Flow Aerodynamics Modeling of an MHD Swirl Combustor: Calculations and Experimental Verification

1982 ◽  
Vol 104 (3) ◽  
pp. 385-391 ◽  
Author(s):  
A. K. Gupta ◽  
J. M. Bee´r ◽  
J. F. Louis ◽  
A. A. Busnaina ◽  
D. G. Lilley
Keyword(s):  
Computer Code ◽  
Staggered Grid ◽  
Constant Density ◽  
Swirl Combustor ◽  
Second Stage ◽  
Density Flow ◽  
Swirl Velocity ◽  
Theoretical Predictions ◽  
Seed Distribution ◽  
Shaped Nozzle

This paper describes a computer code for calculating the flow dynamics of constant density flow in the second stage trumpet shaped nozzle section of a two stage MHD swirl combustor for application to a disk generator. The primitive pressure-velocity variable, finite difference computer code has been developed to allow the computation of inert nonreacting turbulent swirling flows in an axisymmetric MHD model swirl combustor. The method and program involve a staggered grid system for axial and radial velocities, and a line relaxation technique for efficient solution of the equations. Turbulence simulation is by way of a two-equation κ-ε model. The code produces as output the flowfield map of the nondimensional stream function, axial, and swirl velocity. Good argeement was obtained between the theoretical predictions and the qualitative experimental results. The best seed injector location for uniform seed distribution at combustor exit is with injector located centrally on the combustor axis at entrance to the second stage combustor.

scholarly journals Validation of Digital Rock Physics Algorithms

Minerals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 669
Author(s):  
Rongrong Lin ◽  
Leon Thomsen
Keyword(s):  
Rock Physics ◽  
Image Resolution ◽  
Staggered Grid ◽  
Static Properties ◽  
Shear Moduli ◽  
Digital Rock Physics ◽  
Digital Rock ◽  
Saturated Rock ◽  
Theoretical Predictions ◽  
Theoretical Test

With a detailed microscopic image of a rock sample, one can determine the corresponding 3-D grain geometry, forming a basis to calculate the elastic properties numerically. The issues which arise in such a calculation include those associated with image resolution, the registration of the digital numerical grid with the digital image, and grain anisotropy. Further, there is a need to validate the numerical calculation via experiment or theory. Because of the geometrical complexity of the rock, the best theoretical test employs the Hashin–Shtrikman result that, for an aggregate of two isotropic components with equal shear moduli, the bulk modulus is uniquely determined, independent of the micro-geometry. Similarly, for an aggregate of two isotropic components with a certain combination of elastic moduli defined herein, the Hashin–Shtrikman formulae give a unique result for the shear modulus, independent of the micro-geometry. For a porous, saturated rock, the solid incompressibility may be calculated via an “unjacketed” test, independent of the micro-geometry. Any numerical algorithm proposed for digital rock physics computation should be validated by successfully confirming these theoretical predictions. Using these tests, we validate a previously published staggered-grid finite difference damped time-stepping algorithm to calculate the static properties of digital rock models.

A Study of Two-Dimensional Supersonic Air Ejector Systems

1973 ◽  
Vol 187 (1) ◽  
pp. 733-743
Author(s):  
R. S. Benson ◽  
V. A. Eustace
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Ambient Pressure ◽  
Performance Characteristics ◽  
Constant Density ◽  
Two Dimensional ◽  
Theoretical Predictions ◽  
Flow Field Characteristics ◽  
Air Ejector

The performance and flow field characteristics for two-dimensional ejector systems are determined theoretically for the condition when operation is independent of ambient pressure. The method considers the detailed inviscid interaction between the primary and secondary streams within the mixing tube and an estimate is made of the secondary flow entrained by the two-stream viscous mixing region. The validity of the theory is tested by comparing the performance characteristics of an experimental ejector facility with theoretical predictions and by comparing the theoretical flow field, in terms of constant density contours, with infinite fringe interferograms.

Theory Versus Experiment for Short (L/D = 1/6) Honeycomb and Smooth Annular Pressure Seals

1993 ◽  
Author(s):  
Dara W. Childs ◽  
George F. Kleynhans
Keyword(s):  
Pressure Ratio ◽  
Surface Friction ◽  
Computer Code ◽  
Cell Width ◽  
Rotordynamic Coefficients ◽  
Test Parameters ◽  
Theoretical Predictions ◽  
Theory Versus ◽  
Honeycomb Cell ◽  
Parameter Ranges

