Mine Fan Research Articles

An Analysis of the Methane Explosion in the Area of the Return Shaft Bottom at Mine

Methane explosions are one of the greatest hazards in the coal mining industry and have caused many accidents. On 27 July 2016 at approximately 11:01 a.m., an explosion of methane occurred at the bottom of Zygmunt return shaft at the depth of 411 metres. The explosion resulted in one casualty. The article presents the results of, and the conclusions from, an in-depth analysis of the changes in the parameters of mine air, especially methane concentration, air flow and the operation of mine fans, recorded by sensors installed in the workings and in Zygmunt ventilation shaft around the time of the accident. The analysis was based on signals recorded by the monitoring system, related to the evolution of methane and fire hazards prior to and after the accident occurred. An attempt was made to identify the cause and the circumstances of the methane explosion at the bottom of the return shaft.

Fault Diagnosis of Rolling Bearings in Primary Mine Fans under Sample Imbalance Conditions.

Rolling bearings are crucial parts of primary mine fans. In order to guarantee the safety of coal mine production, primary mine fans commonly work during regular operation and are immediately shut down for repair in case of failure. This causes the sample imbalance phenomenon in fault diagnosis (FD), i.e., there are many more normal state samples than faulty ones, seriously affecting the precision of FD. Therefore, the current study presents an FD approach for the rolling bearings of primary mine fans under sample imbalance conditions via symmetrized dot pattern (SDP) images, denoising diffusion probabilistic models (DDPMs), the image generation method, and a convolutional neural network (CNN). First, the 1D bearing vibration signal was transformed into an SDP image with significant characteristics, and the DDPM was employed to create a generated image with similar feature distributions to the real fault image of the minority class. Then, the generated images were supplemented into the imbalanced dataset for data augmentation to balance the minority class samples with the majority ones. Finally, a CNN was utilized as a fault diagnosis model to identify and detect the rolling bearings' operating conditions. In order to assess the efficiency of the presented method, experiments were performed using the regular rolling bearing dataset and primary mine fan rolling bearing data under actual operating situations. The experimental results indicate that the presented method can more efficiently fit the real image samples' feature distribution and generate image samples with higher similarity than other commonly used methods. Moreover, the diagnostic precision of the FD model can be effectively enhanced by gradually expanding and enhancing the unbalanced dataset.

Estimating Energy Consumption of Mine Fans in Underground Mines in Case of Uncertainty of Fan Influence Zones

Estimating Energy Consumption of Mine Fans in Underground Mines in Case of Uncertainty of Fan Influence Zones

Effectiveness of ventilation regulation in a simple diagonal system of underground mines

Purpose. Each ventilation system has its own important elements, such as the various branches of the system, which can be connected in a normal and diagonal pattern, ventilation regulators and fans. Based on a professional approach to the analysis of this aeration system, a comparison of reliability results has been conducted, which indicates the real state of the microclimate in underground mines, affecting the increase in the prospects for the development of mining activity. Methods. This paper deals with the problem of ventilation in underground mines, especially in diagonal systems, and the importance of regulating ventilation to provide the required amount of air (Q, m3/min) through the entire system, taking into account the determination of the main fan depression. Findings. To ensure the required (designed) amount of air through the system branches, various methods of effective regulation are used in mining engineering. Therefore, based on research and measurements in different mine workings, our findings provide complete safety and comfort of microclimate during mining activity. Originality. The measurements performed and the database created according to the values and results obtained from the analytical calculations present the best possible estimate, which is substantiated in the paper. Practical implications. The problem of calculating and regulating aeration for a simple diagonal system has been solved, taking into account the determination of the main mine fan depression before and after the use of aeration regulators.

SELF-STARTING OF SYNCHRONOUS MOTORS WITH COMPENSATION INERTION OF THE EXCITATION CONTOUR

The actual scientific problem is solved in the work, which consists in the development, theoretical and experimental researches of devices for self - starting of synchronous motors with compensation of inertia of excitation circuit. The aim of the work is to increase the reliability of the self-starting mode of synchronous motors of responsible mechanisms to maintain the continuity of complex technological processes. In the event of natural disasters and natural disasters, power outages can cause long-term disruptions of technological processes, large material losses, and in some cases fires and explosions, which can lead to human casualties and significant economic damage.
 Under these conditions, the mode of restarting synchronous motors must be used to power the responsible electric drives of mechanisms, such as mine fans, water pumping stations.
 To limit the dynamic loads, it is necessary to have the smallest possible value of e.r.s. stator SD in order to limit the switching current, which can be achieved by using various methods and means of extinguishing the field, increasing the time of introduction of automatic re-inclusion or automatic inclusion of the reserve. The calculated dependences of the self-starting modes of SD when extinguishing the magnetic field due to the inclusion of capacitive energy storage devices are obtained. The developed device for self-starting of SD with a capacity of 1000 kW of the drive unit of the pump unit with ENE was implemented at the pumping station of the Dnieper Metallurgical Plant. The efficiency of the developed device does not depend on the presence of voltage that supplies the excitation system in the self-starting mode. The use of ENE in the excitation circuit provides compensation for the inertia of the OZ and increase the input coin and intensive quenching of the magnetic field. The developed devices provide reliable self-starting of synchronous electric drives of mechanisms with continuous technological processes regardless of the presence of voltage in the power supply system of the exciter.

