Investigations Into Creep Behavior of Gas Turbine Component Assemblies

2012 ◽  
Author(s):  
Kotur S. Raghavan
Keyword(s):  
Nonlinear Analysis ◽  
Gas Turbines ◽  
Material Selection ◽  
Rupture Life ◽  
Compressive Force ◽  
Design Stage ◽  
Creep Properties ◽  
Threaded Fasteners ◽  
Parametric Studies ◽  
Joint Behavior

Modern day gas turbines are very complex in construction and consist of a very large number of smaller parts and subassemblies. Hence the most vital parts of the entire assembly are the mechanical devices which are deployed to connect and keep them together. In gas turbines two approaches are normally used in the assembly process. They are the threaded fasteners such as bolt and nut and shrunk-fit or interference-fit assemblies. In the high temperature regions of the gas turbines the effect of creep on the integrity of such fastening arrangements needs to be assessed at the design stage. A problem commonly faced pertains to lack of creep data which would facilitate detailed nonlinear analysis. The available data invariably exhibit scatter. In this paper parametric studies are undertaken. Creep curves are chosen so that both primary and secondary stages are accounted for. The coefficients are chosen to meet the design needs. The performance of bolted joints and shrunk-fit assemblies get affected over time due to stress relaxation leading to loss of bolt pretension or the effective interference. The bolt preload as well as the interference is to be optimally chosen. Higher the preload or the interference the more effective is the joint. At the same time the stress levels are higher and hence the stresses will relax to a greater extent. For a design stage assessment of the behavior of assemblies there is need for correlation among the various operating parameters such as stress, temperature and time. For individual components one normally uses empirical correlations such as Larson-Miller to predict rupture life and also creep growth. For assemblies in which relaxation is the main design issue, such parameters are usually not available. There is need to carry out detailed nonlinear analysis. Typical bolted flange and shrink-fit assemblies are chosen for study. Parametric studies are carried out. Using creep properties as described earlier, nonlinear structural responses are studied. The purpose is to correlate the creep properties, in terms of creep strain with respect to time, stress and temperature, with the joint behavior. The key joint behavior indices are the bolt tensile stress in the case of threaded fastening and the compressive force of “effective interference” in the case of shrunk-fit assemblies. The studies have established the need for rigorous creep analysis of components having interference fits or threaded fasteners. Once the operational requirements are known, the approach presented helps in material selection.

scholarly journals Temperature Resistance of Mo3Si: Phase Stability, Microhardness, and Creep Properties

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 564 ◽  
Author(s):  
Olha Kauss ◽  
Susanne Obert ◽  
Iurii Bogomol ◽  
Thomas Wablat ◽  
Nils Siemensmeyer ◽  
...  
Keyword(s):  
Power Law ◽  
Phase Stability ◽  
Gas Turbines ◽  
Constitutive Models ◽  
Creep Properties ◽  
Multi Scale ◽  
Scale Modeling ◽  
Significant Difference ◽  
Before And After ◽  
Multi Phase

Mo-Si-B alloys are one of the most promising candidates to substitute Ni based superalloys in gas turbines. The optimization of their composition can be achieved more effectively using multi-scale modeling of materials behavior and structural analysis of components for understanding, predicting, and screening properties of new alloys. Nevertheless, this approach is dependent on data on the properties of the single phases in these alloys. The focus of this investigation is Mo3Si, one of the phases in typical Mo-Si-B alloys. The effect of 100 h annealing at 1600 °C on phase stability and microhardness of its three near-stoichiometric compositions—Mo-23Si, Mo-24Si and Mo-25Si (at %)—is reported. While Mo-23Si specimen consist only of Mo3Si before and after annealing, Mo-24Si and Mo-25Si comprise Mo5Si3 and Mo3Si before annealing. The latter is then increased by the annealing. No significant difference in microhardness was detected between the different compositions as well as after annealing. The creep properties of Mo3Si are described at 1093 °C and 1300 °C at varying stress levels as well as at 300 MPa and temperatures between 1050 °C and 1350 °C. Three constitutive models were used for regression of experimental results—(i) power law with a constant creep exponent, (ii) stress range dependent law, and (iii) power law with a temperature-dependent creep exponent. It is confirmed that Mo3Si has a higher creep resistance than Moss and multi-phase Mo-Si-B alloys, but a lower creep strength as compared to Mo5SiB2.

