scholarly journals Turbine thermomechanical modelling during excessive axial movement and overspeed

2019 ◽  
Vol 123 (1260) ◽  
pp. 248-264
Author(s):  
I. Eryilmaz ◽  
V. Pachidis
Keyword(s):  
Finite Element ◽  
Design Space Exploration ◽  
Design Space ◽  
Design Guidelines ◽  
Dislocation Rate ◽  
Frictional Torque ◽  
Turbine Wheel ◽  
Axial Movement ◽  
Free Running ◽  
Shaft Failure

ABSTRACTThis manuscript discusses the numerical (finite element) and analytical modelling of structural interactions between gas turbine components in case of excessive axial movement and overspeed. Excessive axial movement, which may occur after a shaft failure, results in contact between rotating and static turbine components under high forces. These forces create friction which can act as a counter torque, potentially retarding the ‘free-rotating’ components. The study is based on a shaft failure scenario of a ‘three-shaft’, high ‘bypass’ ratio, civil ‘large-fan’ engine. Coupled analytical performance and friction methods are used as stand-alone tools to investigate the effect of rubbing between rotating and stationary components. The method is supported by ‘high-fidelity’, ‘three-dimensional’, thermomechanical finite element simulations using LS-DYNA software. The novelty of the work reported herein lies in the development of a generalised modelling approach that can produce useful engine design guidelines to minimise the terminal speed of a free running turbine after an unlocated shaft failure. The study demonstrates the advantage of using a fast analytical formulation in a design space exploration, after verifying the analytical model against finite element simulation results. The radius and the area of a stationary seal platform in the turbine assembly are changed systematically and the design space is explored in terms of turbine acceleration, turbine dislocation rate and stationary component mass. The radius of the friction interface increases due to the increasing radius of the nozzle guide vane flow path and stationary seal platform. This increases the frictional torque generated at the interface. It was found that if the axial dislocation rate of the free running turbine wheel is high, the resulting friction torque becomes more effective as an overspeed prevention mechanism. Reduced contact area results in a higher axial dislocation rate and this condition leads to a design compromise between available friction capacity, during shaft failure contact and seal platform structural integrity.

Optimization Methodology for Composite Stiffened Panel Based on Genetic Algorithm

2014 ◽  
Vol 952 ◽  
pp. 34-37
Author(s):  
Da Feng Jin ◽  
Zhe Liu ◽  
Zhi Rui Fan
Keyword(s):  
Genetic Algorithm ◽  
Finite Element Method ◽  
Finite Element ◽  
Design Space ◽  
Design Guidelines ◽  
Stiffened Panel ◽  
Stacking Sequence ◽  
Design Variables ◽  
Composite Stiffened Panel ◽  
Optimization Methodology

A novel optimization methodology for stiffened panel is proposed in this paper. The purpose of the optimization methodology is to improve the first buckling load of the panel which is obtained by finite element method. The stacking sequence of the stiffeners is taken as design variables. In order to ensure the manufacturability of design, the design guidelines of stacking sequence are taken into account. A DOE based on Halton Sequence makes the initial points of genetic algorithm spread more evenly in the design space of laminate parameters and consequently accelerates the search to convergence. The numerical example verifies the efficiency of this method.

Hydrodynamic Hull form Design Space Exploration of Large Medium-Speed Catamarans using Full-Scale CFD

2015 ◽  
Vol 157 (A3) ◽  
pp. 161-174
Keyword(s):  
Design Space Exploration ◽  
Design Space ◽  
Free Surface Flow ◽  
Design Guidelines ◽  
Surface Flow ◽  
Full Scale ◽  
Efficient Operation ◽  
Medium Speed ◽  
Wide Range ◽  
Form Design

Large medium-speed catamarans are a new class of vessel currently under development as fuel-efficient ferries for sustainable fast sea transportation. Appropriate data to derive design guidelines for such vessels are not available and therefore a wide range of demihull slenderness ratios were studied to investigate the design space for fuel-efficient operation. Computational fluid dynamics for viscous free-surface flow simulations were utilised to investigate resistance properties of different catamaran configurations having a similar deadweight at light displacement, but with lengths ranging from 110 m to 190 m. The simulations were conducted at full-scale Reynolds numbers (log(Re) = 8.9 – 9.6) and Froude numbers ranged from Fr = 0.25 to 0.49. Hulls of 130 m and below had high transport efficiency below 26 knots and in light loading conditions while hulls of 150 m and 170 m showed benefits for heavier displacement cases and speeds up to 35 knots. Furthermore, the study concluded that the lowest drag was achieved with demihull slenderness ratios between 11 and 13.