Investigation of aerodynamic schemes of reversible mine fans

The article considers the aerodynamic scheme of the main ventilation fan with high aerodynamic properties in reverse operation mode based on the use of a rotating input guide vanes. The dependences of the setup angles of the blades of the input guide vanes and the rotor, when the fan is switched to the reverse mode, on the required flow coefficients and fan pressure at certain parameters of the profile cascades at a mean radius are revealed. Using the example of the designed aerodynamic schemes, the influence of the swirl of the flow in the guide device, the solidity of the blade cascades of the rotors and the torsion of the blades on the aerodynamic characteristics of the reversible fan operation mode, calculated in the ANSYS CFX, is shown. Obtained fan aerodynamic scheme provides a performance in the reverse mode operation equal to 0.96 of the performance of the direct mode in the same ventilation network.

Optimal adjustment of mine fan geometry and operation

Mine fans consume significant electrical power, so it is important to ensure high efficiency of their operation. The aim of this study is to develop a method to determine the most economically efficient method to adjust axial fan geometry and operation at the maximum average efficiency in all operating modes. The method includes a developed mathematical model of the single-stage axial fan duty and a genetic algorithm for optimizing the fan parameters. The initial data for the mathematical model were the geometry of the fan blades of the average radius and the parameters of the fan operating mode. The result of the calculation was the fan efficiency in a preset operating mode. Two adjustment scenarios are modeled: fans with variable pitch blades and fans with variable rotation speed. The fan efficiency was determined by calculating the total pressure loss at the unit stage at the middle radius with regard to the loss at the blade tips. Since the mathematical model contains a large number of independent parameters, and there exists the possibility of local extrema, the optimization is performed using the genetic algorithm. The mathematical model of the fan with variable pitch blades was tested using experimental data. The error of the mathematical model in continuous modes at high efficiency (>75%) never exceeds 1.5%. As a case-study, the optimal fan parameters are determined for two preset operating modes and for two adjustment scenarios of fans with variable pitch blades and with variable rotation speed. On the basis of the obtained geometric parameters at the average radius of blades, using the constant circulation law, the fan designs were developed and then investigated by numerical simulation in CFX program. It is shown that if the air flow rate in operating modes differs significantly and the pressure is not, it is advisable to use fans with variable pitch blades.

Blade crown design for high-speed axial mine fans

The authors propose the aerodynamic designs for the high-rate axial main mine fans having the load capacity of 696-914 kW/m2, which is 4-5.3 times higher than the currently manufactured axial fans have. This result is achieved through the increased blade tip speed up to 220 m/s owing to the topological optimization of the material distribution within the physical volume f the blade by the minimum mass criterion. The new blades have an oriented structure and mass 50-70% less than the masses of the single-piece blades at the same allowable stresses and strains.

Estimating Energy Consumption of Mine Fans in Underground Mines in Case of Uncertainty of Fan Influence Zones

Estimating Energy Consumption of Mine Fans in Underground Mines in Case of Uncertainty of Fan Influence Zones

Использование турбовинтовых вентиляторов с устройством интенсификации аэрации карьеров для проветривания выработанного пространства

The application of open-pit fans on the basis of turboprop aircraft engines, working in complex with the devices for intensification of aeration of worked-out space, for ventilation of open-pit mines is considered. The most effective for the open-pit mines ventilation is the use of isothermal jets created by the mine fans with gas-turbine aviation engines. The principle design of the device for intensification of open pits airing represents inclined profiled blades installed on supports. Such a design allows to direct the developed ventilation jet into the quarry, as well as to increase its velocity at the outlet into the mined-out space in the constructions of confusers (blades--top platform of leeward side). The application of the complex, consisting of the ventilation installation and the device of quarries aeration intensification, installed on the surface, allows to increase considerably the volume of the air, supplied to the worked-out space, in comparison with the location of the fan in the pit, to decrease the noise levels in the working zones. By means of modeling qualitative and quantitative aerodynamic characteristics of the offered ventilation scheme (location of the fan and aeration intensifier, pattern of air currents in the quarry, speeds distribution) are defined, its application efficiency and conditions are evaluated

