Auxiliary Ventilation Research Articles

Auxiliary Ventilation Control Technique in Heading Laneway

Auxiliary Ventilation Control Technique in Heading Laneway

Fuzzy Control Technique of Auxiliary Ventilation in Heading Laneway

Aimed at air quantity requirement and energy conservation at normal ventilation as well as safety and quickly at methane discharging, this study discussed the design process of self learning fuzzy controller based on basic fuzzy model. Firstly, the control system block is described. Then basic fuzzy model is introduced. Auxiliary ventilation is time-varying parameters, nonlinear and large hysteresis system. Therefore, the design includes the normalization, reference model, time-delay, sample cycle, calculation method and control rule modification. The partial fan speed adjustment adopts Direct Torque Control (DTC). Based on theoretical analysis and simulation, combing DSP chip with Intelligent Power Module (IPM), auxiliary ventilation fuzzy control adjusting speed experiment system is established. Experimental results have shown that the system can safely and efficiently fulfill the function of normal ventilation and methane discharging.

Conventional and numerical models of blasting gas behaviour in auxiliary ventilation of mining headings

A study has been carried out in a coal heading, excavated by drilling and blasting in a deep underground mine located in Northern Spain (Hullera Vasco Leonesa S.A.), by measurements of blasting gases, CO and NO2, in three cross-sections of the heading located at 20, 30 and 40m from the heading face.Mathematical models of gas dilution, according to the dilution time after blasting, have been developed. These models show the differences between the obtained values by application of these experimental models and the values of other mathematical model in common use.The mentioned differences indicate the need to obtain in each underground work its own dilution models of blasting gases. This need is more important when the mass of explosives, the cross sectional area of the heading and the conditions of the auxiliary ventilation keep away from the ones used in order to obtain the mathematical model in common use.4D models have been developed by Computational Fluid Dynamics (CFD) through software Ansys CFX 12.0. The CFD model results have been validated and compared to experimental models obtained in the measurement programmes.From these CFD models other dilution behaviour mathematical models of blasting gases can be developed for other cross sectional areas, other mass of explosives and other ventilation parameters.The experimental mathematical models and CFD models obtained allow us to analyse how the blasting gases behave and therefore to know in which conditions it is safe for the workers to return to a blasted area.

Some approaches to improve ventilation system in underground coal mines environment – A computational fluid dynamic study

This study addresses gas control in a typical “room-and-pillar” structure in an underground coal mine via mathematical model utilizing commercial computational fluid dynamic software. In essence, the model considers conservation of turbulent mass, momentum, species, and energy. Several turbulence models are tested and compared with published experimental data; good agreement between model prediction and experimental data is obtained for Spallart–Almaras turbulence model. Various design features were evaluated, e.g., flow stopping designs for improved quality (e.g., removal of contaminants) and quantity control (e.g., magnitude and direction of airflow). We further focus on the cross-cut region where rapid mining development take place, several ventilation scenarios with and/or without additional auxiliary ventilation are investigated for effective removal of methane. Two different cutting scenarios in rapid mining development are also evaluated. The advantages and limitations of each design are discussed and compared not only in terms of quality and quantity, but also in terms of the overall pressure drop which represent the associated cost of ventilation system.

Optimisation of underground ventilation systems by means of neural networks

The optimisation of the auxiliary ventilation network of underground mines entails the right choice of fans and duct characteristics. Once the decision-making team has selected the appropriate set of ventilation hardware, the duct line is installed across a main drivage and ends up to the most productive working areas. However, when there are many possible duct line routes from the auxiliary fan to the duct line open end, as is the case in the room and pillar mining method, the choice of a cost effective duct line route, in terms of the total length and bending of the ducts involved, is important for the minimisation of the operating cost of ventilation. In this paper, the problem of finding a cost effective duct line route, among a definite number of possibilities, is tackled with a modified discrete Hopfield network. It is shown that the network provides the optimum result for a trivial case. The implementation of the network on a realistic case is shown to be superior to results from the A* algorithm. However, the feasibility of the proposed solution is highly dependent on mining issues and on the right choice of number and distribution of control points that realise all possible routes from the fan to the headings.

Study on Blasting Driving Roadway Single Transformation Ejector Auxiliary Ventilation

Faced with the serious pollution problems of blasting smoke after blasting with the ventilation method based on pressure, using single transformation ejector auxiliary ventilation was raised in the paper, namely ventilation based on pressure was put into use when it was normal, but ejector auxiliary ventilation was used after blasting. The simulation of the condition by fluid analysis software when ejector auxiliary ventilation and ventilation method based on pressure were conducted, and a inclusion was presented that ejector auxiliary ventilation had a good effect on exhausting smoke for the long tunnel with small section, and it has an advantage of shortening exhausting smoke time and less pollution to the roadway, Ventilation can be divided into two phases, when the ejector inlet is submerged in the smoke, smoke is suck out mainly through ventiduct. when the ejector inlet is exposed to fresh air flow, the ejetor assist smoke get out through ventiduct.