Finite element analysis of multirecess hybrid spherical journal bearing system

2019 ◽  
Vol 234 (11) ◽  
pp. 1798-1821
Author(s):  
Adesh K Tomar ◽  
Satish C Sharma
Keyword(s):  
Finite Element ◽  
Journal Bearing ◽  
Design Guidelines ◽  
Numerical Results ◽  
Fluid Film ◽  
Frictional Torque ◽  
Element Analysis ◽  
Fluid Film Thickness ◽  
Film Stiffness ◽  
Bearing System

The present work deals with finite element method analysis of a multirecess hybrid spherical journal bearing system. The governing equations have been discretized using Galerkin’s technique and are solved simultaneously using a suitable iterative technique. The effect of span angle on the static and dynamic behavior of a hybrid spherical journal bearing compensated with membrane restrictor is investigated in the present work. Numerical results indicate that larger values of span angle provide enhanced value of minimum fluid-film thickness [Formula: see text], reduced lubricant flow requirement [Formula: see text], and higher value of frictional torque [Formula: see text]. Further, the results have been compared with a correspondingly similar capillary-compensated bearing. The comparison of numerically results demonstrates that the value of direct fluid-film stiffness coefficient [Formula: see text] could be 45.90% higher than that of correspondingly similar capillary-compensated bearing. The numerical results presented in this work may be useful as design guidelines for a recessed hybrid spherical journal bearing.

HYDRODYNAMIC HULL FORM DESIGN SPACE EXPLORATION OF LARGE MEDIUM-SPEED CATAMARANS USING FULL-SCALE CFD

2021 ◽  
Vol 157 (A3) ◽  
Author(s):  
M Haase ◽  
J R Binns ◽  
N Bose ◽  
G Davidson ◽  
G Thomas ◽  
...  
Keyword(s):  
Design Space Exploration ◽  
Design Space ◽  
Free Surface Flow ◽  
Design Guidelines ◽  
Surface Flow ◽  
Full Scale ◽  
Efficient Operation ◽  
Medium Speed ◽  
Wide Range ◽  
Form Design

Large medium-speed catamarans are a new class of vessel currently under development as fuel-efficient ferries for sustainable fast sea transportation. Appropriate data to derive design guidelines for such vessels are not available and therefore a wide range of demihull slenderness ratios were studied to investigate the design space for fuel-efficient operation. Computational fluid dynamics for viscous free-surface flow simulations were utilised to investigate resistance properties of different catamaran configurations having a similar deadweight at light displacement, but with lengths ranging from 110 m to 190 m. The simulations were conducted at full-scale Reynolds numbers (log(Re) = 8.9 – 9.6) and Froude numbers ranged from Fr = 0.25 to 0.49. Hulls of 130 m and below had high transport efficiency below 26 knots and in light loading conditions while hulls of 150 m and 170 m showed benefits for heavier displacement cases and speeds up to 35 knots. Furthermore, the study concluded that the lowest drag was achieved with demihull slenderness ratios between 11 and 13.

Design Space Exploration of a Beam Flexible Hub Concept for an Inside-Out Ceramic Turbine Using a Simplified Rotordynamic Finite Element Model

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Céderick Landry ◽  
Patrick K. Dubois ◽  
Jean-Sébastien Plante ◽  
François Charron ◽  
Mathieu Picard
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Design Space Exploration ◽  
Design Space ◽  
Space Exploration ◽  
Element Model ◽  
Inlet Temperature ◽  
Blade Tip ◽  
Hoop Stresses ◽  
Inside Out

This paper presents a new flexible hub design for the inside-out ceramic turbine (ICT) rotor configuration. This configuration is used in microturbines to integrate ceramic blades in order to increase turbine inlet temperature (TIT), which leads to higher cycle efficiency values. The ICT uses an outer composite rim to load the ceramic blades in compression by converting the centrifugal loads of the blades into hoop stresses in the composite rim. High stresses in the composite rim lead to high radial displacement of the blades. This displacement is compensated by using flexible hub in order to maintain the contact with the blades. However, hub flexibility can lead to rotordynamic problems as heavy hub deformation will induce high stresses in it. Thus, stresses in the hub are induced by both rotordynamics and centrifugation, requiring a multi-objective design process, which has yielded geometries that limited, until now, the blade tip speed to 358 m/s. In this paper, a simplified rotordynamics finite element model of a flexible hub is developed to allow quick design iterations. Using the model, a design space exploration of this hub concept is done while considering centrifugation and rotordynamics. Experimental validation is conducted on a simplified ICT prototype up to 129 krpm, i.e., an equivalent blade tip speed of 390 m/s. Finally, predictions from the experimentally calibrated model show that the tested prototype hub could reach a blade tip speed of 680 m/s.

