scholarly journals Experimental and numerical studies on combustion characteristics of N 2 -diluted CH 4 and O 2 diffusion combustion in a packed bed

2019 ◽  
Vol 6 (9) ◽  
pp. 190492 ◽  
Author(s):  
Houping Li ◽  
Junrui Shi ◽  
Mingming Mao ◽  
Yongqi Liu
Keyword(s):  
Diffusion Processes ◽  
Packed Bed ◽  
Gas Diffusion ◽  
Combustion Characteristics ◽  
Pollutant Emission ◽  
Diffusion Combustion ◽  
No Emission ◽  
Numerical Studies ◽  
And Diffusion ◽  
Co Emission

Experimental and numerical studies were conducted to determine the combustion characteristics of gas diffusion combustion in a porous combustor packed with 2.5 mm or 3.5 mm alumina pellets, special attention being focused on the effect of packed bed height ( h ) on combustion, NO and CO emissions. The pollutant emission of diffusion filtration combustion is studied with different packed bed lengths in the range of 40 mm ≤ h ≤ 240 mm, fixed excess air ratio of 1.88 and fixed gas inlet velocity of 0.06 m s −1 . Results show that both immersed and surface flames coexist in the combustor. Although porous media enhance the mixing and diffusion processes, the diffusion flame shape is still observed from the side and top views of the combustor, and the diffusion filtration retains properties of diffusion combustion. The immersed flame is always observed with increase in h , whereas the height of surface flame decreases. The NO emission decreases sharply when h is increased from 40 mm to 120 mm. However, the NO emission decreases slightly when h > 120 mm. In the investigated range of h , it is shown that h has a significant influence on the CO emission, an increase in h leading to a constant increase in CO for the combustors packed with 2.5 mm or 3.5 mm pellets. The maximum CO emission is 662 ppm and the minimum value is 67 ppm. In the scope of this study, the temperature on the external wall of the combustor reaches 434–513°C.

Numerical Simulation Analysis of Dangerous Heavy Gas Leakage and Diffusion

2013 ◽  
Vol 726-731 ◽  
pp. 1354-1357
Author(s):  
Ning Zhou ◽  
Wei Cui ◽  
Kai Quan Wang ◽  
Hui Jun Zhao
Keyword(s):  
Wind Velocity ◽  
Diffusion Processes ◽  
Air Entrainment ◽  
Gas Diffusion ◽  
Gas Concentration ◽  
Gas Leakage ◽  
Tank Farm ◽  
Gravity Settling ◽  
Heavy Gas ◽  
And Diffusion

Using Fluent to simulate dangerous heavy gas leakage and diffusion of oil tank farm under different conditions. The analysis results show that the diffusion processes of heavy gas can be divided into four stages like gravity settling stage, air entrainment stage, cloud heating stage and the stage of transformation to the non-heavy gas diffusion. While the gas leakage occurs in the middle position of the tank farm, the gas diffusion speed is slow and the gas concentration is easy to achieve the explosive limit. When the wind velocity is 0.95 m/s, the diffusion velocity of heavy gas increases with the wind velocity, gas concentrations rises obviously. When the wind velocity reaches to 1.7 m/s, the gas concentration will reach the peak, as the wind velocity increases, the gas concentration reduces slowly.

Effect of Fuel Dilution on the Structure and Pollutant Emission of Syngas Diffusion Flames

2007 ◽  
Author(s):  
Xin Hui ◽  
Zhedian Zhang ◽  
Kejin Mu ◽  
Yue Wang ◽  
Yunhan Xiao
Keyword(s):  
Diffusion Flames ◽  
Flame Temperature ◽  
Nox Emission ◽  
Pollutant Emissions ◽  
Pollutant Emission ◽  
No Emission ◽  
Exhaust Temperature ◽  
Fuel Dilution ◽  
Fuel Stream ◽  
Co Emission

Combustion with diluted syngas is important for integrated gasification combined cycle (IGCC) system that attains high efficiency and low pollutant emissions. In syngas diffusion flames, peak flame temperature is higher than that in nature gas flames, so NOx emission is more significant. To achieve low NOx emission, fuel dilution is an effective way. In the present study, Flame structure and emission characteristics were experimentally and numerically studied in various fuel diluted syngas diffusion flames, and H2O, N2 and CO2 were employed as diluents respectively. The purpose of this paper is to better understand the behavior and mechanism of fuel diluted combustion and to provide fundamental data base for the development of syngas combustion techniques. Experiments were conducted by using jet diffusion flames in a model combustor. Flame size, exhaust temperature and emission concentration were measured. It was found that by introducing diluents into fuel stream, the stoichiometric surface was brought inward, namely the flame envelope shrunk due to a relatively low fuel concentration. The exhaust temperature was decreased. The results also indicated that with diluted fuel stream, there was an increase of CO emission and an apparent decrease of NO emission. For the same exhaust temperature, H2O had the most significant influence on NO emission among the three diluents, while CO2 affected CO emission most by inhibiting its oxidation thermally and chemically. Numerical simulations were performed in counterflow diffusion flames by applying Chemkin software. To reveal the mechanisms of various diluents in flames, the detailed chemistry of H2-CO-N2 system was employed. It was found that the concentration of OH radical is important for both NO and CO emissions. The OH concentration is affected not only by the type of diluents but also by the flame temperature, therefore it is determined by the coupling and competition of diluents’ chemical and thermal effects.

