Ventilation Network Research Articles

Models and methods of aerogasdynamic calculations for ventilation networks in underground mines: Review

Models and methods of aerogasdynamic calculations for ventilation networks in underground mines: Review

Учет локальной естественной тяги при обеспечении аэрологической безопасности на горных предприятиях

Safety of mining operations is the basis for the efficient functioning of the mines. During mining operations, due to changing conditions in the mine workings, the natural draft began to appear more frequent. Moreover, its influence can be limited to a separate section without affecting the entire ventilation network. In this paper, the new concept is introduced and explained — local natural ventilation. The classification signs and the negative consequences of its manifestation are presented. Main difference between the local natural ventilation as a subspecies of natural ventilation as a whole lies in the limited action both in the spaces of mine workings or individual sections, and in time. Particularly its occurrence depends on the season or the technological processes performed. In this case, the local natural ventilation is not an emergency and is not subject to registration as an incident or accident. However, its manifestations can lead to both incidents and accidents. Taking this factor into account will allow to increase the level of aerological safety at the mining enterprises. A method of three-dimensional computer modeling is proposed for predicting the manifestation of local natural ventilation and making decisions to prevent it. An example of the use of this approach at the Norilsk mine during the construction of shafts with verification of field measurements is given. It confirms the possibility of practical application of the proposed calculation method. The algorithm for registering the local natural ventilation considered in the article makes it possible to develop activities for improving the level of industrial safety at the mining enterprises as a whole.

ОБ ИСПОЛЬЗОВАНИИ АППАРАТА НЕЧЁТКОЙ ЛОГИКИ ДЛЯ ПОВЫШЕНИЯ АДЕКВАТНОСТИ МОДЕЛЕЙ ШАХТНЫХ ВЕНТИЛЯЦИОННЫХ СЕТЕЙ ПРИ РЕШЕНИИ ЗАДАЧ ИНЖЕНЕРНОГО ОБЕСПЕЧЕНИЯ АВАРИЙНО-СПАСАТЕЛЬНЫХ РАБОТ

In this paper the possibility of using fuzzy logic approach in the predicting of param-eters of mine ventilation network model in engineering support task solving during mine res-cue operators is described. The structure and elemental composition of predicting system of parameters of mine ventilation network is offered. Estimation of discrete factors influence on parameters of the mine ventilation network changing is carried out. Regression model for di-rect using without fuzzy logic systems implementation environment is released.

局部搜索微分进化算法求解复杂通风网络优化策略研究

局部搜索微分进化算法求解复杂通风网络优化策略研究

A study on source identification of gas explosion in coal mines based on gas concentration

When the gas explosion occurs in the mine, it is essential to determine in time whether the ventilation system is damaged and trace the explosion location and time to develop an emergency rescue plan and conduct rescue work. In this study, a method to trace the source of explosion by monitoring catastrophic gas concentrations, based on the one-dimensional unsteady flow differential equation, an unsteady flow model for the transport of catastrophic gas in the ventilation network was established. Further, the change laws of catastrophic gas concentrations at roadway intersections were analyzed in combination with the nodal air volume balance law in the ventilation network theory. Finally, we used the particle swarm optimization (PSO) algorithm to invert the gas explosion source point and time in conjunction with the catastrophic gas concentration monitoring data at the monitoring point. Herein, an instantaneous release tracer gas was used instead of a catastrophic gas after a gas explosion, and a concentration monitoring experiment was carried out in a full-size experimental roadway. The inversion results show that the PSO can invert the location and time of the explosion source and simultaneously assess the damage status of dampers within the ventilation network. Note that the root mean square error between the inversion and measured results was less than 1, proving the reliability of the inversion results.

Optimization of mine ventilation network feature graph.

