scholarly journals Analysis of Gaseous and Gaseous-Dusty, Premixed Flame Propagation in Obstructed Passages with Tightly Placed Obstacles

Fluids ◽  
2020 ◽  
Vol 5 (3) ◽  
pp. 115
Author(s):  
Furkan Kodakoglu ◽  
Sinan Demir ◽  
Damir Valiev ◽  
V’yacheslav Akkerman
Keyword(s):  
Flame Propagation ◽  
Premixed Flame ◽  
Dust Particles ◽  
Blockage Ratio ◽  
Two Dimensional ◽  
Analytical Formulation ◽  
Flame Acceleration ◽  
Explosive Materials ◽  
Run Up ◽  
The Impact

A recent predictive scenario of premixed flame propagation in unobstructed passages is extended to account for obstructions that can be encountered in facilities dealing with explosive materials such as in coalmines. Specifically, the theory of globally-spherical, self-accelerating premixed expanding flames and that of flame acceleration in obstructed conduits are combined to form a new analytical formulation. The coalmining configuration is imitated by two-dimensional and cylindrical passages of high aspect ratio, with a comb-shaped array of tightly placed obstacles attached to the walls. It is assumed that the spacing between the obstacles is much less or, at least, does not exceed the obstacle height. The passage has one extreme open end such that a flame is ignited at a closed end and propagates to an exit. The key stages of the flame evolution such as the velocity of the flame front and the run-up distance are scrutinized for variety of the flame and mining parameters. Starting with gaseous methane-air and propane-air flames, the analysis is subsequently extended to gaseous-dusty environments. Specifically, the coal (combustible, i.e., facilitating the fire) and inert (such as sand, moderating the process) dust and their combinations are considered, and the impact of the size and concentration of the dust particles on flame acceleration is quantified. Overall, the influence of both the obstacles and the combustion instability on the fire scenario is substantial, and it gets stronger with the blockage ratio.

scholarly journals Investigation of Pressure Rise and Flame Acceleration Characteristics in a Single Channel of Wave Rotor Combustor with Spoilers

2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
Jianzhong Li ◽  
Kaichen Zhang ◽  
Wei Li ◽  
Li Yuan
Keyword(s):  
Flame Propagation ◽  
Single Channel ◽  
Pressure Rise ◽  
Propagation Speed ◽  
Blockage Ratio ◽  
Wave Rotor ◽  
Flame Acceleration ◽  
Channel Wave ◽  
Experimental Rig ◽  
Flame Propagation Speed

A simplified single channel wave rotor combustor (WRC) experimental rig was established, in which the spoilers with different blockage ratios (BR) could be conveniently installed and disassembled. The spoilers were firstly used for WRC to improve the pressure rise. The effects of different blockage ratios on the pressure rise and flame acceleration characteristics in a single channel of the WRC were investigated. The addition of spoilers could remarkably improve the pressure rise and flame propagation speed in a single channel of the WRC. While the blockage ratio of the spoiler increases, both pressure rise and mean flame propagation speed are improved. When the spoilers with a blockage ratio of 38.91% are used, the peak pressure increases by 200% compared to that of WRC without the spoilers. When the spoilers of different blockage ratios (23.35%, 31.13%, and 38.91%) are used, it is found that the flame propagation speed is significantly improved with the increasing of the blockage ratio. Specifically, the maximum flame propagation speed reaches 55 m/s, and the maximum mean flame propagation speed is 36.95 m/s. Furthermore, combustion becomes more intense, and the flame is brighter around the spoiler.

scholarly journals Experimental and Modeling Study of Wall Film Effect on Combustion Characteristics of Premixed Flame in a Constant Volume Combustion Bomb

2022 ◽  
Vol 7 ◽  
Author(s):  
Shijie Bai ◽  
Hongsheng Zhang ◽  
Chang Li ◽  
Chaohui Wu ◽  
Xingyu Liang ◽  
...  
Keyword(s):  
Flame Propagation ◽  
Internal Combustion Engines ◽  
Combustion Characteristics ◽  
Constant Volume ◽  
Premixed Flame ◽  
Wall Region ◽  
Wall Film ◽  
Soot Precursors ◽  
Constant Volume Combustion ◽  
The Impact

