Gas Turbines and Uncertainty Quantification: Impact of PDF Tails on UQ Predictions, the Black Swan

2013 ◽  
Author(s):  
Francesco Montomoli ◽  
Michela Massini
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Uncertainty Quantification ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Black Swan ◽  
Probability Of Occurrence ◽  
Hot Gas ◽  
Black Swans ◽  
Input Parameters

In the last five years Uncertainty Quantification (UQ) techniques became popular to predict gas turbine performances. Taking into account the uncertainties in the input parameters it is possible to evaluate the impact of random variations and to overcome the limitations of deterministic studies. These methods, that only recently have been widely used in computational fluid dynamics, have some limitations that must be considered. One of the most important limitations is that these models cannot predict a “Black Swan” (BS) event. In probability a Black Swan is an event rare, possible and with serious consequences. A reliable design requires a correct evaluation of the probabilities of occurrence of the Black Swan that could strongly affect the life of the turbine. Black Swans are generated by the variability of the input parameters in the “tail” of the statistical distributions. Being far from the mean value design geometry/condition, these events have a low probability of occurrence. In this paper is shown that the use of the Gaussian distribution for the input parameters could strongly underestimate the probability of occurrence of a Black Swan event. Despite that most of the models used in UQ for aerodesign are neglecting the problem. As an example of Black Swan, the hot gas ingestion across a stator is analysed. The gaps have been assumed to be affected by uncertainty with a variation of +/-50% of the nominal value. By using a Monte Carlo simulation with 108 realizations and a Gauss distribution as input, the configuration is initially considered reliable. The six sigma criterion is also satisfied and the probability to have a failure is only 2.54 10−4%. However if a “fat tail” for the input distribution is used instead, the probability to have hot gas ingestion becomes 2.33%, 104 times higher. Most of the methods used in literature aim to have an accurate reproduction of the PDF moments such as mean, standard deviation, skew and kurtosis. However the “tail” of the distribution affects the gas turbine life and must be considered. In particular “fat tails”, the mathematical origin of Black Swans events, can have serious consequences, but in modern stochastic models used for computational fluid dynamics they are not accounted for.

scholarly journals Ensuring Adequate Coolant Purity for Advanced Gas Turbines

1995 ◽  
Author(s):  
D. E. Woodmansee ◽  
A. K. Tolpadi ◽  
T. H. Hwang ◽  
A. D. Maddaus
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Particulate Contaminants ◽  
Accelerating Flows

The role of particulate contaminants in advanced gas turbine coolants is discussed, especially in light of the extremely high G-field regions they will experience in service. Predictions of sedimentation in both laminar and highly turbulent accelerating flows using a computational fluid dynamics code are made for a range of particulate sizes to show that particles over 0.5 µm are of concern. Possible techniques for limiting access of these particulates to the gas turbines themselves are presented. Overall, contaminant deposition appears controllable, limiting required cleaning of coolant channels to regularly scheduled inspections.

scholarly journals COLD FLOW NUMERICAL ANALYSIS OF GAS MICROTURBINE COMBUSTION CHAMBER THROUGH CFD TOOL

2019 ◽  
Vol 18 (1) ◽  
pp. 29
Author(s):  
G. K. Caetano ◽  
J. F. T. de Carvalho ◽  
J. S. Rosa
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Combustion Chamber ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Reverse Flow ◽  
Ideal Point ◽  
Random Motion ◽  
Design Data ◽  
Cold Flow

