Mason-Smith Nicholas, Duke Daniel J, Kastengren Alan L, Traini Daniela, Young Paul M, Chen Yang, Lewis David A, Edgington-Mitchell Daniel, Honnery Damon
Laboratory for Turbulence Research in Aerospace and Combustion, Department of Mechanical and Aerospace Engineering, Monash University, Clayton, Australia.
Energy Systems Division, Argonne National Laboratory, Lemont, Illinois, USA.
Pharm Res. 2017 Apr;34(4):718-729. doi: 10.1007/s11095-017-2098-2. Epub 2017 Jan 17.
Sprays from pressurised metered-dose inhalers are produced by a transient discharge of a multiphase mixture. Small length and short time scales have made the investigation of the governing processes difficult. Consequently, a deep understanding of the physical processes that govern atomisation and drug particle formation has been elusive.
X-ray phase contrast imaging and quantitative radiography were used to reveal the internal flow structure and measure the time-variant nozzle exit mass density of 50 µL metered sprays of HFA134a, with and without ethanol cosolvent. Internal flow patterns were imaged at a magnification of 194 pixels/mm and 7759 frames per second with 150 ps temporal resolution. Spray projected mass was measured with temporal resolution of 1 ms and spatial resolution 6 µm × 5 µm.
The flow upstream of the nozzle comprised large volumes of vapour at all times throughout the injection. The inclusion of ethanol prevented bubble coalescence, altering the internal flow structure and discharge. Radiography measurements confirmed that the nozzle exit area is dominantly occupied by vapour, with a peak liquid volume fraction of 13%.
Vapour generation in pMDIs occurs upstream of the sump, and the dominant volume component in the nozzle exit orifice is vapour at all times in the injection. The flow in ethanol-containing pMDIs has a bubbly structure resulting in a comparatively stable discharge, whereas the binary structure of propellant-only flows results in unsteady discharge and the production of unrespirable liquid masses.
压力定量吸入器产生的喷雾是由多相混合物的瞬态排放形成的。小长度和短时间尺度使得对控制过程的研究变得困难。因此，对控制雾化和药物颗粒形成的物理过程的深入理解一直难以实现。
使用X射线相衬成像和定量射线照相术来揭示内部流动结构，并测量含和不含乙醇共溶剂的50 μL HFA134a定量喷雾的随时间变化的喷嘴出口质量密度。以194像素/毫米的放大倍数和每秒7759帧的速度对内部流动模式进行成像，时间分辨率为150皮秒。以1毫秒的时间分辨率和6微米×5微米的空间分辨率测量喷雾投影质量。
在整个喷射过程中，喷嘴上游的流动始终包含大量蒸汽。加入乙醇可防止气泡合并，改变内部流动结构和排放。射线照相测量证实，喷嘴出口区域主要被蒸汽占据，液体体积分数峰值为13%。
压力定量吸入器中的蒸汽生成发生在贮液槽上游，并且在喷射过程中喷嘴出口孔中的主要体积成分始终是蒸汽。含乙醇的压力定量吸入器中的流动具有气泡结构，导致排放相对稳定，而仅含推进剂的流动的二元结构导致不稳定排放并产生不可吸入的液团。
