scholarly journals Crystal Viscoplasticity of a Ni-Base Superalloy in the Aged State

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
M. M. Kirka ◽  
R. W. Neu
Keyword(s):  
Gas Turbines ◽  
Internal State ◽  
Kinetic Equations ◽  
State Variables ◽  
Aging Effects ◽  
Directional Coarsening ◽  
Industrial Gas Turbines ◽  
Effects Of Aging ◽  
Base Superalloy

Arising from long-term high temperature service, the microstructure of nickel-base (Ni-base) superalloy components undergoes thermally and deformation-induced aging characterized by isotropic coarsening and directional coarsening (rafting) of the γ′ precipitates. The net result of the morphological evolutions of the γ′ particles is a deviation of the mechanical behavior from that of the as-heat treated properties. To capture the influence of a rafted and isotropic aged microstructure states on the long-term constitutive behavior of a Ni-base superalloy undergoing thermomechanical fatigue (TMF), a temperature-dependent crystal viscoplasticity (CVP) constitutive model is extended to include the effects of aging. The influence of aging in the CVP framework is captured through the addition of internal state variables that measure the widening of the γ channels and in-turn update the material parameters of the CVP model. Through the coupling with analytical derived kinetic equations to the CVP model, the enhanced CVP model is shown to be in good agreement when compared to experimental behavior in describing the long-term aging effects on the cyclic response of a directionally solidified (DS) Ni-base superalloy used in hot section components of industrial gas turbines.

An Improved Method for Evaluating Market Value of Turbine Gaspath Component Alternatives

2003 ◽  
Author(s):  
Fred T. Willett ◽  
Michael R. Pothier
Keyword(s):  
Power Plant ◽  
Gas Turbines ◽  
Net Present Value ◽  
Risk Level ◽  
Improved Method ◽  
Short Term ◽  
Plant Operator ◽  
Efficiency Increase ◽  
Industrial Gas Turbines

The large installed base of large frame industrial gas turbines has prompted a number of replacement part offerings, in addition to the replacement parts offered by the OEM. Willett [1] proposed an economic model developed to evaluate gas turbine component alternatives for base load and cyclic duty operation. The improved method expands the capability of the earlier model by including risk level as a variable. Power plant operator value of alternative replacement turbine components for a popular large frame industrial gas turbines is evaluated. A baseline case is established to represent the current component repair and replacement situation, assuming no risk. Each of the modes of power plant operation is evaluated from a long-term financial focus. A short-term financial focus is evaluated for contrast and discussed briefly. Long-term focus is characterized by a nine-year evaluation period, while short-term focus is based on first year benefit only. Four factors are varied: part price, output increase, simple cycle efficiency increase, and additional risk. Natural gas fuel is considered at two different gas prices. Peak, off-peak, and spot market electricity prices are considered. Results are calculated and compared using net present value (NPV) criteria. A case study is presented to demonstrate the method’s applicability to a range of different risk scenarios, from ill-fitting replacement parts to catastrophic turbine failure.

A Conceptual Design Study for a New High Temperature Fast Response Cooled Total Pressure Probe

2008 ◽  
Vol 131 (2) ◽  
Author(s):  
Jean-François Brouckaert ◽  
Mehmet Mersinligil ◽  
Marco Pau
Keyword(s):  
High Temperature ◽  
Gas Turbines ◽  
Total Pressure ◽  
Fast Response ◽  
Pressure Probe ◽  
Piezoresistive Pressure Sensor ◽  
Industrial Gas Turbines ◽  
Aero Engines ◽  
Harsh Conditions

The present paper proposes a concept for a water-cooled high temperature unsteady total pressure probe intended for measurements in the hot sections of industrial gas turbines or aero-engines. This concept is based on the use of a conventional miniature piezoresistive pressure sensor, which is located at the probe tip to achieve a bandwidth of at least 40 kHz. Due to extremely harsh conditions and the intention to immerse the probe continuously into the hot gas stream, the probe and sensor must be heavily cooled. The short term objective of this design is to gain the capability of performing measurements at the temperature conditions typically found at high pressure turbine exit (1100–1400 K) and in the long term at combustor exit (2000 K or higher).

