The Effect of Ca-Rich Deposits on the High Temperature Degradation of Coated and Uncoated Superalloys

2008 ◽  
Vol 595-598 ◽  
pp. 805-812 ◽  
Author(s):  
Kee Young Jung ◽  
Frederick S. Pettit ◽  
Gerald H. Meier
Keyword(s):  
Gas Turbines ◽  
Cyclic Oxidation ◽  
Alternative Fuels ◽  
Coal Ash ◽  
Mineral Matter ◽  
Type I ◽  
Platinum Aluminide ◽  
Alternate Fuels ◽  
Different Characteristics ◽  
Type Ii Hot Corrosion

When gas turbines use alternate fuels, such as syngas derived from coal, ash from the fuels can deposit on turbine hardware. These deposits can cause substantial corrosion of the hardware which may have significantly different characteristics than Type I and Type II hot corrosion. The composition of the ash is determined by the mineral matter in coals, which often have kaolinite (Al2O3·2SiO2·2H2O), pyrites (FeS2), and calcites (CaCO3) as major components. This study was directed at degradation produced by CaO and CaSO4 and comparing it with the attack induced by Na2SO4 deposits. The alloys GTD 111, IN 738, and René N5, as well as these alloys coated with CoNiCrAlY and platinum aluminide, were exposed to conditions relevant to corrosion induced using alternative fuels. The initial test conditions involved a number of deposits including Na2SO4, CaO, and CaSO4 in dry and wet (pH2O = 10.1 kPa, 0.1 atm) air at 950oC. The most severe degradation occurred with CaO deposits. Specimens of the three alloys were subsequently exposed to cyclic oxidation conditions at 950oC with deposits of CaO in dry and wet air. All three alloys were attacked more severely when CaO deposits were present and this attack became even more severe in wet compared to dry air. However, the increase in attack caused by the presence of water vapor was small compared to the attack caused by the CaO deposits. The degradation induced via CaO deposits caused more severe degradation of René N5 compared to GTD 111 and IN 738. Tests using CaO deposits and cyclic oxidation conditions at 950oC in dry and wet air were also performed for the two coatings on the three alloy substrates. Both coatings were significantly degraded by attack induced by the CaO deposits. No effect of the alloy substrates on coating performance was apparent. Mechanisms for the effects of Ca-rich deposits on superalloy and coating degradation are discussed.

scholarly journals INVESTIGATION ON THE PERFORMANCE OF FLAXSEED BIODIESEL BLENDS WITH TIO2 COATED PISTON ON A FOUR STROKE DI DIESEL ENGINE

2017 ◽  
Vol 46 (1) ◽  
pp. 49-53
Author(s):  
R. Bhaskar Reddy ◽  
S. Sunilkumar Reddy
Keyword(s):  
Combustion Chamber ◽  
Fuel Economy ◽  
Diesel Engines ◽  
Canola Oil ◽  
Alternative Fuels ◽  
Flaxseed Oil ◽  
Suitable Alternative ◽  
Petroleum Resources ◽  
Di Diesel Engine ◽  
Alternate Fuels

Diesel engines are being used extensively for fuel economy but due to gradual depletion of Petroleum resources and increase in exhaust emissions, there is an urgent need for suitable alternative fuels for the diesel engines. As our country is an agricultural country, if the alternate fuels are produced by our farmers it will be beneficial for the country and the farmers also. In recent studies, researchers studied various vegetable oils like canola oil, alovera oil, soya been oil, flaxseed oil and hone oil etc. Out of all flaxseed oil play an important role as an alternative fuel. But the properties of flaxseed oil are not suitable for the usage in the existing diesel engines without blending with diesel fuel. The performance of the engine depends on the combustion phenomenon and it further depends on the amount of heat retained in the combustion chamber. Hence the present work is planned accordingly to develop an insulated engine by coating the piston with TIO2material. So that more amount of heat will be retained in the combustion chamber which aids the combustion. Further the performance of flaxseedbiodiesel blend namely B10, B20, B30 and B40 are tested and the results are mentioned accordingly.