Reliability estimation of auxiliary ventilation systems in long tunnels during construction

Ventilation system should blow large quantity of airflow particularly in case of toxic or explosive gasses emission from the wall rocks and face, especially in long tunnels. In these cases, multiple jet fans are usually required, so that they could be grouped together as serial, parallel or combined arrangements through ventilation system or equally spaced along the tunnel. There is a serious requirement to have some reserved jet fans along with the main once, so that the operation of the ventilation system could be reliable. Operation of a ventilation system is usually evaluated by experiences and engineering judgments which follow empirical methods. The aim of this paper is to introduce an approach to evaluate reliability of ventilation system in the long tunnels. The method is based upon using the failure rate time to determine the probability of the failure of an active jet fan and also the repair rate time to determine the probability of repairing the out of work ones .In this approach, the active and standby jet fans are modelled as a stochastic process. Therefore, the probability of replacing each failed jet fan with a standby jet fan is estimated using Markov Chains theory .From this point of view a more realistic decision-making for the number of standby jet fans and also reducing the risk as well as uncertainties can be based upon the analysis of such a results.

Auxiliary ventilation in mining roadways driven with roadheaders: Validated CFD modelling of dust behaviour

The production of dust when driving mining roadways can affect workers health. In addition, there is a decrease in productivity since Mine Safety regulations establish a reduction in the working time depending on the quartz content and dust concentration in the atmosphere. One of the gate roadways of the longwall named E4-S, belonging to the underground coal mine Carbonar SA located in Northern Spain, is being driven by an AM50 roadheader machine. The mined coal has a high coal dust content. This paper presents a study of dust behaviour in two auxiliary ventilation systems by Computational Fluid Dynamics (CFD) models, taking into account the influence of time. The accuracy of these CFD models was assessed by airflow velocity and respirable dust concentration measurements taken in six points of six roadway cross-sections of the mentioned operating coal mine. It is concluded that these models predicted the airflow and dust behaviour at the working face, where the dust source is located, and in different roadways cross-sections behind the working face. As a result, CFD models allow optimization of the auxiliary ventilation system used, avoiding the important deficiencies when it is calculated by conventional methods.

Models of methane behaviour in auxiliary ventilation of underground coal mining

Abstract Studies have been conducted in a roadway excavated in a coalbed of a deep underground coal mine located in Northern Spain (Hullera Vasco Leonesa SA), by both airflow velocity and methane concentration measurements. Modelling of ventilation and methane behaviour of that roadway by Computational Fluid Dynamics (CFD), through software Ansys CFX 10.0, is presented. A good correlation was found between the experimental data and the results predicted by CFD. Then a comparison of the results obtained by conventional methods with the results obtained by CFD 4D modelling, for the auxiliary ventilation in a dead-end roadway, was made. Although conventional methods give satisfactory results when considering methane dilution, this research proves that there may be some roadway zones in which methane concentration is higher than regulation values. This is owing to the airflow and methane behaviour in the roadway with the presence of dead zones, and the fact that only a part of the airflow provided by the fan reaches the working face. CFD modelling allows us to know in which zones of the roadway it may be necessary to reinforce forcing ventilation by additional systems, such as a forcing system with exhaust overlap, jet fans, spray fan systems or compressed air injectors.

Statistical model for the volume rate reaching the end of ventilation duct

Auxiliary ventilation is used to ventilate dead-ends of the drivages, and the most common method employed is to use auxiliary fans and ducting. In order to provide a safe and comfortable environment, it is necessary to provide sufficient air to the working areas. The optimum design of auxiliary ventilation systems may be difficult owing to the methods used in the design of such systems that require complex calculations. In this study, by evaluating data gathered from Turkish Hardcoal Enterprises, a predictive model of the volume flow rate reaching the end of a leaky ventilation duct for a simple auxiliary ventilation system was developed using multiple regression analysis. The independent variables that enter the regression were chosen as duct diameter, fan flow output, fan operating pressure, frictional pressure drop, duct length, duct resistance, and resistance coefficient of leakage paths. The coefficient of determination ( R 2) obtained for the predictive model was 0.931, and the residual analysis indicated that the model was statistically acceptable. Also, by using the two-sample t-test, it was shown that the developed regression model was consistent with the results obtained from another data set not included in the derivation of the presently developed regression model.

