Edward J. Long

Characterisation of the Interaction between Toroidal Vortex Structures and Flame Front Propagation

Experimental laser diagnostic data is presented for flame characterisation during interactions with toroidal vortices generated in the wake of an annular obstacle. A novel twin section combustion chamber has been utilised to allow the controlled formation of stable eddy structures into which a flame front can propagate. High speed laser sheet visualisation was employed to record the flow field and flame front temporal development and high-speed digital particle image velocimetry was used to quantify the velocity field of the unburnt mixture ahead of the flame front. Results provide characterisation of the toroidal vortex/flame front interaction for a range of vortex scales of and recirculation strengths.

High-Speed Laser Image Analysis of Plume Angles for Pressurised Metered Dose Inhalers: The Effect of Nozzle Geometry

The aim of this study is to investigate aerosol plume geometries of pressurised metered dose inhalers (pMDIs) using a high-speed laser image system with different actuator nozzle materials and designs. Actuators made from aluminium, PET and PTFE were manufactured with four different nozzle designs: cone, flat, curved cone and curved flat. Plume angles and spans generated using the designed actuator nozzles with four solution-based pMDI formulations were imaged using Oxford Lasers EnVision system and analysed using EnVision Patternate software. Reduced plume angles for all actuator materials and nozzle designs were observed with pMDI formulations containing drug with high co-solvent concentration (ethanol) due to the reduced vapour pressure. Significantly higher plume angles were observed with the PTFE flat nozzle across all formulations, which could be a result of the nozzle geometry and material’s hydrophobicity. The plume geometry of pMDI aerosols can be influenced by the vapour pressure of the formulation, nozzle geometries and actuator material physiochemical properties.

The Influence of Actuator Materials and Nozzle Designs on Electrostatic Charge of Pressurised Metered Dose Inhaler (pMDI) Formulations

ABSTRACTPurposeTo investigate the influence of different actuator materials and nozzle designs on the electrostatic charge properties of a series of solution metered dose inhaler (pMDI) aerosols.MethodsActuators were manufactured with flat and cone nozzle designs using five different materials from the triboelectric series (Nylon, Polyethylene terephthalate, Polyethylene–High density, Polypropylene copolymer and Polytetrafluoroethylene). The electrostatic charge profiles of pMDI containing beclomethasone dipropionate (BDP) as model drug in HFA-134a propellant, with different concentrations of ethanol were studied. Electrostatic measurements were taken using a modified electrical low-pressure impactor (ELPI) and the deposited drug mass assayed chemically using HPLC.ResultsThe charge profiles of HFA 134a alone have shown strong electronegativity with all actuator materials and nozzle designs, at an average of –1531.34 pC ± 377.34. The presence of co-solvent ethanol significantly reduced the negative charge magnitude. BDP reduced the suppressing effect of ethanol on the negative charging of the propellant. For all tested formulations, the flat nozzle design showed no significant differences in net charge between different actuator materials, whereas the charge profiles of cone designs followed the triboelectric series.ConclusionThe electrostatic charging profiles from a solution pMDI containing BDP and ethanol can be significantly influenced by the actuator material, nozzle design and formulation components. Ethanol concentration appears to have the most significant impact. Furthermore, BDP interactions with ethanol and HFA have an influence on the electrostatic charge of aerosols. By choosing different combinations of actuator materials and orifice design, the fine particle fractions of formulations can be altered.

Optical diagnostics studies of air flow and powder fluidisation in Nexthaler®. Part II: Use of fluorescent imaging to characterise transient release of fines from a dry powder inhaler

Graphical abstract Scattered and fluorescent intensity image pairs in mouthpiece exit region of Nexthaler® over a period of 15 ms representing the main fines emission (test conditions: Qmax = 60 l.min−1, Trise = 1.2 s). Figure. No Caption available. Abstract The fine particle fraction is a key indicator of therapeutic effectiveness of inhaled pharmaceutical aerosols. This paper presents a fluorescence imaging technique to visualise and characterise the emission of active pharmaceutical ingredient (API) fines in model formulations containing coarse lactose carrier and 1.5–2 &mgr;m diameter fluorescent microspheres (model API fines). A two‐camera arrangement was used to acquire simultaneous images of spatial and temporal distribution of model API fines and fluidised powder formulation near the mouthpiece exit of a DPI. Digital image analysis showed that the model API fines were released along with the bulk of the powder dose. More rapidly accelerating airflows were found to cause earlier release of API fines. The fluorescence imaging technique analyses a substantial fraction of the aerosol plume and was found to provide effective time‐resolved characterisation of the de‐aggregation and release of API fines with consistent results across a wide range of model API concentrations. Future studies should demonstrate the usefulness of the fluorescence imaging technique across different formulations and DPI devices.

LES and Laser Measurements of Dynamic Flame/Vortex Interactions

The dynamic interaction that occurs between a propagating flame front and a rotating vortex structure is one of the key mechanisms within turbulent combustion [1]. As such, it is found within many applications such as industrial combustors and burners, internal combustion engines, and obstacle-induced explosions. The exact manner in which the flame propagates through a turbulent field is strictly dependent on the turbulent structures encountered by the flame. However, the fluid structures generated in practical configurations are highly complex, providing a difficult environment in which to examine interactions between flame propagation and flow field.