Comparison Between Two-Shaft Simple and Single-Shaft Recuperated Brayton Cycles Using Different Types of Gaseous Fuels

2010 ◽  
Author(s):  
A. K. Malkogianni ◽  
A. Tourlidakis ◽  
A. L. Polyzakis
Keyword(s):  
Natural Gas ◽  
Gas Turbines ◽  
Alternative Fuels ◽  
High Efficiency ◽  
Heating Value ◽  
Gaseous Fuels ◽  
Oil And Natural Gas ◽  
Parametric Studies ◽  
The Impact ◽  
Lower Heating

Geopolitical issues give rise to problems in the smooth and continuous flow of oil and natural gas from the production countries to the consumers’ development countries. In addition, severe environmental issues such as greenhouse gas emissions, eventually guide the consumers to fuels more suitable to the present situation. Alternative fuels such as biogas and coal gas have recently become more attractive because of their benefits, especially for electricity generation. On the other hand, the use of relatively low heating value fuels has a significant effect to the performance parameters of gas turbines. In this paper, the impact of using four fuels with different heating value in the gas turbine performance is simulated. Based on the high efficiency and commercialization criteria, two types of engines are chosen to be simulated: two-shaft simple and single-shaft recuperated cycle gas turbines. The heating values of the four gases investigated, correspond to natural gas and to a series of three gases with gradually lower heating values than that of natural gas. The main conclusions drawn from this design point (DP) and off-design (OD) analysis is that, for a given TET, efficiency increases for both engines when gases with low heating value are used. On the contrary, when power output is kept constant, the use of gases with low heating value will result in a decrease of thermal efficiency. A number of parametric studies are carried out and the effect of operating parameters on performance is assessed. The analysis is performed with customized software, which has been developed for this purpose.

scholarly journals Alternate Fuels and the Gas Turbine Catalytic Combustor

1979 ◽  
Author(s):  
W. C. Pfefferle
Keyword(s):  
Nitrogen Oxides ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Soot Formation ◽  
Raw Materials ◽  
Tar Sands ◽  
Aromatic Content ◽  
Percent Conversion ◽  
Catalytic Combustor ◽  
Alternate Fuels

Inasmuch as conventional gas turbine combustors often produce soot even with the present low aromatic content fuels, the production of acceptable liquid turbine fuels from hydrogen deficient raw materials such as coal and tar sands requires large quantities of high cost hydrogen if conventional combustors are to be used. The economics of producing alternate turbine fuels would be improved if high aromatic content fuels could be burned in gas turbines without soot formation. Gas turbines using the catalytic combustor not only can efficiently burn highly aromatic fuels without soot formation but can meet all existing or proposed regulations on emissions of hydrocarbons, carbon monoxide, and nitrogen oxides. Under certain conditions, high fuels can be burned with as little as 10 to 15 percent conversion of the fuel nitrogen to nitrogen oxides. In view of the potential savings, any program for alternate fuels should take into account the opportunities offered by the catalytic combustor.

Ash Behavior During Combustion and Deposition in Coal-Fueled Gas Turbines

1987 ◽  
Vol 109 (3) ◽  
pp. 325-330 ◽  
Author(s):  
C. L. Spiro ◽  
S. G. Kimura ◽  
C. C. Chen
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Alkali Metals ◽  
Coal Ash ◽  
Water Mixture ◽  
Corrosion Rates ◽  
Petroleum Fuels

Chemical and physical transformations of coal ash during combustion and deposition in gas turbine environments have been studied. Extensive characterization of the coal-water mixture fuel and deposits obtained on deposition pins and turbine nozzle vanes has been performed. The behavior of alkali metals has been found to be much different from that for petroleum fuels, resulting in lower than expected deposition and probable reduced corrosion rates.

Experimental and numerical study of flame structure and emissions in a micro gas turbine combustor

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Vedant Dwivedi ◽  
Srikanth Hari ◽  
S. M. Kumaran ◽  
B. V. S. S. S. Prasad ◽  
Vasudevan Raghavan
Keyword(s):  
Gas Turbine ◽  
Rural Areas ◽  
Gas Turbines ◽  
Alternative Fuels ◽  
Numerical Study ◽  
Operating Conditions ◽  
Emission Characteristics ◽  
Nitric Oxides ◽  
Gas Turbine Combustor ◽  
Micro Gas Turbine

Abstract Experimental and numerical study of flame and emission characteristics in a tubular micro gas turbine combustor is reported. Micro gas turbines are used for distributed power (DP) generation using alternative fuels in rural areas. The combustion and emission characteristics from the combustor have to be studied for proper design using different fuel types. In this study methane, representing fossil natural gas, and biogas, a renewable fuel that is a mixture of methane and carbon-dioxide, are used. Primary air flow (with swirl component) and secondary aeration have been varied. Experiments have been conducted to measure the exit temperatures. Turbulent reactive flow model is used to simulate the methane and biogas flames. Numerical results are validated against the experimental data. Parametric studies to reveal the effects of primary flow, secondary flow and swirl have been conducted and results are systematically presented. An analysis of nitric-oxides emission for different fuels and operating conditions has been presented subsequently.