A ventilation network feature graph can directly and quantitatively represent the features of a ventilation network. To ensure the stability of airflow in a mine and improve ventilation system analysis, we propose a new algorithm to draw ventilation network feature graphs. The independent path method serves as the algorithm's main frame, and an improved adaptive genetic algorithm is embedded so that the graph may be drawn better. A mathematical model based on the node adjacency matrix method for unidirectional circuit discrimination is constructed as the drawing algorithm may not be valid in such cases. By modifying the edge-seeking strategy, the improved depth-first search algorithm can be used to determine all of the paths in the ventilation network with unidirectional circuits, and the equivalent transformation method of network topology relations is used to draw the ventilation network feature graph. Through the analysis of the topological relation of a ventilation network, a simplified mathematical model is constructed, and network simplification technology makes the drawing concise and hierarchical. The rapid and intuitive drawing of the ventilation network feature graphs is significant for optimization of the ventilation system and day-to-day management.

An Efficient Mine Ventilation Solution Method Based on Minimum Independent Closed Loops

In this paper, according to the analysis of optimum circuits, we present an efficient ventilation network solution based on minimum independent closed loops. Our main contribution is optimizing the circuit dividing strategy to improve the iteration convergence and the efficiency of a single iteration. In contrast to a traditional circuit, a minimum closed loop may contain one or more co-tree branches but fewer high-resistance branches and fan branches. It is helpful in solving the problem of divergence or slow convergence for complex ventilation networks. Moreover, we analyze the dividing rules of closed loops and improve the dividing algorithm of minimum independent closed loops. Compared with the traditional Hardy Cross iteration method, the improved solution method has better iteration convergence and computation efficiency. The experimental results of real-world mine ventilation networks show that the improved solution method converges rapidly within a small number of iterations. We also investigate the influence of network complexity, iterative precision, and initial airflow on the iteration convergence.

A GIS Based Unsteady Network Model and System Applications for Intelligent Mine Ventilation

With the development of state-of-the-art technology, such as the artificial intelligence and the Internet of Things, the construction of “intelligent mine” is being vigorously promoted, where the intelligent mine ventilation is one of the primary concerns that provides the efficient guarantee for safety production in the underground coal mine system. This study aims to integrate the geographical information system (GIS) and the unsteady ventilation network model together, to provide location based information and online real-time support for the decision-making system. Firstly, a GIS based unsteady network model is proposed, and its algorithm steps are brought out. Secondly, a prototype web system, named 3D VentCloud, is designed and developed based on the front and end technique, which effectively integrates the proposed algorithms. Thirdly, the model is validated, and the system is applied to a real coal mine for ventilation solution, which demonstrates that the model is reasonable and practical. The online simulation system is efficient in providing real-time support. The study is potential and is expected to guide the real-time coal mine safety production.

Расчет устойчивости воздушных потоков в горных выработках по фактору тепловой депрессии в аналитическом комплексе «Аэросеть»

Underground fires are one of the most serious emergencies that occur during mining operations. Analysis of possible scenarios for its development is a mandatory measure when designing new mine workings and when developing a plan for immediate elimination of accidents at the existing mine workings. The main danger that an underground fire creates for the mine ventilation system is a change in the ventilation mode and, accordingly, a change in the direction of movement of the air and harmful gases released during combustion. It is almost impossible to calculate in manual mode all the possible scenarios for the development of an emergency for different places where underground fires occur. This confirms the need to develop algorithms for automated assessment of the effect of thermal depression from a fire on the stability of the air flow in all mine workings of the mine ventilation network. The authors consider two numerical algorithms implemented in the «Aeroset» analytical complex and solving two independent problems. The first of them is determining the air flow stability in the mine on the whole in the presence of a fire of a given heat emission rate in any place of the mine working. The second task is to find the critical rate of fire heat generation in stationary workings, leading to a loss of stability of the air flow in the mined-out spaces of the mine. The techniques of increasing the speed of calculations of algorithms are studied. The article also describes the developed tools for graphical analysis of the calculation results. Examples of using such tools in practice are given. It is concluded that the developed software tools allow to quickly model the stability of air distribution in the mine ventilation networks of arbitrary topology in the presence of underground fires, and conveniently visualize the calculations.