Research on the Fault Diagnosis Method of Mine Fan Based on Sound Signal Analysis

The underground local fan and auxiliary fan also play a vital role in the underground air quality, compared with the system fan. However, the number of underground local fans and auxiliary fans is large and widely distributed, which is disadvantageous to adopt the same method of online monitoring and fault diagnosis method as the system fan. In order to find a new fault diagnosis method, which is cost-effective and reliable, this paper proposes a fault diagnosis method based on sound signal. It analyzes the source of fan noise and studies the overall scheme of mine fan fault diagnosis expert system based on sound signal. The fault expert system consists of four parts: signal acquisition and noise elimination, feature extraction, state recognition, and fault diagnosis. Its principle is briefly introduced. The denoising method of wavelet is adopted in this paper. Wavelet packet is used to extract the characteristics of sound signal, and the energy size and energy proportion of each frequency component are used as the basis of knowledge acquisition and reasoning. Through the analysis of the measured signals of the fan in the normal operating state, the feature vectors were extracted as the basis for the discrimination of the normal state after noise elimination. At the same time, the audio processing software was used to simulate the sound signals in three fault states. Then, the feature vector of the fault state is extracted, which is obviously different from that of the fan in the normal operation. As the basis of fault state analysis of the expert system, it lays the foundation for the realization of the expert system of mine fan equipment running state diagnosis.

Measurement and Characteristic Analysis of Electromagnetic Disturbance of Coal Mine Fan Converter

With the extensive use of converters in high-power ventilator, shearer, road header, conveyor, hoist, and other coal mine equipment, the electromagnetic disturbance problem of the converter is worthy of attention. In this paper, the field measurement and statistical method are used to analyze the radiation interference characteristics of frequency converter. Then, a typical fan converter is taken as an example, and the electromagnetic disturbance of the converter is tested in four key positions and two working frequencies, respectively. Multiple sets of data and spectrum are obtained by using a spectrum analyzer and other instruments, and the dominant frequency characteristic parameters of the converter are analyzed emphatically. The small sample data adopts the Shapiro–Wilk test, and the 80%/80% rule was used for statistical analysis. Finally, we got five common frequencies of electromagnetic interference generated by the converter (electric field dBμV/m). The CH4 sensor and other sensors work near these five dominant frequencies, which may affect the normal operation of the sensor and cause alarm. The test and analysis method proposed in this paper can be used to obtain the characteristic parameters of the converter electromagnetic disturbance, which can be used as a reference for the design of the immunity of sensors or control instruments.

ON OPTIMUM SYSTEM OF VENTILATION OF THE RIKOTI MOTOR ROAD TUNNEL

The main characteristics of the Rikoti motor road tunnel are: length -l 700 m. cross-section areas of transport zone -60 m2 and of air duct - 17 m2, ventilation system is longitudinal-cross wise. Fresh air gets into the tunnel through East and West portals and is sucked off with the help of four ventilators ВОД- 21м mounted at the portals. Draw off from transport zone of the tunnel is realized through windows arranged in chessboard order in tunnel falce ceiling, in two rows of 40 windows in each row. Flow section of the windows is regulated manually with the help of gates. The cross-section area of the fully open window is 0.5 m2. The mentioned system of aeration does not provide the tunnel with the necessary quantity of air at maximum intensity of motor transport motion. Besides, a great quantity of electric power is consumed as there are used nonregulated mine fans and poor quality window constructions. The given work proposes using the longitudinal ventilation diagram with jet fans. As a result of realization of the proposed measures the annual economy of about l mln lari is expected.

DESIGNING ATTACHMENTS FOR BLADES OF AXIAL MINE FANS

The subject of the research is the attachment of fixed blades of axial mine fans. Within increasing rotational speeds (and increasing centrifugal forces as a result), the loads on the blades and, thus, on their attachments grow. Accordingly, the design of the blade attachment should ensure the required strength of the structure. The key objective of the blade attachment design is to keep stresses and strains within permissible limits (so that the effective stresses are beyond the ultimate values) at the preset rotational speeds. Then methods used to meet the objective include selection of the appropriate characteristics of the materials, variation of structure of the blade attachment and calculation of the attachment strength at each stage to select the most efficient parameters.