scholarly journals Trap, ignition, and diffusion combustion characteristics of active carbon micro-particles at a meso-scale studied by optical tweezers

2014 ◽  
Vol 63 (17) ◽  
pp. 178802
Author(s):  
Huang Xue-Feng ◽  
Li Sheng-Ji ◽  
Zhou Dong-Hui ◽  
Zhao Guan-Jun ◽  
Wang Guan-Qing ◽  
...  
Keyword(s):  
Optical Tweezers ◽  
Active Carbon ◽  
Combustion Characteristics ◽  
Diffusion Combustion ◽  
Micro Particles ◽  
And Diffusion ◽  
Meso Scale

Meridional Circulation, Turbulence, and Diffusion Processes in Stars

1976 ◽  
Vol 32 ◽  
pp. 109-116 ◽  
Author(s):  
S. Vauclair
Keyword(s):  
Convection Zone ◽  
Diffusion Processes ◽  
Meridional Circulation ◽  
Diffusion Time ◽  
Work In Progress ◽  
First Results ◽  
Stellar Envelopes ◽  
And Diffusion ◽  
Turbulence And Diffusion ◽  
Hr Diagram

This paper gives the first results of a work in progress, in collaboration with G. Michaud and G. Vauclair. It is a first attempt to compute the effects of meridional circulation and turbulence on diffusion processes in stellar envelopes. Computations have been made for a 2 Mʘstar, which lies in the Am - δ Scuti region of the HR diagram.Let us recall that in Am stars diffusion cannot occur between the two outer convection zones, contrary to what was assumed by Watson (1970, 1971) and Smith (1971), since they are linked by overshooting (Latour, 1972; Toomre et al., 1975). But diffusion may occur at the bottom of the second convection zone. According to Vauclair et al. (1974), the second convection zone, due to He II ionization, disappears after a time equal to the helium diffusion time, and then diffusion may happen at the bottom of the first convection zone, so that the arguments by Watson and Smith are preserved.

NMR-Study of Structure and Diffusion Processes in Li3N

1980 ◽  
Vol 41 (C6) ◽  
pp. C6-28-C6-31 ◽  
Author(s):  
R. Messer ◽  
H. Birli ◽  
K. Differt
Keyword(s):  
Diffusion Processes ◽  
Nmr Study ◽  
And Diffusion

Effect of cluster-gradient architecture of nanostructured topocomposites on features of tribointeraction with heterophased material

2020 ◽  
pp. 130-135
Author(s):  
D.N. Korotaev ◽  
K.N. Poleshchenko ◽  
E.N. Eremin ◽  
E.E. Tarasov
Keyword(s):  
Wear Resistance ◽  
Titanium Alloy ◽  
Energy Dissipation ◽  
Phase Structure ◽  
Diffusion Processes ◽  
Structural Phase ◽  
High Wear Resistance ◽  
Wear Characteristics ◽  
And Diffusion

The wear resistance and wear characteristics of cluster-gradient architecture (CGA) nanostructured topocomposites are studied. The specifics of tribocontact interaction under microcutting conditions is considered. The reasons for retention of high wear resistance of this class of nanostructured topocomposites are studied. The mechanisms of energy dissipation from the tribocontact zone, due to the nanogeometry and the structural-phase structure of CGA topocomposites are analyzed. The role of triboactivated deformation and diffusion processes in providing increased wear resistance of carbide-based topocomposites is shown. They are tested under the conditions of blade processing of heat-resistant titanium alloy.

Certain Problems with the Application of Stochastic Diffusion Processes for the Description of Chemical Engineering Phenomena. Diffusional Change of Solid Particle Size

1996 ◽  
Vol 61 (4) ◽  
pp. 536-563
Author(s):  
Vladimír Kudrna ◽  
Pavel Hasal
Keyword(s):  
Particle Size ◽  
Solid Particle ◽  
Chemical Engineering ◽  
Diffusion Processes ◽  
Granular Systems ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Diffusion Term ◽  
Population Balances ◽  
And Diffusion

To the description of changes of solid particle size in population, the application was proposed of stochastic differential equations and diffusion equations adequate to them making it possible to express the development of these populations in time. Particular relations were derived for some particle size distributions in flow and batch equipments. It was shown that it is expedient to complement the population balances often used for the description of granular systems by a "diffusion" term making it possible to express the effects of random influences in the growth process and/or particle diminution.

Liquid Droplet Dispersion in a Rotating Packed Bed: Experimental and Numerical Studies

2021 ◽  
pp. 116675
Author(s):  
Ying Wang ◽  
Yan-Bin Li ◽  
Meng-Jun Su ◽  
Guang-Wen Chu ◽  
Bao-Chang Sun ◽  
...  
Keyword(s):  
Liquid Droplet ◽  
Packed Bed ◽  
Droplet Dispersion ◽  
Numerical Studies ◽  
Rotating Packed Bed

scholarly journals Influence of Geometry on Thin Layer and Diffusion Processes at Carbon Electrodes

Langmuir ◽  
2021 ◽  
Author(s):  
Qun Cao ◽  
Zijun Shao ◽  
Dale K. Hensley ◽  
Nickolay V. Lavrik ◽  
B. Jill Venton
Keyword(s):  
Thin Layer ◽  
Diffusion Processes ◽  
Carbon Electrodes ◽  
And Diffusion
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