Numerical determination of velocity field of airflow in gob

Author: J. Szlązak

In most Polish coal mines the extraction process is conducted by means of caving and a characteristic feature of excavated seams is a high risk of fire.

The intensity of ventilation in the gob of a long-wall system with caving is the main influence on the level of risk of such a fire hazard.

The reasons for such spontaneous fires are: firstly of all, coal losses in the gob or coal from external sources - secondly the quantity of air supplied by the main fans and permeating that gob.

This article presents a mathematical model for the airflow in the caving zone in the context of a changeable co-efficient of gob permeability.

A numerical method for solving equations describing airflow, which enables the creation of a computer programme for the determination of velocity and pressure in the caving zone, is also given. Such programmes have been designed for the most typical ventilation systems.

The calculations of the distribution of air velocity and pressure may be of some help when selecting preventive measures to reduce fire risks.