Analysis of Diesel Particulate Matter Flow Patterns in Different Ventilation and Operational Conditions of Underground Mines

Diesel-operated vehicles are commonly used by personnel in underground mines. Although these vehicles facilitate travel within the mine, their main disadvantage is that they generate diesel particulate matter (DPM), a known carcinogenic agent. This calls for research to control the spread of DPM in underground mines in order to ensure the safety of mine personnel. In this article, the flow patterns of DPM generated by two types of diesel-operated vehicles are modeled using computational fluid dynamics (CFD) simulations. The simulation results are validated using field experimental measurements. The models show that if the vehicle is stationary, DPM particles are dispersed towards the center of the gallery and occupy the entire cross section of the road way. Vehicle movement induces air currents that may result in the miners being exposed to high DPM concentrations. The results show that if the DPM and the intake air counter-flow (flow in opposite directions), the DPM spread occurs throughout the entire cross-section of the roadway. This research is expected to contribute to the formulation of effective DPM control strategies in underground mines

Investigation of terrain effects on the consequence distance of CO2 released from high-pressure pipelines

As part of Carbon Capture and Storage (CCS) projects, Carbon Dioxide (CO2) is usually transported via pipelines from source to sequestration location. Ensuring the safety of the operation is of great importance, as CO2 is a hazardous substance and an accidental release may have catastrophic consequences. Therefore, a comprehensive understanding of the effects of a CO2 release from CCS facilities is essential to allow the appropriate safety precautions to be taken. The majority of prior studies that address this topic do so by simulating CO2 dispersion over a flat horizontal terrain. However, CO2 pipelines may be deployed near topographically complex locations such as congested industrial or urban areas. The extent to which the complexity of the terrain may affect the area affected by an accidental release has not been explored in detail. In this paper, we present Computational Fluid Dynamics (CFD) models for the prediction of atmospheric dispersion of CO2 over complex terrains, in order to evaluate the ‘consequence distance’ relating to accidental CO2 releases from high-pressure pipelines. The CFD model is validated against the results of a heavy gas dispersion experiment carried out at Thorney Island. Simulations of CO2 dispersion over seven types of complex terrain are carried out, considering ‘full-bore’ rupture of a pipeline carrying a pre-combustion CO2 mixture. The influence of different terrain features on the consequence distance is studied. In addition, the dispersion of a (CO2 + H2S) mixture is simulated to investigate the threshold value of the fraction of Hydrogen Sulphide (H2S) for which the hazardous effects of H2S become significant for a release over complex terrains

Improved dynamic stall prediction of wind turbine airfoils

This paper presents a dynamic stall model to predict the unsteady airloads on wind turbine airfoils. The proposed model is based on the Beddoes-Leishman (B-L) model and modifications are carried out for wind turbine applications. The lift, drag, and pitch moment of the S809 airfoil oscillating in stall-development and deep-stall regimes are predicted. Validation against available experimental data shows overall good agreement

Optimum Auxiliary Fan Location to Control Air Recirculation

This paper presents the optimum auxiliary fan(s) location to control air recirculation in dead-end workings where diesel-powered vehicles operate. Investigations were conducted with various secondary fan locations from the dead-end crosscut with varying the intake air quantities using a 30 m3/s capacity twin 75 kW auxiliary fan and 45 m3/s capacity twin 110 kW auxiliary fan to control air recirculation and DPM. The results showed that if the drive intake airflow rate matches the fan capacity, air recirculation will occur even when the fan is located 10 m away from the crosscut entry. Results also showed that if the intake drive air quantity was greater than or equal to 150% of fan capacity, no recirculation was observed when the twin 75 kW fan location was at least 5 m and the twin 110 kW fan location was at least 10 m away from the dead-end crosscut access

A new insight into ductile fracture of ultrafine-grained Al-Mg alloys

It is well known that when coarse-grained metals undergo severe plastic deformation to be transformed into nano-grained metals, their ductility is reduced. However, there are no ductile fracture criteria developed based on grain refinement. In this paper, we propose a new relationship between ductile fracture and grain refinement during deformation, considering factors besides void nucleation and growth. Ultrafine-grained Al-Mg alloy sheets were fabricated using different rolling techniques at room and cryogenic temperatures. It is proposed for the first time that features of the microstructure near the fracture surface can be used to explain the ductile fracture post necking directly. We found that as grains are refined to a nano size which approaches the theoretical minimum achievable value, the material becomes brittle at the shear band zone. This may explain the tendency for ductile fracture in metals under plastic deformation.The authors gratefully acknowledge the financial support from the Vice-Chancellor’s Fellowship Grant and URC small grant at the University of Wollongong

