Gas Turbine Failure due to Water Wash and Extraction Line Blockage

2011 ◽  
Author(s):  
Abdulmajeed A. Ali
Keyword(s):  
Combustion Chamber ◽  
Operation Mode ◽  
Turbine Blades ◽  
Root Cause ◽  
Hot Gas ◽  
Subsequent Investigation ◽  
Exhaust Stream ◽  
The Subject ◽  
Air Passage ◽  
Interlock System

A Hot Gas Path Inspection (HGPI) of GE Co-Generation train revealed an extensive failure of the turbine blades and vanes in the first, second, third stages and combustion chamber cross firing tubes. Subsequent investigation effort indicated that commissioning activities of associated compressor water wash system allowed large volumes of water to penetrate the compressor and combustion chamber due to improper instrumentation interlock configuration of MOV-20TW-1 (Offline compressor water wash motor operated valve) and MOV-20TW-3 (Online compressor water wash motor operated valve). The field wiring for the valves was incorrectly interchanged causing the offline water wash valves to be operated while commanding the online water wash valves to operate and vice-versa. Compressor water wash system is typically used to remove fouling deposits from compressor components to maintain the equipment efficiency, power output and reduce corrosion rate. Vendor recommends daily online water wash while the offline water wash shall be performed whenever the equipment is not working. As a result, cross firing tubes were exposed to sudden quenching during the water wash activities causing tube fragmentation, which found its way through the exhaust stream to the turbine chamber — colliding with associated buckets and nozzles — eventually resulting in the reported damage. Water seeped into the air extraction line and settled in the dryer skid system, resulting in desiccant contamination. Following turbine shutdown for correcting the instrumentation loop configurations of subject MOVs, the contaminated desiccant flowed to the combustion chamber, blocking the extraction line and the drain lines. After successful configuration of compressor water wash system MOVs, the turbine was put back in operation mode. The contaminated desiccant blocked the air passage of the combustion chamber, which consequently melted the cross firing tubes and contributed to the overheating of first stage buckets. Investigation concluded that the inadequate pre-commissioning procedure — for the Co-Generation train compressor water wash interlock system — were the root cause behind the subject incident. The immediate cause was determined to be water penetration to the compressors and combustion chamber internals during machine operation.

M. V. Nadkarni. Farmer's Movements in India. New Delhi: Allied Publishers Pvt. Ltd., 1987.237 pp.,Price: (hardbound edition) Rupees (Indian) 100.00.

1988 ◽  
Vol 27 (3) ◽  
pp. 333-335
Author(s):  
Khwaja Sarmad
Keyword(s):  
Tamil Nadu ◽  
Rural Poverty ◽  
Price Policy ◽  
New Delhi ◽  
Root Cause ◽  
The Subject ◽  
The Rich ◽  
Land Holdings ◽  
Set Up ◽  
Agricultural Price

This book is a comprehensive analysis of farmers' movements in India with a focus on the movements in Tamil Nadu, Maharashtra, Punjab and Karnatka. It examines the economic, social and political aspects of the farmers' struggle for a better deal within regional and national perspectives and evaluates the potential impact of these struggles on economic development in general, and on rural development, in particular. In a most competent way the author has presented the current state of the debate on the subject. He deals exhaustively with the subject of agricultural price policy and argues against the proposition that favourable price-setting for farm products is adequate to alleviate rural poverty. A better way to tackle this problem is to improve the per capita output in the rural sector, since the root cause of the problem is not unfavourable terms of trade but the increasing proportion of land holdings, which are economically not viable. Agricultural price policy is analyzed within the context of class relations, which enables to establish a link between the economic and political demands of the farmers. This analysis leads the author to conclude, that in contrast with the peasants' movements in India, which helped to break up the feudal agrarian set-up, the recent farmers' movements, with a few exceptions, have little revolutionary content. Their leadership has been appropriated by the rich landowners, who have transformed the movements into a lobby for advancing their own interests, within the existing power structure, to the neglect of the poorer peasantry.

Art. VIII.—On the Origin of the Ancient Northern Constellation-figures

1897 ◽  
Vol 29 (2) ◽  
pp. 205-226
Author(s):  
Robert Brown
Keyword(s):  
The South ◽  
Future Time ◽  
Classic Work ◽  
Careful Observation ◽  
Subsequent Investigation ◽  
Correct Conclusion ◽  
Western Asia ◽  
The World ◽  
The Subject ◽  
Euphrates Valley

Amongst the most remarkable instances of the result of careful observation and systematized thought which Western Asia has given to the world at large, are the Signs of the Zodiac, and the ancient extra-zodiacal constellation-figures, northern and southern; and by ‘ancient’ I mean those which have been enshrined for all future time in the Phainomena of Aratos. Of the Twelve Signs I shall only speak incidentally. It is now many years since Ideler and Guigniaut, contrary to the views of Letronne, arrived at the correct conclusion that the Signs of the Zodiac came, with so much else of archaic thought and civilization, from, the Euphrates Valley; and, having firmly established themselves in Hellenic usage, were afterwards carried by Greek conquerors as far as India in the east and Egypt in the south. But, although modern research has supplied an immense amount of material for the purpose, it is remarkable that the classic work of Ideler still gives the best account of the constellation-figures and their various stars. Surely, then, it is time that an effort was made to utilize in a connected form some at least of the results of subsequent investigation; and, although the inquiry, like all such, is progressive, and, like all researches into the ancient and archaic past, is beset with numerous difficulties, yet the principles to be applied and the general outlines of the subject are clear and distinct.

