Improving Turbine Component Efficiency

1980 ◽  
Vol 102 (2) ◽  
pp. 434-436
Author(s):  
K. D. Mach
Keyword(s):  
Structural Integrity ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Metal Structure ◽  
Three Dimensions ◽  
Computation Method ◽  
Test Procedures ◽  
Aerodynamic Efficiency ◽  
Careful Control ◽  
Component Efficiency

The thermal efficiency of a gas turbine engine depends on the cycle pressure and temperature ratio and on the aerodynamic efficiencies of the gas path components. Maintaining and/or improving structural integrity and aerodynamic efficiency in this high pressure, high temperature environment is the preeminent problem of the turbine designer. High gas temperatures require at least some of the metal structure to be cooled, yet cooling air is a loss to the cycle and its consumption must be kept to a minimum. Research into cooling techniques and boundary layer behavior on airfoils and endwalls and into test procedures for obtaining heat transfer data are providing some of the answers the designer needs. Increased operating-pressures generate increased mechanical stresses. Finite element analyses and automated design procedures are proving to be powerful aids to the designer. Improving aerodynamic efficiency requires careful control of the flow in three dimensions, particularly in low aspect ratio machines. The first practical computation method for three-dimensional, viscous, transonic flows became available in late 1977 and has made this one of the most exciting areas of turbine technology. Additional gains in aerodynamic efficiency can be realized by controlling leakages, especially those over the rotor tip, by accounting for the transient interactions between rotor and stator; and by careful control of discharged coolant flow. This paper briefly describes the turbine cooling research conducted by the Air Force Aero Propulsion Laboratory and describes more extensively the AFAPL programs in turbine aerodynamics, including applications of three-dimensional flow analysis.

Improving Turbine Component Efficiency

1979 ◽  
Author(s):  
K. D. Mach
Keyword(s):  
Structural Integrity ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Computation Method ◽  
Test Procedures ◽  
Aerodynamic Efficiency ◽  
Turbine Engine ◽  
Careful Control ◽  
Component Efficiency

The thermal efficiency of a gas turbine engine depends on the cycle pressure and temperature ratio and on the aerodynamic efficiencies of the gas path components. Maintaining and/or improving structural integrity and aerodynamic efficiency in this high pressure, high temperature environment is the preeminent problem of the turbine designer. High gas temperatures require at least some of the metal structures to be cooled, yet cooling air is a loss to the cycle and its consumption must be kept to a minimum. Research into cooling techniques and boundary layer behavior on airfoils and endwalls and into test procedures for obtaining heat transfer data are providing some of the answers the designer needs. Increased operating pressures generate increased mechanical stresses. Finite element analyses and automated design procedures are proving to be powerful aids to the designer. Improving aerodynamic efficiency requires careful control of the flow in three dimensions, particularly in low aspect ratio machines. The first practical computation method for three-dimensional, viscous, transonic flows became available in late 1977 and has made this one of the most exciting areas of turbine technology. Additional gains in aerodynamic efficiency can be realized by controlling leakages, especially those over the rotor tip, by accounting for the transient interactions between rotor and stator and by careful control of discharged coolant flow. This paper briefly describes the turbine cooling research conducted by the Air Force Aero Propulsion Laboratory and describes mor extensively the AFAPL programs in turbine aerodynamics, including applications of three-dimensional flow analysis.

Cellular Automaton Simulations of Surface Mass Transport Due to Curvature Gradients: Simulations of Sintering in 3-D.

1991 ◽  
Vol 249 ◽  
Author(s):  
D.P. Bentz ◽  
P.J.P. Pimienta ◽  
E.J. Garboczi ◽  
W.C. Carter
Keyword(s):  
Cellular Automaton ◽  
Scaling Laws ◽  
Chemical Potential ◽  
Pore Space ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Computation Method ◽  
Surface Mass ◽  
Digital Version ◽  
The Continuum

ABSTRACTA cellular automaton algorithm is described that simulates the evolution of a surface driven by the reduction of chemical potential differences on the surface. When the surface tension is isotropic, the chemical potential is proportional to the curvature at the surface. This process is important in the development of microstructure during the sintering of powders. The algorithm is implemented in two and three dimensions in a digital image mode, using discrete pixels to represent continuum objects. The heart of the algorithm is a pixel-counting-based method for computing the potential at a pixel located in a digital surface. This method gives an approximate measure of the curvature at the given surface pixel. The continuum version of this method is analytically shown to give the true curvature at a point on a continuum surface. The digital version of the curvature computation method is shown to obey the scaling laws derived for the continuum version. The evolution of the surface of a three dimensional loosely packed powder, along with the percolation characteristics of its pore space, are computed as an example of the algorithm.

