Modelling micro-scale coalescence and transportprocesses in liquid aerosol filtration

This work has examined the physico-chemical properties of coalescing filters on a micro-scale, considering them as either a capillary system or a fibre-droplet system. This work has developed a validated theoretical model for droplet-fibe forces in both phillic and phobic systems and a computational fluid dynamics solver for droplet-fibre systems. This work will significantly improve the design and optimisation of coalescing filter systems

Development and Validation of a Computational Fluid Dynamics (CFD) Solver for Droplet-Fibre Systems

Droplet-fibre interactions are found in many natural and anthropogenic systems. A common industrial example is fibrous filtration - used to capture liquid (e.g. oil) mists. The filters used consist mostly of highly porous arrays of randomly layered fibres. Given the random (complex) nature of these filters, the existing models describing their behaviour are mainly empirical in nature and thus only applicable over a narrow range of parameters and operating conditions. Therefore simulation of these filters using computational fluid dynamics offers a viable alternative to the existing models. In this work we will detail the development of a solver that couples the Lagrangian tracking of particles with a volume-of-fluid (VOF) solver. This solver is built on the existing open-source OpenFOAM CFD libraries, which have been modified to allow the physically accurate modelling of small particles. The solver also models the collection of these particles, where there is a transition from the discrete treatment (as in the Lagrangian tracking of the particles) to the volume-of-fluid treatment. The solver allows the simulation of the motion of small liquid droplets, the capture of these droplets by filter fibres, the coalescence of these captured droplets, into films and the subsequent break up of these films into droplet arrays by Plateau-Rayleigh instability. Also simulated is the movement of these coalesced droplets within the filter, leading to the drainage of oil from the filter.A validation of the fundamental physical mechanisms in the filter was performed, by comparing the simulated conformation of liquid droplets and films on the fibre to Plateau-Rayleigh instability theory. The model showed general agreement with both theory and observations. The simulated capture efficiency was also compared to capture efficiencies predicted by the single fibre efficiency (SFE) theory. A good agreement between the two was found

Comparison of breathing models for determining flow and particle deposition in the lungs

Collection and deposition of particles in the upper airway and lungs is of considerable importance – for example, when studying chronic diseases, or when determining the efficacy of aerosol drug delivery. Modelling of particle deposition usually assumes either constant flow (typically at maximum inspiration), or oscillating flow – ignoring any effects of the lung’s motion. This paper presents a preliminary examination of the effects of ignoring mesh motion when modelling the lungs. Initially, an idealised lung model was created, corresponding to generations 0 to 3 of Weibel’s morphology[14]. Simulations were then made using this geometry for steady flow, oscillating flow, and flow developed by expanding the lung. The expansion of the lung was modelled using a mesh motion library developed by the authors. This model allowed the expansion of the lung to be prescribed. Results from the simulations show significant differences between the three modelling options – relating to both the predicted flow field, and particle deposition sites. Robustness of the moving mesh modelling technique is demonstrated on a high-resolution geometry created from CT scans of a Sprague-Dawley rat model lung

Simulating Plateau-Rayleigh instability and liquid reentrainment in a flow field using a VOF method

Plateau-Rayleigh Instability (PRI) is the well known phenomena of the breakup of a liquid column or cylinder. Such a process is integral to the operation of a range of natural and anthropogenic systems, such as gas-liquid and liquid-liquid separators, fuel cells, the accumulation of dewdrops on spider webs, and many more. Volume Of Fluid (VOF) methods, such as available in OpenFOAM, should be able to accurately resolve PRI in such systems. One such system, in which PRI is integral, is the filtration of oil or water aerosol mists using fibrous filters. In many cases, entrainment (or carryover) of liquid from fibers occurs. The mechanisms behind such entrainment are poorly understood. This work will validate the OpenFOAM VOF against classical PRI theory, both with and without a secondary fluid phase flowing through the system (e.g. air). Furthermore, the work will utilise the validated two-phase VOF solver to examine the phenomena of liquid reentrainment from mist filters

The relationship between pressure drop and liquid saturation in oil-mist filters - Predicting filter saturation using a capillary based model

