in Gas Turbines

1950 ◽  
Vol 163 (1) ◽  
pp. 206-220 ◽  
Author(s):  
P. Lloyd ◽  
R. P. Probert
Keyword(s):  
Gas Turbines ◽  
Turbine Blades ◽  
Solid Particles ◽  
Ash Deposition ◽  
Heavy Oils ◽  
Residual Oil ◽  
Secondary Effects ◽  
Efficient Combustion

The burning of residual oil fuels in gas turbines raises some special problems: the efficient combustion of the solid particles to which these fuels give rise, the avoidance of ash deposits, and the protection of turbine blades and other components from corrosion effects peculiar to these fuels. This lecture discusses these problems and the methods which are being considered for solving them. It is shown that the burning of these heavy oils is not the greatest of the difficulties, since with suitably designed equipment this process can be quite efficiently performed. What is difficult is the avoidance of ash deposition and of the secondary effects, notably blade corrosion, to which this deposition gives rise. These effects are considered in some detail.

Coating Effect on Particle Trajectories and Turbine Blade Erosion

1992 ◽  
Vol 114 (2) ◽  
pp. 250-257 ◽  
Author(s):  
W. Tabakoff ◽  
M. Metwally
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Protective Coatings ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Axial Flow ◽  
Coal Ash ◽  
Impact Angle ◽  
Laser Doppler Velocimeter ◽  
Particle Trajectories

Gas turbine engines operating in dusty environments are exposed to erosion and performance deterioration. In order to improve the erosion resistance, nickel and cobalt superalloy blades and vanes are widely used in the hot section of gas turbines. Protective coatings have been used to enhance superalloy resistance to hot erosion. An investigation has been conducted to study coal ash particle dynamics and resulting blade erosion for both uncoated and coated blades of a two-stage axial flow gas turbine. A quasi-three-dimensional flow solution is obtained for each blade row for accurate computation of particle trajectories. The change in particle momentum due to collision with the turbine blades and casings is modeled using restitution parameters derived from three-component laser-Doppler velocimeter measurements. The erosion models for both blade superalloy and coatings are derived based on the erosion data obtained by testing the blade superalloy and coatings in a high-temperature erosion wind tunnel. The results show both the three-dimensional particle trajectories and the resulting blade impact locations for both uncoated and coated blade surfaces. In addition are shown the distribution of the erosion rate, impact frequency, impact velocity, and impact angle for the superalloy and the coating. The results indicate significant effects of the coating, especially on blade erosion and material deterioration.

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