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 Model Adjustment of Small Rotors for High Speed Gas Turbines

1990 ◽  
Author(s):  
Alain Delbez ◽  
Christian Beth ◽  
Daniel Gay
Keyword(s):  
Gas Turbines ◽  
High Speed ◽  
Dynamic Behaviour ◽  
Design Stage ◽  
Rotor Bearing ◽  
Angular Velocities ◽  
Model Adjustment ◽  
Experimental Approaches

In this paper, we present the studies which are carried out at MICROTURBO relating to rotor-bearing systems mounted in small high speed gas turbines. These studies are based on both theoretical and experimental approaches, and are aimed at providing an improved prediction of the dynamic behaviour of rotors at the design stage, in particular the critical angular velocities and sensitivity to unbalance.

Stress Rupture Behavior of Disk Superalloys Exposed to Low-Temperature Hot Corrosion Environment

2020 ◽  
Author(s):  
Dipankar Dua ◽  
Mohammad Khajavi ◽  
Gary White ◽  
Deepak Thirumurthy ◽  
Jaskirat Singh
Keyword(s):  
Low Temperature ◽  
Hot Corrosion ◽  
Inconel 718 ◽  
Gas Turbines ◽  
Rupture Life ◽  
Stress Rupture ◽  
Stress Rupture Life ◽  
Corrosive Environments ◽  
The Impact ◽  
Temperature Surface

Abstract Siemens Energy has a large fleet of aero-derivative gas turbines. The performance and durability of these power turbines largely depend on the capability of hot section components to resist high-temperature surface attacks and to maintain their mechanical properties. Hot corrosion attack occurs due to exposure of turbine components to sulfur-bearing fuels/air together with other corrosive compounds during turbine operation. This paper investigates the impact of low-temperature hot corrosion on the stress rupture of commonly used gas turbine disk alloys, including Inconel 718, Incoloy 901, and A-286. The results indicate that Inconel 718 and Incoloy 901 maintain their creep strength advantage over A-286 in a low-temperature hot corrosion inducing environment at 1100°F. All three materials exhibited an equivalent life reduction in the corrosive environments at 1100°F. Moreover, the results demonstrate that the stress-rupture life of materials in hot-corrosion environments depends on the combined and cumulative effects of corrosion-resistant and hardening elements.

scholarly journals Impact of compressed air energy storage demands on gas turbine performance

2020 ◽  
pp. 095765092090627 ◽  
Author(s):  
Uyioghosa Igie ◽  
Marco Abbondanza ◽  
Artur Szymański ◽  
Theoklis Nikolaidis
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Pressure Ratio ◽  
Engine Performance ◽  
Compressed Air ◽  
Design Stage ◽  
Simulation Code ◽  
Ratio Distribution ◽  
Stall Margin ◽  
Industrial Gas Turbines

Industrial gas turbines are now required to operate more flexibly as a result of incentives and priorities given to renewable forms of energy. This study considers the extraction of compressed air from the gas turbine; it is implemented to store heat energy at periods of a surplus power supply and the reinjection at peak demand. Using an in-house engine performance simulation code, extractions and injections are investigated for a range of flows and for varied rear stage bleeding locations. Inter-stage bleeding is seen to unload the stage of extraction towards choke, while loading the subsequent stages, pushing them towards stall. Extracting after the last stage is shown to be appropriate for a wider range of flows: up to 15% of the compressor inlet flow. Injecting in this location at high flows pushes the closest stage towards stall. The same effect is observed in all the stages but to a lesser magnitude. Up to 17.5% injection seems allowable before compressor stalls; however, a more conservative estimate is expected with higher fidelity models. The study also shows an increase in performance with a rise in flow injection. Varying the design stage pressure ratio distribution brought about an improvement in the stall margin utilized, only for high extraction.