Gas turbines are equipment used mainly in the generation of electric energy. They have as one of their main components the combustion chamber. Therefore, it is relevant to study the characteristics of this component, in order to reach a satisfactory operation. In this context, this paper presents an analysis of a combustion chamber applied to a gas turbine with a cold flow approach using the numerical theoretical method, through the computational fluid dynamics technique. In this experiment, the software Abaqus CFD (computational fluid dynamics) – present in the 3DExperience platform – and the finite volume method are used. The objective was to evaluate the flow, pressure and velocity profiles during the single-phase flow. The gas turbine prototype is configured using a combustion chamber of reverse flow type in order to decrease flow velocity and increase the combustion efficiency. Based on input data obtained from practical experiments, the calculation of the number and Reynolds confirmed – according to the literature of fluid mechanics – the occurrence of a flow classified as turbulent, with chaotic and random motion, what allows defining the ideal point of injection from analysis of velocity plots with stream lines. In addition, a Mach number smaller than 0.3 confirms the theory of having an incompressible flow, in which compressibility effects can be disregarded. The analysis of mass flow rates of the combustion zones made it possible to evaluate maximum differences of 3% between the design data and the one found in the study. To determine the inherent error of the mesh in the CFD study was calculated through the grid conference method, the value found was around 2.68%.

Effect of Outer Fin Axial Gap on the Sealing Effectiveness and Fluid Dynamics of Radial Rim Seal

2017 ◽  
Author(s):  
Zhigang Li ◽  
Jun Li ◽  
Liming Song ◽  
Qing Gao ◽  
Xin Yan ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Flow Rate ◽  
Gas Turbines ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Numerical Approach ◽  
Coolant Flow ◽  
Coolant Flow Rate ◽  
Navier Stokes ◽  
Hot Gas

The modern gas turbine is widely applied in the aviation propulsion and power generation. The rim seal is usually designed at the periphery of the wheel-space and prevented the hot gas ingestion in modern gas turbines. The high sealing effectiveness of rim seal can improve the aerodynamic performance of gas turbines and avoid of the disc overheating. Effect of outer fin axial gap of radial rim seal on the sealing effectiveness and fluid dynamics was numerically investigated in this work. The sealing effectiveness and fluid dynamics of radial rim seal with three different outer fin axial gaps was conducted at different coolant flow rates using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) and SST turbulent model solutions. The accuracy of the presented numerical approach for the prediction of the sealing performance of the turbine rim seal was demonstrated. The obtained results show that the sealing effectiveness of radial rim seal increases with increase of coolant flow rate at the fixed axial outer fin gap. The sealing effectiveness increases with decrease of the axial outer fin gap at the fixed coolant flow rate. Furthermore, at the fixed coolant flow rate, the hot gas ingestion increases with the increase of the axial outer fin gap. This flow behavior intensifies the interaction between the hot gas and coolant flow at the clearance of radial rim seal. The preswirl coefficient in the wheel-space cavity is also illustrated to analyze the flow dynamics of radial rim seal at different axial outer fin gaps.

A Fully Integrated Approach to Component Zooming Using Computational Fluid Dynamics

2004 ◽  
Vol 128 (3) ◽  
pp. 579-584 ◽  
Author(s):  
Vassilios Pachidis ◽  
Pericles Pilidis ◽  
Fabien Talhouarn ◽  
Anestis Kalfas ◽  
Ioannis Templalexis
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Gas Turbine ◽  
Engine Performance ◽  
Integrated Approach ◽  
High Fidelity ◽  
Performance Simulation ◽  
Fully Integrated ◽  
Engine Component ◽  
Simulation Strategy