Combustion Characteristics of Isolated Free-Falling Droplets of Jet A Blended With Ethanol and Butanol

2018 ◽  
Author(s):  
Álvaro Muelas ◽  
Pilar Remacha ◽  
Javier Ballester
Keyword(s):  
Gas Turbines ◽  
Alternative Fuels ◽  
Droplet Diameter ◽  
Combustion Process ◽  
Combustion Characteristics ◽  
Shell Size ◽  
Pure Ethanol ◽  
Promising Alternative ◽  
Burning Rates ◽  
Alcohol Mixtures

Recent studies on experimental gas turbines suggest that the addition of ethanol or butanol to Jet A are viable alternatives for reducing CO and NOx emissions while maintaining similar performance to that of pure Jet A. In light of this potential, experimental data regarding the burning characteristics of Jet A/ethanol and Jet A/butanol blends are required in order to better understand their combustion process. Following a previous study on Jet A/butanol droplet combustion, the scope has been extended in order to also include ethanol and a Jet A/ethanol mixture as well as to perform a more detailed characterization. In this work the combustion characteristics of Jet A, butanol, ethanol and their mixtures (20% vol. alcohol in kerosene) are presented for different test conditions. The evaluated combustion characteristics include droplet, flame and soot shell size evolutions, burning rates and image-based soot estimations. The influence of oxygen availability is also ascertained. The evolution of droplet diameter and burning rates for Jet A and its blends with both alcohols are very similar, whereas pure ethanol and butanol display more distinct behaviors. Soot indices are found to be quite different, with a clear reduction in the sooting propensity of the Jet A/alcohol mixtures when compared to neat kerosene. These results support the feasibility of kerosene-alcohol mixtures as promising alternative fuels with similar combustion characteristics, but with much lower sooting propensity than pure kerosene.

Evaluating Materials and Fuels Using an Atmospheric-Pressure Low-Velocity Burner Rig: Factors to Consider to Avoid Unintended Consequences

2012 ◽  
Author(s):  
David A. Shifler ◽  
Louis F. Aprigliano ◽  
Dan Groghan
Keyword(s):  
Atmospheric Pressure ◽  
Gas Turbines ◽  
Alternative Fuels ◽  
Energy Content ◽  
Full Range ◽  
Unintended Consequences ◽  
Low Velocity ◽  
Accelerated Corrosion ◽  
Operational Conditions ◽  
Gaseous Products

The availability of petroleum-derived fuels is declining and the cost of petroleum can fluctuate wildly from $60 to $140 per barrel. These factors are causing a global desire to develop and use alternative fuels. While hydrogen, ethanol, and other non-hydrocarbon fuels are practical alternative fuels for the commercial sector, only liquid hydrocarbons meet the stringent needs of the military in terms of energy content, safety, handling and multi-platform use over the full range of operational conditions. Synthetic fuels will need to meet the current Naval petroleum-based physical, combustion, and chemistry specifications. Therefore, these fuels must be certified to meet Navy requirements and not have an adverse impact on current engine lives or performance. It has been established that low-velocity, atmospheric-pressure burner rigs, when operated properly, simulate the corrosion and degradation of materials operating in Navy shipboard gas turbines. To evaluate new fuels to determine whether or not they will cause accelerated corrosion in a gas turbine, the corrosion of standard coated superalloys representative of materials in the hot section of gas turbines are exposed to the combustion gaseous products of the new fuels or fuel blends in the burner rig and compared to that of a standard Navy fuel. The control of parameters in all tests is critical if proper evaluation and interpretation is to be achieved. Failure to control the parameters leads to questions that could require more testing or deliver unsupportable, indeterminate conclusions. Two case studies will be presented on how these principles were used to conduct successful burner rig tests and how the learning from those cases were applied to make a decision as to how to conduct an alternate fuels test in a third case.

