scholarly journals Numerical Simulation of Magnesium Dust Dispersion and Explosion in 20 L Apparatus via an Euler–Lagrange Method

Energies ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 402
Author(s):  
Tao Fu ◽  
Yun-Ting Tsai ◽  
Qiang Zhou
Keyword(s):  
Ignition Time ◽  
Particle Dispersion ◽  
Maximum Pressure ◽  
Lagrange Method ◽  
Explosion Pressure ◽  
Experimental Apparatus ◽  
Pressure Development ◽  
Fluid Properties ◽  
Field Velocity ◽  
Dust Dispersion

Computational fluid dynamics (CFD) was used to investigate the explosion characteristics of a Mg/air mixture in a 20 L apparatus via an Euler–Lagrange method. Various fluid properties, namely pressure field, velocity field, turbulence intensity, and the degree of particle dispersion, were obtained and analyzed. The simulation results suggested that the best delayed ignition time was 60 ms after dust dispersion, which was consistent with the optimum delayed ignition time adopted by experimental apparatus. These results indicate that the simulated Mg particles were evenly diffused in the 20 L apparatus under the effect of the turbulence. The simulations also reveal that the pressure development in the explosion system can be divided into the pressure rising stage, the maximum pressure stage, and pressure attenuation stage. The relative error of the maximum explosion pressure between the simulation and the experiments is approximately 1.04%. The explosion model provides reliable and useful information for investigating Mg explosions.

scholarly journals Method to characterize directional changes in Arctic sea ice drift and associated deformation due to synoptic atmospheric variations using Lagrangian dispersion statistics

2017 ◽  
Vol 11 (4) ◽  
pp. 1707-1731 ◽  
Author(s):  
Jennifer V. Lukovich ◽  
Cathleen A. Geiger ◽  
David G. Barber
Keyword(s):  
Sea Ice ◽  
Single Particle ◽  
Weather Forecasting ◽  
Particle Dispersion ◽  
Arctic Sea Ice ◽  
Maximum Pressure ◽  
Dynamical Regime ◽  
Scaling Exponent ◽  
Ice Drift ◽  
Sea Ice Drift

Abstract. A framework is developed to assess the directional changes in sea ice drift paths and associated deformation processes in response to atmospheric forcing. The framework is based on Lagrangian statistical analyses leveraging particle dispersion theory which tells us whether ice drift is in a subdiffusive, diffusive, ballistic, or superdiffusive dynamical regime using single-particle (absolute) dispersion statistics. In terms of sea ice deformation, the framework uses two- and three-particle dispersion to characterize along- and across-shear transport as well as differential kinematic parameters. The approach is tested with GPS beacons deployed in triplets on sea ice in the southern Beaufort Sea at varying distances from the coastline in fall of 2009 with eight individual events characterized. One transition in particular follows the sea level pressure (SLP) high on 8 October in 2009 while the sea ice drift was in a superdiffusive dynamic regime. In this case, the dispersion scaling exponent (which is a slope between single-particle absolute dispersion of sea ice drift and elapsed time) changed from superdiffusive (α ∼ 3) to ballistic (α ∼ 2) as the SLP was rounding its maximum pressure value. Following this shift between regimes, there was a loss in synchronicity between sea ice drift and atmospheric motion patterns. While this is only one case study, the outcomes suggest similar studies be conducted on more buoy arrays to test momentum transfer linkages between storms and sea ice responses as a function of dispersion regime states using scaling exponents. The tools and framework developed in this study provide a unique characterization technique to evaluate these states with respect to sea ice processes in general. Application of these techniques can aid ice hazard assessments and weather forecasting in support of marine transportation and indigenous use of near-shore Arctic areas.

scholarly journals Gaseous combustion at high pressures. Part IV.—The influence of varying initial pressures upon the rate of pressure development and the activation of nitrogen in carbon monoxide-air explosions

1924 ◽  
Vol 105 (732) ◽  
pp. 406-433
Keyword(s):  
Carbon Monoxide ◽  
High Pressures ◽  
Vibrational Energy ◽  
Initial Pressure ◽  
Maximum Pressure ◽  
Time Interval ◽  
Pressure Development ◽  
The One ◽  
Air Explosion ◽  
Energy Absorbing

