Numerical Analysis of Gas Explosions in Coal Mines
Abstract
We use reactive CFD simulations to study worst-case scenarios for gas explosions in stoichiometric methane-air mixtures confined in largescale obstructed tunnel geometries relevant to coal mines. In particular, we analyze effects of tunnel blockage ratio br and spacing of obstructions L on flame acceleration, formation of a shock-flame complex, deflagration-to-detonation transition (DDT), and resulting explosion pressures. We considered two types of obstructions: periodic obstacles placed on channel walls, and a layer of rock rubble that partially fills the channel. For channels with periodic obstacles and the channel height d = 3 m typical of coal mine tunnels, the minimum distance to DDT, LDDT = 28 m, is observed for br = 0.3, L/d = 0.5. For channels with rock rubble and d = 3 m, the minimum LDDT = 5 5.5 m is observed when the channel is completely filled with rocks. This DDT length is significantly shorter than the values computed for channels with periodic obstacles, but it corresponds to a relatively loose rock layer that may not be typical for realistic coal mine environments. Nevertheless, our results show that methane-air detonations in coal mines can develop quickly and produce reflected-shock pressures ~ 50 atm (735 psi). These detonations cannot be contained by the standard 50 psi or 120 psi seals that are designed to stop relatively slow deflagrations. In areas with a high risk of detonations, the seals should be designed to withstand the static pressure of at least 640 psi, as previously recommended by NIOSH.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 02, 2021
- Accession Number
- AD1124036
Entities
People
- Carolyn R. Kaplan
- Elaine Oran
- Logan Kunka
- Vadim N. Gamezo
Organizations
- Alpha Foundation
- Texas A&M University
- University of Maryland