An introduction to heat transfer

Proceedings of the royal society.

Influence of Coal Dust on Premixed Turbulent Methane-Air Flames

Deflagration explosions of coal dust clouds and flammable gases are a major safety concern in coal mining industry. Accidental fire and explosion caused by coal dust cloud can impose substantial losses and damages to people and properties in underground coal mines. Hybrid mixtures of methane and coal dust have the potential to reduce the minimum activation energy of a combustion reaction. In this study the Minimum Explosion Concentration (MEC), Over Pressure Rise (OPR), deflagration index for gas and dust hybrid mixtures (K st ) and explosive region of hybrid fuel mixtures present in Ventilation Air Methane (VAM) were investigated. Experiments were carried out according to the ASTM E1226-12 guideline utilising a 20 L spherical shape apparatus specifically designed for this purpose. Results obtained from this study have shown that the presence of methane significantly affects explosion characteristics of coal dust clouds. Dilute concentrations of methane, 0.75–1.25%, resulted in coal dust clouds OPR increasing from 0.3 bar to 2.2 bar and boosting the K st value from 10 bar m s −1 to 25 bar m s −1 . The explosion characteristics were also affected by the ignitors’ energy; for instance, for a coal dust cloud concentration of 50 g m −3 the OPR recorded was 0.09 bar when a 1 kJ chemical ignitor was used, while, 0.75 bar (OPR) was recorded when a 10 kJ chemical ignitor was used. For the first time, new explosion regions were identified for diluted methane-coal dust cloud mixtures when using 1, 5 and 10 kJ ignitors. Finally, the Le-Chatelier mixing rule was modified to predict the lower explosion limit of methane-coal dust cloud hybrid mixtures considering the energy of the ignitors.

Effects of ignition energy on fire and explosion characteristics of dilute hybrid fuel in ventilation air methane

Upward flame spread over discrete fuels

https://digital.wpi.edu/downloads/np193935v

Study of Interaction of Entrained Coal Dust Particles in Lean Methane-Air Premixed Flames

Vertical arrays of horizontally protruding wood matchsticks, 0.25 cm in diameter and 1.91 cm long, arranged from one to five matches across were used to investigate the influence of the spacing of discrete fuel elements on rates of upward flame spread. Vertical spacing's between the matchsticks in the array (0.0, 0.6, 0.8, 1.0, 1.2, and 1.4 cm) were used to reveal the influence of separation distance on rates of upward flame spread, defined as progression of the ignition front, time to burnout, and mass-loss rates. Advancement of the ignition front was found to vary linearly with time for the 0.0 cm spacing, while reaching nearly a t1.7 advancement with time for the furthest-spaced arrays. Rates of upward flame spread were found to increase dramatically for spacings between 0 cm and 0.8 cm and experienced only a slight increase thereafter. Based on these observations, the influence of convective heating was hypothesized to dominate this spread mechanism, and predictions of ignition times were developed us...

Yanxuan Xie

Papers

Study of Interaction of Entrained Coal Dust Particles in Lean Methane-Air Premixed Flames

Burning Behavior of Vertical Matchstick Arrays

Naturally entraining solid particle injector