In the previous paper of this series it was shown :— (1) that when nitrogen is added as a diluent to a mixture of 2CO+O 2 undergoing combustion in a bomb at an initial pressure of 50 atmospheres, it exerts a peculiar energy-absorbing influence upon the system, far beyond that of other diatomic gases, or of argon; (2) that by virtue of such influence, it retards the attainment of maximum pressure in a much greater degree than can be accounted for on the supposition of its acting merely as a diatomic diluent; (3) that the energy so absorbed by the nitrogen during the combustion period, which extends right up to the attainment of maximum pressure, is slowly liberated thereafter as the system cools down ; and that consequently the rate of cooling is greatly retarded for a considerable time interval after the attainment of maximum pressure; (4) that there is no such energy-absorbing effect ( i. e ., other than a purely "diluent" one) when nitrogen is present in a 2H 2 +O 2 mixture similarly undergoing combustion ; but that, on the contrary, the presence of hydrogen in a CO-air mixture undergoing combustion at such high pressures so strongly counteracts the said " energy-absorbing " influence of the nitrogen, that it must be excluded as far as possible from the system before any large nitrogen-effect can be observed. These facts were explained on the supposition that there is some constitutional correspondence between CO and N 2 molecules (whose densities are identical) whereby the vibrational energy (radiation) emitted when the one burns is of such a quality as can be readily absorbed by the other, the two thus acting in resonance. It was further supposed that, in consequence of such resonance, nitrogen becomes chemically " activated " when present during the combustion of carbon monoxide at such high pressures ; and in conformity with this supposition, it was shown that such "activated" nitrogen is able to combine with oxygen more readily than does nitrogen which has merely been raised to a correspondingly high temperature in a hydrogen-air explosion.

Cardiac dysfunction after acute endotoxin administration in conscious sheep

1991 ◽  
Vol 260 (5) ◽  
pp. H1474-H1481 ◽  
Author(s):  
K. Sugi ◽  
J. Newald ◽  
L. D. Traber ◽  
J. P. Maguire ◽  
D. N. Herndon ◽  
...  
Keyword(s):  
Sham Group ◽  
Systolic Pressure ◽  
Simultaneous Increase ◽  
Maximum Pressure ◽  
Ovine Model ◽  
Myocardial Depression ◽  
Dimension Analysis ◽  
Pressure Development ◽  
Pulmonary Arterial ◽  
Conscious Sheep

We evaluated cardiac function in an unanesthetized ovine model of hyperdynamic endotoxemia. The animals were instrumented for crystallographic dimension analysis of the left ventricle (LV) and measurement of LV, aortic, atrial, central venous, and pulmonary arterial pressures, and cardiac output. Seven sheep received 1.5 micrograms/kg of Escherichia coli endotoxin [lipopolysaccharide (LPS) LPS-P group] and were compared to a sham group. The sham group demonstrated no significant change in any of the variables. In the LPS-P group, the cardiac index increased (5.7 +/- 0.4 to 7.9 +/- 0.6 l.min-1.m-2) between 8 and 12 h after LPS. Concomitantly, the maximum elastance of LV end-systolic pressure-volume relations significantly decreased (2.88 +/- 0.27 mmHg/ml) compared with baseline (3.89 +/- 0.50 mmHg/ml). Other indexes of the LV contractility (maximum pressure development and ejection fraction) were also reduced. There was a simultaneous increase in the LV end-systolic and diastolic volumes. These findings confirm the hypothesis that there is a myocardial depression during LPS in the ovine model.

scholarly journals The dissociation of carbon dioxide at high temperatures

1927 ◽  
Vol 115 (771) ◽  
pp. 318-333 ◽  
Keyword(s):  
Carbon Dioxide ◽  
High Temperatures ◽  
Combustion Engine ◽  
Initial Pressure ◽  
Simple Relation ◽  
Maximum Temperature ◽  
Maximum Pressure ◽  
Complete Combustion ◽  
Explosion Pressure ◽  
Rich Mixture

The power of an internal combustion engine is greatest when operating with a “rich” mixture, that is to say, with a mixture which contains more fuel than is necessary for complete combustion. Similarly, it is found that if mixtures of carbon monoxide and air in varying proportions are exploded in a closed bomb at constant initial temperature and pressure, the explosion pressure is greatest when the ratio CO/O 2 is greater than 2. These phenomena are known to be connected with the dissociation of carbon dioxide at high temperatures, for if there were no dissociation we should expect the explosion pressure to be greatest when CO/O 2 = 2. No attention appears, however, to have been paid to the position of the maximum. It can be shown in the following way that there is a very simple relation between the composition of the mixture giving maximum pressure on explosion, and the dissociation of carbon dioxide at the maximum explosion temperature. Let the initial composition be represented by the expression 2 (1 + a ) CO + O 2 + b N 2 (Total mols = 3 + 2 a + b ), and let P i , T i represent the initial pressure and temperature; P e the maximum pressure observed after explosion, and T e the corresponding maximum temperature.

