Jerzy Krawczyk

The mining in seams with a high methane content by means of a longwall system, under conditions of high extraction concentration, results in exceeding methane concentrations allowed by the regulations at workings of the longwall environment, with the effect of mining machines’ standstill periods. The paper is a part of a study supporting the develo...

The analysis of phenomena related to gas transport in hard coal is important with regard to the energetic use of coal bed methane (CBM), the reduction of greenhouse gas emissions to the atmosphere (CO2) and the prevention of natural hazards such as methane hazards and gas and rock outbursts. This article presents issues concerning the feasibility a...

Research work on the air flow in mine workings frequently utilises computer techniques in the form of numeric simulations. However, it is very often necessary to apply simplifications when building a geometrical model. The assumption of constant model geometry on its entire length is one of the most frequent simplifications. This results in a subst...

This paper presents a relatively simple method to analyze potential methane hazard and preventive methods based on a computer simulation of the airflow and methane emission on the longwall face and in the goaf. The presented approach considers the operation of a longwall shearer and conveyers and their possible impacts on both direct emissions of m...

Underground coal mining frequently uses longwalls. The occurrence of a potentially explosive mixture of methane and air is one of the most serious hazards. A large number of papers have applied numerical modeling of methane propagation in research aimed at this problem. To date, none of the CFD simulations has considered the movement of the shearer...

Wiele ścian wydobywczych jest eksploatowanych w warunkach zagrożenia metanowego. Istotnym źródłem gazów są pustki poeksploatacyjne. Z tego względu ważne jest poznanie mechanizmu wymiany gazów na granicy ściany wydobywczej i przyległych zrobów. Dotychczasowe pomiary in situ nie dostarczały wystarczającej informacji w tej dziedzinie. Niniejsza praca...

For many years, the legal regulations governing radiation protection were primarily concerned with artificial radioactivity, omitting in practice the hazards associated with the occurrence of natural radioactivity in non-nuclear industry. Meanwhile, materials with enhanced concentration of natural isotopes can pose serious radiation risks. A specta...

Currently CFD numerical simulations are an important part of the research on the airflow in mining drift. One of the first steps throughout the simulation process is to build a geometric model that will reflect the geometry in which the problem is being investigated. In the case of numerical calculations for underground mine workings, due to the ve...

Abandonment of underground mines of a complex multi-level structure is usually done in a stepwise way. At each stage, the performance of the ventilation system must be adjusted to current structure of workings and the liquidation of related activities. The ventilation system must not only provide relevant working conditions of the liquidation but a...

This paper presents a new stationary device that can perform simultaneous measurements of air flow velocity and methane concentration in a mine heading (stationary methane anemometer). The test station is designed to use the instrument to test the effect of various parameters on the air-methane stream. The air velocities and methane concentrations...

The paper presents results of a research on the migration of methane from goaf into an area of a longwall ventilated by means of the U-type ventilation system. Two-dimensional models of the area in question were prepared. The models encompassed longwalls whose length was 240 m, as well as segments of the main and tailgate whose length was minimum 5...

Present paper is an analysis of the propagation of methane in the end segment of a longwall ventilated by means of the Y-type ventilation system. The propagation in question occurs as a result of sudden inflows of methane from the adjacent goaf. Relevant simulations for multiple variants were carried out using the Finite Volume Method. As part of t...

In this study, presented are the advanced hot-wire anemometric measurements systems suitable for investigation of velocity fields in mine headings. A construction of two types of modernized three-element hot-wire anemometric probes is discussed. The three-element wire sensor which was used only under laboratory conditions up to date was added a fou...

In this study, presented are the advanced hot-wire anemometric measurements systems suitable for investigation of velocity fields in mine headings. A construction of two types of modernized three-element hot-wire anemometric probes is discussed. The three-element wire sensor which was used only under laboratory conditions up to date was added a fou...

This article outlines the results of a computer simulation reproducing the transport of a mixture of air and methane following the outburst on 25 November, 2005 in transport gallery D-6, bed 409/4, at the 'Zofiówka' hard coal mine. Based on a mathematical model, numerical method and boundary conditions from the disturbance caused by the outburst, t...

A method of a continuous measurement of an unsteady distribution of velocity in a cross section of a mine working has been presented. The measurement was made with a computer controlled portable data acquisition system with a fast 24-channel data logger capable of simultaneous sampling in all channels and in-home designed and manufactured Pitot-Pra...

The paper presents a method for distinguishing unstable operating points in ventilation networks with fans operating in parallel. Several concepts of ventilation systems and their characteristics were applied. The analysis of local stability of equilibrium points of the system of ordinary differential equations describing unsteady incompressible fl...

The present article sets forward the results of field tests that made it possible to validate the mathematical model used in the VENTGRAPH ventilation engineer programmes. The case considered relates to the introduction of a new heading to the ventilation network of the mine. The utilisation of computer programmes in practice is justified by the ne...