Free-Form Design of Electrical Machine Rotor Cores for Production Using Additive Manufacturing

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Michele Garibaldi ◽  
Christopher Gerada ◽  
Ian Ashcroft ◽  
Richard Hague
Keyword(s):  
Structural Integrity ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Free Form ◽  
Electrical Machine ◽  
Element Analysis ◽  
Torque Density ◽  
Magnetostatic Problem ◽  
Form Design ◽  
3D Printed

This work presents a finite element analysis-based, topology optimization (TO) methodology for the combined magnetostatic and structural design of electrical machine cores. Our methodology uses the Bi-directional Evolutionary Structural Optimization (BESO) heuristics to remove inefficient elements from a meshed model based on elemental energies. The algorithm improves the average torque density while maintaining structural integrity. To the best of our knowledge, this work represents the first effort to address the structural-magnetostatic problem of electrical machine design using a free-form approach. Using a surface-mounted permanent magnet motor (PMM) as a case study, the methodology is first tested on linear and nonlinear two-dimensional problems whereby it is shown that the rapid convergence achieved makes the algorithm suitable for real-world applications. The proposed optimization scheme can be easily extended to three dimensions, and we propose that the resulting designs are suitable for manufacturing using selective laser melting, a 3D printing technology capable of producing fully dense high-silicon steel components with good soft magnetic properties. Three-dimensional TO results show that the weight of a PMM rotor can be slashed by 50% without affecting its rated torque profile when the actual magnetic permeability of the 3D-printed material is considered.

convergent-beam diffraction from surfaces

1987 ◽  
Vol 45 ◽  
pp. 30-33
Author(s):  
J. A. Eades ◽  
A. E. Smith ◽  
D. F. Lynch
Keyword(s):  
Reciprocal Lattice ◽  
Three Dimensional ◽  
Grazing Incidence ◽  
Three Dimensions ◽  
Plane Figure ◽  
Transmission Electron ◽  
Convergent Beam ◽  
Beam Patterns ◽  
Beam Diffraction

It is quite simple (in the transmission electron microscope) to obtain convergent-beam patterns from the surface of a bulk crystal. The beam is focussed onto the surface at near grazing incidence (figure 1) and if the surface is flat the appropriate pattern is obtained in the diffraction plane (figure 2). Such patterns are potentially valuable for the characterization of surfaces just as normal convergent-beam patterns are valuable for the characterization of crystals.There are, however, several important ways in which reflection diffraction from surfaces differs from the more familiar electron diffraction in transmission.GeometryIn reflection diffraction, because of the surface, it is not possible to describe the specimen as periodic in three dimensions, nor is it possible to associate diffraction with a conventional three-dimensional reciprocal lattice.

Extension of the Spatial PDI Model to Three Dimensions

1997 ◽  
Vol 84 (1) ◽  
pp. 176-178
Author(s):  
Frank O'Brien
Keyword(s):  
Population Density ◽  
Dimensional Space ◽  
Finite Lattice ◽  
Three Dimensional ◽  
Upper Bounds ◽  
Three Dimensions ◽  
Lower And Upper Bounds ◽  
Density Index ◽  
Three Dimensional Space

The author's population density index ( PDI) model is extended to three-dimensional distributions. A derived formula is presented that allows for the calculation of the lower and upper bounds of density in three-dimensional space for any finite lattice.

scholarly journals Free partition functions and an averaged holographic duality

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Nima Afkhami-Jeddi ◽  
Henry Cohn ◽  
Thomas Hartman ◽  
Amirhossein Tajdini
Keyword(s):  
Partition Function ◽  
Spectral Gap ◽  
Central Charge ◽  
Three Dimensional ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Partition Functions ◽  
General Constraints ◽  
Dimensional Gravity ◽  
Holographic Duality

