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2486 KiB

Open AccessArticle

Scale Effect of Premixed Methane-Air Combustion in Confined Space Using LES Model

by Liang Wang, Sisi Que, Jerry C. Tien and Nassib S. Aouad

Minerals 2016, 6(1), 2; https://doi.org/10.3390/min6010002 - 29 Dec 2015

Cited by 2 | Viewed by 4598

Abstract

Gas explosion is the most hazardous incident occurring in underground airways. Computational Fluid Dynamics (CFD) techniques are sophisticated in simulating explosions in confined spaces; specifically, when testing large-scale gaseous explosions, such as methane explosions in underground mines. The dimensions of a confined space where explosions could occur vary significantly. Thus, the scale effect on explosion parameters is worth investigating. In this paper, the impact of scaling on explosion overpressures is investigated by employing two scaling factors: The Gas-fill Length Scaling Factor (FLSF) and the Hydraulic Diameter Scaling Factor (HDSF). The combinations of eight FLSFs and five HDSFs will cover a wide range of space dimensions where flammable gas could accumulate. Experiments were also conducted to evaluate the selected numerical models. The Large Eddy Simulation turbulence model was selected because it shows accuracy compared to the widely used Reynolds’ averaged models for the scenarios investigated in the experiments. Three major conclusions can be drawn: (1) The overpressure increases with both FLSF and HDSF within the deflagration regime; (2) In an explosion duct with a length to diameter ratio greater than 54, detonation is more likely to be triggered for a stoichiometric methane/air mixture; (3) Overpressure increases as an increment hydraulic diameter of a geometry within deflagration regime. A relative error of 7% is found when predicting blast peak overpressure for the base case compared to the experiment; a good agreement for the wave arrival time is also achieved. Full article

(This article belongs to the Special Issue Advanced Underground Mine Ventilation and Monitoring Systems)

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6898 KiB

Open AccessArticle

Temporal and Spatial Distribution of Respirable Dust After Blasting of Coal Roadway Driving Faces: A Case Study

by Shengyong Hu, Zhuo Wang and Guorui Feng

Minerals 2015, 5(4), 679-692; https://doi.org/10.3390/min5040517 - 15 Oct 2015

Cited by 33 | Viewed by 4203

Abstract

Coal roadway driving is an important part of the underground mining system, and very common in Chinese coal mines. However, the high concentration of respirable dust produced in the blasting operation poses a great hazard to miners’ health as well as the underground environment. In this paper, based on the direct simulation Monte Carlo method, the gas–solid two-phase flow model of particle movement is established to study the respirable dust distribution in blasting driving face. The results show that there is an obvious vortex region in which airflow velocity is lower than that close to the roadway wall and driving face. After blasting, respirable dust in the front of the dust group jet from the driving face cannot be discharged timely, with the result that its concentration is higher than the critical value until it is expelled from the roadway, whereas respirable dust concentration at the back of the dust group is gradually diluted and exhibits an alternate thin dense phase distribution. Meanwhile, respirable dust concentration in the breathing zone is relatively higher than that at the top and bottom of roadway. The accuracy of numerical simulation results is verified by field measurements. The research results are helpful for further understanding the evolution of respirable dust distribution after blasting, and are good for providing guidance for efficient controlling of respirable dust and improving the working environment for underground miners. Full article

(This article belongs to the Special Issue Advanced Underground Mine Ventilation and Monitoring Systems)

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1614 KiB

Open AccessArticle

An Underground Air-Route Temperature Prediction Model for Ultra-Deep Coal Mines

by Shuai Zhu, Shiyue Wu, Jianwei Cheng, Siyuan Li and Mingming Li

Minerals 2015, 5(3), 527-545; https://doi.org/10.3390/min5030508 - 25 Aug 2015

Cited by 23 | Viewed by 8252

Abstract

Due to modern mining methods deployed in recent years, production of coal mines has been expanded significantly compared to thirty years ago. As a consequence, the mining depth of coal mines is becoming ever deeper. A common world-wide problem that underground coal mines are currently experiencing is the hazard caused by the underground hot environment, which also promotes a great need of reliable mitigation measures to assist mine operators controlling the heat stress for miners as well as maintaining the normal operation of the mine. In this paper, a model for underground air-route temperature prediction in ultra-deep mines based on previous findings was developed. In developing this model, the idea of heat balance was used to establish the temperature calculation equation. Various underground heat sources (air compress, wall oxidation, underground heat, machinery, etc.) are covered in the model to improve the prediction accuracy. In addition, a PC-based numerical tool was also developed to aid users using such a mathematical model. Finally, a few temperature measurements for an ultra-deep underground coal mine were performed to demonstrate the applicability of the proposed mathematical prediction model. Full article

(This article belongs to the Special Issue Advanced Underground Mine Ventilation and Monitoring Systems)

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