Background . This study focuses on a simulation strategy that will allow the performance characteristics of an isolated gas turbine engine component, resolved from a detailed, high-fidelity analysis, to be transferred to an engine system analysis carried out at a lower level of resolution. This work will enable component-level, complex physical processes to be captured and analyzed in the context of the whole engine performance, at an affordable computing resource and time. Approach. The technique described in this paper utilizes an object-oriented, zero-dimensional (0D) gas turbine modeling and performance simulation system and a high-fidelity, three-dimensional (3D) computational fluid dynamics (CFD) component model. The work investigates relative changes in the simulated engine performance after coupling the 3D CFD component to the 0D engine analysis system. For the purposes of this preliminary investigation, the high-fidelity component communicates with the lower fidelity cycle via an iterative, semi-manual process for the determination of the correct operating point. This technique has the potential to become fully automated, can be applied to all engine components, and does not involve the generation of a component characteristic map. Results. This paper demonstrates the potentials of the “fully integrated” approach to component zooming by using a 3D CFD intake model of a high bypass ratio turbofan as a case study. The CFD model is based on the geometry of the intake of the CFM56-5B2 engine. The high-fidelity model can fully define the characteristic of the intake at several operating condition and is subsequently used in the 0D cycle analysis to provide a more accurate, physics-based estimate of intake performance (i.e., pressure recovery) and hence, engine performance, replacing the default, empirical values. A detailed comparison between the baseline engine performance (empirical pressure recovery) and the engine performance obtained after using the coupled, high-fidelity component is presented in this paper. The analysis carried out by this study demonstrates relative changes in the simulated engine performance larger than 1%. Conclusions. This investigation proves the value of the simulation strategy followed in this paper and completely justifies (i) the extra computational effort required for a more automatic link between the high-fidelity component and the 0D cycle, and (ii) the extra time and effort that is usually required to create and run a 3D CFD engine component, especially in those cases where more accurate, high-fidelity engine performance simulation is required.

A Review of Some Early Design Practice Using Computational Fluid Dynamics and a Current Perspective

2005 ◽  
Vol 127 (1) ◽  
pp. 5-13 ◽  
Author(s):  
J. H. Horlock ◽  
J. D. Denton
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Gas Turbines ◽  
Design Practice ◽  
Future Developments ◽  
Basic Fluid ◽  
Current Perspective ◽  
Computational Fluid Dynamics Cfd ◽  
A Current ◽  
Empirical Design

In the early development of gas turbines, many empirical design rules were used; for example in obtaining fluid deflection using the deviation from blading angles, in the assumption of zero radial velocities (so-called radial equilibrium) and in expressions for clearance loss (the Lakshminarayana formulas). The validity of some of these rules, and the basic fluid mechanics behind them, is examined by use of modern ideas and computational fluid dynamics (CFD) codes. A current perspective of CFD in design is given, together with a view on future developments.

Uncertainty Quantification in High Performance Computational Fluid Dynamics

2021 ◽  
pp. 355-371
Author(s):  
Andrea Beck ◽  
Jakob Dürrwächter ◽  
Thomas Kuhn ◽  
Fabian Meyer ◽  
Claus-Dieter Munz ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Uncertainty Quantification ◽  
High Performance

Computational Fluid Dynamics Study of Oil Behavior in a Scoop, and Factors Affecting Scoop Capture Efficiency

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Evgenia Korsukova ◽  
Hervé Morvan
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Gas Turbines ◽  
High Speed ◽  
Velocity Ratio ◽  
Capture Efficiency ◽  
Parameter Analysis ◽  
Parameter Study ◽  
3D Simulations ◽  
Engine Components

Abstract Due to the continuous reduction of engine sizes, efficient under-race lubrication becomes ever more crucial in order to provide sufficient amount of oil to various engine components. An oil scoop is a rotating component that captures oil from a jet, and axially redirects it to the bearing, providing under-race lubrication. Given the importance of lubrication in high-speed engine components, the efficiency study of under-race lubrication appliances receives rapidly growing demands from manufacturers and therefore is of great interest. This work provides description of computational fluid dynamics (CFD) methods that were found to be most accurate and efficient for a large parameter analysis of the scoop capture efficiencies. One of the main purposes of this paper is to demonstrate an optimal and validated computational approach to modeling under-race lubrication with a focus on oil capture efficiency. Second, to show which factors most influence the scoop capture efficiency. Additionally, simulations allow for the fluid behavior inside the scoop to be observed that cannot be visualized experimentally due to high speeds. An improved method of efficiency calculation is also presented and compared to existing methods (Cageao, P. P., Simmons, K., Prabhakar, A., and Chandra, B., 2019, “Assessment of the Oil Scoop Capture Efficiency in High Speed Rotors,” ASME J. Eng. Gas Turbines Power, 141(1), p. 012401; Korsukova, E., Kruisbrink, A., Morvan, H., Paleo Cageao, P., and Simmons, K., 2016, “Oil Scoop Simulation and Analysis Using CFD and SPH,” ASME Paper No. GT2016-57554.). Results of both two-dimensional (2D) and semi-three-dimensional (3D) simulations are provided. Both qualitative comparison of 2D with semi-3D simulations and quantitative comparison of 2D simulations with experiments (Cageao, P. P., Simmons, K., Prabhakar, A., and Chandra, B., 2019, “Assessment of the Oil Scoop Capture Efficiency in High Speed Rotors,” ASME J. Eng. Gas Turbines Power, 141(1), p. 012401) show consistency. Parameter study using 2D simulations is shown with variation of rotational scoop speed, jet angles, velocity ratio. Key results show that changes of the jet angle and velocity ratio can improve the scoop efficiency.