Microstructure and mechanical properties of large-volume gradient-structure aluminium sheets fabricated by cyclic skin-pass rolling

Materials of a gradient structure have been shown to possess both high strength and high ductility. To date, materials of a gradient structure can only be produced in small quantities. In this paper, we report a novel \u27cyclic skin-pass rolling\u27 (CSPR) technique capable of producing sheets of gradient structure in large quantities. Both experimental and analytical/numerical investigations are reported. In the experiments on aluminium sheets, the outer layer was subjected to 40 passes of CSPR with a reduction ratio of 1% per pass. After CSPR, the sample surface shows an ultrafine-grained microstructure with a mean grain size of 206 nm, while the annealed microstructure is retained in the core of the sample. Compared with cold-rolled aluminium sheets fabricated with the same total reduction ratio, CSPR-processed aluminium sheets have the same yield stress but improved uniform elongation (2.4 times). The scanning electron microscopy was used to study the fracture surface, and The transmission electron microscopy to examine the microstructure near the fracture end, in order to analyse the improvement in ductility. In addition, the finite element method was used to simulate the roll-sample contact pressure and strain distribution as well as residual stress on the sheet surface during CSPR, and to better understand the mechanism leading to improvement of ductility of the sheets by the CSPR technique

A new insight into ductile fracture of ultrafine-grained Al-Mg alloys

It is well known that when coarse-grained metals undergo severe plastic deformation to be transformed into nano-grained metals, their ductility is reduced. However, there are no ductile fracture criteria developed based on grain refinement. In this paper, we propose a new relationship between ductile fracture and grain refinement during deformation, considering factors besides void nucleation and growth. Ultrafine-grained Al-Mg alloy sheets were fabricated using different rolling techniques at room and cryogenic temperatures. It is proposed for the first time that features of the microstructure near the fracture surface can be used to explain the ductile fracture post necking directly. We found that as grains are refined to a nano size which approaches the theoretical minimum achievable value, the material becomes brittle at the shear band zone. This may explain the tendency for ductile fracture in metals under plastic deformation

Shock-assisted pneumatic injection technology

Analytical and experimental investigations exploring a new, potentially useful idea for a type of particle injector are presented. The injector is designed to work on the principles of gas dynamics, and can be used for transporting dry particulate matter to high pressure destinations and processes. The proposed device is expected to overcome many of the limitations (such as limited operating/back pressure, moving parts, clogging, deterioration due to particle agglomeration) of conventionally used particle feeders. The basic idea involves creation of a zone of relatively low pressure in a supersonic gas stream in a duct, and introducing the particulate matter into this zone. The particulate matter is then conveyed by the gas stream to the high pressure destination through a normal shock. The aim, motivation and basic concepts of the project are introduced in Chapter 1. The relevant available literature is also surveyed. Chapter 2 contains an overview of the project. The technique used for the analytical investigation of the flow in the proposed injector is introduced. Chapter 3 contains an analytical investigation of flow in the Injection Tube. Chapter 4 presents an analysis of the primary gas flow, which leads to nozzle design. Flow in the Interaction Region is investigated in Chapter 5. Chapter 6 introduces a \u27Modified-Fanno\u27 model for the pseudo-shock, developed during the course of the analytical investigation of flow in the Compression Region. In Chapter 7, the \u27Modified-Fanno\u27 model is extended to suspension flows. Chapters 8 and 9 contain two-dimensional and three-dimensional PHOENICS simulations of the flow in the injector duct, respectively. Chapter 10 contains an account of design considerations and fabrication details of the experimental facility and a description of the flow visualisation technique. Chapter 11 presents results of the experimental investigation, along with comparisons with theoretical predictions. Chapter 12 presents conclusions and recommendations for further and related work. Among the new ideas explored during this study are the application of Generalised Steady One-Dimensional Flow analysis for designing the nozzle duct, modelling of a pseudo-normal shock in a duct as \u27Modified-Fanno\u27 flow, and a possible extension of the model to multiple shocks in suspensions. study reveals that the proposed injection device is feasible and easily controllable