Alternative Fuels in Gas Turbine Applications: A Simple Method for Assessing the Influence of Fuel on Performances

2000 ◽  
Author(s):  
Michel Molière ◽  
Frédéric Pommel
Keyword(s):  
Gas Turbines ◽  
Alternative Fuels ◽  
Differential Method ◽  
Simple Method ◽  
Gas Condensates ◽  
Exhaust Heat ◽  
Petroleum Distillates ◽  
Output Efficiency ◽  
The Many ◽  
The Impact

Gas turbines have by essence access to a broad range of primary energies. This advantage is essentially exploitable by the Heavy Duty branch which, thanks to moderate compression ratios, robust mechanical designs and versatile combustion systems, can utilise a wide series of commercial and process by-products fuels: natural gas, petroleum distillates, gasified coal or biomass, gas condensates, ash-forming fuels, alcohols etc. In this context, a thorough knowledge of the many-facetted fuel/machine interdependency, which seems insufficiently covered by the existing literature on gas turbines, is of prime interest. This paper is devoted to the thermodynamic aspects of fuel influence. It offers: (i) a review of the main primary energies accessible to stationary gas turbines, (ii) a new, differential method for assessing the impact of fuel on machine thermodynamics, with original equations accounting for the changes in power output, efficiency and exhaust heat.

Effects of Surface Deposition, Hole Blockage, and Thermal Barrier Coating Spallation on Vane Endwall Film Cooling

2006 ◽  
Vol 129 (3) ◽  
pp. 599-607 ◽  
Author(s):  
N. Sundaram ◽  
K. A. Thole
Keyword(s):  
Thermal Barrier Coating ◽  
Film Cooling ◽  
Gas Turbines ◽  
Large Scale ◽  
Leading Edge ◽  
Thermal Barrier ◽  
Cooling Effectiveness ◽  
Barrier Coating ◽  
Cooling Hole ◽  
Alternate Fuels

With the increase in usage of gas turbines for power generation and given that natural gas resources continue to be depleted, it has become increasingly important to search for alternate fuels. One source of alternate fuels is coal derived synthetic fuels. Coal derived fuels, however, contain traces of ash and other contaminants that can deposit on vane and turbine surfaces affecting their heat transfer through reduced film cooling. The endwall of a first stage vane is one such region that can be susceptible to depositions from these contaminants. This study uses a large-scale turbine vane cascade in which the following effects on film cooling adiabatic effectiveness were investigated in the endwall region: the effect of near-hole deposition, the effect of partial film cooling hole blockage, and the effect of spallation of a thermal barrier coating. The results indicated that deposits near the hole exit can sometimes improve the cooling effectiveness at the leading edge, but with increased deposition heights the cooling deteriorates. Partial hole blockage studies revealed that the cooling effectiveness deteriorates with increases in the number of blocked holes. Spallation studies showed that for a spalled endwall surface downstream of the leading edge cooling row, cooling effectiveness worsened with an increase in blowing ratio.

scholarly journals Improved Particle Trajectory Calculations Through Turbomachinery Affected by Coal Ash Particles

1981 ◽  
Author(s):  
B. Beecher ◽  
W. Tabakoff ◽  
A. Hamed
Keyword(s):  
Flow Field ◽  
Gas Turbines ◽  
Three Dimensional ◽  
Coal Ash ◽  
Two Dimensional ◽  
Flow Properties ◽  
Trajectory Calculations ◽  
Blade Thickness ◽  
Spline Fitting ◽  
Numerical Grid

Trajectories of small coal ash particles encountered in coal-fired gas turbines are calculated with an improved computer analysis currently under development. The analysis uses an improved numerical grid and mathematical spline-fitting techniques to account for three-dimensional gradients in the flow field and blade geometry. The greater accuracy thus achieved in flow field definition improves the trajectory calculations over previous two-dimensional models by allowing the small particles to react to radial variations in the flow properties. A greater accuracy thus achieved in the geometry definition permits particle rebounding in a direction perpendicular to the blade and flow path surfaces rather than in a two-dimensional plane. The improved method also accounts for radial variations in airfoil chord, stagger, and blade thickness when computing particle impact at a blade location.

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