Modelling of Hydraulic Seals Using an Axisymmetric Volume of Fluid Method (VOF)

2013 ◽  
Author(s):  
Hans-Christian Mathews ◽  
Hervé Morvan ◽  
Davide Peduto ◽  
Yi Wang ◽  
Colin Young ◽  
...  
Keyword(s):  
Design Method ◽  
Analytical Calculation ◽  
Volume Of Fluid ◽  
Numerical Results ◽  
Dimensionless Number ◽  
Maximum Pressure ◽  
Oil Consumption ◽  
Fluid Properties ◽  
Calculation Results ◽  
Aero Engines

Hydraulic seals are used in aero engines because of their excellent sealing properties. Sealing of oil inside bearing chambers is extremely important as leakage of oil into internal spaces of the engine increases the oil consumption and can result in undesirable effects, ranging from cosmetic to mechanical. A robust dimensioning of the seal is therefore essential. However, the maximum pressure capacity of the hydraulic seal is not always determined accurately enough with many of the existing design approaches, so a high safety factor must be used. It is desirable to keep improving the accuracy of these methods, in particular to handle ever larger pressure differences. A new dimensionless design method is therefore introduced here to improve the determination of the maximum pressure capacity. This paper reports on a numerical CFD investigation using an axisymmetric Volume-of-Fluid (VOF) method building on the work of Young and Chew [1]. The numerical results are validated with the results of a two-shaft test rig, alongside analytical calculation results. Additionally, a parametric study based on CFD simulations is performed to identify dominant influence quantities. The parameters include the fluid properties of oil, the shaft speeds and the geometry parameters of the seal. Employing a data reduction approach, a new dimensionless number is introduced which allows the presentation of experimental and numerical results of the hydraulic seal in a dimensionless form. Based on this representation, a correlation is proposed, which shows a very promising trend. This validated CFD investigation and subsequent correlation introduced here show significant potential for the dimensionless description of hydraulic seals and their maximum pressure capacity.

scholarly journals Flow Characteristics of the Raw Sewage for the Design of Sewage-Source Heat Pump Systems

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Ying Xu ◽  
Yuebin Wu ◽  
Qiang Sun
Keyword(s):  
Turbulent Flow ◽  
Heat Pump ◽  
Power Law ◽  
Loss Factor ◽  
Flow Characteristics ◽  
Power Law Fluid ◽  
Frictional Loss ◽  
Experimental Apparatus ◽  
Fluid Properties ◽  
Sewage Source

The flow characteristics of raw sewage directly affect the technical and economic performance of sewage-source heat pump systems. The purpose of this research is to characterize the flow characteristics of sewage by experimental means. A sophisticated and flexible experimental apparatus was designed and constructed. Then the flow characteristics of the raw sewage were studied through laboratorial testing and theoretical analyses. Results indicated that raw sewage could be characterized as a power-law fluid with the rheological exponentnbeing 0.891 and the rheological coefficientkbeing 0.00175. In addition, the frictional loss factor formula in laminar flow for raw sewage was deduced by theoretical analysis of the power-law fluid. Furthermore, an explicit empirical formula for the frictional loss factor in turbulent flow was obtained through curve fitting of the experimental data. Finally, the equivalent viscosity of the raw sewage is defined in order to calculate the Reynolds number in turbulent flow regions; it was found that sewage had two to three times the viscosity of water at the same temperature. These results contributed to appropriate parameters of fluid properties when designing and operating sewage-source heat pump systems.

scholarly journals A new shock-wave test apparatus for liquid CO2 blasting and measurement analysis

2019 ◽  
Vol 52 (5-6) ◽  
pp. 399-408 ◽  
Author(s):  
Ying Chen ◽  
Hongwei Zhang ◽  
Zhijie Zhu ◽  
Tingxiang Ren ◽  
Chen Cao ◽  
...  
Keyword(s):  
Shock Wave ◽  
Scientific Basis ◽  
Maximum Pressure ◽  
Rock Body ◽  
Wave Pressure ◽  
Fixed Ring ◽  
Measurement Analysis ◽  
Experimental Apparatus ◽  
Shock Wave Pressure ◽  
The Stability

Liquid CO2 blasting of coal or rock body technology is widely used for improving permeability, pressure relief, cutting proof, and roadway development. Due to the lack of proper apparatus for blasting measurement, the determination of blasting parameters is often not under scientific basis. A newly designed experimental apparatus is developed to monitor shock-wave pressure of liquid CO2 blasting. The apparatus mainly consists of testing tube and base bracket. The testing tube is fixed on the base bracket by fixed ring. The base bracket is fixed to the ground by expansion bolts to ensure the stability of the apparatus and personnel safety during blasting. Three testing tubes with inner diameter of 48, 68, and 82 mm are designed and manufactured to simulate different sizes of boreholes. Monitoring holes are drilled on the testing tube to monitor blasting shock-wave pressure in real time. The maximum pressure of the shock-wave and its acting duration can be obtained. Experimental results also revealed that the normal direction of the gas outlet is the effective shock-wave acting area where the maximum pressure reaches more than 160 MPa. The shock-wave pressure is in non-linear relationship with the distance from gas outlet. By comparison of the blasting tube sealed to unsealed condition, it is found that sealing can be effected by increment in shock-wave pressure of about 43.3%. The research results provide a basis and reference work for determination and optimization of liquid CO2 blasting parameters.