Study on fire smoke flow characteristics in the ventilation network and linkage control system in coal mines

SummaryIn coal mining, smoke flow from tunnel fires can easily cause a large number of deaths in the ventilation network. But the optimal smoke flow path control methods and automatic control system were lacked. In order to improve the efficiency of fire emergency rescue, the control mechanism and regional linkage control system for fire induced smoke flow in ventilation network was studied. Based on a ventilation system in coal mines, different fire scenarios for smoke flow were analysed using ventilation simulation software (VSS). Smoke flow control methods were simulated under different ventilation modes, a contrastive analysis was conducted for the respective effects and the optimal smoke flow path control methods were confirmed in different fire scenarios. A new type of ventilation facility, regional monitoring sub‐stations and remote linkage control platforms were developed for smoke control. A reliability evaluation model for the control system was established by Bayesian network. The failure of the linkage control is 98.9%, the monitoring sub‐station is 64.4%, the sub‐station communication is 43.9%; thus, a double insurance of the control process must be realised. Since its application, the proposed regional linkage control system has been repeatedly tested through fire drills, and good results have been obtained.

Cluster analysis-based anomaly detection in building automation systems

Faults in heating, ventilation, and air-conditioning control networks substantially affect energy and comfort performance in commercial buildings. As these control networks are comprised of many sensors and actuators, it is challenging to identify, often subtle, anomalies caused by these faults. In this paper, we develop a cluster analysis method for anomaly detection. The proposed method consolidates the building automation system data into a small number of distinct patterns of operation. These distinct patterns help energy managers discover and interpret anomalies through visualization of these patterns. The method was demonstrated with a year’s worth of building automation system data from 247 thermal zones and an air handling unit. Anomalies associated with zone temperature and airflow control were identified in about one-third of these zones. At the air handling unit-level, we identified anomalies related with three different faults: the use of economizer mode with perimeter heating, and leaky outdoor and return air dampers. The use of economizer mode with perimeter heating affected 39% to 52% of the total operation period and caused the outdoor air damper to remain fully open and the heat recovery unit to remain off during most of the heating season.

Decrease in coal losses during mining of contiguous seams in the near-bottom part at Vorkuta deposit

The problem of formation of extended zones with high rock pressure (HRP) from safety pillars at the boundaries of extraction pillars formed due to the mine layout of complex geometry is considered at the example of JSC Vorkutaugol mines. A detailed analysis of the remaining reserves of the near-bottom part of the deposit was carried out to estimate losses and the impact of HRP zones from the Chetvertyi protective seam to mining operations on the Troinoi upper seam along with the possibilities for the reduction of sizes of HRP zones at the account of expanding the underworked space. Due to research on the near-bottom part of the Vorkuta deposit, within the framework of the accepted layout, a zone at the Komsomolskaya mine and two zones at the Zapolyarnaya-2 mine were singled out, at which losses at the boundaries of the extraction pillars amount up to 13-22 % of the total resources of the mine field. The high volume of losses in these pillars indicates the relevance of research on the priority extraction impact of protective seams on the efficiency and safety of mining operations in the working area of underworked and HRP zones. Based on the analysis of foreign and Russian experience in the pillar cleaning-up at the boundaries of working areas and the methodical guidelines and instructions, a technological scheme was developed that allows increasing the coal mining recovery factor in the near-bottom part of the Vorkuta deposit from 0.75 to 0.9 without fundamental changing of the ventilation and transport networks and also without purchasing any additional mining equipment.
 The conducted economic calculations confirmed the effectiveness of implementing the new technological scheme for cleaning-up reserves at the boundaries of extraction districts. The economic effect is from 0.079 to1.381 billion rubles of additional profit from coaxial extraction pillars, depending on the mining and geological conditions and the size of the pillars.

Effects of ventilation conditions and procedures during a fire in a reduced-scale room

This paper deals with the consequences of applying ventilation procedures during confined fires. If the air intake duct is closed after the beginning of the fire, another risk may appear, namely the ignition of unburnt gases in extraction ducts. This configuration is typical of many industrial installations equipped with ventilation networks. Heptane and dodecane pool fires were performed in a reduced-scale compartment equipped with a mechanical ventilation network. Heat release rate, temperatures and unburnt species concentration were measured for different pan diameters, different ventilation flows, with and without closing the intake duct, to study fire development and the potential risk of ignition in the exhaust system. Empirical correlations to estimate unburnt species concentrations are given. Based on these correlations, lower flammability limit calculations and scaling laws, a risk assessment methodology is proposed and a decision support tool is provided. Experimental results clearly show that the auto-ignition of unburnt gases can happen near the extraction duct, with and without closing the intake duct.

