Search

In this article, a novel multiscale modeling method is proposed for transient computational fluid dynamics (CFD) simulations of the human airways. The developed method is the first attempt to incorporate spatial coupling and temporal coupling into transient human airway simulations, aiming to improve the flexibility and the efficiency of these simulations. In this method, domain decomposition was used to separate the complex airway model into different scaled domains. Each scaled domain could adopt a suitable mesh and timestep, as necessary: the coarse mesh and large timestep were employed in the macro regions to reduce the computational cost, while the fine mesh and small timestep were used in micro regions to maintain the simulation accuracy. The radial point interpolation method was used to couple data between the coarse mesh and the fine mesh. The continuous micro solution–intermittent temporal coupling method was applied to bridge different timesteps. The developed method was benchmarked using a well-studied four-generation symmetric airway model under realistic normal breath conditions. The accuracy and efficiency of the method were verified separately in the inhalation phase and the exhalation phase. Similar airflow behavior to previous studies was observed from the multiscale airway model. The developed multiscale method has the potential to improve the flexibility and efficiency of transient human airway simulations without sacrificing accuracy.

The objective of this study was to examine the hydrothermal liquefaction of sugarcane bagasse using ethanol and black liquor (BL) in a pilot scale. Combinations of co-solvents (ethanol/ water, ethanol/BL) were studied at various concentrations and reaction conditions. The maximum oil yield of 61% was achieved with a reaction temperature of 300 °C for 30 min and using pure BL as a solvent, while the highest higher heating value (HHV) was obtained from a 50:50 ethanol-BL mixture. The oils contained alcohols, esters, phenolic compounds, aromatics, and heterocyclics. The O/C and H/C ratios of the oil were comparable with traditional biodiesel and commercial diesel. Although this study showed there are some improvements to be made to improve the chemical composition, the approach has potential for large-scale production of a substitute for fossil-fuel-based diesel.

A profluorescent nitroxide was used to evaluate the oxidative potential of pollution derived from a compression ignition engine fuelled with biodiesel. The reaction products responsible for the observed fluorescence increase when a DMSO solution of nitroxide was exposed to biodiesel exhaust were determined by using HPLC/MS. The main fluorescent species was identified as a methanesulfonamide adduct arising from the reaction of the nitroxide with DMSO-derived sulfoxyl radicals.

Particulate matter (PM) emissions involve a complex mixture of solid and liquid particles suspended in a gas, where it is noted that PM emissions from diesel engines are a major contributor to the ambient air pollution problem. While epidemiological studies have shown a link between increased ambient PM emissions and respiratory morbidity and mortality, studies of this design are not able to identify the PM constituents responsible for driving adverse respiratory health effects. This review explores in detail the physico-chemical properties of diesel PM (DPM) and identifies the constituents of this pollution source that are responsible for the development of respiratory disease. In particular, this review shows that the DPM surface area and adsorbed organic compounds play a significant role in manifesting chemical and cellular processes that if sustained can lead to the development of adverse respiratory health effects. The mechanisms of injury involved included inflammation, innate and acquired immunity, and oxidative stress. Understanding the mechanisms of lung injury from DPM will enhance efforts to protect at-risk individuals from the harmful respiratory effects of air pollutants.