Abstract A study which compares theoretical predictions of experimental rotordynamic and leakage results is presented for short (L/D = 1/6) honeycomb and smooth annular pressure seals. A computer code used in this comparison has been developed from a theory that employs a perturbation analysis of the governing equations flow and uses Moody’s pipe friction relationship for the surface friction of the rotor and stator. This study was undertaken to investigate how well an existing code could predict these characteristics with input provided from recorded test data and independent flat-plate tests. The results examine the effect that the following independent test parameters have on the experimental measurements and theoretical predictions: inlet preswirl, rotor speed, inlet pressure, pressure ratio across seal, seal clearance, and honeycomb cell width. Experimental results show that leakage is reduced by decreasing the honeycomb cell width. Rotordynamically, the short seals are stabilizing over all test parameter ranges. However, the short seals did not perform as favorably as longer (L/D = 1/3) seals. In general, the theory overpredicts rotordynamic coefficients and leakage.

scholarly journals Firn Densification: An Empirical Model

1980 ◽  
Vol 25 (93) ◽  
pp. 373-385 ◽  
Author(s):  
Michael M. Herron ◽  
Chester C. Langway
Keyword(s):  
Empirical Model ◽  
Accumulation Rate ◽  
Rate Equations ◽  
Constant Density ◽  
Square Root ◽  
Accumulation Rates ◽  
Densification Rate ◽  
Second Stage ◽  
The Mean ◽  
Two Stages

AbstractAn empirical model of firn densification from the surface to the zone of pore close-off has been constructed. Fundamental rate equations have been derived for the first two stages of densification. In the first stage, for densities less than 0.55 Mg m−3, the densification rate is proportional to the mean annual accumulation times the term (ρi − ρ), where ρ is the density of the snow and ρi is the density of pure ice. The densification rate in the second stage, where 0.55 Mg m −3 < ρ < 0.8 Mg m−3, is proportional to the square root of the accumulation rate and to (ρi− ρ). Depth–density and depth–age calculations from this model are compared with observation. Model accumulation rates are within about 20% of values obtained by other techniques. It is suggested that depth intervals of constant density in some Antarctic cores may represent a synchronous event in the 1880 ’s when ten times the normal accumulation fell within a year or two.

scholarly journals Integrated Cross Sections of the Photo-Neutron Reactions Induced on \(^{197}\)Au with 60 \(\text{MeV}\) Bremsstrahlung

2020 ◽  
Vol 30 (1) ◽  
pp. 49
Author(s):  
Nguyen Van Do ◽  
Nguyen Thanh Luan ◽  
Nguyen Thi Xuan ◽  
Pham Duc Khue ◽  
Kim Tien Thanh ◽  
...  
Keyword(s):  
Cross Sections ◽  
Gamma Ray ◽  
Computer Code ◽  
Experimental Results ◽  
Point Energy ◽  
Spectrometric Technique ◽  
End Point ◽  
Theoretical Predictions ◽  
Neutron Reactions ◽  
First Time

Abstract. Seven photo-neutron reactions 197Au(γ,xn)197-xAu (with x=1-7) produced by the bremsstrahlung end-point energy of 60 MeV were identified. In this work, we focus on the measurement of integrated sections. Experiments were carried out based on the activation method in combination with off-line gamma-ray spectrometric technique. The integrated cross sections of the investigated reactions were determined relative to that of the monitoring reaction 197Au(γ,n)196Au. To validate the experimental results, theoretical predictions were also made using the computer code TALYS 1.9. The current integrated cross-sections of the 197Au(γ,xn)197-xAu reactions with 60 MeV bremsstrahlung end point energy are measured for the first time.

scholarly journals Auctions with external incentives: experimental evidence

2020 ◽  
Vol 49 (4) ◽  
pp. 1003-1043
Author(s):  
Miguel A. Fonseca ◽  
Francesco Giovannoni ◽  
Miltiadis Makris
Keyword(s):  
Experimental Evidence ◽  
Bidding Behavior ◽  
Second Stage ◽  
Theoretical Predictions ◽  
External Incentives ◽  
The Way

AbstractWe consider auctions where bidders’ valuations are positively correlated with their productivity in a second-stage aftermarket. We test in the lab whether bidders recognize the opportunity to signal their productivity through their bidding and, conditional on them doing so, whether disclosing different information about the auction outcomes affects their signaling behavior. Our results confirm that bidders recognize the signaling opportunities they face and also react to differences in the way their bidding behavior is disclosed, although not always in a way that is consistent with theoretical predictions.

