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Abstract
A technique for evaluation of shock wave impulse after a methane-air mixture explosion is elaborated. The numerical model developed in previous studies has been verified in the laboratory by using laser initiation of explosives and measuring the pressure impulses of explosion products on a ballistic pendulum. To evaluate the mechanical impulse the functional correlations between its magnitude, the swing angle, and the pendulum characteristics have been derived analytically. The reliability of experimental results is ensured by calibrating the sensor that measures the pendulum swing angle and estimating the impulse measurement errors caused by specifics of angle measurements by a digital voltmeter, pendulum axis friction, and the pauses between measurements. Testing the developed technique to evaluate the shock wave impact showed satisfactory consistency of experimental and theoretical results with the momentum deviation below 9%, which confirms model applicability and correct reproducibility of the shock wave propagation process.
Highlights
The explosion of a methane-air mixture in an underground coal mine excavation is considered as one of the most dangerous catastrophic events in mining [1, 2]
The pressure impulse was measured using the method of ballistic pendulum due to its reliability, measurement accuracy and ease of implementation (Fig. 1), with the impulse being calculated based on the swing angle
Regarding to the short-term period of the explosion product impacts on the pendulum, we can assume that the pendulum gains an impulse when the swing angle φ equals to zero
Summary
The explosion of a methane-air mixture in an underground coal mine excavation is considered as one of the most dangerous catastrophic events in mining [1, 2]. The specifics of methane-air and/or dust-air mixture explosions consist in generation of shock waves and their propagation through the mine excavation network [3 – 6]. The shock wave (SW) is believed to be the main factor threatening the life and health of miners, leading to excavation collapses and damage of mining equipment operated underground. Many experts suggested the ambiguous nature of the source that initiates the ignition and explosion of the methane-air mixture [7, 8]. The changes in technologies, equipment operation mode, the physicochemical properties of coal being destructed due to nanostructure stability violation, etc. Recent studies using numerical modelling demonstrated notable achievements [14 – 16]; the proposed ideas and obtained results will be taken into account in this study
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