Root Cause Analysis of SI Nozzle Thermal Sleeve Breakaway Failures Occurring at PWR Plants

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Jong Chull Jo ◽  
Myung Jo Jhung ◽  
Seon Oh Yu ◽  
Hho Jung Kim ◽  
Young Gill Yune
Keyword(s):  
Cold Water ◽  
Operation Mode ◽  
Branch Pipe ◽  
Thin Wall ◽  
Reactor Operation ◽  
Support Condition ◽  
Primary Coolant ◽  
Root Cause ◽  
Main Pipe ◽  
Flow Situation

At conventional pressurized water reactors (PWRs), cold water stored in the refueling water tank of emergency core cooling system is injected into the primary coolant system through a safety injection (SI) line, which is connected to each cold leg pipe between the main coolant pump and the reactor vessel during the SI operation, which begins on the receipt of a loss of coolant accident signal. In normal reactor power operation mode, the wall of SI line nozzle maintains at high temperature because it is the junction part connected to the cold leg pipe through which the hot main coolant flows. To prevent and relieve excessive transient thermal stress in the nozzle wall, which may be caused by the direct contact of cold water in the SI operation mode, a thermal sleeve in the shape of thin wall cylinder is set in the nozzle part of each SI line. Recently, mechanical failures that the sleeves are separated from the SI branch pipe and fall into the connected cold leg main pipe occurred in sequence at some typical PWR plants in Korea. To find out the root cause of thermal sleeve breakaway failures, the flow situation in the junction of primary coolant main pipe-SI branch pipe and the vibration modal characteristics of the thermal sleeve are investigated in detail by using both computational fluid dynamics code and structure analysis finite element code. As a result, the transient response in fluid pressure exerting on the local part of thermal sleeve wall surface to the primary coolant flow through the pipe junction area during the normal reactor operation mode shows oscillatory characteristics with the frequencies ranging from 15Hzto18Hz. These frequencies coincide with the lower mode natural frequencies of thermal sleeve, which has a pinned support condition on the outer surface with the circumferential prominence set into the circumferential groove on the inner surface of SI nozzle at the midheight of thermal sleeve. In addition, the variation of pressure on the thermal sleeve surface yields alternating forces and torques in the directions of two rectangular axes perpendicular to the longitudinal axis of cylindrical thermal sleeve, which causes both rolling and pitching motions of the thermal sleeve. Consequently, it is seen that this flow situation surrounding the thermal sleeve during the normal reactor operation can induce resonant vibrations accompanying the shaking motion of the thermal sleeve at the pinned support condition, which finally leads to the failures of thermal sleeve breakaway from the SI nozzle.

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.

Cooling of Turbine Blades With Expanded Exit Holes: Computational Analyses of Leading Edge and Pressure-Side of a Turbine Blade

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Fariborz Forghan ◽  
Omid Askari ◽  
Uichiro Narusawa ◽  
Hameed Metghalchi
Keyword(s):  
High Speed ◽  
Turbine Blades ◽  
Leading Edge ◽  
Weak Shock ◽  
Suction Side ◽  
Pressure Side ◽  
Blade Surface ◽  
Cooling Effectiveness ◽  
Hot Gas ◽  
Computational Analyses

Turbine blades are cooled by a jet flow from expanded exit holes (EEH) forming a low-temperature film over the blade surface. Subsequent to our report on the suction-side (low-pressure, high-speed region), computational analyses are performed to examine the cooling effectiveness of the flow from EEH located at the leading edge as well as at the pressure-side (high-pressure, low-speed region). Unlike the case of the suction-side, the flow through EEH on the pressure-side is either subsonic or transonic with a weak shock front. The cooling effectiveness, η (defined as the temperature difference between the hot gas and the blade surface as a fraction of that between the hot gas and the cooling jet), is higher than the suction-side along the surface near the exit of EEH. However, its magnitude declines sharply with an increase in the distance from EEH. Significant effects on the magnitude of η are observed and discussed in detail of (1) the coolant mass flow rate (0.001, 0.002, and 0.004 (kg/s)), (2) EEH configurations at the leading edge (vertical EEH at the stagnation point, 50 deg into the leading-edge suction-side, and 50 deg into the leading-edge pressure-side), (3) EEH configurations in the midregion of the pressure-side (90 deg (perpendicular to the mainstream flow), 30 deg EEH tilt toward upstream, and 30 deg tilt toward downstream), and (4) the inclination angle of EEH.