Design of Frequency Conversion and Soft Start Cooperative Control System for Mine Fan

In order to improve the safety and reliability of mine fan control system and realize remote control in dual operation modes, a cooperative control system of frequency conversion and soft start of mine fan was developed based on PLC. On the basis of analyzing the position of coal mine in China’s economic development and the role of coal mine ventilation system, this paper expounds the working principles of mine soft starter and mine frequency converter, and designs a cooperative control system of mine fan frequency conversion and soft start based on PLC, which realizes remote control of mine fan starting, running and stopping, and has the functions of voltage, current, wind speed and air volume parameter monitoring and fault protection.

Design of control and frequency conversion speed regulation system for mine fan

In order to improve the accuracy and stability of the control system of mine fan, the control and frequency conversion speed regulation system of mine fan was developed based on PLC. Based on the analysis on control technology for mine fan, puts forward the inverter, soft start double mode control strategy, combined with the design of PLC control system hardware circuit and software program, the realization of mine fan starting and soft start, reasonable speed regulating, stop running process control, at the same time have the parameters such as voltage, current detection and fault protection function.

Rationale for main fans service life in the conditions of changing load

Research aim is to study basic regularities in functional condition change of main fans included in the confi guration of main mine ventilation installations depending on the technological service conditions. The research also aims to determine the standard service life of main fans with the account of the diff erential analysis of the destructive factors, structural features, intensity and modes of operation of ventilation plants. 108 "Izvestiya vysshikh uchebnykh zavedenii. Gornyi zhurnal". No. 6. 2020 ISSN 0536-1028 Research methodology. Based on the analysis of main fan installations structure and differential analysis of technological factors affecting the functional efficiency of main fans, a mathematical model has been proposed which determines the standard and residual life of the main fan with the account of the changing load. Results and analysis. As a result of studying the impact of destructive factors on the main functional parts of the main fan, an equation has been proposed, which takes into account the physical properties of the material the fan elements are made of together with the quantitative effect of the external physical factors on the machine’s operation. Research results show that the resource of the main fans should be determined based on the useful life of the machine’s major component, i.e. mainshaft, with the account of the machine’s operation mode. Conclusions and scope of results. Circuit designs of mine ventilation plants predetermine the main fans service life. The service life should be established at the stage of the detail design with the account of the differential analysis of the destructive factors, structural features, intensity and operation modes of ventilation plants. The proposed methodology for main mine fans residual life determination is applied in expert organizations and Guidances on the determination of residual life of main mine fans which operate under the excess of the standard service life. The methodology may also be applied by project organizations to determine the design service life for the constructed main ventilation installations.

DEVELOPMENT OF AERODYNAMIC DIAGRAMS OF HIGH-LOADED REVERSE AXIAL FANS

Present-day achievements in the field of strength calculation and structural optimization allow creating main mine fans with higher tip speed than in currently used machines. The paper considers the features of calculating the aerodynamic diagrams of mine reverse axial fans with a tip speed over 200 m/s. It is shown that at such speed it is possible to obtain high-flow fans with significantly smaller dimensions than their existing counterparts. Aerodynamic diagrams with high reverse characteristics (flow rate of more than 0.7 from the direct mode for the network of the same aerodynamic characteristics as in direct mode) are developed. The aerodynamic characteristics of the developed diagrams are calculated in the ANSYS software package. It is shown that an increase in the tip speed contributes to an increase in reverse properties of fans compared to less high-speed machines designed for the same total pressure. The limiting values of axial velocity coefficient and pressure coefficient are determined, at which it is possible to obtain a fan without an inlet guide vane, with a monotonic dependence of total pressure on flow rate.

An IGBT short-circuit protection method using variable VCE detection threshold

When mine fan is driven by power inverter, the high-power inverter maybe used to drive low-power motors, so the short-circuit protection threshold of the IGBT needs to be adjusted online. Firstly, the principle of DESAT function of IGBT driver chip is analyzed, then the detection threshold adjustment circuit is designed by using precision voltage reference and voltage comparator, and the method of real-time threshold adjustment by PWM wave with different duty ratio is designed. Experiments show that the IGBT overcurrent detection circuit can respond and act quickly and accurately, so that the IGBT can be protected in time and effectively under different overcurrent conditions.

Stress–strain behavior of discontinuous blades for axial mine fans

The study is aimed at designing of blades such that preserve strength at the tip sped not higher than 140 m/s. Because of high rotary speeds, cast blades lack the wanted strength. Thus, it is necessary to design light-weight blades to increase rotary velocity fans. Using the finite element method in ANSYS, strength calculations are performed for blades of varied cellular structures; the stress and strain patterns versus rotor speed are obtained. The cellular structure blades made of aluminium alloy AK7 allows 1.8 times increase in the rotor speed and delivery of an axial fan series VOD.