Spherical flame propagation Behaviors in Iron-Methane-Air mixtures

Effects of a carbon monoxide-dominant gas mixture on the explosion and flame propagation behaviors of methane in air

Experimental and numerical study on formation mechanism of premixed hydrogen-air squish flame in wall constrained environment

It studied the explosion propagation of the hybrid mixture of LDPE dust and a small amount of ethylene (below its LEL) in a closed duct, to examine the impacts of dust concentration, dust particle size, and ethylene concentration on flame propagation behavior and overpressure characteristics. The dust concentration affected the explosion behavior of the LDPE dust/ethylene hybrid mixture in two ways. The flame gradually became discrete and unstable as the dust concentration increased, while the maximum and average flame propagation velocity, Pmax, and (dp/dt)max increased first and then decreased. The dust particle size and ethylene concentration had a significant effect on the hybrid mixture explosion. As the particle size decreased or the ethylene concentration increased, the discrete flames quickly merged into a bright continuous flame. Further, the maximum and average flame propagation velocity, Pmax, and (dp/dt)max increased, whereas the fluctuation degree of the flame propagation velocity with time showed a decreasing trend. There was no obvious agglomeration phenomenon among small LDPE particles. The explosion overpressure and flame propagation showed a strong synergistic effect. Compared with the semi-open duct, the closed duct with a more uniform dust/gas hybrid mixture showed a more continuous flame structure, a shorter flame propagation distance, and a lower flame propagation velocity. These conclusions can provide a scientific basis for explosion risk analyses and process safety designs involving the production of LDPE powder.

Optical diagnostics in impact of ammonia energy ratio and diesel split ratio on combustion process and flame propagation in an Ammonia-Diesel Dual-Fuel engine

Effects of radiative loss on premixed planar flame propagation

Application of modified eddy dissipation concept with large eddy simulation for numerical investigation of internal combustion engines

Experimental analysis on post-explosion residues for evaluating coal dust explosion severity and flame propagation behaviors

Response of flame thickness and propagation speed under intense turbulence in spatially developing lean premixed methane–air jet flames

With the advancement of spark ignition engines, lean or diluted in-cylinder charge is often used to improve the engine performance. Enhanced in-cylinder charge motion is widely applied under such conditions to promote the flame propagation, which raise challenges for the spark ignition system. In this work, the spark discharging process is investigated under different flow conditions via both optical diagnosis and electrical measurement. Results show that the spark plasma channel is stretched under flow conditions. A higher discharge current can maintain the stretched spark plasma for a longer duration. Re-strikes are observed when the spark plasma is stretched to a certain extent. The frequency of re-strikes increases with increased flow velocity and decreased discharge current level. The discharge duration reduces with the increased flow velocity. The effects of gas flow on the ignition and flame kernel development are studied in a constant volume optical combustion chamber with premixed lean and stoichiometric methane air mixture. Two spark strategies with low and high discharge current are used for the ignition. The flame propagation speed of both lean and stoichiometric mixtures increases with the increased gas flow velocity. A higher discharge current level retains a more stable spark channel and improves the flame kernel development for both lean and stoichiometric conditions, especially under the higher gas flow velocity of 20 m/s.

The work of this thesis aims at studying the explosive phenomenon of hybrid mixtures to get insights into the driving mechanisms and the explosion features affecting the course of hybrid mixture explosion. This is achieved by means of an extensive experimental study that developed in the following steps: - Measurement of the ignitability and the explosion severity; - Study of the flame propagation. The explosion experiments were performed in a 20 l Siwek bomb; instead, the flame propagation experiments were performed in a new equipment: a tube of 1 m length and 7x7 cm square. The hybrid mixture under examination was a mixture of methane and nicotinic acid in air. Results allow the definition of four different regimes of the gas/dust/air mixture explosion in the plane dust concentration vs. fuel concentration. And the flame propagation behaviour of the mixture gives a further contribution to the explanation of the different regimes.

In order to systematically study the suppression effect of Aluminum hydroxide[Al(OH)3] and Magnesium hydroxide[Mg(OH)2] on the explosion of flour, Hartmann experiment system was used to carry out the explosion flame propagation experiment, and the influence of adding different proportions of Al(OH)3 and Mg(OH)2 powder on the morphology and propagation speed of flour combustion flame was studied. Combined with the thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) curves of Al(OH)3 and Mg(OH)2 powder, the inhibition mechanism of Al(OH)3 and Mg(OH)2 powder on flour explosion was analyzed. The results showed that with the increase of Al(OH)3 and Mg(OH)2, the flame propagation speed gradually decreases. After adding 40%wt Mg(OH)2, when t = 182 ms, the flame reaches the top of the glass tube. When 60 wt% Mg(OH)2 and 60 wt% Al(OH)3 powder were added, the maximum flame propagation velocity of flour decreased from 13.86 m/s to 5.78 m/s and 1.62 m/s, respectively, and Al(OH)3 was superior to Mg(OH)2 in inhibiting flame propagation. Both inhibitors can inhibit flour combustion by adsorption of H and OH radicals.

A numerical analysis of multi-dimensional iron flame propagation using boundary-layer resolved simulations

Investigation of the structure and propagation speeds of n-heptane cool flames

Experimental observations of turbulent flame propagation effected by flame acceleration in the end gas of closed combustion chamber

This study investigates the suppression effect of ultrafine CaCO3 powder on gas explosions through a series of experiments conducted in a medium-scale explosion tube (9.6 m in length) with varying concentrations of ultrafine CaCO3. The gas explosion suppression concentration was established at 9.5%. The results indicate that, at concentrations of 125 g/m3 and 300 g/m3, ultrafine CaCO3 powder significantly reduced the flame propagation speed of the gas explosion. Among the concentrations that did not fully suppress the gas explosion, 20 g/m3 effectively mitigated the flame propagation speed and overpressure throughout the entire process. The concentration of 75 g/m3 demonstrated a suppression–promotion–suppression–promotion pattern regarding the flame propagation rate, with significant fluctuations observed throughout the process. While the maximum suppression rate reached 60.9%, the maximum promotion rate was 131.12%. At 10 g/m3, the flame propagation rate initially increased before decreasing, with the most effective suppression observed within the first 6.6 m, where flame propagation suppression increased rapidly from 58.13% to 74.82%, and the peak explosion overpressure was reduced by up to 62.94%. These findings contribute valuable insights for the development of effective gas explosion suppression strategies in mining environments.