Abstract We study the torus partition functions of free bosonic CFTs in two dimensions. Integrating over Narain moduli defines an ensemble-averaged free CFT. We calculate the averaged partition function and show that it can be reinterpreted as a sum over topologies in three dimensions. This result leads us to conjecture that an averaged free CFT in two dimensions is holographically dual to an exotic theory of three-dimensional gravity with U(1)c×U(1)c symmetry and a composite boundary graviton. Additionally, for small central charge c, we obtain general constraints on the spectral gap of free CFTs using the spinning modular bootstrap, construct examples of Narain compactifications with a large gap, and find an analytic bootstrap functional corresponding to a single self-dual boson.

Turbulent three-dimensional dielectric electrohydrodynamic convection between two plates

2012 ◽  
Vol 696 ◽  
pp. 228-262 ◽  
Author(s):  
A. Kourmatzis ◽  
J. S. Shrimpton
Keyword(s):  
Spatial Data ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Energy Budgets ◽  
Turbulent Regime ◽  
Scalar Flux ◽  
Wide Range ◽  
Scalar Variance

AbstractThe fundamental mechanisms responsible for the creation of electrohydrodynamically driven roll structures in free electroconvection between two plates are analysed with reference to traditional Rayleigh–Bénard convection (RBC). Previously available knowledge limited to two dimensions is extended to three-dimensions, and a wide range of electric Reynolds numbers is analysed, extending into a fully inherently three-dimensional turbulent regime. Results reveal that structures appearing in three-dimensional electrohydrodynamics (EHD) are similar to those observed for RBC, and while two-dimensional EHD results bear some similarities with the three-dimensional results there are distinct differences. Analysis of two-point correlations and integral length scales show that full three-dimensional electroconvection is more chaotic than in two dimensions and this is also noted by qualitatively observing the roll structures that arise for both low (${\mathit{Re}}_{E} = 1$) and high electric Reynolds numbers (up to ${\mathit{Re}}_{E} = 120$). Furthermore, calculations of mean profiles and second-order moments along with energy budgets and spectra have examined the validity of neglecting the fluctuating electric field ${ E}_{i}^{\ensuremath{\prime} } $ in the Reynolds-averaged EHD equations and provide insight into the generation and transport mechanisms of turbulent EHD. Spectral and spatial data clearly indicate how fluctuating energy is transferred from electrical to hydrodynamic forms, on moving through the domain away from the charging electrode. It is shown that ${ E}_{i}^{\ensuremath{\prime} } $ is not negligible close to the walls and terms acting as sources and sinks in the turbulent kinetic energy, turbulent scalar flux and turbulent scalar variance equations are examined. Profiles of hydrodynamic terms in the budgets resemble those in the literature for RBC; however there are terms specific to EHD that are significant, indicating that the transfer of energy in EHD is also attributed to further electrodynamic terms and a strong coupling exists between the charge flux and variance, due to the ionic drift term.

scholarly journals The Everyday Life of Security: Capturing Space, Practice, and Affect

2021 ◽  
Author(s):  
Jonna Nyman
Keyword(s):  
Everyday Life ◽  
Research Methods ◽  
Lived Experiences ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Conceptual Clarity ◽  
The Everyday ◽  
Participatory Photography ◽  
High Politics ◽  
Ordinary Citizens

Abstract Security shapes everyday life, but despite a growing literature on everyday security there is no consensus on the meaning of the “everyday.” At the same time, the research methods that dominate the field are designed to study elites and high politics. This paper does two things. First, it brings together and synthesizes the existing literature on everyday security to argue that we should think about the everyday life of security as constituted across three dimensions: space, practice, and affect. Thus, the paper adds conceptual clarity, demonstrating that the everyday life of security is multifaceted and exists in mundane spaces, routine practices, and affective/lived experiences. Second, it works through the methodological implications of a three-dimensional understanding of everyday security. In order to capture all three dimensions and the ways in which they interact, we need to explore different methods. The paper offers one such method, exploring the everyday life of security in contemporary China through a participatory photography project with six ordinary citizens in Beijing. The central contribution of the paper is capturing—conceptually and methodologically—all three dimensions, in order to develop our understanding of the everyday life of security.

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