Computer Simulation of Flow of Air and Methane Mixture in the Longwall – Return Crossing Zone

 Author: Marian Branny

This paper investigates how the positions of jet fans, installed at the outlet from the longwall region, should affect the efficiency of methane rarefaction and removal from the area. The adequacy of the suggested
solution is verified by numerical simulations supported by the programme FLUENT 6.1.
The flow region comprising two crossing headings (longwall end section with the return airway) is shown in Fig. 1. Methane inflow from the rock strata is modelled by assuming the appropriate boundary condition on one of the walls restricting the flow region. The potentials to reduce methane hazards by the use of free jet fans are explored. The fan WLE-603B is installed in the inlet cross-section of the niche (x = 5 m), in three positions:
a) half-way the section width, 0.5 m from the roof
b) in the upper corner of the inlet cross-section
c) in the lower corner of the inlet cross-section
and
d) underneath the roof, at the distance x = 4 m from the niche front
e) underneath the roof, at the distance x = 6 m from the niche front
Fig. 5-6 and 7-8 show velocity fields and distributions of mass fractions of methane at selected cross-sections. The most favourable variants are those designated as b (Fig. 5, 7) and c and e, where the fan is positioned in the upper or lower corner of the inlet cross-section or when it is pushed into the through-flow stream.

Registered differences between these solutions are minor and prove to be negligible in practical applications.