Numerical research on airflow-dust migration behavior and optimal forced air duct installation position in a subway tunnel during drilling operation

Bibliometric analysis and review of mine ventilation literature published between 2010 and 2023

To provide scholars with a quick understanding of the current status, research hotspots, and future trends in the field of mine ventilation, this paper conducted a visualized bibliometric analysis and a comprehensive review of mine ventilation-related literature from 2010 to 2023 using CiteSpace. A thorough analysis of the publication time, co-authorship, co-citation, keywords, and research topics of the literature was carried out. Based on this, through systematic literature reading and summarization, research topics in the field of mine ventilation were organized, analyzed, and classified. The results indicate that mine ventilation research from 2010 to 2023 went through three stages: stable development, slow growth, and rapid ascent. Nie Wen and China Univ Min & Technol were the most prolific authors and institutions in the field of mine ventilation. China had the highest number of publications during 2010-2023, while Canada and Poland exhibited the highest centrality, signifying their key roles in the mine ventilation domain. Deep mine ventilation and intelligent mine ventilation emerged as research hotspots and mainstream trends in the future. The analysis of multiple hazard coupling studies represents a research direction that mine ventilation needs to develop. Numerical simulation techniques should not be limited to static analysis, as dynamic simulation is a focal area of interest.

Parametric modeling study for blown-dust secondary pollution and optimal ventilation velocity during tunnel construction

Tunnel construction often relies on drilling and blasting. High dust pollution is one of the primary problems of drilling and blasting construction. The level of secondary blown dust pollution caused by ventilation matches that of dust pollution caused by drilling construction. In this study, a critical flow model and blown dust rate model for deposited dust were established via force analysis, which was validated against the test data. The research results showed that the characteristic airflow velocity for blowing dust particles with a 100 μm diameter reached approximately 0.42 m/s for tunnel diameter is 10 m, and the ventilation Re values under smooth and rough conditions were 2.3 × 105 and 1.4 × 105, respectively. Furthermore, when ventilation Re reached 4 × 105, the blown dust pollution rate caused by ventilation under smooth conditions was approximately 1.8 × 10-2 kg/s. If dust particle size is more or less the critical dust particle size, the characteristic airflow velocity was increased. Moreover, the optimal velocity at which the deposited dust does not flow or move during tunnel construction was related to the tunnel size and roughness. For the smooth tunnel with a diameter of 10 m, the optimal ventilation velocity was 3.5 m/s. When the tunnel roughness was increased from 0.005 to 0.5 m, the optimal ventilation velocity decreased from 3.3 to 1.6 m/s. The deposited dust critical flow model and blown dust pollution rate model established in this study provide a sound theoretical basis for selecting the optimal velocity of tunnel ventilation and recognizing the risks of secondary blown dust pollution due to ventilation.

Diffusion Characteristics of Airflow and CO in the Dead-End Tunnel with Different Ventilation Parameters after Tunneling Blasting

After tunnel blasting, a large amount of CO will be produced and accumulated in the dead-end tunnel. If the ventilation discharge is not proper and the entry time into the dead-end tunnel is not appropriate, then it can cause workers to suffer from poisoning, hypoxia, and suffocation. Therefore, to understand the airflow and diffusion characteristics of CO in the dead-end tunnel after excavation and improve the working environment quality of the heading excavation tunnel, this paper uses numerical simulation and on-site verification to study the influence of different ventilation parameters on the airflow and CO diffusion characteristics in the dead-end tunnel after excavation and blasting. The research results show that the higher the air velocity of the duct, the smaller the distance between the duct and the working face, and the higher the hanging height of the duct, the easier it is for CO to be discharged from the dead-end tunnel. The larger the distance between the duct and the side wall, the more vortices there are in the dead-end tunnel and the more difficult it is to discharge CO from the tunnel. This study provides theoretical guidance for the research of the migration law of CO after tunnel blasting and has important value for ensuring a safe working environment and clean production in tunnel excavation.

The evaluation analysis on the airborne dust regional pollution of the anchor drilling operation in the tunnel

The anchor drilling operations generate massive airborne dust particles in the tunnel heading face that raises the pneumoconiosis morbidity and explosion risk. In this paper, a full-scale tunnel physical model is constructed to study the effect of the wind velocity and drilling site position on the airborne dust regional pollution scope based on the actual anchor drilling craft. The research indicates that the four extensive vortex areas keep the dust suspension at 14 m from the heading face and make the deposition dust particle refloat. The average respirable dust rate reaches the maximum value at section 5 m and presents a gradual decline as the dust particle migrates along the outlet direction. Raising the wind velocity contributes to alleviating the airborne dust pollution in the anchor drilling operation. As the wind velocity increases from 3 to 24 m/s, the high dust concentration area and number higher than 200 mg/m³ pose overall decrease trends, and the average dust concentration displays a linear decrease until 26.14-58.65 mg/m³ around the anchor worker head. Moving the drilling site positions closer to the exhaust air duct aggravates the airborne dust pollution in the front breathing zone. As the anchor drilling operation switches from the return air side to the supply air side, the dust concentration area ascends by 59.4-84.4% in the personnel respiratory space.

Dust Control Technology in Dry Directional Drilling in Soft and Broken Coal Seams

High rate of dust generation and serious dust diffusion in dry directional drilling in soft and broken coal seams (SBCS) have long been critical problems in the mining process. To solve these problems, in this study, a dust hood was designed and applied to realize non-contact dust control in drilling holes. The optimal performance of the dust hood was achieved when different technical parameters, including the gap width between the dust hood and the drill pipe, the air-slot width of the sealing device, the slag discharge pressure, and the air curtain pressure were controlled at 2 mm, 0.2 mm, 0.3 MPa, and 0.5 MPa, respectively. As a result, the dust concentration was reduced from 540 mg/m³ to 15 mg/m³, with dust control efficiency reaching 97.2%. The in situ test results confirmed good dust control effects, as the dust control efficiency reached 98.3% after using the dust hood.

Optimization of Air Cooling System Using Adjoint Solver Technique

Air cooling systems are currently the most popular and least expensive solutions to maintain a safe temperature in electronic devices. Heat sinks have been widely used in this area, allowing for an increase in the effective heat transfer surface area. The main objective of this study was to optimise the shape of the heat sink geometric model using the Adjoint Solver technique. The optimised shape in the context of minimal temperature value behind the heat sink is proposed. The effect of radiation and trapezoidal fin shape on the maximum temperature in the cooling system is also investigated. Simulation studies were performed in Ansys Fluent software using the Reynolds—averaged Navier–Stokes technique. As a result of the simulation, it turned out that not taking into account the radiation leads to an overestimation of temperatures in the system—even by 14 ∘C. It was found that as the angle and height of the fins increases, the temperature value behind the heat sink decreases and the heat source temperature increases. The best design in the context of minimal temperature value behind the heat sink from all analysed cases is obtained for heat sink with deformed fins according to iteration 14. The temperature reduction behind the heat sink by as much as 25 ∘C, with minor changes in heat source temperature, has been achieved.