A Conceptual Design Study for a New High Temperature Fast Response Cooled Total Pressure Probe

2008 ◽  
Author(s):  
Jean-Franc¸ois Brouckaert ◽  
Mehmet Mersinligil ◽  
Marco Pau
Keyword(s):  
High Temperature ◽  
Gas Turbines ◽  
Total Pressure ◽  
Fast Response ◽  
Pressure Probe ◽  
Industrial Gas Turbines ◽  
Aero Engines ◽  
Harsh Conditions ◽  
Term Objective

The present paper proposes a concept for a water cooled high temperature unsteady total pressure probe, intended for measurements in the hot sections of industrial gas turbines or aero-engines. This concept is based on the use of a conventional miniature piezo-resistive pressure sensor, located at the probe tip to achieve a bandwidth of at least 40kHz. Due to extremely harsh conditions and the intention to immerse the probe continuously into the hot gas stream, the probe and sensor must be heavily cooled. The short term objective of this design is to gain the capability of performing measurements at the temperature conditions typically found at high pressure turbine exit (1100–1400K) and in the long term at combustor exit (2000K or higher).

scholarly journals A Techno-Economic Computational Tool for Power Generation Project Assessments and Life Cycle Risk Management

1997 ◽  
Author(s):  
Stéphane Gayraud ◽  
Riti Singh
Keyword(s):  
Power Generation ◽  
Risk Management ◽  
Life Cycle ◽  
Risk Analysis ◽  
Gas Turbines ◽  
Life Cycle Cost ◽  
The Monte Carlo Method ◽  
Analysis Technique ◽  
Industrial Gas Turbines

The growing desire for sponsors of power generation projects to share risk with the lenders has promoted the use of computational tools, simulating and evaluating from a techno-economic viewpoint long-term, high-risk projects. Such models need to include reliable engine diagnostics, life-cycle costing and risk analysis technique. This paper presents a Decision Support System (DSS) for the assessment of power generation projects using industrial gas turbines. The software, programmed in Visual Basic in Excel, runs the object-oriented software Pythia which has been developed by the Department of Propulsion, Power and Automotive Engineering at Cranfield University and which can perform gas turbine performance calculations, including off-design conditions, with or without degradation effects providing thus very reliable engine diagnostics. Moreover, a life cycle cost, assessed using manufacturer methodology for instance, can be integrated into the economic model. The degree of uncertainty relating to technical and economic factors is assessed using a normal distribution and the level of risk can then be evaluated using a risk analysis technique based upon the Monte Carlo Method. The DSS therefore provides charts and result tables to support the decision making, allowing the user to achieve a good level of confidence using new techniques of risk management.

scholarly journals Chemical and physical aging of comets

1999 ◽  
Vol 173 ◽  
pp. 195-210 ◽  
Author(s):  
K.J. Meech
Keyword(s):  
Physical Aging ◽  
Activity Levels ◽  
Aging Effects ◽  
Water Ice ◽  
Crystalline Water ◽  
Comet Nuclei ◽  
Effects Of Aging ◽  
Physical Changes ◽  
Physical And Chemical

AbstractAging effects for comet nuclei encompass both chemical and physical changes to the nucleus which may be manifested as a change in the level of and type of activity that the nucleus experiences. Recent observations have shown the importance of the amorphous to crystalline water ice phase transition in comet nuclei for controlling activity at large distances, and for altering the porosity and volatile distribution in the interior of comets. Evidence for secular changes in activity levels or differences between dynamical classes of comets which have spent different amounts of time in the inner solar system must be decoupled from expected primordial differences between comets. Long-term observational programs by several groups have demonstrated that the effects of aging are detectable. This paper will discuss the expected primordial comet differences, the expected physical and chemical effects of aging, the techniques for observing differences in activity levels, and will present summaries of results of several observing programs.

scholarly journals Gas Turbine Operation Under Long Term PFB Conditions

1982 ◽  
Author(s):  
Ralph R. Boericke
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Coal Ash ◽  
Department Of Energy ◽  
Dust Particles ◽  
Fluidized Bed Combustion ◽  
Combustion Gases ◽  
Alkali Compounds ◽  
Industrial Gas Turbines

A key issue in pressurized fluidized bed combustion (PFBC) is the durability of the gas turbine when operated on combustion gases containing coal ash, attrited sorbent bed material, and corrosive alkali compounds. The tolerance of industrial gas turbines to erosion by dust particles has been estimated based on data from a variety of sources which are reviewed briefly in this paper. It is shown, based on experimental data, that conventional cyclones can remove sufficient dust particles to meet the projected turbine erosion tolerance. In addition, advanced clean-up devices under development by the U.S. Department of Energy which would effectively remove gas turbine erosion as an issue in PFBC are described. An overview of ongoing materials work is presented which summarizes recent experimental results and assesses the suitability of existing and new turbine alloys to survive this environment. Particular attention is given to a PFB Long Term Materials Test currently in progress which will demonstrate materials corrosion resistance for exposure times up to 14,000 hr. Preliminary results from this test are discussed.

