A novel, biomimetically inspired, flash evaporation liquid atomization system

• Main Author: Booth, Alexander John
• Published: University of Leeds 2012
• Subjects: 660
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.713482

The increasing demands placed on conventional methods of liquid atomization, in terms of spray quality, now mean that there is a need for a new, disruptive, liquid atomization technology which can rapidly improve spray performance to meet the growing sophistication required of modern liquid spray systems. This thesis details an investigation into the mode of action of a liquid atomization system (pMISTe) which shows promise to be able to provide this disruptive new spray technology. Influenced by the defence mechanism of the bombardier beetle, this atomization method produces a large amount of volumetric shear in a body of liquid, by inducing a flash evaporation of a proportion of the total liquid mass in an enclosed chamber. The flash evaporation is created firstly by heating the liquid far above its saturation temperature at an ambient external pressure - in a chamber cavity sealed by an electronically controlled ejection valve. This valve is released very rapidly, causing the liquid in the chamber to suddenly `see' the ambient external pressure. It is this sudden exposure of a superheated liquid to the low external ambient pressure that drives the flash evaporation and the atomisation. The atomization system was investigated using a staged experimental method, including a mixture of Taguchi Design of Experiment (DoE) and full factorial techniques. From these investigations the main characteristics of the mode of action of the system were identified. These were that, in general, increases in chamber liquid temperature caused decreasing average droplet size, and that increases in refill flow rate caused increasing droplet size; due to the primary flash evaporation mechanism. In addition more complex secondary behaviours, attributed to the fluid dynamic properties of the system, were discovered. The performance of the system is also discussed with reference to its suitability for a range of spray applications