Thermodynamic Performance Analyses of Mixed Gas-Steam Cycle (1): Performance Prediction Method

1998 ◽  
Author(s):  
Kirk Hanawa
Keyword(s):  
Gas Turbine ◽  
Performance Prediction ◽  
Gas Turbines ◽  
Prediction Method ◽  
Design Stage ◽  
Inlet Temperature ◽  
Evaluation Tool ◽  
Operational Parameters ◽  
Mixed Gas ◽  
Linear Differential

There are various papers relevant to the improvement ideas of gas turbine cycles, which in general discuss only optimum one-point cycle analysis.*1,*2,*6 It is, accordingly, unclear whether such improvement concepts can be applied into existing gas turbines or not. It might be difficult to incorporate such ideas, in the case of yielding significant changes for operation modes. And it may be essential to assess improvement ideas, from view points of applicability to existing gas turbine models.*3 This paper introduces the performance analysis method of simplified small perturbation procedure, showing thermodynamic behaviors based upon the component characteristics, and resultant influences due to settled operation parameters, like ambient temperature & pressure, turbine inlet temperature, etc. The established method might be used as a rule of thumb for the performance prediction when introducing water and/or steam injection into GTs, where operational parameters’ changes are defined under multi-linear differential equations. This is easy to compile in the computer as Lotus 1-2-3 or Exel to evaluate whether every parameter is within the limit or not, offering very helpful performance evaluation tool for the conceptual design stage.

Sustainable Design Through Flexible Product Evolution

2004 ◽  
Author(s):  
Michael Van Wie ◽  
Robert B. Stone ◽  
Daniel A. McAdams
Keyword(s):  
Material Selection ◽  
Sustainable Design ◽  
Design Method ◽  
New Technology ◽  
Empirical Studies ◽  
Design Stage ◽  
Vast Number ◽  
Product Evolution ◽  
S Curve ◽  
Over Time

Sustainable design defined broadly is the problem of designing environmentally benign products so that the environment can be maintained with minimal negative effects from the product throughout the product’s entire lifecycle. This research investigates how sustainable design can be achieved at the conceptual design stage. Although sustainability encompasses a vast number of issues ranging from energy efficient solutions, design for disassembly, recycling, proper material selection, and improved manufacturing choices, the research focus of this work is on the particular issue of product evolution as it relates to the flexibility of a product or concept. Product evolution, often powered by new technology, erases the market competitiveness of concepts over time and impacts flexibility on the design effort side. Specifically, how does the designer develop concepts that can at least partially be reused and adapted to the next product generation with minimal effort? One answer is to design flexible concepts that can incur unknown future changes with maximum concept reuse. Flexibility in this context implies the property of a concept, physical solution, component, or product, to be robust and tolerant to generally unavoidable evolutionary changes. The challenge is to know how to configure a product to satisfy this requirement. As part of this research, we perform empirical studies of product evolution to determine evolutionary trends. Product evolution is measured in the broad terms of product performance over time. The goal is to predict when a product should evolve by either 1) moving from the lower plateau of an S-curve to the higher plateau or 2) jumping to a new S-curve being prepared to do so in a sustainable manner. That is, the objective is to allow companies to be able to reuse components or platforms (including reconditioning and recycling), tooling as well as design and manufacturing staff. The key toward this goal is an understanding how products evolve and what conditions coincide with product change. The approach is to investigate the types of changes (evolutions) that lead to flexible (sustainable) designs. The results of this research can be used for a prescriptive approach in developing a sustainable design method that relies on this newly acquired knowledge of product evolution.