The computational modeling of the ventilation flows within a rapid development drivage

In recent years, the increase in the drivage rates of continuous miners has exacerbated the environmental conditions experienced within the rapid development headings of many deep UK coal mines. This paper presents the conclusions drawn from the analysis of a series of validated computational studies conducted to assess the effectiveness of alternative auxiliary ventilation systems on the mitigation of any adverse environmental conditions experienced within these drivages. A series of steady-state computational fluid dynamics (CFD) models were constructed to replicate the ventilation flow patterns seen at the head end of a drivage during the various stages of a cutting and bolting cycle. The results obtained from these simulations were compared against the data obtained from a series of full scale ventilation experiments conducted within a rapid development drivage of a representative UK deep coal mine. It is concluded that CFD models may be successfully used to identify the ventilation characteristics associated with the various auxiliary ventilation systems during a typical cutting bolting cycle.

The influence of ventilation variables on the volume rate of airflow delivered to the face of long drivages

Auxiliary ventilation is performed by carrying intake or return air in ducts. The complete elimination of air leakage from or into the ducting system is impossible due to duct quality and numerous joints in ducting system. The auxiliary ventilation systems for long drivages often require the use of multiple fans. Fans are installed in series and separated from each other in fixed or variable lengths. There are many methods proposed for the analysis air flow problems in leaky ducts. Due to the lengthy calculations, computers are often needed to conduct the analyses. In this study, a method known as “series–parallel combination of the duct and leakage path” has been introduced and a computer program has been developed based on this method. In order to design the conditions of an auxiliary ventilated drivage, in situ measurement have been made in Western Lignite Enterprises (GLI) OMERLER underground coal mine (Turkey) and the related data necessary for this study was collected. The presently developed program was tested using these data, and it was found that the measured and calculated values are quite close. The effective operational parameters governing auxiliary ventilation have been investigated and the effects of these variables on the volume rate of air flow reaching long drivage face have been examined by using linear regression analysis. Finally, it was concluded that the increase of duct diameter has prime importance in achieving the adequate air flow to the face and that for the auxiliary fans considered in this study the selection of fan does not greatly affect the volume rate reaching the face in a long duct line.

The ventilation and climate modelling of rapid development tunnel drivages

Abstract The extraction of minerals and coal at greater depth, employing higher-powered machinery to increase production levels has imposed an increased burden on ventilation systems to maintain an acceptable working environment. A deterioration in the climate experienced within these workings may also adversely affect the health and safety of the workforce. In the UK, mineral extraction is now being practiced at depths of over 1000 m. In addition, the adoption of continuous miner and tunnel bolting support methods has permitted improved development rates to be achieved at the cost of increased emissions of dust, gas and heat and humidity. There is a recognized need to improve the efficiency in the design and operation of auxiliary ventilation systems to maintain an adequate underground environment and climate. Any improvement achieved in the quality, quantity and control of the delivered ventilation will assist in the provision of improved gas and dust dilution and climatic control. Due to the constraints imposed by the mining method, there may be an economic or practical limit to the climatic improvement that may be obtained by the sole use of ventilation air. Where this limit is identified, there may be the need to consider the selective application of air-cooling systems. The paper details the construction of a computer based climatic prediction tool developed at the University of Nottingham. This work builds upon earlier research (Ross et al., 1997, Proceedings of 6th International Mine Ventilation Congress, SME, Littleton, CO, pp. 283–288) that developed a prototype model for short tunnel developments. The current model predicts the psychrometric and thermodynamic conditions within long rapid development single entry tunnel drivages. The model takes into account the mass and heat transfer between the strata, water, machinery and the ventilation air. The results produced by the model have been correlated against ventilation, climatic and operational data, obtained from a number of rapid tunnel developments within UK deep coalmines. The paper details the results of a series of correlation and validation studies conducted against the ventilation and climate survey data measured within 105s district Tail Gate tunnel development at Maltby Colliery, UK. The paper concludes by presenting the results of a case study that illustrate the application of the validated model to the design and operation of an integrated mine ventilation and cooling system. The case study illustrates the effect that an increased depth and hence increased virgin strata temperature has on the climate experienced within rapid tunnel developments. Further investigations were performed to identify the optimum cooling strategy that should be adopted to maintain a satisfactory climate at the head of the drivage.

Modelling of auxiliary ventilation systems

In subsurface excavations, auxiliary ventilation systems are an important and integrated component of the overall ventilation scheme. Without adequate auxiliary ventilation, it is impossible to provide sufficient air to working faces, regardless of the quantity or quality of air in the main airways. Extended development headings are typically ventilated using fan and duct systems, which either force or exhaust air through the duct. The optimum design of such systems can be complex, depending on factors such as duct resistance, leakage and diameter, fan selection and spacing, and shock losses. This paper describes the development and application of a comprehensive design process for auxiliary ventilation systems. Included is a summary of published theory and literature, a description of software development, information and results from detailed field measurements, and a description of the application of the software to the design of an actual extended auxiliary fan and duct system.