The impact of accurately modelling corridor thermodynamics in the overheating risk assessment of multi-residential dwellings

Prolonged overheating can have serious cumulative effects on human health, resulting in heat exhaustion, heatstroke and even death. The frequency and severity of heatwaves will increase considerably in the future as a result of accelerating climatic changes compounded by increasing urbanisation.A recent overheating risk-assessment methodology, Technical Memorandum (TM)59: 2017 was developed by the Chartered Institution of Building Services Engineers (CIBSE) to address this problem, by providing a consistent framework for the evaluation of overheating risks in new homes. TM59 has for the first time highlighted the importance of including corridor heat transfer effects in the dynamic modelling of multi-residential dwellings. This paper investigates the strengths and limitations of current approaches to the modelling of corridors, based on a case study of three energy-efficient flats located in London. The results of modelling in accordance with TM59 guidance are compared with alternative approaches, using more realistic occupancy and weather information, and compared to empirically measured data. The findings of this study indicate that current practices in Building Performance Simulation (BPS) are likely to under-estimate the actual air temperatures in corridors. This study highlights the need for further research into the way in which corridors, flats and their interconnecting ventilation and heat transfer networks are commonly discretised in BPS models.

An Innovative Finite Tube Method for Coupling of Mine Ventilation Network and Gob Flow Field: Methodology and Application in Risk Analysis

Explosions and fires originated from longwall gob due to the formation of methane-air mixture have been a severe threat to coal miner’s lives. Many numerical studies on coal mine fire and explosion hazards have focused on the airflow in roadways and mine gobs. However, most of these studies isolate the gob from its surrounding roadways, and the network analysis and the CFD method are applied independently to model the two classes of airflows. This approach greatly limits the ability of simulating mine ventilation flow, especially unable to consider the effects of gob boundary conditions on air exchange between the gob and the surrounding airways. An innovative finite tube method (FTM) is developed to couple the one-dimensional mine ventilation network (MVN) and the 2D/3D gob flow field (GFF). In FTM, GFF is discretized into a finite number of flow tubes each of which is formed by any two adjacent stream lines. These tubes, representing the gob’s field flow, connect the MVN into a new coupling network. To solve the coupling model between MVN and GFF, an iterative solution technique is developed in which the MVN analysis is used to evaluate the boundary pressures for GFF simulation and in turn the FTM feeds the GFF results back to the coupling network. Based on the FTM approach, a model for gas migration in gob has been established for delineating the hazard zones of explosive methane concentration and spontaneous combustion. A computer program is developed to implement the FTM simulation. An illustrative example with five flow tubes representing the GFF is created to verify the stability and convergence of the FTM solution process. A simulation example also indicates that the accuracy of FTM is improved by 12% compared with previous method. Results of an application case show that the program is capable of quantitatively evaluating the gob’s risk zones prone for spontaneous combustion and gas explosion as well as performing risk analysis for various ventilation scenarios.

SOLUTION OF THE PROBLEM OF TRANSIENT AIR DISTRIBUTIONIN VENTILATION NETWORKS OF MINES, TAKING INTO ACCOUNT THERMODYNAMIC AIR FLOW PARAMETERS

This paper highlights the importance of calculating transient air distribution in mine ventilation networks, taking into account heat ventilation parameters of mine working atmosphere. The change in the temperature of an air flow as it moved along a working with a constant wall temperature was studied. For the network mathematical model of transient air distribution in a ventilation network of the mine, a new resolver was developed which takes into account the revealed regularities of change in air flow temperature from its velocity, temperature and cross-sectional area of mine workings, and allows calculating the change in air temperature as it moves along mine workings. The results of change in air temperature during its movement along the mine working were compared with analytical calculation method and in solving the problem by finite volume method. The obtained simulation results have good convergence. The deviation values obtained in the network model of transient air distribution from the finite volume method do not exceed 7 %.