Design of Experiments for Aeroelastic Analysis

2012 ◽  
Author(s):  
Natasha Smith ◽  
Jose Camberos ◽  
Edward Alyanak
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Design Of Experiments ◽  
Design Space Exploration ◽  
Design Space ◽  
Response Surfaces ◽  
Wing Shape ◽  
Computational Experiments ◽  
Element Analysis ◽  
Aeroelastic Analysis

The performance of an aircraft in flight is, in part, a result of interactions between aerodynamic forces and structural deformations. Aerodynamic pressures result in elastic deformations which alter the wing shape and thus affect the aerodynamics. Consideration of this multidisciplinary interaction is critical to wing design. In particular, divergence (static elastic instability) and flutter (dynamic resonance) are potential catastrophic effects to be avoided. Performing an aeroelastic analysis requires the combination of static and dynamic structural analysis (often done through finite element analysis) with aerodynamic analysis (typically using some form of computational fluid dynamics, CFD). For large grids, each of these can require a significant computational effort. Resolving the interactions between the two is an iterative process which only magnifies the problem. This is a typical characteristic and drawback of multidisciplinary analysis; it makes exploring a large design space (which may include a large range of wing shape, structural support, and material choices) particularly challenging. Statistical design of experiments (DOX) is one technique for design space exploration using a limited number of targeted, computational experiments. DOX is useful for identifying the design variables most critical for a relevant response, and for finding sensitivities needed for design optimization. The objectives for this project were (1) to find the most significant geometric, modeling, and material parameters that affect the predicted aeroelastic responses of a simple wing geometry, (2) to develop parsimonious, low-order response surfaces to model effects of interest, (3) and to evaluate the quality of the response surfaces. The computational experiments were performed with MSC Nastran which combines finite element analysis for the structural response with a steady vortex-lattice method for trim aeroelastic analyses. The discussion will include an overview of the experiment design selection process, formulation of an approximation model, and an explanation of key metrics for evaluating the response surface designs. Comprehensive results are presented for the natural frequency responses, as well as a preliminary analysis of aerodynamic trim solutions.

Design Space Exploration of a 512KB STT-Assisted SOT MRAM Cache

2020 ◽  
Author(s):  
Adrian G. Caburnay ◽  
Jonathan Gabriel S.A. Reyes ◽  
Anastacia P. Ballesil-Alvarez ◽  
Maria Theresa G. de Leon ◽  
John Richard E. Hizon ◽  
...  
Keyword(s):  
Design Space Exploration ◽  
Design Space ◽  
Space Exploration

scholarly journals Development of Simulation Based p-Multipliers for Laterally Loaded Pile Groups in Granular Soil Using 3D Nonlinear Finite Element Model

2020 ◽  
Vol 11 (1) ◽  
pp. 26
Author(s):  
Muhammad Bilal Adeel ◽  
Muhammad Asad Jan ◽  
Muhammad Aaqib ◽  
Duhee Park
Keyword(s):  
Finite Element ◽  
Element Model ◽  
Design Guidelines ◽  
American Petroleum Institute ◽  
Winkler Foundation ◽  
Group Effect ◽  
Pile Groups ◽  
Element Analysis ◽  
Laterally Loaded Pile ◽  
Laterally Loaded

The behavior of laterally loaded pile groups is usually accessed by beam-on-nonlinear-Winkler-foundation (BNWF) approach employing various forms of empirically derived p-y curves and p-multipliers. Averaged p-multiplier for a particular pile group is termed as the group effect parameter. In practice, the p-y curve presented by the American Petroleum Institute (API) is most often utilized for piles in granular soils, although its shortcomings are recognized. In this study, we performed 3D finite element analysis to develop p-multipliers and group effect parameters for 3 × 3 to 5 × 5 vertically squared pile groups. The effect of the ratio of spacing to pile diameter (S/D), number of group piles, varying friction angle (φ), and pile fixity conditions on p-multipliers and group effect parameters are evaluated and quantified. Based on the simulation outcomes, a new functional form to calculate p-multipliers is proposed for pile groups. Extensive comparisons with the experimental measurements reveal that the calculated p-multipliers and group effect parameters are within the recorded range. Comparisons with two design guidelines which do not account for the pile fixity condition demonstrate that they overestimate the p-multipliers for fixed-head condition.

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