The primary objective of the present study was to investigate the impact of wall film on the combustion characteristics of premixed flames in internal combustion engines through the joint experimental and numerical techniques. The interaction between the premixed methane-air flame and n-dodecane film attached to the wall of a constant volume combustion bomb was experimentally examined. The flame propagation processes, as well as pressure evolution were quantitatively characterized. Then, computational fluid dynamic (CFD) simulation was performed incorporating the combustion chemistry model. To enable efficient simulation of the chemically reacting flow in engine chambers, a simplified modeling approach based on a two-step reaction scheme was developed. A compact reaction model for the selected model fuel n-dodecane was constructed and reduced to include 35 chemical species and 180 reactions. The flame propagation process of the premixed flame and its interaction with dry and wet walls was studied. The results showed that the propagation of the premixed flame could be divided into four stages, and the existence of the slit structure increased the instability of the flame structure in the near-wall region. The wall film tended to promote emissions, producing more unburned hydrocarbons, soot precursors and aldehydes.

scholarly journals Acceleration of Premixed Flames in Obstructed Pipes with Both Extremes Open

Energies ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 4094
Author(s):  
Abdulafeez Adebiyi ◽  
Olatunde Abidakun ◽  
V’yacheslav Akkerman
Keyword(s):  
Flame Propagation ◽  
Premixed Flame ◽  
Critical Parameters ◽  
Reacting Flow ◽  
Computational Simulations ◽  
Chemical Parameters ◽  
Flow Equations ◽  
Flame Acceleration ◽  
Logistic Regression Algorithm ◽  
Steady Propagation

Premixed flame propagation in obstructed channels with both extremes open is studied by means of computational simulations of the reacting flow equations with a fully-compressible hydrodynamics, transport properties (heat conduction, diffusion and viscosity) and an Arrhenius chemical kinetics. The aim of this paper is to distinguish and scrutinize various regimes of flame propagation in this configuration depending on the geometrical and thermal-chemical parameters. The parametric study includes various channel widths, blockage ratios, and thermal expansion ratios. It is found that the interplay of these three critical parameters determines a regime of flame propagation. Specifically, either a flame propagates quasi-steady, without acceleration, or it experiences three consecutive distinctive phases (quasi-steady propagation, acceleration and saturation). This study is mainly focused on the flame acceleration regime. The accelerating phase is exponential in nature, which correlates well with the theoretical prediction from the literature. The accelerating trend also qualitatively resembles that from semi-open channels, but acceleration is substantially weaker when both extremes are open. Likewise, the identified regime of quasi-steady propagation fits the regime of flame oscillations, found for the low Reynolds number flames. In addition, the machine learning logistic regression algorithm is employed to characterize and differentiate the parametric domains of accelerating and non-accelerating flames.

scholarly journals Computational Study of Premixed Flame Propagation in Micro-Channels with Nonslip Walls: Effect of Wall Temperature

Fluids ◽  
2021 ◽  
Vol 6 (1) ◽  
pp. 36
Author(s):  
Orlando J. Ugarte ◽  
V’yacheslav Akkerman
Keyword(s):  
Flame Propagation ◽  
Computational Study ◽  
Reacting Flow ◽  
Narrow Channels ◽  
Flow Equations ◽  
Flame Acceleration ◽  
Flame Dynamics ◽  
Micro Channels ◽  
Fuel Mixtures ◽  
The Impact

This investigation evaluates the propagation of premixed flames in narrow channels with isothermal walls. The study is based on the numerical solution of the set of fully-compressible, reacting flow equations that includes viscosity, diffusion, thermal conduction and Arrhenius chemical kinetics. Specifically, channels and pipes with one extreme open and one extreme closed are considered such that a flame is sparked at the closed extreme and propagates towards the open one. The isothermal channel walls are kept at multiple constant temperatures in the range from Tw=300 K to 1200 K. The impact of these isothermal walls on the flame dynamics is studied for multiple radii of the channel (R) and for various thermal expansion ratios (Θ), which approximate the thermal behavior of different fuel mixtures in the system. The flame dynamics in isothermal channels is also compared to that with adiabatic walls, which were previously found to produce exponential flame acceleration at the initial stage of the burning process. The results show that the heat losses at the walls prevent strong acceleration and lead to much slower flame propagation in isothermal channels as compared to adiabatic ones. Four distinctive regimes of premixed burning in isothermal channels have been identified in the Θ−Tw−R space: (i) flame extinction; (ii) linear flame acceleration; (iii) steady or near-steady flame propagation; and (iv) flame oscillations. The physical processes in each of these regimes are discussed, and the corresponding regime diagrams are presented.