scholarly journals Numerical simulation of dust explosion in the spherical 20l vessel

2015 ◽  
Vol 63 (1) ◽  
pp. 289-293 ◽  
Author(s):  
Z. Salamonowicz ◽  
M. Kotowski ◽  
M. Półka ◽  
W. Barnat
Keyword(s):  
Numerical Simulation ◽  
Numerical Simulations ◽  
Combustion Process ◽  
Test Stand ◽  
Maximum Pressure ◽  
Dust Explosion ◽  
Computational Domain ◽  
Dispersion Process ◽  
Dust Dispersion ◽  
Positive Agreement

Abstract The paper presents experimental and numerical validation of the combustion process of coal and flour dust dispersed in a spherical chamber of 20 cubic decimetres volume. The aim of the study is to validate the numerical simulation results in relation to the experimental data obtained on the test stand. To perform the numerical simulations, a Computational Fluid Dynamics code FLUENT was used. Geometry of the computational domain was built in compliance with EN 14460. Numerical simulations were divided into two main steps. The first one consists in a dust dispersion process, where influence of standardized geometry was verified. The second part of numerical simulations investigated dust explosion characteristics in compliance with EN 14034. After several model modifications, outcomes of the numerical analysis shows positive agreement with both, the explosion characteristics for different dust concentration levels and the maximum pressure increase obtained on the test stand.

Indonesia Coal Explosive Characteristic of Pulverized Coal in Experiment

2011 ◽  
Vol 418-420 ◽  
pp. 706-711
Author(s):  
Jia Hu Li ◽  
Li Bao Yin
Keyword(s):  
Pulverized Coal ◽  
Maximum Pressure ◽  
Explosion Pressure ◽  
Maximum Explosion Pressure

In this paper, the explosion experiments of Indonesia pulverized coal cloud are carried out. The pressure histories are recorded. The maximum pressure, the maximum pressure rising rates and the explosion time are analysed based on the pressure histories. The experiment results indicate that with the increase of pulverized coal concentration, the maximum explosion pressure and maximum pressure rising rate at first increases, then decreases, and the explosion time is contrary to that.

scholarly journals Anisotropic Lagrangian Dispersion in Rotating Flows with a β Effect

2014 ◽  
Vol 44 (2) ◽  
pp. 632-643 ◽  
Author(s):  
Stefania Espa ◽  
Guglielmo Lacorata ◽  
Gabriella Di Nitto
Keyword(s):  
Particle Dispersion ◽  
Physical Parameters ◽  
Rotating Turbulence ◽  
Tracer Dispersion ◽  
Anisotropy Index ◽  
Wide Range ◽  
Experimental Apparatus ◽  
Theoretical Predictions ◽  
Degree Of Anisotropy ◽  
Lagrangian Dispersion

Abstract A detailed analysis of Lagrangian tracer dispersion is performed on datasets obtained from laboratory experiments that simulate rotating turbulence in the presence of a β effect. Compatible with the limitations of the experimental apparatus, a relatively wide range of the zonostrophy index Rβ, a parameter used to characterize flow regimes in β-plane turbulence, is explored. The considered range spans from values ~O(10−1), for which the flow is nearly isotropic, to values ~O(1), corresponding to the so-called transitional range in which the flow gradually leaves the friction-dominated regime to enter the full zonostrophic regime. The degree of anistropy and the characteristic scales of the flow have been estimated by means of a Lagrangian approach based on the reconstruction of tracer trajectories and on the measure of the finite-scale Lyapunov exponents (FSLE). The FSLE analysis allows one to identify the regimes of two-particle dispersion and to relate them to the physical parameters of the system. Moreover, a Lagrangian anisotropy index (LAI) is introduced and defined in terms of the FSLE zonal and radial components, in order to describe the onset of anisotropy and to check if it is consistent with the theoretical predictions. It is remarkable that the finite-scale dispersion rates are very sensitive to the degree of anistropy of turbulence, more so than other indicators defined in terms of Eulerian quantities. Furthermore, they offer an effective diagnostic tool of the degree of anisotropy that can be used even prior to attaining a fully developed regime of zonostrophic turbulence.

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