Coal-Water Slurry Testing of an Industrial Gas Turbine

1992 ◽  
Author(s):  
R. A. Wenglarz ◽  
C. Wilkes ◽  
R. C. Bourke ◽  
H. C. Mongia
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Water Injection ◽  
Department Of Energy ◽  
Combustion System ◽  
Hot Gas ◽  
Water Slurry ◽  
Coal Water Slurry ◽  
Burning Coal ◽  
Industrial Gas Turbine

This paper describes the first test of an industrial gas turbine and low emissions combustion system on coal-water-slurry fuel. The engine and combustion system have been developed over the past five years as part of the Heat Engines program sponsored by the Morgantown Energy Technology Center of the U.S. Department of Energy (DOE). The engine is a modified Allison 501-K industrial gas turbine designed to produce 3.5 MW of electrical power when burning natural gas or distillate fuel. Full load power output increases to approximately 4.9 MW when burning coal-water slurry as a result of additional turbine mass flow rate. The engine has been modified to accept an external staged combustion system developed specifically for burning coal and low quality ash-bearing fuels. Combustion staging permits the control of NOx from fuel-bound nitrogen while simultaneously controlling CO emissions. Water injection freezes molten ash in the quench zone located between the rich and lean zones. The dry ash is removed from the hot gas stream by two parallel cyclone separators. This paper describes the engine and combustor system modifications required for running on coal and presents the emissions and turbine performance data from the coal-water slurry testing. Included is a discussion of hot gas path ash deposition and planned future work that will support the commercialization of coal-fired gas turbines.

Coupled Thermo-Mechanical Fatigue Tests for Simulating Load Conditions in Cooled Turbine Parts

2011 ◽  
Author(s):  
Roland Mu¨cke ◽  
Klaus Rau
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Mechanical Load ◽  
Fatigue Tests ◽  
Temperature Fields ◽  
Hot Gas ◽  
Mechanical Fatigue ◽  
Numerical Predictions ◽  
Temperature Capability ◽  
Load Conditions

Modern heavy-duty gas turbines operate under hot gas temperatures that are much higher than the temperature capability of nickel superalloys. For that reason, advanced cooling technology is applied for reducing the metal temperature to an acceptable level. Highly cooled components, however, are characterised by large thermal gradients resulting in inhomogeneous temperature fields and complex thermo-mechanical load conditions. In particular, the different rates of stress relaxation due to the different metal temperatures on hot gas and cooling air exposed surfaces lead to load redistributions in cooled structures, which have to be considered in the lifetime prediction methodology. In this context, the paper describes Coupled Thermo-Mechanical Fatigue (CTMF) tests for simultaneously simulating load conditions on hot and cold surfaces of cooled turbine parts, Refs [1, 2]. In contrary to standard Thermo-Mechanical Fatigue (TMF) testing methods, CTMF tests involve the interaction between hot and cold regions of the parts and thus more closely simulates the material behaviour in cooled gas turbine structures. The paper describes the methodology of CTMF tests and their application to typical load conditions in cooled gas turbine parts. Experimental results are compared with numerical predictions showing the advantages of the proposed testing method.

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