scholarly journals Impact of Radiative Losses on Flame Acceleration and Deflagration to Detonation Transition of Lean Hydrogen-Air Mixtures in a Macro-Channel with Obstacles

Fluids ◽  
2018 ◽  
Vol 3 (4) ◽  
pp. 104 ◽  
Author(s):  
Gautham Krishnamoorthy ◽  
Lucky Mulenga
Keyword(s):  
Combustion Wave ◽  
Computational Cost ◽  
Scaling Analysis ◽  
Small Surface ◽  
Flame Acceleration ◽  
System Pressure ◽  
Micro Channels ◽  
Radiative Losses ◽  
Run Up ◽  
The Impact

While there has been some recognition regarding the impact of thermal boundary conditions (adiabatic versus isothermal) on premixed flame propagation mechanisms in micro-channels (hydraulic diameters <10 mm), their impact in macro-channels has often been overlooked due to small surface-area-to-volume ratios of the propagating combustion wave. Further, the impact of radiative losses has also been neglected due to its anticipated insignificance based on scaling analysis and the high computational cost associated with resolving it’s spatial, temporal, directional, and wavelength dependencies. However, when channel conditions promote flame acceleration and deflagration-to-detonation transitions (DDT), large pressures are encountered in the vicinity of the combustion wave, thereby increasing the magnitude of radiative losses which in turn can impact the strength and velocity of the combustion wave. This is demonstrated for the first time through simulations of lean (equivalence ratio: 0.5) hydrogen-air mixtures in a macro-channel (hydraulic diameter: 174 mm) with obstacles (Blockage ratio: 0.51). By employing Planck mean absorption coefficients in conjunction with the P-1 radiation model, radiative losses are shown to affect the run-up distances to DDT in a long channel (length: 11.878 m). As anticipated, the differences in run-up distances resulting from radiative losses only increased with system pressure.

A simplified numerical and analytical study for assessing the seismic response of a gravity concrete lock

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Neander Berto Mendes ◽  
Lineu José Pedroso ◽  
Paulo Marcelo Vieira Ribeiro
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Analytical Study ◽  
Two Dimensional ◽  
The Finite Element Method ◽  
Fluid Structure ◽  
Analytical Formulation ◽  
Acoustic Cavity ◽  
Water Chamber ◽  
Structure Problem

ABSTRACT: This work presents the dynamic response of a lock subjected to the horizontal S0E component of the El Centro earthquake for empty and completely filled water chamber cases, by coupled fluid-structure analysis. Initially, the lock was studied by approximation, considering it similar to the case of a double piston coupled to a two-dimensional acoustic cavity (tank), representing a simplified analytical model of the fluid-structure problem. This analytical formulation can be compared with numerical results, in order to qualify the responses of the ultimate problem to be investigated. In all the analyses performed, modeling and numerical simulations were done using the finite element method (FEM), supported by the commercial software ANSYS.

Recent Advances and Need of Green Synthesis in Two-Dimensional Materials for Energy Conversion and Storage Applications

2021 ◽  
Vol 16 ◽  
Author(s):  
Joice Sophia Ponraj ◽  
Muniraj Vignesh Narayanan ◽  
Ranjith Kumar Dharman ◽  
Valanarasu Santiyagu ◽  
Ramalingam Gopal ◽  
...  
Keyword(s):  
Energy Storage ◽  
Green Synthesis ◽  
2D Materials ◽  
Synthesis Method ◽  
Energy Storage And Conversion ◽  
Two Dimensional ◽  
Severe Problem ◽  
Energy Conversion And Storage ◽  
Energy Application ◽  
The Impact

: Increasing energy crisis across the globe requires immediate solutions. Two-dimensional (2D) materials are in great significance because of its application in energy storage and conversion devices but the production process significantly impacts the environment thereby posing a severe problem in the field of pollution control. Green synthesis method provides an eminent way of reduction in pollutants. This article reviews the importance of green synthesis in the energy application sector. The focus of 2D materials like graphene, MoS2, VS2 in energy storage and conversion devices are emphasized based on supporting recent reports. The emerging Li-ion batteries are widely reviewed along with their promising alternatives like Zn, Na, Mg batteries and are featured in detail. The impact of green methods in the energy application field are outlined. Moreover, future outlook in the energy sector is envisioned by proposing an increase in 2D elemental materials research.

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