Abstract
This paper presents a method for determining the sensitivity of the main air flow directions in ventilation subnetworks to changes in aerodynamic resistance and air density in mine workings. The authors have developed formulae for determining the sensitivity of the main subnetwork air flows by establishing the degree of dependency of the air volume stream in a given working on the variations in resistance or air density of other workings of the network. They have been implemented in the Ventgraph mine ventilation network simulator. This software, widely used in Polish collieries, provides an extended possibility to predict the process of ventilation, air distribution and, in the case of underground fire, the spread of combustion gasses. The new method facilitates an assessment by mine ventilation services of the stability of ventilation systems in exploitation areas and determines the sensitivity of the main subnetwork air flow directions to changes in aerodynamic resistance and air density. Recently in some Polish collieries new longwalls are developed in seams located deeper than the bottom of the intake shaft. Such a solution is called “exploitation below the level of access” or “sublevel”. The new approach may be applied to such developments to assess the potential of changes in direction and air flow rates. In addition, an interpretation of the developed sensitivity indicator is presented. While analyzing air distributions for sublevel exploitation, the application of current numerical models for calculations of the distribution results in tangible benefits, such as the evaluation of the safety or risk levels for such exploitation. Application of the Ventgraph computer program, and particularly the module POŻAR (fire) with the newly developed options, allows for an additional approach to the sensitivity indicator in evaluating air flow safety levels for the risks present during exploitation below the level of the intake shaft. The analyses performed and examples presented enabled useful conclusions for mining practice to be drawn.
Highlights
Ventilation systems of mines are often too complex to predict and control the flow without numerical modeling
Examples are presented to illustrate the performance of the new calculation capacities of the Ventgraph program. The results prove their usefulness for analyzing the changes of air flow direction and distribution in a ventilation system of an underground mine
The solution of a ventilation network for two air density values ρj enables a calculation of the density sensitivity indicator [κ i,j ] for all network branches in column j of the sensitivity factor matrices with dimensions J × J, where J is the number of branches in the ventilation network
Summary
Ventilation systems of mines are often too complex to predict and control the flow without numerical modeling. A useful addition to the evaluation of air flow stability is a determination of the indices of the sensitivity of the main flows in ventilation subnetworks to the changes in the aerodynamic resistance of workings [13,14,15]. This parameter shows the degree of dependency of the air volume stream in a given working to the resistance of other workings forming the network. The results of the calculations are presented in an isometric diagram of a specific ventilation network
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