A Note on the Accuracy of Similar Solutions of the Equations for Laminar Boundary Layers on Curved Surfaces

1969 ◽  
Vol 73 (699) ◽  
pp. 226-228 ◽  
Author(s):  
B. S. Massey ◽  
B. R. Clayton
Keyword(s):  
Stokes Equations ◽  
Single Equation ◽  
Navier Stokes ◽  
Constant Density ◽  
Curved Surfaces ◽  
Two Dimensional ◽  
Navier Stokes Equations ◽  
Laminar Boundary Layers ◽  
Density Flow ◽  
Similar Solutions

Summary To describe steady, two-dimensional, constant-density flow in a laminar boundary layer on a curved surface, a single equation may be derived from the complete Navier-Stokes equations, with no approximations being necessary. The conditions under which similar solutions are attainable are discussed, and the validity of some previous calculations is upheld.

Some Generalizations in One-Dimensional Constant Density Fluid Dynamics

1962 ◽  
Vol 84 (1) ◽  
pp. 44-48
Author(s):  
William G. Steltz ◽  
Robert P. Benedict
Keyword(s):  
Pressure Ratio ◽  
Isothermal Flow ◽  
Direct Application ◽  
Constant Density ◽  
Flow Function ◽  
Flow Process ◽  
One Dimensional ◽  
Flow Maps ◽  
Density Flow ◽  
Flow Processes

We present a Generalized Constant Density Flow Function, Γ, which is shown to have direct application in the treatment of many simplified, workless, one-dimensional flow processes. Those particular flow processes treated in this paper are: the familiar adiabatic flows, with or without friction, with area variations always allowed; and diabatic flows with or without friction, with area variations always allowed. Moreover, the Γ function is shown to have significance in a generalized flow process having an arbitrary combination of heat transfer, friction, and area and elevation variation. Development of the Γ function is given in some detail. Schematic isentropic, Fanno, Rayleigh, and isothermal flow maps are presented in terms of the conventional enthalpy—entropy diagram, and again in terms of the pressure ratio—Γ diagram. Numerical examples are included to illustrate the solution of typical problems through use of the Generalized Constant Density Flow Function.

Instability Mechanism in a Swirl Flow Combustor: Precession of Vortex Core and Influence of Density Gradient

2015 ◽  
Author(s):  
Kiran Manoharan ◽  
Samuel Hansford ◽  
Jacqueline O’ Connor ◽  
Santosh Hemchandra
Keyword(s):  
Gas Turbine ◽  
Density Gradient ◽  
Vortex Core ◽  
Temporal Analysis ◽  
Flame Stabilization ◽  
Base Flow ◽  
Constant Density ◽  
Flow Profile ◽  
Swirl Flows ◽  
Density Flow

Combustion instability is a serious problem limiting the operating envelope of present day gas turbine systems using a lean premixed combustion strategy. Gas turbine combustors employ swirl as a means for achieving fuel-air mixing as well as flame stabilization. However swirl flows are complex flows comprised of multiple shear layers as well as recirculation zones which makes them particularly susceptible to hydrodynamic instability. We perform a local stability analysis on a family of base flow model profiles characteristic of swirling flow that has undergone vortex breakdown as would be the case in a gas turbine combustor. A temporal analysis at azimuthal wavenumbers m = 0 and m = 1 reveals the presence of two unstable modes. A companion spatio-temporal analysis shows that the region in base flow parameter space for constant density density flow, over which m = 1 mode with the lower oscillation frequency is absolutely unstable, is much larger that that for the corresponding m = 0 mode. This suggests that the dominant self-excited unstable behavior in a constant density flow is an asymmetric, m=1 mode. The presence of a density gradient within the inner shear layer of the flow profile causes the absolutely unstable region for the m = 1 to shrink which suggests a possible explanation for the suppression of the precessing vortex core in the presence of a flame.

Firn Densification: An Empirical Model

1980 ◽  
Vol 25 (93) ◽  
pp. 373-385 ◽  
Author(s):  
Michael M. Herron ◽  
Chester C. Langway
Keyword(s):  
Empirical Model ◽  
Accumulation Rate ◽  
Rate Equations ◽  
Constant Density ◽  
Square Root ◽  
Accumulation Rates ◽  
Densification Rate ◽  
Second Stage ◽  
The Mean ◽  
Two Stages

AbstractAn empirical model of firn densification from the surface to the zone of pore close-off has been constructed. Fundamental rate equations have been derived for the first two stages of densification. In the first stage, for densities less than 0.55 Mg m−3, the densification rate is proportional to the mean annual accumulation times the term (ρi−ρ), whereρis the density of the snow andρiis the density of pure ice. The densification rate in the second stage, where 0.55 Mg m−3&lt; ρ &lt; 0.8 Mg m−3, is proportional to the square root of the accumulation rate and to (ρi−ρ). Depth–density and depth–age calculations from this model are compared with observation. Model accumulation rates are within about 20% of values obtained by other techniques. It is suggested that depth intervals of constant density in some Antarctic cores may represent a synchronous event in the 1880 ’s when ten times the normal accumulation fell within a year or two.

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