Development of a Coal Fired Pressurized Fluidized Bed for Combined Cycle Power Generation

1980 ◽  
Author(s):  
S. Moskowitz ◽  
G. Weth ◽  
A. Leon
Keyword(s):  
Fluidized Bed ◽  
Large Scale ◽  
Technology Development ◽  
Turbine Blades ◽  
Combined Cycle ◽  
Test Time ◽  
Test Program ◽  
Hot Gas ◽  
Fluid Bed ◽  
Electric Plant

A program to design, construct and operate a pilot electric plant using a pressurized fluidized bed (PFB) combustor burning high sulfur coal to produce electricity at competitive costs and in an environmentally acceptable manner is proceeding under DOE sponsorship. Three components were identified needing experimental test data to validate the selected design configurations or material selections. These components included: (a) PFB in-bed heat exchanger tubes, (b) hot gas cleanup system, and (c) turbine blades. R&D test programs utilizing laboratory rigs, commercial fluid bed reactors, and a large scale PFB technology rig were conducted for a cumulative test time of over 10,000 hr. Design criteria and configurations were selected and verified. This paper presents the results of the technology development presents the results of the technology development tests. Also, the large scale PFB technology rig design and test program are presented. The results of operating a small gas turbine coupled to the PFB combustor and hot gas cleanup system within this technology rig are discussed.

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.

Thermodynamics Cycle Analysis, Pressure Loss and Heat Transfer Assessment of a Recuperative System for Aero Engines

2014 ◽  
Author(s):  
A. Goulas ◽  
S. Donnerhack ◽  
M. Flouros ◽  
D. Misirlis ◽  
Z. Vlahostergios ◽  
...  
Keyword(s):  
Combustion Chamber ◽  
Fuel Consumption ◽  
Heat Exchangers ◽  
Engine Performance ◽  
Specific Fuel Consumption ◽  
Hot Gas ◽  
Research Activities ◽  
Aero Engine ◽  
Overall Efficiency ◽  
Aero Engines

Aiming in the direction of designing more efficient aero engines, various concepts have been developed in recent years, among which is the concept of an intercooled and recuperative aero engine. Particularly in the area of recuperation, MTU Aero Engines has been driving research activities in the last decade. This concept is based on the use of a system of heat exchangers mounted inside the hot-gas exhaust nozzle (recuperator). Through the operation of the system of heat exchangers, the heat from the exhaust gas, downstream the LP turbine of the jet engine is driven back to the combustion chamber. Thus, the preheated air enters the engine combustion chamber with increased enthalpy, providing improved combustion and by consequence, increased fuel economy and low-level emissions. If additionally an intercooler is placed between the compressor stages of the aero engine, the compressed air is then cooled by the intercooler thus, less compression work is required to reach the compressor target pressure. In this paper an overall assessment of the system is presented with particular focus on the recuperative system and the heat exchangers mounted into the aero engine’s exhaust nozzle. The herein presented results were based on the combined use of CFD computations, experimental measurements and thermodynamic cycle analysis. They focus on the effects of total pressure losses and heat exchanger efficiency on the aero engine performance especially the engine’s overall efficiency and the specific fuel consumption. More specifically, two different hot-gas exhaust nozzle configurations incorporating modifications in the system of heat exchangers are examined. The results show that significant improvements can be achieved in overall efficiency and specific fuel consumption hence contributing into the reduction of CO2 and NOx emissions. The design of a more sophisticated recuperation system can lead to further improvements in the aero engine efficiency in the reduction of fuel consumption. This work is part of the European funded research program LEMCOTEC (Low Emissions Core engine Technologies).

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.

Effect of Internal Coolant Crossflow on the Effectiveness of Shaped Film-Cooling Holes

2003 ◽  
Vol 125 (3) ◽  
pp. 547-554 ◽  
Author(s):  
Michael Gritsch ◽  
Achmed Schulz ◽  
Sigmar Wittig
Keyword(s):  
Film Cooling ◽  
Gas Flow ◽  
Flow Direction ◽  
Turbine Blades ◽  
Density Ratio ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Hot Gas ◽  
Wide Range

Film-cooling was the subject of numerous studies during the past decades. However, the effect of flow conditions on the entry side of the film-cooling hole on film-cooling performance has surprisingly not received much attention. A stagnant plenum which is widely used in experimental and numerical studies to feed the holes is not necessarily a right means to re-present real engine conditions. For this reason, the present paper reports on an experimental study investigating the effect of a coolant crossflow feeding the holes that is oriented perpendicular to the hot gas flow direction to model a flow situation that is, for instance, of common use in modern turbine blades’ cooling schemes. A comprehensive set of experiments was performed to evaluate the effect of perpendicular coolant supply direction on film-cooling effectiveness over a wide range of blowing ratios (M=0.5…2.0) and coolant crossflow Mach numbers Mac=0…0.6. The coolant-to-hot gas density ratio, however, was kept constant at 1.85 which can be assumed to be representative for typical gas turbine applications. Three different hole geometries, including a cylindrical hole as well as two holes with expanded exits, were considered. Particularly, two-dimensional distributions of local film-cooling effectiveness acquired by means of an infrared camera system were used to give detailed insight into the governing flow phenomena. The results of the present investigation show that there is a profound effect of how the coolant is supplied to the hole on the film-cooling performance in the near hole region. Therefore, crossflow at the hole entry side has be taken into account when modeling film-cooling schemes of turbine bladings.

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