Steam-Cooled Gas Turbine Casings, Struts, and Disks in a Reheat Gas Turbine Combined Cycle: Part I—Compressor and Combustor

1983 ◽  
Vol 105 (4) ◽  
pp. 844-850 ◽  
Author(s):  
I. G. Rice
Keyword(s):  
Steam Turbine ◽  
Gas Turbine ◽  
Gas Turbines ◽  
High Performance ◽  
Material Selection ◽  
Pressure Ratio ◽  
Industrial Applications ◽  
Combined Cycle ◽  
Tip Clearance ◽  
Turbine Output

High-cycle pressure-ratio (38–42) gas turbines being developed for future aircraft and, in turn, industrial applications impose more critical disk and casing cooling and thermal-expansion problems. Additional attention, therefore, is being focused on cooling and the proper selection of materials. Associated blade-tip clearance control of the high-pressure compressor and high-temperature turbine is critical for high performance. This paper relates to the use of extracted steam from a steam turbine as a coolant in a combined cycle to enhance material selection and to control expansion in such a manner that the cooling process increases combined-cycle efficiency, gas turbine output, and steam turbine output.

Research on Creep Properties of Sn2.5Ag0.7CuXRE Lead-Free Soldered Joints for Surface Mount Technology

2007 ◽  
Vol 353-358 ◽  
pp. 2912-2915 ◽  
Author(s):  
Ke Ke Zhang ◽  
Yao Li Wang ◽  
Yan Li Fan ◽  
Jie Yiang ◽  
Yan Fu Yan ◽  
...  
Keyword(s):  
Rupture Life ◽  
Creep Property ◽  
Creep Rupture ◽  
Lead Free ◽  
Lead Free Solder ◽  
Surface Mount Technology ◽  
Cross Sectional ◽  
Creep Properties ◽  
Surface Mount ◽  
Free Solder

Creep property of solder alloys is one of the important factors to effect the reliability of surface mount technology (SMT) soldered joints. The creep behavior and its rupture life of Sn2.5Ag0.7CuXRE lead-free soldered joints were separately investigated and predicted under constant temperature by a single shear lap creep specimen with a 1mm2 cross sectional area and finite element method (FEM) in this paper. Results show that the creep property of Sn2.5Ag0.7Cu0.1RE is superior to that of the commercial employed lead-free solder Sn3.8Ag0.7Cu and the creep rupture life of its soldered joints is 8.4 times more than that of Sn2.5Ag0.7Cu solder. The creep rupture life of Sn2.5Ag0.7CuXRE lead-free soldered joints indirectly predicted by FEM is better in accord with that of actual testing results, which are important to design the reliability of lead-free soldered joints for SMT.

Small Punch Creep Testing Technique for Remnant Life Assessment

2014 ◽  
Vol 592-594 ◽  
pp. 739-743 ◽  
Author(s):  
J. Ganesh Kumar ◽  
K. Laha ◽  
M.D. Mathew
Keyword(s):  
Creep Test ◽  
Rupture Life ◽  
Life Assessment ◽  
Test Results ◽  
Creep Tests ◽  
Testing Technique ◽  
Creep Properties ◽  
Small Punch ◽  
Miniature Specimens ◽  
Deflection Rate

Small punch creep (SPC) testing technique is a material non-intensive testing technique for evaluating creep behavior of materials using miniature specimens. It can be used for remnant life assessment (RLA) studies on components in service, by scooping out limited material for testing without impairing the strength of component. In order to ensure the reliability of use of SPC technique for RLA, it is necessary to establish sound database on SPC properties of the material before putting into service. In this investigation, SPC technique was used to evaluate creep properties of 316LN stainless steel using specimens of size 10 x 10 x 0.5 mm. SPC tests were conducted in load controlled mode at 923 K and at various loads. SPC curves clearly exhibited primary, secondary and tertiary creep stages. The minimum deflection rate increased and rupture life decreased with an increase in applied load. Like in conventional creep test results, the minimum deflection rate obeyed Norton’s power law and Monkman-Grant relationship. SPC test was correlated with corresponding conventional creep test. Good correlation was established between creep rupture life values evaluated from SPC tests and conventional creep tests.

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