Modeling ventilation and dispersion for covered roadways

A series of computational fluid simulations was conducted to assess the relative impacts of several forced ventilation configurations on the distribution of atmospheric pollution concentrations from vehicles operating within a covered roadway. These conditions are frequently encountered in urban highways, airports, parking structures and so forth. Ventilation configurations tested included ceiling curtains and jets. A simple 2D geometry without artificial ventilation was used as a base case together with a worst-case flow scenario that assumed no transverse ambient wind flow. The base-case simulations were compared to simulations for various auxiliary ventilation alternatives. The simulations demonstrate that ventilation is necessary to effectively minimize peak ambient concentrations in covered roadways. Auxiliary overhead ventilation ports are found to result in the most dramatic improvement in pollutant concentrations. The simulations also indicate that regions of low velocity and vortex-type flow patterns with flow reversals are characteristic of situations with very high values of peak pollutant concentrations.

大型掘進機械の存在する掘進先における併用通気に伴うメタンガス挙動と分岐管の効果

大型掘進機械の存在する掘進先における併用通気に伴うメタンガス挙動と分岐管の効果

Simulation of Thermal Environmental Conditions in Heading Face with Forcing Auxiliary Ventilation. Control of thermal environmental conditions in locally ventilated working place. 1st Report.

Numerous studies have been made to control the climate conditions in underground mines, but most of them are concentrated on a single roadway with through airflow, and those on the simulation of heat problems in developing roadway with local ventilation are very few. Therefore it is necessary to establish a proper method to simulate the thermal environmental conditions within the working face with auxiliary ventilation for controlling the thermal climate there effectively.As a basic study on control of the thermal environment in working face with auxiliary ventilation, the CFD method is employed to simulate the transfer of heat and moisture between rock surface and the airflow at a heading face with forcing auxiliary ventilation. Based on the simulation results, the distribution of local heat-transfer coefficient and its relationship with airflow rate, variation of heat transfer flux from the strata to the ventilation air with time and wetness fraction, the distribution of rock temperature and its variation with time elapse are discussed in the paper.The study provides an important basis for establishing a proper method to predict the thermal environment conditions on locally ventilated working places.

Prediction of Climatic Conditions in Developing Roadway with Forcing Auxiliary Ventilation System. Control of thermal environmental conditions in locally ventilated working place. (2nd Report).

Finite difference method is applied to simulate the thermal environmental conditions in a developing roadway with forcing auxiliary ventilation. The local heat transfer coefficients which were obtained by simulating the heat and mass transfer process in working face with CFD method are coded into the program for the prediction of the thermal environmental conditions in working face. The 3-demensional heat conduction in surrounding strata rock, the heat and mass transfer between the airflow in the duct and roadway, the heat and mass transfer between wet rock surface and roadway air are simulated with taking into consideration the air leakage of the ventilation duct and the advance of the working face. The distribution of the air temperature and relative humidity of the air both in the duct and roadway, and their variation with time can be predicted by the program when forcing auxiliary ventilation is used. The model for the prediction of the thermal environment can provide a reliable approach to predict if a climate problem exists in the design stage, allowing suitable ameliorative measures to be tested and evaluated prior to the start of driving. It will contribute to establishing the rational method for improvement of the thermal environment, by proposing more effective technological guide in the control of heat problems in working face with auxiliary ventilation.

局部通気の風速測定とＣＦＤによる数値解析 掘進切羽における掘削機械による風速分布への影響 Ｉ

Although forced auxiliary ventilation is widely employed at heading faces, it is not easy to design an optimum ventilation system for a working face because of the complexity of airflows. Therefore, it is essential to obtain airflow patterns at the face where a heavy machine works.From this point of view the influence of a machine such as a road header upon airflow patterns are investigated by both methods of measuring of airflow velocity in reduced scale model and using Computational Fluid Dynamics (CFD).As a result, some important information is obtained concerning the influence of a machine upon airflow patterns in the face. A vortex is generated in the space between a face and a machine, and the wake was created behind a machine. The authors pointed out a possibility that these flows may lead the stagnation of both dust and gases.The results also show that the CFD is an effective tool for simulating the airflow under varied conditions of the ventilation system.

空気の流れのパターンに与える通気条件の影響 ＩＶ 局部通気を行う作業箇所における環境条件の解析

Although forced auxiliary ventilation is widely employed at heading faces, it is not easy to lay out the optimum ventilation system for a given heading face mainly because of the complexity of airflow. Therefore, it is essential to obtain detailed knowledge about the influence of the conditions of the ventilation system upon airflow patterns at the face. From this point of view the effects of the position of the outlet of the air duct, the airflow rate from the duct and others are investigated by means of Computational Fluid Dynamics (CFD).As a result, much important information is obtained concerning the influence of conditions of the ventilation system upon airflow patterns in the face. The results also show that the computation method, which the authors proposed in a previous report, is an effective tool for simulating the airflow under varied conditions of the ventilation system.