This work details the results of a study into the relationship between pressure drop and liquid saturation in mist (or coalescing) filters. Liquid saturation (clogging) in mist filters is of critical importance as it is directly related to filter efficiency and flow resistance. Experiments were conducted to determine steady-state saturation and pressure drop values in commonly used oleophillic fibrous filter media, using a range of different combinations of face velocity and number of layers of media within the filter element. Several empirical relationships for saturation and pressure drop were derived based on the relationships found. In addition, a capillary-based saturation model has been described and fitted to the experimental data. A good agreement between the model and data was obtained when an empirically fitted term was added. Equations were developed which allow such variables to be determined from known parameters

Respiratory Health Effects of In Vivo Sub-Chronic Diesel and Biodiesel Exhaust Exposure

Biodiesel, which can be made from a variety of natural oils, is currently promoted as a sustainable, healthier replacement for commercial mineral diesel despite little experimental data supporting this. The aim of our research was to investigate the health impacts of exposure to exhaust generated by the combustion of diesel and two different biodiesels. Male BALB/c mice (n = 24 per group) were exposed for 2 h/day for 8 days to diluted exhaust from a diesel engine running on ultra-low sulfur diesel (ULSD) or Tallow or Canola biodiesel, with room air exposures used as control. A variety of respiratory-related end-point measurements were assessed, including lung function, responsiveness to methacholine, airway inflammation and cytokine response, and airway morphometry. Exposure to Tallow biodiesel exhaust resulted in the most significant health impacts compared to Air controls, including increased airway hyperresponsiveness and airway inflammation. In contrast, exposure to Canola biodiesel exhaust resulted in fewer negative health effects. Exposure to ULSD resulted in health impacts between those of the two biodiesels. The health effects of biodiesel exhaust exposure vary depending on the feedstock used to make the fuel

Biodiesel feedstock determines exhaust toxicity in 20% biodiesel: 80% mineral diesel blends

To address climate change concerns, and reduce the carbon footprint caused by fossil fuel use, it is likely that blend ratios of renewable biodiesel with commercial mineral diesel fuel will steadily increase, resulting in biodiesel use becoming more widespread. Exhaust toxicity of unblended biodiesels changes depending on feedstock type, however the effect of feedstock on blended fuels is less well known. The aim of this study was to assess the impact of biodiesel feedstock on exhaust toxicity of 20% blended biodiesel fuels (B20). Primary human airway epithelial cells were exposed to exhaust diluted 1/15 with air from an engine running on conventional ultra-low sulfur diesel (ULSD) or 20% blends of soy, canola, waste cooking oil (WCO), tallow, palm or cottonseed biodiesel in diesel. Physico-chemical exhaust properties were compared between fuels and the post-exposure effect of exhaust on cellular viability and media release was assessed 24 h later. Exhaust properties changed significantly between all fuels with cottonseed B20 being the most different to both ULSD and its respective unblended biodiesel. Exposure to palm B20 resulted in significantly decreased cellular viability (96.3 ± 1.7%; p < 0.01) whereas exposure to soy B20 generated the greatest number of changes in mediator release (including IL-6, IL-8 and TNF-α, p < 0.05) when compared to air exposed controls, with palm B20 and tallow B20 closely following. In contrast, canola B20 and WCO B20 were the least toxic with only mediators G-CSF and TNF-α being significantly increased. Therefore, exposure to palm B20, soy B20 and tallow B20 were found to be the most toxic and exposure to canola B20 and WCO B20 the least. The top three most toxic and the bottom three least toxic B20 fuels are consistent with their unblended counterparts, suggesting that feedstock type greatly impacts exhaust toxicity, even when biodiesel only comprises 20% of the fuel

Multidifferential study of identified charged hadron distributions in ZZ-tagged jets in proton-proton collisions at s=\sqrt{s}=13 TeV

Jet fragmentation functions are measured for the first time in proton-proton collisions for charged pions, kaons, and protons within jets recoiling against a $Z$ boson. The charged-hadron distributions are studied longitudinally and transversely to the jet direction for jets with transverse momentum 20 $< p_{\textrm{T}} < 100$ GeV and in the pseudorapidity range $2.5 < \eta < 4$. The data sample was collected with the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 1.64 fb$^{-1}$. Triple differential distributions as a function of the hadron longitudinal momentum fraction, hadron transverse momentum, and jet transverse momentum are also measured for the first time. This helps constrain transverse-momentum-dependent fragmentation functions. Differences in the shapes and magnitudes of the measured distributions for the different hadron species provide insights into the hadronization process for jets predominantly initiated by light quarks.Comment: All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-013.html (LHCb public pages