Determining the Hydrogen Mass Fraction, Concentration Distributions and Related Flow Properties in a Subsonic Turbulent Mixing Region with a Multi-Species Co-Flow

2010 ◽  
Author(s):  
Alexander Gonor ◽  
Vitali Khaikine ◽  
James Gottlieb ◽  
Isaiah Blankson
Keyword(s):  
Turbulent Mixing ◽  
Mass Fraction ◽  
Flow Properties ◽  
Hydrogen Mass

Hydrogen Storage in Small Size Hollow Microspheres

2012 ◽  
Vol 512-515 ◽  
pp. 1395-1399 ◽  
Author(s):  
Zhan Wen Zhang ◽  
Su Fen Chen ◽  
Yi Yang Liu ◽  
Lin Su ◽  
Mei Fang Liu ◽  
...  
Keyword(s):  
High Pressure ◽  
Elevated Temperature ◽  
Hydrogen Storage ◽  
Vapor Deposition ◽  
Mass Fraction ◽  
Hoop Stress ◽  
Hydrogen Gas ◽  
Hollow Microspheres ◽  
Hydrogen Mass ◽  
Pressure Hydrogen

Hollow microspheres with less than 1 millimeter in diameter and several micrometers in wall thickness are attractive for hydrogen storage and transportation. The hollow microspheres can be made by drop tower technique, microencapsulation and vapor deposition methods. By immersion in high pressure hydrogen for a period of time at elevated temperature, the hollow microspheres can be filed with hydrogen gas at pressures up to one hundred MPa. The hydrogen mass fraction can be varied from 1% to 10% for hollow microspheres with different membrane hoop stress at failure.

Ejector-Nozzle Flow and Thrust

1960 ◽  
Vol 82 (1) ◽  
pp. 120-129 ◽  
Author(s):  
H. E. Weber
Keyword(s):  
Nozzle Exit ◽  
Turbulent Mixing ◽  
Basic Assumption ◽  
Small Distance ◽  
Momentum Thickness ◽  
Flow Properties ◽  
Thrust Coefficient ◽  
Ejector Nozzle ◽  
Momentum Integral ◽  
Secondary Stream

An analysis for predicting the secondary and primary flows and the thrust coefficient of ejector nozzles is presented. Particular attention is given to the diverging shroud ejector in which the throat of the secondary stream is formed at a small distance down-stream of the primary nozzle exit; i.e., near the plane of the minimum shroud area. The basic assumption in the analysis is that the shroud is sufficiently short so that the mixing of the two streams is incomplete, and that both streams have isentropic cores. The momentum thickness of the mixing region is obtained from the momentum-integral equation for the turbulent mixing region assuming that momentum and temperature diffuse at the same rate. The momentum thickness at the nozzle exit is related to the initial momentum thickness created by the wall separating the two streams. The exit-momentum thicknesses of the mixing region and the wall are used to obtain the actual thrust coefficient. Experimental data on primary-secondary flow properties and thrust coefficients of a divergent-shroud ejector nozzle show good correlation with the theory.

scholarly journals Exergy Analysis in Hydrogen-Air Detonation

2012 ◽  
Vol 2012 ◽  
pp. 1-16 ◽  
Author(s):  
Abel Rouboa ◽  
Valter Silva ◽  
Nuno Couto
Keyword(s):  
Mass Fraction ◽  
Exergy Analysis ◽  
Fluid Dynamic ◽  
Time Discretization ◽  
Euler System ◽  
Total Enthalpy ◽  
Finite Volume Discretization ◽  
System Equations ◽  
Hydrogen Mass ◽  
Exergy Losses

The main goal of this paper is to analyze the exergy losses during the shock and rarefaction wave of hydrogen-air mixture. First, detonation parameters (pressure, temperature, density, and species mass fraction) are calculated for three cases where the hydrogen mass fraction in air is 1.5%, 2.5%, and 5%. Then, exergy efficiency is used as objective criteria of performance evaluation. A two-dimensional computational fluid dynamic code is developed using Finite volume discretization method coupled with implicit scheme for the time discretization (Euler system equations). A seven-species and five-step global reactions mechanism is used. Implicit total variation diminishing (TVD) algorithm, based on Riemann solver, is solved. The typical diagrams of exergy balances of hydrogen detonation in air are calculated for each case. The energy balance shows a successive conversion of kinetic energy, and total enthalpy, however, does not indicate consequent losses. On the other hand, exergy losses increase with the augment of hydrogen concentration in air. It obtained an exergetic efficiency of 77.2%, 73.4% and 69.7% for the hydrogen concentrations of 1.5%, 2.5%, and 5%, respectively.

scholarly journals A realistic two-dimensional model of Altair

2020 ◽  
Vol 633 ◽  
pp. A78 ◽  
Author(s):  
K. Bouchaud ◽  
A. Domiciano de Souza ◽  
M. Rieutord ◽  
D. R. Reese ◽  
P. Kervella
Keyword(s):  
Angular Velocity ◽  
Differential Rotation ◽  
Mass Fraction ◽  
Rotation Period ◽  
Position Angle ◽  
Young Star ◽  
Evolutionary Stage ◽  
Two Dimensional ◽  
Long Baseline ◽  
Hydrogen Mass

Context. Fast rotation is responsible for important changes in the structure and evolution of stars and the way we see them. Optical long baseline interferometry now allows for the study of its effects on the stellar surface, mainly gravity darkening and flattening. Aims. We aim to determine the fundamental parameters of the fast-rotating star Altair, in particular its evolutionary stage (represented here by the core hydrogen mass fraction Xc), mass, and differential rotation, using state-of-the-art stellar interior and atmosphere models together with interferometric (ESO-VLTI), spectroscopic, and asteroseismic observations. Methods. We use ESTER two-dimensional stellar models to produce the relevant surface parameters needed to create intensity maps from atmosphere models. Interferometric and spectroscopic observables are computed from these intensity maps and several stellar parameters are then adjusted using the publicly available MCMC algorithm Emcee. Results. We determined Altair’s equatorial radius to be Req = 2.008 ± 0.006 R⊙, the position angle PA = 301.1 ± 0.3°, the inclination i = 50.7 ± 1.2°, and the equatorial angular velocity Ω = 0.74 ± 0.01 times the Keplerian angular velocity at equator. This angular velocity leads to a flattening of ε = 0.220 ± 0.003. We also deduce from the spectroscopically derived v sin i ≃ 243 km s−1, a true equatorial velocity of ∼314 km s−1 corresponding to a rotation period of 7h46m (∼3 cycles/day). The data also impose a strong correlation between mass, metallicity, hydrogen abundance, and core evolution. Thanks to asteroseismic data, and provided our frequencies identification is correct, we constrain the mass of Altair to 1.86 ± 0.03 M⊙ and further deduce its metallicity Z = 0.019 and its core hydrogen mass fraction Xc = 0.71, assuming an initial solar hydrogen mass fraction X = 0.739. These values suggest that Altair is a young star ∼100 Myr old. Finally, the 2D ESTER model also gives the internal differential rotation of Altair, showing that its core rotates approximately 50% faster than the envelope, while the surface differential rotation does not exceed 6%.

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