Control strategies for ventilation networks in small‐scale mines using an experimental benchmark

AbstractIn view of the frequent ventilation network changes during production in underground mining, decreasing sensors and actuators without altering production control and safety is one of the chief engineering challenges. This work is focused on modeling identification and control strategies for underground ventilation networks in small‐scale mines using an experimental benchmark. Guidelines to obtain a discrete state space model are provided, considering the conservation laws in the network to define the structure of the linear model. The main purpose of the paper is to analyze the use of classic controllers in the mine ventilation system when there are limitations on the number of sensors and actuators available to design a feedback control system. A comparison of three classic control strategies is presented considering the a constraint on the available number of sensors. Experimental and simulation results are presented.

Prevention of multiple patterns of combined buoyancy- and pressure-driven flow in longitudinally ventilated sloping multi-branch traffic tunnel fires

Longitudinal ventilation is widely employed for smoke control in tunnels due to its relatively low installation cost and compactness. However, smoke control using a longitudinal ventilation system becomes complex when applied in a multi-branch sloping tunnel. In sloping tunnels, the stack effect and forced longitudinal ventilation may combine to produce multiple smoke flow patterns, even under identical or similar boundary conditions. Furthermore, such flow multiplicity behavior is considerably more complicated in a multi-branch sloping tunnel than in a single sloping tunnel. In this paper, an optimal longitudinal ventilation strategy was proposed to prevent smoke flow multiplicity induced by the combined buoyancy- and pressure-driven effects of a downhill sloping, longitudinally ventilated multi-branch tunnel fire. The ventilation network of the multi-branch tunnel was divided into three basic regions: the branches upstream of the intersection node, an on/off-ramp, and the other branches downstream of the intersection node. Based on this division and a hydraulic analysis, the multi-branch tunnel was characterized as a system consisting of several three-branch structures. The critical fan-induced pressure rise required to prevent smoke flow multiplicity was then derived by a potential analysis method according to the fire location in the tunnel. The optimal strategy was achieved by integrating the fan-induced pressure rises in each tunnel branch. The results reveal that the total pressure at the branch intersection node can be varied to regulate the integrated fan-induced pressure rise in each branch. The efficiency of this strategy in preventing flow multiplicity for all typical fire source locations in a three-branch structure was then demonstrated via numerical simulations. The proposed approach has implications for improving tunnel emergency ventilation design and fire protection.

Applications and verification of a computational energy dynamics model for mine climate simulations

A complete thermodynamic model is described for temperature and heat flow distribution simulation for ventilation networks in underground mines. The method is called the Computational Energy Dynamics (CED) model of the heat, mass, and energy transport. The Thermal and Humidity (TH) transport elements of the full model are described for advection, convection, and accumulation, encompassing heat capacity, radiation, latent heat for evaporation, and condensation in the airways, as well as variable heat conduction and accumulation in the rock strata. The thermal flywheel effect for time-dependent temperature field applications is included in the model solution. A CED model validation exercise is described, directly evaluating the iterated, minimized energy balance errors for the mechanical and thermal energy components for each network branch after a converged solution is determined. A simulation example relevant to mine safety and health is shown with the CED-TH model, demonstrating its capabilities in efficiency and accuracy in comparison with measurement results.

Ventilation Monitoring and Control in Mines

Ventilation monitoring and control in mines are becoming an integral part of day-to-day activity for maintaining health and safety of miners. The authors evaluate potential real-time monitoring solutions for detecting and reducing diesel particulate matter, mine fires, and dust in situ, and examined the state-of-the-art use of ventilation monitoring and control in underground mines for detecting and reducing air contaminants to acceptable regulatory limit. Authors review relevant documents, including research papers, trade publications, and manufacturers’ website-based information, to identify research gaps. The authors also evaluate contemporary sensors (airflow, gas, dust, silica), control system and software technologies, data transport systems, Industrial Internet of Things, ventilation network simulators, and control devices to identify potential health and safety research gaps. In this study, examples of some mines from Canada, Australia, and the USA are included where ventilation monitoring and controls have been applied. Overall, this review identifies multiple challenges and research gaps in applying mine monitoring and control systems that could be the focus of future research, offering potential improvements to miner safety and health and financial benefits.