Kenichi Uchino

Fundamental studies on locating spontaneous combustion of coal by the self-potential method

Abstract Self-potential anomalies can be generated by a fluid pressure gradient, by a temperature gradient or by a chemical gradient. On the basis of this principle, the authors propose a self-potential method to locate the fire source of spontaneous combustion of coal, and have performed experiments using models to examine the possibility of this method. The experiments are divided into two groups. The first is to investigate the influence of the heater temperature on potential distribution; the other is to investigate the influence of the heating time. The results of these experiments have shown that the potentials generated by the heat are of measurable magnitude and they become larger with increasing heating time and/or heater power. Moreover, the results of all the experiments have a common feature, namely a potential distribution is always generated corresponding to the conditions of a heat source and there is a centre of potential distribution above the heat source. It is concluded that it is possible, at least at the experimental scale, to locate the heat source by the self-potential method.

A Full-scale Experiment on Water Spray Zones for Suppression of Underground Open Fires.

In order to prove the practical effect of a water spray zone on suppression of the spread of underground fire, a full-scale experiment was performed in a 400 m long test gallery with a cross section of 5.4 m2.Firstly, it is clarified that a water spray method is effective when water droplets are uniformly sprayed in the gallery and the mean diameter is less than 0.4 mm. Secondly, the cooling effect of water spray is quantitatively discussed from many aspects such as heat transfer and ventilation. Finally, it is shown that the quantity of water required to suppress the spread of fire is proportional to the air velocity and the cross section of gallery and that for a strongest fire can be estimated by equation (5) in the paper.

Behavior of open fire in inclined galleries and the change in ventilation characteristics caused by the fire.

In order to acquire fundamental data on the characteristics of open fires in inclined galleries and the change in ventilation characteristics caused by the fire, a series of experiments have been carried out, using two types of model gallery.The results of the investigation are summarized as follows;(1) The effect of the inclination of the gallery on the spread rate of the timber fire was quantitatively clarified in both cases of upward and downward spread of the fire.(2) Buoyancy effects created by the fire in a inclined gallery contributes to reducing the pressure loss of ventilation in case of ascensional ventilation and to increasing it in case of descensional ventilation.(3) A method is proposed for estimating the fire spread rate and the fire zone length, the variation of ventilation cased by fire and the effect of the inclination of the gallery being taken into consideration.