Effects of Aging on the Subcortical Encoding of Stop Consonants

2020 ◽  
Vol 29 (3) ◽  
pp. 391-403
Author(s):  
Dania Rishiq ◽  
Ashley Harkrider ◽  
Cary Springer ◽  
Mark Hedrick
Keyword(s):  
Older Adults ◽  
Repeated Measures ◽  
Mixed Model ◽  
Auditory Brainstem ◽  
Auditory Brainstem Responses ◽  
Aging Effects ◽  
Formant Frequency ◽  
Place Of Articulation ◽  
Second Formant ◽  
Effects Of Aging

Purpose The main purpose of this study was to evaluate aging effects on the predominantly subcortical (brainstem) encoding of the second-formant frequency transition, an essential acoustic cue for perceiving place of articulation. Method Synthetic consonant–vowel syllables varying in second-formant onset frequency (i.e., /ba/, /da/, and /ga/ stimuli) were used to elicit speech-evoked auditory brainstem responses (speech-ABRs) in 16 young adults ( M age = 21 years) and 11 older adults ( M age = 59 years). Repeated-measures mixed-model analyses of variance were performed on the latencies and amplitudes of the speech-ABR peaks. Fixed factors were phoneme (repeated measures on three levels: /b/ vs. /d/ vs. /g/) and age (two levels: young vs. older). Results Speech-ABR differences were observed between the two groups (young vs. older adults). Specifically, older listeners showed generalized amplitude reductions for onset and major peaks. Significant Phoneme × Group interactions were not observed. Conclusions Results showed aging effects in speech-ABR amplitudes that may reflect diminished subcortical encoding of consonants in older listeners. These aging effects were not phoneme dependent as observed using the statistical methods of this study.

Fuel System Suitability Considerations for Industrial Gas Turbines

2004 ◽  
Vol 126 (1) ◽  
pp. 119-126 ◽  
Author(s):  
F. G. Elliott ◽  
R. Kurz ◽  
C. Etheridge ◽  
J. P. O’Connell
Keyword(s):  
Gas Turbines ◽  
Equations Of State ◽  
Dew Point ◽  
Liquid Fuels ◽  
Physical Parameters ◽  
Special Focus ◽  
Fuel System ◽  
Fuel Gas ◽  
Pressure Drops ◽  
Industrial Gas Turbines

Industrial Gas Turbines allow operation with a wide variety of gaseous and liquid fuels. To determine the suitability for operation with a gas fuel system, various physical parameters of the proposed fuel need to be determined: heating value, dew point, Joule-Thompson coefficient, Wobbe Index, and others. This paper describes an approach to provide a consistent treatment for determining the above physical properties. Special focus is given to the problem of determining the dew point of the potential fuel gas at various pressure levels. A dew point calculation using appropriate equations of state is described, and results are presented. In particular the treatment of heavier hydrocarbons, and water is addressed and recommendations about the necessary data input are made. Since any fuel gas system causes pressure drops in the fuel gas, the temperature reduction due to the Joule-Thompson effect has to be considered and quantified. Suggestions about how to approach fuel suitability questions during the project development and construction phase, as well as in operation are made.

scholarly journals An extension of Gronwall inequality in the theory of bodies with voids

Open Physics ◽  
2020 ◽  
Vol 18 (1) ◽  
pp. 1161-1167
Author(s):  
Marin Marin ◽  
Praveen Ailawalia ◽  
Ioan Tuns
Keyword(s):  
Boundary Value Problem ◽  
Internal State ◽  
Boundary Value ◽  
Initial Boundary ◽  
Initial Boundary Value Problem ◽  
Uniqueness Result ◽  
Internal Variables ◽  
State Variables ◽  
Gronwall’S Inequality ◽  
Initial Boundary Value

Abstract In this paper, we obtain a generalization of the Gronwall’s inequality to cover the study of porous elastic media considering their internal state variables. Based on some estimations obtained in three auxiliary results, we use this form of the Gronwall’s inequality to prove the uniqueness of solution for the mixed initial-boundary value problem considered in this context. Thus, we can conclude that even if we take into account the internal variables, this fact does not affect the uniqueness result regarding the solution of the mixed initial-boundary value problem in this context.

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